Remove damned ancient DOS line endings from Irrlicht. Hopefully I did not go overboard.

1 files changed, 5023 insertions, 5023 deletions

diff --git a/libraries/irrlicht-1.8/source/Irrlicht/libpng/pngrtran.c b/libraries/irrlicht-1.8/source/Irrlicht/libpng/pngrtran.c
index 26083a0..1079595 100644
--- a/libraries/irrlicht-1.8/source/Irrlicht/libpng/pngrtran.c
+++ b/libraries/irrlicht-1.8/source/Irrlicht/libpng/pngrtran.c
@@ -1,5023 +1,5023 @@
-

-/* pngrtran.c - transforms the data in a row for PNG readers

- *

- * Last changed in libpng 1.5.7 [December 15, 2011]

- * Copyright (c) 1998-2011 Glenn Randers-Pehrson

- * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)

- * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)

- *

- * This code is released under the libpng license.

- * For conditions of distribution and use, see the disclaimer

- * and license in png.h

- *

- * This file contains functions optionally called by an application

- * in order to tell libpng how to handle data when reading a PNG.

- * Transformations that are used in both reading and writing are

- * in pngtrans.c.

- */

-

-#include "pngpriv.h"

-

-#ifdef PNG_READ_SUPPORTED

-

-/* Set the action on getting a CRC error for an ancillary or critical chunk. */

-void PNGAPI

-png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)

-{

-   png_debug(1, "in png_set_crc_action");

-

-   if (png_ptr == NULL)

-      return;

-

-   /* Tell libpng how we react to CRC errors in critical chunks */

-   switch (crit_action)

-   {

-      case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */

-         break;

-

-      case PNG_CRC_WARN_USE:                               /* Warn/use data */

-         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;

-         png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;

-         break;

-

-      case PNG_CRC_QUIET_USE:                             /* Quiet/use data */

-         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;

-         png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |

-                           PNG_FLAG_CRC_CRITICAL_IGNORE;

-         break;

-

-      case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */

-         png_warning(png_ptr,

-            "Can't discard critical data on CRC error");

-      case PNG_CRC_ERROR_QUIT:                                /* Error/quit */

-

-      case PNG_CRC_DEFAULT:

-      default:

-         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;

-         break;

-   }

-

-   /* Tell libpng how we react to CRC errors in ancillary chunks */

-   switch (ancil_action)

-   {

-      case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */

-         break;

-

-      case PNG_CRC_WARN_USE:                              /* Warn/use data */

-         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;

-         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;

-         break;

-

-      case PNG_CRC_QUIET_USE:                            /* Quiet/use data */

-         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;

-         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |

-                           PNG_FLAG_CRC_ANCILLARY_NOWARN;

-         break;

-

-      case PNG_CRC_ERROR_QUIT:                               /* Error/quit */

-         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;

-         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;

-         break;

-

-      case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */

-

-      case PNG_CRC_DEFAULT:

-      default:

-         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;

-         break;

-   }

-}

-

-#ifdef PNG_READ_BACKGROUND_SUPPORTED

-/* Handle alpha and tRNS via a background color */

-void PNGFAPI

-png_set_background_fixed(png_structp png_ptr,

-    png_const_color_16p background_color, int background_gamma_code,

-    int need_expand, png_fixed_point background_gamma)

-{

-   png_debug(1, "in png_set_background_fixed");

-

-   if (png_ptr == NULL)

-      return;

-

-   if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)

-   {

-      png_warning(png_ptr, "Application must supply a known background gamma");

-      return;

-   }

-

-   png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;

-   png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-   png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-

-   png_memcpy(&(png_ptr->background), background_color,

-      png_sizeof(png_color_16));

-   png_ptr->background_gamma = background_gamma;

-   png_ptr->background_gamma_type = (png_byte)(background_gamma_code);

-   if (need_expand)

-      png_ptr->transformations |= PNG_BACKGROUND_EXPAND;

-   else

-      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;

-}

-

-#  ifdef PNG_FLOATING_POINT_SUPPORTED

-void PNGAPI

-png_set_background(png_structp png_ptr,

-    png_const_color_16p background_color, int background_gamma_code,

-    int need_expand, double background_gamma)

-{

-   png_set_background_fixed(png_ptr, background_color, background_gamma_code,

-      need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));

-}

-#  endif  /* FLOATING_POINT */

-#endif /* READ_BACKGROUND */

-

-/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the

- * one that pngrtran does first (scale) happens.  This is necessary to allow the

- * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.

- */

-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED

-void PNGAPI

-png_set_scale_16(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_scale_16");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= PNG_SCALE_16_TO_8;

-}

-#endif

-

-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED

-/* Chop 16-bit depth files to 8-bit depth */

-void PNGAPI

-png_set_strip_16(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_strip_16");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= PNG_16_TO_8;

-}

-#endif

-

-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

-void PNGAPI

-png_set_strip_alpha(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_strip_alpha");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= PNG_STRIP_ALPHA;

-}

-#endif

-

-#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)

-static png_fixed_point

-translate_gamma_flags(png_structp png_ptr, png_fixed_point output_gamma,

-   int is_screen)

-{

-   /* Check for flag values.  The main reason for having the old Mac value as a

-    * flag is that it is pretty near impossible to work out what the correct

-    * value is from Apple documentation - a working Mac system is needed to

-    * discover the value!

-    */

-   if (output_gamma == PNG_DEFAULT_sRGB ||

-      output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)

-   {

-      /* If there is no sRGB support this just sets the gamma to the standard

-       * sRGB value.  (This is a side effect of using this function!)

-       */

-#     ifdef PNG_READ_sRGB_SUPPORTED

-         png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;

-#     endif

-      if (is_screen)

-         output_gamma = PNG_GAMMA_sRGB;

-      else

-         output_gamma = PNG_GAMMA_sRGB_INVERSE;

-   }

-

-   else if (output_gamma == PNG_GAMMA_MAC_18 ||

-      output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)

-   {

-      if (is_screen)

-         output_gamma = PNG_GAMMA_MAC_OLD;

-      else

-         output_gamma = PNG_GAMMA_MAC_INVERSE;

-   }

-

-   return output_gamma;

-}

-

-#  ifdef PNG_FLOATING_POINT_SUPPORTED

-static png_fixed_point

-convert_gamma_value(png_structp png_ptr, double output_gamma)

-{

-   /* The following silently ignores cases where fixed point (times 100,000)

-    * gamma values are passed to the floating point API.  This is safe and it

-    * means the fixed point constants work just fine with the floating point

-    * API.  The alternative would just lead to undetected errors and spurious

-    * bug reports.  Negative values fail inside the _fixed API unless they

-    * correspond to the flag values.

-    */

-   if (output_gamma > 0 && output_gamma < 128)

-      output_gamma *= PNG_FP_1;

-

-   /* This preserves -1 and -2 exactly: */

-   output_gamma = floor(output_gamma + .5);

-

-   if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)

-      png_fixed_error(png_ptr, "gamma value");

-

-   return (png_fixed_point)output_gamma;

-}

-#  endif

-#endif /* READ_ALPHA_MODE || READ_GAMMA */

-

-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED

-void PNGFAPI

-png_set_alpha_mode_fixed(png_structp png_ptr, int mode,

-   png_fixed_point output_gamma)

-{

-   int compose = 0;

-   png_fixed_point file_gamma;

-

-   png_debug(1, "in png_set_alpha_mode");

-

-   if (png_ptr == NULL)

-      return;

-

-   output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);

-

-   /* Validate the value to ensure it is in a reasonable range. The value

-    * is expected to be 1 or greater, but this range test allows for some

-    * viewing correction values.  The intent is to weed out users of this API

-    * who use the inverse of the gamma value accidentally!  Since some of these

-    * values are reasonable this may have to be changed.

-    */

-   if (output_gamma < 70000 || output_gamma > 300000)

-      png_error(png_ptr, "output gamma out of expected range");

-

-   /* The default file gamma is the inverse of the output gamma; the output

-    * gamma may be changed below so get the file value first:

-    */

-   file_gamma = png_reciprocal(output_gamma);

-

-   /* There are really 8 possibilities here, composed of any combination

-    * of:

-    *

-    *    premultiply the color channels

-    *    do not encode non-opaque pixels

-    *    encode the alpha as well as the color channels

-    *

-    * The differences disappear if the input/output ('screen') gamma is 1.0,

-    * because then the encoding is a no-op and there is only the choice of

-    * premultiplying the color channels or not.

-    *

-    * png_set_alpha_mode and png_set_background interact because both use

-    * png_compose to do the work.  Calling both is only useful when

-    * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along

-    * with a default gamma value.  Otherwise PNG_COMPOSE must not be set.

-    */

-   switch (mode)

-   {

-      case PNG_ALPHA_PNG:        /* default: png standard */

-         /* No compose, but it may be set by png_set_background! */

-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-         break;

-

-      case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */

-         compose = 1;

-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-         /* The output is linear: */

-         output_gamma = PNG_FP_1;

-         break;

-

-      case PNG_ALPHA_OPTIMIZED:  /* associated, non-opaque pixels linear */

-         compose = 1;

-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-         png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;

-         /* output_gamma records the encoding of opaque pixels! */

-         break;

-

-      case PNG_ALPHA_BROKEN:     /* associated, non-linear, alpha encoded */

-         compose = 1;

-         png_ptr->transformations |= PNG_ENCODE_ALPHA;

-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-         break;

-

-      default:

-         png_error(png_ptr, "invalid alpha mode");

-   }

-

-   /* Only set the default gamma if the file gamma has not been set (this has

-    * the side effect that the gamma in a second call to png_set_alpha_mode will

-    * be ignored.)

-    */

-   if (png_ptr->gamma == 0)

-      png_ptr->gamma = file_gamma;

-

-   /* But always set the output gamma: */

-   png_ptr->screen_gamma = output_gamma;

-

-   /* Finally, if pre-multiplying, set the background fields to achieve the

-    * desired result.

-    */

-   if (compose)

-   {

-      /* And obtain alpha pre-multiplication by composing on black: */

-      png_memset(&png_ptr->background, 0, sizeof png_ptr->background);

-      png_ptr->background_gamma = png_ptr->gamma; /* just in case */

-      png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;

-      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;

-

-      if (png_ptr->transformations & PNG_COMPOSE)

-         png_error(png_ptr,

-            "conflicting calls to set alpha mode and background");

-

-      png_ptr->transformations |= PNG_COMPOSE;

-   }

-

-   /* New API, make sure apps call the correct initializers: */

-   png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;

-}

-

-#  ifdef PNG_FLOATING_POINT_SUPPORTED

-void PNGAPI

-png_set_alpha_mode(png_structp png_ptr, int mode, double output_gamma)

-{

-   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,

-      output_gamma));

-}

-#  endif

-#endif

-

-#ifdef PNG_READ_QUANTIZE_SUPPORTED

-/* Dither file to 8-bit.  Supply a palette, the current number

- * of elements in the palette, the maximum number of elements

- * allowed, and a histogram if possible.  If the current number

- * of colors is greater then the maximum number, the palette will be

- * modified to fit in the maximum number.  "full_quantize" indicates

- * whether we need a quantizing cube set up for RGB images, or if we

- * simply are reducing the number of colors in a paletted image.

- */

-

-typedef struct png_dsort_struct

-{

-   struct png_dsort_struct FAR * next;

-   png_byte left;

-   png_byte right;

-} png_dsort;

-typedef png_dsort FAR *       png_dsortp;

-typedef png_dsort FAR * FAR * png_dsortpp;

-

-void PNGAPI

-png_set_quantize(png_structp png_ptr, png_colorp palette,

-    int num_palette, int maximum_colors, png_const_uint_16p histogram,

-    int full_quantize)

-{

-   png_debug(1, "in png_set_quantize");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= PNG_QUANTIZE;

-

-   if (!full_quantize)

-   {

-      int i;

-

-      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,

-          (png_uint_32)(num_palette * png_sizeof(png_byte)));

-      for (i = 0; i < num_palette; i++)

-         png_ptr->quantize_index[i] = (png_byte)i;

-   }

-

-   if (num_palette > maximum_colors)

-   {

-      if (histogram != NULL)

-      {

-         /* This is easy enough, just throw out the least used colors.

-          * Perhaps not the best solution, but good enough.

-          */

-

-         int i;

-

-         /* Initialize an array to sort colors */

-         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,

-             (png_uint_32)(num_palette * png_sizeof(png_byte)));

-

-         /* Initialize the quantize_sort array */

-         for (i = 0; i < num_palette; i++)

-            png_ptr->quantize_sort[i] = (png_byte)i;

-

-         /* Find the least used palette entries by starting a

-          * bubble sort, and running it until we have sorted

-          * out enough colors.  Note that we don't care about

-          * sorting all the colors, just finding which are

-          * least used.

-          */

-

-         for (i = num_palette - 1; i >= maximum_colors; i--)

-         {

-            int done; /* To stop early if the list is pre-sorted */

-            int j;

-

-            done = 1;

-            for (j = 0; j < i; j++)

-            {

-               if (histogram[png_ptr->quantize_sort[j]]

-                   < histogram[png_ptr->quantize_sort[j + 1]])

-               {

-                  png_byte t;

-

-                  t = png_ptr->quantize_sort[j];

-                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];

-                  png_ptr->quantize_sort[j + 1] = t;

-                  done = 0;

-               }

-            }

-

-            if (done)

-               break;

-         }

-

-         /* Swap the palette around, and set up a table, if necessary */

-         if (full_quantize)

-         {

-            int j = num_palette;

-

-            /* Put all the useful colors within the max, but don't

-             * move the others.

-             */

-            for (i = 0; i < maximum_colors; i++)

-            {

-               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)

-               {

-                  do

-                     j--;

-                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);

-

-                  palette[i] = palette[j];

-               }

-            }

-         }

-         else

-         {

-            int j = num_palette;

-

-            /* Move all the used colors inside the max limit, and

-             * develop a translation table.

-             */

-            for (i = 0; i < maximum_colors; i++)

-            {

-               /* Only move the colors we need to */

-               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)

-               {

-                  png_color tmp_color;

-

-                  do

-                     j--;

-                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);

-

-                  tmp_color = palette[j];

-                  palette[j] = palette[i];

-                  palette[i] = tmp_color;

-                  /* Indicate where the color went */

-                  png_ptr->quantize_index[j] = (png_byte)i;

-                  png_ptr->quantize_index[i] = (png_byte)j;

-               }

-            }

-

-            /* Find closest color for those colors we are not using */

-            for (i = 0; i < num_palette; i++)

-            {

-               if ((int)png_ptr->quantize_index[i] >= maximum_colors)

-               {

-                  int min_d, k, min_k, d_index;

-

-                  /* Find the closest color to one we threw out */

-                  d_index = png_ptr->quantize_index[i];

-                  min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);

-                  for (k = 1, min_k = 0; k < maximum_colors; k++)

-                  {

-                     int d;

-

-                     d = PNG_COLOR_DIST(palette[d_index], palette[k]);

-

-                     if (d < min_d)

-                     {

-                        min_d = d;

-                        min_k = k;

-                     }

-                  }

-                  /* Point to closest color */

-                  png_ptr->quantize_index[i] = (png_byte)min_k;

-               }

-            }

-         }

-         png_free(png_ptr, png_ptr->quantize_sort);

-         png_ptr->quantize_sort = NULL;

-      }

-      else

-      {

-         /* This is much harder to do simply (and quickly).  Perhaps

-          * we need to go through a median cut routine, but those

-          * don't always behave themselves with only a few colors

-          * as input.  So we will just find the closest two colors,

-          * and throw out one of them (chosen somewhat randomly).

-          * [We don't understand this at all, so if someone wants to

-          *  work on improving it, be our guest - AED, GRP]

-          */

-         int i;

-         int max_d;

-         int num_new_palette;

-         png_dsortp t;

-         png_dsortpp hash;

-

-         t = NULL;

-

-         /* Initialize palette index arrays */

-         png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,

-             (png_uint_32)(num_palette * png_sizeof(png_byte)));

-         png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,

-             (png_uint_32)(num_palette * png_sizeof(png_byte)));

-

-         /* Initialize the sort array */

-         for (i = 0; i < num_palette; i++)

-         {

-            png_ptr->index_to_palette[i] = (png_byte)i;

-            png_ptr->palette_to_index[i] = (png_byte)i;

-         }

-

-         hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *

-             png_sizeof(png_dsortp)));

-

-         num_new_palette = num_palette;

-

-         /* Initial wild guess at how far apart the farthest pixel

-          * pair we will be eliminating will be.  Larger

-          * numbers mean more areas will be allocated, Smaller

-          * numbers run the risk of not saving enough data, and

-          * having to do this all over again.

-          *

-          * I have not done extensive checking on this number.

-          */

-         max_d = 96;

-

-         while (num_new_palette > maximum_colors)

-         {

-            for (i = 0; i < num_new_palette - 1; i++)

-            {

-               int j;

-

-               for (j = i + 1; j < num_new_palette; j++)

-               {

-                  int d;

-

-                  d = PNG_COLOR_DIST(palette[i], palette[j]);

-

-                  if (d <= max_d)

-                  {

-

-                     t = (png_dsortp)png_malloc_warn(png_ptr,

-                         (png_uint_32)(png_sizeof(png_dsort)));

-

-                     if (t == NULL)

-                         break;

-

-                     t->next = hash[d];

-                     t->left = (png_byte)i;

-                     t->right = (png_byte)j;

-                     hash[d] = t;

-                  }

-               }

-               if (t == NULL)

-                  break;

-            }

-

-            if (t != NULL)

-            for (i = 0; i <= max_d; i++)

-            {

-               if (hash[i] != NULL)

-               {

-                  png_dsortp p;

-

-                  for (p = hash[i]; p; p = p->next)

-                  {

-                     if ((int)png_ptr->index_to_palette[p->left]

-                         < num_new_palette &&

-                         (int)png_ptr->index_to_palette[p->right]

-                         < num_new_palette)

-                     {

-                        int j, next_j;

-

-                        if (num_new_palette & 0x01)

-                        {

-                           j = p->left;

-                           next_j = p->right;

-                        }

-                        else

-                        {

-                           j = p->right;

-                           next_j = p->left;

-                        }

-

-                        num_new_palette--;

-                        palette[png_ptr->index_to_palette[j]]

-                            = palette[num_new_palette];

-                        if (!full_quantize)

-                        {

-                           int k;

-

-                           for (k = 0; k < num_palette; k++)

-                           {

-                              if (png_ptr->quantize_index[k] ==

-                                  png_ptr->index_to_palette[j])

-                                 png_ptr->quantize_index[k] =

-                                     png_ptr->index_to_palette[next_j];

-

-                              if ((int)png_ptr->quantize_index[k] ==

-                                  num_new_palette)

-                                 png_ptr->quantize_index[k] =

-                                     png_ptr->index_to_palette[j];

-                           }

-                        }

-

-                        png_ptr->index_to_palette[png_ptr->palette_to_index

-                            [num_new_palette]] = png_ptr->index_to_palette[j];

-

-                        png_ptr->palette_to_index[png_ptr->index_to_palette[j]]

-                            = png_ptr->palette_to_index[num_new_palette];

-

-                        png_ptr->index_to_palette[j] =

-                            (png_byte)num_new_palette;

-

-                        png_ptr->palette_to_index[num_new_palette] =

-                            (png_byte)j;

-                     }

-                     if (num_new_palette <= maximum_colors)

-                        break;

-                  }

-                  if (num_new_palette <= maximum_colors)

-                     break;

-               }

-            }

-

-            for (i = 0; i < 769; i++)

-            {

-               if (hash[i] != NULL)

-               {

-                  png_dsortp p = hash[i];

-                  while (p)

-                  {

-                     t = p->next;

-                     png_free(png_ptr, p);

-                     p = t;

-                  }

-               }

-               hash[i] = 0;

-            }

-            max_d += 96;

-         }

-         png_free(png_ptr, hash);

-         png_free(png_ptr, png_ptr->palette_to_index);

-         png_free(png_ptr, png_ptr->index_to_palette);

-         png_ptr->palette_to_index = NULL;

-         png_ptr->index_to_palette = NULL;

-      }

-      num_palette = maximum_colors;

-   }

-   if (png_ptr->palette == NULL)

-   {

-      png_ptr->palette = palette;

-   }

-   png_ptr->num_palette = (png_uint_16)num_palette;

-

-   if (full_quantize)

-   {

-      int i;

-      png_bytep distance;

-      int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +

-          PNG_QUANTIZE_BLUE_BITS;

-      int num_red = (1 << PNG_QUANTIZE_RED_BITS);

-      int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);

-      int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);

-      png_size_t num_entries = ((png_size_t)1 << total_bits);

-

-      png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,

-          (png_uint_32)(num_entries * png_sizeof(png_byte)));

-

-      distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *

-          png_sizeof(png_byte)));

-

-      png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));

-

-      for (i = 0; i < num_palette; i++)

-      {

-         int ir, ig, ib;

-         int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));

-         int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));

-         int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));

-

-         for (ir = 0; ir < num_red; ir++)

-         {

-            /* int dr = abs(ir - r); */

-            int dr = ((ir > r) ? ir - r : r - ir);

-            int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +

-                PNG_QUANTIZE_GREEN_BITS));

-

-            for (ig = 0; ig < num_green; ig++)

-            {

-               /* int dg = abs(ig - g); */

-               int dg = ((ig > g) ? ig - g : g - ig);

-               int dt = dr + dg;

-               int dm = ((dr > dg) ? dr : dg);

-               int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);

-

-               for (ib = 0; ib < num_blue; ib++)

-               {

-                  int d_index = index_g | ib;

-                  /* int db = abs(ib - b); */

-                  int db = ((ib > b) ? ib - b : b - ib);

-                  int dmax = ((dm > db) ? dm : db);

-                  int d = dmax + dt + db;

-

-                  if (d < (int)distance[d_index])

-                  {

-                     distance[d_index] = (png_byte)d;

-                     png_ptr->palette_lookup[d_index] = (png_byte)i;

-                  }

-               }

-            }

-         }

-      }

-

-      png_free(png_ptr, distance);

-   }

-}

-#endif /* PNG_READ_QUANTIZE_SUPPORTED */

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-void PNGFAPI

-png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,

-   png_fixed_point file_gamma)

-{

-   png_debug(1, "in png_set_gamma_fixed");

-

-   if (png_ptr == NULL)

-      return;

-

-   /* New in libpng-1.5.4 - reserve particular negative values as flags. */

-   scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);

-   file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);

-

-#if PNG_LIBPNG_VER >= 10600

-   /* Checking the gamma values for being >0 was added in 1.5.4 along with the

-    * premultiplied alpha support; this actually hides an undocumented feature

-    * of the previous implementation which allowed gamma processing to be

-    * disabled in background handling.  There is no evidence (so far) that this

-    * was being used; however, png_set_background itself accepted and must still

-    * accept '0' for the gamma value it takes, because it isn't always used.

-    *

-    * Since this is an API change (albeit a very minor one that removes an

-    * undocumented API feature) it will not be made until libpng-1.6.0.

-    */

-   if (file_gamma <= 0)

-      png_error(png_ptr, "invalid file gamma in png_set_gamma");

-

-   if (scrn_gamma <= 0)

-      png_error(png_ptr, "invalid screen gamma in png_set_gamma");

-#endif

-

-   /* Set the gamma values unconditionally - this overrides the value in the PNG

-    * file if a gAMA chunk was present.  png_set_alpha_mode provides a

-    * different, easier, way to default the file gamma.

-    */

-   png_ptr->gamma = file_gamma;

-   png_ptr->screen_gamma = scrn_gamma;

-}

-

-#  ifdef PNG_FLOATING_POINT_SUPPORTED

-void PNGAPI

-png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)

-{

-   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),

-      convert_gamma_value(png_ptr, file_gamma));

-}

-#  endif /* FLOATING_POINT_SUPPORTED */

-#endif /* READ_GAMMA */

-

-#ifdef PNG_READ_EXPAND_SUPPORTED

-/* Expand paletted images to RGB, expand grayscale images of

- * less than 8-bit depth to 8-bit depth, and expand tRNS chunks

- * to alpha channels.

- */

-void PNGAPI

-png_set_expand(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_expand");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);

-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-}

-

-/* GRR 19990627:  the following three functions currently are identical

- *  to png_set_expand().  However, it is entirely reasonable that someone

- *  might wish to expand an indexed image to RGB but *not* expand a single,

- *  fully transparent palette entry to a full alpha channel--perhaps instead

- *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace

- *  the transparent color with a particular RGB value, or drop tRNS entirely.

- *  IOW, a future version of the library may make the transformations flag

- *  a bit more fine-grained, with separate bits for each of these three

- *  functions.

- *

- *  More to the point, these functions make it obvious what libpng will be

- *  doing, whereas "expand" can (and does) mean any number of things.

- *

- *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified

- *  to expand only the sample depth but not to expand the tRNS to alpha

- *  and its name was changed to png_set_expand_gray_1_2_4_to_8().

- */

-

-/* Expand paletted images to RGB. */

-void PNGAPI

-png_set_palette_to_rgb(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_palette_to_rgb");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);

-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-}

-

-/* Expand grayscale images of less than 8-bit depth to 8 bits. */

-void PNGAPI

-png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_expand_gray_1_2_4_to_8");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= PNG_EXPAND;

-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-}

-

-

-

-/* Expand tRNS chunks to alpha channels. */

-void PNGAPI

-png_set_tRNS_to_alpha(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_tRNS_to_alpha");

-

-   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);

-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-}

-#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */

-

-#ifdef PNG_READ_EXPAND_16_SUPPORTED

-/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise

- * it may not work correctly.)

- */

-void PNGAPI

-png_set_expand_16(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_expand_16");

-

-   if (png_ptr == NULL)

-      return;

-

-   png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);

-   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-

-   /* New API, make sure apps call the correct initializers: */

-   png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;

-}

-#endif

-

-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED

-void PNGAPI

-png_set_gray_to_rgb(png_structp png_ptr)

-{

-   png_debug(1, "in png_set_gray_to_rgb");

-

-   if (png_ptr != NULL)

-   {

-      /* Because rgb must be 8 bits or more: */

-      png_set_expand_gray_1_2_4_to_8(png_ptr);

-      png_ptr->transformations |= PNG_GRAY_TO_RGB;

-      png_ptr->flags &= ~PNG_FLAG_ROW_INIT;

-   }

-}

-#endif

-

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-void PNGFAPI

-png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,

-    png_fixed_point red, png_fixed_point green)

-{

-   png_debug(1, "in png_set_rgb_to_gray");

-

-   if (png_ptr == NULL)

-      return;

-

-   switch(error_action)

-   {

-      case PNG_ERROR_ACTION_NONE:

-         png_ptr->transformations |= PNG_RGB_TO_GRAY;

-         break;

-

-      case PNG_ERROR_ACTION_WARN:

-         png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;

-         break;

-

-      case PNG_ERROR_ACTION_ERROR:

-         png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;

-         break;

-

-      default:

-         png_error(png_ptr, "invalid error action to rgb_to_gray");

-         break;

-   }

-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

-#ifdef PNG_READ_EXPAND_SUPPORTED

-      png_ptr->transformations |= PNG_EXPAND;

-#else

-   {

-      png_warning(png_ptr,

-        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");

-

-      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;

-   }

-#endif

-   {

-      if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)

-      {

-         png_uint_16 red_int, green_int;

-

-         /* NOTE: this calculation does not round, but this behavior is retained

-          * for consistency, the inaccuracy is very small.  The code here always

-          * overwrites the coefficients, regardless of whether they have been

-          * defaulted or set already.

-          */

-         red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);

-         green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);

-

-         png_ptr->rgb_to_gray_red_coeff   = red_int;

-         png_ptr->rgb_to_gray_green_coeff = green_int;

-         png_ptr->rgb_to_gray_coefficients_set = 1;

-      }

-

-      else

-      {

-         if (red >= 0 && green >= 0)

-            png_warning(png_ptr,

-               "ignoring out of range rgb_to_gray coefficients");

-

-         /* Use the defaults, from the cHRM chunk if set, else the historical

-          * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See

-          * png_do_rgb_to_gray for more discussion of the values.  In this case

-          * the coefficients are not marked as 'set' and are not overwritten if

-          * something has already provided a default.

-          */

-         if (png_ptr->rgb_to_gray_red_coeff == 0 &&

-            png_ptr->rgb_to_gray_green_coeff == 0)

-         {

-            png_ptr->rgb_to_gray_red_coeff   = 6968;

-            png_ptr->rgb_to_gray_green_coeff = 23434;

-            /* png_ptr->rgb_to_gray_blue_coeff  = 2366; */

-         }

-      }

-   }

-}

-

-#ifdef PNG_FLOATING_POINT_SUPPORTED

-/* Convert a RGB image to a grayscale of the same width.  This allows us,

- * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.

- */

-

-void PNGAPI

-png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,

-   double green)

-{

-   if (png_ptr == NULL)

-      return;

-

-   png_set_rgb_to_gray_fixed(png_ptr, error_action,

-      png_fixed(png_ptr, red, "rgb to gray red coefficient"),

-      png_fixed(png_ptr, green, "rgb to gray green coefficient"));

-}

-#endif /* FLOATING POINT */

-

-#endif

-

-#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \

-    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)

-void PNGAPI

-png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr

-    read_user_transform_fn)

-{

-   png_debug(1, "in png_set_read_user_transform_fn");

-

-   if (png_ptr == NULL)

-      return;

-

-#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED

-   png_ptr->transformations |= PNG_USER_TRANSFORM;

-   png_ptr->read_user_transform_fn = read_user_transform_fn;

-#endif

-}

-#endif

-

-#ifdef PNG_READ_TRANSFORMS_SUPPORTED

-#ifdef PNG_READ_GAMMA_SUPPORTED

-/* In the case of gamma transformations only do transformations on images where

- * the [file] gamma and screen_gamma are not close reciprocals, otherwise it

- * slows things down slightly, and also needlessly introduces small errors.

- */

-static int /* PRIVATE */

-png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)

-{

-   /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma

-    * correction as a difference of the overall transform from 1.0

-    *

-    * We want to compare the threshold with s*f - 1, if we get

-    * overflow here it is because of wacky gamma values so we

-    * turn on processing anyway.

-    */

-   png_fixed_point gtest;

-   return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||

-       png_gamma_significant(gtest);

-}

-#endif

-

-/* Initialize everything needed for the read.  This includes modifying

- * the palette.

- */

-

-/*For the moment 'png_init_palette_transformations' and

- * 'png_init_rgb_transformations' only do some flag canceling optimizations.

- * The intent is that these two routines should have palette or rgb operations

- * extracted from 'png_init_read_transformations'.

- */

-static void /* PRIVATE */

-png_init_palette_transformations(png_structp png_ptr)

-{

-   /* Called to handle the (input) palette case.  In png_do_read_transformations

-    * the first step is to expand the palette if requested, so this code must

-    * take care to only make changes that are invariant with respect to the

-    * palette expansion, or only do them if there is no expansion.

-    *

-    * STRIP_ALPHA has already been handled in the caller (by setting num_trans

-    * to 0.)

-    */

-   int input_has_alpha = 0;

-   int input_has_transparency = 0;

-

-   if (png_ptr->num_trans > 0)

-   {

-      int i;

-

-      /* Ignore if all the entries are opaque (unlikely!) */

-      for (i=0; i<png_ptr->num_trans; ++i)

-         if (png_ptr->trans_alpha[i] == 255)

-            continue;

-         else if (png_ptr->trans_alpha[i] == 0)

-            input_has_transparency = 1;

-         else

-            input_has_alpha = 1;

-   }

-

-   /* If no alpha we can optimize. */

-   if (!input_has_alpha)

-   {

-      /* Any alpha means background and associative alpha processing is

-       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA

-       * and ENCODE_ALPHA are irrelevant.

-       */

-      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-

-      if (!input_has_transparency)

-         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);

-   }

-

-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)

-   /* png_set_background handling - deals with the complexity of whether the

-    * background color is in the file format or the screen format in the case

-    * where an 'expand' will happen.

-    */

-

-   /* The following code cannot be entered in the alpha pre-multiplication case

-    * because PNG_BACKGROUND_EXPAND is cancelled below.

-    */

-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&

-       (png_ptr->transformations & PNG_EXPAND))

-   {

-      {

-         png_ptr->background.red   =

-             png_ptr->palette[png_ptr->background.index].red;

-         png_ptr->background.green =

-             png_ptr->palette[png_ptr->background.index].green;

-         png_ptr->background.blue  =

-             png_ptr->palette[png_ptr->background.index].blue;

-

-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED

-        if (png_ptr->transformations & PNG_INVERT_ALPHA)

-        {

-           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))

-           {

-              /* Invert the alpha channel (in tRNS) unless the pixels are

-               * going to be expanded, in which case leave it for later

-               */

-              int i, istop = png_ptr->num_trans;

-

-              for (i=0; i<istop; i++)

-                 png_ptr->trans_alpha[i] = (png_byte)(255 -

-                    png_ptr->trans_alpha[i]);

-           }

-        }

-#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */

-      }

-   } /* background expand and (therefore) no alpha association. */

-#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */

-}

-

-static void /* PRIVATE */

-png_init_rgb_transformations(png_structp png_ptr)

-{

-   /* Added to libpng-1.5.4: check the color type to determine whether there

-    * is any alpha or transparency in the image and simply cancel the

-    * background and alpha mode stuff if there isn't.

-    */

-   int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;

-   int input_has_transparency = png_ptr->num_trans > 0;

-

-   /* If no alpha we can optimize. */

-   if (!input_has_alpha)

-   {

-      /* Any alpha means background and associative alpha processing is

-       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA

-       * and ENCODE_ALPHA are irrelevant.

-       */

-#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED

-         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-#     endif

-

-      if (!input_has_transparency)

-         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);

-   }

-

-#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)

-   /* png_set_background handling - deals with the complexity of whether the

-    * background color is in the file format or the screen format in the case

-    * where an 'expand' will happen.

-    */

-

-   /* The following code cannot be entered in the alpha pre-multiplication case

-    * because PNG_BACKGROUND_EXPAND is cancelled below.

-    */

-   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&

-       (png_ptr->transformations & PNG_EXPAND) &&

-       !(png_ptr->color_type & PNG_COLOR_MASK_COLOR))

-       /* i.e., GRAY or GRAY_ALPHA */

-   {

-      {

-         /* Expand background and tRNS chunks */

-         int gray = png_ptr->background.gray;

-         int trans_gray = png_ptr->trans_color.gray;

-

-         switch (png_ptr->bit_depth)

-         {

-            case 1:

-               gray *= 0xff;

-               trans_gray *= 0xff;

-               break;

-

-            case 2:

-               gray *= 0x55;

-               trans_gray *= 0x55;

-               break;

-

-            case 4:

-               gray *= 0x11;

-               trans_gray *= 0x11;

-               break;

-

-            default:

-

-            case 8:

-               /* Already 8 bits, fall through */

-

-            case 16:

-               /* Already a full 16 bits */

-               break;

-         }

-

-         png_ptr->background.red = png_ptr->background.green =

-            png_ptr->background.blue = (png_uint_16)gray;

-

-         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))

-         {

-            png_ptr->trans_color.red = png_ptr->trans_color.green =

-               png_ptr->trans_color.blue = (png_uint_16)trans_gray;

-         }

-      }

-   } /* background expand and (therefore) no alpha association. */

-#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */

-}

-

-void /* PRIVATE */

-png_init_read_transformations(png_structp png_ptr)

-{

-   png_debug(1, "in png_init_read_transformations");

-

-   /* This internal function is called from png_read_start_row in pngrutil.c

-    * and it is called before the 'rowbytes' calculation is done, so the code

-    * in here can change or update the transformations flags.

-    *

-    * First do updates that do not depend on the details of the PNG image data

-    * being processed.

-    */

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-   /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds

-    * png_set_alpha_mode and this is another source for a default file gamma so

-    * the test needs to be performed later - here.  In addition prior to 1.5.4

-    * the tests were repeated for the PALETTE color type here - this is no

-    * longer necessary (and doesn't seem to have been necessary before.)

-    */

-   {

-      /* The following temporary indicates if overall gamma correction is

-       * required.

-       */

-      int gamma_correction = 0;

-

-      if (png_ptr->gamma != 0) /* has been set */

-      {

-         if (png_ptr->screen_gamma != 0) /* screen set too */

-            gamma_correction = png_gamma_threshold(png_ptr->gamma,

-               png_ptr->screen_gamma);

-

-         else

-            /* Assume the output matches the input; a long time default behavior

-             * of libpng, although the standard has nothing to say about this.

-             */

-            png_ptr->screen_gamma = png_reciprocal(png_ptr->gamma);

-      }

-

-      else if (png_ptr->screen_gamma != 0)

-         /* The converse - assume the file matches the screen, note that this

-          * perhaps undesireable default can (from 1.5.4) be changed by calling

-          * png_set_alpha_mode (even if the alpha handling mode isn't required

-          * or isn't changed from the default.)

-          */

-         png_ptr->gamma = png_reciprocal(png_ptr->screen_gamma);

-

-      else /* neither are set */

-         /* Just in case the following prevents any processing - file and screen

-          * are both assumed to be linear and there is no way to introduce a

-          * third gamma value other than png_set_background with 'UNIQUE', and,

-          * prior to 1.5.4

-          */

-         png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;

-

-      /* Now turn the gamma transformation on or off as appropriate.  Notice

-       * that PNG_GAMMA just refers to the file->screen correction.  Alpha

-       * composition may independently cause gamma correction because it needs

-       * linear data (e.g. if the file has a gAMA chunk but the screen gamma

-       * hasn't been specified.)  In any case this flag may get turned off in

-       * the code immediately below if the transform can be handled outside the

-       * row loop.

-       */

-      if (gamma_correction)

-         png_ptr->transformations |= PNG_GAMMA;

-

-      else

-         png_ptr->transformations &= ~PNG_GAMMA;

-   }

-#endif

-

-   /* Certain transformations have the effect of preventing other

-    * transformations that happen afterward in png_do_read_transformations,

-    * resolve the interdependencies here.  From the code of

-    * png_do_read_transformations the order is:

-    *

-    *  1) PNG_EXPAND (including PNG_EXPAND_tRNS)

-    *  2) PNG_STRIP_ALPHA (if no compose)

-    *  3) PNG_RGB_TO_GRAY

-    *  4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY

-    *  5) PNG_COMPOSE

-    *  6) PNG_GAMMA

-    *  7) PNG_STRIP_ALPHA (if compose)

-    *  8) PNG_ENCODE_ALPHA

-    *  9) PNG_SCALE_16_TO_8

-    * 10) PNG_16_TO_8

-    * 11) PNG_QUANTIZE (converts to palette)

-    * 12) PNG_EXPAND_16

-    * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY

-    * 14) PNG_INVERT_MONO

-    * 15) PNG_SHIFT

-    * 16) PNG_PACK

-    * 17) PNG_BGR

-    * 18) PNG_PACKSWAP

-    * 19) PNG_FILLER (includes PNG_ADD_ALPHA)

-    * 20) PNG_INVERT_ALPHA

-    * 21) PNG_SWAP_ALPHA

-    * 22) PNG_SWAP_BYTES

-    * 23) PNG_USER_TRANSFORM [must be last]

-    */

-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&

-      !(png_ptr->transformations & PNG_COMPOSE))

-   {

-      /* Stripping the alpha channel happens immediately after the 'expand'

-       * transformations, before all other transformation, so it cancels out

-       * the alpha handling.  It has the side effect negating the effect of

-       * PNG_EXPAND_tRNS too:

-       */

-      png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |

-         PNG_EXPAND_tRNS);

-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-

-      /* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen

-       * so transparency information would remain just so long as it wasn't

-       * expanded.  This produces unexpected API changes if the set of things

-       * that do PNG_EXPAND_tRNS changes (perfectly possible given the

-       * documentation - which says ask for what you want, accept what you

-       * get.)  This makes the behavior consistent from 1.5.4:

-       */

-      png_ptr->num_trans = 0;

-   }

-#endif /* STRIP_ALPHA supported, no COMPOSE */

-

-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED

-   /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA

-    * settings will have no effect.

-    */

-   if (!png_gamma_significant(png_ptr->screen_gamma))

-   {

-      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;

-      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;

-   }

-#endif

-

-#if defined(PNG_READ_EXPAND_SUPPORTED) && \

-   defined(PNG_READ_BACKGROUND_SUPPORTED) && \

-   defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)

-   /* Detect gray background and attempt to enable optimization for

-    * gray --> RGB case.

-    *

-    * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or

-    * RGB_ALPHA (in which case need_expand is superfluous anyway), the

-    * background color might actually be gray yet not be flagged as such.

-    * This is not a problem for the current code, which uses

-    * PNG_BACKGROUND_IS_GRAY only to decide when to do the

-    * png_do_gray_to_rgb() transformation.

-    *

-    * TODO: this code needs to be revised to avoid the complexity and

-    * interdependencies.  The color type of the background should be recorded in

-    * png_set_background, along with the bit depth, then the code has a record

-    * of exactly what color space the background is currently in.

-    */

-   if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)

-   {

-      /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if

-       * the file was grayscale the background value is gray.

-       */

-      if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))

-         png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;

-   }

-

-   else if (png_ptr->transformations & PNG_COMPOSE)

-   {

-      /* PNG_COMPOSE: png_set_background was called with need_expand false,

-       * so the color is in the color space of the output or png_set_alpha_mode

-       * was called and the color is black.  Ignore RGB_TO_GRAY because that

-       * happens before GRAY_TO_RGB.

-       */

-      if (png_ptr->transformations & PNG_GRAY_TO_RGB)

-      {

-         if (png_ptr->background.red == png_ptr->background.green &&

-             png_ptr->background.red == png_ptr->background.blue)

-         {

-            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;

-            png_ptr->background.gray = png_ptr->background.red;

-         }

-      }

-   }

-#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED (etc) */

-

-   /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations

-    * can be performed directly on the palette, and some (such as rgb to gray)

-    * can be optimized inside the palette.  This is particularly true of the

-    * composite (background and alpha) stuff, which can be pretty much all done

-    * in the palette even if the result is expanded to RGB or gray afterward.

-    *

-    * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and

-    * earlier and the palette stuff is actually handled on the first row.  This

-    * leads to the reported bug that the palette returned by png_get_PLTE is not

-    * updated.

-    */

-   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

-      png_init_palette_transformations(png_ptr);

-

-   else

-      png_init_rgb_transformations(png_ptr);

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \

-   defined(PNG_READ_EXPAND_16_SUPPORTED)

-   if ((png_ptr->transformations & PNG_EXPAND_16) &&

-      (png_ptr->transformations & PNG_COMPOSE) &&

-      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&

-      png_ptr->bit_depth != 16)

-   {

-      /* TODO: fix this.  Because the expand_16 operation is after the compose

-       * handling the background color must be 8, not 16, bits deep, but the

-       * application will supply a 16-bit value so reduce it here.

-       *

-       * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at

-       * present, so that case is ok (until do_expand_16 is moved.)

-       *

-       * NOTE: this discards the low 16 bits of the user supplied background

-       * color, but until expand_16 works properly there is no choice!

-       */

-#     define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))

-      CHOP(png_ptr->background.red);

-      CHOP(png_ptr->background.green);

-      CHOP(png_ptr->background.blue);

-      CHOP(png_ptr->background.gray);

-#     undef CHOP

-   }

-#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \

-   (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \

-   defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))

-   if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&

-      (png_ptr->transformations & PNG_COMPOSE) &&

-      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&

-      png_ptr->bit_depth == 16)

-   {

-      /* On the other hand, if a 16-bit file is to be reduced to 8-bits per

-       * component this will also happen after PNG_COMPOSE and so the background

-       * color must be pre-expanded here.

-       *

-       * TODO: fix this too.

-       */

-      png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);

-      png_ptr->background.green =

-         (png_uint_16)(png_ptr->background.green * 257);

-      png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);

-      png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);

-   }

-#endif

-

-   /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the

-    * background support (see the comments in scripts/pnglibconf.dfa), this

-    * allows pre-multiplication of the alpha channel to be implemented as

-    * compositing on black.  This is probably sub-optimal and has been done in

-    * 1.5.4 betas simply to enable external critique and testing (i.e. to

-    * implement the new API quickly, without lots of internal changes.)

-    */

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-#  ifdef PNG_READ_BACKGROUND_SUPPORTED

-      /* Includes ALPHA_MODE */

-      png_ptr->background_1 = png_ptr->background;

-#  endif

-

-   /* This needs to change - in the palette image case a whole set of tables are

-    * built when it would be quicker to just calculate the correct value for

-    * each palette entry directly.  Also, the test is too tricky - why check

-    * PNG_RGB_TO_GRAY if PNG_GAMMA is not set?  The answer seems to be that

-    * PNG_GAMMA is cancelled even if the gamma is known?  The test excludes the

-    * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction

-    * the gamma tables will not be built even if composition is required on a

-    * gamma encoded value.

-    *

-    * In 1.5.4 this is addressed below by an additional check on the individual

-    * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the

-    * tables.

-    */

-   if ((png_ptr->transformations & PNG_GAMMA)

-      || ((png_ptr->transformations & PNG_RGB_TO_GRAY)

-         && (png_gamma_significant(png_ptr->gamma) ||

-            png_gamma_significant(png_ptr->screen_gamma)))

-      || ((png_ptr->transformations & PNG_COMPOSE)

-         && (png_gamma_significant(png_ptr->gamma)

-            || png_gamma_significant(png_ptr->screen_gamma)

-#  ifdef PNG_READ_BACKGROUND_SUPPORTED

-            || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE

-               && png_gamma_significant(png_ptr->background_gamma))

-#  endif

-      )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)

-         && png_gamma_significant(png_ptr->screen_gamma))

-      )

-   {

-      png_build_gamma_table(png_ptr, png_ptr->bit_depth);

-

-#ifdef PNG_READ_BACKGROUND_SUPPORTED

-      if (png_ptr->transformations & PNG_COMPOSE)

-      {

-         /* Issue a warning about this combination: because RGB_TO_GRAY is

-          * optimized to do the gamma transform if present yet do_background has

-          * to do the same thing if both options are set a

-          * double-gamma-correction happens.  This is true in all versions of

-          * libpng to date.

-          */

-         if (png_ptr->transformations & PNG_RGB_TO_GRAY)

-            png_warning(png_ptr,

-               "libpng does not support gamma+background+rgb_to_gray");

-

-         if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

-         {

-            /* We don't get to here unless there is a tRNS chunk with non-opaque

-             * entries - see the checking code at the start of this function.

-             */

-            png_color back, back_1;

-            png_colorp palette = png_ptr->palette;

-            int num_palette = png_ptr->num_palette;

-            int i;

-            if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)

-            {

-

-               back.red = png_ptr->gamma_table[png_ptr->background.red];

-               back.green = png_ptr->gamma_table[png_ptr->background.green];

-               back.blue = png_ptr->gamma_table[png_ptr->background.blue];

-

-               back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];

-               back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];

-               back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];

-            }

-            else

-            {

-               png_fixed_point g, gs;

-

-               switch (png_ptr->background_gamma_type)

-               {

-                  case PNG_BACKGROUND_GAMMA_SCREEN:

-                     g = (png_ptr->screen_gamma);

-                     gs = PNG_FP_1;

-                     break;

-

-                  case PNG_BACKGROUND_GAMMA_FILE:

-                     g = png_reciprocal(png_ptr->gamma);

-                     gs = png_reciprocal2(png_ptr->gamma,

-                        png_ptr->screen_gamma);

-                     break;

-

-                  case PNG_BACKGROUND_GAMMA_UNIQUE:

-                     g = png_reciprocal(png_ptr->background_gamma);

-                     gs = png_reciprocal2(png_ptr->background_gamma,

-                        png_ptr->screen_gamma);

-                     break;

-                  default:

-                     g = PNG_FP_1;    /* back_1 */

-                     gs = PNG_FP_1;   /* back */

-                     break;

-               }

-

-               if (png_gamma_significant(gs))

-               {

-                  back.red = png_gamma_8bit_correct(png_ptr->background.red,

-                      gs);

-                  back.green = png_gamma_8bit_correct(png_ptr->background.green,

-                      gs);

-                  back.blue = png_gamma_8bit_correct(png_ptr->background.blue,

-                      gs);

-               }

-

-               else

-               {

-                  back.red   = (png_byte)png_ptr->background.red;

-                  back.green = (png_byte)png_ptr->background.green;

-                  back.blue  = (png_byte)png_ptr->background.blue;

-               }

-

-               if (png_gamma_significant(g))

-               {

-                  back_1.red = png_gamma_8bit_correct(png_ptr->background.red,

-                     g);

-                  back_1.green = png_gamma_8bit_correct(

-                     png_ptr->background.green, g);

-                  back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,

-                     g);

-               }

-

-               else

-               {

-                  back_1.red   = (png_byte)png_ptr->background.red;

-                  back_1.green = (png_byte)png_ptr->background.green;

-                  back_1.blue  = (png_byte)png_ptr->background.blue;

-               }

-            }

-

-            for (i = 0; i < num_palette; i++)

-            {

-               if (i < (int)png_ptr->num_trans &&

-                   png_ptr->trans_alpha[i] != 0xff)

-               {

-                  if (png_ptr->trans_alpha[i] == 0)

-                  {

-                     palette[i] = back;

-                  }

-                  else /* if (png_ptr->trans_alpha[i] != 0xff) */

-                  {

-                     png_byte v, w;

-

-                     v = png_ptr->gamma_to_1[palette[i].red];

-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);

-                     palette[i].red = png_ptr->gamma_from_1[w];

-

-                     v = png_ptr->gamma_to_1[palette[i].green];

-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);

-                     palette[i].green = png_ptr->gamma_from_1[w];

-

-                     v = png_ptr->gamma_to_1[palette[i].blue];

-                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);

-                     palette[i].blue = png_ptr->gamma_from_1[w];

-                  }

-               }

-               else

-               {

-                  palette[i].red = png_ptr->gamma_table[palette[i].red];

-                  palette[i].green = png_ptr->gamma_table[palette[i].green];

-                  palette[i].blue = png_ptr->gamma_table[palette[i].blue];

-               }

-            }

-

-            /* Prevent the transformations being done again.

-             *

-             * NOTE: this is highly dubious; it removes the transformations in

-             * place.  This seems inconsistent with the general treatment of the

-             * transformations elsewhere.

-             */

-            png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);

-         } /* color_type == PNG_COLOR_TYPE_PALETTE */

-

-         /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */

-         else /* color_type != PNG_COLOR_TYPE_PALETTE */

-         {

-            int gs_sig, g_sig;

-            png_fixed_point g = PNG_FP_1;  /* Correction to linear */

-            png_fixed_point gs = PNG_FP_1; /* Correction to screen */

-

-            switch (png_ptr->background_gamma_type)

-            {

-               case PNG_BACKGROUND_GAMMA_SCREEN:

-                  g = png_ptr->screen_gamma;

-                  /* gs = PNG_FP_1; */

-                  break;

-

-               case PNG_BACKGROUND_GAMMA_FILE:

-                  g = png_reciprocal(png_ptr->gamma);

-                  gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_gamma);

-                  break;

-

-               case PNG_BACKGROUND_GAMMA_UNIQUE:

-                  g = png_reciprocal(png_ptr->background_gamma);

-                  gs = png_reciprocal2(png_ptr->background_gamma,

-                      png_ptr->screen_gamma);

-                  break;

-

-               default:

-                  png_error(png_ptr, "invalid background gamma type");

-            }

-

-            g_sig = png_gamma_significant(g);

-            gs_sig = png_gamma_significant(gs);

-

-            if (g_sig)

-               png_ptr->background_1.gray = png_gamma_correct(png_ptr,

-                   png_ptr->background.gray, g);

-

-            if (gs_sig)

-               png_ptr->background.gray = png_gamma_correct(png_ptr,

-                   png_ptr->background.gray, gs);

-

-            if ((png_ptr->background.red != png_ptr->background.green) ||

-                (png_ptr->background.red != png_ptr->background.blue) ||

-                (png_ptr->background.red != png_ptr->background.gray))

-            {

-               /* RGB or RGBA with color background */

-               if (g_sig)

-               {

-                  png_ptr->background_1.red = png_gamma_correct(png_ptr,

-                      png_ptr->background.red, g);

-

-                  png_ptr->background_1.green = png_gamma_correct(png_ptr,

-                      png_ptr->background.green, g);

-

-                  png_ptr->background_1.blue = png_gamma_correct(png_ptr,

-                      png_ptr->background.blue, g);

-               }

-

-               if (gs_sig)

-               {

-                  png_ptr->background.red = png_gamma_correct(png_ptr,

-                      png_ptr->background.red, gs);

-

-                  png_ptr->background.green = png_gamma_correct(png_ptr,

-                      png_ptr->background.green, gs);

-

-                  png_ptr->background.blue = png_gamma_correct(png_ptr,

-                      png_ptr->background.blue, gs);

-               }

-            }

-

-            else

-            {

-               /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */

-               png_ptr->background_1.red = png_ptr->background_1.green

-                   = png_ptr->background_1.blue = png_ptr->background_1.gray;

-

-               png_ptr->background.red = png_ptr->background.green

-                   = png_ptr->background.blue = png_ptr->background.gray;

-            }

-

-            /* The background is now in screen gamma: */

-            png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;

-         } /* color_type != PNG_COLOR_TYPE_PALETTE */

-      }/* png_ptr->transformations & PNG_BACKGROUND */

-

-      else

-      /* Transformation does not include PNG_BACKGROUND */

-#endif /* PNG_READ_BACKGROUND_SUPPORTED */

-      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-         /* RGB_TO_GRAY needs to have non-gamma-corrected values! */

-         && ((png_ptr->transformations & PNG_EXPAND) == 0 ||

-         (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)

-#endif

-         )

-      {

-         png_colorp palette = png_ptr->palette;

-         int num_palette = png_ptr->num_palette;

-         int i;

-

-         /*NOTE: there are other transformations that should probably be in here

-          * too.

-          */

-         for (i = 0; i < num_palette; i++)

-         {

-            palette[i].red = png_ptr->gamma_table[palette[i].red];

-            palette[i].green = png_ptr->gamma_table[palette[i].green];

-            palette[i].blue = png_ptr->gamma_table[palette[i].blue];

-         }

-

-         /* Done the gamma correction. */

-         png_ptr->transformations &= ~PNG_GAMMA;

-      } /* color_type == PALETTE && !PNG_BACKGROUND transformation */

-   }

-#ifdef PNG_READ_BACKGROUND_SUPPORTED

-   else

-#endif

-#endif /* PNG_READ_GAMMA_SUPPORTED */

-

-#ifdef PNG_READ_BACKGROUND_SUPPORTED

-   /* No GAMMA transformation (see the hanging else 4 lines above) */

-   if ((png_ptr->transformations & PNG_COMPOSE) &&

-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))

-   {

-      int i;

-      int istop = (int)png_ptr->num_trans;

-      png_color back;

-      png_colorp palette = png_ptr->palette;

-

-      back.red   = (png_byte)png_ptr->background.red;

-      back.green = (png_byte)png_ptr->background.green;

-      back.blue  = (png_byte)png_ptr->background.blue;

-

-      for (i = 0; i < istop; i++)

-      {

-         if (png_ptr->trans_alpha[i] == 0)

-         {

-            palette[i] = back;

-         }

-

-         else if (png_ptr->trans_alpha[i] != 0xff)

-         {

-            /* The png_composite() macro is defined in png.h */

-            png_composite(palette[i].red, palette[i].red,

-                png_ptr->trans_alpha[i], back.red);

-

-            png_composite(palette[i].green, palette[i].green,

-                png_ptr->trans_alpha[i], back.green);

-

-            png_composite(palette[i].blue, palette[i].blue,

-                png_ptr->trans_alpha[i], back.blue);

-         }

-      }

-

-      png_ptr->transformations &= ~PNG_COMPOSE;

-   }

-#endif /* PNG_READ_BACKGROUND_SUPPORTED */

-

-#ifdef PNG_READ_SHIFT_SUPPORTED

-   if ((png_ptr->transformations & PNG_SHIFT) &&

-       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))

-   {

-      int i;

-      int istop = png_ptr->num_palette;

-      int shift = 8 - png_ptr->sig_bit.red;

-

-      /* significant bits can be in the range 1 to 7 for a meaninful result, if

-       * the number of significant bits is 0 then no shift is done (this is an

-       * error condition which is silently ignored.)

-       */

-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)

-      {

-         int component = png_ptr->palette[i].red;

-

-         component >>= shift;

-         png_ptr->palette[i].red = (png_byte)component;

-      }

-

-      shift = 8 - png_ptr->sig_bit.green;

-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)

-      {

-         int component = png_ptr->palette[i].green;

-

-         component >>= shift;

-         png_ptr->palette[i].green = (png_byte)component;

-      }

-

-      shift = 8 - png_ptr->sig_bit.blue;

-      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)

-      {

-         int component = png_ptr->palette[i].blue;

-

-         component >>= shift;

-         png_ptr->palette[i].blue = (png_byte)component;

-      }

-   }

-#endif  /* PNG_READ_SHIFT_SUPPORTED */

-}

-

-/* Modify the info structure to reflect the transformations.  The

- * info should be updated so a PNG file could be written with it,

- * assuming the transformations result in valid PNG data.

- */

-void /* PRIVATE */

-png_read_transform_info(png_structp png_ptr, png_infop info_ptr)

-{

-   png_debug(1, "in png_read_transform_info");

-

-#ifdef PNG_READ_EXPAND_SUPPORTED

-   if (png_ptr->transformations & PNG_EXPAND)

-   {

-      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

-      {

-         /* This check must match what actually happens in

-          * png_do_expand_palette; if it ever checks the tRNS chunk to see if

-          * it is all opaque we must do the same (at present it does not.)

-          */

-         if (png_ptr->num_trans > 0)

-            info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;

-

-         else

-            info_ptr->color_type = PNG_COLOR_TYPE_RGB;

-

-         info_ptr->bit_depth = 8;

-         info_ptr->num_trans = 0;

-      }

-      else

-      {

-         if (png_ptr->num_trans)

-         {

-            if (png_ptr->transformations & PNG_EXPAND_tRNS)

-               info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;

-         }

-         if (info_ptr->bit_depth < 8)

-            info_ptr->bit_depth = 8;

-

-         info_ptr->num_trans = 0;

-      }

-   }

-#endif

-

-#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\

-   defined(PNG_READ_ALPHA_MODE_SUPPORTED)

-   /* The following is almost certainly wrong unless the background value is in

-    * the screen space!

-    */

-   if (png_ptr->transformations & PNG_COMPOSE)

-      info_ptr->background = png_ptr->background;

-#endif

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),

-    * however it seems that the code in png_init_read_transformations, which has

-    * been called before this from png_read_update_info->png_read_start_row

-    * sometimes does the gamma transform and cancels the flag.

-    */

-   info_ptr->gamma = png_ptr->gamma;

-#endif

-

-   if (info_ptr->bit_depth == 16)

-   {

-#  ifdef PNG_READ_16BIT_SUPPORTED

-#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED

-         if (png_ptr->transformations & PNG_SCALE_16_TO_8)

-            info_ptr->bit_depth = 8;

-#     endif

-

-#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED

-         if (png_ptr->transformations & PNG_16_TO_8)

-            info_ptr->bit_depth = 8;

-#     endif

-

-#  else

-      /* No 16 bit support: force chopping 16-bit input down to 8, in this case

-       * the app program can chose if both APIs are available by setting the

-       * correct scaling to use.

-       */

-#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED

-         /* For compatibility with previous versions use the strip method by

-          * default.  This code works because if PNG_SCALE_16_TO_8 is already

-          * set the code below will do that in preference to the chop.

-          */

-         png_ptr->transformations |= PNG_16_TO_8;

-         info_ptr->bit_depth = 8;

-#     else

-

-#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED

-            png_ptr->transformations |= PNG_SCALE_16_TO_8;

-            info_ptr->bit_depth = 8;

-#        else

-

-            CONFIGURATION ERROR: you must enable at least one 16 to 8 method

-#        endif

-#    endif

-#endif /* !READ_16BIT_SUPPORTED */

-   }

-

-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED

-   if (png_ptr->transformations & PNG_GRAY_TO_RGB)

-      info_ptr->color_type = (png_byte)(info_ptr->color_type |

-         PNG_COLOR_MASK_COLOR);

-#endif

-

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-   if (png_ptr->transformations & PNG_RGB_TO_GRAY)

-      info_ptr->color_type = (png_byte)(info_ptr->color_type &

-         ~PNG_COLOR_MASK_COLOR);

-#endif

-

-#ifdef PNG_READ_QUANTIZE_SUPPORTED

-   if (png_ptr->transformations & PNG_QUANTIZE)

-   {

-      if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||

-          (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&

-          png_ptr->palette_lookup && info_ptr->bit_depth == 8)

-      {

-         info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;

-      }

-   }

-#endif

-

-#ifdef PNG_READ_EXPAND_16_SUPPORTED

-   if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&

-      info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)

-   {

-      info_ptr->bit_depth = 16;

-   }

-#endif

-

-#ifdef PNG_READ_PACK_SUPPORTED

-   if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))

-      info_ptr->bit_depth = 8;

-#endif

-

-   if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

-      info_ptr->channels = 1;

-

-   else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)

-      info_ptr->channels = 3;

-

-   else

-      info_ptr->channels = 1;

-

-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

-   if (png_ptr->transformations & PNG_STRIP_ALPHA)

-   {

-      info_ptr->color_type = (png_byte)(info_ptr->color_type &

-         ~PNG_COLOR_MASK_ALPHA);

-      info_ptr->num_trans = 0;

-   }

-#endif

-

-   if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)

-      info_ptr->channels++;

-

-#ifdef PNG_READ_FILLER_SUPPORTED

-   /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */

-   if ((png_ptr->transformations & PNG_FILLER) &&

-       ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||

-       (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))

-   {

-      info_ptr->channels++;

-      /* If adding a true alpha channel not just filler */

-      if (png_ptr->transformations & PNG_ADD_ALPHA)

-         info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;

-   }

-#endif

-

-#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \

-defined(PNG_READ_USER_TRANSFORM_SUPPORTED)

-   if (png_ptr->transformations & PNG_USER_TRANSFORM)

-   {

-      if (info_ptr->bit_depth < png_ptr->user_transform_depth)

-         info_ptr->bit_depth = png_ptr->user_transform_depth;

-

-      if (info_ptr->channels < png_ptr->user_transform_channels)

-         info_ptr->channels = png_ptr->user_transform_channels;

-   }

-#endif

-

-   info_ptr->pixel_depth = (png_byte)(info_ptr->channels *

-       info_ptr->bit_depth);

-

-   info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);

-

-   /* Adding in 1.5.4: cache the above value in png_struct so that we can later

-    * check in png_rowbytes that the user buffer won't get overwritten.  Note

-    * that the field is not always set - if png_read_update_info isn't called

-    * the application has to either not do any transforms or get the calculation

-    * right itself.

-    */

-   png_ptr->info_rowbytes = info_ptr->rowbytes;

-

-#ifndef PNG_READ_EXPAND_SUPPORTED

-   if (png_ptr)

-      return;

-#endif

-}

-

-/* Transform the row.  The order of transformations is significant,

- * and is very touchy.  If you add a transformation, take care to

- * decide how it fits in with the other transformations here.

- */

-void /* PRIVATE */

-png_do_read_transformations(png_structp png_ptr, png_row_infop row_info)

-{

-   png_debug(1, "in png_do_read_transformations");

-

-   if (png_ptr->row_buf == NULL)

-   {

-      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this

-       * error is incredibly rare and incredibly easy to debug without this

-       * information.

-       */

-      png_error(png_ptr, "NULL row buffer");

-   }

-

-   /* The following is debugging; prior to 1.5.4 the code was never compiled in;

-    * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro

-    * PNG_WARN_UNINITIALIZED_ROW removed.  In 1.5 the new flag is set only for

-    * selected new APIs to ensure that there is no API change.

-    */

-   if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&

-      !(png_ptr->flags & PNG_FLAG_ROW_INIT))

-   {

-      /* Application has failed to call either png_read_start_image() or

-       * png_read_update_info() after setting transforms that expand pixels.

-       * This check added to libpng-1.2.19 (but not enabled until 1.5.4).

-       */

-      png_error(png_ptr, "Uninitialized row");

-   }

-

-#ifdef PNG_READ_EXPAND_SUPPORTED

-   if (png_ptr->transformations & PNG_EXPAND)

-   {

-      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)

-      {

-         png_do_expand_palette(row_info, png_ptr->row_buf + 1,

-             png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);

-      }

-

-      else

-      {

-         if (png_ptr->num_trans &&

-             (png_ptr->transformations & PNG_EXPAND_tRNS))

-            png_do_expand(row_info, png_ptr->row_buf + 1,

-                &(png_ptr->trans_color));

-

-         else

-            png_do_expand(row_info, png_ptr->row_buf + 1,

-                NULL);

-      }

-   }

-#endif

-

-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&

-      !(png_ptr->transformations & PNG_COMPOSE) &&

-      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||

-      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))

-      png_do_strip_channel(row_info, png_ptr->row_buf + 1,

-         0 /* at_start == false, because SWAP_ALPHA happens later */);

-#endif

-

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-   if (png_ptr->transformations & PNG_RGB_TO_GRAY)

-   {

-      int rgb_error =

-          png_do_rgb_to_gray(png_ptr, row_info,

-              png_ptr->row_buf + 1);

-

-      if (rgb_error)

-      {

-         png_ptr->rgb_to_gray_status=1;

-         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==

-             PNG_RGB_TO_GRAY_WARN)

-            png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");

-

-         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==

-             PNG_RGB_TO_GRAY_ERR)

-            png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");

-      }

-   }

-#endif

-

-/* From Andreas Dilger e-mail to png-implement, 26 March 1998:

- *

- *   In most cases, the "simple transparency" should be done prior to doing

- *   gray-to-RGB, or you will have to test 3x as many bytes to check if a

- *   pixel is transparent.  You would also need to make sure that the

- *   transparency information is upgraded to RGB.

- *

- *   To summarize, the current flow is:

- *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite

- *                                   with background "in place" if transparent,

- *                                   convert to RGB if necessary

- *   - Gray + alpha -> composite with gray background and remove alpha bytes,

- *                                   convert to RGB if necessary

- *

- *   To support RGB backgrounds for gray images we need:

- *   - Gray + simple transparency -> convert to RGB + simple transparency,

- *                                   compare 3 or 6 bytes and composite with

- *                                   background "in place" if transparent

- *                                   (3x compare/pixel compared to doing

- *                                   composite with gray bkgrnd)

- *   - Gray + alpha -> convert to RGB + alpha, composite with background and

- *                                   remove alpha bytes (3x float

- *                                   operations/pixel compared with composite

- *                                   on gray background)

- *

- *  Greg's change will do this.  The reason it wasn't done before is for

- *  performance, as this increases the per-pixel operations.  If we would check

- *  in advance if the background was gray or RGB, and position the gray-to-RGB

- *  transform appropriately, then it would save a lot of work/time.

- */

-

-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED

-   /* If gray -> RGB, do so now only if background is non-gray; else do later

-    * for performance reasons

-    */

-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&

-       !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))

-      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);

-#endif

-

-#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\

-   (defined PNG_READ_ALPHA_MODE_SUPPORTED)

-   if (png_ptr->transformations & PNG_COMPOSE)

-      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);

-#endif

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-   if ((png_ptr->transformations & PNG_GAMMA) &&

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-      /* Because RGB_TO_GRAY does the gamma transform. */

-      !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&

-#endif

-#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\

-   (defined PNG_READ_ALPHA_MODE_SUPPORTED)

-      /* Because PNG_COMPOSE does the gamma transform if there is something to

-       * do (if there is an alpha channel or transparency.)

-       */

-       !((png_ptr->transformations & PNG_COMPOSE) &&

-       ((png_ptr->num_trans != 0) ||

-       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&

-#endif

-      /* Because png_init_read_transformations transforms the palette, unless

-       * RGB_TO_GRAY will do the transform.

-       */

-       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))

-      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);

-#endif

-

-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED

-   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&

-      (png_ptr->transformations & PNG_COMPOSE) &&

-      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||

-      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))

-      png_do_strip_channel(row_info, png_ptr->row_buf + 1,

-         0 /* at_start == false, because SWAP_ALPHA happens later */);

-#endif

-

-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED

-   if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&

-      (row_info->color_type & PNG_COLOR_MASK_ALPHA))

-      png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);

-#endif

-

-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED

-   if (png_ptr->transformations & PNG_SCALE_16_TO_8)

-      png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED

-   /* There is no harm in doing both of these because only one has any effect,

-    * by putting the 'scale' option first if the app asks for scale (either by

-    * calling the API or in a TRANSFORM flag) this is what happens.

-    */

-   if (png_ptr->transformations & PNG_16_TO_8)

-      png_do_chop(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_QUANTIZE_SUPPORTED

-   if (png_ptr->transformations & PNG_QUANTIZE)

-   {

-      png_do_quantize(row_info, png_ptr->row_buf + 1,

-          png_ptr->palette_lookup, png_ptr->quantize_index);

-

-      if (row_info->rowbytes == 0)

-         png_error(png_ptr, "png_do_quantize returned rowbytes=0");

-   }

-#endif /* PNG_READ_QUANTIZE_SUPPORTED */

-

-#ifdef PNG_READ_EXPAND_16_SUPPORTED

-   /* Do the expansion now, after all the arithmetic has been done.  Notice

-    * that previous transformations can handle the PNG_EXPAND_16 flag if this

-    * is efficient (particularly true in the case of gamma correction, where

-    * better accuracy results faster!)

-    */

-   if (png_ptr->transformations & PNG_EXPAND_16)

-      png_do_expand_16(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED

-   /*NOTE: moved here in 1.5.4 (from much later in this list.) */

-   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&

-       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))

-      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_INVERT_SUPPORTED

-   if (png_ptr->transformations & PNG_INVERT_MONO)

-      png_do_invert(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_SHIFT_SUPPORTED

-   if (png_ptr->transformations & PNG_SHIFT)

-      png_do_unshift(row_info, png_ptr->row_buf + 1,

-          &(png_ptr->shift));

-#endif

-

-#ifdef PNG_READ_PACK_SUPPORTED

-   if (png_ptr->transformations & PNG_PACK)

-      png_do_unpack(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_BGR_SUPPORTED

-   if (png_ptr->transformations & PNG_BGR)

-      png_do_bgr(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_PACKSWAP_SUPPORTED

-   if (png_ptr->transformations & PNG_PACKSWAP)

-      png_do_packswap(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_FILLER_SUPPORTED

-   if (png_ptr->transformations & PNG_FILLER)

-      png_do_read_filler(row_info, png_ptr->row_buf + 1,

-          (png_uint_32)png_ptr->filler, png_ptr->flags);

-#endif

-

-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED

-   if (png_ptr->transformations & PNG_INVERT_ALPHA)

-      png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED

-   if (png_ptr->transformations & PNG_SWAP_ALPHA)

-      png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);

-#endif

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-#ifdef PNG_READ_SWAP_SUPPORTED

-   if (png_ptr->transformations & PNG_SWAP_BYTES)

-      png_do_swap(row_info, png_ptr->row_buf + 1);

-#endif

-#endif

-

-#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED

-   if (png_ptr->transformations & PNG_USER_TRANSFORM)

-    {

-      if (png_ptr->read_user_transform_fn != NULL)

-         (*(png_ptr->read_user_transform_fn)) /* User read transform function */

-             (png_ptr,     /* png_ptr */

-             row_info,     /* row_info: */

-                /*  png_uint_32 width;       width of row */

-                /*  png_size_t rowbytes;     number of bytes in row */

-                /*  png_byte color_type;     color type of pixels */

-                /*  png_byte bit_depth;      bit depth of samples */

-                /*  png_byte channels;       number of channels (1-4) */

-                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */

-             png_ptr->row_buf + 1);    /* start of pixel data for row */

-#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED

-      if (png_ptr->user_transform_depth)

-         row_info->bit_depth = png_ptr->user_transform_depth;

-

-      if (png_ptr->user_transform_channels)

-         row_info->channels = png_ptr->user_transform_channels;

-#endif

-      row_info->pixel_depth = (png_byte)(row_info->bit_depth *

-          row_info->channels);

-

-      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);

-   }

-#endif

-}

-

-#ifdef PNG_READ_PACK_SUPPORTED

-/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,

- * without changing the actual values.  Thus, if you had a row with

- * a bit depth of 1, you would end up with bytes that only contained

- * the numbers 0 or 1.  If you would rather they contain 0 and 255, use

- * png_do_shift() after this.

- */

-void /* PRIVATE */

-png_do_unpack(png_row_infop row_info, png_bytep row)

-{

-   png_debug(1, "in png_do_unpack");

-

-   if (row_info->bit_depth < 8)

-   {

-      png_uint_32 i;

-      png_uint_32 row_width=row_info->width;

-

-      switch (row_info->bit_depth)

-      {

-         case 1:

-         {

-            png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);

-            png_bytep dp = row + (png_size_t)row_width - 1;

-            png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);

-            for (i = 0; i < row_width; i++)

-            {

-               *dp = (png_byte)((*sp >> shift) & 0x01);

-

-               if (shift == 7)

-               {

-                  shift = 0;

-                  sp--;

-               }

-

-               else

-                  shift++;

-

-               dp--;

-            }

-            break;

-         }

-

-         case 2:

-         {

-

-            png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);

-            png_bytep dp = row + (png_size_t)row_width - 1;

-            png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);

-            for (i = 0; i < row_width; i++)

-            {

-               *dp = (png_byte)((*sp >> shift) & 0x03);

-

-               if (shift == 6)

-               {

-                  shift = 0;

-                  sp--;

-               }

-

-               else

-                  shift += 2;

-

-               dp--;

-            }

-            break;

-         }

-

-         case 4:

-         {

-            png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);

-            png_bytep dp = row + (png_size_t)row_width - 1;

-            png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);

-            for (i = 0; i < row_width; i++)

-            {

-               *dp = (png_byte)((*sp >> shift) & 0x0f);

-

-               if (shift == 4)

-               {

-                  shift = 0;

-                  sp--;

-               }

-

-               else

-                  shift = 4;

-

-               dp--;

-            }

-            break;

-         }

-

-         default:

-            break;

-      }

-      row_info->bit_depth = 8;

-      row_info->pixel_depth = (png_byte)(8 * row_info->channels);

-      row_info->rowbytes = row_width * row_info->channels;

-   }

-}

-#endif

-

-#ifdef PNG_READ_SHIFT_SUPPORTED

-/* Reverse the effects of png_do_shift.  This routine merely shifts the

- * pixels back to their significant bits values.  Thus, if you have

- * a row of bit depth 8, but only 5 are significant, this will shift

- * the values back to 0 through 31.

- */

-void /* PRIVATE */

-png_do_unshift(png_row_infop row_info, png_bytep row,

-    png_const_color_8p sig_bits)

-{

-   int color_type;

-

-   png_debug(1, "in png_do_unshift");

-

-   /* The palette case has already been handled in the _init routine. */

-   color_type = row_info->color_type;

-

-   if (color_type != PNG_COLOR_TYPE_PALETTE)

-   {

-      int shift[4];

-      int channels = 0;

-      int bit_depth = row_info->bit_depth;

-

-      if (color_type & PNG_COLOR_MASK_COLOR)

-      {

-         shift[channels++] = bit_depth - sig_bits->red;

-         shift[channels++] = bit_depth - sig_bits->green;

-         shift[channels++] = bit_depth - sig_bits->blue;

-      }

-

-      else

-      {

-         shift[channels++] = bit_depth - sig_bits->gray;

-      }

-

-      if (color_type & PNG_COLOR_MASK_ALPHA)

-      {

-         shift[channels++] = bit_depth - sig_bits->alpha;

-      }

-

-      {

-         int c, have_shift;

-

-         for (c = have_shift = 0; c < channels; ++c)

-         {

-            /* A shift of more than the bit depth is an error condition but it

-             * gets ignored here.

-             */

-            if (shift[c] <= 0 || shift[c] >= bit_depth)

-               shift[c] = 0;

-

-            else

-               have_shift = 1;

-         }

-

-         if (!have_shift)

-            return;

-      }

-

-      switch (bit_depth)

-      {

-         default:

-         /* Must be 1bpp gray: should not be here! */

-            /* NOTREACHED */

-            break;

-

-         case 2:

-         /* Must be 2bpp gray */

-         /* assert(channels == 1 && shift[0] == 1) */

-         {

-            png_bytep bp = row;

-            png_bytep bp_end = bp + row_info->rowbytes;

-

-            while (bp < bp_end)

-            {

-               int b = (*bp >> 1) & 0x55;

-               *bp++ = (png_byte)b;

-            }

-            break;

-         }

-

-         case 4:

-         /* Must be 4bpp gray */

-         /* assert(channels == 1) */

-         {

-            png_bytep bp = row;

-            png_bytep bp_end = bp + row_info->rowbytes;

-            int gray_shift = shift[0];

-            int mask =  0xf >> gray_shift;

-

-            mask |= mask << 4;

-

-            while (bp < bp_end)

-            {

-               int b = (*bp >> gray_shift) & mask;

-               *bp++ = (png_byte)b;

-            }

-            break;

-         }

-

-         case 8:

-         /* Single byte components, G, GA, RGB, RGBA */

-         {

-            png_bytep bp = row;

-            png_bytep bp_end = bp + row_info->rowbytes;

-            int channel = 0;

-

-            while (bp < bp_end)

-            {

-               int b = *bp >> shift[channel];

-               if (++channel >= channels)

-                  channel = 0;

-               *bp++ = (png_byte)b;

-            }

-            break;

-         }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-         case 16:

-         /* Double byte components, G, GA, RGB, RGBA */

-         {

-            png_bytep bp = row;

-            png_bytep bp_end = bp + row_info->rowbytes;

-            int channel = 0;

-

-            while (bp < bp_end)

-            {

-               int value = (bp[0] << 8) + bp[1];

-

-               value >>= shift[channel];

-               if (++channel >= channels)

-                  channel = 0;

-               *bp++ = (png_byte)(value >> 8);

-               *bp++ = (png_byte)(value & 0xff);

-            }

-            break;

-         }

-#endif

-      }

-   }

-}

-#endif

-

-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED

-/* Scale rows of bit depth 16 down to 8 accurately */

-void /* PRIVATE */

-png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)

-{

-   png_debug(1, "in png_do_scale_16_to_8");

-

-   if (row_info->bit_depth == 16)

-   {

-      png_bytep sp = row; /* source */

-      png_bytep dp = row; /* destination */

-      png_bytep ep = sp + row_info->rowbytes; /* end+1 */

-

-      while (sp < ep)

-      {

-         /* The input is an array of 16 bit components, these must be scaled to

-          * 8 bits each.  For a 16 bit value V the required value (from the PNG

-          * specification) is:

-          *

-          *    (V * 255) / 65535

-          *

-          * This reduces to round(V / 257), or floor((V + 128.5)/257)

-          *

-          * Represent V as the two byte value vhi.vlo.  Make a guess that the

-          * result is the top byte of V, vhi, then the correction to this value

-          * is:

-          *

-          *    error = floor(((V-vhi.vhi) + 128.5) / 257)

-          *          = floor(((vlo-vhi) + 128.5) / 257)

-          *

-          * This can be approximated using integer arithmetic (and a signed

-          * shift):

-          *

-          *    error = (vlo-vhi+128) >> 8;

-          *

-          * The approximate differs from the exact answer only when (vlo-vhi) is

-          * 128; it then gives a correction of +1 when the exact correction is

-          * 0.  This gives 128 errors.  The exact answer (correct for all 16 bit

-          * input values) is:

-          *

-          *    error = (vlo-vhi+128)*65535 >> 24;

-          *

-          * An alternative arithmetic calculation which also gives no errors is:

-          *

-          *    (V * 255 + 32895) >> 16

-          */

-

-         png_int_32 tmp = *sp++; /* must be signed! */

-         tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;

-         *dp++ = (png_byte)tmp;

-      }

-

-      row_info->bit_depth = 8;

-      row_info->pixel_depth = (png_byte)(8 * row_info->channels);

-      row_info->rowbytes = row_info->width * row_info->channels;

-   }

-}

-#endif

-

-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED

-void /* PRIVATE */

-/* Simply discard the low byte.  This was the default behavior prior

- * to libpng-1.5.4.

- */

-png_do_chop(png_row_infop row_info, png_bytep row)

-{

-   png_debug(1, "in png_do_chop");

-

-   if (row_info->bit_depth == 16)

-   {

-      png_bytep sp = row; /* source */

-      png_bytep dp = row; /* destination */

-      png_bytep ep = sp + row_info->rowbytes; /* end+1 */

-

-      while (sp < ep)

-      {

-         *dp++ = *sp;

-         sp += 2; /* skip low byte */

-      }

-

-      row_info->bit_depth = 8;

-      row_info->pixel_depth = (png_byte)(8 * row_info->channels);

-      row_info->rowbytes = row_info->width * row_info->channels;

-   }

-}

-#endif

-

-#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED

-void /* PRIVATE */

-png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)

-{

-   png_debug(1, "in png_do_read_swap_alpha");

-

-   {

-      png_uint_32 row_width = row_info->width;

-      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

-      {

-         /* This converts from RGBA to ARGB */

-         if (row_info->bit_depth == 8)

-         {

-            png_bytep sp = row + row_info->rowbytes;

-            png_bytep dp = sp;

-            png_byte save;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               save = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = save;

-            }

-         }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-         /* This converts from RRGGBBAA to AARRGGBB */

-         else

-         {

-            png_bytep sp = row + row_info->rowbytes;

-            png_bytep dp = sp;

-            png_byte save[2];

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               save[0] = *(--sp);

-               save[1] = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = save[0];

-               *(--dp) = save[1];

-            }

-         }

-#endif

-      }

-

-      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)

-      {

-         /* This converts from GA to AG */

-         if (row_info->bit_depth == 8)

-         {

-            png_bytep sp = row + row_info->rowbytes;

-            png_bytep dp = sp;

-            png_byte save;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               save = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = save;

-            }

-         }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-         /* This converts from GGAA to AAGG */

-         else

-         {

-            png_bytep sp = row + row_info->rowbytes;

-            png_bytep dp = sp;

-            png_byte save[2];

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               save[0] = *(--sp);

-               save[1] = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = save[0];

-               *(--dp) = save[1];

-            }

-         }

-#endif

-      }

-   }

-}

-#endif

-

-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED

-void /* PRIVATE */

-png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)

-{

-   png_uint_32 row_width;

-   png_debug(1, "in png_do_read_invert_alpha");

-

-   row_width = row_info->width;

-   if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

-   {

-      if (row_info->bit_depth == 8)

-      {

-         /* This inverts the alpha channel in RGBA */

-         png_bytep sp = row + row_info->rowbytes;

-         png_bytep dp = sp;

-         png_uint_32 i;

-

-         for (i = 0; i < row_width; i++)

-         {

-            *(--dp) = (png_byte)(255 - *(--sp));

-

-/*          This does nothing:

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            We can replace it with:

-*/

-            sp-=3;

-            dp=sp;

-         }

-      }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-      /* This inverts the alpha channel in RRGGBBAA */

-      else

-      {

-         png_bytep sp = row + row_info->rowbytes;

-         png_bytep dp = sp;

-         png_uint_32 i;

-

-         for (i = 0; i < row_width; i++)

-         {

-            *(--dp) = (png_byte)(255 - *(--sp));

-            *(--dp) = (png_byte)(255 - *(--sp));

-

-/*          This does nothing:

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-            We can replace it with:

-*/

-            sp-=6;

-            dp=sp;

-         }

-      }

-#endif

-   }

-   else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)

-   {

-      if (row_info->bit_depth == 8)

-      {

-         /* This inverts the alpha channel in GA */

-         png_bytep sp = row + row_info->rowbytes;

-         png_bytep dp = sp;

-         png_uint_32 i;

-

-         for (i = 0; i < row_width; i++)

-         {

-            *(--dp) = (png_byte)(255 - *(--sp));

-            *(--dp) = *(--sp);

-         }

-      }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-      else

-      {

-         /* This inverts the alpha channel in GGAA */

-         png_bytep sp  = row + row_info->rowbytes;

-         png_bytep dp = sp;

-         png_uint_32 i;

-

-         for (i = 0; i < row_width; i++)

-         {

-            *(--dp) = (png_byte)(255 - *(--sp));

-            *(--dp) = (png_byte)(255 - *(--sp));

-/*

-            *(--dp) = *(--sp);

-            *(--dp) = *(--sp);

-*/

-            sp-=2;

-            dp=sp;

-         }

-      }

-#endif

-   }

-}

-#endif

-

-#ifdef PNG_READ_FILLER_SUPPORTED

-/* Add filler channel if we have RGB color */

-void /* PRIVATE */

-png_do_read_filler(png_row_infop row_info, png_bytep row,

-    png_uint_32 filler, png_uint_32 flags)

-{

-   png_uint_32 i;

-   png_uint_32 row_width = row_info->width;

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-   png_byte hi_filler = (png_byte)((filler>>8) & 0xff);

-#endif

-   png_byte lo_filler = (png_byte)(filler & 0xff);

-

-   png_debug(1, "in png_do_read_filler");

-

-   if (

-       row_info->color_type == PNG_COLOR_TYPE_GRAY)

-   {

-      if (row_info->bit_depth == 8)

-      {

-         if (flags & PNG_FLAG_FILLER_AFTER)

-         {

-            /* This changes the data from G to GX */

-            png_bytep sp = row + (png_size_t)row_width;

-            png_bytep dp =  sp + (png_size_t)row_width;

-            for (i = 1; i < row_width; i++)

-            {

-               *(--dp) = lo_filler;

-               *(--dp) = *(--sp);

-            }

-            *(--dp) = lo_filler;

-            row_info->channels = 2;

-            row_info->pixel_depth = 16;

-            row_info->rowbytes = row_width * 2;

-         }

-

-         else

-         {

-            /* This changes the data from G to XG */

-            png_bytep sp = row + (png_size_t)row_width;

-            png_bytep dp = sp  + (png_size_t)row_width;

-            for (i = 0; i < row_width; i++)

-            {

-               *(--dp) = *(--sp);

-               *(--dp) = lo_filler;

-            }

-            row_info->channels = 2;

-            row_info->pixel_depth = 16;

-            row_info->rowbytes = row_width * 2;

-         }

-      }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-      else if (row_info->bit_depth == 16)

-      {

-         if (flags & PNG_FLAG_FILLER_AFTER)

-         {

-            /* This changes the data from GG to GGXX */

-            png_bytep sp = row + (png_size_t)row_width * 2;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 1; i < row_width; i++)

-            {

-               *(--dp) = hi_filler;

-               *(--dp) = lo_filler;

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-            }

-            *(--dp) = hi_filler;

-            *(--dp) = lo_filler;

-            row_info->channels = 2;

-            row_info->pixel_depth = 32;

-            row_info->rowbytes = row_width * 4;

-         }

-

-         else

-         {

-            /* This changes the data from GG to XXGG */

-            png_bytep sp = row + (png_size_t)row_width * 2;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 0; i < row_width; i++)

-            {

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = hi_filler;

-               *(--dp) = lo_filler;

-            }

-            row_info->channels = 2;

-            row_info->pixel_depth = 32;

-            row_info->rowbytes = row_width * 4;

-         }

-      }

-#endif

-   } /* COLOR_TYPE == GRAY */

-   else if (row_info->color_type == PNG_COLOR_TYPE_RGB)

-   {

-      if (row_info->bit_depth == 8)

-      {

-         if (flags & PNG_FLAG_FILLER_AFTER)

-         {

-            /* This changes the data from RGB to RGBX */

-            png_bytep sp = row + (png_size_t)row_width * 3;

-            png_bytep dp = sp  + (png_size_t)row_width;

-            for (i = 1; i < row_width; i++)

-            {

-               *(--dp) = lo_filler;

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-            }

-            *(--dp) = lo_filler;

-            row_info->channels = 4;

-            row_info->pixel_depth = 32;

-            row_info->rowbytes = row_width * 4;

-         }

-

-         else

-         {

-            /* This changes the data from RGB to XRGB */

-            png_bytep sp = row + (png_size_t)row_width * 3;

-            png_bytep dp = sp + (png_size_t)row_width;

-            for (i = 0; i < row_width; i++)

-            {

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = lo_filler;

-            }

-            row_info->channels = 4;

-            row_info->pixel_depth = 32;

-            row_info->rowbytes = row_width * 4;

-         }

-      }

-

-#ifdef PNG_READ_16BIT_SUPPORTED

-      else if (row_info->bit_depth == 16)

-      {

-         if (flags & PNG_FLAG_FILLER_AFTER)

-         {

-            /* This changes the data from RRGGBB to RRGGBBXX */

-            png_bytep sp = row + (png_size_t)row_width * 6;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 1; i < row_width; i++)

-            {

-               *(--dp) = hi_filler;

-               *(--dp) = lo_filler;

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-            }

-            *(--dp) = hi_filler;

-            *(--dp) = lo_filler;

-            row_info->channels = 4;

-            row_info->pixel_depth = 64;

-            row_info->rowbytes = row_width * 8;

-         }

-

-         else

-         {

-            /* This changes the data from RRGGBB to XXRRGGBB */

-            png_bytep sp = row + (png_size_t)row_width * 6;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 0; i < row_width; i++)

-            {

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = *(--sp);

-               *(--dp) = hi_filler;

-               *(--dp) = lo_filler;

-            }

-

-            row_info->channels = 4;

-            row_info->pixel_depth = 64;

-            row_info->rowbytes = row_width * 8;

-         }

-      }

-#endif

-   } /* COLOR_TYPE == RGB */

-}

-#endif

-

-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED

-/* Expand grayscale files to RGB, with or without alpha */

-void /* PRIVATE */

-png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)

-{

-   png_uint_32 i;

-   png_uint_32 row_width = row_info->width;

-

-   png_debug(1, "in png_do_gray_to_rgb");

-

-   if (row_info->bit_depth >= 8 &&

-       !(row_info->color_type & PNG_COLOR_MASK_COLOR))

-   {

-      if (row_info->color_type == PNG_COLOR_TYPE_GRAY)

-      {

-         if (row_info->bit_depth == 8)

-         {

-            /* This changes G to RGB */

-            png_bytep sp = row + (png_size_t)row_width - 1;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 0; i < row_width; i++)

-            {

-               *(dp--) = *sp;

-               *(dp--) = *sp;

-               *(dp--) = *(sp--);

-            }

-         }

-

-         else

-         {

-            /* This changes GG to RRGGBB */

-            png_bytep sp = row + (png_size_t)row_width * 2 - 1;

-            png_bytep dp = sp  + (png_size_t)row_width * 4;

-            for (i = 0; i < row_width; i++)

-            {

-               *(dp--) = *sp;

-               *(dp--) = *(sp - 1);

-               *(dp--) = *sp;

-               *(dp--) = *(sp - 1);

-               *(dp--) = *(sp--);

-               *(dp--) = *(sp--);

-            }

-         }

-      }

-

-      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)

-      {

-         if (row_info->bit_depth == 8)

-         {

-            /* This changes GA to RGBA */

-            png_bytep sp = row + (png_size_t)row_width * 2 - 1;

-            png_bytep dp = sp  + (png_size_t)row_width * 2;

-            for (i = 0; i < row_width; i++)

-            {

-               *(dp--) = *(sp--);

-               *(dp--) = *sp;

-               *(dp--) = *sp;

-               *(dp--) = *(sp--);

-            }

-         }

-

-         else

-         {

-            /* This changes GGAA to RRGGBBAA */

-            png_bytep sp = row + (png_size_t)row_width * 4 - 1;

-            png_bytep dp = sp  + (png_size_t)row_width * 4;

-            for (i = 0; i < row_width; i++)

-            {

-               *(dp--) = *(sp--);

-               *(dp--) = *(sp--);

-               *(dp--) = *sp;

-               *(dp--) = *(sp - 1);

-               *(dp--) = *sp;

-               *(dp--) = *(sp - 1);

-               *(dp--) = *(sp--);

-               *(dp--) = *(sp--);

-            }

-         }

-      }

-      row_info->channels = (png_byte)(row_info->channels + 2);

-      row_info->color_type |= PNG_COLOR_MASK_COLOR;

-      row_info->pixel_depth = (png_byte)(row_info->channels *

-          row_info->bit_depth);

-      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);

-   }

-}

-#endif

-

-#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED

-/* Reduce RGB files to grayscale, with or without alpha

- * using the equation given in Poynton's ColorFAQ of 1998-01-04 at

- * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008 but

- * versions dated 1998 through November 2002 have been archived at

- * http://web.archive.org/web/20000816232553/http://www.inforamp.net/

- * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )

- * Charles Poynton poynton at poynton.com

- *

- *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B

- *

- *  which can be expressed with integers as

- *

- *     Y = (6969 * R + 23434 * G + 2365 * B)/32768

- *

- * Poynton's current link (as of January 2003 through July 2011):

- * <http://www.poynton.com/notes/colour_and_gamma/>

- * has changed the numbers slightly:

- *

- *     Y = 0.2126*R + 0.7152*G + 0.0722*B

- *

- *  which can be expressed with integers as

- *

- *     Y = (6966 * R + 23436 * G + 2366 * B)/32768

- *

- *  Historically, however, libpng uses numbers derived from the ITU-R Rec 709

- *  end point chromaticities and the D65 white point.  Depending on the

- *  precision used for the D65 white point this produces a variety of different

- *  numbers, however if the four decimal place value used in ITU-R Rec 709 is

- *  used (0.3127,0.3290) the Y calculation would be:

- *

- *     Y = (6968 * R + 23435 * G + 2366 * B)/32768

- *

- *  While this is correct the rounding results in an overflow for white, because

- *  the sum of the rounded coefficients is 32769, not 32768.  Consequently

- *  libpng uses, instead, the closest non-overflowing approximation:

- *

- *     Y = (6968 * R + 23434 * G + 2366 * B)/32768

- *

- *  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk

- *  (including an sRGB chunk) then the chromaticities are used to calculate the

- *  coefficients.  See the chunk handling in pngrutil.c for more information.

- *

- *  In all cases the calculation is to be done in a linear colorspace.  If no

- *  gamma information is available to correct the encoding of the original RGB

- *  values this results in an implicit assumption that the original PNG RGB

- *  values were linear.

- *

- *  Other integer coefficents can be used via png_set_rgb_to_gray().  Because

- *  the API takes just red and green coefficients the blue coefficient is

- *  calculated to make the sum 32768.  This will result in different rounding

- *  to that used above.

- */

-int /* PRIVATE */

-png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)

-

-{

-   int rgb_error = 0;

-

-   png_debug(1, "in png_do_rgb_to_gray");

-

-   if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&

-       (row_info->color_type & PNG_COLOR_MASK_COLOR))

-   {

-      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;

-      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;

-      PNG_CONST png_uint_32 bc = 32768 - rc - gc;

-      PNG_CONST png_uint_32 row_width = row_info->width;

-      PNG_CONST int have_alpha =

-         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;

-

-      if (row_info->bit_depth == 8)

-      {

-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)

-         /* Notice that gamma to/from 1 are not necessarily inverses (if

-          * there is an overall gamma correction).  Prior to 1.5.5 this code

-          * checked the linearized values for equality; this doesn't match

-          * the documentation, the original values must be checked.

-          */

-         if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)

-         {

-            png_bytep sp = row;

-            png_bytep dp = row;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               png_byte red   = *(sp++);

-               png_byte green = *(sp++);

-               png_byte blue  = *(sp++);

-

-               if (red != green || red != blue)

-               {

-                  red = png_ptr->gamma_to_1[red];

-                  green = png_ptr->gamma_to_1[green];

-                  blue = png_ptr->gamma_to_1[blue];

-

-                  rgb_error |= 1;

-                  *(dp++) = png_ptr->gamma_from_1[

-                      (rc*red + gc*green + bc*blue + 16384)>>15];

-               }

-

-               else

-               {

-                  /* If there is no overall correction the table will not be

-                   * set.

-                   */

-                  if (png_ptr->gamma_table != NULL)

-                     red = png_ptr->gamma_table[red];

-

-                  *(dp++) = red;

-               }

-

-               if (have_alpha)

-                  *(dp++) = *(sp++);

-            }

-         }

-         else

-#endif

-         {

-            png_bytep sp = row;

-            png_bytep dp = row;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               png_byte red   = *(sp++);

-               png_byte green = *(sp++);

-               png_byte blue  = *(sp++);

-

-               if (red != green || red != blue)

-               {

-                  rgb_error |= 1;

-                  /*NOTE: this is the historical approach which simply

-                   * truncates the results.

-                   */

-                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);

-               }

-

-               else

-                  *(dp++) = red;

-

-               if (have_alpha)

-                  *(dp++) = *(sp++);

-            }

-         }

-      }

-

-      else /* RGB bit_depth == 16 */

-      {

-#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)

-         if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)

-         {

-            png_bytep sp = row;

-            png_bytep dp = row;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               png_uint_16 red, green, blue, w;

-

-               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-

-               if (red == green && red == blue)

-               {

-                  if (png_ptr->gamma_16_table != NULL)

-                     w = png_ptr->gamma_16_table[(red&0xff)

-                         >> png_ptr->gamma_shift][red>>8];

-

-                  else

-                     w = red;

-               }

-

-               else

-               {

-                  png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)

-                      >> png_ptr->gamma_shift][red>>8];

-                  png_uint_16 green_1 =

-                      png_ptr->gamma_16_to_1[(green&0xff) >>

-                      png_ptr->gamma_shift][green>>8];

-                  png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)

-                      >> png_ptr->gamma_shift][blue>>8];

-                  png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1

-                      + bc*blue_1 + 16384)>>15);

-                  w = png_ptr->gamma_16_from_1[(gray16&0xff) >>

-                      png_ptr->gamma_shift][gray16 >> 8];

-                  rgb_error |= 1;

-               }

-

-               *(dp++) = (png_byte)((w>>8) & 0xff);

-               *(dp++) = (png_byte)(w & 0xff);

-

-               if (have_alpha)

-               {

-                  *(dp++) = *(sp++);

-                  *(dp++) = *(sp++);

-               }

-            }

-         }

-         else

-#endif

-         {

-            png_bytep sp = row;

-            png_bytep dp = row;

-            png_uint_32 i;

-

-            for (i = 0; i < row_width; i++)

-            {

-               png_uint_16 red, green, blue, gray16;

-

-               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;

-

-               if (red != green || red != blue)

-                  rgb_error |= 1;

-

-               /* From 1.5.5 in the 16 bit case do the accurate conversion even

-                * in the 'fast' case - this is because this is where the code

-                * ends up when handling linear 16 bit data.

-                */

-               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>

-                  15);

-               *(dp++) = (png_byte)((gray16>>8) & 0xff);

-               *(dp++) = (png_byte)(gray16 & 0xff);

-

-               if (have_alpha)

-               {

-                  *(dp++) = *(sp++);

-                  *(dp++) = *(sp++);

-               }

-            }

-         }

-      }

-

-      row_info->channels = (png_byte)(row_info->channels - 2);

-      row_info->color_type = (png_byte)(row_info->color_type &

-          ~PNG_COLOR_MASK_COLOR);

-      row_info->pixel_depth = (png_byte)(row_info->channels *

-          row_info->bit_depth);

-      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);

-   }

-   return rgb_error;

-}

-#endif

-#endif /* PNG_READ_TRANSFORMS_SUPPORTED */

-

-#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED

-/* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth

- * large of png_color.  This lets grayscale images be treated as

- * paletted.  Most useful for gamma correction and simplification

- * of code.  This API is not used internally.

- */

-void PNGAPI

-png_build_grayscale_palette(int bit_depth, png_colorp palette)

-{

-   int num_palette;

-   int color_inc;

-   int i;

-   int v;

-

-   png_debug(1, "in png_do_build_grayscale_palette");

-

-   if (palette == NULL)

-      return;

-

-   switch (bit_depth)

-   {

-      case 1:

-         num_palette = 2;

-         color_inc = 0xff;

-         break;

-

-      case 2:

-         num_palette = 4;

-         color_inc = 0x55;

-         break;

-

-      case 4:

-         num_palette = 16;

-         color_inc = 0x11;

-         break;

-

-      case 8:

-         num_palette = 256;

-         color_inc = 1;

-         break;

-

-      default:

-         num_palette = 0;

-         color_inc = 0;

-         break;

-   }

-

-   for (i = 0, v = 0; i < num_palette; i++, v += color_inc)

-   {

-      palette[i].red = (png_byte)v;

-      palette[i].green = (png_byte)v;

-      palette[i].blue = (png_byte)v;

-   }

-}

-#endif

-

-

-#ifdef PNG_READ_TRANSFORMS_SUPPORTED

-#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\

-   (defined PNG_READ_ALPHA_MODE_SUPPORTED)

-/* Replace any alpha or transparency with the supplied background color.

- * "background" is already in the screen gamma, while "background_1" is

- * at a gamma of 1.0.  Paletted files have already been taken care of.

- */

-void /* PRIVATE */

-png_do_compose(png_row_infop row_info, png_bytep row, png_structp png_ptr)

-{

-#ifdef PNG_READ_GAMMA_SUPPORTED

-   png_const_bytep gamma_table = png_ptr->gamma_table;

-   png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;

-   png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;

-   png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;

-   png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;

-   png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;

-   int gamma_shift = png_ptr->gamma_shift;

-#endif

-

-   png_bytep sp;

-   png_uint_32 i;

-   png_uint_32 row_width = row_info->width;

-   int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;

-   int shift;

-

-   png_debug(1, "in png_do_compose");

-

-   {

-      switch (row_info->color_type)

-      {

-         case PNG_COLOR_TYPE_GRAY:

-         {

-            switch (row_info->bit_depth)

-            {

-               case 1:

-               {

-                  sp = row;

-                  shift = 7;

-                  for (i = 0; i < row_width; i++)

-                  {

-                     if ((png_uint_16)((*sp >> shift) & 0x01)

-                        == png_ptr->trans_color.gray)

-                     {

-                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);

-                        *sp |= (png_byte)(png_ptr->background.gray << shift);

-                     }

-

-                     if (!shift)

-                     {

-                        shift = 7;

-                        sp++;

-                     }

-

-                     else

-                        shift--;

-                  }

-                  break;

-               }

-

-               case 2:

-               {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-                  if (gamma_table != NULL)

-                  {

-                     sp = row;

-                     shift = 6;

-                     for (i = 0; i < row_width; i++)

-                     {

-                        if ((png_uint_16)((*sp >> shift) & 0x03)

-                            == png_ptr->trans_color.gray)

-                        {

-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);

-                           *sp |= (png_byte)(png_ptr->background.gray << shift);

-                        }

-

-                        else

-                        {

-                           png_byte p = (png_byte)((*sp >> shift) & 0x03);

-                           png_byte g = (png_byte)((gamma_table [p | (p << 2) |

-                               (p << 4) | (p << 6)] >> 6) & 0x03);

-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);

-                           *sp |= (png_byte)(g << shift);

-                        }

-

-                        if (!shift)

-                        {

-                           shift = 6;

-                           sp++;

-                        }

-

-                        else

-                           shift -= 2;

-                     }

-                  }

-

-                  else

-#endif

-                  {

-                     sp = row;

-                     shift = 6;

-                     for (i = 0; i < row_width; i++)

-                     {

-                        if ((png_uint_16)((*sp >> shift) & 0x03)

-                            == png_ptr->trans_color.gray)

-                        {

-                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);

-                           *sp |= (png_byte)(png_ptr->background.gray << shift);

-                        }

-

-                        if (!shift)

-                        {

-                           shift = 6;

-                           sp++;

-                        }

-

-                        else

-                           shift -= 2;

-                     }

-                  }

-                  break;

-               }

-

-               case 4:

-               {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-                  if (gamma_table != NULL)

-                  {

-                     sp = row;

-                     shift = 4;

-                     for (i = 0; i < row_width; i++)

-                     {

-                        if ((png_uint_16)((*sp >> shift) & 0x0f)

-                            == png_ptr->trans_color.gray)

-                        {

-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);

-                           *sp |= (png_byte)(png_ptr->background.gray << shift);

-                        }

-

-                        else

-                        {

-                           png_byte p = (png_byte)((*sp >> shift) & 0x0f);

-                           png_byte g = (png_byte)((gamma_table[p |

-                               (p << 4)] >> 4) & 0x0f);

-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);

-                           *sp |= (png_byte)(g << shift);

-                        }

-

-                        if (!shift)

-                        {

-                           shift = 4;

-                           sp++;

-                        }

-

-                        else

-                           shift -= 4;

-                     }

-                  }

-

-                  else

-#endif

-                  {

-                     sp = row;

-                     shift = 4;

-                     for (i = 0; i < row_width; i++)

-                     {

-                        if ((png_uint_16)((*sp >> shift) & 0x0f)

-                            == png_ptr->trans_color.gray)

-                        {

-                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);

-                           *sp |= (png_byte)(png_ptr->background.gray << shift);

-                        }

-

-                        if (!shift)

-                        {

-                           shift = 4;

-                           sp++;

-                        }

-

-                        else

-                           shift -= 4;

-                     }

-                  }

-                  break;

-               }

-

-               case 8:

-               {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-                  if (gamma_table != NULL)

-                  {

-                     sp = row;

-                     for (i = 0; i < row_width; i++, sp++)

-                     {

-                        if (*sp == png_ptr->trans_color.gray)

-                           *sp = (png_byte)png_ptr->background.gray;

-

-                        else

-                           *sp = gamma_table[*sp];

-                     }

-                  }

-                  else

-#endif

-                  {

-                     sp = row;

-                     for (i = 0; i < row_width; i++, sp++)

-                     {

-                        if (*sp == png_ptr->trans_color.gray)

-                           *sp = (png_byte)png_ptr->background.gray;

-                     }

-                  }

-                  break;

-               }

-

-               case 16:

-               {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-                  if (gamma_16 != NULL)

-                  {

-                     sp = row;

-                     for (i = 0; i < row_width; i++, sp += 2)

-                     {

-                        png_uint_16 v;

-

-                        v = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-

-                        if (v == png_ptr->trans_color.gray)

-                        {

-                           /* Background is already in screen gamma */

-                           *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);

-                           *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);

-                        }

-

-                        else

-                        {

-                           v = gamma_16[*(sp + 1) >> gamma_shift][*sp];

-                           *sp = (png_byte)((v >> 8) & 0xff);

-                           *(sp + 1) = (png_byte)(v & 0xff);

-                        }

-                     }

-                  }

-                  else

-#endif

-                  {

-                     sp = row;

-                     for (i = 0; i < row_width; i++, sp += 2)

-                     {

-                        png_uint_16 v;

-

-                        v = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-

-                        if (v == png_ptr->trans_color.gray)

-                        {

-                           *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);

-                           *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);

-                        }

-                     }

-                  }

-                  break;

-               }

-

-               default:

-                  break;

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_RGB:

-         {

-            if (row_info->bit_depth == 8)

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_table != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 3)

-                  {

-                     if (*sp == png_ptr->trans_color.red &&

-                         *(sp + 1) == png_ptr->trans_color.green &&

-                         *(sp + 2) == png_ptr->trans_color.blue)

-                     {

-                        *sp = (png_byte)png_ptr->background.red;

-                        *(sp + 1) = (png_byte)png_ptr->background.green;

-                        *(sp + 2) = (png_byte)png_ptr->background.blue;

-                     }

-

-                     else

-                     {

-                        *sp = gamma_table[*sp];

-                        *(sp + 1) = gamma_table[*(sp + 1)];

-                        *(sp + 2) = gamma_table[*(sp + 2)];

-                     }

-                  }

-               }

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 3)

-                  {

-                     if (*sp == png_ptr->trans_color.red &&

-                         *(sp + 1) == png_ptr->trans_color.green &&

-                         *(sp + 2) == png_ptr->trans_color.blue)

-                     {

-                        *sp = (png_byte)png_ptr->background.red;

-                        *(sp + 1) = (png_byte)png_ptr->background.green;

-                        *(sp + 2) = (png_byte)png_ptr->background.blue;

-                     }

-                  }

-               }

-            }

-            else /* if (row_info->bit_depth == 16) */

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_16 != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 6)

-                  {

-                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-

-                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)

-                         + *(sp + 3));

-

-                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)

-                         + *(sp + 5));

-

-                     if (r == png_ptr->trans_color.red &&

-                         g == png_ptr->trans_color.green &&

-                         b == png_ptr->trans_color.blue)

-                     {

-                        /* Background is already in screen gamma */

-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);

-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);

-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);

-                     }

-

-                     else

-                     {

-                        png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];

-                        *sp = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(v & 0xff);

-

-                        v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];

-                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(v & 0xff);

-

-                        v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];

-                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(v & 0xff);

-                     }

-                  }

-               }

-

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 6)

-                  {

-                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-

-                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)

-                         + *(sp + 3));

-

-                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)

-                         + *(sp + 5));

-

-                     if (r == png_ptr->trans_color.red &&

-                         g == png_ptr->trans_color.green &&

-                         b == png_ptr->trans_color.blue)

-                     {

-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);

-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);

-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);

-                     }

-                  }

-               }

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_GRAY_ALPHA:

-         {

-            if (row_info->bit_depth == 8)

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_to_1 != NULL && gamma_from_1 != NULL &&

-                   gamma_table != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 2)

-                  {

-                     png_uint_16 a = *(sp + 1);

-

-                     if (a == 0xff)

-                        *sp = gamma_table[*sp];

-

-                     else if (a == 0)

-                     {

-                        /* Background is already in screen gamma */

-                        *sp = (png_byte)png_ptr->background.gray;

-                     }

-

-                     else

-                     {

-                        png_byte v, w;

-

-                        v = gamma_to_1[*sp];

-                        png_composite(w, v, a, png_ptr->background_1.gray);

-                        if (!optimize)

-                           w = gamma_from_1[w];

-                        *sp = w;

-                     }

-                  }

-               }

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 2)

-                  {

-                     png_byte a = *(sp + 1);

-

-                     if (a == 0)

-                        *sp = (png_byte)png_ptr->background.gray;

-

-                     else if (a < 0xff)

-                        png_composite(*sp, *sp, a, png_ptr->background_1.gray);

-                  }

-               }

-            }

-            else /* if (png_ptr->bit_depth == 16) */

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_16 != NULL && gamma_16_from_1 != NULL &&

-                   gamma_16_to_1 != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 4)

-                  {

-                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)

-                         + *(sp + 3));

-

-                     if (a == (png_uint_16)0xffff)

-                     {

-                        png_uint_16 v;

-

-                        v = gamma_16[*(sp + 1) >> gamma_shift][*sp];

-                        *sp = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(v & 0xff);

-                     }

-

-                     else if (a == 0)

-                     {

-                        /* Background is already in screen gamma */

-                        *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);

-                     }

-

-                     else

-                     {

-                        png_uint_16 g, v, w;

-

-                        g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];

-                        png_composite_16(v, g, a, png_ptr->background_1.gray);

-                        if (optimize)

-                           w = v;

-                        else

-                           w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];

-                        *sp = (png_byte)((w >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(w & 0xff);

-                     }

-                  }

-               }

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 4)

-                  {

-                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)

-                         + *(sp + 3));

-

-                     if (a == 0)

-                     {

-                        *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);

-                     }

-

-                     else if (a < 0xffff)

-                     {

-                        png_uint_16 g, v;

-

-                        g = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-                        png_composite_16(v, g, a, png_ptr->background_1.gray);

-                        *sp = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(v & 0xff);

-                     }

-                  }

-               }

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_RGB_ALPHA:

-         {

-            if (row_info->bit_depth == 8)

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_to_1 != NULL && gamma_from_1 != NULL &&

-                   gamma_table != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 4)

-                  {

-                     png_byte a = *(sp + 3);

-

-                     if (a == 0xff)

-                     {

-                        *sp = gamma_table[*sp];

-                        *(sp + 1) = gamma_table[*(sp + 1)];

-                        *(sp + 2) = gamma_table[*(sp + 2)];

-                     }

-

-                     else if (a == 0)

-                     {

-                        /* Background is already in screen gamma */

-                        *sp = (png_byte)png_ptr->background.red;

-                        *(sp + 1) = (png_byte)png_ptr->background.green;

-                        *(sp + 2) = (png_byte)png_ptr->background.blue;

-                     }

-

-                     else

-                     {

-                        png_byte v, w;

-

-                        v = gamma_to_1[*sp];

-                        png_composite(w, v, a, png_ptr->background_1.red);

-                        if (!optimize) w = gamma_from_1[w];

-                        *sp = w;

-

-                        v = gamma_to_1[*(sp + 1)];

-                        png_composite(w, v, a, png_ptr->background_1.green);

-                        if (!optimize) w = gamma_from_1[w];

-                        *(sp + 1) = w;

-

-                        v = gamma_to_1[*(sp + 2)];

-                        png_composite(w, v, a, png_ptr->background_1.blue);

-                        if (!optimize) w = gamma_from_1[w];

-                        *(sp + 2) = w;

-                     }

-                  }

-               }

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 4)

-                  {

-                     png_byte a = *(sp + 3);

-

-                     if (a == 0)

-                     {

-                        *sp = (png_byte)png_ptr->background.red;

-                        *(sp + 1) = (png_byte)png_ptr->background.green;

-                        *(sp + 2) = (png_byte)png_ptr->background.blue;

-                     }

-

-                     else if (a < 0xff)

-                     {

-                        png_composite(*sp, *sp, a, png_ptr->background.red);

-

-                        png_composite(*(sp + 1), *(sp + 1), a,

-                            png_ptr->background.green);

-

-                        png_composite(*(sp + 2), *(sp + 2), a,

-                            png_ptr->background.blue);

-                     }

-                  }

-               }

-            }

-            else /* if (row_info->bit_depth == 16) */

-            {

-#ifdef PNG_READ_GAMMA_SUPPORTED

-               if (gamma_16 != NULL && gamma_16_from_1 != NULL &&

-                   gamma_16_to_1 != NULL)

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 8)

-                  {

-                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))

-                         << 8) + (png_uint_16)(*(sp + 7)));

-

-                     if (a == (png_uint_16)0xffff)

-                     {

-                        png_uint_16 v;

-

-                        v = gamma_16[*(sp + 1) >> gamma_shift][*sp];

-                        *sp = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(v & 0xff);

-

-                        v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];

-                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(v & 0xff);

-

-                        v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];

-                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(v & 0xff);

-                     }

-

-                     else if (a == 0)

-                     {

-                        /* Background is already in screen gamma */

-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);

-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);

-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);

-                     }

-

-                     else

-                     {

-                        png_uint_16 v, w;

-

-                        v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];

-                        png_composite_16(w, v, a, png_ptr->background_1.red);

-                        if (!optimize)

-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];

-                        *sp = (png_byte)((w >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(w & 0xff);

-

-                        v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];

-                        png_composite_16(w, v, a, png_ptr->background_1.green);

-                        if (!optimize)

-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];

-

-                        *(sp + 2) = (png_byte)((w >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(w & 0xff);

-

-                        v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];

-                        png_composite_16(w, v, a, png_ptr->background_1.blue);

-                        if (!optimize)

-                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];

-

-                        *(sp + 4) = (png_byte)((w >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(w & 0xff);

-                     }

-                  }

-               }

-

-               else

-#endif

-               {

-                  sp = row;

-                  for (i = 0; i < row_width; i++, sp += 8)

-                  {

-                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))

-                         << 8) + (png_uint_16)(*(sp + 7)));

-

-                     if (a == 0)

-                     {

-                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);

-                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);

-                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);

-                     }

-

-                     else if (a < 0xffff)

-                     {

-                        png_uint_16 v;

-

-                        png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));

-                        png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)

-                            + *(sp + 3));

-                        png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)

-                            + *(sp + 5));

-

-                        png_composite_16(v, r, a, png_ptr->background.red);

-                        *sp = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 1) = (png_byte)(v & 0xff);

-

-                        png_composite_16(v, g, a, png_ptr->background.green);

-                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 3) = (png_byte)(v & 0xff);

-

-                        png_composite_16(v, b, a, png_ptr->background.blue);

-                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);

-                        *(sp + 5) = (png_byte)(v & 0xff);

-                     }

-                  }

-               }

-            }

-            break;

-         }

-

-         default:

-            break;

-      }

-   }

-}

-#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */

-

-#ifdef PNG_READ_GAMMA_SUPPORTED

-/* Gamma correct the image, avoiding the alpha channel.  Make sure

- * you do this after you deal with the transparency issue on grayscale

- * or RGB images. If your bit depth is 8, use gamma_table, if it

- * is 16, use gamma_16_table and gamma_shift.  Build these with

- * build_gamma_table().

- */

-void /* PRIVATE */

-png_do_gamma(png_row_infop row_info, png_bytep row, png_structp png_ptr)

-{

-   png_const_bytep gamma_table = png_ptr->gamma_table;

-   png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;

-   int gamma_shift = png_ptr->gamma_shift;

-

-   png_bytep sp;

-   png_uint_32 i;

-   png_uint_32 row_width=row_info->width;

-

-   png_debug(1, "in png_do_gamma");

-

-   if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||

-       (row_info->bit_depth == 16 && gamma_16_table != NULL)))

-   {

-      switch (row_info->color_type)

-      {

-         case PNG_COLOR_TYPE_RGB:

-         {

-            if (row_info->bit_depth == 8)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  *sp = gamma_table[*sp];

-                  sp++;

-                  *sp = gamma_table[*sp];

-                  sp++;

-                  *sp = gamma_table[*sp];

-                  sp++;

-               }

-            }

-

-            else /* if (row_info->bit_depth == 16) */

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  png_uint_16 v;

-

-                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-

-                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-

-                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-               }

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_RGB_ALPHA:

-         {

-            if (row_info->bit_depth == 8)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  *sp = gamma_table[*sp];

-                  sp++;

-

-                  *sp = gamma_table[*sp];

-                  sp++;

-

-                  *sp = gamma_table[*sp];

-                  sp++;

-

-                  sp++;

-               }

-            }

-

-            else /* if (row_info->bit_depth == 16) */

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-

-                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-

-                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 4;

-               }

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_GRAY_ALPHA:

-         {

-            if (row_info->bit_depth == 8)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  *sp = gamma_table[*sp];

-                  sp += 2;

-               }

-            }

-

-            else /* if (row_info->bit_depth == 16) */

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 4;

-               }

-            }

-            break;

-         }

-

-         case PNG_COLOR_TYPE_GRAY:

-         {

-            if (row_info->bit_depth == 2)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i += 4)

-               {

-                  int a = *sp & 0xc0;

-                  int b = *sp & 0x30;

-                  int c = *sp & 0x0c;

-                  int d = *sp & 0x03;

-

-                  *sp = (png_byte)(

-                      ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|

-                      ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|

-                      ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|

-                      ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));

-                  sp++;

-               }

-            }

-

-            if (row_info->bit_depth == 4)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i += 2)

-               {

-                  int msb = *sp & 0xf0;

-                  int lsb = *sp & 0x0f;

-

-                  *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)

-                      | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));

-                  sp++;

-               }

-            }

-

-            else if (row_info->bit_depth == 8)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  *sp = gamma_table[*sp];

-                  sp++;

-               }

-            }

-

-            else if (row_info->bit_depth == 16)

-            {

-               sp = row;

-               for (i = 0; i < row_width; i++)

-               {

-                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];

-                  *sp = (png_byte)((v >> 8) & 0xff);

-                  *(sp + 1) = (png_byte)(v & 0xff);

-                  sp += 2;

-               }

-            }

-            break;

-         }

-

-         default:

-            break;

-      }

-   }

-}

-#endif

-

-#ifdef PNG_READ_ALPHA_MODE_SUPPORTED

-/* Encode the alpha channel to the output gamma (the input channel is always

- * linear.)  Called only with color types that have an alpha channel.  Needs the

- * from_1 tables.

- */

-void /* PRIVATE */

-png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structp png_ptr)

-{

-   png_uint_32 row_width = row_info->width;

-

-   png_debug(1, "in png_do_encode_alpha");

-

-   if (row_info->color_type & PNG_COLOR_MASK_ALPHA)

-   {

-      if (row_info->bit_depth == 8)

-      {

-         PNG_CONST png_bytep table = png_ptr->gamma_from_1;

-

-         if (table != NULL)

-         {

-            PNG_CONST int step =

-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;

-

-            /* The alpha channel is the last component: */

-            row += step - 1;

-

-            for (; row_width > 0; --row_width, row += step)

-               *row = table[*row];

-

-            return;

-         }

-      }

-

-      else if (row_info->bit_depth == 16)

-      {

-         PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;

-         PNG_CONST int gamma_shift = png_ptr->gamma_shift;

-

-         if (table != NULL)

-         {

-            PNG_CONST int step =

-               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;

-

-            /* The alpha channel is the last component: */

-            row += step - 2;

-

-            for (; row_width > 0; --row_width, row += step)

-            {

-               png_uint_16 v;

-

-               v = table[*(row + 1) >> gamma_shift][*row];

-               *row = (png_byte)((v >> 8) & 0xff);

-               *(row + 1) = (png_byte)(v & 0xff);

-            }

-

-            return;

-         }

-      }

-   }

-

-   /* Only get to here if called with a weird row_info; no harm has been done,

-    * so just issue a warning.

-    */

-   png_warning(png_ptr, "png_do_encode_alpha: unexpected call");

-}

-#endif

-

-#ifdef PNG_READ_EXPAND_SUPPORTED

-/* Expands a palette row to an RGB or RGBA row depending

- * upon whether you supply trans and num_trans.

- */

-void /* PRIVATE */

-png_do_expand_palette(png_row_infop row_info, png_bytep row,

-   png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)

-{

-   int shift, value;

-   png_bytep sp, dp;

-   png_uint_32 i;

-   png_uint_32 row_width=row_info->width;

-

-   png_debug(1, "in png_do_expand_palette");

-

-   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)

-   {

-      if (row_info->bit_depth < 8)

-      {

-         switch (row_info->bit_depth)

-         {

-            case 1:

-            {

-               sp = row + (png_size_t)((row_width - 1) >> 3);

-               dp = row + (png_size_t)row_width - 1;

-               shift = 7 - (int)((row_width + 7) & 0x07);

-               for (i = 0; i < row_width; i++)

-               {

-                  if ((*sp >> shift) & 0x01)

-                     *dp = 1;

-

-                  else

-                     *dp = 0;

-

-                  if (shift == 7)

-                  {

-                     shift = 0;

-                     sp--;

-                  }

-

-                  else

-                     shift++;

-

-                  dp--;

-               }

-               break;

-            }

-

-            case 2:

-            {

-               sp = row + (png_size_t)((row_width - 1) >> 2);

-               dp = row + (png_size_t)row_width - 1;

-               shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);

-               for (i = 0; i < row_width; i++)

-               {

-                  value = (*sp >> shift) & 0x03;

-                  *dp = (png_byte)value;

-                  if (shift == 6)

-                  {

-                     shift = 0;

-                     sp--;

-                  }

-

-                  else

-                     shift += 2;

-

-                  dp--;

-               }

-               break;

-            }

-

-            case 4:

-            {

-               sp = row + (png_size_t)((row_width - 1) >> 1);

-               dp = row + (png_size_t)row_width - 1;

-               shift = (int)((row_width & 0x01) << 2);

-               for (i = 0; i < row_width; i++)

-               {

-                  value = (*sp >> shift) & 0x0f;

-                  *dp = (png_byte)value;

-                  if (shift == 4)

-                  {

-                     shift = 0;

-                     sp--;

-                  }

-

-                  else

-                     shift += 4;

-

-                  dp--;

-               }

-               break;

-            }

-

-            default:

-               break;

-         }

-         row_info->bit_depth = 8;

-         row_info->pixel_depth = 8;

-         row_info->rowbytes = row_width;

-      }

-

-      if (row_info->bit_depth == 8)

-      {

-         {

-            if (num_trans > 0)

-            {

-               sp = row + (png_size_t)row_width - 1;

-               dp = row + (png_size_t)(row_width << 2) - 1;

-

-               for (i = 0; i < row_width; i++)

-               {

-                  if ((int)(*sp) >= num_trans)

-                     *dp-- = 0xff;

-

-                  else

-                     *dp-- = trans_alpha[*sp];

-

-                  *dp-- = palette[*sp].blue;

-                  *dp-- = palette[*sp].green;

-                  *dp-- = palette[*sp].red;

-                  sp--;

-               }

-               row_info->bit_depth = 8;

-               row_info->pixel_depth = 32;

-               row_info->rowbytes = row_width * 4;

-               row_info->color_type = 6;

-               row_info->channels = 4;

-            }

-

-            else

-            {

-               sp = row + (png_size_t)row_width - 1;

-               dp = row + (png_size_t)(row_width * 3) - 1;

-

-               for (i = 0; i < row_width; i++)

-               {

-                  *dp-- = palette[*sp].blue;

-                  *dp-- = palette[*sp].green;

-                  *dp-- = palette[*sp].red;

-                  sp--;

-               }

-

-               row_info->bit_depth = 8;

-               row_info->pixel_depth = 24;

-               row_info->rowbytes = row_width * 3;

-               row_info->color_type = 2;

-               row_info->channels = 3;

-            }

-         }

-      }

-   }

-}

-

-/* If the bit depth < 8, it is expanded to 8.  Also, if the already

- * expanded transparency value is supplied, an alpha channel is built.

- */

-void /* PRIVATE */

-png_do_expand(png_row_infop row_info, png_bytep row,

-    png_const_color_16p trans_color)

-{

-   int shift, value;

-   png_bytep sp, dp;

-   png_uint_32 i;

-   png_uint_32 row_width=row_info->width;

-

-   png_debug(1, "in png_do_expand");

-

-   {

-      if (row_info->color_type == PNG_COLOR_TYPE_GRAY)

-      {

-         png_uint_16 gray = (png_uint_16)(trans_color ? trans_color->gray : 0);

-

-         if (row_info->bit_depth < 8)

-         {

-            switch (row_info->bit_depth)

-            {

-               case 1:

-               {

-                  gray = (png_uint_16)((gray & 0x01) * 0xff);

-                  sp = row + (png_size_t)((row_width - 1) >> 3);

-                  dp = row + (png_size_t)row_width - 1;

-                  shift = 7 - (int)((row_width + 7) & 0x07);

-                  for (i = 0; i < row_width; i++)

-                  {

-                     if ((*sp >> shift) & 0x01)

-                        *dp = 0xff;

-

-                     else

-                        *dp = 0;

-

-                     if (shift == 7)

-                     {

-                        shift = 0;

-                        sp--;

-                     }

-

-                     else

-                        shift++;

-

-                     dp--;

-                  }

-                  break;

-               }

-

-               case 2:

-               {

-                  gray = (png_uint_16)((gray & 0x03) * 0x55);

-                  sp = row + (png_size_t)((row_width - 1) >> 2);

-                  dp = row + (png_size_t)row_width - 1;

-                  shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);

-                  for (i = 0; i < row_width; i++)

-                  {

-                     value = (*sp >> shift) & 0x03;

-                     *dp = (png_byte)(value | (value << 2) | (value << 4) |

-                        (value << 6));

-                     if (shift == 6)

-                     {

-                        shift = 0;

-                        sp--;

-                     }

-

-                     else

-                        shift += 2;

-

-                     dp--;

-                  }

-                  break;

-               }

-

-               case 4:

-               {

-                  gray = (png_uint_16)((gray & 0x0f) * 0x11);

-                  sp = row + (png_size_t)((row_width - 1) >> 1);

-                  dp = row + (png_size_t)row_width - 1;

-                  shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);

-                  for (i = 0; i < row_width; i++)

-                  {

-                     value = (*sp >> shift) & 0x0f;

-                     *dp = (png_byte)(value | (value << 4));

-                     if (shift == 4)

-                     {

-                        shift = 0;

-                        sp--;

-                     }

-

-                     else

-                        shift = 4;

-

-                     dp--;

-                  }

-                  break;

-               }

-

-               default:

-                  break;

-            }

-

-            row_info->bit_depth = 8;

-            row_info->pixel_depth = 8;

-            row_info->rowbytes = row_width;

-         }

-

-         if (trans_color != NULL)

-         {

-            if (row_info->bit_depth == 8)

-            {

-               gray = gray & 0xff;

-               sp = row + (png_size_t)row_width - 1;

-               dp = row + (png_size_t)(row_width << 1) - 1;

-

-               for (i = 0; i < row_width; i++)

-               {

-                  if (*sp == gray)

-                     *dp-- = 0;

-

-                  else

-                     *dp-- = 0xff;

-

-                  *dp-- = *sp--;

-               }

-            }

-

-            else if (row_info->bit_depth == 16)

-            {

-               png_byte gray_high = (png_byte)((gray >> 8) & 0xff);

-               png_byte gray_low = (png_byte)(gray & 0xff);

-               sp = row + row_info->rowbytes - 1;

-               dp = row + (row_info->rowbytes << 1) - 1;

-               for (i = 0; i < row_width; i++)

-               {

-                  if (*(sp - 1) == gray_high && *(sp) == gray_low)

-                  {

-                     *dp-- = 0;

-                     *dp-- = 0;

-                  }

-

-                  else

-                  {

-                     *dp-- = 0xff;

-                     *dp-- = 0xff;

-                  }

-

-                  *dp-- = *sp--;

-                  *dp-- = *sp--;

-               }

-            }

-

-            row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;

-            row_info->channels = 2;

-            row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);

-            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,

-               row_width);

-         }

-      }

-      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)

-      {

-         if (row_info->bit_depth == 8)

-         {

-            png_byte red = (png_byte)(trans_color->red & 0xff);

-            png_byte green = (png_byte)(trans_color->green & 0xff);

-            png_byte blue = (png_byte)(trans_color->blue & 0xff);

-            sp = row + (png_size_t)row_info->rowbytes - 1;

-            dp = row + (png_size_t)(row_width << 2) - 1;

-            for (i = 0; i < row_width; i++)

-            {

-               if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)

-                  *dp-- = 0;

-

-               else

-                  *dp-- = 0xff;

-

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-            }

-         }

-         else if (row_info->bit_depth == 16)

-         {

-            png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);

-            png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);

-            png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);

-            png_byte red_low = (png_byte)(trans_color->red & 0xff);

-            png_byte green_low = (png_byte)(trans_color->green & 0xff);

-            png_byte blue_low = (png_byte)(trans_color->blue & 0xff);

-            sp = row + row_info->rowbytes - 1;

-            dp = row + (png_size_t)(row_width << 3) - 1;

-            for (i = 0; i < row_width; i++)

-            {

-               if (*(sp - 5) == red_high &&

-                   *(sp - 4) == red_low &&

-                   *(sp - 3) == green_high &&

-                   *(sp - 2) == green_low &&

-                   *(sp - 1) == blue_high &&

-                   *(sp    ) == blue_low)

-               {

-                  *dp-- = 0;

-                  *dp-- = 0;

-               }

-

-               else

-               {

-                  *dp-- = 0xff;

-                  *dp-- = 0xff;

-               }

-

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-               *dp-- = *sp--;

-            }

-         }

-         row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;

-         row_info->channels = 4;

-         row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);

-         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);

-      }

-   }

-}

-#endif

-

-#ifdef PNG_READ_EXPAND_16_SUPPORTED

-/* If the bit depth is 8 and the color type is not a palette type expand the

- * whole row to 16 bits.  Has no effect otherwise.

- */

-void /* PRIVATE */

-png_do_expand_16(png_row_infop row_info, png_bytep row)

-{

-   if (row_info->bit_depth == 8 &&

-      row_info->color_type != PNG_COLOR_TYPE_PALETTE)

-   {

-      /* The row have a sequence of bytes containing [0..255] and we need

-       * to turn it into another row containing [0..65535], to do this we

-       * calculate:

-       *

-       *  (input / 255) * 65535

-       *

-       *  Which happens to be exactly input * 257 and this can be achieved

-       *  simply by byte replication in place (copying backwards).

-       */

-      png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */

-      png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */

-      while (dp > sp)

-         dp[-2] = dp[-1] = *--sp, dp -= 2;

-

-      row_info->rowbytes *= 2;

-      row_info->bit_depth = 16;

-      row_info->pixel_depth = (png_byte)(row_info->channels * 16);

-   }

-}

-#endif

-

-#ifdef PNG_READ_QUANTIZE_SUPPORTED

-void /* PRIVATE */

-png_do_quantize(png_row_infop row_info, png_bytep row,

-    png_const_bytep palette_lookup, png_const_bytep quantize_lookup)

-{

-   png_bytep sp, dp;

-   png_uint_32 i;

-   png_uint_32 row_width=row_info->width;

-

-   png_debug(1, "in png_do_quantize");

-

-   if (row_info->bit_depth == 8)

-   {

-      if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)

-      {

-         int r, g, b, p;

-         sp = row;

-         dp = row;

-         for (i = 0; i < row_width; i++)

-         {

-            r = *sp++;

-            g = *sp++;

-            b = *sp++;

-

-            /* This looks real messy, but the compiler will reduce

-             * it down to a reasonable formula.  For example, with

-             * 5 bits per color, we get:

-             * p = (((r >> 3) & 0x1f) << 10) |

-             *    (((g >> 3) & 0x1f) << 5) |

-             *    ((b >> 3) & 0x1f);

-             */

-            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &

-                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<

-                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |

-                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &

-                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<

-                (PNG_QUANTIZE_BLUE_BITS)) |

-                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &

-                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

-

-            *dp++ = palette_lookup[p];

-         }

-

-         row_info->color_type = PNG_COLOR_TYPE_PALETTE;

-         row_info->channels = 1;

-         row_info->pixel_depth = row_info->bit_depth;

-         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);

-      }

-

-      else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&

-         palette_lookup != NULL)

-      {

-         int r, g, b, p;

-         sp = row;

-         dp = row;

-         for (i = 0; i < row_width; i++)

-         {

-            r = *sp++;

-            g = *sp++;

-            b = *sp++;

-            sp++;

-

-            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &

-                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<

-                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |

-                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &

-                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<

-                (PNG_QUANTIZE_BLUE_BITS)) |

-                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &

-                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

-

-            *dp++ = palette_lookup[p];

-         }

-

-         row_info->color_type = PNG_COLOR_TYPE_PALETTE;

-         row_info->channels = 1;

-         row_info->pixel_depth = row_info->bit_depth;

-         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);

-      }

-

-      else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&

-         quantize_lookup)

-      {

-         sp = row;

-

-         for (i = 0; i < row_width; i++, sp++)

-         {

-            *sp = quantize_lookup[*sp];

-         }

-      }

-   }

-}

-#endif /* PNG_READ_QUANTIZE_SUPPORTED */

-#endif /* PNG_READ_TRANSFORMS_SUPPORTED */

-

-#ifdef PNG_MNG_FEATURES_SUPPORTED

-/* Undoes intrapixel differencing  */

-void /* PRIVATE */

-png_do_read_intrapixel(png_row_infop row_info, png_bytep row)

-{

-   png_debug(1, "in png_do_read_intrapixel");

-

-   if (

-       (row_info->color_type & PNG_COLOR_MASK_COLOR))

-   {

-      int bytes_per_pixel;

-      png_uint_32 row_width = row_info->width;

-

-      if (row_info->bit_depth == 8)

-      {

-         png_bytep rp;

-         png_uint_32 i;

-

-         if (row_info->color_type == PNG_COLOR_TYPE_RGB)

-            bytes_per_pixel = 3;

-

-         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

-            bytes_per_pixel = 4;

-

-         else

-            return;

-

-         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)

-         {

-            *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);

-            *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);

-         }

-      }

-      else if (row_info->bit_depth == 16)

-      {

-         png_bytep rp;

-         png_uint_32 i;

-

-         if (row_info->color_type == PNG_COLOR_TYPE_RGB)

-            bytes_per_pixel = 6;

-

-         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

-            bytes_per_pixel = 8;

-

-         else

-            return;

-

-         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)

-         {

-            png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);

-            png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);

-            png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);

-            png_uint_32 red  = (s0 + s1 + 65536) & 0xffff;

-            png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;

-            *(rp    ) = (png_byte)((red >> 8) & 0xff);

-            *(rp + 1) = (png_byte)(red & 0xff);

-            *(rp + 4) = (png_byte)((blue >> 8) & 0xff);

-            *(rp + 5) = (png_byte)(blue & 0xff);

-         }

-      }

-   }

-}

-#endif /* PNG_MNG_FEATURES_SUPPORTED */

-#endif /* PNG_READ_SUPPORTED */

+
+/* pngrtran.c - transforms the data in a row for PNG readers
+ *
+ * Last changed in libpng 1.5.7 [December 15, 2011]
+ * Copyright (c) 1998-2011 Glenn Randers-Pehrson
+ * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
+ * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ *
+ * This file contains functions optionally called by an application
+ * in order to tell libpng how to handle data when reading a PNG.
+ * Transformations that are used in both reading and writing are
+ * in pngtrans.c.
+ */
+
+#include "pngpriv.h"
+
+#ifdef PNG_READ_SUPPORTED
+
+/* Set the action on getting a CRC error for an ancillary or critical chunk. */
+void PNGAPI
+png_set_crc_action(png_structp png_ptr, int crit_action, int ancil_action)
+{
+   png_debug(1, "in png_set_crc_action");
+
+   if (png_ptr == NULL)
+      return;
+
+   /* Tell libpng how we react to CRC errors in critical chunks */
+   switch (crit_action)
+   {
+      case PNG_CRC_NO_CHANGE:                        /* Leave setting as is */
+         break;
+
+      case PNG_CRC_WARN_USE:                               /* Warn/use data */
+         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+         png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE;
+         break;
+
+      case PNG_CRC_QUIET_USE:                             /* Quiet/use data */
+         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+         png_ptr->flags |= PNG_FLAG_CRC_CRITICAL_USE |
+                           PNG_FLAG_CRC_CRITICAL_IGNORE;
+         break;
+
+      case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
+         png_warning(png_ptr,
+            "Can't discard critical data on CRC error");
+      case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
+
+      case PNG_CRC_DEFAULT:
+      default:
+         png_ptr->flags &= ~PNG_FLAG_CRC_CRITICAL_MASK;
+         break;
+   }
+
+   /* Tell libpng how we react to CRC errors in ancillary chunks */
+   switch (ancil_action)
+   {
+      case PNG_CRC_NO_CHANGE:                       /* Leave setting as is */
+         break;
+
+      case PNG_CRC_WARN_USE:                              /* Warn/use data */
+         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE;
+         break;
+
+      case PNG_CRC_QUIET_USE:                            /* Quiet/use data */
+         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_USE |
+                           PNG_FLAG_CRC_ANCILLARY_NOWARN;
+         break;
+
+      case PNG_CRC_ERROR_QUIT:                               /* Error/quit */
+         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+         png_ptr->flags |= PNG_FLAG_CRC_ANCILLARY_NOWARN;
+         break;
+
+      case PNG_CRC_WARN_DISCARD:                      /* Warn/discard data */
+
+      case PNG_CRC_DEFAULT:
+      default:
+         png_ptr->flags &= ~PNG_FLAG_CRC_ANCILLARY_MASK;
+         break;
+   }
+}
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+/* Handle alpha and tRNS via a background color */
+void PNGFAPI
+png_set_background_fixed(png_structp png_ptr,
+    png_const_color_16p background_color, int background_gamma_code,
+    int need_expand, png_fixed_point background_gamma)
+{
+   png_debug(1, "in png_set_background_fixed");
+
+   if (png_ptr == NULL)
+      return;
+
+   if (background_gamma_code == PNG_BACKGROUND_GAMMA_UNKNOWN)
+   {
+      png_warning(png_ptr, "Application must supply a known background gamma");
+      return;
+   }
+
+   png_ptr->transformations |= PNG_COMPOSE | PNG_STRIP_ALPHA;
+   png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+   png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+
+   png_memcpy(&(png_ptr->background), background_color,
+      png_sizeof(png_color_16));
+   png_ptr->background_gamma = background_gamma;
+   png_ptr->background_gamma_type = (png_byte)(background_gamma_code);
+   if (need_expand)
+      png_ptr->transformations |= PNG_BACKGROUND_EXPAND;
+   else
+      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+}
+
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_background(png_structp png_ptr,
+    png_const_color_16p background_color, int background_gamma_code,
+    int need_expand, double background_gamma)
+{
+   png_set_background_fixed(png_ptr, background_color, background_gamma_code,
+      need_expand, png_fixed(png_ptr, background_gamma, "png_set_background"));
+}
+#  endif  /* FLOATING_POINT */
+#endif /* READ_BACKGROUND */
+
+/* Scale 16-bit depth files to 8-bit depth.  If both of these are set then the
+ * one that pngrtran does first (scale) happens.  This is necessary to allow the
+ * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
+ */
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+void PNGAPI
+png_set_scale_16(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_scale_16");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_SCALE_16_TO_8;
+}
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+/* Chop 16-bit depth files to 8-bit depth */
+void PNGAPI
+png_set_strip_16(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_strip_16");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_16_TO_8;
+}
+#endif
+
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+void PNGAPI
+png_set_strip_alpha(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_strip_alpha");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_STRIP_ALPHA;
+}
+#endif
+
+#if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
+static png_fixed_point
+translate_gamma_flags(png_structp png_ptr, png_fixed_point output_gamma,
+   int is_screen)
+{
+   /* Check for flag values.  The main reason for having the old Mac value as a
+    * flag is that it is pretty near impossible to work out what the correct
+    * value is from Apple documentation - a working Mac system is needed to
+    * discover the value!
+    */
+   if (output_gamma == PNG_DEFAULT_sRGB ||
+      output_gamma == PNG_FP_1 / PNG_DEFAULT_sRGB)
+   {
+      /* If there is no sRGB support this just sets the gamma to the standard
+       * sRGB value.  (This is a side effect of using this function!)
+       */
+#     ifdef PNG_READ_sRGB_SUPPORTED
+         png_ptr->flags |= PNG_FLAG_ASSUME_sRGB;
+#     endif
+      if (is_screen)
+         output_gamma = PNG_GAMMA_sRGB;
+      else
+         output_gamma = PNG_GAMMA_sRGB_INVERSE;
+   }
+
+   else if (output_gamma == PNG_GAMMA_MAC_18 ||
+      output_gamma == PNG_FP_1 / PNG_GAMMA_MAC_18)
+   {
+      if (is_screen)
+         output_gamma = PNG_GAMMA_MAC_OLD;
+      else
+         output_gamma = PNG_GAMMA_MAC_INVERSE;
+   }
+
+   return output_gamma;
+}
+
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+static png_fixed_point
+convert_gamma_value(png_structp png_ptr, double output_gamma)
+{
+   /* The following silently ignores cases where fixed point (times 100,000)
+    * gamma values are passed to the floating point API.  This is safe and it
+    * means the fixed point constants work just fine with the floating point
+    * API.  The alternative would just lead to undetected errors and spurious
+    * bug reports.  Negative values fail inside the _fixed API unless they
+    * correspond to the flag values.
+    */
+   if (output_gamma > 0 && output_gamma < 128)
+      output_gamma *= PNG_FP_1;
+
+   /* This preserves -1 and -2 exactly: */
+   output_gamma = floor(output_gamma + .5);
+
+   if (output_gamma > PNG_FP_MAX || output_gamma < PNG_FP_MIN)
+      png_fixed_error(png_ptr, "gamma value");
+
+   return (png_fixed_point)output_gamma;
+}
+#  endif
+#endif /* READ_ALPHA_MODE || READ_GAMMA */
+
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+void PNGFAPI
+png_set_alpha_mode_fixed(png_structp png_ptr, int mode,
+   png_fixed_point output_gamma)
+{
+   int compose = 0;
+   png_fixed_point file_gamma;
+
+   png_debug(1, "in png_set_alpha_mode");
+
+   if (png_ptr == NULL)
+      return;
+
+   output_gamma = translate_gamma_flags(png_ptr, output_gamma, 1/*screen*/);
+
+   /* Validate the value to ensure it is in a reasonable range. The value
+    * is expected to be 1 or greater, but this range test allows for some
+    * viewing correction values.  The intent is to weed out users of this API
+    * who use the inverse of the gamma value accidentally!  Since some of these
+    * values are reasonable this may have to be changed.
+    */
+   if (output_gamma < 70000 || output_gamma > 300000)
+      png_error(png_ptr, "output gamma out of expected range");
+
+   /* The default file gamma is the inverse of the output gamma; the output
+    * gamma may be changed below so get the file value first:
+    */
+   file_gamma = png_reciprocal(output_gamma);
+
+   /* There are really 8 possibilities here, composed of any combination
+    * of:
+    *
+    *    premultiply the color channels
+    *    do not encode non-opaque pixels
+    *    encode the alpha as well as the color channels
+    *
+    * The differences disappear if the input/output ('screen') gamma is 1.0,
+    * because then the encoding is a no-op and there is only the choice of
+    * premultiplying the color channels or not.
+    *
+    * png_set_alpha_mode and png_set_background interact because both use
+    * png_compose to do the work.  Calling both is only useful when
+    * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
+    * with a default gamma value.  Otherwise PNG_COMPOSE must not be set.
+    */
+   switch (mode)
+   {
+      case PNG_ALPHA_PNG:        /* default: png standard */
+         /* No compose, but it may be set by png_set_background! */
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         break;
+
+      case PNG_ALPHA_ASSOCIATED: /* color channels premultiplied */
+         compose = 1;
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         /* The output is linear: */
+         output_gamma = PNG_FP_1;
+         break;
+
+      case PNG_ALPHA_OPTIMIZED:  /* associated, non-opaque pixels linear */
+         compose = 1;
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags |= PNG_FLAG_OPTIMIZE_ALPHA;
+         /* output_gamma records the encoding of opaque pixels! */
+         break;
+
+      case PNG_ALPHA_BROKEN:     /* associated, non-linear, alpha encoded */
+         compose = 1;
+         png_ptr->transformations |= PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+         break;
+
+      default:
+         png_error(png_ptr, "invalid alpha mode");
+   }
+
+   /* Only set the default gamma if the file gamma has not been set (this has
+    * the side effect that the gamma in a second call to png_set_alpha_mode will
+    * be ignored.)
+    */
+   if (png_ptr->gamma == 0)
+      png_ptr->gamma = file_gamma;
+
+   /* But always set the output gamma: */
+   png_ptr->screen_gamma = output_gamma;
+
+   /* Finally, if pre-multiplying, set the background fields to achieve the
+    * desired result.
+    */
+   if (compose)
+   {
+      /* And obtain alpha pre-multiplication by composing on black: */
+      png_memset(&png_ptr->background, 0, sizeof png_ptr->background);
+      png_ptr->background_gamma = png_ptr->gamma; /* just in case */
+      png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_FILE;
+      png_ptr->transformations &= ~PNG_BACKGROUND_EXPAND;
+
+      if (png_ptr->transformations & PNG_COMPOSE)
+         png_error(png_ptr,
+            "conflicting calls to set alpha mode and background");
+
+      png_ptr->transformations |= PNG_COMPOSE;
+   }
+
+   /* New API, make sure apps call the correct initializers: */
+   png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
+}
+
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_alpha_mode(png_structp png_ptr, int mode, double output_gamma)
+{
+   png_set_alpha_mode_fixed(png_ptr, mode, convert_gamma_value(png_ptr,
+      output_gamma));
+}
+#  endif
+#endif
+
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+/* Dither file to 8-bit.  Supply a palette, the current number
+ * of elements in the palette, the maximum number of elements
+ * allowed, and a histogram if possible.  If the current number
+ * of colors is greater then the maximum number, the palette will be
+ * modified to fit in the maximum number.  "full_quantize" indicates
+ * whether we need a quantizing cube set up for RGB images, or if we
+ * simply are reducing the number of colors in a paletted image.
+ */
+
+typedef struct png_dsort_struct
+{
+   struct png_dsort_struct FAR * next;
+   png_byte left;
+   png_byte right;
+} png_dsort;
+typedef png_dsort FAR *       png_dsortp;
+typedef png_dsort FAR * FAR * png_dsortpp;
+
+void PNGAPI
+png_set_quantize(png_structp png_ptr, png_colorp palette,
+    int num_palette, int maximum_colors, png_const_uint_16p histogram,
+    int full_quantize)
+{
+   png_debug(1, "in png_set_quantize");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_QUANTIZE;
+
+   if (!full_quantize)
+   {
+      int i;
+
+      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
+          (png_uint_32)(num_palette * png_sizeof(png_byte)));
+      for (i = 0; i < num_palette; i++)
+         png_ptr->quantize_index[i] = (png_byte)i;
+   }
+
+   if (num_palette > maximum_colors)
+   {
+      if (histogram != NULL)
+      {
+         /* This is easy enough, just throw out the least used colors.
+          * Perhaps not the best solution, but good enough.
+          */
+
+         int i;
+
+         /* Initialize an array to sort colors */
+         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
+             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+
+         /* Initialize the quantize_sort array */
+         for (i = 0; i < num_palette; i++)
+            png_ptr->quantize_sort[i] = (png_byte)i;
+
+         /* Find the least used palette entries by starting a
+          * bubble sort, and running it until we have sorted
+          * out enough colors.  Note that we don't care about
+          * sorting all the colors, just finding which are
+          * least used.
+          */
+
+         for (i = num_palette - 1; i >= maximum_colors; i--)
+         {
+            int done; /* To stop early if the list is pre-sorted */
+            int j;
+
+            done = 1;
+            for (j = 0; j < i; j++)
+            {
+               if (histogram[png_ptr->quantize_sort[j]]
+                   < histogram[png_ptr->quantize_sort[j + 1]])
+               {
+                  png_byte t;
+
+                  t = png_ptr->quantize_sort[j];
+                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
+                  png_ptr->quantize_sort[j + 1] = t;
+                  done = 0;
+               }
+            }
+
+            if (done)
+               break;
+         }
+
+         /* Swap the palette around, and set up a table, if necessary */
+         if (full_quantize)
+         {
+            int j = num_palette;
+
+            /* Put all the useful colors within the max, but don't
+             * move the others.
+             */
+            for (i = 0; i < maximum_colors; i++)
+            {
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               {
+                  do
+                     j--;
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
+
+                  palette[i] = palette[j];
+               }
+            }
+         }
+         else
+         {
+            int j = num_palette;
+
+            /* Move all the used colors inside the max limit, and
+             * develop a translation table.
+             */
+            for (i = 0; i < maximum_colors; i++)
+            {
+               /* Only move the colors we need to */
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
+               {
+                  png_color tmp_color;
+
+                  do
+                     j--;
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
+
+                  tmp_color = palette[j];
+                  palette[j] = palette[i];
+                  palette[i] = tmp_color;
+                  /* Indicate where the color went */
+                  png_ptr->quantize_index[j] = (png_byte)i;
+                  png_ptr->quantize_index[i] = (png_byte)j;
+               }
+            }
+
+            /* Find closest color for those colors we are not using */
+            for (i = 0; i < num_palette; i++)
+            {
+               if ((int)png_ptr->quantize_index[i] >= maximum_colors)
+               {
+                  int min_d, k, min_k, d_index;
+
+                  /* Find the closest color to one we threw out */
+                  d_index = png_ptr->quantize_index[i];
+                  min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
+                  for (k = 1, min_k = 0; k < maximum_colors; k++)
+                  {
+                     int d;
+
+                     d = PNG_COLOR_DIST(palette[d_index], palette[k]);
+
+                     if (d < min_d)
+                     {
+                        min_d = d;
+                        min_k = k;
+                     }
+                  }
+                  /* Point to closest color */
+                  png_ptr->quantize_index[i] = (png_byte)min_k;
+               }
+            }
+         }
+         png_free(png_ptr, png_ptr->quantize_sort);
+         png_ptr->quantize_sort = NULL;
+      }
+      else
+      {
+         /* This is much harder to do simply (and quickly).  Perhaps
+          * we need to go through a median cut routine, but those
+          * don't always behave themselves with only a few colors
+          * as input.  So we will just find the closest two colors,
+          * and throw out one of them (chosen somewhat randomly).
+          * [We don't understand this at all, so if someone wants to
+          *  work on improving it, be our guest - AED, GRP]
+          */
+         int i;
+         int max_d;
+         int num_new_palette;
+         png_dsortp t;
+         png_dsortpp hash;
+
+         t = NULL;
+
+         /* Initialize palette index arrays */
+         png_ptr->index_to_palette = (png_bytep)png_malloc(png_ptr,
+             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+         png_ptr->palette_to_index = (png_bytep)png_malloc(png_ptr,
+             (png_uint_32)(num_palette * png_sizeof(png_byte)));
+
+         /* Initialize the sort array */
+         for (i = 0; i < num_palette; i++)
+         {
+            png_ptr->index_to_palette[i] = (png_byte)i;
+            png_ptr->palette_to_index[i] = (png_byte)i;
+         }
+
+         hash = (png_dsortpp)png_calloc(png_ptr, (png_uint_32)(769 *
+             png_sizeof(png_dsortp)));
+
+         num_new_palette = num_palette;
+
+         /* Initial wild guess at how far apart the farthest pixel
+          * pair we will be eliminating will be.  Larger
+          * numbers mean more areas will be allocated, Smaller
+          * numbers run the risk of not saving enough data, and
+          * having to do this all over again.
+          *
+          * I have not done extensive checking on this number.
+          */
+         max_d = 96;
+
+         while (num_new_palette > maximum_colors)
+         {
+            for (i = 0; i < num_new_palette - 1; i++)
+            {
+               int j;
+
+               for (j = i + 1; j < num_new_palette; j++)
+               {
+                  int d;
+
+                  d = PNG_COLOR_DIST(palette[i], palette[j]);
+
+                  if (d <= max_d)
+                  {
+
+                     t = (png_dsortp)png_malloc_warn(png_ptr,
+                         (png_uint_32)(png_sizeof(png_dsort)));
+
+                     if (t == NULL)
+                         break;
+
+                     t->next = hash[d];
+                     t->left = (png_byte)i;
+                     t->right = (png_byte)j;
+                     hash[d] = t;
+                  }
+               }
+               if (t == NULL)
+                  break;
+            }
+
+            if (t != NULL)
+            for (i = 0; i <= max_d; i++)
+            {
+               if (hash[i] != NULL)
+               {
+                  png_dsortp p;
+
+                  for (p = hash[i]; p; p = p->next)
+                  {
+                     if ((int)png_ptr->index_to_palette[p->left]
+                         < num_new_palette &&
+                         (int)png_ptr->index_to_palette[p->right]
+                         < num_new_palette)
+                     {
+                        int j, next_j;
+
+                        if (num_new_palette & 0x01)
+                        {
+                           j = p->left;
+                           next_j = p->right;
+                        }
+                        else
+                        {
+                           j = p->right;
+                           next_j = p->left;
+                        }
+
+                        num_new_palette--;
+                        palette[png_ptr->index_to_palette[j]]
+                            = palette[num_new_palette];
+                        if (!full_quantize)
+                        {
+                           int k;
+
+                           for (k = 0; k < num_palette; k++)
+                           {
+                              if (png_ptr->quantize_index[k] ==
+                                  png_ptr->index_to_palette[j])
+                                 png_ptr->quantize_index[k] =
+                                     png_ptr->index_to_palette[next_j];
+
+                              if ((int)png_ptr->quantize_index[k] ==
+                                  num_new_palette)
+                                 png_ptr->quantize_index[k] =
+                                     png_ptr->index_to_palette[j];
+                           }
+                        }
+
+                        png_ptr->index_to_palette[png_ptr->palette_to_index
+                            [num_new_palette]] = png_ptr->index_to_palette[j];
+
+                        png_ptr->palette_to_index[png_ptr->index_to_palette[j]]
+                            = png_ptr->palette_to_index[num_new_palette];
+
+                        png_ptr->index_to_palette[j] =
+                            (png_byte)num_new_palette;
+
+                        png_ptr->palette_to_index[num_new_palette] =
+                            (png_byte)j;
+                     }
+                     if (num_new_palette <= maximum_colors)
+                        break;
+                  }
+                  if (num_new_palette <= maximum_colors)
+                     break;
+               }
+            }
+
+            for (i = 0; i < 769; i++)
+            {
+               if (hash[i] != NULL)
+               {
+                  png_dsortp p = hash[i];
+                  while (p)
+                  {
+                     t = p->next;
+                     png_free(png_ptr, p);
+                     p = t;
+                  }
+               }
+               hash[i] = 0;
+            }
+            max_d += 96;
+         }
+         png_free(png_ptr, hash);
+         png_free(png_ptr, png_ptr->palette_to_index);
+         png_free(png_ptr, png_ptr->index_to_palette);
+         png_ptr->palette_to_index = NULL;
+         png_ptr->index_to_palette = NULL;
+      }
+      num_palette = maximum_colors;
+   }
+   if (png_ptr->palette == NULL)
+   {
+      png_ptr->palette = palette;
+   }
+   png_ptr->num_palette = (png_uint_16)num_palette;
+
+   if (full_quantize)
+   {
+      int i;
+      png_bytep distance;
+      int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
+          PNG_QUANTIZE_BLUE_BITS;
+      int num_red = (1 << PNG_QUANTIZE_RED_BITS);
+      int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
+      int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
+      png_size_t num_entries = ((png_size_t)1 << total_bits);
+
+      png_ptr->palette_lookup = (png_bytep)png_calloc(png_ptr,
+          (png_uint_32)(num_entries * png_sizeof(png_byte)));
+
+      distance = (png_bytep)png_malloc(png_ptr, (png_uint_32)(num_entries *
+          png_sizeof(png_byte)));
+
+      png_memset(distance, 0xff, num_entries * png_sizeof(png_byte));
+
+      for (i = 0; i < num_palette; i++)
+      {
+         int ir, ig, ib;
+         int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
+         int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
+         int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
+
+         for (ir = 0; ir < num_red; ir++)
+         {
+            /* int dr = abs(ir - r); */
+            int dr = ((ir > r) ? ir - r : r - ir);
+            int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
+                PNG_QUANTIZE_GREEN_BITS));
+
+            for (ig = 0; ig < num_green; ig++)
+            {
+               /* int dg = abs(ig - g); */
+               int dg = ((ig > g) ? ig - g : g - ig);
+               int dt = dr + dg;
+               int dm = ((dr > dg) ? dr : dg);
+               int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
+
+               for (ib = 0; ib < num_blue; ib++)
+               {
+                  int d_index = index_g | ib;
+                  /* int db = abs(ib - b); */
+                  int db = ((ib > b) ? ib - b : b - ib);
+                  int dmax = ((dm > db) ? dm : db);
+                  int d = dmax + dt + db;
+
+                  if (d < (int)distance[d_index])
+                  {
+                     distance[d_index] = (png_byte)d;
+                     png_ptr->palette_lookup[d_index] = (png_byte)i;
+                  }
+               }
+            }
+         }
+      }
+
+      png_free(png_ptr, distance);
+   }
+}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+void PNGFAPI
+png_set_gamma_fixed(png_structp png_ptr, png_fixed_point scrn_gamma,
+   png_fixed_point file_gamma)
+{
+   png_debug(1, "in png_set_gamma_fixed");
+
+   if (png_ptr == NULL)
+      return;
+
+   /* New in libpng-1.5.4 - reserve particular negative values as flags. */
+   scrn_gamma = translate_gamma_flags(png_ptr, scrn_gamma, 1/*screen*/);
+   file_gamma = translate_gamma_flags(png_ptr, file_gamma, 0/*file*/);
+
+#if PNG_LIBPNG_VER >= 10600
+   /* Checking the gamma values for being >0 was added in 1.5.4 along with the
+    * premultiplied alpha support; this actually hides an undocumented feature
+    * of the previous implementation which allowed gamma processing to be
+    * disabled in background handling.  There is no evidence (so far) that this
+    * was being used; however, png_set_background itself accepted and must still
+    * accept '0' for the gamma value it takes, because it isn't always used.
+    *
+    * Since this is an API change (albeit a very minor one that removes an
+    * undocumented API feature) it will not be made until libpng-1.6.0.
+    */
+   if (file_gamma <= 0)
+      png_error(png_ptr, "invalid file gamma in png_set_gamma");
+
+   if (scrn_gamma <= 0)
+      png_error(png_ptr, "invalid screen gamma in png_set_gamma");
+#endif
+
+   /* Set the gamma values unconditionally - this overrides the value in the PNG
+    * file if a gAMA chunk was present.  png_set_alpha_mode provides a
+    * different, easier, way to default the file gamma.
+    */
+   png_ptr->gamma = file_gamma;
+   png_ptr->screen_gamma = scrn_gamma;
+}
+
+#  ifdef PNG_FLOATING_POINT_SUPPORTED
+void PNGAPI
+png_set_gamma(png_structp png_ptr, double scrn_gamma, double file_gamma)
+{
+   png_set_gamma_fixed(png_ptr, convert_gamma_value(png_ptr, scrn_gamma),
+      convert_gamma_value(png_ptr, file_gamma));
+}
+#  endif /* FLOATING_POINT_SUPPORTED */
+#endif /* READ_GAMMA */
+
+#ifdef PNG_READ_EXPAND_SUPPORTED
+/* Expand paletted images to RGB, expand grayscale images of
+ * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
+ * to alpha channels.
+ */
+void PNGAPI
+png_set_expand(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_expand");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+
+/* GRR 19990627:  the following three functions currently are identical
+ *  to png_set_expand().  However, it is entirely reasonable that someone
+ *  might wish to expand an indexed image to RGB but *not* expand a single,
+ *  fully transparent palette entry to a full alpha channel--perhaps instead
+ *  convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
+ *  the transparent color with a particular RGB value, or drop tRNS entirely.
+ *  IOW, a future version of the library may make the transformations flag
+ *  a bit more fine-grained, with separate bits for each of these three
+ *  functions.
+ *
+ *  More to the point, these functions make it obvious what libpng will be
+ *  doing, whereas "expand" can (and does) mean any number of things.
+ *
+ *  GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
+ *  to expand only the sample depth but not to expand the tRNS to alpha
+ *  and its name was changed to png_set_expand_gray_1_2_4_to_8().
+ */
+
+/* Expand paletted images to RGB. */
+void PNGAPI
+png_set_palette_to_rgb(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_palette_to_rgb");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+
+/* Expand grayscale images of less than 8-bit depth to 8 bits. */
+void PNGAPI
+png_set_expand_gray_1_2_4_to_8(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= PNG_EXPAND;
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+
+
+
+/* Expand tRNS chunks to alpha channels. */
+void PNGAPI
+png_set_tRNS_to_alpha(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_tRNS_to_alpha");
+
+   png_ptr->transformations |= (PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+}
+#endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
+
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
+ * it may not work correctly.)
+ */
+void PNGAPI
+png_set_expand_16(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_expand_16");
+
+   if (png_ptr == NULL)
+      return;
+
+   png_ptr->transformations |= (PNG_EXPAND_16 | PNG_EXPAND | PNG_EXPAND_tRNS);
+   png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+
+   /* New API, make sure apps call the correct initializers: */
+   png_ptr->flags |= PNG_FLAG_DETECT_UNINITIALIZED;
+}
+#endif
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+void PNGAPI
+png_set_gray_to_rgb(png_structp png_ptr)
+{
+   png_debug(1, "in png_set_gray_to_rgb");
+
+   if (png_ptr != NULL)
+   {
+      /* Because rgb must be 8 bits or more: */
+      png_set_expand_gray_1_2_4_to_8(png_ptr);
+      png_ptr->transformations |= PNG_GRAY_TO_RGB;
+      png_ptr->flags &= ~PNG_FLAG_ROW_INIT;
+   }
+}
+#endif
+
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+void PNGFAPI
+png_set_rgb_to_gray_fixed(png_structp png_ptr, int error_action,
+    png_fixed_point red, png_fixed_point green)
+{
+   png_debug(1, "in png_set_rgb_to_gray");
+
+   if (png_ptr == NULL)
+      return;
+
+   switch(error_action)
+   {
+      case PNG_ERROR_ACTION_NONE:
+         png_ptr->transformations |= PNG_RGB_TO_GRAY;
+         break;
+
+      case PNG_ERROR_ACTION_WARN:
+         png_ptr->transformations |= PNG_RGB_TO_GRAY_WARN;
+         break;
+
+      case PNG_ERROR_ACTION_ERROR:
+         png_ptr->transformations |= PNG_RGB_TO_GRAY_ERR;
+         break;
+
+      default:
+         png_error(png_ptr, "invalid error action to rgb_to_gray");
+         break;
+   }
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+#ifdef PNG_READ_EXPAND_SUPPORTED
+      png_ptr->transformations |= PNG_EXPAND;
+#else
+   {
+      png_warning(png_ptr,
+        "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
+
+      png_ptr->transformations &= ~PNG_RGB_TO_GRAY;
+   }
+#endif
+   {
+      if (red >= 0 && green >= 0 && red + green <= PNG_FP_1)
+      {
+         png_uint_16 red_int, green_int;
+
+         /* NOTE: this calculation does not round, but this behavior is retained
+          * for consistency, the inaccuracy is very small.  The code here always
+          * overwrites the coefficients, regardless of whether they have been
+          * defaulted or set already.
+          */
+         red_int = (png_uint_16)(((png_uint_32)red*32768)/100000);
+         green_int = (png_uint_16)(((png_uint_32)green*32768)/100000);
+
+         png_ptr->rgb_to_gray_red_coeff   = red_int;
+         png_ptr->rgb_to_gray_green_coeff = green_int;
+         png_ptr->rgb_to_gray_coefficients_set = 1;
+      }
+
+      else
+      {
+         if (red >= 0 && green >= 0)
+            png_warning(png_ptr,
+               "ignoring out of range rgb_to_gray coefficients");
+
+         /* Use the defaults, from the cHRM chunk if set, else the historical
+          * values which are close to the sRGB/HDTV/ITU-Rec 709 values.  See
+          * png_do_rgb_to_gray for more discussion of the values.  In this case
+          * the coefficients are not marked as 'set' and are not overwritten if
+          * something has already provided a default.
+          */
+         if (png_ptr->rgb_to_gray_red_coeff == 0 &&
+            png_ptr->rgb_to_gray_green_coeff == 0)
+         {
+            png_ptr->rgb_to_gray_red_coeff   = 6968;
+            png_ptr->rgb_to_gray_green_coeff = 23434;
+            /* png_ptr->rgb_to_gray_blue_coeff  = 2366; */
+         }
+      }
+   }
+}
+
+#ifdef PNG_FLOATING_POINT_SUPPORTED
+/* Convert a RGB image to a grayscale of the same width.  This allows us,
+ * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
+ */
+
+void PNGAPI
+png_set_rgb_to_gray(png_structp png_ptr, int error_action, double red,
+   double green)
+{
+   if (png_ptr == NULL)
+      return;
+
+   png_set_rgb_to_gray_fixed(png_ptr, error_action,
+      png_fixed(png_ptr, red, "rgb to gray red coefficient"),
+      png_fixed(png_ptr, green, "rgb to gray green coefficient"));
+}
+#endif /* FLOATING POINT */
+
+#endif
+
+#if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
+    defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
+void PNGAPI
+png_set_read_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
+    read_user_transform_fn)
+{
+   png_debug(1, "in png_set_read_user_transform_fn");
+
+   if (png_ptr == NULL)
+      return;
+
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+   png_ptr->transformations |= PNG_USER_TRANSFORM;
+   png_ptr->read_user_transform_fn = read_user_transform_fn;
+#endif
+}
+#endif
+
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* In the case of gamma transformations only do transformations on images where
+ * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
+ * slows things down slightly, and also needlessly introduces small errors.
+ */
+static int /* PRIVATE */
+png_gamma_threshold(png_fixed_point screen_gamma, png_fixed_point file_gamma)
+{
+   /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
+    * correction as a difference of the overall transform from 1.0
+    *
+    * We want to compare the threshold with s*f - 1, if we get
+    * overflow here it is because of wacky gamma values so we
+    * turn on processing anyway.
+    */
+   png_fixed_point gtest;
+   return !png_muldiv(&gtest, screen_gamma, file_gamma, PNG_FP_1) ||
+       png_gamma_significant(gtest);
+}
+#endif
+
+/* Initialize everything needed for the read.  This includes modifying
+ * the palette.
+ */
+
+/*For the moment 'png_init_palette_transformations' and
+ * 'png_init_rgb_transformations' only do some flag canceling optimizations.
+ * The intent is that these two routines should have palette or rgb operations
+ * extracted from 'png_init_read_transformations'.
+ */
+static void /* PRIVATE */
+png_init_palette_transformations(png_structp png_ptr)
+{
+   /* Called to handle the (input) palette case.  In png_do_read_transformations
+    * the first step is to expand the palette if requested, so this code must
+    * take care to only make changes that are invariant with respect to the
+    * palette expansion, or only do them if there is no expansion.
+    *
+    * STRIP_ALPHA has already been handled in the caller (by setting num_trans
+    * to 0.)
+    */
+   int input_has_alpha = 0;
+   int input_has_transparency = 0;
+
+   if (png_ptr->num_trans > 0)
+   {
+      int i;
+
+      /* Ignore if all the entries are opaque (unlikely!) */
+      for (i=0; i<png_ptr->num_trans; ++i)
+         if (png_ptr->trans_alpha[i] == 255)
+            continue;
+         else if (png_ptr->trans_alpha[i] == 0)
+            input_has_transparency = 1;
+         else
+            input_has_alpha = 1;
+   }
+
+   /* If no alpha we can optimize. */
+   if (!input_has_alpha)
+   {
+      /* Any alpha means background and associative alpha processing is
+       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
+       * and ENCODE_ALPHA are irrelevant.
+       */
+      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+
+      if (!input_has_transparency)
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+   }
+
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+   /* png_set_background handling - deals with the complexity of whether the
+    * background color is in the file format or the screen format in the case
+    * where an 'expand' will happen.
+    */
+
+   /* The following code cannot be entered in the alpha pre-multiplication case
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
+    */
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       (png_ptr->transformations & PNG_EXPAND))
+   {
+      {
+         png_ptr->background.red   =
+             png_ptr->palette[png_ptr->background.index].red;
+         png_ptr->background.green =
+             png_ptr->palette[png_ptr->background.index].green;
+         png_ptr->background.blue  =
+             png_ptr->palette[png_ptr->background.index].blue;
+
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+        if (png_ptr->transformations & PNG_INVERT_ALPHA)
+        {
+           if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+           {
+              /* Invert the alpha channel (in tRNS) unless the pixels are
+               * going to be expanded, in which case leave it for later
+               */
+              int i, istop = png_ptr->num_trans;
+
+              for (i=0; i<istop; i++)
+                 png_ptr->trans_alpha[i] = (png_byte)(255 -
+                    png_ptr->trans_alpha[i]);
+           }
+        }
+#endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
+      }
+   } /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+
+static void /* PRIVATE */
+png_init_rgb_transformations(png_structp png_ptr)
+{
+   /* Added to libpng-1.5.4: check the color type to determine whether there
+    * is any alpha or transparency in the image and simply cancel the
+    * background and alpha mode stuff if there isn't.
+    */
+   int input_has_alpha = (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+   int input_has_transparency = png_ptr->num_trans > 0;
+
+   /* If no alpha we can optimize. */
+   if (!input_has_alpha)
+   {
+      /* Any alpha means background and associative alpha processing is
+       * required, however if the alpha is 0 or 1 throughout OPTIIMIZE_ALPHA
+       * and ENCODE_ALPHA are irrelevant.
+       */
+#     ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+         png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+         png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+#     endif
+
+      if (!input_has_transparency)
+         png_ptr->transformations &= ~(PNG_COMPOSE | PNG_BACKGROUND_EXPAND);
+   }
+
+#if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
+   /* png_set_background handling - deals with the complexity of whether the
+    * background color is in the file format or the screen format in the case
+    * where an 'expand' will happen.
+    */
+
+   /* The following code cannot be entered in the alpha pre-multiplication case
+    * because PNG_BACKGROUND_EXPAND is cancelled below.
+    */
+   if ((png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+       (png_ptr->transformations & PNG_EXPAND) &&
+       !(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+       /* i.e., GRAY or GRAY_ALPHA */
+   {
+      {
+         /* Expand background and tRNS chunks */
+         int gray = png_ptr->background.gray;
+         int trans_gray = png_ptr->trans_color.gray;
+
+         switch (png_ptr->bit_depth)
+         {
+            case 1:
+               gray *= 0xff;
+               trans_gray *= 0xff;
+               break;
+
+            case 2:
+               gray *= 0x55;
+               trans_gray *= 0x55;
+               break;
+
+            case 4:
+               gray *= 0x11;
+               trans_gray *= 0x11;
+               break;
+
+            default:
+
+            case 8:
+               /* Already 8 bits, fall through */
+
+            case 16:
+               /* Already a full 16 bits */
+               break;
+         }
+
+         png_ptr->background.red = png_ptr->background.green =
+            png_ptr->background.blue = (png_uint_16)gray;
+
+         if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+         {
+            png_ptr->trans_color.red = png_ptr->trans_color.green =
+               png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+         }
+      }
+   } /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+
+void /* PRIVATE */
+png_init_read_transformations(png_structp png_ptr)
+{
+   png_debug(1, "in png_init_read_transformations");
+
+   /* This internal function is called from png_read_start_row in pngrutil.c
+    * and it is called before the 'rowbytes' calculation is done, so the code
+    * in here can change or update the transformations flags.
+    *
+    * First do updates that do not depend on the details of the PNG image data
+    * being processed.
+    */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
+    * png_set_alpha_mode and this is another source for a default file gamma so
+    * the test needs to be performed later - here.  In addition prior to 1.5.4
+    * the tests were repeated for the PALETTE color type here - this is no
+    * longer necessary (and doesn't seem to have been necessary before.)
+    */
+   {
+      /* The following temporary indicates if overall gamma correction is
+       * required.
+       */
+      int gamma_correction = 0;
+
+      if (png_ptr->gamma != 0) /* has been set */
+      {
+         if (png_ptr->screen_gamma != 0) /* screen set too */
+            gamma_correction = png_gamma_threshold(png_ptr->gamma,
+               png_ptr->screen_gamma);
+
+         else
+            /* Assume the output matches the input; a long time default behavior
+             * of libpng, although the standard has nothing to say about this.
+             */
+            png_ptr->screen_gamma = png_reciprocal(png_ptr->gamma);
+      }
+
+      else if (png_ptr->screen_gamma != 0)
+         /* The converse - assume the file matches the screen, note that this
+          * perhaps undesireable default can (from 1.5.4) be changed by calling
+          * png_set_alpha_mode (even if the alpha handling mode isn't required
+          * or isn't changed from the default.)
+          */
+         png_ptr->gamma = png_reciprocal(png_ptr->screen_gamma);
+
+      else /* neither are set */
+         /* Just in case the following prevents any processing - file and screen
+          * are both assumed to be linear and there is no way to introduce a
+          * third gamma value other than png_set_background with 'UNIQUE', and,
+          * prior to 1.5.4
+          */
+         png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;
+
+      /* Now turn the gamma transformation on or off as appropriate.  Notice
+       * that PNG_GAMMA just refers to the file->screen correction.  Alpha
+       * composition may independently cause gamma correction because it needs
+       * linear data (e.g. if the file has a gAMA chunk but the screen gamma
+       * hasn't been specified.)  In any case this flag may get turned off in
+       * the code immediately below if the transform can be handled outside the
+       * row loop.
+       */
+      if (gamma_correction)
+         png_ptr->transformations |= PNG_GAMMA;
+
+      else
+         png_ptr->transformations &= ~PNG_GAMMA;
+   }
+#endif
+
+   /* Certain transformations have the effect of preventing other
+    * transformations that happen afterward in png_do_read_transformations,
+    * resolve the interdependencies here.  From the code of
+    * png_do_read_transformations the order is:
+    *
+    *  1) PNG_EXPAND (including PNG_EXPAND_tRNS)
+    *  2) PNG_STRIP_ALPHA (if no compose)
+    *  3) PNG_RGB_TO_GRAY
+    *  4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
+    *  5) PNG_COMPOSE
+    *  6) PNG_GAMMA
+    *  7) PNG_STRIP_ALPHA (if compose)
+    *  8) PNG_ENCODE_ALPHA
+    *  9) PNG_SCALE_16_TO_8
+    * 10) PNG_16_TO_8
+    * 11) PNG_QUANTIZE (converts to palette)
+    * 12) PNG_EXPAND_16
+    * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
+    * 14) PNG_INVERT_MONO
+    * 15) PNG_SHIFT
+    * 16) PNG_PACK
+    * 17) PNG_BGR
+    * 18) PNG_PACKSWAP
+    * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
+    * 20) PNG_INVERT_ALPHA
+    * 21) PNG_SWAP_ALPHA
+    * 22) PNG_SWAP_BYTES
+    * 23) PNG_USER_TRANSFORM [must be last]
+    */
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      !(png_ptr->transformations & PNG_COMPOSE))
+   {
+      /* Stripping the alpha channel happens immediately after the 'expand'
+       * transformations, before all other transformation, so it cancels out
+       * the alpha handling.  It has the side effect negating the effect of
+       * PNG_EXPAND_tRNS too:
+       */
+      png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
+         PNG_EXPAND_tRNS);
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+
+      /* Kill the tRNS chunk itself too.  Prior to 1.5.4 this did not happen
+       * so transparency information would remain just so long as it wasn't
+       * expanded.  This produces unexpected API changes if the set of things
+       * that do PNG_EXPAND_tRNS changes (perfectly possible given the
+       * documentation - which says ask for what you want, accept what you
+       * get.)  This makes the behavior consistent from 1.5.4:
+       */
+      png_ptr->num_trans = 0;
+   }
+#endif /* STRIP_ALPHA supported, no COMPOSE */
+
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+   /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
+    * settings will have no effect.
+    */
+   if (!png_gamma_significant(png_ptr->screen_gamma))
+   {
+      png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+      png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+   }
+#endif
+
+#if defined(PNG_READ_EXPAND_SUPPORTED) && \
+   defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+   defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+   /* Detect gray background and attempt to enable optimization for
+    * gray --> RGB case.
+    *
+    * Note:  if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
+    * RGB_ALPHA (in which case need_expand is superfluous anyway), the
+    * background color might actually be gray yet not be flagged as such.
+    * This is not a problem for the current code, which uses
+    * PNG_BACKGROUND_IS_GRAY only to decide when to do the
+    * png_do_gray_to_rgb() transformation.
+    *
+    * TODO: this code needs to be revised to avoid the complexity and
+    * interdependencies.  The color type of the background should be recorded in
+    * png_set_background, along with the bit depth, then the code has a record
+    * of exactly what color space the background is currently in.
+    */
+   if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
+   {
+      /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
+       * the file was grayscale the background value is gray.
+       */
+      if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+         png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+   }
+
+   else if (png_ptr->transformations & PNG_COMPOSE)
+   {
+      /* PNG_COMPOSE: png_set_background was called with need_expand false,
+       * so the color is in the color space of the output or png_set_alpha_mode
+       * was called and the color is black.  Ignore RGB_TO_GRAY because that
+       * happens before GRAY_TO_RGB.
+       */
+      if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+      {
+         if (png_ptr->background.red == png_ptr->background.green &&
+             png_ptr->background.red == png_ptr->background.blue)
+         {
+            png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+            png_ptr->background.gray = png_ptr->background.red;
+         }
+      }
+   }
+#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED (etc) */
+
+   /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
+    * can be performed directly on the palette, and some (such as rgb to gray)
+    * can be optimized inside the palette.  This is particularly true of the
+    * composite (background and alpha) stuff, which can be pretty much all done
+    * in the palette even if the result is expanded to RGB or gray afterward.
+    *
+    * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
+    * earlier and the palette stuff is actually handled on the first row.  This
+    * leads to the reported bug that the palette returned by png_get_PLTE is not
+    * updated.
+    */
+   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      png_init_palette_transformations(png_ptr);
+
+   else
+      png_init_rgb_transformations(png_ptr);
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+   defined(PNG_READ_EXPAND_16_SUPPORTED)
+   if ((png_ptr->transformations & PNG_EXPAND_16) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+      png_ptr->bit_depth != 16)
+   {
+      /* TODO: fix this.  Because the expand_16 operation is after the compose
+       * handling the background color must be 8, not 16, bits deep, but the
+       * application will supply a 16-bit value so reduce it here.
+       *
+       * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
+       * present, so that case is ok (until do_expand_16 is moved.)
+       *
+       * NOTE: this discards the low 16 bits of the user supplied background
+       * color, but until expand_16 works properly there is no choice!
+       */
+#     define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
+      CHOP(png_ptr->background.red);
+      CHOP(png_ptr->background.green);
+      CHOP(png_ptr->background.blue);
+      CHOP(png_ptr->background.gray);
+#     undef CHOP
+   }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+   (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
+   defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
+   if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+      png_ptr->bit_depth == 16)
+   {
+      /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
+       * component this will also happen after PNG_COMPOSE and so the background
+       * color must be pre-expanded here.
+       *
+       * TODO: fix this too.
+       */
+      png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
+      png_ptr->background.green =
+         (png_uint_16)(png_ptr->background.green * 257);
+      png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
+      png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
+   }
+#endif
+
+   /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
+    * background support (see the comments in scripts/pnglibconf.dfa), this
+    * allows pre-multiplication of the alpha channel to be implemented as
+    * compositing on black.  This is probably sub-optimal and has been done in
+    * 1.5.4 betas simply to enable external critique and testing (i.e. to
+    * implement the new API quickly, without lots of internal changes.)
+    */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+      /* Includes ALPHA_MODE */
+      png_ptr->background_1 = png_ptr->background;
+#  endif
+
+   /* This needs to change - in the palette image case a whole set of tables are
+    * built when it would be quicker to just calculate the correct value for
+    * each palette entry directly.  Also, the test is too tricky - why check
+    * PNG_RGB_TO_GRAY if PNG_GAMMA is not set?  The answer seems to be that
+    * PNG_GAMMA is cancelled even if the gamma is known?  The test excludes the
+    * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
+    * the gamma tables will not be built even if composition is required on a
+    * gamma encoded value.
+    *
+    * In 1.5.4 this is addressed below by an additional check on the individual
+    * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
+    * tables.
+    */
+   if ((png_ptr->transformations & PNG_GAMMA)
+      || ((png_ptr->transformations & PNG_RGB_TO_GRAY)
+         && (png_gamma_significant(png_ptr->gamma) ||
+            png_gamma_significant(png_ptr->screen_gamma)))
+      || ((png_ptr->transformations & PNG_COMPOSE)
+         && (png_gamma_significant(png_ptr->gamma)
+            || png_gamma_significant(png_ptr->screen_gamma)
+#  ifdef PNG_READ_BACKGROUND_SUPPORTED
+            || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
+               && png_gamma_significant(png_ptr->background_gamma))
+#  endif
+      )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
+         && png_gamma_significant(png_ptr->screen_gamma))
+      )
+   {
+      png_build_gamma_table(png_ptr, png_ptr->bit_depth);
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+      if (png_ptr->transformations & PNG_COMPOSE)
+      {
+         /* Issue a warning about this combination: because RGB_TO_GRAY is
+          * optimized to do the gamma transform if present yet do_background has
+          * to do the same thing if both options are set a
+          * double-gamma-correction happens.  This is true in all versions of
+          * libpng to date.
+          */
+         if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+            png_warning(png_ptr,
+               "libpng does not support gamma+background+rgb_to_gray");
+
+         if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+         {
+            /* We don't get to here unless there is a tRNS chunk with non-opaque
+             * entries - see the checking code at the start of this function.
+             */
+            png_color back, back_1;
+            png_colorp palette = png_ptr->palette;
+            int num_palette = png_ptr->num_palette;
+            int i;
+            if (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_FILE)
+            {
+
+               back.red = png_ptr->gamma_table[png_ptr->background.red];
+               back.green = png_ptr->gamma_table[png_ptr->background.green];
+               back.blue = png_ptr->gamma_table[png_ptr->background.blue];
+
+               back_1.red = png_ptr->gamma_to_1[png_ptr->background.red];
+               back_1.green = png_ptr->gamma_to_1[png_ptr->background.green];
+               back_1.blue = png_ptr->gamma_to_1[png_ptr->background.blue];
+            }
+            else
+            {
+               png_fixed_point g, gs;
+
+               switch (png_ptr->background_gamma_type)
+               {
+                  case PNG_BACKGROUND_GAMMA_SCREEN:
+                     g = (png_ptr->screen_gamma);
+                     gs = PNG_FP_1;
+                     break;
+
+                  case PNG_BACKGROUND_GAMMA_FILE:
+                     g = png_reciprocal(png_ptr->gamma);
+                     gs = png_reciprocal2(png_ptr->gamma,
+                        png_ptr->screen_gamma);
+                     break;
+
+                  case PNG_BACKGROUND_GAMMA_UNIQUE:
+                     g = png_reciprocal(png_ptr->background_gamma);
+                     gs = png_reciprocal2(png_ptr->background_gamma,
+                        png_ptr->screen_gamma);
+                     break;
+                  default:
+                     g = PNG_FP_1;    /* back_1 */
+                     gs = PNG_FP_1;   /* back */
+                     break;
+               }
+
+               if (png_gamma_significant(gs))
+               {
+                  back.red = png_gamma_8bit_correct(png_ptr->background.red,
+                      gs);
+                  back.green = png_gamma_8bit_correct(png_ptr->background.green,
+                      gs);
+                  back.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+                      gs);
+               }
+
+               else
+               {
+                  back.red   = (png_byte)png_ptr->background.red;
+                  back.green = (png_byte)png_ptr->background.green;
+                  back.blue  = (png_byte)png_ptr->background.blue;
+               }
+
+               if (png_gamma_significant(g))
+               {
+                  back_1.red = png_gamma_8bit_correct(png_ptr->background.red,
+                     g);
+                  back_1.green = png_gamma_8bit_correct(
+                     png_ptr->background.green, g);
+                  back_1.blue = png_gamma_8bit_correct(png_ptr->background.blue,
+                     g);
+               }
+
+               else
+               {
+                  back_1.red   = (png_byte)png_ptr->background.red;
+                  back_1.green = (png_byte)png_ptr->background.green;
+                  back_1.blue  = (png_byte)png_ptr->background.blue;
+               }
+            }
+
+            for (i = 0; i < num_palette; i++)
+            {
+               if (i < (int)png_ptr->num_trans &&
+                   png_ptr->trans_alpha[i] != 0xff)
+               {
+                  if (png_ptr->trans_alpha[i] == 0)
+                  {
+                     palette[i] = back;
+                  }
+                  else /* if (png_ptr->trans_alpha[i] != 0xff) */
+                  {
+                     png_byte v, w;
+
+                     v = png_ptr->gamma_to_1[palette[i].red];
+                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.red);
+                     palette[i].red = png_ptr->gamma_from_1[w];
+
+                     v = png_ptr->gamma_to_1[palette[i].green];
+                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.green);
+                     palette[i].green = png_ptr->gamma_from_1[w];
+
+                     v = png_ptr->gamma_to_1[palette[i].blue];
+                     png_composite(w, v, png_ptr->trans_alpha[i], back_1.blue);
+                     palette[i].blue = png_ptr->gamma_from_1[w];
+                  }
+               }
+               else
+               {
+                  palette[i].red = png_ptr->gamma_table[palette[i].red];
+                  palette[i].green = png_ptr->gamma_table[palette[i].green];
+                  palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+               }
+            }
+
+            /* Prevent the transformations being done again.
+             *
+             * NOTE: this is highly dubious; it removes the transformations in
+             * place.  This seems inconsistent with the general treatment of the
+             * transformations elsewhere.
+             */
+            png_ptr->transformations &= ~(PNG_COMPOSE | PNG_GAMMA);
+         } /* color_type == PNG_COLOR_TYPE_PALETTE */
+
+         /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
+         else /* color_type != PNG_COLOR_TYPE_PALETTE */
+         {
+            int gs_sig, g_sig;
+            png_fixed_point g = PNG_FP_1;  /* Correction to linear */
+            png_fixed_point gs = PNG_FP_1; /* Correction to screen */
+
+            switch (png_ptr->background_gamma_type)
+            {
+               case PNG_BACKGROUND_GAMMA_SCREEN:
+                  g = png_ptr->screen_gamma;
+                  /* gs = PNG_FP_1; */
+                  break;
+
+               case PNG_BACKGROUND_GAMMA_FILE:
+                  g = png_reciprocal(png_ptr->gamma);
+                  gs = png_reciprocal2(png_ptr->gamma, png_ptr->screen_gamma);
+                  break;
+
+               case PNG_BACKGROUND_GAMMA_UNIQUE:
+                  g = png_reciprocal(png_ptr->background_gamma);
+                  gs = png_reciprocal2(png_ptr->background_gamma,
+                      png_ptr->screen_gamma);
+                  break;
+
+               default:
+                  png_error(png_ptr, "invalid background gamma type");
+            }
+
+            g_sig = png_gamma_significant(g);
+            gs_sig = png_gamma_significant(gs);
+
+            if (g_sig)
+               png_ptr->background_1.gray = png_gamma_correct(png_ptr,
+                   png_ptr->background.gray, g);
+
+            if (gs_sig)
+               png_ptr->background.gray = png_gamma_correct(png_ptr,
+                   png_ptr->background.gray, gs);
+
+            if ((png_ptr->background.red != png_ptr->background.green) ||
+                (png_ptr->background.red != png_ptr->background.blue) ||
+                (png_ptr->background.red != png_ptr->background.gray))
+            {
+               /* RGB or RGBA with color background */
+               if (g_sig)
+               {
+                  png_ptr->background_1.red = png_gamma_correct(png_ptr,
+                      png_ptr->background.red, g);
+
+                  png_ptr->background_1.green = png_gamma_correct(png_ptr,
+                      png_ptr->background.green, g);
+
+                  png_ptr->background_1.blue = png_gamma_correct(png_ptr,
+                      png_ptr->background.blue, g);
+               }
+
+               if (gs_sig)
+               {
+                  png_ptr->background.red = png_gamma_correct(png_ptr,
+                      png_ptr->background.red, gs);
+
+                  png_ptr->background.green = png_gamma_correct(png_ptr,
+                      png_ptr->background.green, gs);
+
+                  png_ptr->background.blue = png_gamma_correct(png_ptr,
+                      png_ptr->background.blue, gs);
+               }
+            }
+
+            else
+            {
+               /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
+               png_ptr->background_1.red = png_ptr->background_1.green
+                   = png_ptr->background_1.blue = png_ptr->background_1.gray;
+
+               png_ptr->background.red = png_ptr->background.green
+                   = png_ptr->background.blue = png_ptr->background.gray;
+            }
+
+            /* The background is now in screen gamma: */
+            png_ptr->background_gamma_type = PNG_BACKGROUND_GAMMA_SCREEN;
+         } /* color_type != PNG_COLOR_TYPE_PALETTE */
+      }/* png_ptr->transformations & PNG_BACKGROUND */
+
+      else
+      /* Transformation does not include PNG_BACKGROUND */
+#endif /* PNG_READ_BACKGROUND_SUPPORTED */
+      if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+         /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
+         && ((png_ptr->transformations & PNG_EXPAND) == 0 ||
+         (png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
+#endif
+         )
+      {
+         png_colorp palette = png_ptr->palette;
+         int num_palette = png_ptr->num_palette;
+         int i;
+
+         /*NOTE: there are other transformations that should probably be in here
+          * too.
+          */
+         for (i = 0; i < num_palette; i++)
+         {
+            palette[i].red = png_ptr->gamma_table[palette[i].red];
+            palette[i].green = png_ptr->gamma_table[palette[i].green];
+            palette[i].blue = png_ptr->gamma_table[palette[i].blue];
+         }
+
+         /* Done the gamma correction. */
+         png_ptr->transformations &= ~PNG_GAMMA;
+      } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
+   }
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   else
+#endif
+#endif /* PNG_READ_GAMMA_SUPPORTED */
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+   /* No GAMMA transformation (see the hanging else 4 lines above) */
+   if ((png_ptr->transformations & PNG_COMPOSE) &&
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+   {
+      int i;
+      int istop = (int)png_ptr->num_trans;
+      png_color back;
+      png_colorp palette = png_ptr->palette;
+
+      back.red   = (png_byte)png_ptr->background.red;
+      back.green = (png_byte)png_ptr->background.green;
+      back.blue  = (png_byte)png_ptr->background.blue;
+
+      for (i = 0; i < istop; i++)
+      {
+         if (png_ptr->trans_alpha[i] == 0)
+         {
+            palette[i] = back;
+         }
+
+         else if (png_ptr->trans_alpha[i] != 0xff)
+         {
+            /* The png_composite() macro is defined in png.h */
+            png_composite(palette[i].red, palette[i].red,
+                png_ptr->trans_alpha[i], back.red);
+
+            png_composite(palette[i].green, palette[i].green,
+                png_ptr->trans_alpha[i], back.green);
+
+            png_composite(palette[i].blue, palette[i].blue,
+                png_ptr->trans_alpha[i], back.blue);
+         }
+      }
+
+      png_ptr->transformations &= ~PNG_COMPOSE;
+   }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED */
+
+#ifdef PNG_READ_SHIFT_SUPPORTED
+   if ((png_ptr->transformations & PNG_SHIFT) &&
+       (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE))
+   {
+      int i;
+      int istop = png_ptr->num_palette;
+      int shift = 8 - png_ptr->sig_bit.red;
+
+      /* significant bits can be in the range 1 to 7 for a meaninful result, if
+       * the number of significant bits is 0 then no shift is done (this is an
+       * error condition which is silently ignored.)
+       */
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      {
+         int component = png_ptr->palette[i].red;
+
+         component >>= shift;
+         png_ptr->palette[i].red = (png_byte)component;
+      }
+
+      shift = 8 - png_ptr->sig_bit.green;
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      {
+         int component = png_ptr->palette[i].green;
+
+         component >>= shift;
+         png_ptr->palette[i].green = (png_byte)component;
+      }
+
+      shift = 8 - png_ptr->sig_bit.blue;
+      if (shift > 0 && shift < 8) for (i=0; i<istop; ++i)
+      {
+         int component = png_ptr->palette[i].blue;
+
+         component >>= shift;
+         png_ptr->palette[i].blue = (png_byte)component;
+      }
+   }
+#endif  /* PNG_READ_SHIFT_SUPPORTED */
+}
+
+/* Modify the info structure to reflect the transformations.  The
+ * info should be updated so a PNG file could be written with it,
+ * assuming the transformations result in valid PNG data.
+ */
+void /* PRIVATE */
+png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
+{
+   png_debug(1, "in png_read_transform_info");
+
+#ifdef PNG_READ_EXPAND_SUPPORTED
+   if (png_ptr->transformations & PNG_EXPAND)
+   {
+      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      {
+         /* This check must match what actually happens in
+          * png_do_expand_palette; if it ever checks the tRNS chunk to see if
+          * it is all opaque we must do the same (at present it does not.)
+          */
+         if (png_ptr->num_trans > 0)
+            info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+
+         else
+            info_ptr->color_type = PNG_COLOR_TYPE_RGB;
+
+         info_ptr->bit_depth = 8;
+         info_ptr->num_trans = 0;
+      }
+      else
+      {
+         if (png_ptr->num_trans)
+         {
+            if (png_ptr->transformations & PNG_EXPAND_tRNS)
+               info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+         }
+         if (info_ptr->bit_depth < 8)
+            info_ptr->bit_depth = 8;
+
+         info_ptr->num_trans = 0;
+      }
+   }
+#endif
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
+   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
+   /* The following is almost certainly wrong unless the background value is in
+    * the screen space!
+    */
+   if (png_ptr->transformations & PNG_COMPOSE)
+      info_ptr->background = png_ptr->background;
+#endif
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
+    * however it seems that the code in png_init_read_transformations, which has
+    * been called before this from png_read_update_info->png_read_start_row
+    * sometimes does the gamma transform and cancels the flag.
+    */
+   info_ptr->gamma = png_ptr->gamma;
+#endif
+
+   if (info_ptr->bit_depth == 16)
+   {
+#  ifdef PNG_READ_16BIT_SUPPORTED
+#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_SCALE_16_TO_8)
+            info_ptr->bit_depth = 8;
+#     endif
+
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         if (png_ptr->transformations & PNG_16_TO_8)
+            info_ptr->bit_depth = 8;
+#     endif
+
+#  else
+      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
+       * the app program can chose if both APIs are available by setting the
+       * correct scaling to use.
+       */
+#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+         /* For compatibility with previous versions use the strip method by
+          * default.  This code works because if PNG_SCALE_16_TO_8 is already
+          * set the code below will do that in preference to the chop.
+          */
+         png_ptr->transformations |= PNG_16_TO_8;
+         info_ptr->bit_depth = 8;
+#     else
+
+#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+            png_ptr->transformations |= PNG_SCALE_16_TO_8;
+            info_ptr->bit_depth = 8;
+#        else
+
+            CONFIGURATION ERROR: you must enable at least one 16 to 8 method
+#        endif
+#    endif
+#endif /* !READ_16BIT_SUPPORTED */
+   }
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+      info_ptr->color_type = (png_byte)(info_ptr->color_type |
+         PNG_COLOR_MASK_COLOR);
+#endif
+
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_COLOR);
+#endif
+
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
+   {
+      if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
+          (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
+          png_ptr->palette_lookup && info_ptr->bit_depth == 8)
+      {
+         info_ptr->color_type = PNG_COLOR_TYPE_PALETTE;
+      }
+   }
+#endif
+
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+   if (png_ptr->transformations & PNG_EXPAND_16 && info_ptr->bit_depth == 8 &&
+      info_ptr->color_type != PNG_COLOR_TYPE_PALETTE)
+   {
+      info_ptr->bit_depth = 16;
+   }
+#endif
+
+#ifdef PNG_READ_PACK_SUPPORTED
+   if ((png_ptr->transformations & PNG_PACK) && (info_ptr->bit_depth < 8))
+      info_ptr->bit_depth = 8;
+#endif
+
+   if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+      info_ptr->channels = 1;
+
+   else if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
+      info_ptr->channels = 3;
+
+   else
+      info_ptr->channels = 1;
+
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if (png_ptr->transformations & PNG_STRIP_ALPHA)
+   {
+      info_ptr->color_type = (png_byte)(info_ptr->color_type &
+         ~PNG_COLOR_MASK_ALPHA);
+      info_ptr->num_trans = 0;
+   }
+#endif
+
+   if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
+      info_ptr->channels++;
+
+#ifdef PNG_READ_FILLER_SUPPORTED
+   /* STRIP_ALPHA and FILLER allowed:  MASK_ALPHA bit stripped above */
+   if ((png_ptr->transformations & PNG_FILLER) &&
+       ((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
+       (info_ptr->color_type == PNG_COLOR_TYPE_GRAY)))
+   {
+      info_ptr->channels++;
+      /* If adding a true alpha channel not just filler */
+      if (png_ptr->transformations & PNG_ADD_ALPHA)
+         info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
+   }
+#endif
+
+#if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
+defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
+   if (png_ptr->transformations & PNG_USER_TRANSFORM)
+   {
+      if (info_ptr->bit_depth < png_ptr->user_transform_depth)
+         info_ptr->bit_depth = png_ptr->user_transform_depth;
+
+      if (info_ptr->channels < png_ptr->user_transform_channels)
+         info_ptr->channels = png_ptr->user_transform_channels;
+   }
+#endif
+
+   info_ptr->pixel_depth = (png_byte)(info_ptr->channels *
+       info_ptr->bit_depth);
+
+   info_ptr->rowbytes = PNG_ROWBYTES(info_ptr->pixel_depth, info_ptr->width);
+
+   /* Adding in 1.5.4: cache the above value in png_struct so that we can later
+    * check in png_rowbytes that the user buffer won't get overwritten.  Note
+    * that the field is not always set - if png_read_update_info isn't called
+    * the application has to either not do any transforms or get the calculation
+    * right itself.
+    */
+   png_ptr->info_rowbytes = info_ptr->rowbytes;
+
+#ifndef PNG_READ_EXPAND_SUPPORTED
+   if (png_ptr)
+      return;
+#endif
+}
+
+/* Transform the row.  The order of transformations is significant,
+ * and is very touchy.  If you add a transformation, take care to
+ * decide how it fits in with the other transformations here.
+ */
+void /* PRIVATE */
+png_do_read_transformations(png_structp png_ptr, png_row_infop row_info)
+{
+   png_debug(1, "in png_do_read_transformations");
+
+   if (png_ptr->row_buf == NULL)
+   {
+      /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
+       * error is incredibly rare and incredibly easy to debug without this
+       * information.
+       */
+      png_error(png_ptr, "NULL row buffer");
+   }
+
+   /* The following is debugging; prior to 1.5.4 the code was never compiled in;
+    * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
+    * PNG_WARN_UNINITIALIZED_ROW removed.  In 1.5 the new flag is set only for
+    * selected new APIs to ensure that there is no API change.
+    */
+   if ((png_ptr->flags & PNG_FLAG_DETECT_UNINITIALIZED) != 0 &&
+      !(png_ptr->flags & PNG_FLAG_ROW_INIT))
+   {
+      /* Application has failed to call either png_read_start_image() or
+       * png_read_update_info() after setting transforms that expand pixels.
+       * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
+       */
+      png_error(png_ptr, "Uninitialized row");
+   }
+
+#ifdef PNG_READ_EXPAND_SUPPORTED
+   if (png_ptr->transformations & PNG_EXPAND)
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+      {
+         png_do_expand_palette(row_info, png_ptr->row_buf + 1,
+             png_ptr->palette, png_ptr->trans_alpha, png_ptr->num_trans);
+      }
+
+      else
+      {
+         if (png_ptr->num_trans &&
+             (png_ptr->transformations & PNG_EXPAND_tRNS))
+            png_do_expand(row_info, png_ptr->row_buf + 1,
+                &(png_ptr->trans_color));
+
+         else
+            png_do_expand(row_info, png_ptr->row_buf + 1,
+                NULL);
+      }
+   }
+#endif
+
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      !(png_ptr->transformations & PNG_COMPOSE) &&
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+         0 /* at_start == false, because SWAP_ALPHA happens later */);
+#endif
+
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+   if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+   {
+      int rgb_error =
+          png_do_rgb_to_gray(png_ptr, row_info,
+              png_ptr->row_buf + 1);
+
+      if (rgb_error)
+      {
+         png_ptr->rgb_to_gray_status=1;
+         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
+             PNG_RGB_TO_GRAY_WARN)
+            png_warning(png_ptr, "png_do_rgb_to_gray found nongray pixel");
+
+         if ((png_ptr->transformations & PNG_RGB_TO_GRAY) ==
+             PNG_RGB_TO_GRAY_ERR)
+            png_error(png_ptr, "png_do_rgb_to_gray found nongray pixel");
+      }
+   }
+#endif
+
+/* From Andreas Dilger e-mail to png-implement, 26 March 1998:
+ *
+ *   In most cases, the "simple transparency" should be done prior to doing
+ *   gray-to-RGB, or you will have to test 3x as many bytes to check if a
+ *   pixel is transparent.  You would also need to make sure that the
+ *   transparency information is upgraded to RGB.
+ *
+ *   To summarize, the current flow is:
+ *   - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
+ *                                   with background "in place" if transparent,
+ *                                   convert to RGB if necessary
+ *   - Gray + alpha -> composite with gray background and remove alpha bytes,
+ *                                   convert to RGB if necessary
+ *
+ *   To support RGB backgrounds for gray images we need:
+ *   - Gray + simple transparency -> convert to RGB + simple transparency,
+ *                                   compare 3 or 6 bytes and composite with
+ *                                   background "in place" if transparent
+ *                                   (3x compare/pixel compared to doing
+ *                                   composite with gray bkgrnd)
+ *   - Gray + alpha -> convert to RGB + alpha, composite with background and
+ *                                   remove alpha bytes (3x float
+ *                                   operations/pixel compared with composite
+ *                                   on gray background)
+ *
+ *  Greg's change will do this.  The reason it wasn't done before is for
+ *  performance, as this increases the per-pixel operations.  If we would check
+ *  in advance if the background was gray or RGB, and position the gray-to-RGB
+ *  transform appropriately, then it would save a lot of work/time.
+ */
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   /* If gray -> RGB, do so now only if background is non-gray; else do later
+    * for performance reasons
+    */
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+       !(png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+#endif
+
+#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
+   (defined PNG_READ_ALPHA_MODE_SUPPORTED)
+   if (png_ptr->transformations & PNG_COMPOSE)
+      png_do_compose(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   if ((png_ptr->transformations & PNG_GAMMA) &&
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+      /* Because RGB_TO_GRAY does the gamma transform. */
+      !(png_ptr->transformations & PNG_RGB_TO_GRAY) &&
+#endif
+#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
+   (defined PNG_READ_ALPHA_MODE_SUPPORTED)
+      /* Because PNG_COMPOSE does the gamma transform if there is something to
+       * do (if there is an alpha channel or transparency.)
+       */
+       !((png_ptr->transformations & PNG_COMPOSE) &&
+       ((png_ptr->num_trans != 0) ||
+       (png_ptr->color_type & PNG_COLOR_MASK_ALPHA))) &&
+#endif
+      /* Because png_init_read_transformations transforms the palette, unless
+       * RGB_TO_GRAY will do the transform.
+       */
+       (png_ptr->color_type != PNG_COLOR_TYPE_PALETTE))
+      png_do_gamma(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+   if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+      (png_ptr->transformations & PNG_COMPOSE) &&
+      (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+      row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
+      png_do_strip_channel(row_info, png_ptr->row_buf + 1,
+         0 /* at_start == false, because SWAP_ALPHA happens later */);
+#endif
+
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+   if ((png_ptr->transformations & PNG_ENCODE_ALPHA) &&
+      (row_info->color_type & PNG_COLOR_MASK_ALPHA))
+      png_do_encode_alpha(row_info, png_ptr->row_buf + 1, png_ptr);
+#endif
+
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+   if (png_ptr->transformations & PNG_SCALE_16_TO_8)
+      png_do_scale_16_to_8(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+   /* There is no harm in doing both of these because only one has any effect,
+    * by putting the 'scale' option first if the app asks for scale (either by
+    * calling the API or in a TRANSFORM flag) this is what happens.
+    */
+   if (png_ptr->transformations & PNG_16_TO_8)
+      png_do_chop(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
+   {
+      png_do_quantize(row_info, png_ptr->row_buf + 1,
+          png_ptr->palette_lookup, png_ptr->quantize_index);
+
+      if (row_info->rowbytes == 0)
+         png_error(png_ptr, "png_do_quantize returned rowbytes=0");
+   }
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+   /* Do the expansion now, after all the arithmetic has been done.  Notice
+    * that previous transformations can handle the PNG_EXPAND_16 flag if this
+    * is efficient (particularly true in the case of gamma correction, where
+    * better accuracy results faster!)
+    */
+   if (png_ptr->transformations & PNG_EXPAND_16)
+      png_do_expand_16(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+   /*NOTE: moved here in 1.5.4 (from much later in this list.) */
+   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) &&
+       (png_ptr->mode & PNG_BACKGROUND_IS_GRAY))
+      png_do_gray_to_rgb(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_INVERT_SUPPORTED
+   if (png_ptr->transformations & PNG_INVERT_MONO)
+      png_do_invert(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_SHIFT_SUPPORTED
+   if (png_ptr->transformations & PNG_SHIFT)
+      png_do_unshift(row_info, png_ptr->row_buf + 1,
+          &(png_ptr->shift));
+#endif
+
+#ifdef PNG_READ_PACK_SUPPORTED
+   if (png_ptr->transformations & PNG_PACK)
+      png_do_unpack(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_BGR_SUPPORTED
+   if (png_ptr->transformations & PNG_BGR)
+      png_do_bgr(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_PACKSWAP_SUPPORTED
+   if (png_ptr->transformations & PNG_PACKSWAP)
+      png_do_packswap(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_FILLER_SUPPORTED
+   if (png_ptr->transformations & PNG_FILLER)
+      png_do_read_filler(row_info, png_ptr->row_buf + 1,
+          (png_uint_32)png_ptr->filler, png_ptr->flags);
+#endif
+
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+   if (png_ptr->transformations & PNG_INVERT_ALPHA)
+      png_do_read_invert_alpha(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
+   if (png_ptr->transformations & PNG_SWAP_ALPHA)
+      png_do_read_swap_alpha(row_info, png_ptr->row_buf + 1);
+#endif
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+#ifdef PNG_READ_SWAP_SUPPORTED
+   if (png_ptr->transformations & PNG_SWAP_BYTES)
+      png_do_swap(row_info, png_ptr->row_buf + 1);
+#endif
+#endif
+
+#ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
+   if (png_ptr->transformations & PNG_USER_TRANSFORM)
+    {
+      if (png_ptr->read_user_transform_fn != NULL)
+         (*(png_ptr->read_user_transform_fn)) /* User read transform function */
+             (png_ptr,     /* png_ptr */
+             row_info,     /* row_info: */
+                /*  png_uint_32 width;       width of row */
+                /*  png_size_t rowbytes;     number of bytes in row */
+                /*  png_byte color_type;     color type of pixels */
+                /*  png_byte bit_depth;      bit depth of samples */
+                /*  png_byte channels;       number of channels (1-4) */
+                /*  png_byte pixel_depth;    bits per pixel (depth*channels) */
+             png_ptr->row_buf + 1);    /* start of pixel data for row */
+#ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
+      if (png_ptr->user_transform_depth)
+         row_info->bit_depth = png_ptr->user_transform_depth;
+
+      if (png_ptr->user_transform_channels)
+         row_info->channels = png_ptr->user_transform_channels;
+#endif
+      row_info->pixel_depth = (png_byte)(row_info->bit_depth *
+          row_info->channels);
+
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_info->width);
+   }
+#endif
+}
+
+#ifdef PNG_READ_PACK_SUPPORTED
+/* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
+ * without changing the actual values.  Thus, if you had a row with
+ * a bit depth of 1, you would end up with bytes that only contained
+ * the numbers 0 or 1.  If you would rather they contain 0 and 255, use
+ * png_do_shift() after this.
+ */
+void /* PRIVATE */
+png_do_unpack(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_unpack");
+
+   if (row_info->bit_depth < 8)
+   {
+      png_uint_32 i;
+      png_uint_32 row_width=row_info->width;
+
+      switch (row_info->bit_depth)
+      {
+         case 1:
+         {
+            png_bytep sp = row + (png_size_t)((row_width - 1) >> 3);
+            png_bytep dp = row + (png_size_t)row_width - 1;
+            png_uint_32 shift = 7 - (int)((row_width + 7) & 0x07);
+            for (i = 0; i < row_width; i++)
+            {
+               *dp = (png_byte)((*sp >> shift) & 0x01);
+
+               if (shift == 7)
+               {
+                  shift = 0;
+                  sp--;
+               }
+
+               else
+                  shift++;
+
+               dp--;
+            }
+            break;
+         }
+
+         case 2:
+         {
+
+            png_bytep sp = row + (png_size_t)((row_width - 1) >> 2);
+            png_bytep dp = row + (png_size_t)row_width - 1;
+            png_uint_32 shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+            for (i = 0; i < row_width; i++)
+            {
+               *dp = (png_byte)((*sp >> shift) & 0x03);
+
+               if (shift == 6)
+               {
+                  shift = 0;
+                  sp--;
+               }
+
+               else
+                  shift += 2;
+
+               dp--;
+            }
+            break;
+         }
+
+         case 4:
+         {
+            png_bytep sp = row + (png_size_t)((row_width - 1) >> 1);
+            png_bytep dp = row + (png_size_t)row_width - 1;
+            png_uint_32 shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
+            for (i = 0; i < row_width; i++)
+            {
+               *dp = (png_byte)((*sp >> shift) & 0x0f);
+
+               if (shift == 4)
+               {
+                  shift = 0;
+                  sp--;
+               }
+
+               else
+                  shift = 4;
+
+               dp--;
+            }
+            break;
+         }
+
+         default:
+            break;
+      }
+      row_info->bit_depth = 8;
+      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+      row_info->rowbytes = row_width * row_info->channels;
+   }
+}
+#endif
+
+#ifdef PNG_READ_SHIFT_SUPPORTED
+/* Reverse the effects of png_do_shift.  This routine merely shifts the
+ * pixels back to their significant bits values.  Thus, if you have
+ * a row of bit depth 8, but only 5 are significant, this will shift
+ * the values back to 0 through 31.
+ */
+void /* PRIVATE */
+png_do_unshift(png_row_infop row_info, png_bytep row,
+    png_const_color_8p sig_bits)
+{
+   int color_type;
+
+   png_debug(1, "in png_do_unshift");
+
+   /* The palette case has already been handled in the _init routine. */
+   color_type = row_info->color_type;
+
+   if (color_type != PNG_COLOR_TYPE_PALETTE)
+   {
+      int shift[4];
+      int channels = 0;
+      int bit_depth = row_info->bit_depth;
+
+      if (color_type & PNG_COLOR_MASK_COLOR)
+      {
+         shift[channels++] = bit_depth - sig_bits->red;
+         shift[channels++] = bit_depth - sig_bits->green;
+         shift[channels++] = bit_depth - sig_bits->blue;
+      }
+
+      else
+      {
+         shift[channels++] = bit_depth - sig_bits->gray;
+      }
+
+      if (color_type & PNG_COLOR_MASK_ALPHA)
+      {
+         shift[channels++] = bit_depth - sig_bits->alpha;
+      }
+
+      {
+         int c, have_shift;
+
+         for (c = have_shift = 0; c < channels; ++c)
+         {
+            /* A shift of more than the bit depth is an error condition but it
+             * gets ignored here.
+             */
+            if (shift[c] <= 0 || shift[c] >= bit_depth)
+               shift[c] = 0;
+
+            else
+               have_shift = 1;
+         }
+
+         if (!have_shift)
+            return;
+      }
+
+      switch (bit_depth)
+      {
+         default:
+         /* Must be 1bpp gray: should not be here! */
+            /* NOTREACHED */
+            break;
+
+         case 2:
+         /* Must be 2bpp gray */
+         /* assert(channels == 1 && shift[0] == 1) */
+         {
+            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
+
+            while (bp < bp_end)
+            {
+               int b = (*bp >> 1) & 0x55;
+               *bp++ = (png_byte)b;
+            }
+            break;
+         }
+
+         case 4:
+         /* Must be 4bpp gray */
+         /* assert(channels == 1) */
+         {
+            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int gray_shift = shift[0];
+            int mask =  0xf >> gray_shift;
+
+            mask |= mask << 4;
+
+            while (bp < bp_end)
+            {
+               int b = (*bp >> gray_shift) & mask;
+               *bp++ = (png_byte)b;
+            }
+            break;
+         }
+
+         case 8:
+         /* Single byte components, G, GA, RGB, RGBA */
+         {
+            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int channel = 0;
+
+            while (bp < bp_end)
+            {
+               int b = *bp >> shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
+               *bp++ = (png_byte)b;
+            }
+            break;
+         }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+         case 16:
+         /* Double byte components, G, GA, RGB, RGBA */
+         {
+            png_bytep bp = row;
+            png_bytep bp_end = bp + row_info->rowbytes;
+            int channel = 0;
+
+            while (bp < bp_end)
+            {
+               int value = (bp[0] << 8) + bp[1];
+
+               value >>= shift[channel];
+               if (++channel >= channels)
+                  channel = 0;
+               *bp++ = (png_byte)(value >> 8);
+               *bp++ = (png_byte)(value & 0xff);
+            }
+            break;
+         }
+#endif
+      }
+   }
+}
+#endif
+
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
+/* Scale rows of bit depth 16 down to 8 accurately */
+void /* PRIVATE */
+png_do_scale_16_to_8(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_scale_16_to_8");
+
+   if (row_info->bit_depth == 16)
+   {
+      png_bytep sp = row; /* source */
+      png_bytep dp = row; /* destination */
+      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+
+      while (sp < ep)
+      {
+         /* The input is an array of 16 bit components, these must be scaled to
+          * 8 bits each.  For a 16 bit value V the required value (from the PNG
+          * specification) is:
+          *
+          *    (V * 255) / 65535
+          *
+          * This reduces to round(V / 257), or floor((V + 128.5)/257)
+          *
+          * Represent V as the two byte value vhi.vlo.  Make a guess that the
+          * result is the top byte of V, vhi, then the correction to this value
+          * is:
+          *
+          *    error = floor(((V-vhi.vhi) + 128.5) / 257)
+          *          = floor(((vlo-vhi) + 128.5) / 257)
+          *
+          * This can be approximated using integer arithmetic (and a signed
+          * shift):
+          *
+          *    error = (vlo-vhi+128) >> 8;
+          *
+          * The approximate differs from the exact answer only when (vlo-vhi) is
+          * 128; it then gives a correction of +1 when the exact correction is
+          * 0.  This gives 128 errors.  The exact answer (correct for all 16 bit
+          * input values) is:
+          *
+          *    error = (vlo-vhi+128)*65535 >> 24;
+          *
+          * An alternative arithmetic calculation which also gives no errors is:
+          *
+          *    (V * 255 + 32895) >> 16
+          */
+
+         png_int_32 tmp = *sp++; /* must be signed! */
+         tmp += (((int)*sp++ - tmp + 128) * 65535) >> 24;
+         *dp++ = (png_byte)tmp;
+      }
+
+      row_info->bit_depth = 8;
+      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+      row_info->rowbytes = row_info->width * row_info->channels;
+   }
+}
+#endif
+
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
+void /* PRIVATE */
+/* Simply discard the low byte.  This was the default behavior prior
+ * to libpng-1.5.4.
+ */
+png_do_chop(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_chop");
+
+   if (row_info->bit_depth == 16)
+   {
+      png_bytep sp = row; /* source */
+      png_bytep dp = row; /* destination */
+      png_bytep ep = sp + row_info->rowbytes; /* end+1 */
+
+      while (sp < ep)
+      {
+         *dp++ = *sp;
+         sp += 2; /* skip low byte */
+      }
+
+      row_info->bit_depth = 8;
+      row_info->pixel_depth = (png_byte)(8 * row_info->channels);
+      row_info->rowbytes = row_info->width * row_info->channels;
+   }
+}
+#endif
+
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
+void /* PRIVATE */
+png_do_read_swap_alpha(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_read_swap_alpha");
+
+   {
+      png_uint_32 row_width = row_info->width;
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+      {
+         /* This converts from RGBA to ARGB */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_byte save;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               save = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = save;
+            }
+         }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+         /* This converts from RRGGBBAA to AARRGGBB */
+         else
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_byte save[2];
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               save[0] = *(--sp);
+               save[1] = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = save[0];
+               *(--dp) = save[1];
+            }
+         }
+#endif
+      }
+
+      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
+         /* This converts from GA to AG */
+         if (row_info->bit_depth == 8)
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_byte save;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               save = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = save;
+            }
+         }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+         /* This converts from GGAA to AAGG */
+         else
+         {
+            png_bytep sp = row + row_info->rowbytes;
+            png_bytep dp = sp;
+            png_byte save[2];
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               save[0] = *(--sp);
+               save[1] = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = save[0];
+               *(--dp) = save[1];
+            }
+         }
+#endif
+      }
+   }
+}
+#endif
+
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
+void /* PRIVATE */
+png_do_read_invert_alpha(png_row_infop row_info, png_bytep row)
+{
+   png_uint_32 row_width;
+   png_debug(1, "in png_do_read_invert_alpha");
+
+   row_width = row_info->width;
+   if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         /* This inverts the alpha channel in RGBA */
+         png_bytep sp = row + row_info->rowbytes;
+         png_bytep dp = sp;
+         png_uint_32 i;
+
+         for (i = 0; i < row_width; i++)
+         {
+            *(--dp) = (png_byte)(255 - *(--sp));
+
+/*          This does nothing:
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            We can replace it with:
+*/
+            sp-=3;
+            dp=sp;
+         }
+      }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+      /* This inverts the alpha channel in RRGGBBAA */
+      else
+      {
+         png_bytep sp = row + row_info->rowbytes;
+         png_bytep dp = sp;
+         png_uint_32 i;
+
+         for (i = 0; i < row_width; i++)
+         {
+            *(--dp) = (png_byte)(255 - *(--sp));
+            *(--dp) = (png_byte)(255 - *(--sp));
+
+/*          This does nothing:
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+            We can replace it with:
+*/
+            sp-=6;
+            dp=sp;
+         }
+      }
+#endif
+   }
+   else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         /* This inverts the alpha channel in GA */
+         png_bytep sp = row + row_info->rowbytes;
+         png_bytep dp = sp;
+         png_uint_32 i;
+
+         for (i = 0; i < row_width; i++)
+         {
+            *(--dp) = (png_byte)(255 - *(--sp));
+            *(--dp) = *(--sp);
+         }
+      }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+      else
+      {
+         /* This inverts the alpha channel in GGAA */
+         png_bytep sp  = row + row_info->rowbytes;
+         png_bytep dp = sp;
+         png_uint_32 i;
+
+         for (i = 0; i < row_width; i++)
+         {
+            *(--dp) = (png_byte)(255 - *(--sp));
+            *(--dp) = (png_byte)(255 - *(--sp));
+/*
+            *(--dp) = *(--sp);
+            *(--dp) = *(--sp);
+*/
+            sp-=2;
+            dp=sp;
+         }
+      }
+#endif
+   }
+}
+#endif
+
+#ifdef PNG_READ_FILLER_SUPPORTED
+/* Add filler channel if we have RGB color */
+void /* PRIVATE */
+png_do_read_filler(png_row_infop row_info, png_bytep row,
+    png_uint_32 filler, png_uint_32 flags)
+{
+   png_uint_32 i;
+   png_uint_32 row_width = row_info->width;
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+   png_byte hi_filler = (png_byte)((filler>>8) & 0xff);
+#endif
+   png_byte lo_filler = (png_byte)(filler & 0xff);
+
+   png_debug(1, "in png_do_read_filler");
+
+   if (
+       row_info->color_type == PNG_COLOR_TYPE_GRAY)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         if (flags & PNG_FLAG_FILLER_AFTER)
+         {
+            /* This changes the data from G to GX */
+            png_bytep sp = row + (png_size_t)row_width;
+            png_bytep dp =  sp + (png_size_t)row_width;
+            for (i = 1; i < row_width; i++)
+            {
+               *(--dp) = lo_filler;
+               *(--dp) = *(--sp);
+            }
+            *(--dp) = lo_filler;
+            row_info->channels = 2;
+            row_info->pixel_depth = 16;
+            row_info->rowbytes = row_width * 2;
+         }
+
+         else
+         {
+            /* This changes the data from G to XG */
+            png_bytep sp = row + (png_size_t)row_width;
+            png_bytep dp = sp  + (png_size_t)row_width;
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = lo_filler;
+            }
+            row_info->channels = 2;
+            row_info->pixel_depth = 16;
+            row_info->rowbytes = row_width * 2;
+         }
+      }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+      else if (row_info->bit_depth == 16)
+      {
+         if (flags & PNG_FLAG_FILLER_AFTER)
+         {
+            /* This changes the data from GG to GGXX */
+            png_bytep sp = row + (png_size_t)row_width * 2;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 1; i < row_width; i++)
+            {
+               *(--dp) = hi_filler;
+               *(--dp) = lo_filler;
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+            }
+            *(--dp) = hi_filler;
+            *(--dp) = lo_filler;
+            row_info->channels = 2;
+            row_info->pixel_depth = 32;
+            row_info->rowbytes = row_width * 4;
+         }
+
+         else
+         {
+            /* This changes the data from GG to XXGG */
+            png_bytep sp = row + (png_size_t)row_width * 2;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = hi_filler;
+               *(--dp) = lo_filler;
+            }
+            row_info->channels = 2;
+            row_info->pixel_depth = 32;
+            row_info->rowbytes = row_width * 4;
+         }
+      }
+#endif
+   } /* COLOR_TYPE == GRAY */
+   else if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         if (flags & PNG_FLAG_FILLER_AFTER)
+         {
+            /* This changes the data from RGB to RGBX */
+            png_bytep sp = row + (png_size_t)row_width * 3;
+            png_bytep dp = sp  + (png_size_t)row_width;
+            for (i = 1; i < row_width; i++)
+            {
+               *(--dp) = lo_filler;
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+            }
+            *(--dp) = lo_filler;
+            row_info->channels = 4;
+            row_info->pixel_depth = 32;
+            row_info->rowbytes = row_width * 4;
+         }
+
+         else
+         {
+            /* This changes the data from RGB to XRGB */
+            png_bytep sp = row + (png_size_t)row_width * 3;
+            png_bytep dp = sp + (png_size_t)row_width;
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = lo_filler;
+            }
+            row_info->channels = 4;
+            row_info->pixel_depth = 32;
+            row_info->rowbytes = row_width * 4;
+         }
+      }
+
+#ifdef PNG_READ_16BIT_SUPPORTED
+      else if (row_info->bit_depth == 16)
+      {
+         if (flags & PNG_FLAG_FILLER_AFTER)
+         {
+            /* This changes the data from RRGGBB to RRGGBBXX */
+            png_bytep sp = row + (png_size_t)row_width * 6;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 1; i < row_width; i++)
+            {
+               *(--dp) = hi_filler;
+               *(--dp) = lo_filler;
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+            }
+            *(--dp) = hi_filler;
+            *(--dp) = lo_filler;
+            row_info->channels = 4;
+            row_info->pixel_depth = 64;
+            row_info->rowbytes = row_width * 8;
+         }
+
+         else
+         {
+            /* This changes the data from RRGGBB to XXRRGGBB */
+            png_bytep sp = row + (png_size_t)row_width * 6;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 0; i < row_width; i++)
+            {
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = *(--sp);
+               *(--dp) = hi_filler;
+               *(--dp) = lo_filler;
+            }
+
+            row_info->channels = 4;
+            row_info->pixel_depth = 64;
+            row_info->rowbytes = row_width * 8;
+         }
+      }
+#endif
+   } /* COLOR_TYPE == RGB */
+}
+#endif
+
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
+/* Expand grayscale files to RGB, with or without alpha */
+void /* PRIVATE */
+png_do_gray_to_rgb(png_row_infop row_info, png_bytep row)
+{
+   png_uint_32 i;
+   png_uint_32 row_width = row_info->width;
+
+   png_debug(1, "in png_do_gray_to_rgb");
+
+   if (row_info->bit_depth >= 8 &&
+       !(row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+      {
+         if (row_info->bit_depth == 8)
+         {
+            /* This changes G to RGB */
+            png_bytep sp = row + (png_size_t)row_width - 1;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 0; i < row_width; i++)
+            {
+               *(dp--) = *sp;
+               *(dp--) = *sp;
+               *(dp--) = *(sp--);
+            }
+         }
+
+         else
+         {
+            /* This changes GG to RRGGBB */
+            png_bytep sp = row + (png_size_t)row_width * 2 - 1;
+            png_bytep dp = sp  + (png_size_t)row_width * 4;
+            for (i = 0; i < row_width; i++)
+            {
+               *(dp--) = *sp;
+               *(dp--) = *(sp - 1);
+               *(dp--) = *sp;
+               *(dp--) = *(sp - 1);
+               *(dp--) = *(sp--);
+               *(dp--) = *(sp--);
+            }
+         }
+      }
+
+      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+      {
+         if (row_info->bit_depth == 8)
+         {
+            /* This changes GA to RGBA */
+            png_bytep sp = row + (png_size_t)row_width * 2 - 1;
+            png_bytep dp = sp  + (png_size_t)row_width * 2;
+            for (i = 0; i < row_width; i++)
+            {
+               *(dp--) = *(sp--);
+               *(dp--) = *sp;
+               *(dp--) = *sp;
+               *(dp--) = *(sp--);
+            }
+         }
+
+         else
+         {
+            /* This changes GGAA to RRGGBBAA */
+            png_bytep sp = row + (png_size_t)row_width * 4 - 1;
+            png_bytep dp = sp  + (png_size_t)row_width * 4;
+            for (i = 0; i < row_width; i++)
+            {
+               *(dp--) = *(sp--);
+               *(dp--) = *(sp--);
+               *(dp--) = *sp;
+               *(dp--) = *(sp - 1);
+               *(dp--) = *sp;
+               *(dp--) = *(sp - 1);
+               *(dp--) = *(sp--);
+               *(dp--) = *(sp--);
+            }
+         }
+      }
+      row_info->channels = (png_byte)(row_info->channels + 2);
+      row_info->color_type |= PNG_COLOR_MASK_COLOR;
+      row_info->pixel_depth = (png_byte)(row_info->channels *
+          row_info->bit_depth);
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+   }
+}
+#endif
+
+#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
+/* Reduce RGB files to grayscale, with or without alpha
+ * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
+ * <http://www.inforamp.net/~poynton/>  (THIS LINK IS DEAD June 2008 but
+ * versions dated 1998 through November 2002 have been archived at
+ * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
+ * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
+ * Charles Poynton poynton at poynton.com
+ *
+ *     Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
+ *
+ *  which can be expressed with integers as
+ *
+ *     Y = (6969 * R + 23434 * G + 2365 * B)/32768
+ *
+ * Poynton's current link (as of January 2003 through July 2011):
+ * <http://www.poynton.com/notes/colour_and_gamma/>
+ * has changed the numbers slightly:
+ *
+ *     Y = 0.2126*R + 0.7152*G + 0.0722*B
+ *
+ *  which can be expressed with integers as
+ *
+ *     Y = (6966 * R + 23436 * G + 2366 * B)/32768
+ *
+ *  Historically, however, libpng uses numbers derived from the ITU-R Rec 709
+ *  end point chromaticities and the D65 white point.  Depending on the
+ *  precision used for the D65 white point this produces a variety of different
+ *  numbers, however if the four decimal place value used in ITU-R Rec 709 is
+ *  used (0.3127,0.3290) the Y calculation would be:
+ *
+ *     Y = (6968 * R + 23435 * G + 2366 * B)/32768
+ *
+ *  While this is correct the rounding results in an overflow for white, because
+ *  the sum of the rounded coefficients is 32769, not 32768.  Consequently
+ *  libpng uses, instead, the closest non-overflowing approximation:
+ *
+ *     Y = (6968 * R + 23434 * G + 2366 * B)/32768
+ *
+ *  Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
+ *  (including an sRGB chunk) then the chromaticities are used to calculate the
+ *  coefficients.  See the chunk handling in pngrutil.c for more information.
+ *
+ *  In all cases the calculation is to be done in a linear colorspace.  If no
+ *  gamma information is available to correct the encoding of the original RGB
+ *  values this results in an implicit assumption that the original PNG RGB
+ *  values were linear.
+ *
+ *  Other integer coefficents can be used via png_set_rgb_to_gray().  Because
+ *  the API takes just red and green coefficients the blue coefficient is
+ *  calculated to make the sum 32768.  This will result in different rounding
+ *  to that used above.
+ */
+int /* PRIVATE */
+png_do_rgb_to_gray(png_structp png_ptr, png_row_infop row_info, png_bytep row)
+
+{
+   int rgb_error = 0;
+
+   png_debug(1, "in png_do_rgb_to_gray");
+
+   if (!(row_info->color_type & PNG_COLOR_MASK_PALETTE) &&
+       (row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
+      PNG_CONST png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+      PNG_CONST png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+      PNG_CONST png_uint_32 bc = 32768 - rc - gc;
+      PNG_CONST png_uint_32 row_width = row_info->width;
+      PNG_CONST int have_alpha =
+         (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+
+      if (row_info->bit_depth == 8)
+      {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+         /* Notice that gamma to/from 1 are not necessarily inverses (if
+          * there is an overall gamma correction).  Prior to 1.5.5 this code
+          * checked the linearized values for equality; this doesn't match
+          * the documentation, the original values must be checked.
+          */
+         if (png_ptr->gamma_from_1 != NULL && png_ptr->gamma_to_1 != NULL)
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               png_byte red   = *(sp++);
+               png_byte green = *(sp++);
+               png_byte blue  = *(sp++);
+
+               if (red != green || red != blue)
+               {
+                  red = png_ptr->gamma_to_1[red];
+                  green = png_ptr->gamma_to_1[green];
+                  blue = png_ptr->gamma_to_1[blue];
+
+                  rgb_error |= 1;
+                  *(dp++) = png_ptr->gamma_from_1[
+                      (rc*red + gc*green + bc*blue + 16384)>>15];
+               }
+
+               else
+               {
+                  /* If there is no overall correction the table will not be
+                   * set.
+                   */
+                  if (png_ptr->gamma_table != NULL)
+                     red = png_ptr->gamma_table[red];
+
+                  *(dp++) = red;
+               }
+
+               if (have_alpha)
+                  *(dp++) = *(sp++);
+            }
+         }
+         else
+#endif
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               png_byte red   = *(sp++);
+               png_byte green = *(sp++);
+               png_byte blue  = *(sp++);
+
+               if (red != green || red != blue)
+               {
+                  rgb_error |= 1;
+                  /*NOTE: this is the historical approach which simply
+                   * truncates the results.
+                   */
+                  *(dp++) = (png_byte)((rc*red + gc*green + bc*blue)>>15);
+               }
+
+               else
+                  *(dp++) = red;
+
+               if (have_alpha)
+                  *(dp++) = *(sp++);
+            }
+         }
+      }
+
+      else /* RGB bit_depth == 16 */
+      {
+#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
+         if (png_ptr->gamma_16_to_1 != NULL && png_ptr->gamma_16_from_1 != NULL)
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               png_uint_16 red, green, blue, w;
+
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+
+               if (red == green && red == blue)
+               {
+                  if (png_ptr->gamma_16_table != NULL)
+                     w = png_ptr->gamma_16_table[(red&0xff)
+                         >> png_ptr->gamma_shift][red>>8];
+
+                  else
+                     w = red;
+               }
+
+               else
+               {
+                  png_uint_16 red_1   = png_ptr->gamma_16_to_1[(red&0xff)
+                      >> png_ptr->gamma_shift][red>>8];
+                  png_uint_16 green_1 =
+                      png_ptr->gamma_16_to_1[(green&0xff) >>
+                      png_ptr->gamma_shift][green>>8];
+                  png_uint_16 blue_1  = png_ptr->gamma_16_to_1[(blue&0xff)
+                      >> png_ptr->gamma_shift][blue>>8];
+                  png_uint_16 gray16  = (png_uint_16)((rc*red_1 + gc*green_1
+                      + bc*blue_1 + 16384)>>15);
+                  w = png_ptr->gamma_16_from_1[(gray16&0xff) >>
+                      png_ptr->gamma_shift][gray16 >> 8];
+                  rgb_error |= 1;
+               }
+
+               *(dp++) = (png_byte)((w>>8) & 0xff);
+               *(dp++) = (png_byte)(w & 0xff);
+
+               if (have_alpha)
+               {
+                  *(dp++) = *(sp++);
+                  *(dp++) = *(sp++);
+               }
+            }
+         }
+         else
+#endif
+         {
+            png_bytep sp = row;
+            png_bytep dp = row;
+            png_uint_32 i;
+
+            for (i = 0; i < row_width; i++)
+            {
+               png_uint_16 red, green, blue, gray16;
+
+               red   = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               green = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+               blue  = (png_uint_16)(((*(sp))<<8) | *(sp + 1)); sp += 2;
+
+               if (red != green || red != blue)
+                  rgb_error |= 1;
+
+               /* From 1.5.5 in the 16 bit case do the accurate conversion even
+                * in the 'fast' case - this is because this is where the code
+                * ends up when handling linear 16 bit data.
+                */
+               gray16  = (png_uint_16)((rc*red + gc*green + bc*blue + 16384) >>
+                  15);
+               *(dp++) = (png_byte)((gray16>>8) & 0xff);
+               *(dp++) = (png_byte)(gray16 & 0xff);
+
+               if (have_alpha)
+               {
+                  *(dp++) = *(sp++);
+                  *(dp++) = *(sp++);
+               }
+            }
+         }
+      }
+
+      row_info->channels = (png_byte)(row_info->channels - 2);
+      row_info->color_type = (png_byte)(row_info->color_type &
+          ~PNG_COLOR_MASK_COLOR);
+      row_info->pixel_depth = (png_byte)(row_info->channels *
+          row_info->bit_depth);
+      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+   }
+   return rgb_error;
+}
+#endif
+#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
+
+#ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
+/* Build a grayscale palette.  Palette is assumed to be 1 << bit_depth
+ * large of png_color.  This lets grayscale images be treated as
+ * paletted.  Most useful for gamma correction and simplification
+ * of code.  This API is not used internally.
+ */
+void PNGAPI
+png_build_grayscale_palette(int bit_depth, png_colorp palette)
+{
+   int num_palette;
+   int color_inc;
+   int i;
+   int v;
+
+   png_debug(1, "in png_do_build_grayscale_palette");
+
+   if (palette == NULL)
+      return;
+
+   switch (bit_depth)
+   {
+      case 1:
+         num_palette = 2;
+         color_inc = 0xff;
+         break;
+
+      case 2:
+         num_palette = 4;
+         color_inc = 0x55;
+         break;
+
+      case 4:
+         num_palette = 16;
+         color_inc = 0x11;
+         break;
+
+      case 8:
+         num_palette = 256;
+         color_inc = 1;
+         break;
+
+      default:
+         num_palette = 0;
+         color_inc = 0;
+         break;
+   }
+
+   for (i = 0, v = 0; i < num_palette; i++, v += color_inc)
+   {
+      palette[i].red = (png_byte)v;
+      palette[i].green = (png_byte)v;
+      palette[i].blue = (png_byte)v;
+   }
+}
+#endif
+
+
+#ifdef PNG_READ_TRANSFORMS_SUPPORTED
+#if (defined PNG_READ_BACKGROUND_SUPPORTED) ||\
+   (defined PNG_READ_ALPHA_MODE_SUPPORTED)
+/* Replace any alpha or transparency with the supplied background color.
+ * "background" is already in the screen gamma, while "background_1" is
+ * at a gamma of 1.0.  Paletted files have already been taken care of.
+ */
+void /* PRIVATE */
+png_do_compose(png_row_infop row_info, png_bytep row, png_structp png_ptr)
+{
+#ifdef PNG_READ_GAMMA_SUPPORTED
+   png_const_bytep gamma_table = png_ptr->gamma_table;
+   png_const_bytep gamma_from_1 = png_ptr->gamma_from_1;
+   png_const_bytep gamma_to_1 = png_ptr->gamma_to_1;
+   png_const_uint_16pp gamma_16 = png_ptr->gamma_16_table;
+   png_const_uint_16pp gamma_16_from_1 = png_ptr->gamma_16_from_1;
+   png_const_uint_16pp gamma_16_to_1 = png_ptr->gamma_16_to_1;
+   int gamma_shift = png_ptr->gamma_shift;
+#endif
+
+   png_bytep sp;
+   png_uint_32 i;
+   png_uint_32 row_width = row_info->width;
+   int optimize = (png_ptr->flags & PNG_FLAG_OPTIMIZE_ALPHA) != 0;
+   int shift;
+
+   png_debug(1, "in png_do_compose");
+
+   {
+      switch (row_info->color_type)
+      {
+         case PNG_COLOR_TYPE_GRAY:
+         {
+            switch (row_info->bit_depth)
+            {
+               case 1:
+               {
+                  sp = row;
+                  shift = 7;
+                  for (i = 0; i < row_width; i++)
+                  {
+                     if ((png_uint_16)((*sp >> shift) & 0x01)
+                        == png_ptr->trans_color.gray)
+                     {
+                        *sp &= (png_byte)((0x7f7f >> (7 - shift)) & 0xff);
+                        *sp |= (png_byte)(png_ptr->background.gray << shift);
+                     }
+
+                     if (!shift)
+                     {
+                        shift = 7;
+                        sp++;
+                     }
+
+                     else
+                        shift--;
+                  }
+                  break;
+               }
+
+               case 2:
+               {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                  if (gamma_table != NULL)
+                  {
+                     sp = row;
+                     shift = 6;
+                     for (i = 0; i < row_width; i++)
+                     {
+                        if ((png_uint_16)((*sp >> shift) & 0x03)
+                            == png_ptr->trans_color.gray)
+                        {
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                        }
+
+                        else
+                        {
+                           png_byte p = (png_byte)((*sp >> shift) & 0x03);
+                           png_byte g = (png_byte)((gamma_table [p | (p << 2) |
+                               (p << 4) | (p << 6)] >> 6) & 0x03);
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(g << shift);
+                        }
+
+                        if (!shift)
+                        {
+                           shift = 6;
+                           sp++;
+                        }
+
+                        else
+                           shift -= 2;
+                     }
+                  }
+
+                  else
+#endif
+                  {
+                     sp = row;
+                     shift = 6;
+                     for (i = 0; i < row_width; i++)
+                     {
+                        if ((png_uint_16)((*sp >> shift) & 0x03)
+                            == png_ptr->trans_color.gray)
+                        {
+                           *sp &= (png_byte)((0x3f3f >> (6 - shift)) & 0xff);
+                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                        }
+
+                        if (!shift)
+                        {
+                           shift = 6;
+                           sp++;
+                        }
+
+                        else
+                           shift -= 2;
+                     }
+                  }
+                  break;
+               }
+
+               case 4:
+               {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                  if (gamma_table != NULL)
+                  {
+                     sp = row;
+                     shift = 4;
+                     for (i = 0; i < row_width; i++)
+                     {
+                        if ((png_uint_16)((*sp >> shift) & 0x0f)
+                            == png_ptr->trans_color.gray)
+                        {
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                        }
+
+                        else
+                        {
+                           png_byte p = (png_byte)((*sp >> shift) & 0x0f);
+                           png_byte g = (png_byte)((gamma_table[p |
+                               (p << 4)] >> 4) & 0x0f);
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(g << shift);
+                        }
+
+                        if (!shift)
+                        {
+                           shift = 4;
+                           sp++;
+                        }
+
+                        else
+                           shift -= 4;
+                     }
+                  }
+
+                  else
+#endif
+                  {
+                     sp = row;
+                     shift = 4;
+                     for (i = 0; i < row_width; i++)
+                     {
+                        if ((png_uint_16)((*sp >> shift) & 0x0f)
+                            == png_ptr->trans_color.gray)
+                        {
+                           *sp &= (png_byte)((0xf0f >> (4 - shift)) & 0xff);
+                           *sp |= (png_byte)(png_ptr->background.gray << shift);
+                        }
+
+                        if (!shift)
+                        {
+                           shift = 4;
+                           sp++;
+                        }
+
+                        else
+                           shift -= 4;
+                     }
+                  }
+                  break;
+               }
+
+               case 8:
+               {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                  if (gamma_table != NULL)
+                  {
+                     sp = row;
+                     for (i = 0; i < row_width; i++, sp++)
+                     {
+                        if (*sp == png_ptr->trans_color.gray)
+                           *sp = (png_byte)png_ptr->background.gray;
+
+                        else
+                           *sp = gamma_table[*sp];
+                     }
+                  }
+                  else
+#endif
+                  {
+                     sp = row;
+                     for (i = 0; i < row_width; i++, sp++)
+                     {
+                        if (*sp == png_ptr->trans_color.gray)
+                           *sp = (png_byte)png_ptr->background.gray;
+                     }
+                  }
+                  break;
+               }
+
+               case 16:
+               {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+                  if (gamma_16 != NULL)
+                  {
+                     sp = row;
+                     for (i = 0; i < row_width; i++, sp += 2)
+                     {
+                        png_uint_16 v;
+
+                        v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+
+                        if (v == png_ptr->trans_color.gray)
+                        {
+                           /* Background is already in screen gamma */
+                           *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                        }
+
+                        else
+                        {
+                           v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+                           *sp = (png_byte)((v >> 8) & 0xff);
+                           *(sp + 1) = (png_byte)(v & 0xff);
+                        }
+                     }
+                  }
+                  else
+#endif
+                  {
+                     sp = row;
+                     for (i = 0; i < row_width; i++, sp += 2)
+                     {
+                        png_uint_16 v;
+
+                        v = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+
+                        if (v == png_ptr->trans_color.gray)
+                        {
+                           *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);
+                           *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                        }
+                     }
+                  }
+                  break;
+               }
+
+               default:
+                  break;
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_RGB:
+         {
+            if (row_info->bit_depth == 8)
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_table != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 3)
+                  {
+                     if (*sp == png_ptr->trans_color.red &&
+                         *(sp + 1) == png_ptr->trans_color.green &&
+                         *(sp + 2) == png_ptr->trans_color.blue)
+                     {
+                        *sp = (png_byte)png_ptr->background.red;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                     }
+
+                     else
+                     {
+                        *sp = gamma_table[*sp];
+                        *(sp + 1) = gamma_table[*(sp + 1)];
+                        *(sp + 2) = gamma_table[*(sp + 2)];
+                     }
+                  }
+               }
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 3)
+                  {
+                     if (*sp == png_ptr->trans_color.red &&
+                         *(sp + 1) == png_ptr->trans_color.green &&
+                         *(sp + 2) == png_ptr->trans_color.blue)
+                     {
+                        *sp = (png_byte)png_ptr->background.red;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                     }
+                  }
+               }
+            }
+            else /* if (row_info->bit_depth == 16) */
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_16 != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 6)
+                  {
+                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+
+                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
+                         + *(sp + 3));
+
+                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
+                         + *(sp + 5));
+
+                     if (r == png_ptr->trans_color.red &&
+                         g == png_ptr->trans_color.green &&
+                         b == png_ptr->trans_color.blue)
+                     {
+                        /* Background is already in screen gamma */
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+
+                     else
+                     {
+                        png_uint_16 v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+                        *sp = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
+
+                        v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(v & 0xff);
+
+                        v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(v & 0xff);
+                     }
+                  }
+               }
+
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 6)
+                  {
+                     png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+
+                     png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
+                         + *(sp + 3));
+
+                     png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
+                         + *(sp + 5));
+
+                     if (r == png_ptr->trans_color.red &&
+                         g == png_ptr->trans_color.green &&
+                         b == png_ptr->trans_color.blue)
+                     {
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+                  }
+               }
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_GRAY_ALPHA:
+         {
+            if (row_info->bit_depth == 8)
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
+                   gamma_table != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 2)
+                  {
+                     png_uint_16 a = *(sp + 1);
+
+                     if (a == 0xff)
+                        *sp = gamma_table[*sp];
+
+                     else if (a == 0)
+                     {
+                        /* Background is already in screen gamma */
+                        *sp = (png_byte)png_ptr->background.gray;
+                     }
+
+                     else
+                     {
+                        png_byte v, w;
+
+                        v = gamma_to_1[*sp];
+                        png_composite(w, v, a, png_ptr->background_1.gray);
+                        if (!optimize)
+                           w = gamma_from_1[w];
+                        *sp = w;
+                     }
+                  }
+               }
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 2)
+                  {
+                     png_byte a = *(sp + 1);
+
+                     if (a == 0)
+                        *sp = (png_byte)png_ptr->background.gray;
+
+                     else if (a < 0xff)
+                        png_composite(*sp, *sp, a, png_ptr->background_1.gray);
+                  }
+               }
+            }
+            else /* if (png_ptr->bit_depth == 16) */
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
+                   gamma_16_to_1 != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
+                  {
+                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
+                         + *(sp + 3));
+
+                     if (a == (png_uint_16)0xffff)
+                     {
+                        png_uint_16 v;
+
+                        v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+                        *sp = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
+                     }
+
+                     else if (a == 0)
+                     {
+                        /* Background is already in screen gamma */
+                        *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                     }
+
+                     else
+                     {
+                        png_uint_16 g, v, w;
+
+                        g = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+                        png_composite_16(v, g, a, png_ptr->background_1.gray);
+                        if (optimize)
+                           w = v;
+                        else
+                           w = gamma_16_from_1[(v&0xff) >> gamma_shift][v >> 8];
+                        *sp = (png_byte)((w >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(w & 0xff);
+                     }
+                  }
+               }
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
+                  {
+                     png_uint_16 a = (png_uint_16)(((*(sp + 2)) << 8)
+                         + *(sp + 3));
+
+                     if (a == 0)
+                     {
+                        *sp = (png_byte)((png_ptr->background.gray >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.gray & 0xff);
+                     }
+
+                     else if (a < 0xffff)
+                     {
+                        png_uint_16 g, v;
+
+                        g = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+                        png_composite_16(v, g, a, png_ptr->background_1.gray);
+                        *sp = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
+                     }
+                  }
+               }
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_RGB_ALPHA:
+         {
+            if (row_info->bit_depth == 8)
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_to_1 != NULL && gamma_from_1 != NULL &&
+                   gamma_table != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
+                  {
+                     png_byte a = *(sp + 3);
+
+                     if (a == 0xff)
+                     {
+                        *sp = gamma_table[*sp];
+                        *(sp + 1) = gamma_table[*(sp + 1)];
+                        *(sp + 2) = gamma_table[*(sp + 2)];
+                     }
+
+                     else if (a == 0)
+                     {
+                        /* Background is already in screen gamma */
+                        *sp = (png_byte)png_ptr->background.red;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                     }
+
+                     else
+                     {
+                        png_byte v, w;
+
+                        v = gamma_to_1[*sp];
+                        png_composite(w, v, a, png_ptr->background_1.red);
+                        if (!optimize) w = gamma_from_1[w];
+                        *sp = w;
+
+                        v = gamma_to_1[*(sp + 1)];
+                        png_composite(w, v, a, png_ptr->background_1.green);
+                        if (!optimize) w = gamma_from_1[w];
+                        *(sp + 1) = w;
+
+                        v = gamma_to_1[*(sp + 2)];
+                        png_composite(w, v, a, png_ptr->background_1.blue);
+                        if (!optimize) w = gamma_from_1[w];
+                        *(sp + 2) = w;
+                     }
+                  }
+               }
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 4)
+                  {
+                     png_byte a = *(sp + 3);
+
+                     if (a == 0)
+                     {
+                        *sp = (png_byte)png_ptr->background.red;
+                        *(sp + 1) = (png_byte)png_ptr->background.green;
+                        *(sp + 2) = (png_byte)png_ptr->background.blue;
+                     }
+
+                     else if (a < 0xff)
+                     {
+                        png_composite(*sp, *sp, a, png_ptr->background.red);
+
+                        png_composite(*(sp + 1), *(sp + 1), a,
+                            png_ptr->background.green);
+
+                        png_composite(*(sp + 2), *(sp + 2), a,
+                            png_ptr->background.blue);
+                     }
+                  }
+               }
+            }
+            else /* if (row_info->bit_depth == 16) */
+            {
+#ifdef PNG_READ_GAMMA_SUPPORTED
+               if (gamma_16 != NULL && gamma_16_from_1 != NULL &&
+                   gamma_16_to_1 != NULL)
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 8)
+                  {
+                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
+                         << 8) + (png_uint_16)(*(sp + 7)));
+
+                     if (a == (png_uint_16)0xffff)
+                     {
+                        png_uint_16 v;
+
+                        v = gamma_16[*(sp + 1) >> gamma_shift][*sp];
+                        *sp = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
+
+                        v = gamma_16[*(sp + 3) >> gamma_shift][*(sp + 2)];
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(v & 0xff);
+
+                        v = gamma_16[*(sp + 5) >> gamma_shift][*(sp + 4)];
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(v & 0xff);
+                     }
+
+                     else if (a == 0)
+                     {
+                        /* Background is already in screen gamma */
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+
+                     else
+                     {
+                        png_uint_16 v, w;
+
+                        v = gamma_16_to_1[*(sp + 1) >> gamma_shift][*sp];
+                        png_composite_16(w, v, a, png_ptr->background_1.red);
+                        if (!optimize)
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+                        *sp = (png_byte)((w >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(w & 0xff);
+
+                        v = gamma_16_to_1[*(sp + 3) >> gamma_shift][*(sp + 2)];
+                        png_composite_16(w, v, a, png_ptr->background_1.green);
+                        if (!optimize)
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+
+                        *(sp + 2) = (png_byte)((w >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(w & 0xff);
+
+                        v = gamma_16_to_1[*(sp + 5) >> gamma_shift][*(sp + 4)];
+                        png_composite_16(w, v, a, png_ptr->background_1.blue);
+                        if (!optimize)
+                           w = gamma_16_from_1[((w&0xff) >> gamma_shift)][w >> 8];
+
+                        *(sp + 4) = (png_byte)((w >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(w & 0xff);
+                     }
+                  }
+               }
+
+               else
+#endif
+               {
+                  sp = row;
+                  for (i = 0; i < row_width; i++, sp += 8)
+                  {
+                     png_uint_16 a = (png_uint_16)(((png_uint_16)(*(sp + 6))
+                         << 8) + (png_uint_16)(*(sp + 7)));
+
+                     if (a == 0)
+                     {
+                        *sp = (png_byte)((png_ptr->background.red >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(png_ptr->background.red & 0xff);
+                        *(sp + 2) = (png_byte)((png_ptr->background.green >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(png_ptr->background.green & 0xff);
+                        *(sp + 4) = (png_byte)((png_ptr->background.blue >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(png_ptr->background.blue & 0xff);
+                     }
+
+                     else if (a < 0xffff)
+                     {
+                        png_uint_16 v;
+
+                        png_uint_16 r = (png_uint_16)(((*sp) << 8) + *(sp + 1));
+                        png_uint_16 g = (png_uint_16)(((*(sp + 2)) << 8)
+                            + *(sp + 3));
+                        png_uint_16 b = (png_uint_16)(((*(sp + 4)) << 8)
+                            + *(sp + 5));
+
+                        png_composite_16(v, r, a, png_ptr->background.red);
+                        *sp = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 1) = (png_byte)(v & 0xff);
+
+                        png_composite_16(v, g, a, png_ptr->background.green);
+                        *(sp + 2) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 3) = (png_byte)(v & 0xff);
+
+                        png_composite_16(v, b, a, png_ptr->background.blue);
+                        *(sp + 4) = (png_byte)((v >> 8) & 0xff);
+                        *(sp + 5) = (png_byte)(v & 0xff);
+                     }
+                  }
+               }
+            }
+            break;
+         }
+
+         default:
+            break;
+      }
+   }
+}
+#endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+/* Gamma correct the image, avoiding the alpha channel.  Make sure
+ * you do this after you deal with the transparency issue on grayscale
+ * or RGB images. If your bit depth is 8, use gamma_table, if it
+ * is 16, use gamma_16_table and gamma_shift.  Build these with
+ * build_gamma_table().
+ */
+void /* PRIVATE */
+png_do_gamma(png_row_infop row_info, png_bytep row, png_structp png_ptr)
+{
+   png_const_bytep gamma_table = png_ptr->gamma_table;
+   png_const_uint_16pp gamma_16_table = png_ptr->gamma_16_table;
+   int gamma_shift = png_ptr->gamma_shift;
+
+   png_bytep sp;
+   png_uint_32 i;
+   png_uint_32 row_width=row_info->width;
+
+   png_debug(1, "in png_do_gamma");
+
+   if (((row_info->bit_depth <= 8 && gamma_table != NULL) ||
+       (row_info->bit_depth == 16 && gamma_16_table != NULL)))
+   {
+      switch (row_info->color_type)
+      {
+         case PNG_COLOR_TYPE_RGB:
+         {
+            if (row_info->bit_depth == 8)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  *sp = gamma_table[*sp];
+                  sp++;
+                  *sp = gamma_table[*sp];
+                  sp++;
+                  *sp = gamma_table[*sp];
+                  sp++;
+               }
+            }
+
+            else /* if (row_info->bit_depth == 16) */
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 v;
+
+                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+
+                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+
+                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+               }
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_RGB_ALPHA:
+         {
+            if (row_info->bit_depth == 8)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  *sp = gamma_table[*sp];
+                  sp++;
+
+                  *sp = gamma_table[*sp];
+                  sp++;
+
+                  *sp = gamma_table[*sp];
+                  sp++;
+
+                  sp++;
+               }
+            }
+
+            else /* if (row_info->bit_depth == 16) */
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+
+                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+
+                  v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 4;
+               }
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_GRAY_ALPHA:
+         {
+            if (row_info->bit_depth == 8)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  *sp = gamma_table[*sp];
+                  sp += 2;
+               }
+            }
+
+            else /* if (row_info->bit_depth == 16) */
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 4;
+               }
+            }
+            break;
+         }
+
+         case PNG_COLOR_TYPE_GRAY:
+         {
+            if (row_info->bit_depth == 2)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i += 4)
+               {
+                  int a = *sp & 0xc0;
+                  int b = *sp & 0x30;
+                  int c = *sp & 0x0c;
+                  int d = *sp & 0x03;
+
+                  *sp = (png_byte)(
+                      ((((int)gamma_table[a|(a>>2)|(a>>4)|(a>>6)])   ) & 0xc0)|
+                      ((((int)gamma_table[(b<<2)|b|(b>>2)|(b>>4)])>>2) & 0x30)|
+                      ((((int)gamma_table[(c<<4)|(c<<2)|c|(c>>2)])>>4) & 0x0c)|
+                      ((((int)gamma_table[(d<<6)|(d<<4)|(d<<2)|d])>>6) ));
+                  sp++;
+               }
+            }
+
+            if (row_info->bit_depth == 4)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i += 2)
+               {
+                  int msb = *sp & 0xf0;
+                  int lsb = *sp & 0x0f;
+
+                  *sp = (png_byte)((((int)gamma_table[msb | (msb >> 4)]) & 0xf0)
+                      | (((int)gamma_table[(lsb << 4) | lsb]) >> 4));
+                  sp++;
+               }
+            }
+
+            else if (row_info->bit_depth == 8)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  *sp = gamma_table[*sp];
+                  sp++;
+               }
+            }
+
+            else if (row_info->bit_depth == 16)
+            {
+               sp = row;
+               for (i = 0; i < row_width; i++)
+               {
+                  png_uint_16 v = gamma_16_table[*(sp + 1) >> gamma_shift][*sp];
+                  *sp = (png_byte)((v >> 8) & 0xff);
+                  *(sp + 1) = (png_byte)(v & 0xff);
+                  sp += 2;
+               }
+            }
+            break;
+         }
+
+         default:
+            break;
+      }
+   }
+}
+#endif
+
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+/* Encode the alpha channel to the output gamma (the input channel is always
+ * linear.)  Called only with color types that have an alpha channel.  Needs the
+ * from_1 tables.
+ */
+void /* PRIVATE */
+png_do_encode_alpha(png_row_infop row_info, png_bytep row, png_structp png_ptr)
+{
+   png_uint_32 row_width = row_info->width;
+
+   png_debug(1, "in png_do_encode_alpha");
+
+   if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
+   {
+      if (row_info->bit_depth == 8)
+      {
+         PNG_CONST png_bytep table = png_ptr->gamma_from_1;
+
+         if (table != NULL)
+         {
+            PNG_CONST int step =
+               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
+
+            /* The alpha channel is the last component: */
+            row += step - 1;
+
+            for (; row_width > 0; --row_width, row += step)
+               *row = table[*row];
+
+            return;
+         }
+      }
+
+      else if (row_info->bit_depth == 16)
+      {
+         PNG_CONST png_uint_16pp table = png_ptr->gamma_16_from_1;
+         PNG_CONST int gamma_shift = png_ptr->gamma_shift;
+
+         if (table != NULL)
+         {
+            PNG_CONST int step =
+               (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
+
+            /* The alpha channel is the last component: */
+            row += step - 2;
+
+            for (; row_width > 0; --row_width, row += step)
+            {
+               png_uint_16 v;
+
+               v = table[*(row + 1) >> gamma_shift][*row];
+               *row = (png_byte)((v >> 8) & 0xff);
+               *(row + 1) = (png_byte)(v & 0xff);
+            }
+
+            return;
+         }
+      }
+   }
+
+   /* Only get to here if called with a weird row_info; no harm has been done,
+    * so just issue a warning.
+    */
+   png_warning(png_ptr, "png_do_encode_alpha: unexpected call");
+}
+#endif
+
+#ifdef PNG_READ_EXPAND_SUPPORTED
+/* Expands a palette row to an RGB or RGBA row depending
+ * upon whether you supply trans and num_trans.
+ */
+void /* PRIVATE */
+png_do_expand_palette(png_row_infop row_info, png_bytep row,
+   png_const_colorp palette, png_const_bytep trans_alpha, int num_trans)
+{
+   int shift, value;
+   png_bytep sp, dp;
+   png_uint_32 i;
+   png_uint_32 row_width=row_info->width;
+
+   png_debug(1, "in png_do_expand_palette");
+
+   if (row_info->color_type == PNG_COLOR_TYPE_PALETTE)
+   {
+      if (row_info->bit_depth < 8)
+      {
+         switch (row_info->bit_depth)
+         {
+            case 1:
+            {
+               sp = row + (png_size_t)((row_width - 1) >> 3);
+               dp = row + (png_size_t)row_width - 1;
+               shift = 7 - (int)((row_width + 7) & 0x07);
+               for (i = 0; i < row_width; i++)
+               {
+                  if ((*sp >> shift) & 0x01)
+                     *dp = 1;
+
+                  else
+                     *dp = 0;
+
+                  if (shift == 7)
+                  {
+                     shift = 0;
+                     sp--;
+                  }
+
+                  else
+                     shift++;
+
+                  dp--;
+               }
+               break;
+            }
+
+            case 2:
+            {
+               sp = row + (png_size_t)((row_width - 1) >> 2);
+               dp = row + (png_size_t)row_width - 1;
+               shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+               for (i = 0; i < row_width; i++)
+               {
+                  value = (*sp >> shift) & 0x03;
+                  *dp = (png_byte)value;
+                  if (shift == 6)
+                  {
+                     shift = 0;
+                     sp--;
+                  }
+
+                  else
+                     shift += 2;
+
+                  dp--;
+               }
+               break;
+            }
+
+            case 4:
+            {
+               sp = row + (png_size_t)((row_width - 1) >> 1);
+               dp = row + (png_size_t)row_width - 1;
+               shift = (int)((row_width & 0x01) << 2);
+               for (i = 0; i < row_width; i++)
+               {
+                  value = (*sp >> shift) & 0x0f;
+                  *dp = (png_byte)value;
+                  if (shift == 4)
+                  {
+                     shift = 0;
+                     sp--;
+                  }
+
+                  else
+                     shift += 4;
+
+                  dp--;
+               }
+               break;
+            }
+
+            default:
+               break;
+         }
+         row_info->bit_depth = 8;
+         row_info->pixel_depth = 8;
+         row_info->rowbytes = row_width;
+      }
+
+      if (row_info->bit_depth == 8)
+      {
+         {
+            if (num_trans > 0)
+            {
+               sp = row + (png_size_t)row_width - 1;
+               dp = row + (png_size_t)(row_width << 2) - 1;
+
+               for (i = 0; i < row_width; i++)
+               {
+                  if ((int)(*sp) >= num_trans)
+                     *dp-- = 0xff;
+
+                  else
+                     *dp-- = trans_alpha[*sp];
+
+                  *dp-- = palette[*sp].blue;
+                  *dp-- = palette[*sp].green;
+                  *dp-- = palette[*sp].red;
+                  sp--;
+               }
+               row_info->bit_depth = 8;
+               row_info->pixel_depth = 32;
+               row_info->rowbytes = row_width * 4;
+               row_info->color_type = 6;
+               row_info->channels = 4;
+            }
+
+            else
+            {
+               sp = row + (png_size_t)row_width - 1;
+               dp = row + (png_size_t)(row_width * 3) - 1;
+
+               for (i = 0; i < row_width; i++)
+               {
+                  *dp-- = palette[*sp].blue;
+                  *dp-- = palette[*sp].green;
+                  *dp-- = palette[*sp].red;
+                  sp--;
+               }
+
+               row_info->bit_depth = 8;
+               row_info->pixel_depth = 24;
+               row_info->rowbytes = row_width * 3;
+               row_info->color_type = 2;
+               row_info->channels = 3;
+            }
+         }
+      }
+   }
+}
+
+/* If the bit depth < 8, it is expanded to 8.  Also, if the already
+ * expanded transparency value is supplied, an alpha channel is built.
+ */
+void /* PRIVATE */
+png_do_expand(png_row_infop row_info, png_bytep row,
+    png_const_color_16p trans_color)
+{
+   int shift, value;
+   png_bytep sp, dp;
+   png_uint_32 i;
+   png_uint_32 row_width=row_info->width;
+
+   png_debug(1, "in png_do_expand");
+
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_GRAY)
+      {
+         png_uint_16 gray = (png_uint_16)(trans_color ? trans_color->gray : 0);
+
+         if (row_info->bit_depth < 8)
+         {
+            switch (row_info->bit_depth)
+            {
+               case 1:
+               {
+                  gray = (png_uint_16)((gray & 0x01) * 0xff);
+                  sp = row + (png_size_t)((row_width - 1) >> 3);
+                  dp = row + (png_size_t)row_width - 1;
+                  shift = 7 - (int)((row_width + 7) & 0x07);
+                  for (i = 0; i < row_width; i++)
+                  {
+                     if ((*sp >> shift) & 0x01)
+                        *dp = 0xff;
+
+                     else
+                        *dp = 0;
+
+                     if (shift == 7)
+                     {
+                        shift = 0;
+                        sp--;
+                     }
+
+                     else
+                        shift++;
+
+                     dp--;
+                  }
+                  break;
+               }
+
+               case 2:
+               {
+                  gray = (png_uint_16)((gray & 0x03) * 0x55);
+                  sp = row + (png_size_t)((row_width - 1) >> 2);
+                  dp = row + (png_size_t)row_width - 1;
+                  shift = (int)((3 - ((row_width + 3) & 0x03)) << 1);
+                  for (i = 0; i < row_width; i++)
+                  {
+                     value = (*sp >> shift) & 0x03;
+                     *dp = (png_byte)(value | (value << 2) | (value << 4) |
+                        (value << 6));
+                     if (shift == 6)
+                     {
+                        shift = 0;
+                        sp--;
+                     }
+
+                     else
+                        shift += 2;
+
+                     dp--;
+                  }
+                  break;
+               }
+
+               case 4:
+               {
+                  gray = (png_uint_16)((gray & 0x0f) * 0x11);
+                  sp = row + (png_size_t)((row_width - 1) >> 1);
+                  dp = row + (png_size_t)row_width - 1;
+                  shift = (int)((1 - ((row_width + 1) & 0x01)) << 2);
+                  for (i = 0; i < row_width; i++)
+                  {
+                     value = (*sp >> shift) & 0x0f;
+                     *dp = (png_byte)(value | (value << 4));
+                     if (shift == 4)
+                     {
+                        shift = 0;
+                        sp--;
+                     }
+
+                     else
+                        shift = 4;
+
+                     dp--;
+                  }
+                  break;
+               }
+
+               default:
+                  break;
+            }
+
+            row_info->bit_depth = 8;
+            row_info->pixel_depth = 8;
+            row_info->rowbytes = row_width;
+         }
+
+         if (trans_color != NULL)
+         {
+            if (row_info->bit_depth == 8)
+            {
+               gray = gray & 0xff;
+               sp = row + (png_size_t)row_width - 1;
+               dp = row + (png_size_t)(row_width << 1) - 1;
+
+               for (i = 0; i < row_width; i++)
+               {
+                  if (*sp == gray)
+                     *dp-- = 0;
+
+                  else
+                     *dp-- = 0xff;
+
+                  *dp-- = *sp--;
+               }
+            }
+
+            else if (row_info->bit_depth == 16)
+            {
+               png_byte gray_high = (png_byte)((gray >> 8) & 0xff);
+               png_byte gray_low = (png_byte)(gray & 0xff);
+               sp = row + row_info->rowbytes - 1;
+               dp = row + (row_info->rowbytes << 1) - 1;
+               for (i = 0; i < row_width; i++)
+               {
+                  if (*(sp - 1) == gray_high && *(sp) == gray_low)
+                  {
+                     *dp-- = 0;
+                     *dp-- = 0;
+                  }
+
+                  else
+                  {
+                     *dp-- = 0xff;
+                     *dp-- = 0xff;
+                  }
+
+                  *dp-- = *sp--;
+                  *dp-- = *sp--;
+               }
+            }
+
+            row_info->color_type = PNG_COLOR_TYPE_GRAY_ALPHA;
+            row_info->channels = 2;
+            row_info->pixel_depth = (png_byte)(row_info->bit_depth << 1);
+            row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
+               row_width);
+         }
+      }
+      else if (row_info->color_type == PNG_COLOR_TYPE_RGB && trans_color)
+      {
+         if (row_info->bit_depth == 8)
+         {
+            png_byte red = (png_byte)(trans_color->red & 0xff);
+            png_byte green = (png_byte)(trans_color->green & 0xff);
+            png_byte blue = (png_byte)(trans_color->blue & 0xff);
+            sp = row + (png_size_t)row_info->rowbytes - 1;
+            dp = row + (png_size_t)(row_width << 2) - 1;
+            for (i = 0; i < row_width; i++)
+            {
+               if (*(sp - 2) == red && *(sp - 1) == green && *(sp) == blue)
+                  *dp-- = 0;
+
+               else
+                  *dp-- = 0xff;
+
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+            }
+         }
+         else if (row_info->bit_depth == 16)
+         {
+            png_byte red_high = (png_byte)((trans_color->red >> 8) & 0xff);
+            png_byte green_high = (png_byte)((trans_color->green >> 8) & 0xff);
+            png_byte blue_high = (png_byte)((trans_color->blue >> 8) & 0xff);
+            png_byte red_low = (png_byte)(trans_color->red & 0xff);
+            png_byte green_low = (png_byte)(trans_color->green & 0xff);
+            png_byte blue_low = (png_byte)(trans_color->blue & 0xff);
+            sp = row + row_info->rowbytes - 1;
+            dp = row + (png_size_t)(row_width << 3) - 1;
+            for (i = 0; i < row_width; i++)
+            {
+               if (*(sp - 5) == red_high &&
+                   *(sp - 4) == red_low &&
+                   *(sp - 3) == green_high &&
+                   *(sp - 2) == green_low &&
+                   *(sp - 1) == blue_high &&
+                   *(sp    ) == blue_low)
+               {
+                  *dp-- = 0;
+                  *dp-- = 0;
+               }
+
+               else
+               {
+                  *dp-- = 0xff;
+                  *dp-- = 0xff;
+               }
+
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+               *dp-- = *sp--;
+            }
+         }
+         row_info->color_type = PNG_COLOR_TYPE_RGB_ALPHA;
+         row_info->channels = 4;
+         row_info->pixel_depth = (png_byte)(row_info->bit_depth << 2);
+         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
+   }
+}
+#endif
+
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
+/* If the bit depth is 8 and the color type is not a palette type expand the
+ * whole row to 16 bits.  Has no effect otherwise.
+ */
+void /* PRIVATE */
+png_do_expand_16(png_row_infop row_info, png_bytep row)
+{
+   if (row_info->bit_depth == 8 &&
+      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
+   {
+      /* The row have a sequence of bytes containing [0..255] and we need
+       * to turn it into another row containing [0..65535], to do this we
+       * calculate:
+       *
+       *  (input / 255) * 65535
+       *
+       *  Which happens to be exactly input * 257 and this can be achieved
+       *  simply by byte replication in place (copying backwards).
+       */
+      png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
+      png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */
+      while (dp > sp)
+         dp[-2] = dp[-1] = *--sp, dp -= 2;
+
+      row_info->rowbytes *= 2;
+      row_info->bit_depth = 16;
+      row_info->pixel_depth = (png_byte)(row_info->channels * 16);
+   }
+}
+#endif
+
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+void /* PRIVATE */
+png_do_quantize(png_row_infop row_info, png_bytep row,
+    png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
+{
+   png_bytep sp, dp;
+   png_uint_32 i;
+   png_uint_32 row_width=row_info->width;
+
+   png_debug(1, "in png_do_quantize");
+
+   if (row_info->bit_depth == 8)
+   {
+      if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
+      {
+         int r, g, b, p;
+         sp = row;
+         dp = row;
+         for (i = 0; i < row_width; i++)
+         {
+            r = *sp++;
+            g = *sp++;
+            b = *sp++;
+
+            /* This looks real messy, but the compiler will reduce
+             * it down to a reasonable formula.  For example, with
+             * 5 bits per color, we get:
+             * p = (((r >> 3) & 0x1f) << 10) |
+             *    (((g >> 3) & 0x1f) << 5) |
+             *    ((b >> 3) & 0x1f);
+             */
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+                (PNG_QUANTIZE_BLUE_BITS)) |
+                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+
+            *dp++ = palette_lookup[p];
+         }
+
+         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
+         row_info->channels = 1;
+         row_info->pixel_depth = row_info->bit_depth;
+         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
+
+      else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
+         palette_lookup != NULL)
+      {
+         int r, g, b, p;
+         sp = row;
+         dp = row;
+         for (i = 0; i < row_width; i++)
+         {
+            r = *sp++;
+            g = *sp++;
+            b = *sp++;
+            sp++;
+
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+                (PNG_QUANTIZE_BLUE_BITS)) |
+                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
+
+            *dp++ = palette_lookup[p];
+         }
+
+         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
+         row_info->channels = 1;
+         row_info->pixel_depth = row_info->bit_depth;
+         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
+      }
+
+      else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
+         quantize_lookup)
+      {
+         sp = row;
+
+         for (i = 0; i < row_width; i++, sp++)
+         {
+            *sp = quantize_lookup[*sp];
+         }
+      }
+   }
+}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
+#endif /* PNG_READ_TRANSFORMS_SUPPORTED */
+
+#ifdef PNG_MNG_FEATURES_SUPPORTED
+/* Undoes intrapixel differencing  */
+void /* PRIVATE */
+png_do_read_intrapixel(png_row_infop row_info, png_bytep row)
+{
+   png_debug(1, "in png_do_read_intrapixel");
+
+   if (
+       (row_info->color_type & PNG_COLOR_MASK_COLOR))
+   {
+      int bytes_per_pixel;
+      png_uint_32 row_width = row_info->width;
+
+      if (row_info->bit_depth == 8)
+      {
+         png_bytep rp;
+         png_uint_32 i;
+
+         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+            bytes_per_pixel = 3;
+
+         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+            bytes_per_pixel = 4;
+
+         else
+            return;
+
+         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
+            *(rp) = (png_byte)((256 + *rp + *(rp + 1)) & 0xff);
+            *(rp+2) = (png_byte)((256 + *(rp + 2) + *(rp + 1)) & 0xff);
+         }
+      }
+      else if (row_info->bit_depth == 16)
+      {
+         png_bytep rp;
+         png_uint_32 i;
+
+         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
+            bytes_per_pixel = 6;
+
+         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
+            bytes_per_pixel = 8;
+
+         else
+            return;
+
+         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
+         {
+            png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);
+            png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);
+            png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);
+            png_uint_32 red  = (s0 + s1 + 65536) & 0xffff;
+            png_uint_32 blue = (s2 + s1 + 65536) & 0xffff;
+            *(rp    ) = (png_byte)((red >> 8) & 0xff);
+            *(rp + 1) = (png_byte)(red & 0xff);
+            *(rp + 4) = (png_byte)((blue >> 8) & 0xff);
+            *(rp + 5) = (png_byte)(blue & 0xff);
+         }
+      }
+   }
+}
+#endif /* PNG_MNG_FEATURES_SUPPORTED */
+#endif /* PNG_READ_SUPPORTED */