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Diffstat (limited to 'libraries/irrlicht-1.8/source/Irrlicht/libpng/libpng.3')
-rw-r--r-- | libraries/irrlicht-1.8/source/Irrlicht/libpng/libpng.3 | 5952 |
1 files changed, 0 insertions, 5952 deletions
diff --git a/libraries/irrlicht-1.8/source/Irrlicht/libpng/libpng.3 b/libraries/irrlicht-1.8/source/Irrlicht/libpng/libpng.3 deleted file mode 100644 index 14b1567..0000000 --- a/libraries/irrlicht-1.8/source/Irrlicht/libpng/libpng.3 +++ /dev/null | |||
@@ -1,5952 +0,0 @@ | |||
1 | .TH LIBPNG 3 "February 18, 2012" | ||
2 | .SH NAME | ||
3 | libpng \- Portable Network Graphics (PNG) Reference Library 1.5.9 | ||
4 | .SH SYNOPSIS | ||
5 | \fI\fB | ||
6 | |||
7 | \fB#include <png.h>\fP | ||
8 | |||
9 | \fI\fB | ||
10 | |||
11 | \fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP | ||
12 | |||
13 | \fI\fB | ||
14 | |||
15 | \fBvoid png_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP | ||
16 | |||
17 | \fI\fB | ||
18 | |||
19 | \fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP | ||
20 | |||
21 | \fI\fB | ||
22 | |||
23 | \fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP | ||
24 | |||
25 | \fI\fB | ||
26 | |||
27 | \fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP | ||
28 | |||
29 | \fI\fB | ||
30 | |||
31 | \fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP | ||
32 | |||
33 | \fI\fB | ||
34 | |||
35 | \fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP | ||
36 | |||
37 | \fI\fB | ||
38 | |||
39 | \fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP | ||
40 | |||
41 | \fI\fB | ||
42 | |||
43 | \fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP | ||
44 | |||
45 | \fI\fB | ||
46 | |||
47 | \fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP | ||
48 | |||
49 | \fI\fB | ||
50 | |||
51 | \fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP | ||
52 | |||
53 | \fI\fB | ||
54 | |||
55 | \fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP | ||
56 | |||
57 | \fI\fB | ||
58 | |||
59 | \fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP | ||
60 | |||
61 | \fI\fB | ||
62 | |||
63 | \fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP | ||
64 | |||
65 | \fI\fB | ||
66 | |||
67 | \fBpng_structp png_create_write_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP | ||
68 | |||
69 | \fI\fB | ||
70 | |||
71 | \fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask)\fP\fB);\fP | ||
72 | |||
73 | \fI\fB | ||
74 | |||
75 | \fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP | ||
76 | |||
77 | \fI\fB | ||
78 | |||
79 | \fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP | ||
80 | |||
81 | \fI\fB | ||
82 | |||
83 | \fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP | ||
84 | |||
85 | \fI\fB | ||
86 | |||
87 | \fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP | ||
88 | |||
89 | \fI\fB | ||
90 | |||
91 | \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP | ||
92 | |||
93 | \fI\fB | ||
94 | |||
95 | \fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP | ||
96 | |||
97 | \fI\fB | ||
98 | |||
99 | \fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP | ||
100 | |||
101 | \fI\fB | ||
102 | |||
103 | \fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP | ||
104 | |||
105 | \fI\fB | ||
106 | |||
107 | \fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP | ||
108 | |||
109 | \fI\fB | ||
110 | |||
111 | \fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
112 | |||
113 | \fI\fB | ||
114 | |||
115 | \fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP | ||
116 | |||
117 | \fI\fB | ||
118 | |||
119 | \fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
120 | |||
121 | \fI\fB | ||
122 | |||
123 | \fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP | ||
124 | |||
125 | \fI\fB | ||
126 | |||
127 | \fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP | ||
128 | |||
129 | \fI\fB | ||
130 | |||
131 | \fBpng_uint_32 png_get_cHRM_XYZ (png_structp \fIpng_ptr, | ||
132 | |||
133 | \fBpng_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*red_X\fP\fB, double \fP\fI*red_Y\fP\fB, double \fI*red_Z, | ||
134 | |||
135 | \fBdouble \fP\fI*green_X\fP\fB, double \fP\fI*green_Y\fP\fB, double \fP\fI*green_Z\fP\fB, double \fI*blue_X, | ||
136 | |||
137 | \fBdouble \fP\fI*blue_Y\fP\fB, double \fI*blue_Z\fP\fB);\fP | ||
138 | |||
139 | \fI\fB | ||
140 | |||
141 | \fBpng_uint_32 png_get_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fI*int_red_X\fP\fB, png_fixed_point \fP\fI*int_red_Y\fP\fB, png_fixed_point \fP\fI*int_red_Z\fP\fB, png_fixed_point \fP\fI*int_green_X\fP\fB, png_fixed_point \fP\fI*int_green_Y\fP\fB, png_fixed_point \fP\fI*int_green_Z\fP\fB, png_fixed_point \fP\fI*int_blue_X\fP\fB, png_fixed_point \fP\fI*int_blue_Y\fP\fB, png_fixed_point \fI*int_blue_Z\fP\fB);\fP | ||
142 | |||
143 | \fI\fB | ||
144 | |||
145 | \fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
146 | |||
147 | \fI\fB | ||
148 | |||
149 | \fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
150 | |||
151 | \fI\fB | ||
152 | |||
153 | \fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
154 | |||
155 | \fI\fB | ||
156 | |||
157 | \fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
158 | |||
159 | \fI\fB | ||
160 | |||
161 | \fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
162 | |||
163 | \fI\fB | ||
164 | |||
165 | \fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
166 | |||
167 | \fI\fB | ||
168 | |||
169 | \fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP | ||
170 | |||
171 | \fI\fB | ||
172 | |||
173 | \fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP | ||
174 | |||
175 | \fI\fB | ||
176 | |||
177 | \fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
178 | |||
179 | \fI\fB | ||
180 | |||
181 | \fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
182 | |||
183 | \fI\fB | ||
184 | |||
185 | \fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP | ||
186 | |||
187 | \fI\fB | ||
188 | |||
189 | \fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP | ||
190 | |||
191 | \fI\fB | ||
192 | |||
193 | \fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
194 | |||
195 | \fI\fB | ||
196 | |||
197 | \fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
198 | |||
199 | \fI\fB | ||
200 | |||
201 | \fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP | ||
202 | |||
203 | \fI\fB | ||
204 | |||
205 | \fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP | ||
206 | |||
207 | \fI\fB | ||
208 | |||
209 | \fBpng_uint_32 png_get_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*width\fP\fB, png_uint_32 \fP\fI*height\fP\fB, int \fP\fI*bit_depth\fP\fB, int \fP\fI*color_type\fP\fB, int \fP\fI*interlace_type\fP\fB, int \fP\fI*compression_type\fP\fB, int \fI*filter_type\fP\fB);\fP | ||
210 | |||
211 | \fI\fB | ||
212 | |||
213 | \fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
214 | |||
215 | \fI\fB | ||
216 | |||
217 | \fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
218 | |||
219 | \fI\fB | ||
220 | |||
221 | \fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP | ||
222 | |||
223 | \fI\fB | ||
224 | |||
225 | \fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
226 | |||
227 | \fI\fB | ||
228 | |||
229 | \fBpng_const_bytep png_get_io_chunk_name (png_structp \fIpng_ptr\fP\fB);\fP | ||
230 | |||
231 | \fI\fB | ||
232 | |||
233 | \fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
234 | |||
235 | \fI\fB | ||
236 | |||
237 | \fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP | ||
238 | |||
239 | \fI\fB | ||
240 | |||
241 | \fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP | ||
242 | |||
243 | \fI\fB | ||
244 | |||
245 | \fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
246 | |||
247 | \fI\fB | ||
248 | |||
249 | \fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
250 | |||
251 | \fI\fB | ||
252 | |||
253 | \fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP | ||
254 | |||
255 | \fI\fB | ||
256 | |||
257 | \fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP | ||
258 | |||
259 | \fI\fB | ||
260 | |||
261 | \fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP | ||
262 | |||
263 | \fI\fB | ||
264 | |||
265 | \fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
266 | |||
267 | \fI\fB | ||
268 | |||
269 | \fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP | ||
270 | |||
271 | \fI\fB | ||
272 | |||
273 | \fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
274 | |||
275 | \fI\fB | ||
276 | |||
277 | \fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
278 | |||
279 | \fI\fB | ||
280 | |||
281 | \fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
282 | |||
283 | \fI\fB | ||
284 | |||
285 | \fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
286 | |||
287 | \fI\fB | ||
288 | |||
289 | \fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP | ||
290 | |||
291 | \fI\fB | ||
292 | |||
293 | \fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr) | ||
294 | |||
295 | \fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
296 | |||
297 | \fI\fB | ||
298 | |||
299 | \fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
300 | |||
301 | \fI\fB | ||
302 | |||
303 | \fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP | ||
304 | |||
305 | \fI\fB | ||
306 | |||
307 | \fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP | ||
308 | |||
309 | \fI\fB | ||
310 | |||
311 | \fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP | ||
312 | |||
313 | \fI\fB | ||
314 | |||
315 | \fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP | ||
316 | |||
317 | \fI\fB | ||
318 | |||
319 | \fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
320 | |||
321 | \fI\fB | ||
322 | |||
323 | \fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP | ||
324 | |||
325 | \fI\fB | ||
326 | |||
327 | \fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP | ||
328 | |||
329 | \fI\fB | ||
330 | |||
331 | \fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP | ||
332 | |||
333 | \fI\fB | ||
334 | |||
335 | \fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP | ||
336 | |||
337 | \fI\fB | ||
338 | |||
339 | \fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP | ||
340 | |||
341 | \fI\fB | ||
342 | |||
343 | \fB/* This function is really an inline macro. \fI*/ | ||
344 | |||
345 | \fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP | ||
346 | |||
347 | \fI\fB | ||
348 | |||
349 | \fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP | ||
350 | |||
351 | \fI\fB | ||
352 | |||
353 | \fB/* This function is really an inline macro. \fI*/ | ||
354 | |||
355 | \fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP | ||
356 | |||
357 | \fI\fB | ||
358 | |||
359 | \fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP | ||
360 | |||
361 | \fI\fB | ||
362 | |||
363 | \fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
364 | |||
365 | \fI\fB | ||
366 | |||
367 | \fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
368 | |||
369 | \fI\fB | ||
370 | |||
371 | \fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
372 | |||
373 | \fI\fB | ||
374 | |||
375 | \fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP | ||
376 | |||
377 | \fI\fB | ||
378 | |||
379 | \fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP | ||
380 | |||
381 | \fI\fB | ||
382 | |||
383 | \fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
384 | |||
385 | \fI\fB | ||
386 | |||
387 | \fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
388 | |||
389 | \fI\fB | ||
390 | |||
391 | \fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
392 | |||
393 | \fI\fB | ||
394 | |||
395 | \fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
396 | |||
397 | \fI\fB | ||
398 | |||
399 | \fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
400 | |||
401 | \fI\fB | ||
402 | |||
403 | \fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
404 | |||
405 | \fI\fB | ||
406 | |||
407 | \fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
408 | |||
409 | \fI\fB | ||
410 | |||
411 | \fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
412 | |||
413 | \fI\fB | ||
414 | |||
415 | \fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
416 | |||
417 | \fI\fB | ||
418 | |||
419 | \fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
420 | |||
421 | \fI\fB | ||
422 | |||
423 | \fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
424 | |||
425 | \fI\fB | ||
426 | |||
427 | \fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP | ||
428 | |||
429 | \fI\fB | ||
430 | |||
431 | \fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP | ||
432 | |||
433 | \fI\fB | ||
434 | |||
435 | \fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP | ||
436 | |||
437 | \fI\fB | ||
438 | |||
439 | \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP | ||
440 | |||
441 | \fI\fB | ||
442 | |||
443 | \fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP | ||
444 | |||
445 | \fI\fB | ||
446 | |||
447 | \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP | ||
448 | |||
449 | \fI\fB | ||
450 | |||
451 | \fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP | ||
452 | |||
453 | \fI\fB | ||
454 | |||
455 | \fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP | ||
456 | |||
457 | \fI\fB | ||
458 | |||
459 | \fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP | ||
460 | |||
461 | \fI\fB | ||
462 | |||
463 | \fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, png_size_t \fIbuffer_size\fP\fB);\fP | ||
464 | |||
465 | \fI\fB | ||
466 | |||
467 | \fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP | ||
468 | |||
469 | \fI\fB | ||
470 | |||
471 | \fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP | ||
472 | |||
473 | \fI\fB | ||
474 | |||
475 | \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP | ||
476 | |||
477 | \fI\fB | ||
478 | |||
479 | \fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
480 | |||
481 | \fI\fB | ||
482 | |||
483 | \fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP | ||
484 | |||
485 | \fI\fB | ||
486 | |||
487 | \fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
488 | |||
489 | \fI\fB | ||
490 | |||
491 | \fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP | ||
492 | |||
493 | \fI\fB | ||
494 | |||
495 | \fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP | ||
496 | |||
497 | \fI\fB | ||
498 | |||
499 | \fBvoid png_read_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_bytepp \fP\fIdisplay_row\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP | ||
500 | |||
501 | \fI\fB | ||
502 | |||
503 | \fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
504 | |||
505 | \fI\fB | ||
506 | |||
507 | \fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP | ||
508 | |||
509 | \fI\fB | ||
510 | |||
511 | \fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP | ||
512 | |||
513 | \fI\fB | ||
514 | |||
515 | \fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP | ||
516 | |||
517 | \fI\fB | ||
518 | |||
519 | \fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP | ||
520 | |||
521 | \fI\fB | ||
522 | |||
523 | \fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP | ||
524 | |||
525 | \fI\fB | ||
526 | |||
527 | \fBvoid png_set_alpha_mode (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, double \fIoutput_gamma\fP\fB);\fP | ||
528 | |||
529 | \fI\fB | ||
530 | |||
531 | \fBvoid png_set_alpha_mode_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, png_fixed_point \fIoutput_gamma\fP\fB);\fP | ||
532 | |||
533 | \fI\fB | ||
534 | |||
535 | \fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP | ||
536 | |||
537 | \fI\fB | ||
538 | |||
539 | \fBvoid png_set_background_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, png_uint_32 \fIbackground_gamma\fP\fB);\fP | ||
540 | |||
541 | \fI\fB | ||
542 | |||
543 | \fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP | ||
544 | |||
545 | \fI\fB | ||
546 | |||
547 | \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP | ||
548 | |||
549 | \fI\fB | ||
550 | |||
551 | \fBvoid png_set_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fIbackground\fP\fB);\fP | ||
552 | |||
553 | \fI\fB | ||
554 | |||
555 | \fBvoid png_set_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP | ||
556 | |||
557 | \fI\fB | ||
558 | |||
559 | \fBvoid png_set_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwhite_x\fP\fB, png_uint_32 \fP\fIwhite_y\fP\fB, png_uint_32 \fP\fIred_x\fP\fB, png_uint_32 \fP\fIred_y\fP\fB, png_uint_32 \fP\fIgreen_x\fP\fB, png_uint_32 \fP\fIgreen_y\fP\fB, png_uint_32 \fP\fIblue_x\fP\fB, png_uint_32 \fIblue_y\fP\fB);\fP | ||
560 | |||
561 | \fI\fB | ||
562 | |||
563 | \fBvoid png_set_cHRM_XYZ (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIred_X\fP\fB, double \fP\fIred_Y\fP\fB, double \fP\fIred_Z\fP\fB, double \fP\fIgreen_X\fP\fB, double \fIgreen_Y, | ||
564 | |||
565 | \fBdouble \fP\fIgreen_Z\fP\fB, double \fP\fIblue_X\fP\fB, double \fP\fIblue_Y\fP\fB, double \fIblue_Z\fP\fB);\fP | ||
566 | |||
567 | \fI\fB | ||
568 | |||
569 | \fBvoid png_set_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fIint_red_X\fP\fB, png_fixed_point \fP\fIint_red_Y\fP\fB, png_fixed_point \fP\fIint_red_Z\fP\fB, png_fixed_point \fP\fIint_green_X\fP\fB, png_fixed_point \fP\fIint_green_Y\fP\fB, png_fixed_point \fP\fIint_green_Z\fP\fB, png_fixed_point \fP\fIint_blue_X\fP\fB, png_fixed_point \fP\fIint_blue_Y\fP\fB, png_fixed_point \fIint_blue_Z\fP\fB);\fP | ||
570 | |||
571 | \fI\fB | ||
572 | |||
573 | \fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP | ||
574 | |||
575 | \fI\fB | ||
576 | |||
577 | \fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP | ||
578 | |||
579 | \fI\fB | ||
580 | |||
581 | \fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP | ||
582 | |||
583 | \fI\fB | ||
584 | |||
585 | \fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP | ||
586 | |||
587 | \fI\fB | ||
588 | |||
589 | \fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP | ||
590 | |||
591 | \fI\fB | ||
592 | |||
593 | \fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP | ||
594 | |||
595 | \fI\fB | ||
596 | |||
597 | \fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP | ||
598 | |||
599 | \fI\fB | ||
600 | |||
601 | \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP | ||
602 | |||
603 | \fI\fB | ||
604 | |||
605 | \fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP | ||
606 | |||
607 | \fI\fB | ||
608 | |||
609 | \fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP | ||
610 | |||
611 | \fI\fB | ||
612 | |||
613 | \fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP | ||
614 | |||
615 | \fI\fB | ||
616 | |||
617 | \fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP | ||
618 | |||
619 | \fI\fB | ||
620 | |||
621 | \fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP | ||
622 | |||
623 | \fI\fB | ||
624 | |||
625 | \fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP | ||
626 | |||
627 | \fI\fB | ||
628 | |||
629 | \fBvoid png_set_filter_heuristics_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_fixed_point_p \fP\fIfilter_weights\fP\fB, png_fixed_point_p \fIfilter_costs\fP\fB);\fP | ||
630 | |||
631 | \fI\fB | ||
632 | |||
633 | \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP | ||
634 | |||
635 | \fI\fB | ||
636 | |||
637 | \fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP | ||
638 | |||
639 | \fI\fB | ||
640 | |||
641 | \fBvoid png_set_gamma_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIscreen_gamma\fP\fB, png_uint_32 \fIdefault_file_gamma\fP\fB);\fP | ||
642 | |||
643 | \fI\fB | ||
644 | |||
645 | \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP | ||
646 | |||
647 | \fI\fB | ||
648 | |||
649 | \fBvoid png_set_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIfile_gamma\fP\fB);\fP | ||
650 | |||
651 | \fI\fB | ||
652 | |||
653 | \fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP | ||
654 | |||
655 | \fI\fB | ||
656 | |||
657 | \fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP | ||
658 | |||
659 | \fI\fB | ||
660 | |||
661 | \fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP | ||
662 | |||
663 | \fI\fB | ||
664 | |||
665 | \fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP | ||
666 | |||
667 | \fI\fB | ||
668 | |||
669 | \fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP | ||
670 | |||
671 | \fI\fB | ||
672 | |||
673 | \fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP | ||
674 | |||
675 | \fI\fB | ||
676 | |||
677 | \fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP | ||
678 | |||
679 | \fI\fB | ||
680 | |||
681 | \fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP | ||
682 | |||
683 | \fI\fB | ||
684 | |||
685 | \fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP | ||
686 | |||
687 | \fI\fB | ||
688 | |||
689 | \fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP | ||
690 | |||
691 | \fI\fB | ||
692 | |||
693 | \fBjmp_buf* png_set_longjmp_fn (png_structp \fP\fIpng_ptr\fP\fB, png_longjmp_ptr \fP\fIlongjmp_fn\fP\fB, size_t \fIjmp_buf_size\fP\fB);\fP | ||
694 | |||
695 | \fI\fB | ||
696 | |||
697 | \fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP | ||
698 | |||
699 | \fI\fB | ||
700 | |||
701 | \fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP | ||
702 | |||
703 | \fI\fB | ||
704 | |||
705 | \fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP | ||
706 | |||
707 | \fI\fB | ||
708 | |||
709 | \fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP | ||
710 | |||
711 | \fI\fB | ||
712 | |||
713 | \fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP | ||
714 | |||
715 | \fI\fB | ||
716 | |||
717 | \fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP | ||
718 | |||
719 | \fI\fB | ||
720 | |||
721 | \fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP | ||
722 | |||
723 | \fI\fB | ||
724 | |||
725 | \fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP | ||
726 | |||
727 | \fI\fB | ||
728 | |||
729 | \fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP | ||
730 | |||
731 | \fI\fB | ||
732 | |||
733 | \fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP | ||
734 | |||
735 | \fI\fB | ||
736 | |||
737 | \fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP | ||
738 | |||
739 | \fI\fB | ||
740 | |||
741 | \fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP | ||
742 | |||
743 | \fI\fB | ||
744 | |||
745 | \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP | ||
746 | |||
747 | \fI\fB | ||
748 | |||
749 | \fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP | ||
750 | |||
751 | \fI\fB | ||
752 | |||
753 | \fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP | ||
754 | |||
755 | \fI\fB | ||
756 | |||
757 | \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP | ||
758 | |||
759 | \fI\fB | ||
760 | |||
761 | \fBvoid png_set_rgb_to_gray (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIerror_action\fP\fB, double \fP\fIred\fP\fB, double \fIgreen\fP\fB);\fP | ||
762 | |||
763 | \fI\fB | ||
764 | |||
765 | \fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP | ||
766 | |||
767 | \fI\fB | ||
768 | |||
769 | \fBvoid png_set_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytepp \fIrow_pointers\fP\fB);\fP | ||
770 | |||
771 | \fI\fB | ||
772 | |||
773 | \fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP | ||
774 | |||
775 | \fI\fB | ||
776 | |||
777 | \fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP | ||
778 | |||
779 | \fI\fB | ||
780 | |||
781 | \fBvoid png_set_sCAL_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_fixed_point \fP\fIwidth\fP\fB, png_fixed_point \fIheight\fP\fB);\fP | ||
782 | |||
783 | \fI\fB | ||
784 | |||
785 | \fBvoid png_set_sCAL_s (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_charp \fP\fIwidth\fP\fB, png_charp \fIheight\fP\fB);\fP | ||
786 | |||
787 | \fI\fB | ||
788 | |||
789 | \fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP | ||
790 | |||
791 | \fI\fB | ||
792 | |||
793 | \fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP | ||
794 | |||
795 | \fI\fB | ||
796 | |||
797 | \fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP | ||
798 | |||
799 | \fI\fB | ||
800 | |||
801 | \fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP | ||
802 | |||
803 | \fI\fB | ||
804 | |||
805 | \fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP | ||
806 | |||
807 | \fI\fB | ||
808 | |||
809 | \fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP | ||
810 | |||
811 | \fI\fB | ||
812 | |||
813 | \fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP | ||
814 | |||
815 | \fI\fB | ||
816 | |||
817 | \fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP | ||
818 | |||
819 | \fI\fB | ||
820 | |||
821 | \fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP | ||
822 | |||
823 | \fI\fB | ||
824 | |||
825 | \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP | ||
826 | |||
827 | \fI\fB | ||
828 | |||
829 | \fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP | ||
830 | |||
831 | \fI\fB | ||
832 | |||
833 | \fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP | ||
834 | |||
835 | \fI\fB | ||
836 | |||
837 | \fBvoid png_set_text_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP | ||
838 | |||
839 | \fI\fB | ||
840 | |||
841 | \fBvoid png_set_text_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP | ||
842 | |||
843 | \fI\fB | ||
844 | |||
845 | \fBvoid png_set_text_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP | ||
846 | |||
847 | \fI\fB | ||
848 | |||
849 | \fBvoid png_set_text_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP | ||
850 | |||
851 | \fI\fB | ||
852 | |||
853 | \fBvoid \fP\fIpng_set_text_compression_method\fP\fB, (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod)\fP\fB);\fP | ||
854 | |||
855 | \fI\fB | ||
856 | |||
857 | \fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP | ||
858 | |||
859 | \fI\fB | ||
860 | |||
861 | \fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP | ||
862 | |||
863 | \fI\fB | ||
864 | |||
865 | \fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP | ||
866 | |||
867 | \fI\fB | ||
868 | |||
869 | \fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP | ||
870 | |||
871 | \fI\fB | ||
872 | |||
873 | \fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP | ||
874 | |||
875 | \fI\fB | ||
876 | |||
877 | \fBvoid png_set_user_limits (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIuser_width_max\fP\fB, png_uint_32 \fIuser_height_max\fP\fB);\fP | ||
878 | |||
879 | \fI\fB | ||
880 | |||
881 | \fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP | ||
882 | |||
883 | \fI\fB | ||
884 | |||
885 | \fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP | ||
886 | |||
887 | \fI\fB | ||
888 | |||
889 | \fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP | ||
890 | |||
891 | \fI\fB | ||
892 | |||
893 | \fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP | ||
894 | |||
895 | \fI\fB | ||
896 | |||
897 | \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP | ||
898 | |||
899 | \fI\fB | ||
900 | |||
901 | \fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP | ||
902 | |||
903 | \fI\fB | ||
904 | |||
905 | \fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP | ||
906 | |||
907 | \fI\fB | ||
908 | |||
909 | \fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP | ||
910 | |||
911 | \fI\fB | ||
912 | |||
913 | \fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP | ||
914 | |||
915 | \fI\fB | ||
916 | |||
917 | \fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP | ||
918 | |||
919 | \fI\fB | ||
920 | |||
921 | \fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP | ||
922 | |||
923 | \fI\fB | ||
924 | |||
925 | \fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
926 | |||
927 | \fI\fB | ||
928 | |||
929 | \fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP | ||
930 | |||
931 | \fI\fB | ||
932 | |||
933 | \fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP | ||
934 | |||
935 | \fI\fB | ||
936 | |||
937 | \fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
938 | |||
939 | \fI\fB | ||
940 | |||
941 | \fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP | ||
942 | |||
943 | \fI\fB | ||
944 | |||
945 | \fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP | ||
946 | |||
947 | \fI\fB | ||
948 | |||
949 | \fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP | ||
950 | |||
951 | \fI\fB | ||
952 | |||
953 | \fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP | ||
954 | |||
955 | \fI\fB | ||
956 | |||
957 | \fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP | ||
958 | |||
959 | \fI\fB | ||
960 | |||
961 | \fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP | ||
962 | |||
963 | \fI\fB | ||
964 | |||
965 | \fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP | ||
966 | |||
967 | \fI\fB | ||
968 | |||
969 | .SH DESCRIPTION | ||
970 | The | ||
971 | .I libpng | ||
972 | library supports encoding, decoding, and various manipulations of | ||
973 | the Portable Network Graphics (PNG) format image files. It uses the | ||
974 | .IR zlib(3) | ||
975 | compression library. | ||
976 | Following is a copy of the libpng-manual.txt file that accompanies libpng. | ||
977 | .SH LIBPNG.TXT | ||
978 | libpng-manual.txt - A description on how to use and modify libpng | ||
979 | |||
980 | libpng version 1.5.9 - February 18, 2012 | ||
981 | Updated and distributed by Glenn Randers-Pehrson | ||
982 | <glennrp at users.sourceforge.net> | ||
983 | Copyright (c) 1998-2011 Glenn Randers-Pehrson | ||
984 | |||
985 | This document is released under the libpng license. | ||
986 | For conditions of distribution and use, see the disclaimer | ||
987 | and license in png.h | ||
988 | |||
989 | Based on: | ||
990 | |||
991 | libpng versions 0.97, January 1998, through 1.5.9 - February 18, 2012 | ||
992 | Updated and distributed by Glenn Randers-Pehrson | ||
993 | Copyright (c) 1998-2011 Glenn Randers-Pehrson | ||
994 | |||
995 | libpng 1.0 beta 6 version 0.96 May 28, 1997 | ||
996 | Updated and distributed by Andreas Dilger | ||
997 | Copyright (c) 1996, 1997 Andreas Dilger | ||
998 | |||
999 | libpng 1.0 beta 2 - version 0.88 January 26, 1996 | ||
1000 | For conditions of distribution and use, see copyright | ||
1001 | notice in png.h. Copyright (c) 1995, 1996 Guy Eric | ||
1002 | Schalnat, Group 42, Inc. | ||
1003 | |||
1004 | Updated/rewritten per request in the libpng FAQ | ||
1005 | Copyright (c) 1995, 1996 Frank J. T. Wojcik | ||
1006 | December 18, 1995 & January 20, 1996 | ||
1007 | |||
1008 | .SH I. Introduction | ||
1009 | |||
1010 | This file describes how to use and modify the PNG reference library | ||
1011 | (known as libpng) for your own use. There are five sections to this | ||
1012 | file: introduction, structures, reading, writing, and modification and | ||
1013 | configuration notes for various special platforms. In addition to this | ||
1014 | file, example.c is a good starting point for using the library, as | ||
1015 | it is heavily commented and should include everything most people | ||
1016 | will need. We assume that libpng is already installed; see the | ||
1017 | INSTALL file for instructions on how to install libpng. | ||
1018 | |||
1019 | For examples of libpng usage, see the files "example.c", "pngtest.c", | ||
1020 | and the files in the "contrib" directory, all of which are included in | ||
1021 | the libpng distribution. | ||
1022 | |||
1023 | Libpng was written as a companion to the PNG specification, as a way | ||
1024 | of reducing the amount of time and effort it takes to support the PNG | ||
1025 | file format in application programs. | ||
1026 | |||
1027 | The PNG specification (second edition), November 2003, is available as | ||
1028 | a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at | ||
1029 | <http://www.w3.org/TR/2003/REC-PNG-20031110/ | ||
1030 | The W3C and ISO documents have identical technical content. | ||
1031 | |||
1032 | The PNG-1.2 specification is available at | ||
1033 | <http://www.libpng.org/pub/png/documents/>. It is technically equivalent | ||
1034 | to the PNG specification (second edition) but has some additional material. | ||
1035 | |||
1036 | The PNG-1.0 specification is available | ||
1037 | as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a | ||
1038 | W3C Recommendation <http://www.w3.org/TR/REC.png.html>. | ||
1039 | |||
1040 | Some additional chunks are described in the special-purpose public chunks | ||
1041 | documents at <http://www.libpng.org/pub/png/documents/>. | ||
1042 | |||
1043 | Other information | ||
1044 | about PNG, and the latest version of libpng, can be found at the PNG home | ||
1045 | page, <http://www.libpng.org/pub/png/>. | ||
1046 | |||
1047 | Most users will not have to modify the library significantly; advanced | ||
1048 | users may want to modify it more. All attempts were made to make it as | ||
1049 | complete as possible, while keeping the code easy to understand. | ||
1050 | Currently, this library only supports C. Support for other languages | ||
1051 | is being considered. | ||
1052 | |||
1053 | Libpng has been designed to handle multiple sessions at one time, | ||
1054 | to be easily modifiable, to be portable to the vast majority of | ||
1055 | machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy | ||
1056 | to use. The ultimate goal of libpng is to promote the acceptance of | ||
1057 | the PNG file format in whatever way possible. While there is still | ||
1058 | work to be done (see the TODO file), libpng should cover the | ||
1059 | majority of the needs of its users. | ||
1060 | |||
1061 | Libpng uses zlib for its compression and decompression of PNG files. | ||
1062 | Further information about zlib, and the latest version of zlib, can | ||
1063 | be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>. | ||
1064 | The zlib compression utility is a general purpose utility that is | ||
1065 | useful for more than PNG files, and can be used without libpng. | ||
1066 | See the documentation delivered with zlib for more details. | ||
1067 | You can usually find the source files for the zlib utility wherever you | ||
1068 | find the libpng source files. | ||
1069 | |||
1070 | Libpng is thread safe, provided the threads are using different | ||
1071 | instances of the structures. Each thread should have its own | ||
1072 | png_struct and png_info instances, and thus its own image. | ||
1073 | Libpng does not protect itself against two threads using the | ||
1074 | same instance of a structure. | ||
1075 | |||
1076 | .SH II. Structures | ||
1077 | |||
1078 | There are two main structures that are important to libpng, png_struct | ||
1079 | and png_info. Both are internal structures that are no longer exposed | ||
1080 | in the libpng interface (as of libpng 1.5.0). | ||
1081 | |||
1082 | The png_info structure is designed to provide information about the | ||
1083 | PNG file. At one time, the fields of png_info were intended to be | ||
1084 | directly accessible to the user. However, this tended to cause problems | ||
1085 | with applications using dynamically loaded libraries, and as a result | ||
1086 | a set of interface functions for png_info (the png_get_*() and png_set_*() | ||
1087 | functions) was developed, and direct access to the png_info fields was | ||
1088 | deprecated.. | ||
1089 | |||
1090 | The png_struct structure is the object used by the library to decode a | ||
1091 | single image. As of 1.5.0 this structure is also not exposed. | ||
1092 | |||
1093 | Almost all libpng APIs require a pointer to a png_struct as the first argument. | ||
1094 | Many (in particular the png_set and png_get APIs) also require a pointer | ||
1095 | to png_info as the second argument. Some application visible macros | ||
1096 | defined in png.h designed for basic data access (reading and writing | ||
1097 | integers in the PNG format) don't take a png_info pointer, but it's almost | ||
1098 | always safe to assume that a (png_struct*) has to be passed to call an API | ||
1099 | function. | ||
1100 | |||
1101 | You can have more than one png_info structure associated with an image, | ||
1102 | as illustrated in pngtest.c, one for information valid prior to the | ||
1103 | IDAT chunks and another (called "end_info" below) for things after them. | ||
1104 | |||
1105 | The png.h header file is an invaluable reference for programming with libpng. | ||
1106 | And while I'm on the topic, make sure you include the libpng header file: | ||
1107 | |||
1108 | #include <png.h> | ||
1109 | |||
1110 | and also (as of libpng-1.5.0) the zlib header file, if you need it: | ||
1111 | |||
1112 | #include <zlib.h> | ||
1113 | |||
1114 | .SS Types | ||
1115 | |||
1116 | The png.h header file defines a number of integral types used by the | ||
1117 | APIs. Most of these are fairly obvious; for example types corresponding | ||
1118 | to integers of particular sizes and types for passing color values. | ||
1119 | |||
1120 | One exception is how non-integral numbers are handled. For application | ||
1121 | convenience most APIs that take such numbers have C (double) arguments, | ||
1122 | however internally PNG, and libpng, use 32 bit signed integers and encode | ||
1123 | the value by multiplying by 100,000. As of libpng 1.5.0 a convenience | ||
1124 | macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point) | ||
1125 | which is simply (png_int_32). | ||
1126 | |||
1127 | All APIs that take (double) arguments also have a matching API that | ||
1128 | takes the corresponding fixed point integer arguments. The fixed point | ||
1129 | API has the same name as the floating point one with "_fixed" appended. | ||
1130 | The actual range of values permitted in the APIs is frequently less than | ||
1131 | the full range of (png_fixed_point) (-21474 to +21474). When APIs require | ||
1132 | a non-negative argument the type is recorded as png_uint_32 above. Consult | ||
1133 | the header file and the text below for more information. | ||
1134 | |||
1135 | Special care must be take with sCAL chunk handling because the chunk itself | ||
1136 | uses non-integral values encoded as strings containing decimal floating point | ||
1137 | numbers. See the comments in the header file. | ||
1138 | |||
1139 | .SS Configuration | ||
1140 | |||
1141 | The main header file function declarations are frequently protected by C | ||
1142 | preprocessing directives of the form: | ||
1143 | |||
1144 | #ifdef PNG_feature_SUPPORTED | ||
1145 | declare-function | ||
1146 | #endif | ||
1147 | ... | ||
1148 | #ifdef PNG_feature_SUPPORTED | ||
1149 | use-function | ||
1150 | #endif | ||
1151 | |||
1152 | The library can be built without support for these APIs, although a | ||
1153 | standard build will have all implemented APIs. Application programs | ||
1154 | should check the feature macros before using an API for maximum | ||
1155 | portability. From libpng 1.5.0 the feature macros set during the build | ||
1156 | of libpng are recorded in the header file "pnglibconf.h" and this file | ||
1157 | is always included by png.h. | ||
1158 | |||
1159 | If you don't need to change the library configuration from the default, skip to | ||
1160 | the next section ("Reading"). | ||
1161 | |||
1162 | Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all | ||
1163 | of the build project files in the 'projects' directory simply copy | ||
1164 | scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build | ||
1165 | systems do not permit easy auto-configuration of the library - they only | ||
1166 | support the default configuration. | ||
1167 | |||
1168 | The easiest way to make minor changes to the libpng configuration when | ||
1169 | auto-configuration is supported is to add definitions to the command line | ||
1170 | using (typically) CPPFLAGS. For example: | ||
1171 | |||
1172 | CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC | ||
1173 | |||
1174 | will change the internal libpng math implementation for gamma correction and | ||
1175 | other arithmetic calculations to fixed point, avoiding the need for fast | ||
1176 | floating point support. The result can be seen in the generated pnglibconf.h - | ||
1177 | make sure it contains the changed feature macro setting. | ||
1178 | |||
1179 | If you need to make more extensive configuration changes - more than one or two | ||
1180 | feature macro settings - you can either add -DPNG_USER_CONFIG to the build | ||
1181 | command line and put a list of feature macro settings in pngusr.h or you can set | ||
1182 | DFA_XTRA (a makefile variable) to a file containing the same information in the | ||
1183 | form of 'option' settings. | ||
1184 | |||
1185 | A. Changing pnglibconf.h | ||
1186 | |||
1187 | A variety of methods exist to build libpng. Not all of these support | ||
1188 | reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be | ||
1189 | rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand. | ||
1190 | |||
1191 | Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to | ||
1192 | pnglibconf.h and changing the lines defining the supported features, paying | ||
1193 | very close attention to the 'option' information in scripts/pnglibconf.dfa | ||
1194 | that describes those features and their requirements. This is easy to get | ||
1195 | wrong. | ||
1196 | |||
1197 | B. Configuration using DFA_XTRA | ||
1198 | |||
1199 | Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later | ||
1200 | variant such as 'nawk' or 'gawk', is available. The configure build will | ||
1201 | automatically find an appropriate awk and build pnglibconf.h. | ||
1202 | The scripts/pnglibconf.mak file contains a set of make rules for doing the | ||
1203 | same thing if configure is not used, and many of the makefiles in the scripts | ||
1204 | directory use this approach. | ||
1205 | |||
1206 | When rebuilding simply write a new file containing changed options and set | ||
1207 | DFA_XTRA to the name of this file. This causes the build to append the new file | ||
1208 | to the end of scripts/pnglibconf.dfa. The pngusr.dfa file should contain lines | ||
1209 | of the following forms: | ||
1210 | |||
1211 | everything = off | ||
1212 | |||
1213 | This turns all optional features off. Include it at the start of pngusr.dfa to | ||
1214 | make it easier to build a minimal configuration. You will need to turn at least | ||
1215 | some features on afterward to enable either reading or writing code, or both. | ||
1216 | |||
1217 | option feature on | ||
1218 | option feature off | ||
1219 | |||
1220 | Enable or disable a single feature. This will automatically enable other | ||
1221 | features required by a feature that is turned on or disable other features that | ||
1222 | require a feature which is turned off. Conflicting settings will cause an error | ||
1223 | message to be emitted by awk. | ||
1224 | |||
1225 | setting feature default value | ||
1226 | |||
1227 | Changes the default value of setting 'feature' to 'value'. There are a small | ||
1228 | number of settings listed at the top of pnglibconf.h, they are documented in the | ||
1229 | source code. Most of these values have performance implications for the library | ||
1230 | but most of them have no visible effect on the API. Some can also be overridden | ||
1231 | from the API. | ||
1232 | |||
1233 | This method of building a customized pnglibconf.h is illustrated in | ||
1234 | contrib/pngminim/*. See the "$(PNGCONF):" target in the makefile and | ||
1235 | pngusr.dfa in these directories. | ||
1236 | |||
1237 | C. Configuration using PNG_USR_CONFIG | ||
1238 | |||
1239 | If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file | ||
1240 | pngusr.h will automatically be included before the options in | ||
1241 | scripts/pnglibconf.dfa are processed. Your pngusr.h file should contain only | ||
1242 | macro definitions turning features on or off or setting settings. | ||
1243 | |||
1244 | Apart from the global setting "everything = off" all the options listed above | ||
1245 | can be set using macros in pngusr.h: | ||
1246 | |||
1247 | #define PNG_feature_SUPPORTED | ||
1248 | |||
1249 | is equivalent to: | ||
1250 | |||
1251 | option feature on | ||
1252 | |||
1253 | #define PNG_NO_feature | ||
1254 | |||
1255 | is equivalent to: | ||
1256 | |||
1257 | option feature off | ||
1258 | |||
1259 | #define PNG_feature value | ||
1260 | |||
1261 | is equivalent to: | ||
1262 | |||
1263 | setting feature default value | ||
1264 | |||
1265 | Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the | ||
1266 | pngusr file you supply override the contents of scripts/pnglibconf.dfa | ||
1267 | |||
1268 | If confusing or incomprehensible behavior results it is possible to | ||
1269 | examine the intermediate file pnglibconf.dfn to find the full set of | ||
1270 | dependency information for each setting and option. Simply locate the | ||
1271 | feature in the file and read the C comments that precede it. | ||
1272 | |||
1273 | This method is also illustrated in the contrib/pngminim/* makefiles and | ||
1274 | pngusr.h. | ||
1275 | |||
1276 | .SH III. Reading | ||
1277 | |||
1278 | We'll now walk you through the possible functions to call when reading | ||
1279 | in a PNG file sequentially, briefly explaining the syntax and purpose | ||
1280 | of each one. See example.c and png.h for more detail. While | ||
1281 | progressive reading is covered in the next section, you will still | ||
1282 | need some of the functions discussed in this section to read a PNG | ||
1283 | file. | ||
1284 | |||
1285 | .SS Setup | ||
1286 | |||
1287 | You will want to do the I/O initialization(*) before you get into libpng, | ||
1288 | so if it doesn't work, you don't have much to undo. Of course, you | ||
1289 | will also want to insure that you are, in fact, dealing with a PNG | ||
1290 | file. Libpng provides a simple check to see if a file is a PNG file. | ||
1291 | To use it, pass in the first 1 to 8 bytes of the file to the function | ||
1292 | png_sig_cmp(), and it will return 0 (false) if the bytes match the | ||
1293 | corresponding bytes of the PNG signature, or nonzero (true) otherwise. | ||
1294 | Of course, the more bytes you pass in, the greater the accuracy of the | ||
1295 | prediction. | ||
1296 | |||
1297 | If you are intending to keep the file pointer open for use in libpng, | ||
1298 | you must ensure you don't read more than 8 bytes from the beginning | ||
1299 | of the file, and you also have to make a call to png_set_sig_bytes_read() | ||
1300 | with the number of bytes you read from the beginning. Libpng will | ||
1301 | then only check the bytes (if any) that your program didn't read. | ||
1302 | |||
1303 | (*): If you are not using the standard I/O functions, you will need | ||
1304 | to replace them with custom functions. See the discussion under | ||
1305 | Customizing libpng. | ||
1306 | |||
1307 | |||
1308 | FILE *fp = fopen(file_name, "rb"); | ||
1309 | if (!fp) | ||
1310 | { | ||
1311 | return (ERROR); | ||
1312 | } | ||
1313 | |||
1314 | fread(header, 1, number, fp); | ||
1315 | is_png = !png_sig_cmp(header, 0, number); | ||
1316 | |||
1317 | if (!is_png) | ||
1318 | { | ||
1319 | return (NOT_PNG); | ||
1320 | } | ||
1321 | |||
1322 | |||
1323 | Next, png_struct and png_info need to be allocated and initialized. In | ||
1324 | order to ensure that the size of these structures is correct even with a | ||
1325 | dynamically linked libpng, there are functions to initialize and | ||
1326 | allocate the structures. We also pass the library version, optional | ||
1327 | pointers to error handling functions, and a pointer to a data struct for | ||
1328 | use by the error functions, if necessary (the pointer and functions can | ||
1329 | be NULL if the default error handlers are to be used). See the section | ||
1330 | on Changes to Libpng below regarding the old initialization functions. | ||
1331 | The structure allocation functions quietly return NULL if they fail to | ||
1332 | create the structure, so your application should check for that. | ||
1333 | |||
1334 | png_structp png_ptr = png_create_read_struct | ||
1335 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, | ||
1336 | user_error_fn, user_warning_fn); | ||
1337 | |||
1338 | if (!png_ptr) | ||
1339 | return (ERROR); | ||
1340 | |||
1341 | png_infop info_ptr = png_create_info_struct(png_ptr); | ||
1342 | |||
1343 | if (!info_ptr) | ||
1344 | { | ||
1345 | png_destroy_read_struct(&png_ptr, | ||
1346 | (png_infopp)NULL, (png_infopp)NULL); | ||
1347 | return (ERROR); | ||
1348 | } | ||
1349 | |||
1350 | If you want to use your own memory allocation routines, | ||
1351 | use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use | ||
1352 | png_create_read_struct_2() instead of png_create_read_struct(): | ||
1353 | |||
1354 | png_structp png_ptr = png_create_read_struct_2 | ||
1355 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, | ||
1356 | user_error_fn, user_warning_fn, (png_voidp) | ||
1357 | user_mem_ptr, user_malloc_fn, user_free_fn); | ||
1358 | |||
1359 | The error handling routines passed to png_create_read_struct() | ||
1360 | and the memory alloc/free routines passed to png_create_struct_2() | ||
1361 | are only necessary if you are not using the libpng supplied error | ||
1362 | handling and memory alloc/free functions. | ||
1363 | |||
1364 | When libpng encounters an error, it expects to longjmp back | ||
1365 | to your routine. Therefore, you will need to call setjmp and pass | ||
1366 | your png_jmpbuf(png_ptr). If you read the file from different | ||
1367 | routines, you will need to update the longjmp buffer every time you enter | ||
1368 | a new routine that will call a png_*() function. | ||
1369 | |||
1370 | See your documentation of setjmp/longjmp for your compiler for more | ||
1371 | information on setjmp/longjmp. See the discussion on libpng error | ||
1372 | handling in the Customizing Libpng section below for more information | ||
1373 | on the libpng error handling. If an error occurs, and libpng longjmp's | ||
1374 | back to your setjmp, you will want to call png_destroy_read_struct() to | ||
1375 | free any memory. | ||
1376 | |||
1377 | if (setjmp(png_jmpbuf(png_ptr))) | ||
1378 | { | ||
1379 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
1380 | &end_info); | ||
1381 | fclose(fp); | ||
1382 | return (ERROR); | ||
1383 | } | ||
1384 | |||
1385 | Pass (png_infopp)NULL instead of &end_info if you didn't create | ||
1386 | an end_info structure. | ||
1387 | |||
1388 | If you would rather avoid the complexity of setjmp/longjmp issues, | ||
1389 | you can compile libpng with PNG_NO_SETJMP, in which case | ||
1390 | errors will result in a call to PNG_ABORT() which defaults to abort(). | ||
1391 | |||
1392 | You can #define PNG_ABORT() to a function that does something | ||
1393 | more useful than abort(), as long as your function does not | ||
1394 | return. | ||
1395 | |||
1396 | Now you need to set up the input code. The default for libpng is to | ||
1397 | use the C function fread(). If you use this, you will need to pass a | ||
1398 | valid FILE * in the function png_init_io(). Be sure that the file is | ||
1399 | opened in binary mode. If you wish to handle reading data in another | ||
1400 | way, you need not call the png_init_io() function, but you must then | ||
1401 | implement the libpng I/O methods discussed in the Customizing Libpng | ||
1402 | section below. | ||
1403 | |||
1404 | png_init_io(png_ptr, fp); | ||
1405 | |||
1406 | If you had previously opened the file and read any of the signature from | ||
1407 | the beginning in order to see if this was a PNG file, you need to let | ||
1408 | libpng know that there are some bytes missing from the start of the file. | ||
1409 | |||
1410 | png_set_sig_bytes(png_ptr, number); | ||
1411 | |||
1412 | You can change the zlib compression buffer size to be used while | ||
1413 | reading compressed data with | ||
1414 | |||
1415 | png_set_compression_buffer_size(png_ptr, buffer_size); | ||
1416 | |||
1417 | where the default size is 8192 bytes. Note that the buffer size | ||
1418 | is changed immediately and the buffer is reallocated immediately, | ||
1419 | instead of setting a flag to be acted upon later. | ||
1420 | |||
1421 | If you want CRC errors to be handled in a different manner than | ||
1422 | the default, use | ||
1423 | |||
1424 | png_set_crc_action(png_ptr, crit_action, ancil_action); | ||
1425 | |||
1426 | The values for png_set_crc_action() say how libpng is to handle CRC errors in | ||
1427 | ancillary and critical chunks, and whether to use the data contained | ||
1428 | therein. Note that it is impossible to "discard" data in a critical | ||
1429 | chunk. | ||
1430 | |||
1431 | Choices for (int) crit_action are | ||
1432 | PNG_CRC_DEFAULT 0 error/quit | ||
1433 | PNG_CRC_ERROR_QUIT 1 error/quit | ||
1434 | PNG_CRC_WARN_USE 3 warn/use data | ||
1435 | PNG_CRC_QUIET_USE 4 quiet/use data | ||
1436 | PNG_CRC_NO_CHANGE 5 use the current value | ||
1437 | |||
1438 | Choices for (int) ancil_action are | ||
1439 | PNG_CRC_DEFAULT 0 error/quit | ||
1440 | PNG_CRC_ERROR_QUIT 1 error/quit | ||
1441 | PNG_CRC_WARN_DISCARD 2 warn/discard data | ||
1442 | PNG_CRC_WARN_USE 3 warn/use data | ||
1443 | PNG_CRC_QUIET_USE 4 quiet/use data | ||
1444 | PNG_CRC_NO_CHANGE 5 use the current value | ||
1445 | |||
1446 | .SS Setting up callback code | ||
1447 | |||
1448 | You can set up a callback function to handle any unknown chunks in the | ||
1449 | input stream. You must supply the function | ||
1450 | |||
1451 | read_chunk_callback(png_structp png_ptr, | ||
1452 | png_unknown_chunkp chunk); | ||
1453 | { | ||
1454 | /* The unknown chunk structure contains your | ||
1455 | chunk data, along with similar data for any other | ||
1456 | unknown chunks: */ | ||
1457 | |||
1458 | png_byte name[5]; | ||
1459 | png_byte *data; | ||
1460 | png_size_t size; | ||
1461 | |||
1462 | /* Note that libpng has already taken care of | ||
1463 | the CRC handling */ | ||
1464 | |||
1465 | /* put your code here. Search for your chunk in the | ||
1466 | unknown chunk structure, process it, and return one | ||
1467 | of the following: */ | ||
1468 | |||
1469 | return (-n); /* chunk had an error */ | ||
1470 | return (0); /* did not recognize */ | ||
1471 | return (n); /* success */ | ||
1472 | } | ||
1473 | |||
1474 | (You can give your function another name that you like instead of | ||
1475 | "read_chunk_callback") | ||
1476 | |||
1477 | To inform libpng about your function, use | ||
1478 | |||
1479 | png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr, | ||
1480 | read_chunk_callback); | ||
1481 | |||
1482 | This names not only the callback function, but also a user pointer that | ||
1483 | you can retrieve with | ||
1484 | |||
1485 | png_get_user_chunk_ptr(png_ptr); | ||
1486 | |||
1487 | If you call the png_set_read_user_chunk_fn() function, then all unknown | ||
1488 | chunks will be saved when read, in case your callback function will need | ||
1489 | one or more of them. This behavior can be changed with the | ||
1490 | png_set_keep_unknown_chunks() function, described below. | ||
1491 | |||
1492 | At this point, you can set up a callback function that will be | ||
1493 | called after each row has been read, which you can use to control | ||
1494 | a progress meter or the like. It's demonstrated in pngtest.c. | ||
1495 | You must supply a function | ||
1496 | |||
1497 | void read_row_callback(png_structp png_ptr, | ||
1498 | png_uint_32 row, int pass); | ||
1499 | { | ||
1500 | /* put your code here */ | ||
1501 | } | ||
1502 | |||
1503 | (You can give it another name that you like instead of "read_row_callback") | ||
1504 | |||
1505 | To inform libpng about your function, use | ||
1506 | |||
1507 | png_set_read_status_fn(png_ptr, read_row_callback); | ||
1508 | |||
1509 | When this function is called the row has already been completely processed and | ||
1510 | the 'row' and 'pass' refer to the next row to be handled. For the | ||
1511 | non-interlaced case the row that was just handled is simply one less than the | ||
1512 | passed in row number, and pass will always be 0. For the interlaced case the | ||
1513 | same applies unless the row value is 0, in which case the row just handled was | ||
1514 | the last one from one of the preceding passes. Because interlacing may skip a | ||
1515 | pass you cannot be sure that the preceding pass is just 'pass-1', if you really | ||
1516 | need to know what the last pass is record (row,pass) from the callback and use | ||
1517 | the last recorded value each time. | ||
1518 | |||
1519 | As with the user transform you can find the output row using the | ||
1520 | PNG_ROW_FROM_PASS_ROW macro. | ||
1521 | |||
1522 | .SS Unknown-chunk handling | ||
1523 | |||
1524 | Now you get to set the way the library processes unknown chunks in the | ||
1525 | input PNG stream. Both known and unknown chunks will be read. Normal | ||
1526 | behavior is that known chunks will be parsed into information in | ||
1527 | various info_ptr members while unknown chunks will be discarded. This | ||
1528 | behavior can be wasteful if your application will never use some known | ||
1529 | chunk types. To change this, you can call: | ||
1530 | |||
1531 | png_set_keep_unknown_chunks(png_ptr, keep, | ||
1532 | chunk_list, num_chunks); | ||
1533 | keep - 0: default unknown chunk handling | ||
1534 | 1: ignore; do not keep | ||
1535 | 2: keep only if safe-to-copy | ||
1536 | 3: keep even if unsafe-to-copy | ||
1537 | |||
1538 | You can use these definitions: | ||
1539 | PNG_HANDLE_CHUNK_AS_DEFAULT 0 | ||
1540 | PNG_HANDLE_CHUNK_NEVER 1 | ||
1541 | PNG_HANDLE_CHUNK_IF_SAFE 2 | ||
1542 | PNG_HANDLE_CHUNK_ALWAYS 3 | ||
1543 | |||
1544 | chunk_list - list of chunks affected (a byte string, | ||
1545 | five bytes per chunk, NULL or '\0' if | ||
1546 | num_chunks is 0) | ||
1547 | |||
1548 | num_chunks - number of chunks affected; if 0, all | ||
1549 | unknown chunks are affected. If nonzero, | ||
1550 | only the chunks in the list are affected | ||
1551 | |||
1552 | Unknown chunks declared in this way will be saved as raw data onto a | ||
1553 | list of png_unknown_chunk structures. If a chunk that is normally | ||
1554 | known to libpng is named in the list, it will be handled as unknown, | ||
1555 | according to the "keep" directive. If a chunk is named in successive | ||
1556 | instances of png_set_keep_unknown_chunks(), the final instance will | ||
1557 | take precedence. The IHDR and IEND chunks should not be named in | ||
1558 | chunk_list; if they are, libpng will process them normally anyway. | ||
1559 | If you know that your application will never make use of some particular | ||
1560 | chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below. | ||
1561 | |||
1562 | Here is an example of the usage of png_set_keep_unknown_chunks(), | ||
1563 | where the private "vpAg" chunk will later be processed by a user chunk | ||
1564 | callback function: | ||
1565 | |||
1566 | png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'}; | ||
1567 | |||
1568 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) | ||
1569 | png_byte unused_chunks[]= | ||
1570 | { | ||
1571 | 104, 73, 83, 84, (png_byte) '\0', /* hIST */ | ||
1572 | 105, 84, 88, 116, (png_byte) '\0', /* iTXt */ | ||
1573 | 112, 67, 65, 76, (png_byte) '\0', /* pCAL */ | ||
1574 | 115, 67, 65, 76, (png_byte) '\0', /* sCAL */ | ||
1575 | 115, 80, 76, 84, (png_byte) '\0', /* sPLT */ | ||
1576 | 116, 73, 77, 69, (png_byte) '\0', /* tIME */ | ||
1577 | }; | ||
1578 | #endif | ||
1579 | |||
1580 | ... | ||
1581 | |||
1582 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) | ||
1583 | /* ignore all unknown chunks: */ | ||
1584 | png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); | ||
1585 | |||
1586 | /* except for vpAg: */ | ||
1587 | png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); | ||
1588 | |||
1589 | /* also ignore unused known chunks: */ | ||
1590 | png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, | ||
1591 | (int)sizeof(unused_chunks)/5); | ||
1592 | #endif | ||
1593 | |||
1594 | .SS User limits | ||
1595 | |||
1596 | The PNG specification allows the width and height of an image to be as | ||
1597 | large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns. | ||
1598 | Since very few applications really need to process such large images, | ||
1599 | we have imposed an arbitrary 1-million limit on rows and columns. | ||
1600 | Larger images will be rejected immediately with a png_error() call. If | ||
1601 | you wish to change this limit, you can use | ||
1602 | |||
1603 | png_set_user_limits(png_ptr, width_max, height_max); | ||
1604 | |||
1605 | to set your own limits, or use width_max = height_max = 0x7fffffffL | ||
1606 | to allow all valid dimensions (libpng may reject some very large images | ||
1607 | anyway because of potential buffer overflow conditions). | ||
1608 | |||
1609 | You should put this statement after you create the PNG structure and | ||
1610 | before calling png_read_info(), png_read_png(), or png_process_data(). | ||
1611 | |||
1612 | When writing a PNG datastream, put this statement before calling | ||
1613 | png_write_info() or png_write_png(). | ||
1614 | |||
1615 | If you need to retrieve the limits that are being applied, use | ||
1616 | |||
1617 | width_max = png_get_user_width_max(png_ptr); | ||
1618 | height_max = png_get_user_height_max(png_ptr); | ||
1619 | |||
1620 | The PNG specification sets no limit on the number of ancillary chunks | ||
1621 | allowed in a PNG datastream. You can impose a limit on the total number | ||
1622 | of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with | ||
1623 | |||
1624 | png_set_chunk_cache_max(png_ptr, user_chunk_cache_max); | ||
1625 | |||
1626 | where 0x7fffffffL means unlimited. You can retrieve this limit with | ||
1627 | |||
1628 | chunk_cache_max = png_get_chunk_cache_max(png_ptr); | ||
1629 | |||
1630 | This limit also applies to the number of buffers that can be allocated | ||
1631 | by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks. | ||
1632 | |||
1633 | You can also set a limit on the amount of memory that a compressed chunk | ||
1634 | other than IDAT can occupy, with | ||
1635 | |||
1636 | png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max); | ||
1637 | |||
1638 | and you can retrieve the limit with | ||
1639 | |||
1640 | chunk_malloc_max = png_get_chunk_malloc_max(png_ptr); | ||
1641 | |||
1642 | Any chunks that would cause either of these limits to be exceeded will | ||
1643 | be ignored. | ||
1644 | |||
1645 | .SS Information about your system | ||
1646 | |||
1647 | If you intend to display the PNG or to incorporate it in other image data you | ||
1648 | need to tell libpng information about your display or drawing surface so that | ||
1649 | libpng can convert the values in the image to match the display. | ||
1650 | |||
1651 | From libpng-1.5.4 this information can be set before reading the PNG file | ||
1652 | header. In earlier versions png_set_gamma() existed but behaved incorrectly if | ||
1653 | called before the PNG file header had been read and png_set_alpha_mode() did not | ||
1654 | exist. | ||
1655 | |||
1656 | If you need to support versions prior to libpng-1.5.4 test the version number | ||
1657 | as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures | ||
1658 | described in the appropriate manual page. | ||
1659 | |||
1660 | You give libpng the encoding expected by your system expressed as a 'gamma' | ||
1661 | value. You can also specify a default encoding for the PNG file in | ||
1662 | case the required information is missing from the file. By default libpng | ||
1663 | assumes that the PNG data matches your system, to keep this default call: | ||
1664 | |||
1665 | png_set_gamma(png_ptr, screen_gamma, 1/screen_gamma/*file gamma*/); | ||
1666 | |||
1667 | or you can use the fixed point equivalent: | ||
1668 | |||
1669 | png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma, PNG_FP_1/screen_gamma); | ||
1670 | |||
1671 | If you don't know the gamma for your system it is probably 2.2 - a good | ||
1672 | approximation to the IEC standard for display systems (sRGB). If images are | ||
1673 | too contrasty or washed out you got the value wrong - check your system | ||
1674 | documentation! | ||
1675 | |||
1676 | Many systems permit the system gamma to be changed via a lookup table in the | ||
1677 | display driver, a few systems, including older Macs, change the response by | ||
1678 | default. As of 1.5.4 three special values are available to handle common | ||
1679 | situations: | ||
1680 | |||
1681 | PNG_DEFAULT_sRGB: Indicates that the system conforms to the IEC 61966-2-1 | ||
1682 | standard. This matches almost all systems. | ||
1683 | PNG_GAMMA_MAC_18: Indicates that the system is an older (pre Mac OS 10.6) | ||
1684 | Apple Macintosh system with the default settings. | ||
1685 | PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates that the | ||
1686 | system expects data with no gamma encoding. | ||
1687 | |||
1688 | You would use the linear (unencoded) value if you need to process the pixel | ||
1689 | values further because this avoids the need to decode and reencode each | ||
1690 | component value whenever arithmetic is performed. A lot of graphics software | ||
1691 | uses linear values for this reason, often with higher precision component values | ||
1692 | to preserve overall accuracy. | ||
1693 | |||
1694 | The second thing you may need to tell libpng about is how your system handles | ||
1695 | alpha channel information. Some, but not all, PNG files contain an alpha | ||
1696 | channel. To display these files correctly you need to compose the data onto a | ||
1697 | suitable background, as described in the PNG specification. | ||
1698 | |||
1699 | Libpng only supports composing onto a single color (using png_set_background; | ||
1700 | see below). Otherwise you must do the composition yourself and, in this case, | ||
1701 | you may need to call png_set_alpha_mode: | ||
1702 | |||
1703 | #if PNG_LIBPNG_VER >= 10504 | ||
1704 | png_set_alpha_mode(png_ptr, mode, screen_gamma); | ||
1705 | #else | ||
1706 | png_set_gamma(png_ptr, screen_gamma, 1.0/screen_gamma); | ||
1707 | #endif | ||
1708 | |||
1709 | The screen_gamma value is the same as the argument to png_set_gamma; however, | ||
1710 | how it affects the output depends on the mode. png_set_alpha_mode() sets the | ||
1711 | file gamma default to 1/screen_gamma, so normally you don't need to call | ||
1712 | png_set_gamma. If you need different defaults call png_set_gamma() before | ||
1713 | png_set_alpha_mode() - if you call it after it will override the settings made | ||
1714 | by png_set_alpha_mode(). | ||
1715 | |||
1716 | The mode is as follows: | ||
1717 | |||
1718 | PNG_ALPHA_PNG: The data is encoded according to the PNG specification. Red, | ||
1719 | green and blue, or gray, components are gamma encoded color | ||
1720 | values and are not premultiplied by the alpha value. The | ||
1721 | alpha value is a linear measure of the contribution of the | ||
1722 | pixel to the corresponding final output pixel. | ||
1723 | |||
1724 | You should normally use this format if you intend to perform | ||
1725 | color correction on the color values; most, maybe all, color | ||
1726 | correction software has no handling for the alpha channel and, | ||
1727 | anyway, the math to handle pre-multiplied component values is | ||
1728 | unnecessarily complex. | ||
1729 | |||
1730 | Before you do any arithmetic on the component values you need | ||
1731 | to remove the gamma encoding and multiply out the alpha | ||
1732 | channel. See the PNG specification for more detail. It is | ||
1733 | important to note that when an image with an alpha channel is | ||
1734 | scaled, linear encoded, pre-multiplied component values must | ||
1735 | be used! | ||
1736 | |||
1737 | The remaining modes assume you don't need to do any further color correction or | ||
1738 | that if you do, your color correction software knows all about alpha (it | ||
1739 | probably doesn't!) | ||
1740 | |||
1741 | PNG_ALPHA_STANDARD: The data libpng produces | ||
1742 | is encoded in the standard way | ||
1743 | assumed by most correctly written graphics software. | ||
1744 | The gamma encoding will be removed by libpng and the | ||
1745 | linear component values will be pre-multiplied by the | ||
1746 | alpha channel. | ||
1747 | |||
1748 | With this format the final image must be re-encoded to | ||
1749 | match the display gamma before the image is displayed. | ||
1750 | If your system doesn't do that, yet still seems to | ||
1751 | perform arithmetic on the pixels without decoding them, | ||
1752 | it is broken - check out the modes below. | ||
1753 | |||
1754 | With PNG_ALPHA_STANDARD libpng always produces linear | ||
1755 | component values, whatever screen_gamma you supply. The | ||
1756 | screen_gamma value is, however, used as a default for | ||
1757 | the file gamma if the PNG file has no gamma information. | ||
1758 | |||
1759 | If you call png_set_gamma() after png_set_alpha_mode() you | ||
1760 | will override the linear encoding. Instead the | ||
1761 | pre-multiplied pixel values will be gamma encoded but | ||
1762 | the alpha channel will still be linear. This may | ||
1763 | actually match the requirements of some broken software, | ||
1764 | but it is unlikely. | ||
1765 | |||
1766 | While linear 8-bit data is often used it has | ||
1767 | insufficient precision for any image with a reasonable | ||
1768 | dynamic range. To avoid problems, and if your software | ||
1769 | supports it, use png_set_expand_16() to force all | ||
1770 | components to 16 bits. | ||
1771 | |||
1772 | PNG_ALPHA_OPTIMIZED: This mode is the same | ||
1773 | as PNG_ALPHA_STANDARD except that | ||
1774 | completely opaque pixels are gamma encoded according to | ||
1775 | the screen_gamma value. Pixels with alpha less than 1.0 | ||
1776 | will still have linear components. | ||
1777 | |||
1778 | Use this format if you have control over your | ||
1779 | compositing software and do don't do other arithmetic | ||
1780 | (such as scaling) on the data you get from libpng. Your | ||
1781 | compositing software can simply copy opaque pixels to | ||
1782 | the output but still has linear values for the | ||
1783 | non-opaque pixels. | ||
1784 | |||
1785 | In normal compositing, where the alpha channel encodes | ||
1786 | partial pixel coverage (as opposed to broad area | ||
1787 | translucency), the inaccuracies of the 8-bit | ||
1788 | representation of non-opaque pixels are irrelevant. | ||
1789 | |||
1790 | You can also try this format if your software is broken; | ||
1791 | it might look better. | ||
1792 | |||
1793 | PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD; | ||
1794 | however, all component values, | ||
1795 | including the alpha channel are gamma encoded. This is | ||
1796 | an appropriate format to try if your software, or more | ||
1797 | likely hardware, is totally broken, i.e., if it performs | ||
1798 | linear arithmetic directly on gamma encoded values. | ||
1799 | |||
1800 | In most cases of broken software or hardware the bug in the final display | ||
1801 | manifests as a subtle halo around composited parts of the image. You may not | ||
1802 | even perceive this as a halo; the composited part of the image may simply appear | ||
1803 | separate from the background, as though it had been cut out of paper and pasted | ||
1804 | on afterward. | ||
1805 | |||
1806 | If you don't have to deal with bugs in software or hardware, or if you can fix | ||
1807 | them, there are three recommended ways of using png_set_alpha_mode(): | ||
1808 | |||
1809 | png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG, | ||
1810 | screen_gamma); | ||
1811 | |||
1812 | You can do color correction on the result (libpng does not currently | ||
1813 | support color correction internally). When you handle the alpha channel | ||
1814 | you need to undo the gamma encoding and multiply out the alpha. | ||
1815 | |||
1816 | png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD, | ||
1817 | screen_gamma); | ||
1818 | png_set_expand_16(png_ptr); | ||
1819 | |||
1820 | If you are using the high level interface, don't call png_set_expand_16(); | ||
1821 | instead pass PNG_TRANSFORM_EXPAND_16 to the interface. | ||
1822 | |||
1823 | With this mode you can't do color correction, but you can do arithmetic, | ||
1824 | including composition and scaling, on the data without further processing. | ||
1825 | |||
1826 | png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED, | ||
1827 | screen_gamma); | ||
1828 | |||
1829 | You can avoid the expansion to 16-bit components with this mode, but you | ||
1830 | lose the ability to scale the image or perform other linear arithmetic. | ||
1831 | All you can do is compose the result onto a matching output. Since this | ||
1832 | mode is libpng-specific you also need to write your own composition | ||
1833 | software. | ||
1834 | |||
1835 | If you don't need, or can't handle, the alpha channel you can call | ||
1836 | png_set_background() to remove it by compositing against a fixed color. Don't | ||
1837 | call png_set_strip_alpha() to do this - it will leave spurious pixel values in | ||
1838 | transparent parts of this image. | ||
1839 | |||
1840 | png_set_background(png_ptr, &background_color, | ||
1841 | PNG_BACKGROUND_GAMMA_SCREEN, 0, 1); | ||
1842 | |||
1843 | The background_color is an RGB or grayscale value according to the data format | ||
1844 | libpng will produce for you. Because you don't yet know the format of the PNG | ||
1845 | file, if you call png_set_background at this point you must arrange for the | ||
1846 | format produced by libpng to always have 8-bit or 16-bit components and then | ||
1847 | store the color as an 8-bit or 16-bit color as appropriate. The color contains | ||
1848 | separate gray and RGB component values, so you can let libpng produce gray or | ||
1849 | RGB output according to the input format, but low bit depth grayscale images | ||
1850 | must always be converted to at least 8-bit format. (Even though low bit depth | ||
1851 | grayscale images can't have an alpha channel they can have a transparent | ||
1852 | color!) | ||
1853 | |||
1854 | You set the transforms you need later, either as flags to the high level | ||
1855 | interface or libpng API calls for the low level interface. For reference the | ||
1856 | settings and API calls required are: | ||
1857 | |||
1858 | 8-bit values: | ||
1859 | PNG_TRANSFORM_SCALE_16 | PNG_EXPAND | ||
1860 | png_set_expand(png_ptr); png_set_scale_16(png_ptr); | ||
1861 | |||
1862 | If you must get exactly the same inaccurate results | ||
1863 | produced by default in versions prior to libpng-1.5.4, | ||
1864 | use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr) | ||
1865 | instead. | ||
1866 | |||
1867 | 16-bit values: | ||
1868 | PNG_TRANSFORM_EXPAND_16 | ||
1869 | png_set_expand_16(png_ptr); | ||
1870 | |||
1871 | In either case palette image data will be expanded to RGB. If you just want | ||
1872 | color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr) | ||
1873 | to the list. | ||
1874 | |||
1875 | Calling png_set_background before the PNG file header is read will not work | ||
1876 | prior to libpng-1.5.4. Because the failure may result in unexpected warnings or | ||
1877 | errors it is therefore much safer to call png_set_background after the head has | ||
1878 | been read. Unfortunately this means that prior to libpng-1.5.4 it cannot be | ||
1879 | used with the high level interface. | ||
1880 | |||
1881 | .SS The high-level read interface | ||
1882 | |||
1883 | At this point there are two ways to proceed; through the high-level | ||
1884 | read interface, or through a sequence of low-level read operations. | ||
1885 | You can use the high-level interface if (a) you are willing to read | ||
1886 | the entire image into memory, and (b) the input transformations | ||
1887 | you want to do are limited to the following set: | ||
1888 | |||
1889 | PNG_TRANSFORM_IDENTITY No transformation | ||
1890 | PNG_TRANSFORM_SCALE_16 Strip 16-bit samples to | ||
1891 | 8-bit accurately | ||
1892 | PNG_TRANSFORM_STRIP_16 Chop 16-bit samples to | ||
1893 | 8-bit less accurately | ||
1894 | PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel | ||
1895 | PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit | ||
1896 | samples to bytes | ||
1897 | PNG_TRANSFORM_PACKSWAP Change order of packed | ||
1898 | pixels to LSB first | ||
1899 | PNG_TRANSFORM_EXPAND Perform set_expand() | ||
1900 | PNG_TRANSFORM_INVERT_MONO Invert monochrome images | ||
1901 | PNG_TRANSFORM_SHIFT Normalize pixels to the | ||
1902 | sBIT depth | ||
1903 | PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA | ||
1904 | to BGRA | ||
1905 | PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA | ||
1906 | to AG | ||
1907 | PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity | ||
1908 | to transparency | ||
1909 | PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples | ||
1910 | PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples | ||
1911 | to RGB (or GA to RGBA) | ||
1912 | PNG_TRANSFORM_EXPAND_16 Expand samples to 16 bits | ||
1913 | |||
1914 | (This excludes setting a background color, doing gamma transformation, | ||
1915 | quantizing, and setting filler.) If this is the case, simply do this: | ||
1916 | |||
1917 | png_read_png(png_ptr, info_ptr, png_transforms, NULL) | ||
1918 | |||
1919 | where png_transforms is an integer containing the bitwise OR of some | ||
1920 | set of transformation flags. This call is equivalent to png_read_info(), | ||
1921 | followed the set of transformations indicated by the transform mask, | ||
1922 | then png_read_image(), and finally png_read_end(). | ||
1923 | |||
1924 | (The final parameter of this call is not yet used. Someday it might point | ||
1925 | to transformation parameters required by some future input transform.) | ||
1926 | |||
1927 | You must use png_transforms and not call any png_set_transform() functions | ||
1928 | when you use png_read_png(). | ||
1929 | |||
1930 | After you have called png_read_png(), you can retrieve the image data | ||
1931 | with | ||
1932 | |||
1933 | row_pointers = png_get_rows(png_ptr, info_ptr); | ||
1934 | |||
1935 | where row_pointers is an array of pointers to the pixel data for each row: | ||
1936 | |||
1937 | png_bytep row_pointers[height]; | ||
1938 | |||
1939 | If you know your image size and pixel size ahead of time, you can allocate | ||
1940 | row_pointers prior to calling png_read_png() with | ||
1941 | |||
1942 | if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) | ||
1943 | png_error (png_ptr, | ||
1944 | "Image is too tall to process in memory"); | ||
1945 | |||
1946 | if (width > PNG_UINT_32_MAX/pixel_size) | ||
1947 | png_error (png_ptr, | ||
1948 | "Image is too wide to process in memory"); | ||
1949 | |||
1950 | row_pointers = png_malloc(png_ptr, | ||
1951 | height*png_sizeof(png_bytep)); | ||
1952 | |||
1953 | for (int i=0; i<height, i++) | ||
1954 | row_pointers[i]=NULL; /* security precaution */ | ||
1955 | |||
1956 | for (int i=0; i<height, i++) | ||
1957 | row_pointers[i]=png_malloc(png_ptr, | ||
1958 | width*pixel_size); | ||
1959 | |||
1960 | png_set_rows(png_ptr, info_ptr, &row_pointers); | ||
1961 | |||
1962 | Alternatively you could allocate your image in one big block and define | ||
1963 | row_pointers[i] to point into the proper places in your block. | ||
1964 | |||
1965 | If you use png_set_rows(), the application is responsible for freeing | ||
1966 | row_pointers (and row_pointers[i], if they were separately allocated). | ||
1967 | |||
1968 | If you don't allocate row_pointers ahead of time, png_read_png() will | ||
1969 | do it, and it'll be free'ed by libpng when you call png_destroy_*(). | ||
1970 | |||
1971 | .SS The low-level read interface | ||
1972 | |||
1973 | If you are going the low-level route, you are now ready to read all | ||
1974 | the file information up to the actual image data. You do this with a | ||
1975 | call to png_read_info(). | ||
1976 | |||
1977 | png_read_info(png_ptr, info_ptr); | ||
1978 | |||
1979 | This will process all chunks up to but not including the image data. | ||
1980 | |||
1981 | This also copies some of the data from the PNG file into the decode structure | ||
1982 | for use in later transformations. Important information copied in is: | ||
1983 | |||
1984 | 1) The PNG file gamma from the gAMA chunk. This overwrites the default value | ||
1985 | provided by an earlier call to png_set_gamma or png_set_alpha_mode. | ||
1986 | |||
1987 | 2) Prior to libpng-1.5.4 the background color from a bKGd chunk. This | ||
1988 | damages the information provided by an earlier call to png_set_background | ||
1989 | resulting in unexpected behavior. Libpng-1.5.4 no longer does this. | ||
1990 | |||
1991 | 3) The number of significant bits in each component value. Libpng uses this to | ||
1992 | optimize gamma handling by reducing the internal lookup table sizes. | ||
1993 | |||
1994 | 4) The transparent color information from a tRNS chunk. This can be modified by | ||
1995 | a later call to png_set_tRNS. | ||
1996 | |||
1997 | .SS Querying the info structure | ||
1998 | |||
1999 | Functions are used to get the information from the info_ptr once it | ||
2000 | has been read. Note that these fields may not be completely filled | ||
2001 | in until png_read_end() has read the chunk data following the image. | ||
2002 | |||
2003 | png_get_IHDR(png_ptr, info_ptr, &width, &height, | ||
2004 | &bit_depth, &color_type, &interlace_type, | ||
2005 | &compression_type, &filter_method); | ||
2006 | |||
2007 | width - holds the width of the image | ||
2008 | in pixels (up to 2^31). | ||
2009 | |||
2010 | height - holds the height of the image | ||
2011 | in pixels (up to 2^31). | ||
2012 | |||
2013 | bit_depth - holds the bit depth of one of the | ||
2014 | image channels. (valid values are | ||
2015 | 1, 2, 4, 8, 16 and depend also on | ||
2016 | the color_type. See also | ||
2017 | significant bits (sBIT) below). | ||
2018 | |||
2019 | color_type - describes which color/alpha channels | ||
2020 | are present. | ||
2021 | PNG_COLOR_TYPE_GRAY | ||
2022 | (bit depths 1, 2, 4, 8, 16) | ||
2023 | PNG_COLOR_TYPE_GRAY_ALPHA | ||
2024 | (bit depths 8, 16) | ||
2025 | PNG_COLOR_TYPE_PALETTE | ||
2026 | (bit depths 1, 2, 4, 8) | ||
2027 | PNG_COLOR_TYPE_RGB | ||
2028 | (bit_depths 8, 16) | ||
2029 | PNG_COLOR_TYPE_RGB_ALPHA | ||
2030 | (bit_depths 8, 16) | ||
2031 | |||
2032 | PNG_COLOR_MASK_PALETTE | ||
2033 | PNG_COLOR_MASK_COLOR | ||
2034 | PNG_COLOR_MASK_ALPHA | ||
2035 | |||
2036 | interlace_type - (PNG_INTERLACE_NONE or | ||
2037 | PNG_INTERLACE_ADAM7) | ||
2038 | |||
2039 | compression_type - (must be PNG_COMPRESSION_TYPE_BASE | ||
2040 | for PNG 1.0) | ||
2041 | |||
2042 | filter_method - (must be PNG_FILTER_TYPE_BASE | ||
2043 | for PNG 1.0, and can also be | ||
2044 | PNG_INTRAPIXEL_DIFFERENCING if | ||
2045 | the PNG datastream is embedded in | ||
2046 | a MNG-1.0 datastream) | ||
2047 | |||
2048 | Any or all of interlace_type, compression_type, or | ||
2049 | filter_method can be NULL if you are | ||
2050 | not interested in their values. | ||
2051 | |||
2052 | Note that png_get_IHDR() returns 32-bit data into | ||
2053 | the application's width and height variables. | ||
2054 | This is an unsafe situation if these are 16-bit | ||
2055 | variables. In such situations, the | ||
2056 | png_get_image_width() and png_get_image_height() | ||
2057 | functions described below are safer. | ||
2058 | |||
2059 | width = png_get_image_width(png_ptr, | ||
2060 | info_ptr); | ||
2061 | |||
2062 | height = png_get_image_height(png_ptr, | ||
2063 | info_ptr); | ||
2064 | |||
2065 | bit_depth = png_get_bit_depth(png_ptr, | ||
2066 | info_ptr); | ||
2067 | |||
2068 | color_type = png_get_color_type(png_ptr, | ||
2069 | info_ptr); | ||
2070 | |||
2071 | interlace_type = png_get_interlace_type(png_ptr, | ||
2072 | info_ptr); | ||
2073 | |||
2074 | compression_type = png_get_compression_type(png_ptr, | ||
2075 | info_ptr); | ||
2076 | |||
2077 | filter_method = png_get_filter_type(png_ptr, | ||
2078 | info_ptr); | ||
2079 | |||
2080 | channels = png_get_channels(png_ptr, info_ptr); | ||
2081 | |||
2082 | channels - number of channels of info for the | ||
2083 | color type (valid values are 1 (GRAY, | ||
2084 | PALETTE), 2 (GRAY_ALPHA), 3 (RGB), | ||
2085 | 4 (RGB_ALPHA or RGB + filler byte)) | ||
2086 | |||
2087 | rowbytes = png_get_rowbytes(png_ptr, info_ptr); | ||
2088 | |||
2089 | rowbytes - number of bytes needed to hold a row | ||
2090 | |||
2091 | signature = png_get_signature(png_ptr, info_ptr); | ||
2092 | |||
2093 | signature - holds the signature read from the | ||
2094 | file (if any). The data is kept in | ||
2095 | the same offset it would be if the | ||
2096 | whole signature were read (i.e. if an | ||
2097 | application had already read in 4 | ||
2098 | bytes of signature before starting | ||
2099 | libpng, the remaining 4 bytes would | ||
2100 | be in signature[4] through signature[7] | ||
2101 | (see png_set_sig_bytes())). | ||
2102 | |||
2103 | These are also important, but their validity depends on whether the chunk | ||
2104 | has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and | ||
2105 | png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the | ||
2106 | data has been read, or zero if it is missing. The parameters to the | ||
2107 | png_get_<chunk> are set directly if they are simple data types, or a | ||
2108 | pointer into the info_ptr is returned for any complex types. | ||
2109 | |||
2110 | png_get_PLTE(png_ptr, info_ptr, &palette, | ||
2111 | &num_palette); | ||
2112 | |||
2113 | palette - the palette for the file | ||
2114 | (array of png_color) | ||
2115 | |||
2116 | num_palette - number of entries in the palette | ||
2117 | |||
2118 | png_get_gAMA(png_ptr, info_ptr, &file_gamma); | ||
2119 | png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma); | ||
2120 | |||
2121 | file_gamma - the gamma at which the file is | ||
2122 | written (PNG_INFO_gAMA) | ||
2123 | |||
2124 | int_file_gamma - 100,000 times the gamma at which the | ||
2125 | file is written | ||
2126 | |||
2127 | png_get_cHRM(png_ptr, info_ptr, &white_x, &white_y, &red_x, &red_y, | ||
2128 | &green_x, &green_y, &blue_x, &blue_y) | ||
2129 | png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z, &green_X, | ||
2130 | &green_Y, &green_Z, &blue_X, &blue_Y, &blue_Z) | ||
2131 | png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x, &int_white_y, | ||
2132 | &int_red_x, &int_red_y, &int_green_x, &int_green_y, | ||
2133 | &int_blue_x, &int_blue_y) | ||
2134 | png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y, | ||
2135 | &int_red_Z, &int_green_X, &int_green_Y, &int_green_Z, | ||
2136 | &int_blue_X, &int_blue_Y, &int_blue_Z) | ||
2137 | |||
2138 | {white,red,green,blue}_{x,y} | ||
2139 | A color space encoding specified using the chromaticities | ||
2140 | of the end points and the white point. (PNG_INFO_cHRM) | ||
2141 | |||
2142 | {red,green,blue}_{X,Y,Z} | ||
2143 | A color space encoding specified using the encoding end | ||
2144 | points - the CIE tristimulus specification of the intended | ||
2145 | color of the red, green and blue channels in the PNG RGB | ||
2146 | data. The white point is simply the sum of the three end | ||
2147 | points. (PNG_INFO_cHRM) | ||
2148 | |||
2149 | png_get_sRGB(png_ptr, info_ptr, &srgb_intent); | ||
2150 | |||
2151 | file_srgb_intent - the rendering intent (PNG_INFO_sRGB) | ||
2152 | The presence of the sRGB chunk | ||
2153 | means that the pixel data is in the | ||
2154 | sRGB color space. This chunk also | ||
2155 | implies specific values of gAMA and | ||
2156 | cHRM. | ||
2157 | |||
2158 | png_get_iCCP(png_ptr, info_ptr, &name, | ||
2159 | &compression_type, &profile, &proflen); | ||
2160 | |||
2161 | name - The profile name. | ||
2162 | |||
2163 | compression_type - The compression type; always | ||
2164 | PNG_COMPRESSION_TYPE_BASE for PNG 1.0. | ||
2165 | You may give NULL to this argument to | ||
2166 | ignore it. | ||
2167 | |||
2168 | profile - International Color Consortium color | ||
2169 | profile data. May contain NULs. | ||
2170 | |||
2171 | proflen - length of profile data in bytes. | ||
2172 | |||
2173 | png_get_sBIT(png_ptr, info_ptr, &sig_bit); | ||
2174 | |||
2175 | sig_bit - the number of significant bits for | ||
2176 | (PNG_INFO_sBIT) each of the gray, | ||
2177 | red, green, and blue channels, | ||
2178 | whichever are appropriate for the | ||
2179 | given color type (png_color_16) | ||
2180 | |||
2181 | png_get_tRNS(png_ptr, info_ptr, &trans_alpha, | ||
2182 | &num_trans, &trans_color); | ||
2183 | |||
2184 | trans_alpha - array of alpha (transparency) | ||
2185 | entries for palette (PNG_INFO_tRNS) | ||
2186 | |||
2187 | num_trans - number of transparent entries | ||
2188 | (PNG_INFO_tRNS) | ||
2189 | |||
2190 | trans_color - graylevel or color sample values of | ||
2191 | the single transparent color for | ||
2192 | non-paletted images (PNG_INFO_tRNS) | ||
2193 | |||
2194 | png_get_hIST(png_ptr, info_ptr, &hist); | ||
2195 | (PNG_INFO_hIST) | ||
2196 | |||
2197 | hist - histogram of palette (array of | ||
2198 | png_uint_16) | ||
2199 | |||
2200 | png_get_tIME(png_ptr, info_ptr, &mod_time); | ||
2201 | |||
2202 | mod_time - time image was last modified | ||
2203 | (PNG_VALID_tIME) | ||
2204 | |||
2205 | png_get_bKGD(png_ptr, info_ptr, &background); | ||
2206 | |||
2207 | background - background color (of type | ||
2208 | png_color_16p) (PNG_VALID_bKGD) | ||
2209 | valid 16-bit red, green and blue | ||
2210 | values, regardless of color_type | ||
2211 | |||
2212 | num_comments = png_get_text(png_ptr, info_ptr, | ||
2213 | &text_ptr, &num_text); | ||
2214 | |||
2215 | num_comments - number of comments | ||
2216 | |||
2217 | text_ptr - array of png_text holding image | ||
2218 | comments | ||
2219 | |||
2220 | text_ptr[i].compression - type of compression used | ||
2221 | on "text" PNG_TEXT_COMPRESSION_NONE | ||
2222 | PNG_TEXT_COMPRESSION_zTXt | ||
2223 | PNG_ITXT_COMPRESSION_NONE | ||
2224 | PNG_ITXT_COMPRESSION_zTXt | ||
2225 | |||
2226 | text_ptr[i].key - keyword for comment. Must contain | ||
2227 | 1-79 characters. | ||
2228 | |||
2229 | text_ptr[i].text - text comments for current | ||
2230 | keyword. Can be empty. | ||
2231 | |||
2232 | text_ptr[i].text_length - length of text string, | ||
2233 | after decompression, 0 for iTXt | ||
2234 | |||
2235 | text_ptr[i].itxt_length - length of itxt string, | ||
2236 | after decompression, 0 for tEXt/zTXt | ||
2237 | |||
2238 | text_ptr[i].lang - language of comment (empty | ||
2239 | string for unknown). | ||
2240 | |||
2241 | text_ptr[i].lang_key - keyword in UTF-8 | ||
2242 | (empty string for unknown). | ||
2243 | |||
2244 | Note that the itxt_length, lang, and lang_key | ||
2245 | members of the text_ptr structure only exist when the | ||
2246 | library is built with iTXt chunk support. Prior to | ||
2247 | libpng-1.4.0 the library was built by default without | ||
2248 | iTXt support. Also note that when iTXt is supported, | ||
2249 | they contain NULL pointers when the "compression" | ||
2250 | field contains PNG_TEXT_COMPRESSION_NONE or | ||
2251 | PNG_TEXT_COMPRESSION_zTXt. | ||
2252 | |||
2253 | num_text - number of comments (same as | ||
2254 | num_comments; you can put NULL here | ||
2255 | to avoid the duplication) | ||
2256 | |||
2257 | Note while png_set_text() will accept text, language, | ||
2258 | and translated keywords that can be NULL pointers, the | ||
2259 | structure returned by png_get_text will always contain | ||
2260 | regular zero-terminated C strings. They might be | ||
2261 | empty strings but they will never be NULL pointers. | ||
2262 | |||
2263 | num_spalettes = png_get_sPLT(png_ptr, info_ptr, | ||
2264 | &palette_ptr); | ||
2265 | |||
2266 | num_spalettes - number of sPLT chunks read. | ||
2267 | |||
2268 | palette_ptr - array of palette structures holding | ||
2269 | contents of one or more sPLT chunks | ||
2270 | read. | ||
2271 | |||
2272 | png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, | ||
2273 | &unit_type); | ||
2274 | |||
2275 | offset_x - positive offset from the left edge | ||
2276 | of the screen (can be negative) | ||
2277 | |||
2278 | offset_y - positive offset from the top edge | ||
2279 | of the screen (can be negative) | ||
2280 | |||
2281 | unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER | ||
2282 | |||
2283 | png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, | ||
2284 | &unit_type); | ||
2285 | |||
2286 | res_x - pixels/unit physical resolution in | ||
2287 | x direction | ||
2288 | |||
2289 | res_y - pixels/unit physical resolution in | ||
2290 | x direction | ||
2291 | |||
2292 | unit_type - PNG_RESOLUTION_UNKNOWN, | ||
2293 | PNG_RESOLUTION_METER | ||
2294 | |||
2295 | png_get_sCAL(png_ptr, info_ptr, &unit, &width, | ||
2296 | &height) | ||
2297 | |||
2298 | unit - physical scale units (an integer) | ||
2299 | |||
2300 | width - width of a pixel in physical scale units | ||
2301 | |||
2302 | height - height of a pixel in physical scale units | ||
2303 | (width and height are doubles) | ||
2304 | |||
2305 | png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, | ||
2306 | &height) | ||
2307 | |||
2308 | unit - physical scale units (an integer) | ||
2309 | |||
2310 | width - width of a pixel in physical scale units | ||
2311 | (expressed as a string) | ||
2312 | |||
2313 | height - height of a pixel in physical scale units | ||
2314 | (width and height are strings like "2.54") | ||
2315 | |||
2316 | num_unknown_chunks = png_get_unknown_chunks(png_ptr, | ||
2317 | info_ptr, &unknowns) | ||
2318 | |||
2319 | unknowns - array of png_unknown_chunk | ||
2320 | structures holding unknown chunks | ||
2321 | |||
2322 | unknowns[i].name - name of unknown chunk | ||
2323 | |||
2324 | unknowns[i].data - data of unknown chunk | ||
2325 | |||
2326 | unknowns[i].size - size of unknown chunk's data | ||
2327 | |||
2328 | unknowns[i].location - position of chunk in file | ||
2329 | |||
2330 | The value of "i" corresponds to the order in which the | ||
2331 | chunks were read from the PNG file or inserted with the | ||
2332 | png_set_unknown_chunks() function. | ||
2333 | |||
2334 | The value of "location" is a bitwise "or" of | ||
2335 | |||
2336 | PNG_HAVE_IHDR (0x01) | ||
2337 | PNG_HAVE_PLTE (0x02) | ||
2338 | PNG_AFTER_IDAT (0x08) | ||
2339 | |||
2340 | The data from the pHYs chunk can be retrieved in several convenient | ||
2341 | forms: | ||
2342 | |||
2343 | res_x = png_get_x_pixels_per_meter(png_ptr, | ||
2344 | info_ptr) | ||
2345 | |||
2346 | res_y = png_get_y_pixels_per_meter(png_ptr, | ||
2347 | info_ptr) | ||
2348 | |||
2349 | res_x_and_y = png_get_pixels_per_meter(png_ptr, | ||
2350 | info_ptr) | ||
2351 | |||
2352 | res_x = png_get_x_pixels_per_inch(png_ptr, | ||
2353 | info_ptr) | ||
2354 | |||
2355 | res_y = png_get_y_pixels_per_inch(png_ptr, | ||
2356 | info_ptr) | ||
2357 | |||
2358 | res_x_and_y = png_get_pixels_per_inch(png_ptr, | ||
2359 | info_ptr) | ||
2360 | |||
2361 | aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, | ||
2362 | info_ptr) | ||
2363 | |||
2364 | Each of these returns 0 [signifying "unknown"] if | ||
2365 | the data is not present or if res_x is 0; | ||
2366 | res_x_and_y is 0 if res_x != res_y | ||
2367 | |||
2368 | Note that because of the way the resolutions are | ||
2369 | stored internally, the inch conversions won't | ||
2370 | come out to exactly even number. For example, | ||
2371 | 72 dpi is stored as 0.28346 pixels/meter, and | ||
2372 | when this is retrieved it is 71.9988 dpi, so | ||
2373 | be sure to round the returned value appropriately | ||
2374 | if you want to display a reasonable-looking result. | ||
2375 | |||
2376 | The data from the oFFs chunk can be retrieved in several convenient | ||
2377 | forms: | ||
2378 | |||
2379 | x_offset = png_get_x_offset_microns(png_ptr, info_ptr); | ||
2380 | |||
2381 | y_offset = png_get_y_offset_microns(png_ptr, info_ptr); | ||
2382 | |||
2383 | x_offset = png_get_x_offset_inches(png_ptr, info_ptr); | ||
2384 | |||
2385 | y_offset = png_get_y_offset_inches(png_ptr, info_ptr); | ||
2386 | |||
2387 | Each of these returns 0 [signifying "unknown" if both | ||
2388 | x and y are 0] if the data is not present or if the | ||
2389 | chunk is present but the unit is the pixel. The | ||
2390 | remark about inexact inch conversions applies here | ||
2391 | as well, because a value in inches can't always be | ||
2392 | converted to microns and back without some loss | ||
2393 | of precision. | ||
2394 | |||
2395 | For more information, see the | ||
2396 | PNG specification for chunk contents. Be careful with trusting | ||
2397 | rowbytes, as some of the transformations could increase the space | ||
2398 | needed to hold a row (expand, filler, gray_to_rgb, etc.). | ||
2399 | See png_read_update_info(), below. | ||
2400 | |||
2401 | A quick word about text_ptr and num_text. PNG stores comments in | ||
2402 | keyword/text pairs, one pair per chunk, with no limit on the number | ||
2403 | of text chunks, and a 2^31 byte limit on their size. While there are | ||
2404 | suggested keywords, there is no requirement to restrict the use to these | ||
2405 | strings. It is strongly suggested that keywords and text be sensible | ||
2406 | to humans (that's the point), so don't use abbreviations. Non-printing | ||
2407 | symbols are not allowed. See the PNG specification for more details. | ||
2408 | There is also no requirement to have text after the keyword. | ||
2409 | |||
2410 | Keywords should be limited to 79 Latin-1 characters without leading or | ||
2411 | trailing spaces, but non-consecutive spaces are allowed within the | ||
2412 | keyword. It is possible to have the same keyword any number of times. | ||
2413 | The text_ptr is an array of png_text structures, each holding a | ||
2414 | pointer to a language string, a pointer to a keyword and a pointer to | ||
2415 | a text string. The text string, language code, and translated | ||
2416 | keyword may be empty or NULL pointers. The keyword/text | ||
2417 | pairs are put into the array in the order that they are received. | ||
2418 | However, some or all of the text chunks may be after the image, so, to | ||
2419 | make sure you have read all the text chunks, don't mess with these | ||
2420 | until after you read the stuff after the image. This will be | ||
2421 | mentioned again below in the discussion that goes with png_read_end(). | ||
2422 | |||
2423 | .SS Input transformations | ||
2424 | |||
2425 | After you've read the header information, you can set up the library | ||
2426 | to handle any special transformations of the image data. The various | ||
2427 | ways to transform the data will be described in the order that they | ||
2428 | should occur. This is important, as some of these change the color | ||
2429 | type and/or bit depth of the data, and some others only work on | ||
2430 | certain color types and bit depths. | ||
2431 | |||
2432 | Transformations you request are ignored if they don't have any meaning for a | ||
2433 | particular input data format. However some transformations can have an effect | ||
2434 | as a result of a previous transformation. If you specify a contradictory set of | ||
2435 | transformations, for example both adding and removing the alpha channel, you | ||
2436 | cannot predict the final result. | ||
2437 | |||
2438 | The color used for the transparency values should be supplied in the same | ||
2439 | format/depth as the current image data. It is stored in the same format/depth | ||
2440 | as the image data in a tRNS chunk, so this is what libpng expects for this data. | ||
2441 | |||
2442 | The color used for the background value depends on the need_expand argument as | ||
2443 | described below. | ||
2444 | |||
2445 | Data will be decoded into the supplied row buffers packed into bytes | ||
2446 | unless the library has been told to transform it into another format. | ||
2447 | For example, 4 bit/pixel paletted or grayscale data will be returned | ||
2448 | 2 pixels/byte with the leftmost pixel in the high-order bits of the | ||
2449 | byte, unless png_set_packing() is called. 8-bit RGB data will be stored | ||
2450 | in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() | ||
2451 | is called to insert filler bytes, either before or after each RGB triplet. | ||
2452 | 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant | ||
2453 | byte of the color value first, unless png_set_scale_16() is called to | ||
2454 | transform it to regular RGB RGB triplets, or png_set_filler() or | ||
2455 | png_set_add alpha() is called to insert filler bytes, either before or | ||
2456 | after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can | ||
2457 | be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(), | ||
2458 | or png_set_scale_16(). | ||
2459 | |||
2460 | The following code transforms grayscale images of less than 8 to 8 bits, | ||
2461 | changes paletted images to RGB, and adds a full alpha channel if there is | ||
2462 | transparency information in a tRNS chunk. This is most useful on | ||
2463 | grayscale images with bit depths of 2 or 4 or if there is a multiple-image | ||
2464 | viewing application that wishes to treat all images in the same way. | ||
2465 | |||
2466 | if (color_type == PNG_COLOR_TYPE_PALETTE) | ||
2467 | png_set_palette_to_rgb(png_ptr); | ||
2468 | |||
2469 | if (png_get_valid(png_ptr, info_ptr, | ||
2470 | PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); | ||
2471 | |||
2472 | if (color_type == PNG_COLOR_TYPE_GRAY && | ||
2473 | bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); | ||
2474 | |||
2475 | The first two functions are actually aliases for png_set_expand(), added | ||
2476 | in libpng version 1.0.4, with the function names expanded to improve code | ||
2477 | readability. In some future version they may actually do different | ||
2478 | things. | ||
2479 | |||
2480 | As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was | ||
2481 | added. It expands the sample depth without changing tRNS to alpha. | ||
2482 | |||
2483 | As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as | ||
2484 | png_set_expand(); however, the resultant channels have 16 bits rather than 8. | ||
2485 | Use this when the output color or gray channels are made linear to avoid fairly | ||
2486 | severe accuracy loss. | ||
2487 | |||
2488 | if (bit_depth < 16) | ||
2489 | png_set_expand_16(png_ptr); | ||
2490 | |||
2491 | PNG can have files with 16 bits per channel. If you only can handle | ||
2492 | 8 bits per channel, this will strip the pixels down to 8-bit. | ||
2493 | |||
2494 | if (bit_depth == 16) | ||
2495 | #if PNG_LIBPNG_VER >= 10504 | ||
2496 | png_set_scale_16(png_ptr); | ||
2497 | #else | ||
2498 | png_set_strip_16(png_ptr); | ||
2499 | #endif | ||
2500 | |||
2501 | (The more accurate "png_set_scale_16()" API became available in libpng version | ||
2502 | 1.5.4). | ||
2503 | |||
2504 | If you need to process the alpha channel on the image separately from the image | ||
2505 | data (for example if you convert it to a bitmap mask) it is possible to have | ||
2506 | libpng strip the channel leaving just RGB or gray data: | ||
2507 | |||
2508 | if (color_type & PNG_COLOR_MASK_ALPHA) | ||
2509 | png_set_strip_alpha(png_ptr); | ||
2510 | |||
2511 | If you strip the alpha channel you need to find some other way of dealing with | ||
2512 | the information. If, instead, you want to convert the image to an opaque | ||
2513 | version with no alpha channel use png_set_background; see below. | ||
2514 | |||
2515 | As of libpng version 1.5.2, almost all useful expansions are supported, the | ||
2516 | major ommissions are conversion of grayscale to indexed images (which can be | ||
2517 | done trivially in the application) and conversion of indexed to grayscale (which | ||
2518 | can be done by a trivial manipulation of the palette.) | ||
2519 | |||
2520 | In the following table, the 01 means grayscale with depth<8, 31 means | ||
2521 | indexed with depth<8, other numerals represent the color type, "T" means | ||
2522 | the tRNS chunk is present, A means an alpha channel is present, and O | ||
2523 | means tRNS or alpha is present but all pixels in the image are opaque. | ||
2524 | |||
2525 | FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O | ||
2526 | TO | ||
2527 | 01 - [G] - - - - - - - - - - - - - | ||
2528 | 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q | ||
2529 | 0 1 G + . . G G G G G G B B GB GB | ||
2530 | 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt | ||
2531 | 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt | ||
2532 | 2 C P C C C + . . C - - CB CB B B | ||
2533 | 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt | ||
2534 | 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt | ||
2535 | 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q | ||
2536 | 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt | ||
2537 | 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt | ||
2538 | 4A lA G A T T GA GT GT GA GT GT + BA G GBA | ||
2539 | 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G | ||
2540 | 6A CA PA CA C C A T tT PA P P C CBA + BA | ||
2541 | 6O CA PBA CA C C A tT T PA P P CBA C BA + | ||
2542 | |||
2543 | Within the matrix, | ||
2544 | "+" identifies entries where 'from' and 'to' are the same. | ||
2545 | "-" means the transformation is not supported. | ||
2546 | "." means nothing is necessary (a tRNS chunk can just be ignored). | ||
2547 | "t" means the transformation is obtained by png_set_tRNS. | ||
2548 | "A" means the transformation is obtained by png_set_add_alpha(). | ||
2549 | "X" means the transformation is obtained by png_set_expand(). | ||
2550 | "1" means the transformation is obtained by | ||
2551 | png_set_expand_gray_1_2_4_to_8() (and by png_set_expand() if there | ||
2552 | is no transparency in the original or the final format). | ||
2553 | "C" means the transformation is obtained by png_set_gray_to_rgb(). | ||
2554 | "G" means the transformation is obtained by png_set_rgb_to_gray(). | ||
2555 | "P" means the transformation is obtained by | ||
2556 | png_set_expand_palette_to_rgb(). | ||
2557 | "p" means the transformation is obtained by png_set_packing(). | ||
2558 | "Q" means the transformation is obtained by png_set_quantize(). | ||
2559 | "T" means the transformation is obtained by png_set_tRNS_to_alpha(). | ||
2560 | "B" means the transformation is obtained by png_set_background(), or | ||
2561 | png_strip_alpha(). | ||
2562 | |||
2563 | When an entry has multiple transforms listed all are required to cause the | ||
2564 | right overall transformation. When two transforms are separated by a comma | ||
2565 | either will do the job. When transforms are enclosed in [] the transform should | ||
2566 | do the job but this is currently unimplemented - a different format will result | ||
2567 | if the suggested transformations are used. | ||
2568 | |||
2569 | In PNG files, the alpha channel in an image | ||
2570 | is the level of opacity. If you need the alpha channel in an image to | ||
2571 | be the level of transparency instead of opacity, you can invert the | ||
2572 | alpha channel (or the tRNS chunk data) after it's read, so that 0 is | ||
2573 | fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit | ||
2574 | images) is fully transparent, with | ||
2575 | |||
2576 | png_set_invert_alpha(png_ptr); | ||
2577 | |||
2578 | PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as | ||
2579 | they can, resulting in, for example, 8 pixels per byte for 1 bit | ||
2580 | files. This code expands to 1 pixel per byte without changing the | ||
2581 | values of the pixels: | ||
2582 | |||
2583 | if (bit_depth < 8) | ||
2584 | png_set_packing(png_ptr); | ||
2585 | |||
2586 | PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels | ||
2587 | stored in a PNG image have been "scaled" or "shifted" up to the next | ||
2588 | higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] | ||
2589 | to 8 bits/sample in the range [0, 255]). However, it is also possible | ||
2590 | to convert the PNG pixel data back to the original bit depth of the | ||
2591 | image. This call reduces the pixels back down to the original bit depth: | ||
2592 | |||
2593 | png_color_8p sig_bit; | ||
2594 | |||
2595 | if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) | ||
2596 | png_set_shift(png_ptr, sig_bit); | ||
2597 | |||
2598 | PNG files store 3-color pixels in red, green, blue order. This code | ||
2599 | changes the storage of the pixels to blue, green, red: | ||
2600 | |||
2601 | if (color_type == PNG_COLOR_TYPE_RGB || | ||
2602 | color_type == PNG_COLOR_TYPE_RGB_ALPHA) | ||
2603 | png_set_bgr(png_ptr); | ||
2604 | |||
2605 | PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them | ||
2606 | into 4 or 8 bytes for windowing systems that need them in this format: | ||
2607 | |||
2608 | if (color_type == PNG_COLOR_TYPE_RGB) | ||
2609 | png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); | ||
2610 | |||
2611 | where "filler" is the 8 or 16-bit number to fill with, and the location is | ||
2612 | either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether | ||
2613 | you want the filler before the RGB or after. This transformation | ||
2614 | does not affect images that already have full alpha channels. To add an | ||
2615 | opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which | ||
2616 | will generate RGBA pixels. | ||
2617 | |||
2618 | Note that png_set_filler() does not change the color type. If you want | ||
2619 | to do that, you can add a true alpha channel with | ||
2620 | |||
2621 | if (color_type == PNG_COLOR_TYPE_RGB || | ||
2622 | color_type == PNG_COLOR_TYPE_GRAY) | ||
2623 | png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); | ||
2624 | |||
2625 | where "filler" contains the alpha value to assign to each pixel. | ||
2626 | This function was added in libpng-1.2.7. | ||
2627 | |||
2628 | If you are reading an image with an alpha channel, and you need the | ||
2629 | data as ARGB instead of the normal PNG format RGBA: | ||
2630 | |||
2631 | if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) | ||
2632 | png_set_swap_alpha(png_ptr); | ||
2633 | |||
2634 | For some uses, you may want a grayscale image to be represented as | ||
2635 | RGB. This code will do that conversion: | ||
2636 | |||
2637 | if (color_type == PNG_COLOR_TYPE_GRAY || | ||
2638 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA) | ||
2639 | png_set_gray_to_rgb(png_ptr); | ||
2640 | |||
2641 | Conversely, you can convert an RGB or RGBA image to grayscale or grayscale | ||
2642 | with alpha. | ||
2643 | |||
2644 | if (color_type == PNG_COLOR_TYPE_RGB || | ||
2645 | color_type == PNG_COLOR_TYPE_RGB_ALPHA) | ||
2646 | png_set_rgb_to_gray(png_ptr, error_action, double red_weight, | ||
2647 | double green_weight); | ||
2648 | |||
2649 | error_action = 1: silently do the conversion | ||
2650 | |||
2651 | error_action = 2: issue a warning if the original | ||
2652 | image has any pixel where | ||
2653 | red != green or red != blue | ||
2654 | |||
2655 | error_action = 3: issue an error and abort the | ||
2656 | conversion if the original | ||
2657 | image has any pixel where | ||
2658 | red != green or red != blue | ||
2659 | |||
2660 | red_weight: weight of red component | ||
2661 | |||
2662 | green_weight: weight of green component | ||
2663 | If either weight is negative, default | ||
2664 | weights are used. | ||
2665 | |||
2666 | In the corresponding fixed point API the red_weight and green_weight values are | ||
2667 | simply scaled by 100,000: | ||
2668 | |||
2669 | png_set_rgb_to_gray(png_ptr, error_action, png_fixed_point red_weight, | ||
2670 | png_fixed_point green_weight); | ||
2671 | |||
2672 | If you have set error_action = 1 or 2, you can | ||
2673 | later check whether the image really was gray, after processing | ||
2674 | the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. | ||
2675 | It will return a png_byte that is zero if the image was gray or | ||
2676 | 1 if there were any non-gray pixels. Background and sBIT data | ||
2677 | will be silently converted to grayscale, using the green channel | ||
2678 | data for sBIT, regardless of the error_action setting. | ||
2679 | |||
2680 | The default values come from the PNG file cHRM chunk if present; otherwise, the | ||
2681 | defaults correspond to the ITU-R recommendation 709, and also the sRGB color | ||
2682 | space, as recommended in the Charles Poynton's Colour FAQ, | ||
2683 | <http://www.poynton.com/>, in section 9: | ||
2684 | |||
2685 | <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9> | ||
2686 | |||
2687 | Y = 0.2126 * R + 0.7152 * G + 0.0722 * B | ||
2688 | |||
2689 | Previous versions of this document, 1998 through 2002, recommended a slightly | ||
2690 | different formula: | ||
2691 | |||
2692 | Y = 0.212671 * R + 0.715160 * G + 0.072169 * B | ||
2693 | |||
2694 | Libpng uses an integer approximation: | ||
2695 | |||
2696 | Y = (6968 * R + 23434 * G + 2366 * B)/32768 | ||
2697 | |||
2698 | The calculation is done in a linear colorspace, if the image gamma | ||
2699 | can be determined. | ||
2700 | |||
2701 | The png_set_background() function has been described already; it tells libpng to | ||
2702 | composite images with alpha or simple transparency against the supplied | ||
2703 | background color. For compatibility with versions of libpng earlier than | ||
2704 | libpng-1.5.4 it is recommended that you call the function after reading the file | ||
2705 | header, even if you don't want to use the color in a bKGD chunk, if one exists. | ||
2706 | |||
2707 | If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), | ||
2708 | you may use this color, or supply another color more suitable for | ||
2709 | the current display (e.g., the background color from a web page). You | ||
2710 | need to tell libpng how the color is represented, both the format of the | ||
2711 | component values in the color (the number of bits) and the gamma encoding of the | ||
2712 | color. The function takes two arguments, background_gamma_mode and need_expand | ||
2713 | to convey this information, however only two combinations are likely to be | ||
2714 | useful: | ||
2715 | |||
2716 | png_color_16 my_background; | ||
2717 | png_color_16p image_background; | ||
2718 | |||
2719 | if (png_get_bKGD(png_ptr, info_ptr, &image_background)) | ||
2720 | png_set_background(png_ptr, image_background, | ||
2721 | PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1); | ||
2722 | else | ||
2723 | png_set_background(png_ptr, &my_background, | ||
2724 | PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1); | ||
2725 | |||
2726 | The second call was described above - my_background is in the format of the | ||
2727 | final, display, output produced by libpng. Because you now know the format of | ||
2728 | the PNG it is possible to avoid the need to choose either 8-bit or 16-bit | ||
2729 | output and to retain palette images (the palette colors will be modified | ||
2730 | appropriately and the tRNS chunk removed.) However, if you are doing this, | ||
2731 | take great care not to ask for transformations without checking first that | ||
2732 | they apply! | ||
2733 | |||
2734 | In the first call the background color has the original bit depth and color type | ||
2735 | of the PNG file. So, for palette images the color is supplied as a palette | ||
2736 | index and for low bit greyscale images the color is a reduced bit value in | ||
2737 | image_background->gray. | ||
2738 | |||
2739 | If you didn't call png_set_gamma() before reading the file header, for example | ||
2740 | if you need your code to remain compatible with older versions of libpng prior | ||
2741 | to libpng-1.5.4, this is the place to call it. | ||
2742 | |||
2743 | Do not call it if you called png_set_alpha_mode(); doing so will damage the | ||
2744 | settings put in place by png_set_alpha_mode(). (If png_set_alpha_mode() is | ||
2745 | supported then you can certainly do png_set_gamma() before reading the PNG | ||
2746 | header.) | ||
2747 | |||
2748 | This API unconditionally sets the screen and file gamma values, so it will | ||
2749 | override the value in the PNG file unless it is called before the PNG file | ||
2750 | reading starts. For this reason you must always call it with the PNG file | ||
2751 | value when you call it in this position: | ||
2752 | |||
2753 | if (png_get_gAMA(png_ptr, info_ptr, &file_gamma)) | ||
2754 | png_set_gamma(png_ptr, screen_gamma, file_gamma); | ||
2755 | |||
2756 | else | ||
2757 | png_set_gamma(png_ptr, screen_gamma, 0.45455); | ||
2758 | |||
2759 | If you need to reduce an RGB file to a paletted file, or if a paletted | ||
2760 | file has more entries then will fit on your screen, png_set_quantize() | ||
2761 | will do that. Note that this is a simple match quantization that merely | ||
2762 | finds the closest color available. This should work fairly well with | ||
2763 | optimized palettes, but fairly badly with linear color cubes. If you | ||
2764 | pass a palette that is larger than maximum_colors, the file will | ||
2765 | reduce the number of colors in the palette so it will fit into | ||
2766 | maximum_colors. If there is a histogram, libpng will use it to make | ||
2767 | more intelligent choices when reducing the palette. If there is no | ||
2768 | histogram, it may not do as good a job. | ||
2769 | |||
2770 | if (color_type & PNG_COLOR_MASK_COLOR) | ||
2771 | { | ||
2772 | if (png_get_valid(png_ptr, info_ptr, | ||
2773 | PNG_INFO_PLTE)) | ||
2774 | { | ||
2775 | png_uint_16p histogram = NULL; | ||
2776 | |||
2777 | png_get_hIST(png_ptr, info_ptr, | ||
2778 | &histogram); | ||
2779 | png_set_quantize(png_ptr, palette, num_palette, | ||
2780 | max_screen_colors, histogram, 1); | ||
2781 | } | ||
2782 | |||
2783 | else | ||
2784 | { | ||
2785 | png_color std_color_cube[MAX_SCREEN_COLORS] = | ||
2786 | { ... colors ... }; | ||
2787 | |||
2788 | png_set_quantize(png_ptr, std_color_cube, | ||
2789 | MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, | ||
2790 | NULL,0); | ||
2791 | } | ||
2792 | } | ||
2793 | |||
2794 | PNG files describe monochrome as black being zero and white being one. | ||
2795 | The following code will reverse this (make black be one and white be | ||
2796 | zero): | ||
2797 | |||
2798 | if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY) | ||
2799 | png_set_invert_mono(png_ptr); | ||
2800 | |||
2801 | This function can also be used to invert grayscale and gray-alpha images: | ||
2802 | |||
2803 | if (color_type == PNG_COLOR_TYPE_GRAY || | ||
2804 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA) | ||
2805 | png_set_invert_mono(png_ptr); | ||
2806 | |||
2807 | PNG files store 16-bit pixels in network byte order (big-endian, | ||
2808 | ie. most significant bits first). This code changes the storage to the | ||
2809 | other way (little-endian, i.e. least significant bits first, the | ||
2810 | way PCs store them): | ||
2811 | |||
2812 | if (bit_depth == 16) | ||
2813 | png_set_swap(png_ptr); | ||
2814 | |||
2815 | If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you | ||
2816 | need to change the order the pixels are packed into bytes, you can use: | ||
2817 | |||
2818 | if (bit_depth < 8) | ||
2819 | png_set_packswap(png_ptr); | ||
2820 | |||
2821 | Finally, you can write your own transformation function if none of | ||
2822 | the existing ones meets your needs. This is done by setting a callback | ||
2823 | with | ||
2824 | |||
2825 | png_set_read_user_transform_fn(png_ptr, | ||
2826 | read_transform_fn); | ||
2827 | |||
2828 | You must supply the function | ||
2829 | |||
2830 | void read_transform_fn(png_structp png_ptr, png_row_infop | ||
2831 | row_info, png_bytep data) | ||
2832 | |||
2833 | See pngtest.c for a working example. Your function will be called | ||
2834 | after all of the other transformations have been processed. Take care with | ||
2835 | interlaced images if you do the interlace yourself - the width of the row is the | ||
2836 | width in 'row_info', not the overall image width. | ||
2837 | |||
2838 | If supported, libpng provides two information routines that you can use to find | ||
2839 | where you are in processing the image: | ||
2840 | |||
2841 | png_get_current_pass_number(png_structp png_ptr); | ||
2842 | png_get_current_row_number(png_structp png_ptr); | ||
2843 | |||
2844 | Don't try using these outside a transform callback - firstly they are only | ||
2845 | supported if user transforms are supported, secondly they may well return | ||
2846 | unexpected results unless the row is actually being processed at the moment they | ||
2847 | are called. | ||
2848 | |||
2849 | With interlaced | ||
2850 | images the value returned is the row in the input sub-image image. Use | ||
2851 | PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to | ||
2852 | find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). | ||
2853 | |||
2854 | The discussion of interlace handling above contains more information on how to | ||
2855 | use these values. | ||
2856 | |||
2857 | You can also set up a pointer to a user structure for use by your | ||
2858 | callback function, and you can inform libpng that your transform | ||
2859 | function will change the number of channels or bit depth with the | ||
2860 | function | ||
2861 | |||
2862 | png_set_user_transform_info(png_ptr, user_ptr, | ||
2863 | user_depth, user_channels); | ||
2864 | |||
2865 | The user's application, not libpng, is responsible for allocating and | ||
2866 | freeing any memory required for the user structure. | ||
2867 | |||
2868 | You can retrieve the pointer via the function | ||
2869 | png_get_user_transform_ptr(). For example: | ||
2870 | |||
2871 | voidp read_user_transform_ptr = | ||
2872 | png_get_user_transform_ptr(png_ptr); | ||
2873 | |||
2874 | The last thing to handle is interlacing; this is covered in detail below, | ||
2875 | but you must call the function here if you want libpng to handle expansion | ||
2876 | of the interlaced image. | ||
2877 | |||
2878 | number_of_passes = png_set_interlace_handling(png_ptr); | ||
2879 | |||
2880 | After setting the transformations, libpng can update your png_info | ||
2881 | structure to reflect any transformations you've requested with this | ||
2882 | call. | ||
2883 | |||
2884 | png_read_update_info(png_ptr, info_ptr); | ||
2885 | |||
2886 | This is most useful to update the info structure's rowbytes | ||
2887 | field so you can use it to allocate your image memory. This function | ||
2888 | will also update your palette with the correct screen_gamma and | ||
2889 | background if these have been given with the calls above. You may | ||
2890 | only call png_read_update_info() once with a particular info_ptr. | ||
2891 | |||
2892 | After you call png_read_update_info(), you can allocate any | ||
2893 | memory you need to hold the image. The row data is simply | ||
2894 | raw byte data for all forms of images. As the actual allocation | ||
2895 | varies among applications, no example will be given. If you | ||
2896 | are allocating one large chunk, you will need to build an | ||
2897 | array of pointers to each row, as it will be needed for some | ||
2898 | of the functions below. | ||
2899 | |||
2900 | Remember: Before you call png_read_update_info(), the png_get_*() | ||
2901 | functions return the values corresponding to the original PNG image. | ||
2902 | After you call png_read_update_info the values refer to the image | ||
2903 | that libpng will output. Consequently you must call all the png_set_ | ||
2904 | functions before you call png_read_update_info(). This is particularly | ||
2905 | important for png_set_interlace_handling() - if you are going to call | ||
2906 | png_read_update_info() you must call png_set_interlace_handling() before | ||
2907 | it unless you want to receive interlaced output. | ||
2908 | |||
2909 | .SS Reading image data | ||
2910 | |||
2911 | After you've allocated memory, you can read the image data. | ||
2912 | The simplest way to do this is in one function call. If you are | ||
2913 | allocating enough memory to hold the whole image, you can just | ||
2914 | call png_read_image() and libpng will read in all the image data | ||
2915 | and put it in the memory area supplied. You will need to pass in | ||
2916 | an array of pointers to each row. | ||
2917 | |||
2918 | This function automatically handles interlacing, so you don't | ||
2919 | need to call png_set_interlace_handling() (unless you call | ||
2920 | png_read_update_info()) or call this function multiple times, or any | ||
2921 | of that other stuff necessary with png_read_rows(). | ||
2922 | |||
2923 | png_read_image(png_ptr, row_pointers); | ||
2924 | |||
2925 | where row_pointers is: | ||
2926 | |||
2927 | png_bytep row_pointers[height]; | ||
2928 | |||
2929 | You can point to void or char or whatever you use for pixels. | ||
2930 | |||
2931 | If you don't want to read in the whole image at once, you can | ||
2932 | use png_read_rows() instead. If there is no interlacing (check | ||
2933 | interlace_type == PNG_INTERLACE_NONE), this is simple: | ||
2934 | |||
2935 | png_read_rows(png_ptr, row_pointers, NULL, | ||
2936 | number_of_rows); | ||
2937 | |||
2938 | where row_pointers is the same as in the png_read_image() call. | ||
2939 | |||
2940 | If you are doing this just one row at a time, you can do this with | ||
2941 | a single row_pointer instead of an array of row_pointers: | ||
2942 | |||
2943 | png_bytep row_pointer = row; | ||
2944 | png_read_row(png_ptr, row_pointer, NULL); | ||
2945 | |||
2946 | If the file is interlaced (interlace_type != 0 in the IHDR chunk), things | ||
2947 | get somewhat harder. The only current (PNG Specification version 1.2) | ||
2948 | interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7); | ||
2949 | a somewhat complicated 2D interlace scheme, known as Adam7, that | ||
2950 | breaks down an image into seven smaller images of varying size, based | ||
2951 | on an 8x8 grid. This number is defined (from libpng 1.5) as | ||
2952 | PNG_INTERLACE_ADAM7_PASSES in png.h | ||
2953 | |||
2954 | libpng can fill out those images or it can give them to you "as is". | ||
2955 | It is almost always better to have libpng handle the interlacing for you. | ||
2956 | If you want the images filled out, there are two ways to do that. The one | ||
2957 | mentioned in the PNG specification is to expand each pixel to cover | ||
2958 | those pixels that have not been read yet (the "rectangle" method). | ||
2959 | This results in a blocky image for the first pass, which gradually | ||
2960 | smooths out as more pixels are read. The other method is the "sparkle" | ||
2961 | method, where pixels are drawn only in their final locations, with the | ||
2962 | rest of the image remaining whatever colors they were initialized to | ||
2963 | before the start of the read. The first method usually looks better, | ||
2964 | but tends to be slower, as there are more pixels to put in the rows. | ||
2965 | |||
2966 | If, as is likely, you want libpng to expand the images, call this before | ||
2967 | calling png_start_read_image() or png_read_update_info(): | ||
2968 | |||
2969 | if (interlace_type == PNG_INTERLACE_ADAM7) | ||
2970 | number_of_passes | ||
2971 | = png_set_interlace_handling(png_ptr); | ||
2972 | |||
2973 | This will return the number of passes needed. Currently, this is seven, | ||
2974 | but may change if another interlace type is added. This function can be | ||
2975 | called even if the file is not interlaced, where it will return one pass. | ||
2976 | You then need to read the whole image 'number_of_passes' times. Each time | ||
2977 | will distribute the pixels from the current pass to the correct place in | ||
2978 | the output image, so you need to supply the same rows to png_read_rows in | ||
2979 | each pass. | ||
2980 | |||
2981 | If you are not going to display the image after each pass, but are | ||
2982 | going to wait until the entire image is read in, use the sparkle | ||
2983 | effect. This effect is faster and the end result of either method | ||
2984 | is exactly the same. If you are planning on displaying the image | ||
2985 | after each pass, the "rectangle" effect is generally considered the | ||
2986 | better looking one. | ||
2987 | |||
2988 | If you only want the "sparkle" effect, just call png_read_rows() as | ||
2989 | normal, with the third parameter NULL. Make sure you make pass over | ||
2990 | the image number_of_passes times, and you don't change the data in the | ||
2991 | rows between calls. You can change the locations of the data, just | ||
2992 | not the data. Each pass only writes the pixels appropriate for that | ||
2993 | pass, and assumes the data from previous passes is still valid. | ||
2994 | |||
2995 | png_read_rows(png_ptr, row_pointers, NULL, | ||
2996 | number_of_rows); | ||
2997 | |||
2998 | If you only want the first effect (the rectangles), do the same as | ||
2999 | before except pass the row buffer in the third parameter, and leave | ||
3000 | the second parameter NULL. | ||
3001 | |||
3002 | png_read_rows(png_ptr, NULL, row_pointers, | ||
3003 | number_of_rows); | ||
3004 | |||
3005 | If you don't want libpng to handle the interlacing details, just call | ||
3006 | png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images. | ||
3007 | Each of the images is a valid image by itself, however you will almost | ||
3008 | certainly need to distribute the pixels from each sub-image to the | ||
3009 | correct place. This is where everything gets very tricky. | ||
3010 | |||
3011 | If you want to retrieve the separate images you must pass the correct | ||
3012 | number of rows to each successive call of png_read_rows(). The calculation | ||
3013 | gets pretty complicated for small images, where some sub-images may | ||
3014 | not even exist because either their width or height ends up zero. | ||
3015 | libpng provides two macros to help you in 1.5 and later versions: | ||
3016 | |||
3017 | png_uint_32 width = PNG_PASS_COLS(image_width, pass_number); | ||
3018 | png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number); | ||
3019 | |||
3020 | Respectively these tell you the width and height of the sub-image | ||
3021 | corresponding to the numbered pass. 'pass' is in in the range 0 to 6 - | ||
3022 | this can be confusing because the specification refers to the same passes | ||
3023 | as 1 to 7! Be careful, you must check both the width and height before | ||
3024 | calling png_read_rows() and not call it for that pass if either is zero. | ||
3025 | |||
3026 | You can, of course, read each sub-image row by row. If you want to | ||
3027 | produce optimal code to make a pixel-by-pixel transformation of an | ||
3028 | interlaced image this is the best approach; read each row of each pass, | ||
3029 | transform it, and write it out to a new interlaced image. | ||
3030 | |||
3031 | If you want to de-interlace the image yourself libpng provides further | ||
3032 | macros to help that tell you where to place the pixels in the output image. | ||
3033 | Because the interlacing scheme is rectangular - sub-image pixels are always | ||
3034 | arranged on a rectangular grid - all you need to know for each pass is the | ||
3035 | starting column and row in the output image of the first pixel plus the | ||
3036 | spacing between each pixel. As of libpng 1.5 there are four macros to | ||
3037 | retrieve this information: | ||
3038 | |||
3039 | png_uint_32 x = PNG_PASS_START_COL(pass); | ||
3040 | png_uint_32 y = PNG_PASS_START_ROW(pass); | ||
3041 | png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass); | ||
3042 | png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass); | ||
3043 | |||
3044 | These allow you to write the obvious loop: | ||
3045 | |||
3046 | png_uint_32 input_y = 0; | ||
3047 | png_uint_32 output_y = PNG_PASS_START_ROW(pass); | ||
3048 | |||
3049 | while (output_y < output_image_height) | ||
3050 | { | ||
3051 | png_uint_32 input_x = 0; | ||
3052 | png_uint_32 output_x = PNG_PASS_START_COL(pass); | ||
3053 | |||
3054 | while (output_x < output_image_width) | ||
3055 | { | ||
3056 | image[output_y][output_x] = | ||
3057 | subimage[pass][input_y][input_x++]; | ||
3058 | |||
3059 | output_x += xStep; | ||
3060 | } | ||
3061 | |||
3062 | ++input_y; | ||
3063 | output_y += yStep; | ||
3064 | } | ||
3065 | |||
3066 | Notice that the steps between successive output rows and columns are | ||
3067 | returned as shifts. This is possible because the pixels in the subimages | ||
3068 | are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original | ||
3069 | image. In practice you may need to directly calculate the output coordinate | ||
3070 | given an input coordinate. libpng provides two further macros for this | ||
3071 | purpose: | ||
3072 | |||
3073 | png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass); | ||
3074 | png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass); | ||
3075 | |||
3076 | Finally a pair of macros are provided to tell you if a particular image | ||
3077 | row or column appears in a given pass: | ||
3078 | |||
3079 | int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass); | ||
3080 | int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass); | ||
3081 | |||
3082 | Bear in mind that you will probably also need to check the width and height | ||
3083 | of the pass in addition to the above to be sure the pass even exists! | ||
3084 | |||
3085 | With any luck you are convinced by now that you don't want to do your own | ||
3086 | interlace handling. In reality normally the only good reason for doing this | ||
3087 | is if you are processing PNG files on a pixel-by-pixel basis and don't want | ||
3088 | to load the whole file into memory when it is interlaced. | ||
3089 | |||
3090 | libpng includes a test program, pngvalid, that illustrates reading and | ||
3091 | writing of interlaced images. If you can't get interlacing to work in your | ||
3092 | code and don't want to leave it to libpng (the recommended approach), see | ||
3093 | how pngvalid.c does it. | ||
3094 | |||
3095 | .SS Finishing a sequential read | ||
3096 | |||
3097 | After you are finished reading the image through the | ||
3098 | low-level interface, you can finish reading the file. If you are | ||
3099 | interested in comments or time, which may be stored either before or | ||
3100 | after the image data, you should pass the separate png_info struct if | ||
3101 | you want to keep the comments from before and after the image | ||
3102 | separate. | ||
3103 | |||
3104 | png_infop end_info = png_create_info_struct(png_ptr); | ||
3105 | |||
3106 | if (!end_info) | ||
3107 | { | ||
3108 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
3109 | (png_infopp)NULL); | ||
3110 | return (ERROR); | ||
3111 | } | ||
3112 | |||
3113 | png_read_end(png_ptr, end_info); | ||
3114 | |||
3115 | If you are not interested, you should still call png_read_end() | ||
3116 | but you can pass NULL, avoiding the need to create an end_info structure. | ||
3117 | |||
3118 | png_read_end(png_ptr, (png_infop)NULL); | ||
3119 | |||
3120 | If you don't call png_read_end(), then your file pointer will be | ||
3121 | left pointing to the first chunk after the last IDAT, which is probably | ||
3122 | not what you want if you expect to read something beyond the end of | ||
3123 | the PNG datastream. | ||
3124 | |||
3125 | When you are done, you can free all memory allocated by libpng like this: | ||
3126 | |||
3127 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
3128 | &end_info); | ||
3129 | |||
3130 | or, if you didn't create an end_info structure, | ||
3131 | |||
3132 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
3133 | (png_infopp)NULL); | ||
3134 | |||
3135 | It is also possible to individually free the info_ptr members that | ||
3136 | point to libpng-allocated storage with the following function: | ||
3137 | |||
3138 | png_free_data(png_ptr, info_ptr, mask, seq) | ||
3139 | |||
3140 | mask - identifies data to be freed, a mask | ||
3141 | containing the bitwise OR of one or | ||
3142 | more of | ||
3143 | PNG_FREE_PLTE, PNG_FREE_TRNS, | ||
3144 | PNG_FREE_HIST, PNG_FREE_ICCP, | ||
3145 | PNG_FREE_PCAL, PNG_FREE_ROWS, | ||
3146 | PNG_FREE_SCAL, PNG_FREE_SPLT, | ||
3147 | PNG_FREE_TEXT, PNG_FREE_UNKN, | ||
3148 | or simply PNG_FREE_ALL | ||
3149 | |||
3150 | seq - sequence number of item to be freed | ||
3151 | (-1 for all items) | ||
3152 | |||
3153 | This function may be safely called when the relevant storage has | ||
3154 | already been freed, or has not yet been allocated, or was allocated | ||
3155 | by the user and not by libpng, and will in those cases do nothing. | ||
3156 | The "seq" parameter is ignored if only one item of the selected data | ||
3157 | type, such as PLTE, is allowed. If "seq" is not -1, and multiple items | ||
3158 | are allowed for the data type identified in the mask, such as text or | ||
3159 | sPLT, only the n'th item in the structure is freed, where n is "seq". | ||
3160 | |||
3161 | The default behavior is only to free data that was allocated internally | ||
3162 | by libpng. This can be changed, so that libpng will not free the data, | ||
3163 | or so that it will free data that was allocated by the user with png_malloc() | ||
3164 | or png_zalloc() and passed in via a png_set_*() function, with | ||
3165 | |||
3166 | png_data_freer(png_ptr, info_ptr, freer, mask) | ||
3167 | |||
3168 | freer - one of | ||
3169 | PNG_DESTROY_WILL_FREE_DATA | ||
3170 | PNG_SET_WILL_FREE_DATA | ||
3171 | PNG_USER_WILL_FREE_DATA | ||
3172 | |||
3173 | mask - which data elements are affected | ||
3174 | same choices as in png_free_data() | ||
3175 | |||
3176 | This function only affects data that has already been allocated. | ||
3177 | You can call this function after reading the PNG data but before calling | ||
3178 | any png_set_*() functions, to control whether the user or the png_set_*() | ||
3179 | function is responsible for freeing any existing data that might be present, | ||
3180 | and again after the png_set_*() functions to control whether the user | ||
3181 | or png_destroy_*() is supposed to free the data. When the user assumes | ||
3182 | responsibility for libpng-allocated data, the application must use | ||
3183 | png_free() to free it, and when the user transfers responsibility to libpng | ||
3184 | for data that the user has allocated, the user must have used png_malloc() | ||
3185 | or png_zalloc() to allocate it. | ||
3186 | |||
3187 | If you allocated your row_pointers in a single block, as suggested above in | ||
3188 | the description of the high level read interface, you must not transfer | ||
3189 | responsibility for freeing it to the png_set_rows or png_read_destroy function, | ||
3190 | because they would also try to free the individual row_pointers[i]. | ||
3191 | |||
3192 | If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword | ||
3193 | separately, do not transfer responsibility for freeing text_ptr to libpng, | ||
3194 | because when libpng fills a png_text structure it combines these members with | ||
3195 | the key member, and png_free_data() will free only text_ptr.key. Similarly, | ||
3196 | if you transfer responsibility for free'ing text_ptr from libpng to your | ||
3197 | application, your application must not separately free those members. | ||
3198 | |||
3199 | The png_free_data() function will turn off the "valid" flag for anything | ||
3200 | it frees. If you need to turn the flag off for a chunk that was freed by | ||
3201 | your application instead of by libpng, you can use | ||
3202 | |||
3203 | png_set_invalid(png_ptr, info_ptr, mask); | ||
3204 | |||
3205 | mask - identifies the chunks to be made invalid, | ||
3206 | containing the bitwise OR of one or | ||
3207 | more of | ||
3208 | PNG_INFO_gAMA, PNG_INFO_sBIT, | ||
3209 | PNG_INFO_cHRM, PNG_INFO_PLTE, | ||
3210 | PNG_INFO_tRNS, PNG_INFO_bKGD, | ||
3211 | PNG_INFO_hIST, PNG_INFO_pHYs, | ||
3212 | PNG_INFO_oFFs, PNG_INFO_tIME, | ||
3213 | PNG_INFO_pCAL, PNG_INFO_sRGB, | ||
3214 | PNG_INFO_iCCP, PNG_INFO_sPLT, | ||
3215 | PNG_INFO_sCAL, PNG_INFO_IDAT | ||
3216 | |||
3217 | For a more compact example of reading a PNG image, see the file example.c. | ||
3218 | |||
3219 | .SS Reading PNG files progressively | ||
3220 | |||
3221 | The progressive reader is slightly different then the non-progressive | ||
3222 | reader. Instead of calling png_read_info(), png_read_rows(), and | ||
3223 | png_read_end(), you make one call to png_process_data(), which calls | ||
3224 | callbacks when it has the info, a row, or the end of the image. You | ||
3225 | set up these callbacks with png_set_progressive_read_fn(). You don't | ||
3226 | have to worry about the input/output functions of libpng, as you are | ||
3227 | giving the library the data directly in png_process_data(). I will | ||
3228 | assume that you have read the section on reading PNG files above, | ||
3229 | so I will only highlight the differences (although I will show | ||
3230 | all of the code). | ||
3231 | |||
3232 | png_structp png_ptr; | ||
3233 | png_infop info_ptr; | ||
3234 | |||
3235 | /* An example code fragment of how you would | ||
3236 | initialize the progressive reader in your | ||
3237 | application. */ | ||
3238 | int | ||
3239 | initialize_png_reader() | ||
3240 | { | ||
3241 | png_ptr = png_create_read_struct | ||
3242 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, | ||
3243 | user_error_fn, user_warning_fn); | ||
3244 | |||
3245 | if (!png_ptr) | ||
3246 | return (ERROR); | ||
3247 | |||
3248 | info_ptr = png_create_info_struct(png_ptr); | ||
3249 | |||
3250 | if (!info_ptr) | ||
3251 | { | ||
3252 | png_destroy_read_struct(&png_ptr, | ||
3253 | (png_infopp)NULL, (png_infopp)NULL); | ||
3254 | return (ERROR); | ||
3255 | } | ||
3256 | |||
3257 | if (setjmp(png_jmpbuf(png_ptr))) | ||
3258 | { | ||
3259 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
3260 | (png_infopp)NULL); | ||
3261 | return (ERROR); | ||
3262 | } | ||
3263 | |||
3264 | /* This one's new. You can provide functions | ||
3265 | to be called when the header info is valid, | ||
3266 | when each row is completed, and when the image | ||
3267 | is finished. If you aren't using all functions, | ||
3268 | you can specify NULL parameters. Even when all | ||
3269 | three functions are NULL, you need to call | ||
3270 | png_set_progressive_read_fn(). You can use | ||
3271 | any struct as the user_ptr (cast to a void pointer | ||
3272 | for the function call), and retrieve the pointer | ||
3273 | from inside the callbacks using the function | ||
3274 | |||
3275 | png_get_progressive_ptr(png_ptr); | ||
3276 | |||
3277 | which will return a void pointer, which you have | ||
3278 | to cast appropriately. | ||
3279 | */ | ||
3280 | png_set_progressive_read_fn(png_ptr, (void *)user_ptr, | ||
3281 | info_callback, row_callback, end_callback); | ||
3282 | |||
3283 | return 0; | ||
3284 | } | ||
3285 | |||
3286 | /* A code fragment that you call as you receive blocks | ||
3287 | of data */ | ||
3288 | int | ||
3289 | process_data(png_bytep buffer, png_uint_32 length) | ||
3290 | { | ||
3291 | if (setjmp(png_jmpbuf(png_ptr))) | ||
3292 | { | ||
3293 | png_destroy_read_struct(&png_ptr, &info_ptr, | ||
3294 | (png_infopp)NULL); | ||
3295 | return (ERROR); | ||
3296 | } | ||
3297 | |||
3298 | /* This one's new also. Simply give it a chunk | ||
3299 | of data from the file stream (in order, of | ||
3300 | course). On machines with segmented memory | ||
3301 | models machines, don't give it any more than | ||
3302 | 64K. The library seems to run fine with sizes | ||
3303 | of 4K. Although you can give it much less if | ||
3304 | necessary (I assume you can give it chunks of | ||
3305 | 1 byte, I haven't tried less then 256 bytes | ||
3306 | yet). When this function returns, you may | ||
3307 | want to display any rows that were generated | ||
3308 | in the row callback if you don't already do | ||
3309 | so there. | ||
3310 | */ | ||
3311 | png_process_data(png_ptr, info_ptr, buffer, length); | ||
3312 | |||
3313 | /* At this point you can call png_process_data_skip if | ||
3314 | you want to handle data the library will skip yourself; | ||
3315 | it simply returns the number of bytes to skip (and stops | ||
3316 | libpng skipping that number of bytes on the next | ||
3317 | png_process_data call). | ||
3318 | return 0; | ||
3319 | } | ||
3320 | |||
3321 | /* This function is called (as set by | ||
3322 | png_set_progressive_read_fn() above) when enough data | ||
3323 | has been supplied so all of the header has been | ||
3324 | read. | ||
3325 | */ | ||
3326 | void | ||
3327 | info_callback(png_structp png_ptr, png_infop info) | ||
3328 | { | ||
3329 | /* Do any setup here, including setting any of | ||
3330 | the transformations mentioned in the Reading | ||
3331 | PNG files section. For now, you _must_ call | ||
3332 | either png_start_read_image() or | ||
3333 | png_read_update_info() after all the | ||
3334 | transformations are set (even if you don't set | ||
3335 | any). You may start getting rows before | ||
3336 | png_process_data() returns, so this is your | ||
3337 | last chance to prepare for that. | ||
3338 | |||
3339 | This is where you turn on interlace handling, | ||
3340 | assuming you don't want to do it yourself. | ||
3341 | |||
3342 | If you need to you can stop the processing of | ||
3343 | your original input data at this point by calling | ||
3344 | png_process_data_pause. This returns the number | ||
3345 | of unprocessed bytes from the last png_process_data | ||
3346 | call - it is up to you to ensure that the next call | ||
3347 | sees these bytes again. If you don't want to bother | ||
3348 | with this you can get libpng to cache the unread | ||
3349 | bytes by setting the 'save' parameter (see png.h) but | ||
3350 | then libpng will have to copy the data internally. | ||
3351 | */ | ||
3352 | } | ||
3353 | |||
3354 | /* This function is called when each row of image | ||
3355 | data is complete */ | ||
3356 | void | ||
3357 | row_callback(png_structp png_ptr, png_bytep new_row, | ||
3358 | png_uint_32 row_num, int pass) | ||
3359 | { | ||
3360 | /* If the image is interlaced, and you turned | ||
3361 | on the interlace handler, this function will | ||
3362 | be called for every row in every pass. Some | ||
3363 | of these rows will not be changed from the | ||
3364 | previous pass. When the row is not changed, | ||
3365 | the new_row variable will be NULL. The rows | ||
3366 | and passes are called in order, so you don't | ||
3367 | really need the row_num and pass, but I'm | ||
3368 | supplying them because it may make your life | ||
3369 | easier. | ||
3370 | |||
3371 | If you did not turn on interlace handling then | ||
3372 | the callback is called for each row of each | ||
3373 | sub-image when the image is interlaced. In this | ||
3374 | case 'row_num' is the row in the sub-image, not | ||
3375 | the row in the output image as it is in all other | ||
3376 | cases. | ||
3377 | |||
3378 | For the non-NULL rows of interlaced images when | ||
3379 | you have switched on libpng interlace handling, | ||
3380 | you must call png_progressive_combine_row() | ||
3381 | passing in the row and the old row. You can | ||
3382 | call this function for NULL rows (it will just | ||
3383 | return) and for non-interlaced images (it just | ||
3384 | does the memcpy for you) if it will make the | ||
3385 | code easier. Thus, you can just do this for | ||
3386 | all cases if you switch on interlace handling; | ||
3387 | */ | ||
3388 | |||
3389 | png_progressive_combine_row(png_ptr, old_row, | ||
3390 | new_row); | ||
3391 | |||
3392 | /* where old_row is what was displayed for | ||
3393 | previously for the row. Note that the first | ||
3394 | pass (pass == 0, really) will completely cover | ||
3395 | the old row, so the rows do not have to be | ||
3396 | initialized. After the first pass (and only | ||
3397 | for interlaced images), you will have to pass | ||
3398 | the current row, and the function will combine | ||
3399 | the old row and the new row. | ||
3400 | |||
3401 | You can also call png_process_data_pause in this | ||
3402 | callback - see above. | ||
3403 | */ | ||
3404 | } | ||
3405 | |||
3406 | void | ||
3407 | end_callback(png_structp png_ptr, png_infop info) | ||
3408 | { | ||
3409 | /* This function is called after the whole image | ||
3410 | has been read, including any chunks after the | ||
3411 | image (up to and including the IEND). You | ||
3412 | will usually have the same info chunk as you | ||
3413 | had in the header, although some data may have | ||
3414 | been added to the comments and time fields. | ||
3415 | |||
3416 | Most people won't do much here, perhaps setting | ||
3417 | a flag that marks the image as finished. | ||
3418 | */ | ||
3419 | } | ||
3420 | |||
3421 | |||
3422 | |||
3423 | .SH IV. Writing | ||
3424 | |||
3425 | Much of this is very similar to reading. However, everything of | ||
3426 | importance is repeated here, so you won't have to constantly look | ||
3427 | back up in the reading section to understand writing. | ||
3428 | |||
3429 | .SS Setup | ||
3430 | |||
3431 | You will want to do the I/O initialization before you get into libpng, | ||
3432 | so if it doesn't work, you don't have anything to undo. If you are not | ||
3433 | using the standard I/O functions, you will need to replace them with | ||
3434 | custom writing functions. See the discussion under Customizing libpng. | ||
3435 | |||
3436 | FILE *fp = fopen(file_name, "wb"); | ||
3437 | |||
3438 | if (!fp) | ||
3439 | return (ERROR); | ||
3440 | |||
3441 | Next, png_struct and png_info need to be allocated and initialized. | ||
3442 | As these can be both relatively large, you may not want to store these | ||
3443 | on the stack, unless you have stack space to spare. Of course, you | ||
3444 | will want to check if they return NULL. If you are also reading, | ||
3445 | you won't want to name your read structure and your write structure | ||
3446 | both "png_ptr"; you can call them anything you like, such as | ||
3447 | "read_ptr" and "write_ptr". Look at pngtest.c, for example. | ||
3448 | |||
3449 | png_structp png_ptr = png_create_write_struct | ||
3450 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, | ||
3451 | user_error_fn, user_warning_fn); | ||
3452 | |||
3453 | if (!png_ptr) | ||
3454 | return (ERROR); | ||
3455 | |||
3456 | png_infop info_ptr = png_create_info_struct(png_ptr); | ||
3457 | if (!info_ptr) | ||
3458 | { | ||
3459 | png_destroy_write_struct(&png_ptr, | ||
3460 | (png_infopp)NULL); | ||
3461 | return (ERROR); | ||
3462 | } | ||
3463 | |||
3464 | If you want to use your own memory allocation routines, | ||
3465 | define PNG_USER_MEM_SUPPORTED and use | ||
3466 | png_create_write_struct_2() instead of png_create_write_struct(): | ||
3467 | |||
3468 | png_structp png_ptr = png_create_write_struct_2 | ||
3469 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, | ||
3470 | user_error_fn, user_warning_fn, (png_voidp) | ||
3471 | user_mem_ptr, user_malloc_fn, user_free_fn); | ||
3472 | |||
3473 | After you have these structures, you will need to set up the | ||
3474 | error handling. When libpng encounters an error, it expects to | ||
3475 | longjmp() back to your routine. Therefore, you will need to call | ||
3476 | setjmp() and pass the png_jmpbuf(png_ptr). If you | ||
3477 | write the file from different routines, you will need to update | ||
3478 | the png_jmpbuf(png_ptr) every time you enter a new routine that will | ||
3479 | call a png_*() function. See your documentation of setjmp/longjmp | ||
3480 | for your compiler for more information on setjmp/longjmp. See | ||
3481 | the discussion on libpng error handling in the Customizing Libpng | ||
3482 | section below for more information on the libpng error handling. | ||
3483 | |||
3484 | if (setjmp(png_jmpbuf(png_ptr))) | ||
3485 | { | ||
3486 | png_destroy_write_struct(&png_ptr, &info_ptr); | ||
3487 | fclose(fp); | ||
3488 | return (ERROR); | ||
3489 | } | ||
3490 | ... | ||
3491 | return; | ||
3492 | |||
3493 | If you would rather avoid the complexity of setjmp/longjmp issues, | ||
3494 | you can compile libpng with PNG_NO_SETJMP, in which case | ||
3495 | errors will result in a call to PNG_ABORT() which defaults to abort(). | ||
3496 | |||
3497 | You can #define PNG_ABORT() to a function that does something | ||
3498 | more useful than abort(), as long as your function does not | ||
3499 | return. | ||
3500 | |||
3501 | Now you need to set up the output code. The default for libpng is to | ||
3502 | use the C function fwrite(). If you use this, you will need to pass a | ||
3503 | valid FILE * in the function png_init_io(). Be sure that the file is | ||
3504 | opened in binary mode. Again, if you wish to handle writing data in | ||
3505 | another way, see the discussion on libpng I/O handling in the Customizing | ||
3506 | Libpng section below. | ||
3507 | |||
3508 | png_init_io(png_ptr, fp); | ||
3509 | |||
3510 | If you are embedding your PNG into a datastream such as MNG, and don't | ||
3511 | want libpng to write the 8-byte signature, or if you have already | ||
3512 | written the signature in your application, use | ||
3513 | |||
3514 | png_set_sig_bytes(png_ptr, 8); | ||
3515 | |||
3516 | to inform libpng that it should not write a signature. | ||
3517 | |||
3518 | .SS Write callbacks | ||
3519 | |||
3520 | At this point, you can set up a callback function that will be | ||
3521 | called after each row has been written, which you can use to control | ||
3522 | a progress meter or the like. It's demonstrated in pngtest.c. | ||
3523 | You must supply a function | ||
3524 | |||
3525 | void write_row_callback(png_structp png_ptr, png_uint_32 row, | ||
3526 | int pass); | ||
3527 | { | ||
3528 | /* put your code here */ | ||
3529 | } | ||
3530 | |||
3531 | (You can give it another name that you like instead of "write_row_callback") | ||
3532 | |||
3533 | To inform libpng about your function, use | ||
3534 | |||
3535 | png_set_write_status_fn(png_ptr, write_row_callback); | ||
3536 | |||
3537 | When this function is called the row has already been completely processed and | ||
3538 | it has also been written out. The 'row' and 'pass' refer to the next row to be | ||
3539 | handled. For the | ||
3540 | non-interlaced case the row that was just handled is simply one less than the | ||
3541 | passed in row number, and pass will always be 0. For the interlaced case the | ||
3542 | same applies unless the row value is 0, in which case the row just handled was | ||
3543 | the last one from one of the preceding passes. Because interlacing may skip a | ||
3544 | pass you cannot be sure that the preceding pass is just 'pass-1', if you really | ||
3545 | need to know what the last pass is record (row,pass) from the callback and use | ||
3546 | the last recorded value each time. | ||
3547 | |||
3548 | As with the user transform you can find the output row using the | ||
3549 | PNG_ROW_FROM_PASS_ROW macro. | ||
3550 | |||
3551 | You now have the option of modifying how the compression library will | ||
3552 | run. The following functions are mainly for testing, but may be useful | ||
3553 | in some cases, like if you need to write PNG files extremely fast and | ||
3554 | are willing to give up some compression, or if you want to get the | ||
3555 | maximum possible compression at the expense of slower writing. If you | ||
3556 | have no special needs in this area, let the library do what it wants by | ||
3557 | not calling this function at all, as it has been tuned to deliver a good | ||
3558 | speed/compression ratio. The second parameter to png_set_filter() is | ||
3559 | the filter method, for which the only valid values are 0 (as of the | ||
3560 | July 1999 PNG specification, version 1.2) or 64 (if you are writing | ||
3561 | a PNG datastream that is to be embedded in a MNG datastream). The third | ||
3562 | parameter is a flag that indicates which filter type(s) are to be tested | ||
3563 | for each scanline. See the PNG specification for details on the specific | ||
3564 | filter types. | ||
3565 | |||
3566 | |||
3567 | /* turn on or off filtering, and/or choose | ||
3568 | specific filters. You can use either a single | ||
3569 | PNG_FILTER_VALUE_NAME or the bitwise OR of one | ||
3570 | or more PNG_FILTER_NAME masks. | ||
3571 | */ | ||
3572 | png_set_filter(png_ptr, 0, | ||
3573 | PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | | ||
3574 | PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | | ||
3575 | PNG_FILTER_UP | PNG_FILTER_VALUE_UP | | ||
3576 | PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG | | ||
3577 | PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| | ||
3578 | PNG_ALL_FILTERS); | ||
3579 | |||
3580 | If an application wants to start and stop using particular filters during | ||
3581 | compression, it should start out with all of the filters (to ensure that | ||
3582 | the previous row of pixels will be stored in case it's needed later), | ||
3583 | and then add and remove them after the start of compression. | ||
3584 | |||
3585 | If you are writing a PNG datastream that is to be embedded in a MNG | ||
3586 | datastream, the second parameter can be either 0 or 64. | ||
3587 | |||
3588 | The png_set_compression_*() functions interface to the zlib compression | ||
3589 | library, and should mostly be ignored unless you really know what you are | ||
3590 | doing. The only generally useful call is png_set_compression_level() | ||
3591 | which changes how much time zlib spends on trying to compress the image | ||
3592 | data. See the Compression Library (zlib.h and algorithm.txt, distributed | ||
3593 | with zlib) for details on the compression levels. | ||
3594 | |||
3595 | #include zlib.h | ||
3596 | |||
3597 | /* Set the zlib compression level */ | ||
3598 | png_set_compression_level(png_ptr, | ||
3599 | Z_BEST_COMPRESSION); | ||
3600 | |||
3601 | /* Set other zlib parameters for compressing IDAT */ | ||
3602 | png_set_compression_mem_level(png_ptr, 8); | ||
3603 | png_set_compression_strategy(png_ptr, | ||
3604 | Z_DEFAULT_STRATEGY); | ||
3605 | png_set_compression_window_bits(png_ptr, 15); | ||
3606 | png_set_compression_method(png_ptr, 8); | ||
3607 | png_set_compression_buffer_size(png_ptr, 8192) | ||
3608 | |||
3609 | /* Set zlib parameters for text compression | ||
3610 | * If you don't call these, the parameters | ||
3611 | * fall back on those defined for IDAT chunks | ||
3612 | */ | ||
3613 | png_set_text_compression_mem_level(png_ptr, 8); | ||
3614 | png_set_text_compression_strategy(png_ptr, | ||
3615 | Z_DEFAULT_STRATEGY); | ||
3616 | png_set_text_compression_window_bits(png_ptr, 15); | ||
3617 | png_set_text_compression_method(png_ptr, 8); | ||
3618 | |||
3619 | .SS Setting the contents of info for output | ||
3620 | |||
3621 | You now need to fill in the png_info structure with all the data you | ||
3622 | wish to write before the actual image. Note that the only thing you | ||
3623 | are allowed to write after the image is the text chunks and the time | ||
3624 | chunk (as of PNG Specification 1.2, anyway). See png_write_end() and | ||
3625 | the latest PNG specification for more information on that. If you | ||
3626 | wish to write them before the image, fill them in now, and flag that | ||
3627 | data as being valid. If you want to wait until after the data, don't | ||
3628 | fill them until png_write_end(). For all the fields in png_info and | ||
3629 | their data types, see png.h. For explanations of what the fields | ||
3630 | contain, see the PNG specification. | ||
3631 | |||
3632 | Some of the more important parts of the png_info are: | ||
3633 | |||
3634 | png_set_IHDR(png_ptr, info_ptr, width, height, | ||
3635 | bit_depth, color_type, interlace_type, | ||
3636 | compression_type, filter_method) | ||
3637 | |||
3638 | width - holds the width of the image | ||
3639 | in pixels (up to 2^31). | ||
3640 | |||
3641 | height - holds the height of the image | ||
3642 | in pixels (up to 2^31). | ||
3643 | |||
3644 | bit_depth - holds the bit depth of one of the | ||
3645 | image channels. | ||
3646 | (valid values are 1, 2, 4, 8, 16 | ||
3647 | and depend also on the | ||
3648 | color_type. See also significant | ||
3649 | bits (sBIT) below). | ||
3650 | |||
3651 | color_type - describes which color/alpha | ||
3652 | channels are present. | ||
3653 | PNG_COLOR_TYPE_GRAY | ||
3654 | (bit depths 1, 2, 4, 8, 16) | ||
3655 | PNG_COLOR_TYPE_GRAY_ALPHA | ||
3656 | (bit depths 8, 16) | ||
3657 | PNG_COLOR_TYPE_PALETTE | ||
3658 | (bit depths 1, 2, 4, 8) | ||
3659 | PNG_COLOR_TYPE_RGB | ||
3660 | (bit_depths 8, 16) | ||
3661 | PNG_COLOR_TYPE_RGB_ALPHA | ||
3662 | (bit_depths 8, 16) | ||
3663 | |||
3664 | PNG_COLOR_MASK_PALETTE | ||
3665 | PNG_COLOR_MASK_COLOR | ||
3666 | PNG_COLOR_MASK_ALPHA | ||
3667 | |||
3668 | interlace_type - PNG_INTERLACE_NONE or | ||
3669 | PNG_INTERLACE_ADAM7 | ||
3670 | |||
3671 | compression_type - (must be | ||
3672 | PNG_COMPRESSION_TYPE_DEFAULT) | ||
3673 | |||
3674 | filter_method - (must be PNG_FILTER_TYPE_DEFAULT | ||
3675 | or, if you are writing a PNG to | ||
3676 | be embedded in a MNG datastream, | ||
3677 | can also be | ||
3678 | PNG_INTRAPIXEL_DIFFERENCING) | ||
3679 | |||
3680 | If you call png_set_IHDR(), the call must appear before any of the | ||
3681 | other png_set_*() functions, because they might require access to some of | ||
3682 | the IHDR settings. The remaining png_set_*() functions can be called | ||
3683 | in any order. | ||
3684 | |||
3685 | If you wish, you can reset the compression_type, interlace_type, or | ||
3686 | filter_method later by calling png_set_IHDR() again; if you do this, the | ||
3687 | width, height, bit_depth, and color_type must be the same in each call. | ||
3688 | |||
3689 | png_set_PLTE(png_ptr, info_ptr, palette, | ||
3690 | num_palette); | ||
3691 | |||
3692 | palette - the palette for the file | ||
3693 | (array of png_color) | ||
3694 | num_palette - number of entries in the palette | ||
3695 | |||
3696 | png_set_gAMA(png_ptr, info_ptr, file_gamma); | ||
3697 | png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma); | ||
3698 | |||
3699 | file_gamma - the gamma at which the image was | ||
3700 | created (PNG_INFO_gAMA) | ||
3701 | |||
3702 | int_file_gamma - 100,000 times the gamma at which | ||
3703 | the image was created | ||
3704 | |||
3705 | png_set_cHRM(png_ptr, info_ptr, white_x, white_y, red_x, red_y, | ||
3706 | green_x, green_y, blue_x, blue_y) | ||
3707 | png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X, | ||
3708 | green_Y, green_Z, blue_X, blue_Y, blue_Z) | ||
3709 | png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y, | ||
3710 | int_red_x, int_red_y, int_green_x, int_green_y, | ||
3711 | int_blue_x, int_blue_y) | ||
3712 | png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y, | ||
3713 | int_red_Z, int_green_X, int_green_Y, int_green_Z, | ||
3714 | int_blue_X, int_blue_Y, int_blue_Z) | ||
3715 | |||
3716 | {white,red,green,blue}_{x,y} | ||
3717 | A color space encoding specified using the chromaticities | ||
3718 | of the end points and the white point. | ||
3719 | |||
3720 | {red,green,blue}_{X,Y,Z} | ||
3721 | A color space encoding specified using the encoding end | ||
3722 | points - the CIE tristimulus specification of the intended | ||
3723 | color of the red, green and blue channels in the PNG RGB | ||
3724 | data. The white point is simply the sum of the three end | ||
3725 | points. | ||
3726 | |||
3727 | png_set_sRGB(png_ptr, info_ptr, srgb_intent); | ||
3728 | |||
3729 | srgb_intent - the rendering intent | ||
3730 | (PNG_INFO_sRGB) The presence of | ||
3731 | the sRGB chunk means that the pixel | ||
3732 | data is in the sRGB color space. | ||
3733 | This chunk also implies specific | ||
3734 | values of gAMA and cHRM. Rendering | ||
3735 | intent is the CSS-1 property that | ||
3736 | has been defined by the International | ||
3737 | Color Consortium | ||
3738 | (http://www.color.org). | ||
3739 | It can be one of | ||
3740 | PNG_sRGB_INTENT_SATURATION, | ||
3741 | PNG_sRGB_INTENT_PERCEPTUAL, | ||
3742 | PNG_sRGB_INTENT_ABSOLUTE, or | ||
3743 | PNG_sRGB_INTENT_RELATIVE. | ||
3744 | |||
3745 | |||
3746 | png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, | ||
3747 | srgb_intent); | ||
3748 | |||
3749 | srgb_intent - the rendering intent | ||
3750 | (PNG_INFO_sRGB) The presence of the | ||
3751 | sRGB chunk means that the pixel | ||
3752 | data is in the sRGB color space. | ||
3753 | This function also causes gAMA and | ||
3754 | cHRM chunks with the specific values | ||
3755 | that are consistent with sRGB to be | ||
3756 | written. | ||
3757 | |||
3758 | png_set_iCCP(png_ptr, info_ptr, name, compression_type, | ||
3759 | profile, proflen); | ||
3760 | |||
3761 | name - The profile name. | ||
3762 | |||
3763 | compression_type - The compression type; always | ||
3764 | PNG_COMPRESSION_TYPE_BASE for PNG 1.0. | ||
3765 | You may give NULL to this argument to | ||
3766 | ignore it. | ||
3767 | |||
3768 | profile - International Color Consortium color | ||
3769 | profile data. May contain NULs. | ||
3770 | |||
3771 | proflen - length of profile data in bytes. | ||
3772 | |||
3773 | png_set_sBIT(png_ptr, info_ptr, sig_bit); | ||
3774 | |||
3775 | sig_bit - the number of significant bits for | ||
3776 | (PNG_INFO_sBIT) each of the gray, red, | ||
3777 | green, and blue channels, whichever are | ||
3778 | appropriate for the given color type | ||
3779 | (png_color_16) | ||
3780 | |||
3781 | png_set_tRNS(png_ptr, info_ptr, trans_alpha, | ||
3782 | num_trans, trans_color); | ||
3783 | |||
3784 | trans_alpha - array of alpha (transparency) | ||
3785 | entries for palette (PNG_INFO_tRNS) | ||
3786 | |||
3787 | num_trans - number of transparent entries | ||
3788 | (PNG_INFO_tRNS) | ||
3789 | |||
3790 | trans_color - graylevel or color sample values | ||
3791 | (in order red, green, blue) of the | ||
3792 | single transparent color for | ||
3793 | non-paletted images (PNG_INFO_tRNS) | ||
3794 | |||
3795 | png_set_hIST(png_ptr, info_ptr, hist); | ||
3796 | |||
3797 | hist - histogram of palette (array of | ||
3798 | png_uint_16) (PNG_INFO_hIST) | ||
3799 | |||
3800 | png_set_tIME(png_ptr, info_ptr, mod_time); | ||
3801 | |||
3802 | mod_time - time image was last modified | ||
3803 | (PNG_VALID_tIME) | ||
3804 | |||
3805 | png_set_bKGD(png_ptr, info_ptr, background); | ||
3806 | |||
3807 | background - background color (of type | ||
3808 | png_color_16p) (PNG_VALID_bKGD) | ||
3809 | |||
3810 | png_set_text(png_ptr, info_ptr, text_ptr, num_text); | ||
3811 | |||
3812 | text_ptr - array of png_text holding image | ||
3813 | comments | ||
3814 | |||
3815 | text_ptr[i].compression - type of compression used | ||
3816 | on "text" PNG_TEXT_COMPRESSION_NONE | ||
3817 | PNG_TEXT_COMPRESSION_zTXt | ||
3818 | PNG_ITXT_COMPRESSION_NONE | ||
3819 | PNG_ITXT_COMPRESSION_zTXt | ||
3820 | text_ptr[i].key - keyword for comment. Must contain | ||
3821 | 1-79 characters. | ||
3822 | text_ptr[i].text - text comments for current | ||
3823 | keyword. Can be NULL or empty. | ||
3824 | text_ptr[i].text_length - length of text string, | ||
3825 | after decompression, 0 for iTXt | ||
3826 | text_ptr[i].itxt_length - length of itxt string, | ||
3827 | after decompression, 0 for tEXt/zTXt | ||
3828 | text_ptr[i].lang - language of comment (NULL or | ||
3829 | empty for unknown). | ||
3830 | text_ptr[i].translated_keyword - keyword in UTF-8 (NULL | ||
3831 | or empty for unknown). | ||
3832 | |||
3833 | Note that the itxt_length, lang, and lang_key | ||
3834 | members of the text_ptr structure only exist when the | ||
3835 | library is built with iTXt chunk support. Prior to | ||
3836 | libpng-1.4.0 the library was built by default without | ||
3837 | iTXt support. Also note that when iTXt is supported, | ||
3838 | they contain NULL pointers when the "compression" | ||
3839 | field contains PNG_TEXT_COMPRESSION_NONE or | ||
3840 | PNG_TEXT_COMPRESSION_zTXt. | ||
3841 | |||
3842 | num_text - number of comments | ||
3843 | |||
3844 | png_set_sPLT(png_ptr, info_ptr, &palette_ptr, | ||
3845 | num_spalettes); | ||
3846 | |||
3847 | palette_ptr - array of png_sPLT_struct structures | ||
3848 | to be added to the list of palettes | ||
3849 | in the info structure. | ||
3850 | num_spalettes - number of palette structures to be | ||
3851 | added. | ||
3852 | |||
3853 | png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, | ||
3854 | unit_type); | ||
3855 | |||
3856 | offset_x - positive offset from the left | ||
3857 | edge of the screen | ||
3858 | |||
3859 | offset_y - positive offset from the top | ||
3860 | edge of the screen | ||
3861 | |||
3862 | unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER | ||
3863 | |||
3864 | png_set_pHYs(png_ptr, info_ptr, res_x, res_y, | ||
3865 | unit_type); | ||
3866 | |||
3867 | res_x - pixels/unit physical resolution | ||
3868 | in x direction | ||
3869 | |||
3870 | res_y - pixels/unit physical resolution | ||
3871 | in y direction | ||
3872 | |||
3873 | unit_type - PNG_RESOLUTION_UNKNOWN, | ||
3874 | PNG_RESOLUTION_METER | ||
3875 | |||
3876 | png_set_sCAL(png_ptr, info_ptr, unit, width, height) | ||
3877 | |||
3878 | unit - physical scale units (an integer) | ||
3879 | |||
3880 | width - width of a pixel in physical scale units | ||
3881 | |||
3882 | height - height of a pixel in physical scale units | ||
3883 | (width and height are doubles) | ||
3884 | |||
3885 | png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) | ||
3886 | |||
3887 | unit - physical scale units (an integer) | ||
3888 | |||
3889 | width - width of a pixel in physical scale units | ||
3890 | expressed as a string | ||
3891 | |||
3892 | height - height of a pixel in physical scale units | ||
3893 | (width and height are strings like "2.54") | ||
3894 | |||
3895 | png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, | ||
3896 | num_unknowns) | ||
3897 | |||
3898 | unknowns - array of png_unknown_chunk | ||
3899 | structures holding unknown chunks | ||
3900 | unknowns[i].name - name of unknown chunk | ||
3901 | unknowns[i].data - data of unknown chunk | ||
3902 | unknowns[i].size - size of unknown chunk's data | ||
3903 | unknowns[i].location - position to write chunk in file | ||
3904 | 0: do not write chunk | ||
3905 | PNG_HAVE_IHDR: before PLTE | ||
3906 | PNG_HAVE_PLTE: before IDAT | ||
3907 | PNG_AFTER_IDAT: after IDAT | ||
3908 | |||
3909 | The "location" member is set automatically according to | ||
3910 | what part of the output file has already been written. | ||
3911 | You can change its value after calling png_set_unknown_chunks() | ||
3912 | as demonstrated in pngtest.c. Within each of the "locations", | ||
3913 | the chunks are sequenced according to their position in the | ||
3914 | structure (that is, the value of "i", which is the order in which | ||
3915 | the chunk was either read from the input file or defined with | ||
3916 | png_set_unknown_chunks). | ||
3917 | |||
3918 | A quick word about text and num_text. text is an array of png_text | ||
3919 | structures. num_text is the number of valid structures in the array. | ||
3920 | Each png_text structure holds a language code, a keyword, a text value, | ||
3921 | and a compression type. | ||
3922 | |||
3923 | The compression types have the same valid numbers as the compression | ||
3924 | types of the image data. Currently, the only valid number is zero. | ||
3925 | However, you can store text either compressed or uncompressed, unlike | ||
3926 | images, which always have to be compressed. So if you don't want the | ||
3927 | text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE. | ||
3928 | Because tEXt and zTXt chunks don't have a language field, if you | ||
3929 | specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt | ||
3930 | any language code or translated keyword will not be written out. | ||
3931 | |||
3932 | Until text gets around a few hundred bytes, it is not worth compressing it. | ||
3933 | After the text has been written out to the file, the compression type | ||
3934 | is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, | ||
3935 | so that it isn't written out again at the end (in case you are calling | ||
3936 | png_write_end() with the same struct). | ||
3937 | |||
3938 | The keywords that are given in the PNG Specification are: | ||
3939 | |||
3940 | Title Short (one line) title or | ||
3941 | caption for image | ||
3942 | |||
3943 | Author Name of image's creator | ||
3944 | |||
3945 | Description Description of image (possibly long) | ||
3946 | |||
3947 | Copyright Copyright notice | ||
3948 | |||
3949 | Creation Time Time of original image creation | ||
3950 | (usually RFC 1123 format, see below) | ||
3951 | |||
3952 | Software Software used to create the image | ||
3953 | |||
3954 | Disclaimer Legal disclaimer | ||
3955 | |||
3956 | Warning Warning of nature of content | ||
3957 | |||
3958 | Source Device used to create the image | ||
3959 | |||
3960 | Comment Miscellaneous comment; conversion | ||
3961 | from other image format | ||
3962 | |||
3963 | The keyword-text pairs work like this. Keywords should be short | ||
3964 | simple descriptions of what the comment is about. Some typical | ||
3965 | keywords are found in the PNG specification, as is some recommendations | ||
3966 | on keywords. You can repeat keywords in a file. You can even write | ||
3967 | some text before the image and some after. For example, you may want | ||
3968 | to put a description of the image before the image, but leave the | ||
3969 | disclaimer until after, so viewers working over modem connections | ||
3970 | don't have to wait for the disclaimer to go over the modem before | ||
3971 | they start seeing the image. Finally, keywords should be full | ||
3972 | words, not abbreviations. Keywords and text are in the ISO 8859-1 | ||
3973 | (Latin-1) character set (a superset of regular ASCII) and can not | ||
3974 | contain NUL characters, and should not contain control or other | ||
3975 | unprintable characters. To make the comments widely readable, stick | ||
3976 | with basic ASCII, and avoid machine specific character set extensions | ||
3977 | like the IBM-PC character set. The keyword must be present, but | ||
3978 | you can leave off the text string on non-compressed pairs. | ||
3979 | Compressed pairs must have a text string, as only the text string | ||
3980 | is compressed anyway, so the compression would be meaningless. | ||
3981 | |||
3982 | PNG supports modification time via the png_time structure. Two | ||
3983 | conversion routines are provided, png_convert_from_time_t() for | ||
3984 | time_t and png_convert_from_struct_tm() for struct tm. The | ||
3985 | time_t routine uses gmtime(). You don't have to use either of | ||
3986 | these, but if you wish to fill in the png_time structure directly, | ||
3987 | you should provide the time in universal time (GMT) if possible | ||
3988 | instead of your local time. Note that the year number is the full | ||
3989 | year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and | ||
3990 | that months start with 1. | ||
3991 | |||
3992 | If you want to store the time of the original image creation, you should | ||
3993 | use a plain tEXt chunk with the "Creation Time" keyword. This is | ||
3994 | necessary because the "creation time" of a PNG image is somewhat vague, | ||
3995 | depending on whether you mean the PNG file, the time the image was | ||
3996 | created in a non-PNG format, a still photo from which the image was | ||
3997 | scanned, or possibly the subject matter itself. In order to facilitate | ||
3998 | machine-readable dates, it is recommended that the "Creation Time" | ||
3999 | tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"), | ||
4000 | although this isn't a requirement. Unlike the tIME chunk, the | ||
4001 | "Creation Time" tEXt chunk is not expected to be automatically changed | ||
4002 | by the software. To facilitate the use of RFC 1123 dates, a function | ||
4003 | png_convert_to_rfc1123(png_timep) is provided to convert from PNG | ||
4004 | time to an RFC 1123 format string. | ||
4005 | |||
4006 | .SS Writing unknown chunks | ||
4007 | |||
4008 | You can use the png_set_unknown_chunks function to queue up chunks | ||
4009 | for writing. You give it a chunk name, raw data, and a size; that's | ||
4010 | all there is to it. The chunks will be written by the next following | ||
4011 | png_write_info_before_PLTE, png_write_info, or png_write_end function. | ||
4012 | Any chunks previously read into the info structure's unknown-chunk | ||
4013 | list will also be written out in a sequence that satisfies the PNG | ||
4014 | specification's ordering rules. | ||
4015 | |||
4016 | .SS The high-level write interface | ||
4017 | |||
4018 | At this point there are two ways to proceed; through the high-level | ||
4019 | write interface, or through a sequence of low-level write operations. | ||
4020 | You can use the high-level interface if your image data is present | ||
4021 | in the info structure. All defined output | ||
4022 | transformations are permitted, enabled by the following masks. | ||
4023 | |||
4024 | PNG_TRANSFORM_IDENTITY No transformation | ||
4025 | PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples | ||
4026 | PNG_TRANSFORM_PACKSWAP Change order of packed | ||
4027 | pixels to LSB first | ||
4028 | PNG_TRANSFORM_INVERT_MONO Invert monochrome images | ||
4029 | PNG_TRANSFORM_SHIFT Normalize pixels to the | ||
4030 | sBIT depth | ||
4031 | PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA | ||
4032 | to BGRA | ||
4033 | PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA | ||
4034 | to AG | ||
4035 | PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity | ||
4036 | to transparency | ||
4037 | PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples | ||
4038 | PNG_TRANSFORM_STRIP_FILLER Strip out filler | ||
4039 | bytes (deprecated). | ||
4040 | PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading | ||
4041 | filler bytes | ||
4042 | PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing | ||
4043 | filler bytes | ||
4044 | |||
4045 | If you have valid image data in the info structure (you can use | ||
4046 | png_set_rows() to put image data in the info structure), simply do this: | ||
4047 | |||
4048 | png_write_png(png_ptr, info_ptr, png_transforms, NULL) | ||
4049 | |||
4050 | where png_transforms is an integer containing the bitwise OR of some set of | ||
4051 | transformation flags. This call is equivalent to png_write_info(), | ||
4052 | followed the set of transformations indicated by the transform mask, | ||
4053 | then png_write_image(), and finally png_write_end(). | ||
4054 | |||
4055 | (The final parameter of this call is not yet used. Someday it might point | ||
4056 | to transformation parameters required by some future output transform.) | ||
4057 | |||
4058 | You must use png_transforms and not call any png_set_transform() functions | ||
4059 | when you use png_write_png(). | ||
4060 | |||
4061 | .SS The low-level write interface | ||
4062 | |||
4063 | If you are going the low-level route instead, you are now ready to | ||
4064 | write all the file information up to the actual image data. You do | ||
4065 | this with a call to png_write_info(). | ||
4066 | |||
4067 | png_write_info(png_ptr, info_ptr); | ||
4068 | |||
4069 | Note that there is one transformation you may need to do before | ||
4070 | png_write_info(). In PNG files, the alpha channel in an image is the | ||
4071 | level of opacity. If your data is supplied as a level of transparency, | ||
4072 | you can invert the alpha channel before you write it, so that 0 is | ||
4073 | fully transparent and 255 (in 8-bit or paletted images) or 65535 | ||
4074 | (in 16-bit images) is fully opaque, with | ||
4075 | |||
4076 | png_set_invert_alpha(png_ptr); | ||
4077 | |||
4078 | This must appear before png_write_info() instead of later with the | ||
4079 | other transformations because in the case of paletted images the tRNS | ||
4080 | chunk data has to be inverted before the tRNS chunk is written. If | ||
4081 | your image is not a paletted image, the tRNS data (which in such cases | ||
4082 | represents a single color to be rendered as transparent) won't need to | ||
4083 | be changed, and you can safely do this transformation after your | ||
4084 | png_write_info() call. | ||
4085 | |||
4086 | If you need to write a private chunk that you want to appear before | ||
4087 | the PLTE chunk when PLTE is present, you can write the PNG info in | ||
4088 | two steps, and insert code to write your own chunk between them: | ||
4089 | |||
4090 | png_write_info_before_PLTE(png_ptr, info_ptr); | ||
4091 | png_set_unknown_chunks(png_ptr, info_ptr, ...); | ||
4092 | png_write_info(png_ptr, info_ptr); | ||
4093 | |||
4094 | After you've written the file information, you can set up the library | ||
4095 | to handle any special transformations of the image data. The various | ||
4096 | ways to transform the data will be described in the order that they | ||
4097 | should occur. This is important, as some of these change the color | ||
4098 | type and/or bit depth of the data, and some others only work on | ||
4099 | certain color types and bit depths. Even though each transformation | ||
4100 | checks to see if it has data that it can do something with, you should | ||
4101 | make sure to only enable a transformation if it will be valid for the | ||
4102 | data. For example, don't swap red and blue on grayscale data. | ||
4103 | |||
4104 | PNG files store RGB pixels packed into 3 or 6 bytes. This code tells | ||
4105 | the library to strip input data that has 4 or 8 bytes per pixel down | ||
4106 | to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2 | ||
4107 | bytes per pixel). | ||
4108 | |||
4109 | png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); | ||
4110 | |||
4111 | where the 0 is unused, and the location is either PNG_FILLER_BEFORE or | ||
4112 | PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel | ||
4113 | is stored XRGB or RGBX. | ||
4114 | |||
4115 | PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as | ||
4116 | they can, resulting in, for example, 8 pixels per byte for 1 bit files. | ||
4117 | If the data is supplied at 1 pixel per byte, use this code, which will | ||
4118 | correctly pack the pixels into a single byte: | ||
4119 | |||
4120 | png_set_packing(png_ptr); | ||
4121 | |||
4122 | PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your | ||
4123 | data is of another bit depth, you can write an sBIT chunk into the | ||
4124 | file so that decoders can recover the original data if desired. | ||
4125 | |||
4126 | /* Set the true bit depth of the image data */ | ||
4127 | if (color_type & PNG_COLOR_MASK_COLOR) | ||
4128 | { | ||
4129 | sig_bit.red = true_bit_depth; | ||
4130 | sig_bit.green = true_bit_depth; | ||
4131 | sig_bit.blue = true_bit_depth; | ||
4132 | } | ||
4133 | |||
4134 | else | ||
4135 | { | ||
4136 | sig_bit.gray = true_bit_depth; | ||
4137 | } | ||
4138 | |||
4139 | if (color_type & PNG_COLOR_MASK_ALPHA) | ||
4140 | { | ||
4141 | sig_bit.alpha = true_bit_depth; | ||
4142 | } | ||
4143 | |||
4144 | png_set_sBIT(png_ptr, info_ptr, &sig_bit); | ||
4145 | |||
4146 | If the data is stored in the row buffer in a bit depth other than | ||
4147 | one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG), | ||
4148 | this will scale the values to appear to be the correct bit depth as | ||
4149 | is required by PNG. | ||
4150 | |||
4151 | png_set_shift(png_ptr, &sig_bit); | ||
4152 | |||
4153 | PNG files store 16-bit pixels in network byte order (big-endian, | ||
4154 | ie. most significant bits first). This code would be used if they are | ||
4155 | supplied the other way (little-endian, i.e. least significant bits | ||
4156 | first, the way PCs store them): | ||
4157 | |||
4158 | if (bit_depth > 8) | ||
4159 | png_set_swap(png_ptr); | ||
4160 | |||
4161 | If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you | ||
4162 | need to change the order the pixels are packed into bytes, you can use: | ||
4163 | |||
4164 | if (bit_depth < 8) | ||
4165 | png_set_packswap(png_ptr); | ||
4166 | |||
4167 | PNG files store 3 color pixels in red, green, blue order. This code | ||
4168 | would be used if they are supplied as blue, green, red: | ||
4169 | |||
4170 | png_set_bgr(png_ptr); | ||
4171 | |||
4172 | PNG files describe monochrome as black being zero and white being | ||
4173 | one. This code would be used if the pixels are supplied with this reversed | ||
4174 | (black being one and white being zero): | ||
4175 | |||
4176 | png_set_invert_mono(png_ptr); | ||
4177 | |||
4178 | Finally, you can write your own transformation function if none of | ||
4179 | the existing ones meets your needs. This is done by setting a callback | ||
4180 | with | ||
4181 | |||
4182 | png_set_write_user_transform_fn(png_ptr, | ||
4183 | write_transform_fn); | ||
4184 | |||
4185 | You must supply the function | ||
4186 | |||
4187 | void write_transform_fn(png_structp png_ptr, png_row_infop | ||
4188 | row_info, png_bytep data) | ||
4189 | |||
4190 | See pngtest.c for a working example. Your function will be called | ||
4191 | before any of the other transformations are processed. If supported | ||
4192 | libpng also supplies an information routine that may be called from | ||
4193 | your callback: | ||
4194 | |||
4195 | png_get_current_row_number(png_ptr); | ||
4196 | png_get_current_pass_number(png_ptr); | ||
4197 | |||
4198 | This returns the current row passed to the transform. With interlaced | ||
4199 | images the value returned is the row in the input sub-image image. Use | ||
4200 | PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to | ||
4201 | find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). | ||
4202 | |||
4203 | The discussion of interlace handling above contains more information on how to | ||
4204 | use these values. | ||
4205 | |||
4206 | You can also set up a pointer to a user structure for use by your | ||
4207 | callback function. | ||
4208 | |||
4209 | png_set_user_transform_info(png_ptr, user_ptr, 0, 0); | ||
4210 | |||
4211 | The user_channels and user_depth parameters of this function are ignored | ||
4212 | when writing; you can set them to zero as shown. | ||
4213 | |||
4214 | You can retrieve the pointer via the function png_get_user_transform_ptr(). | ||
4215 | For example: | ||
4216 | |||
4217 | voidp write_user_transform_ptr = | ||
4218 | png_get_user_transform_ptr(png_ptr); | ||
4219 | |||
4220 | It is possible to have libpng flush any pending output, either manually, | ||
4221 | or automatically after a certain number of lines have been written. To | ||
4222 | flush the output stream a single time call: | ||
4223 | |||
4224 | png_write_flush(png_ptr); | ||
4225 | |||
4226 | and to have libpng flush the output stream periodically after a certain | ||
4227 | number of scanlines have been written, call: | ||
4228 | |||
4229 | png_set_flush(png_ptr, nrows); | ||
4230 | |||
4231 | Note that the distance between rows is from the last time png_write_flush() | ||
4232 | was called, or the first row of the image if it has never been called. | ||
4233 | So if you write 50 lines, and then png_set_flush 25, it will flush the | ||
4234 | output on the next scanline, and every 25 lines thereafter, unless | ||
4235 | png_write_flush() is called before 25 more lines have been written. | ||
4236 | If nrows is too small (less than about 10 lines for a 640 pixel wide | ||
4237 | RGB image) the image compression may decrease noticeably (although this | ||
4238 | may be acceptable for real-time applications). Infrequent flushing will | ||
4239 | only degrade the compression performance by a few percent over images | ||
4240 | that do not use flushing. | ||
4241 | |||
4242 | .SS Writing the image data | ||
4243 | |||
4244 | That's it for the transformations. Now you can write the image data. | ||
4245 | The simplest way to do this is in one function call. If you have the | ||
4246 | whole image in memory, you can just call png_write_image() and libpng | ||
4247 | will write the image. You will need to pass in an array of pointers to | ||
4248 | each row. This function automatically handles interlacing, so you don't | ||
4249 | need to call png_set_interlace_handling() or call this function multiple | ||
4250 | times, or any of that other stuff necessary with png_write_rows(). | ||
4251 | |||
4252 | png_write_image(png_ptr, row_pointers); | ||
4253 | |||
4254 | where row_pointers is: | ||
4255 | |||
4256 | png_byte *row_pointers[height]; | ||
4257 | |||
4258 | You can point to void or char or whatever you use for pixels. | ||
4259 | |||
4260 | If you don't want to write the whole image at once, you can | ||
4261 | use png_write_rows() instead. If the file is not interlaced, | ||
4262 | this is simple: | ||
4263 | |||
4264 | png_write_rows(png_ptr, row_pointers, | ||
4265 | number_of_rows); | ||
4266 | |||
4267 | row_pointers is the same as in the png_write_image() call. | ||
4268 | |||
4269 | If you are just writing one row at a time, you can do this with | ||
4270 | a single row_pointer instead of an array of row_pointers: | ||
4271 | |||
4272 | png_bytep row_pointer = row; | ||
4273 | |||
4274 | png_write_row(png_ptr, row_pointer); | ||
4275 | |||
4276 | When the file is interlaced, things can get a good deal more complicated. | ||
4277 | The only currently (as of the PNG Specification version 1.2, dated July | ||
4278 | 1999) defined interlacing scheme for PNG files is the "Adam7" interlace | ||
4279 | scheme, that breaks down an image into seven smaller images of varying | ||
4280 | size. libpng will build these images for you, or you can do them | ||
4281 | yourself. If you want to build them yourself, see the PNG specification | ||
4282 | for details of which pixels to write when. | ||
4283 | |||
4284 | If you don't want libpng to handle the interlacing details, just | ||
4285 | use png_set_interlace_handling() and call png_write_rows() the | ||
4286 | correct number of times to write all the sub-images | ||
4287 | (png_set_interlace_handling() returns the number of sub-images.) | ||
4288 | |||
4289 | If you want libpng to build the sub-images, call this before you start | ||
4290 | writing any rows: | ||
4291 | |||
4292 | number_of_passes = png_set_interlace_handling(png_ptr); | ||
4293 | |||
4294 | This will return the number of passes needed. Currently, this is seven, | ||
4295 | but may change if another interlace type is added. | ||
4296 | |||
4297 | Then write the complete image number_of_passes times. | ||
4298 | |||
4299 | png_write_rows(png_ptr, row_pointers, number_of_rows); | ||
4300 | |||
4301 | Think carefully before you write an interlaced image. Typically code that | ||
4302 | reads such images reads all the image data into memory, uncompressed, before | ||
4303 | doing any processing. Only code that can display an image on the fly can | ||
4304 | take advantage of the interlacing and even then the image has to be exactly | ||
4305 | the correct size for the output device, because scaling an image requires | ||
4306 | adjacent pixels and these are not available until all the passes have been | ||
4307 | read. | ||
4308 | |||
4309 | If you do write an interlaced image you will hardly ever need to handle | ||
4310 | the interlacing yourself. Call png_set_interlace_handling() and use the | ||
4311 | approach described above. | ||
4312 | |||
4313 | The only time it is conceivable that you will really need to write an | ||
4314 | interlaced image pass-by-pass is when you have read one pass by pass and | ||
4315 | made some pixel-by-pixel transformation to it, as described in the read | ||
4316 | code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros | ||
4317 | to determine the size of each sub-image in turn and simply write the rows | ||
4318 | you obtained from the read code. | ||
4319 | |||
4320 | .SS Finishing a sequential write | ||
4321 | |||
4322 | After you are finished writing the image, you should finish writing | ||
4323 | the file. If you are interested in writing comments or time, you should | ||
4324 | pass an appropriately filled png_info pointer. If you are not interested, | ||
4325 | you can pass NULL. | ||
4326 | |||
4327 | png_write_end(png_ptr, info_ptr); | ||
4328 | |||
4329 | When you are done, you can free all memory used by libpng like this: | ||
4330 | |||
4331 | png_destroy_write_struct(&png_ptr, &info_ptr); | ||
4332 | |||
4333 | It is also possible to individually free the info_ptr members that | ||
4334 | point to libpng-allocated storage with the following function: | ||
4335 | |||
4336 | png_free_data(png_ptr, info_ptr, mask, seq) | ||
4337 | |||
4338 | mask - identifies data to be freed, a mask | ||
4339 | containing the bitwise OR of one or | ||
4340 | more of | ||
4341 | PNG_FREE_PLTE, PNG_FREE_TRNS, | ||
4342 | PNG_FREE_HIST, PNG_FREE_ICCP, | ||
4343 | PNG_FREE_PCAL, PNG_FREE_ROWS, | ||
4344 | PNG_FREE_SCAL, PNG_FREE_SPLT, | ||
4345 | PNG_FREE_TEXT, PNG_FREE_UNKN, | ||
4346 | or simply PNG_FREE_ALL | ||
4347 | |||
4348 | seq - sequence number of item to be freed | ||
4349 | (-1 for all items) | ||
4350 | |||
4351 | This function may be safely called when the relevant storage has | ||
4352 | already been freed, or has not yet been allocated, or was allocated | ||
4353 | by the user and not by libpng, and will in those cases do nothing. | ||
4354 | The "seq" parameter is ignored if only one item of the selected data | ||
4355 | type, such as PLTE, is allowed. If "seq" is not -1, and multiple items | ||
4356 | are allowed for the data type identified in the mask, such as text or | ||
4357 | sPLT, only the n'th item in the structure is freed, where n is "seq". | ||
4358 | |||
4359 | If you allocated data such as a palette that you passed in to libpng | ||
4360 | with png_set_*, you must not free it until just before the call to | ||
4361 | png_destroy_write_struct(). | ||
4362 | |||
4363 | The default behavior is only to free data that was allocated internally | ||
4364 | by libpng. This can be changed, so that libpng will not free the data, | ||
4365 | or so that it will free data that was allocated by the user with png_malloc() | ||
4366 | or png_zalloc() and passed in via a png_set_*() function, with | ||
4367 | |||
4368 | png_data_freer(png_ptr, info_ptr, freer, mask) | ||
4369 | |||
4370 | freer - one of | ||
4371 | PNG_DESTROY_WILL_FREE_DATA | ||
4372 | PNG_SET_WILL_FREE_DATA | ||
4373 | PNG_USER_WILL_FREE_DATA | ||
4374 | |||
4375 | mask - which data elements are affected | ||
4376 | same choices as in png_free_data() | ||
4377 | |||
4378 | For example, to transfer responsibility for some data from a read structure | ||
4379 | to a write structure, you could use | ||
4380 | |||
4381 | png_data_freer(read_ptr, read_info_ptr, | ||
4382 | PNG_USER_WILL_FREE_DATA, | ||
4383 | PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) | ||
4384 | |||
4385 | png_data_freer(write_ptr, write_info_ptr, | ||
4386 | PNG_DESTROY_WILL_FREE_DATA, | ||
4387 | PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) | ||
4388 | |||
4389 | thereby briefly reassigning responsibility for freeing to the user but | ||
4390 | immediately afterwards reassigning it once more to the write_destroy | ||
4391 | function. Having done this, it would then be safe to destroy the read | ||
4392 | structure and continue to use the PLTE, tRNS, and hIST data in the write | ||
4393 | structure. | ||
4394 | |||
4395 | This function only affects data that has already been allocated. | ||
4396 | You can call this function before calling after the png_set_*() functions | ||
4397 | to control whether the user or png_destroy_*() is supposed to free the data. | ||
4398 | When the user assumes responsibility for libpng-allocated data, the | ||
4399 | application must use | ||
4400 | png_free() to free it, and when the user transfers responsibility to libpng | ||
4401 | for data that the user has allocated, the user must have used png_malloc() | ||
4402 | or png_zalloc() to allocate it. | ||
4403 | |||
4404 | If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword | ||
4405 | separately, do not transfer responsibility for freeing text_ptr to libpng, | ||
4406 | because when libpng fills a png_text structure it combines these members with | ||
4407 | the key member, and png_free_data() will free only text_ptr.key. Similarly, | ||
4408 | if you transfer responsibility for free'ing text_ptr from libpng to your | ||
4409 | application, your application must not separately free those members. | ||
4410 | For a more compact example of writing a PNG image, see the file example.c. | ||
4411 | |||
4412 | .SH V. Modifying/Customizing libpng: | ||
4413 | |||
4414 | There are two issues here. The first is changing how libpng does | ||
4415 | standard things like memory allocation, input/output, and error handling. | ||
4416 | The second deals with more complicated things like adding new chunks, | ||
4417 | adding new transformations, and generally changing how libpng works. | ||
4418 | Both of those are compile-time issues; that is, they are generally | ||
4419 | determined at the time the code is written, and there is rarely a need | ||
4420 | to provide the user with a means of changing them. | ||
4421 | |||
4422 | Memory allocation, input/output, and error handling | ||
4423 | |||
4424 | All of the memory allocation, input/output, and error handling in libpng | ||
4425 | goes through callbacks that are user-settable. The default routines are | ||
4426 | in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change | ||
4427 | these functions, call the appropriate png_set_*_fn() function. | ||
4428 | |||
4429 | Memory allocation is done through the functions png_malloc(), png_calloc(), | ||
4430 | and png_free(). These currently just call the standard C functions. | ||
4431 | png_calloc() calls png_malloc() and then clears the newly | ||
4432 | allocated memory to zero. There is limited support for certain systems | ||
4433 | with segmented memory architectures and the types of pointers declared by | ||
4434 | png.h match this; you will have to use appropriate pointers in your | ||
4435 | application. Since it is | ||
4436 | unlikely that the method of handling memory allocation on a platform | ||
4437 | will change between applications, these functions must be modified in | ||
4438 | the library at compile time. If you prefer to use a different method | ||
4439 | of allocating and freeing data, you can use png_create_read_struct_2() or | ||
4440 | png_create_write_struct_2() to register your own functions as described | ||
4441 | above. These functions also provide a void pointer that can be retrieved | ||
4442 | via | ||
4443 | |||
4444 | mem_ptr=png_get_mem_ptr(png_ptr); | ||
4445 | |||
4446 | Your replacement memory functions must have prototypes as follows: | ||
4447 | |||
4448 | png_voidp malloc_fn(png_structp png_ptr, | ||
4449 | png_alloc_size_t size); | ||
4450 | |||
4451 | void free_fn(png_structp png_ptr, png_voidp ptr); | ||
4452 | |||
4453 | Your malloc_fn() must return NULL in case of failure. The png_malloc() | ||
4454 | function will normally call png_error() if it receives a NULL from the | ||
4455 | system memory allocator or from your replacement malloc_fn(). | ||
4456 | |||
4457 | Your free_fn() will never be called with a NULL ptr, since libpng's | ||
4458 | png_free() checks for NULL before calling free_fn(). | ||
4459 | |||
4460 | Input/Output in libpng is done through png_read() and png_write(), | ||
4461 | which currently just call fread() and fwrite(). The FILE * is stored in | ||
4462 | png_struct and is initialized via png_init_io(). If you wish to change | ||
4463 | the method of I/O, the library supplies callbacks that you can set | ||
4464 | through the function png_set_read_fn() and png_set_write_fn() at run | ||
4465 | time, instead of calling the png_init_io() function. These functions | ||
4466 | also provide a void pointer that can be retrieved via the function | ||
4467 | png_get_io_ptr(). For example: | ||
4468 | |||
4469 | png_set_read_fn(png_structp read_ptr, | ||
4470 | voidp read_io_ptr, png_rw_ptr read_data_fn) | ||
4471 | |||
4472 | png_set_write_fn(png_structp write_ptr, | ||
4473 | voidp write_io_ptr, png_rw_ptr write_data_fn, | ||
4474 | png_flush_ptr output_flush_fn); | ||
4475 | |||
4476 | voidp read_io_ptr = png_get_io_ptr(read_ptr); | ||
4477 | voidp write_io_ptr = png_get_io_ptr(write_ptr); | ||
4478 | |||
4479 | The replacement I/O functions must have prototypes as follows: | ||
4480 | |||
4481 | void user_read_data(png_structp png_ptr, | ||
4482 | png_bytep data, png_size_t length); | ||
4483 | |||
4484 | void user_write_data(png_structp png_ptr, | ||
4485 | png_bytep data, png_size_t length); | ||
4486 | |||
4487 | void user_flush_data(png_structp png_ptr); | ||
4488 | |||
4489 | The user_read_data() function is responsible for detecting and | ||
4490 | handling end-of-data errors. | ||
4491 | |||
4492 | Supplying NULL for the read, write, or flush functions sets them back | ||
4493 | to using the default C stream functions, which expect the io_ptr to | ||
4494 | point to a standard *FILE structure. It is probably a mistake | ||
4495 | to use NULL for one of write_data_fn and output_flush_fn but not both | ||
4496 | of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined. | ||
4497 | It is an error to read from a write stream, and vice versa. | ||
4498 | |||
4499 | Error handling in libpng is done through png_error() and png_warning(). | ||
4500 | Errors handled through png_error() are fatal, meaning that png_error() | ||
4501 | should never return to its caller. Currently, this is handled via | ||
4502 | setjmp() and longjmp() (unless you have compiled libpng with | ||
4503 | PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()), | ||
4504 | but you could change this to do things like exit() if you should wish, | ||
4505 | as long as your function does not return. | ||
4506 | |||
4507 | On non-fatal errors, png_warning() is called | ||
4508 | to print a warning message, and then control returns to the calling code. | ||
4509 | By default png_error() and png_warning() print a message on stderr via | ||
4510 | fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined | ||
4511 | (because you don't want the messages) or PNG_NO_STDIO defined (because | ||
4512 | fprintf() isn't available). If you wish to change the behavior of the error | ||
4513 | functions, you will need to set up your own message callbacks. These | ||
4514 | functions are normally supplied at the time that the png_struct is created. | ||
4515 | It is also possible to redirect errors and warnings to your own replacement | ||
4516 | functions after png_create_*_struct() has been called by calling: | ||
4517 | |||
4518 | png_set_error_fn(png_structp png_ptr, | ||
4519 | png_voidp error_ptr, png_error_ptr error_fn, | ||
4520 | png_error_ptr warning_fn); | ||
4521 | |||
4522 | png_voidp error_ptr = png_get_error_ptr(png_ptr); | ||
4523 | |||
4524 | If NULL is supplied for either error_fn or warning_fn, then the libpng | ||
4525 | default function will be used, calling fprintf() and/or longjmp() if a | ||
4526 | problem is encountered. The replacement error functions should have | ||
4527 | parameters as follows: | ||
4528 | |||
4529 | void user_error_fn(png_structp png_ptr, | ||
4530 | png_const_charp error_msg); | ||
4531 | |||
4532 | void user_warning_fn(png_structp png_ptr, | ||
4533 | png_const_charp warning_msg); | ||
4534 | |||
4535 | The motivation behind using setjmp() and longjmp() is the C++ throw and | ||
4536 | catch exception handling methods. This makes the code much easier to write, | ||
4537 | as there is no need to check every return code of every function call. | ||
4538 | However, there are some uncertainties about the status of local variables | ||
4539 | after a longjmp, so the user may want to be careful about doing anything | ||
4540 | after setjmp returns non-zero besides returning itself. Consult your | ||
4541 | compiler documentation for more details. For an alternative approach, you | ||
4542 | may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net), | ||
4543 | which is illustrated in pngvalid.c and in contrib/visupng. | ||
4544 | |||
4545 | .SS Custom chunks | ||
4546 | |||
4547 | If you need to read or write custom chunks, you may need to get deeper | ||
4548 | into the libpng code. The library now has mechanisms for storing | ||
4549 | and writing chunks of unknown type; you can even declare callbacks | ||
4550 | for custom chunks. However, this may not be good enough if the | ||
4551 | library code itself needs to know about interactions between your | ||
4552 | chunk and existing `intrinsic' chunks. | ||
4553 | |||
4554 | If you need to write a new intrinsic chunk, first read the PNG | ||
4555 | specification. Acquire a first level of understanding of how it works. | ||
4556 | Pay particular attention to the sections that describe chunk names, | ||
4557 | and look at how other chunks were designed, so you can do things | ||
4558 | similarly. Second, check out the sections of libpng that read and | ||
4559 | write chunks. Try to find a chunk that is similar to yours and use | ||
4560 | it as a template. More details can be found in the comments inside | ||
4561 | the code. It is best to handle private or unknown chunks in a generic method, | ||
4562 | via callback functions, instead of by modifying libpng functions. This | ||
4563 | is illustrated in pngtest.c, which uses a callback function to handle a | ||
4564 | private "vpAg" chunk and the new "sTER" chunk, which are both unknown to | ||
4565 | libpng. | ||
4566 | |||
4567 | If you wish to write your own transformation for the data, look through | ||
4568 | the part of the code that does the transformations, and check out some of | ||
4569 | the simpler ones to get an idea of how they work. Try to find a similar | ||
4570 | transformation to the one you want to add and copy off of it. More details | ||
4571 | can be found in the comments inside the code itself. | ||
4572 | |||
4573 | .SS Configuring for 16-bit platforms | ||
4574 | |||
4575 | You will want to look into zconf.h to tell zlib (and thus libpng) that | ||
4576 | it cannot allocate more then 64K at a time. Even if you can, the memory | ||
4577 | won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K. | ||
4578 | |||
4579 | .SS Configuring for DOS | ||
4580 | |||
4581 | For DOS users who only have access to the lower 640K, you will | ||
4582 | have to limit zlib's memory usage via a png_set_compression_mem_level() | ||
4583 | call. See zlib.h or zconf.h in the zlib library for more information. | ||
4584 | |||
4585 | .SS Configuring for Medium Model | ||
4586 | |||
4587 | Libpng's support for medium model has been tested on most of the popular | ||
4588 | compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets | ||
4589 | defined, and FAR gets defined to far in pngconf.h, and you should be | ||
4590 | all set. Everything in the library (except for zlib's structure) is | ||
4591 | expecting far data. You must use the typedefs with the p or pp on | ||
4592 | the end for pointers (or at least look at them and be careful). Make | ||
4593 | note that the rows of data are defined as png_bytepp, which is | ||
4594 | an "unsigned char far * far *". | ||
4595 | |||
4596 | .SS Configuring for gui/windowing platforms: | ||
4597 | |||
4598 | You will need to write new error and warning functions that use the GUI | ||
4599 | interface, as described previously, and set them to be the error and | ||
4600 | warning functions at the time that png_create_*_struct() is called, | ||
4601 | in order to have them available during the structure initialization. | ||
4602 | They can be changed later via png_set_error_fn(). On some compilers, | ||
4603 | you may also have to change the memory allocators (png_malloc, etc.). | ||
4604 | |||
4605 | .SS Configuring for compiler xxx: | ||
4606 | |||
4607 | All includes for libpng are in pngconf.h. If you need to add, change | ||
4608 | or delete an include, this is the place to do it. | ||
4609 | The includes that are not needed outside libpng are placed in pngpriv.h, | ||
4610 | which is only used by the routines inside libpng itself. | ||
4611 | The files in libpng proper only include pngpriv.h and png.h, which | ||
4612 | %14%in turn includes pngconf.h. | ||
4613 | in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h. | ||
4614 | As of libpng-1.5.0, pngpriv.h also includes three other private header | ||
4615 | files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material | ||
4616 | that previously appeared in the public headers. | ||
4617 | |||
4618 | .SS Configuring zlib: | ||
4619 | |||
4620 | There are special functions to configure the compression. Perhaps the | ||
4621 | most useful one changes the compression level, which currently uses | ||
4622 | input compression values in the range 0 - 9. The library normally | ||
4623 | uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests | ||
4624 | have shown that for a large majority of images, compression values in | ||
4625 | the range 3-6 compress nearly as well as higher levels, and do so much | ||
4626 | faster. For online applications it may be desirable to have maximum speed | ||
4627 | (Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also | ||
4628 | specify no compression (Z_NO_COMPRESSION = 0), but this would create | ||
4629 | files larger than just storing the raw bitmap. You can specify the | ||
4630 | compression level by calling: | ||
4631 | |||
4632 | #include zlib.h | ||
4633 | png_set_compression_level(png_ptr, level); | ||
4634 | |||
4635 | Another useful one is to reduce the memory level used by the library. | ||
4636 | The memory level defaults to 8, but it can be lowered if you are | ||
4637 | short on memory (running DOS, for example, where you only have 640K). | ||
4638 | Note that the memory level does have an effect on compression; among | ||
4639 | other things, lower levels will result in sections of incompressible | ||
4640 | data being emitted in smaller stored blocks, with a correspondingly | ||
4641 | larger relative overhead of up to 15% in the worst case. | ||
4642 | |||
4643 | #include zlib.h | ||
4644 | png_set_compression_mem_level(png_ptr, level); | ||
4645 | |||
4646 | The other functions are for configuring zlib. They are not recommended | ||
4647 | for normal use and may result in writing an invalid PNG file. See | ||
4648 | zlib.h for more information on what these mean. | ||
4649 | |||
4650 | #include zlib.h | ||
4651 | png_set_compression_strategy(png_ptr, | ||
4652 | strategy); | ||
4653 | |||
4654 | png_set_compression_window_bits(png_ptr, | ||
4655 | window_bits); | ||
4656 | |||
4657 | png_set_compression_method(png_ptr, method); | ||
4658 | |||
4659 | png_set_compression_buffer_size(png_ptr, size); | ||
4660 | |||
4661 | As of libpng version 1.5.4, additional APIs became | ||
4662 | available to set these separately for non-IDAT | ||
4663 | compressed chunks such as zTXt, iTXt, and iCCP: | ||
4664 | |||
4665 | #include zlib.h | ||
4666 | #if PNG_LIBPNG_VER <= 10504 | ||
4667 | png_set_text_compression_level(png_ptr, level); | ||
4668 | |||
4669 | png_set_text_compression_mem_level(png_ptr, level); | ||
4670 | |||
4671 | png_set_text_compression_strategy(png_ptr, | ||
4672 | strategy); | ||
4673 | |||
4674 | png_set_text_compression_window_bits(png_ptr, | ||
4675 | window_bits); | ||
4676 | |||
4677 | png_set_text_compression_method(png_ptr, method); | ||
4678 | #endif | ||
4679 | |||
4680 | .SS Controlling row filtering | ||
4681 | |||
4682 | If you want to control whether libpng uses filtering or not, which | ||
4683 | filters are used, and how it goes about picking row filters, you | ||
4684 | can call one of these functions. The selection and configuration | ||
4685 | of row filters can have a significant impact on the size and | ||
4686 | encoding speed and a somewhat lesser impact on the decoding speed | ||
4687 | of an image. Filtering is enabled by default for RGB and grayscale | ||
4688 | images (with and without alpha), but not for paletted images nor | ||
4689 | for any images with bit depths less than 8 bits/pixel. | ||
4690 | |||
4691 | The 'method' parameter sets the main filtering method, which is | ||
4692 | currently only '0' in the PNG 1.2 specification. The 'filters' | ||
4693 | parameter sets which filter(s), if any, should be used for each | ||
4694 | scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS | ||
4695 | to turn filtering on and off, respectively. | ||
4696 | |||
4697 | Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB, | ||
4698 | PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise | ||
4699 | ORed together with '|' to specify one or more filters to use. | ||
4700 | These filters are described in more detail in the PNG specification. | ||
4701 | If you intend to change the filter type during the course of writing | ||
4702 | the image, you should start with flags set for all of the filters | ||
4703 | you intend to use so that libpng can initialize its internal | ||
4704 | structures appropriately for all of the filter types. (Note that this | ||
4705 | means the first row must always be adaptively filtered, because libpng | ||
4706 | currently does not allocate the filter buffers until png_write_row() | ||
4707 | is called for the first time.) | ||
4708 | |||
4709 | filters = PNG_FILTER_NONE | PNG_FILTER_SUB | ||
4710 | PNG_FILTER_UP | PNG_FILTER_AVG | | ||
4711 | PNG_FILTER_PAETH | PNG_ALL_FILTERS; | ||
4712 | |||
4713 | png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, | ||
4714 | filters); | ||
4715 | The second parameter can also be | ||
4716 | PNG_INTRAPIXEL_DIFFERENCING if you are | ||
4717 | writing a PNG to be embedded in a MNG | ||
4718 | datastream. This parameter must be the | ||
4719 | same as the value of filter_method used | ||
4720 | in png_set_IHDR(). | ||
4721 | |||
4722 | It is also possible to influence how libpng chooses from among the | ||
4723 | available filters. This is done in one or both of two ways - by | ||
4724 | telling it how important it is to keep the same filter for successive | ||
4725 | rows, and by telling it the relative computational costs of the filters. | ||
4726 | |||
4727 | double weights[3] = {1.5, 1.3, 1.1}, | ||
4728 | costs[PNG_FILTER_VALUE_LAST] = | ||
4729 | {1.0, 1.3, 1.3, 1.5, 1.7}; | ||
4730 | |||
4731 | png_set_filter_heuristics(png_ptr, | ||
4732 | PNG_FILTER_HEURISTIC_WEIGHTED, 3, | ||
4733 | weights, costs); | ||
4734 | |||
4735 | The weights are multiplying factors that indicate to libpng that the | ||
4736 | row filter should be the same for successive rows unless another row filter | ||
4737 | is that many times better than the previous filter. In the above example, | ||
4738 | if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a | ||
4739 | "sum of absolute differences" 1.5 x 1.3 times higher than other filters | ||
4740 | and still be chosen, while the NONE filter could have a sum 1.1 times | ||
4741 | higher than other filters and still be chosen. Unspecified weights are | ||
4742 | taken to be 1.0, and the specified weights should probably be declining | ||
4743 | like those above in order to emphasize recent filters over older filters. | ||
4744 | |||
4745 | The filter costs specify for each filter type a relative decoding cost | ||
4746 | to be considered when selecting row filters. This means that filters | ||
4747 | with higher costs are less likely to be chosen over filters with lower | ||
4748 | costs, unless their "sum of absolute differences" is that much smaller. | ||
4749 | The costs do not necessarily reflect the exact computational speeds of | ||
4750 | the various filters, since this would unduly influence the final image | ||
4751 | size. | ||
4752 | |||
4753 | Note that the numbers above were invented purely for this example and | ||
4754 | are given only to help explain the function usage. Little testing has | ||
4755 | been done to find optimum values for either the costs or the weights. | ||
4756 | |||
4757 | .SS Removing unwanted object code | ||
4758 | |||
4759 | There are a bunch of #define's in pngconf.h that control what parts of | ||
4760 | libpng are compiled. All the defines end in _SUPPORTED. If you are | ||
4761 | never going to use a capability, you can change the #define to #undef | ||
4762 | before recompiling libpng and save yourself code and data space, or | ||
4763 | you can turn off individual capabilities with defines that begin with | ||
4764 | PNG_NO_. | ||
4765 | |||
4766 | In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead. | ||
4767 | |||
4768 | You can also turn all of the transforms and ancillary chunk capabilities | ||
4769 | off en masse with compiler directives that define | ||
4770 | PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, | ||
4771 | or all four, | ||
4772 | along with directives to turn on any of the capabilities that you do | ||
4773 | want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra | ||
4774 | transformations but still leave the library fully capable of reading | ||
4775 | and writing PNG files with all known public chunks. Use of the | ||
4776 | PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library | ||
4777 | that is incapable of reading or writing ancillary chunks. If you are | ||
4778 | not using the progressive reading capability, you can turn that off | ||
4779 | with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING | ||
4780 | capability, which you'll still have). | ||
4781 | |||
4782 | All the reading and writing specific code are in separate files, so the | ||
4783 | linker should only grab the files it needs. However, if you want to | ||
4784 | make sure, or if you are building a stand alone library, all the | ||
4785 | reading files start with "pngr" and all the writing files start with "pngw". | ||
4786 | The files that don't match either (like png.c, pngtrans.c, etc.) | ||
4787 | are used for both reading and writing, and always need to be included. | ||
4788 | The progressive reader is in pngpread.c | ||
4789 | |||
4790 | If you are creating or distributing a dynamically linked library (a .so | ||
4791 | or DLL file), you should not remove or disable any parts of the library, | ||
4792 | as this will cause applications linked with different versions of the | ||
4793 | library to fail if they call functions not available in your library. | ||
4794 | The size of the library itself should not be an issue, because only | ||
4795 | those sections that are actually used will be loaded into memory. | ||
4796 | |||
4797 | .SS Requesting debug printout | ||
4798 | |||
4799 | The macro definition PNG_DEBUG can be used to request debugging | ||
4800 | printout. Set it to an integer value in the range 0 to 3. Higher | ||
4801 | numbers result in increasing amounts of debugging information. The | ||
4802 | information is printed to the "stderr" file, unless another file | ||
4803 | name is specified in the PNG_DEBUG_FILE macro definition. | ||
4804 | |||
4805 | When PNG_DEBUG > 0, the following functions (macros) become available: | ||
4806 | |||
4807 | png_debug(level, message) | ||
4808 | png_debug1(level, message, p1) | ||
4809 | png_debug2(level, message, p1, p2) | ||
4810 | |||
4811 | in which "level" is compared to PNG_DEBUG to decide whether to print | ||
4812 | the message, "message" is the formatted string to be printed, | ||
4813 | and p1 and p2 are parameters that are to be embedded in the string | ||
4814 | according to printf-style formatting directives. For example, | ||
4815 | |||
4816 | png_debug1(2, "foo=%d\n", foo); | ||
4817 | |||
4818 | is expanded to | ||
4819 | |||
4820 | if (PNG_DEBUG > 2) | ||
4821 | fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); | ||
4822 | |||
4823 | When PNG_DEBUG is defined but is zero, the macros aren't defined, but you | ||
4824 | can still use PNG_DEBUG to control your own debugging: | ||
4825 | |||
4826 | #ifdef PNG_DEBUG | ||
4827 | fprintf(stderr, ... | ||
4828 | #endif | ||
4829 | |||
4830 | When PNG_DEBUG = 1, the macros are defined, but only png_debug statements | ||
4831 | having level = 0 will be printed. There aren't any such statements in | ||
4832 | this version of libpng, but if you insert some they will be printed. | ||
4833 | |||
4834 | .SH VI. MNG support | ||
4835 | |||
4836 | The MNG specification (available at http://www.libpng.org/pub/mng) allows | ||
4837 | certain extensions to PNG for PNG images that are embedded in MNG datastreams. | ||
4838 | Libpng can support some of these extensions. To enable them, use the | ||
4839 | png_permit_mng_features() function: | ||
4840 | |||
4841 | feature_set = png_permit_mng_features(png_ptr, mask) | ||
4842 | |||
4843 | mask is a png_uint_32 containing the bitwise OR of the | ||
4844 | features you want to enable. These include | ||
4845 | PNG_FLAG_MNG_EMPTY_PLTE | ||
4846 | PNG_FLAG_MNG_FILTER_64 | ||
4847 | PNG_ALL_MNG_FEATURES | ||
4848 | |||
4849 | feature_set is a png_uint_32 that is the bitwise AND of | ||
4850 | your mask with the set of MNG features that is | ||
4851 | supported by the version of libpng that you are using. | ||
4852 | |||
4853 | It is an error to use this function when reading or writing a standalone | ||
4854 | PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped | ||
4855 | in a MNG datastream. As a minimum, it must have the MNG 8-byte signature | ||
4856 | and the MHDR and MEND chunks. Libpng does not provide support for these | ||
4857 | or any other MNG chunks; your application must provide its own support for | ||
4858 | them. You may wish to consider using libmng (available at | ||
4859 | http://www.libmng.com) instead. | ||
4860 | |||
4861 | .SH VII. Changes to Libpng from version 0.88 | ||
4862 | |||
4863 | It should be noted that versions of libpng later than 0.96 are not | ||
4864 | distributed by the original libpng author, Guy Schalnat, nor by | ||
4865 | Andreas Dilger, who had taken over from Guy during 1996 and 1997, and | ||
4866 | distributed versions 0.89 through 0.96, but rather by another member | ||
4867 | of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are | ||
4868 | still alive and well, but they have moved on to other things. | ||
4869 | |||
4870 | The old libpng functions png_read_init(), png_write_init(), | ||
4871 | png_info_init(), png_read_destroy(), and png_write_destroy() have been | ||
4872 | moved to PNG_INTERNAL in version 0.95 to discourage their use. These | ||
4873 | functions will be removed from libpng version 1.4.0. | ||
4874 | |||
4875 | The preferred method of creating and initializing the libpng structures is | ||
4876 | via the png_create_read_struct(), png_create_write_struct(), and | ||
4877 | png_create_info_struct() because they isolate the size of the structures | ||
4878 | from the application, allow version error checking, and also allow the | ||
4879 | use of custom error handling routines during the initialization, which | ||
4880 | the old functions do not. The functions png_read_destroy() and | ||
4881 | png_write_destroy() do not actually free the memory that libpng | ||
4882 | allocated for these structs, but just reset the data structures, so they | ||
4883 | can be used instead of png_destroy_read_struct() and | ||
4884 | png_destroy_write_struct() if you feel there is too much system overhead | ||
4885 | allocating and freeing the png_struct for each image read. | ||
4886 | |||
4887 | Setting the error callbacks via png_set_message_fn() before | ||
4888 | png_read_init() as was suggested in libpng-0.88 is no longer supported | ||
4889 | because this caused applications that do not use custom error functions | ||
4890 | to fail if the png_ptr was not initialized to zero. It is still possible | ||
4891 | to set the error callbacks AFTER png_read_init(), or to change them with | ||
4892 | png_set_error_fn(), which is essentially the same function, but with a new | ||
4893 | name to force compilation errors with applications that try to use the old | ||
4894 | method. | ||
4895 | |||
4896 | Starting with version 1.0.7, you can find out which version of the library | ||
4897 | you are using at run-time: | ||
4898 | |||
4899 | png_uint_32 libpng_vn = png_access_version_number(); | ||
4900 | |||
4901 | The number libpng_vn is constructed from the major version, minor | ||
4902 | version with leading zero, and release number with leading zero, | ||
4903 | (e.g., libpng_vn for version 1.0.7 is 10007). | ||
4904 | |||
4905 | Note that this function does not take a png_ptr, so you can call it | ||
4906 | before you've created one. | ||
4907 | |||
4908 | You can also check which version of png.h you used when compiling your | ||
4909 | application: | ||
4910 | |||
4911 | png_uint_32 application_vn = PNG_LIBPNG_VER; | ||
4912 | |||
4913 | .SH VIII. Changes to Libpng from version 1.0.x to 1.2.x | ||
4914 | |||
4915 | Support for user memory management was enabled by default. To | ||
4916 | accomplish this, the functions png_create_read_struct_2(), | ||
4917 | png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(), | ||
4918 | png_malloc_default(), and png_free_default() were added. | ||
4919 | |||
4920 | Support for the iTXt chunk has been enabled by default as of | ||
4921 | version 1.2.41. | ||
4922 | |||
4923 | Support for certain MNG features was enabled. | ||
4924 | |||
4925 | Support for numbered error messages was added. However, we never got | ||
4926 | around to actually numbering the error messages. The function | ||
4927 | png_set_strip_error_numbers() was added (Note: the prototype for this | ||
4928 | function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE | ||
4929 | builds of libpng-1.2.15. It was restored in libpng-1.2.36). | ||
4930 | |||
4931 | The png_malloc_warn() function was added at libpng-1.2.3. This issues | ||
4932 | a png_warning and returns NULL instead of aborting when it fails to | ||
4933 | acquire the requested memory allocation. | ||
4934 | |||
4935 | Support for setting user limits on image width and height was enabled | ||
4936 | by default. The functions png_set_user_limits(), png_get_user_width_max(), | ||
4937 | and png_get_user_height_max() were added at libpng-1.2.6. | ||
4938 | |||
4939 | The png_set_add_alpha() function was added at libpng-1.2.7. | ||
4940 | |||
4941 | The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9. | ||
4942 | Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the | ||
4943 | tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is | ||
4944 | deprecated. | ||
4945 | |||
4946 | A number of macro definitions in support of runtime selection of | ||
4947 | assembler code features (especially Intel MMX code support) were | ||
4948 | added at libpng-1.2.0: | ||
4949 | |||
4950 | PNG_ASM_FLAG_MMX_SUPPORT_COMPILED | ||
4951 | PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU | ||
4952 | PNG_ASM_FLAG_MMX_READ_COMBINE_ROW | ||
4953 | PNG_ASM_FLAG_MMX_READ_INTERLACE | ||
4954 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB | ||
4955 | PNG_ASM_FLAG_MMX_READ_FILTER_UP | ||
4956 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG | ||
4957 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH | ||
4958 | PNG_ASM_FLAGS_INITIALIZED | ||
4959 | PNG_MMX_READ_FLAGS | ||
4960 | PNG_MMX_FLAGS | ||
4961 | PNG_MMX_WRITE_FLAGS | ||
4962 | PNG_MMX_FLAGS | ||
4963 | |||
4964 | We added the following functions in support of runtime | ||
4965 | selection of assembler code features: | ||
4966 | |||
4967 | png_get_mmx_flagmask() | ||
4968 | png_set_mmx_thresholds() | ||
4969 | png_get_asm_flags() | ||
4970 | png_get_mmx_bitdepth_threshold() | ||
4971 | png_get_mmx_rowbytes_threshold() | ||
4972 | png_set_asm_flags() | ||
4973 | |||
4974 | We replaced all of these functions with simple stubs in libpng-1.2.20, | ||
4975 | when the Intel assembler code was removed due to a licensing issue. | ||
4976 | |||
4977 | These macros are deprecated: | ||
4978 | |||
4979 | PNG_READ_TRANSFORMS_NOT_SUPPORTED | ||
4980 | PNG_PROGRESSIVE_READ_NOT_SUPPORTED | ||
4981 | PNG_NO_SEQUENTIAL_READ_SUPPORTED | ||
4982 | PNG_WRITE_TRANSFORMS_NOT_SUPPORTED | ||
4983 | PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED | ||
4984 | PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED | ||
4985 | |||
4986 | They have been replaced, respectively, by: | ||
4987 | |||
4988 | PNG_NO_READ_TRANSFORMS | ||
4989 | PNG_NO_PROGRESSIVE_READ | ||
4990 | PNG_NO_SEQUENTIAL_READ | ||
4991 | PNG_NO_WRITE_TRANSFORMS | ||
4992 | PNG_NO_READ_ANCILLARY_CHUNKS | ||
4993 | PNG_NO_WRITE_ANCILLARY_CHUNKS | ||
4994 | |||
4995 | PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been | ||
4996 | deprecated since libpng-1.0.16 and libpng-1.2.6. | ||
4997 | |||
4998 | The function | ||
4999 | png_check_sig(sig, num) | ||
5000 | was replaced with | ||
5001 | !png_sig_cmp(sig, 0, num) | ||
5002 | It has been deprecated since libpng-0.90. | ||
5003 | |||
5004 | The function | ||
5005 | png_set_gray_1_2_4_to_8() | ||
5006 | which also expands tRNS to alpha was replaced with | ||
5007 | png_set_expand_gray_1_2_4_to_8() | ||
5008 | which does not. It has been deprecated since libpng-1.0.18 and 1.2.9. | ||
5009 | |||
5010 | .SH IX. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x | ||
5011 | |||
5012 | Private libpng prototypes and macro definitions were moved from | ||
5013 | png.h and pngconf.h into a new pngpriv.h header file. | ||
5014 | |||
5015 | Functions png_set_benign_errors(), png_benign_error(), and | ||
5016 | png_chunk_benign_error() were added. | ||
5017 | |||
5018 | Support for setting the maximum amount of memory that the application | ||
5019 | will allocate for reading chunks was added, as a security measure. | ||
5020 | The functions png_set_chunk_cache_max() and png_get_chunk_cache_max() | ||
5021 | were added to the library. | ||
5022 | |||
5023 | We implemented support for I/O states by adding png_ptr member io_state | ||
5024 | and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c | ||
5025 | |||
5026 | We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level | ||
5027 | input transforms. | ||
5028 | |||
5029 | Checking for and reporting of errors in the IHDR chunk is more thorough. | ||
5030 | |||
5031 | Support for global arrays was removed, to improve thread safety. | ||
5032 | |||
5033 | Some obsolete/deprecated macros and functions have been removed. | ||
5034 | |||
5035 | Typecasted NULL definitions such as | ||
5036 | #define png_voidp_NULL (png_voidp)NULL | ||
5037 | were eliminated. If you used these in your application, just use | ||
5038 | NULL instead. | ||
5039 | |||
5040 | The png_struct and info_struct members "trans" and "trans_values" were | ||
5041 | changed to "trans_alpha" and "trans_color", respectively. | ||
5042 | |||
5043 | The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles | ||
5044 | were removed. | ||
5045 | |||
5046 | The PNG_1_0_X and PNG_1_2_X macros were eliminated. | ||
5047 | |||
5048 | The PNG_LEGACY_SUPPORTED macro was eliminated. | ||
5049 | |||
5050 | Many WIN32_WCE #ifdefs were removed. | ||
5051 | |||
5052 | The functions png_read_init(info_ptr), png_write_init(info_ptr), | ||
5053 | png_info_init(info_ptr), png_read_destroy(), and png_write_destroy() | ||
5054 | have been removed. They have been deprecated since libpng-0.95. | ||
5055 | |||
5056 | The png_permit_empty_plte() was removed. It has been deprecated | ||
5057 | since libpng-1.0.9. Use png_permit_mng_features() instead. | ||
5058 | |||
5059 | We removed the obsolete stub functions png_get_mmx_flagmask(), | ||
5060 | png_set_mmx_thresholds(), png_get_asm_flags(), | ||
5061 | png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(), | ||
5062 | png_set_asm_flags(), and png_mmx_supported() | ||
5063 | |||
5064 | We removed the obsolete png_check_sig(), png_memcpy_check(), and | ||
5065 | png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(), | ||
5066 | and memset(), respectively. | ||
5067 | |||
5068 | The function png_set_gray_1_2_4_to_8() was removed. It has been | ||
5069 | deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with | ||
5070 | png_set_expand_gray_1_2_4_to_8() because the former function also | ||
5071 | expanded any tRNS chunk to an alpha channel. | ||
5072 | |||
5073 | Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32 | ||
5074 | were added and are used by default instead of the corresponding | ||
5075 | functions. Unfortunately, | ||
5076 | from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the | ||
5077 | function) incorrectly returned a value of type png_uint_32. | ||
5078 | |||
5079 | We changed the prototype for png_malloc() from | ||
5080 | png_malloc(png_structp png_ptr, png_uint_32 size) | ||
5081 | to | ||
5082 | png_malloc(png_structp png_ptr, png_alloc_size_t size) | ||
5083 | |||
5084 | This also applies to the prototype for the user replacement malloc_fn(). | ||
5085 | |||
5086 | The png_calloc() function was added and is used in place of | ||
5087 | of "png_malloc(); memset();" except in the case in png_read_png() | ||
5088 | where the array consists of pointers; in this case a "for" loop is used | ||
5089 | after the png_malloc() to set the pointers to NULL, to give robust. | ||
5090 | behavior in case the application runs out of memory part-way through | ||
5091 | the process. | ||
5092 | |||
5093 | We changed the prototypes of png_get_compression_buffer_size() and | ||
5094 | png_set_compression_buffer_size() to work with png_size_t instead of | ||
5095 | png_uint_32. | ||
5096 | |||
5097 | Support for numbered error messages was removed by default, since we | ||
5098 | never got around to actually numbering the error messages. The function | ||
5099 | png_set_strip_error_numbers() was removed from the library by default. | ||
5100 | |||
5101 | The png_zalloc() and png_zfree() functions are no longer exported. | ||
5102 | The png_zalloc() function no longer zeroes out the memory that it | ||
5103 | allocates. | ||
5104 | |||
5105 | Support for dithering was disabled by default in libpng-1.4.0, because | ||
5106 | it has not been well tested and doesn't actually "dither". | ||
5107 | The code was not | ||
5108 | removed, however, and could be enabled by building libpng with | ||
5109 | PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support | ||
5110 | was reenabled, but the function was renamed png_set_quantize() to | ||
5111 | reflect more accurately what it actually does. At the same time, | ||
5112 | the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to | ||
5113 | PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED | ||
5114 | was renamed to PNG_READ_QUANTIZE_SUPPORTED. | ||
5115 | |||
5116 | We removed the trailing '.' from the warning and error messages. | ||
5117 | |||
5118 | .SH X. Changes to Libpng from version 1.4.x to 1.5.x | ||
5119 | |||
5120 | From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the | ||
5121 | function) incorrectly returned a value of type png_uint_32. | ||
5122 | |||
5123 | A. Changes that affect users of libpng | ||
5124 | |||
5125 | There are no substantial API changes between the non-deprecated parts of | ||
5126 | the 1.4.5 API and the 1.5.0 API, however the ability to directly access | ||
5127 | the main libpng control structures, png_struct and png_info, deprecated | ||
5128 | in earlier versions of libpng, has been completely removed from | ||
5129 | libpng 1.5. | ||
5130 | |||
5131 | We no longer include zlib.h in png.h. Applications that need access | ||
5132 | to information in zlib.h will need to add the '#include "zlib.h"' | ||
5133 | directive. It does not matter whether it is placed prior to or after | ||
5134 | the '"#include png.h"' directive. | ||
5135 | |||
5136 | We moved the png_strcpy(), png_strncpy(), png_strlen(), png_memcpy(), | ||
5137 | png_memcmp(), png_sprintf, and png_memcpy() macros into a private | ||
5138 | header file (pngpriv.h) that is not accessible to applications. | ||
5139 | |||
5140 | In png_get_iCCP, the type of "profile" was changed from png_charpp | ||
5141 | to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep. | ||
5142 | |||
5143 | There are changes of form in png.h, including new and changed macros to | ||
5144 | declare parts of the API. Some API functions with arguments that are | ||
5145 | pointers to data not modified within the function have been corrected to | ||
5146 | declare these arguments with PNG_CONST. | ||
5147 | |||
5148 | Much of the internal use of C macros to control the library build has also | ||
5149 | changed and some of this is visible in the exported header files, in | ||
5150 | particular the use of macros to control data and API elements visible | ||
5151 | during application compilation may require significant revision to | ||
5152 | application code. (It is extremely rare for an application to do this.) | ||
5153 | |||
5154 | Any program that compiled against libpng 1.4 and did not use deprecated | ||
5155 | features or access internal library structures should compile and work | ||
5156 | against libpng 1.5, except for the change in the prototype for | ||
5157 | png_get_iCCP() and png_set_iCCP() API functions mentioned above. | ||
5158 | |||
5159 | libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of | ||
5160 | interlaced images. The macros return the number of rows and columns in | ||
5161 | each pass and information that can be used to de-interlace and (if | ||
5162 | absolutely necessary) interlace an image. | ||
5163 | |||
5164 | libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls | ||
5165 | the application-provided png_longjmp_ptr on the internal, but application | ||
5166 | initialized, longjmp buffer. It is provided as a convenience to avoid | ||
5167 | the need to use the png_jmpbuf macro, which had the unnecessary side | ||
5168 | effect of resetting the internal png_longjmp_ptr value. | ||
5169 | |||
5170 | libpng 1.5.0 includes a complete fixed point API. By default this is | ||
5171 | present along with the corresponding floating point API. In general the | ||
5172 | fixed point API is faster and smaller than the floating point one because | ||
5173 | the PNG file format used fixed point, not floating point. This applies | ||
5174 | even if the library uses floating point in internal calculations. A new | ||
5175 | macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library | ||
5176 | uses floating point arithmetic (the default) or fixed point arithmetic | ||
5177 | internally for performance critical calculations such as gamma correction. | ||
5178 | In some cases, the gamma calculations may produce slightly different | ||
5179 | results. This has changed the results in png_rgb_to_gray and in alpha | ||
5180 | composition (png_set_background for example). This applies even if the | ||
5181 | original image was already linear (gamma == 1.0) and, therefore, it is | ||
5182 | not necessary to linearize the image. This is because libpng has *not* | ||
5183 | been changed to optimize that case correctly, yet. | ||
5184 | |||
5185 | Fixed point support for the sCAL chunk comes with an important caveat; | ||
5186 | the sCAL specification uses a decimal encoding of floating point values | ||
5187 | and the accuracy of PNG fixed point values is insufficient for | ||
5188 | representation of these values. Consequently a "string" API | ||
5189 | (png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading | ||
5190 | arbitrary sCAL chunks in the absence of either the floating point API or | ||
5191 | internal floating point calculations. | ||
5192 | |||
5193 | Applications no longer need to include the optional distribution header | ||
5194 | file pngusr.h or define the corresponding macros during application | ||
5195 | build in order to see the correct variant of the libpng API. From 1.5.0 | ||
5196 | application code can check for the corresponding _SUPPORTED macro: | ||
5197 | |||
5198 | #ifdef PNG_INCH_CONVERSIONS_SUPPORTED | ||
5199 | /* code that uses the inch conversion APIs. */ | ||
5200 | #endif | ||
5201 | |||
5202 | This macro will only be defined if the inch conversion functions have been | ||
5203 | compiled into libpng. The full set of macros, and whether or not support | ||
5204 | has been compiled in, are available in the header file pnglibconf.h. | ||
5205 | This header file is specific to the libpng build. Notice that prior to | ||
5206 | 1.5.0 the _SUPPORTED macros would always have the default definition unless | ||
5207 | reset by pngusr.h or by explicit settings on the compiler command line. | ||
5208 | These settings may produce compiler warnings or errors in 1.5.0 because | ||
5209 | of macro redefinition. | ||
5210 | |||
5211 | From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the | ||
5212 | function) incorrectly returned a value of type png_uint_32. libpng 1.5.0 | ||
5213 | is consistent with the implementation in 1.4.5 and 1.2.x (where the macro | ||
5214 | did not exist.) | ||
5215 | |||
5216 | Applications can now choose whether to use these macros or to call the | ||
5217 | corresponding function by defining PNG_USE_READ_MACROS or | ||
5218 | PNG_NO_USE_READ_MACROS before including png.h. Notice that this is | ||
5219 | only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0 | ||
5220 | will lead to a link failure. | ||
5221 | |||
5222 | Prior to libpng-1.5.4, the zlib compressor used the same set of parameters | ||
5223 | when compressing the IDAT data and textual data such as zTXt and iCCP. | ||
5224 | In libpng-1.5.4 we reinitialized the zlib stream for each type of data. | ||
5225 | We added five png_set_text_*() functions for setting the parameters to | ||
5226 | use with textual data. | ||
5227 | |||
5228 | Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED | ||
5229 | option was off by default, and slightly inaccurate scaling occurred. | ||
5230 | This option can no longer be turned off, and the choice of accurate | ||
5231 | or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8() | ||
5232 | API for accurate scaling or the old png_set_strip_16_to_8() API for simple | ||
5233 | chopping. | ||
5234 | |||
5235 | Prior to libpng-1.5.4, the png_set_user_limits() function could only be | ||
5236 | used to reduce the width and height limits from the value of | ||
5237 | PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said | ||
5238 | that it could be used to override them. Now this function will reduce or | ||
5239 | increase the limits. | ||
5240 | |||
5241 | B. Changes to the build and configuration of libpng | ||
5242 | |||
5243 | Details of internal changes to the library code can be found in the CHANGES | ||
5244 | file and in the GIT repository logs. These will be of no concern to the vast | ||
5245 | majority of library users or builders, however the few who configure libpng | ||
5246 | to a non-default feature set may need to change how this is done. | ||
5247 | |||
5248 | There should be no need for library builders to alter build scripts if | ||
5249 | these use the distributed build support - configure or the makefiles - | ||
5250 | however users of the makefiles may care to update their build scripts | ||
5251 | to build pnglibconf.h where the corresponding makefile does not do so. | ||
5252 | |||
5253 | Building libpng with a non-default configuration has changed completely. | ||
5254 | The old method using pngusr.h should still work correctly even though the | ||
5255 | way pngusr.h is used in the build has been changed; however, library | ||
5256 | builders will probably want to examine the changes to take advantage of | ||
5257 | new capabilities and to simplify their build system. | ||
5258 | |||
5259 | B.1 Specific changes to library configuration capabilities | ||
5260 | |||
5261 | The library now supports a complete fixed point implementation and can | ||
5262 | thus be used on systems that have no floating point support or very | ||
5263 | limited or slow support. Previously gamma correction, an essential part | ||
5264 | of complete PNG support, required reasonably fast floating point. | ||
5265 | |||
5266 | As part of this the choice of internal implementation has been made | ||
5267 | independent of the choice of fixed versus floating point APIs and all the | ||
5268 | missing fixed point APIs have been implemented. | ||
5269 | |||
5270 | The exact mechanism used to control attributes of API functions has | ||
5271 | changed. A single set of operating system independent macro definitions | ||
5272 | is used and operating system specific directives are defined in | ||
5273 | pnglibconf.h | ||
5274 | |||
5275 | As part of this the mechanism used to choose procedure call standards on | ||
5276 | those systems that allow a choice has been changed. At present this only | ||
5277 | affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems | ||
5278 | running on Intel processors. As before, PNGAPI is defined where required | ||
5279 | to control the exported API functions; however, two new macros, PNGCBAPI | ||
5280 | and PNGCAPI, are used instead for callback functions (PNGCBAPI) and | ||
5281 | (PNGCAPI) for functions that must match a C library prototype (currently | ||
5282 | only png_longjmp_ptr, which must match the C longjmp function.) The new | ||
5283 | approach is documented in pngconf.h | ||
5284 | |||
5285 | Despite these changes, libpng 1.5.0 only supports the native C function | ||
5286 | calling standard on those platforms tested so far (__cdecl on Microsoft | ||
5287 | Windows). This is because the support requirements for alternative | ||
5288 | calling conventions seem to no longer exist. Developers who find it | ||
5289 | necessary to set PNG_API_RULE to 1 should advise the mailing list | ||
5290 | (png-mng-implement) of this and library builders who use Openwatcom and | ||
5291 | therefore set PNG_API_RULE to 2 should also contact the mailing list. | ||
5292 | |||
5293 | A new test program, pngvalid, is provided in addition to pngtest. | ||
5294 | pngvalid validates the arithmetic accuracy of the gamma correction | ||
5295 | calculations and includes a number of validations of the file format. | ||
5296 | A subset of the full range of tests is run when "make check" is done | ||
5297 | (in the 'configure' build.) pngvalid also allows total allocated memory | ||
5298 | usage to be evaluated and performs additional memory overwrite validation. | ||
5299 | |||
5300 | Many changes to individual feature macros have been made. The following | ||
5301 | are the changes most likely to be noticed by library builders who | ||
5302 | configure libpng: | ||
5303 | |||
5304 | 1) All feature macros now have consistent naming: | ||
5305 | |||
5306 | #define PNG_NO_feature turns the feature off | ||
5307 | #define PNG_feature_SUPPORTED turns the feature on | ||
5308 | |||
5309 | pnglibconf.h contains one line for each feature macro which is either: | ||
5310 | |||
5311 | #define PNG_feature_SUPPORTED | ||
5312 | |||
5313 | if the feature is supported or: | ||
5314 | |||
5315 | /*#undef PNG_feature_SUPPORTED*/ | ||
5316 | |||
5317 | if it is not. Library code consistently checks for the 'SUPPORTED' macro. | ||
5318 | It does not, and libpng applications should not, check for the 'NO' macro | ||
5319 | which will not normally be defined even if the feature is not supported. | ||
5320 | The 'NO' macros are only used internally for setting or not setting the | ||
5321 | corresponding 'SUPPORTED' macros. | ||
5322 | |||
5323 | Compatibility with the old names is provided as follows: | ||
5324 | |||
5325 | PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED | ||
5326 | |||
5327 | And the following definitions disable the corresponding feature: | ||
5328 | |||
5329 | PNG_SETJMP_NOT_SUPPORTED disables SETJMP | ||
5330 | PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS | ||
5331 | PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV | ||
5332 | PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS | ||
5333 | PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS | ||
5334 | PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS | ||
5335 | |||
5336 | Library builders should remove use of the above, inconsistent, names. | ||
5337 | |||
5338 | 2) Warning and error message formatting was previously conditional on | ||
5339 | the STDIO feature. The library has been changed to use the | ||
5340 | CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled | ||
5341 | the library no longer uses the printf(3) functions, even though the | ||
5342 | default read/write implementations use (FILE) style stdio.h functions. | ||
5343 | |||
5344 | 3) Three feature macros now control the fixed/floating point decisions: | ||
5345 | |||
5346 | PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs | ||
5347 | |||
5348 | PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in | ||
5349 | practice these are normally required internally anyway (because the PNG | ||
5350 | file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT | ||
5351 | merely stops the function from being exported. | ||
5352 | |||
5353 | PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating | ||
5354 | point implementation or the fixed point one. Typically the fixed point | ||
5355 | implementation is larger and slower than the floating point implementation | ||
5356 | on a system that supports floating point, however it may be faster on a | ||
5357 | system which lacks floating point hardware and therefore uses a software | ||
5358 | emulation. | ||
5359 | |||
5360 | 4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the | ||
5361 | functions to read and write ints to be disabled independently of | ||
5362 | PNG_USE_READ_MACROS, which allows libpng to be built with the functions | ||
5363 | even though the default is to use the macros - this allows applications | ||
5364 | to choose at app buildtime whether or not to use macros (previously | ||
5365 | impossible because the functions weren't in the default build.) | ||
5366 | |||
5367 | B.2 Changes to the configuration mechanism | ||
5368 | |||
5369 | Prior to libpng-1.5.0 library builders who needed to configure libpng | ||
5370 | had either to modify the exported pngconf.h header file to add system | ||
5371 | specific configuration or had to write feature selection macros into | ||
5372 | pngusr.h and cause this to be included into pngconf.h by defining | ||
5373 | PNG_USER_CONFIG. The latter mechanism had the disadvantage that an | ||
5374 | application built without PNG_USER_CONFIG defined would see the | ||
5375 | unmodified, default, libpng API and thus would probably fail to link. | ||
5376 | |||
5377 | These mechanisms still work in the configure build and in any makefile | ||
5378 | build that builds pnglibconf.h, although the feature selection macros | ||
5379 | have changed somewhat as described above. In 1.5.0, however, pngusr.h is | ||
5380 | processed only once, when the exported header file pnglibconf.h is built. | ||
5381 | pngconf.h no longer includes pngusr.h, therefore pngusr.h is ignored after the | ||
5382 | build of pnglibconf.h and it is never included in an application build. | ||
5383 | |||
5384 | The rarely used alternative of adding a list of feature macros to the | ||
5385 | CFLAGS setting in the build also still works, however the macros will be | ||
5386 | copied to pnglibconf.h and this may produce macro redefinition warnings | ||
5387 | when the individual C files are compiled. | ||
5388 | |||
5389 | All configuration now only works if pnglibconf.h is built from | ||
5390 | scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan | ||
5391 | (the original author of awk) maintains C source code of that awk and this | ||
5392 | and all known later implementations (often called by subtly different | ||
5393 | names - nawk and gawk for example) are adequate to build pnglibconf.h. | ||
5394 | The Sun Microsystems (now Oracle) program 'awk' is an earlier version | ||
5395 | and does not work; this may also apply to other systems that have a | ||
5396 | functioning awk called 'nawk'. | ||
5397 | |||
5398 | Configuration options are now documented in scripts/pnglibconf.dfa. This | ||
5399 | file also includes dependency information that ensures a configuration is | ||
5400 | consistent; that is, if a feature is switched off dependent features are | ||
5401 | also removed. As a recommended alternative to using feature macros in | ||
5402 | pngusr.h a system builder may also define equivalent options in pngusr.dfa | ||
5403 | (or, indeed, any file) and add that to the configuration by setting | ||
5404 | DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate | ||
5405 | how to do this, and a case where pngusr.h is still required. | ||
5406 | |||
5407 | .SH XI. Detecting libpng | ||
5408 | |||
5409 | The png_get_io_ptr() function has been present since libpng-0.88, has never | ||
5410 | changed, and is unaffected by conditional compilation macros. It is the | ||
5411 | best choice for use in configure scripts for detecting the presence of any | ||
5412 | libpng version since 0.88. In an autoconf "configure.in" you could use | ||
5413 | |||
5414 | AC_CHECK_LIB(png, png_get_io_ptr, ... | ||
5415 | |||
5416 | .SH XII. Source code repository | ||
5417 | |||
5418 | Since about February 2009, version 1.2.34, libpng has been under "git" source | ||
5419 | control. The git repository was built from old libpng-x.y.z.tar.gz files | ||
5420 | going back to version 0.70. You can access the git repository (read only) | ||
5421 | at | ||
5422 | |||
5423 | git://libpng.git.sourceforge.net/gitroot/libpng | ||
5424 | |||
5425 | or you can browse it via "gitweb" at | ||
5426 | |||
5427 | http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng | ||
5428 | |||
5429 | Patches can be sent to glennrp at users.sourceforge.net or to | ||
5430 | png-mng-implement at lists.sourceforge.net or you can upload them to | ||
5431 | the libpng bug tracker at | ||
5432 | |||
5433 | http://libpng.sourceforge.net | ||
5434 | |||
5435 | We also accept patches built from the tar or zip distributions, and | ||
5436 | simple verbal discriptions of bug fixes, reported either to the | ||
5437 | SourceForge bug tracker, to the png-mng-implement at lists.sf.net | ||
5438 | mailing list, or directly to glennrp. | ||
5439 | |||
5440 | .SH XIII. Coding style | ||
5441 | |||
5442 | Our coding style is similar to the "Allman" style, with curly | ||
5443 | braces on separate lines: | ||
5444 | |||
5445 | if (condition) | ||
5446 | { | ||
5447 | action; | ||
5448 | } | ||
5449 | |||
5450 | else if (another condition) | ||
5451 | { | ||
5452 | another action; | ||
5453 | } | ||
5454 | |||
5455 | The braces can be omitted from simple one-line actions: | ||
5456 | |||
5457 | if (condition) | ||
5458 | return (0); | ||
5459 | |||
5460 | We use 3-space indentation, except for continued statements which | ||
5461 | are usually indented the same as the first line of the statement | ||
5462 | plus four more spaces. | ||
5463 | |||
5464 | For macro definitions we use 2-space indentation, always leaving the "#" | ||
5465 | in the first column. | ||
5466 | |||
5467 | #ifndef PNG_NO_FEATURE | ||
5468 | # ifndef PNG_FEATURE_SUPPORTED | ||
5469 | # define PNG_FEATURE_SUPPORTED | ||
5470 | # endif | ||
5471 | #endif | ||
5472 | |||
5473 | Comments appear with the leading "/*" at the same indentation as | ||
5474 | the statement that follows the comment: | ||
5475 | |||
5476 | /* Single-line comment */ | ||
5477 | statement; | ||
5478 | |||
5479 | /* This is a multiple-line | ||
5480 | * comment. | ||
5481 | */ | ||
5482 | statement; | ||
5483 | |||
5484 | Very short comments can be placed after the end of the statement | ||
5485 | to which they pertain: | ||
5486 | |||
5487 | statement; /* comment */ | ||
5488 | |||
5489 | We don't use C++ style ("//") comments. We have, however, | ||
5490 | used them in the past in some now-abandoned MMX assembler | ||
5491 | code. | ||
5492 | |||
5493 | Functions and their curly braces are not indented, and | ||
5494 | exported functions are marked with PNGAPI: | ||
5495 | |||
5496 | /* This is a public function that is visible to | ||
5497 | * application programmers. It does thus-and-so. | ||
5498 | */ | ||
5499 | void PNGAPI | ||
5500 | png_exported_function(png_ptr, png_info, foo) | ||
5501 | { | ||
5502 | body; | ||
5503 | } | ||
5504 | |||
5505 | The prototypes for all exported functions appear in png.h, | ||
5506 | above the comment that says | ||
5507 | |||
5508 | /* Maintainer: Put new public prototypes here ... */ | ||
5509 | |||
5510 | We mark all non-exported functions with "/* PRIVATE */"": | ||
5511 | |||
5512 | void /* PRIVATE */ | ||
5513 | png_non_exported_function(png_ptr, png_info, foo) | ||
5514 | { | ||
5515 | body; | ||
5516 | } | ||
5517 | |||
5518 | The prototypes for non-exported functions (except for those in | ||
5519 | pngtest) appear in | ||
5520 | pngpriv.h | ||
5521 | above the comment that says | ||
5522 | |||
5523 | /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */ | ||
5524 | |||
5525 | To avoid polluting the global namespace, the names of all exported | ||
5526 | functions and variables begin with "png_", and all publicly visible C | ||
5527 | preprocessor macros begin with "PNG_". We request that applications that | ||
5528 | use libpng *not* begin any of their own symbols with either of these strings. | ||
5529 | |||
5530 | We put a space after each comma and after each semicolon | ||
5531 | in "for" statements, and we put spaces before and after each | ||
5532 | C binary operator and after "for" or "while", and before | ||
5533 | "?". We don't put a space between a typecast and the expression | ||
5534 | being cast, nor do we put one between a function name and the | ||
5535 | left parenthesis that follows it: | ||
5536 | |||
5537 | for (i = 2; i > 0; --i) | ||
5538 | y[i] = a(x) + (int)b; | ||
5539 | |||
5540 | We prefer #ifdef and #ifndef to #if defined() and if !defined() | ||
5541 | when there is only one macro being tested. | ||
5542 | |||
5543 | We prefer to express integers that are used as bit masks in hex format, | ||
5544 | with an even number of lower-case hex digits (e.g., 0x00, 0xff, 0x0100). | ||
5545 | |||
5546 | We do not use the TAB character for indentation in the C sources. | ||
5547 | |||
5548 | Lines do not exceed 80 characters. | ||
5549 | |||
5550 | Other rules can be inferred by inspecting the libpng source. | ||
5551 | |||
5552 | .SH XIV. Y2K Compliance in libpng | ||
5553 | |||
5554 | February 18, 2012 | ||
5555 | |||
5556 | Since the PNG Development group is an ad-hoc body, we can't make | ||
5557 | an official declaration. | ||
5558 | |||
5559 | This is your unofficial assurance that libpng from version 0.71 and | ||
5560 | upward through 1.5.9 are Y2K compliant. It is my belief that earlier | ||
5561 | versions were also Y2K compliant. | ||
5562 | |||
5563 | Libpng only has three year fields. One is a 2-byte unsigned integer that | ||
5564 | will hold years up to 65535. The other two hold the date in text | ||
5565 | format, and will hold years up to 9999. | ||
5566 | |||
5567 | The integer is | ||
5568 | "png_uint_16 year" in png_time_struct. | ||
5569 | |||
5570 | The strings are | ||
5571 | "png_charp time_buffer" in png_struct and | ||
5572 | "near_time_buffer", which is a local character string in png.c. | ||
5573 | |||
5574 | There are seven time-related functions: | ||
5575 | |||
5576 | png_convert_to_rfc_1123() in png.c | ||
5577 | (formerly png_convert_to_rfc_1152() in error) | ||
5578 | png_convert_from_struct_tm() in pngwrite.c, called | ||
5579 | in pngwrite.c | ||
5580 | png_convert_from_time_t() in pngwrite.c | ||
5581 | png_get_tIME() in pngget.c | ||
5582 | png_handle_tIME() in pngrutil.c, called in pngread.c | ||
5583 | png_set_tIME() in pngset.c | ||
5584 | png_write_tIME() in pngwutil.c, called in pngwrite.c | ||
5585 | |||
5586 | All appear to handle dates properly in a Y2K environment. The | ||
5587 | png_convert_from_time_t() function calls gmtime() to convert from system | ||
5588 | clock time, which returns (year - 1900), which we properly convert to | ||
5589 | the full 4-digit year. There is a possibility that applications using | ||
5590 | libpng are not passing 4-digit years into the png_convert_to_rfc_1123() | ||
5591 | function, or that they are incorrectly passing only a 2-digit year | ||
5592 | instead of "year - 1900" into the png_convert_from_struct_tm() function, | ||
5593 | but this is not under our control. The libpng documentation has always | ||
5594 | stated that it works with 4-digit years, and the APIs have been | ||
5595 | documented as such. | ||
5596 | |||
5597 | The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned | ||
5598 | integer to hold the year, and can hold years as large as 65535. | ||
5599 | |||
5600 | zlib, upon which libpng depends, is also Y2K compliant. It contains | ||
5601 | no date-related code. | ||
5602 | |||
5603 | |||
5604 | Glenn Randers-Pehrson | ||
5605 | libpng maintainer | ||
5606 | PNG Development Group | ||
5607 | |||
5608 | .SH NOTE | ||
5609 | |||
5610 | Note about libpng version numbers: | ||
5611 | |||
5612 | Due to various miscommunications, unforeseen code incompatibilities | ||
5613 | and occasional factors outside the authors' control, version numbering | ||
5614 | on the library has not always been consistent and straightforward. | ||
5615 | The following table summarizes matters since version 0.89c, which was | ||
5616 | the first widely used release: | ||
5617 | |||
5618 | source png.h png.h shared-lib | ||
5619 | version string int version | ||
5620 | ------- ------ ----- ---------- | ||
5621 | 0.89c ("beta 3") 0.89 89 1.0.89 | ||
5622 | 0.90 ("beta 4") 0.90 90 0.90 | ||
5623 | 0.95 ("beta 5") 0.95 95 0.95 | ||
5624 | 0.96 ("beta 6") 0.96 96 0.96 | ||
5625 | 0.97b ("beta 7") 1.00.97 97 1.0.1 | ||
5626 | 0.97c 0.97 97 2.0.97 | ||
5627 | 0.98 0.98 98 2.0.98 | ||
5628 | 0.99 0.99 98 2.0.99 | ||
5629 | 0.99a-m 0.99 99 2.0.99 | ||
5630 | 1.00 1.00 100 2.1.0 | ||
5631 | 1.0.0 1.0.0 100 2.1.0 | ||
5632 | 1.0.0 (from here on, the 100 2.1.0 | ||
5633 | 1.0.1 png.h string is 10001 2.1.0 | ||
5634 | 1.0.1a-e identical to the 10002 from here on, the | ||
5635 | 1.0.2 source version) 10002 shared library is 2.V | ||
5636 | 1.0.2a-b 10003 where V is the source | ||
5637 | 1.0.1 10001 code version except as | ||
5638 | 1.0.1a-e 10002 2.1.0.1a-e noted. | ||
5639 | 1.0.2 10002 2.1.0.2 | ||
5640 | 1.0.2a-b 10003 2.1.0.2a-b | ||
5641 | 1.0.3 10003 2.1.0.3 | ||
5642 | 1.0.3a-d 10004 2.1.0.3a-d | ||
5643 | 1.0.4 10004 2.1.0.4 | ||
5644 | 1.0.4a-f 10005 2.1.0.4a-f | ||
5645 | 1.0.5 (+ 2 patches) 10005 2.1.0.5 | ||
5646 | 1.0.5a-d 10006 2.1.0.5a-d | ||
5647 | 1.0.5e-r 10100 2.1.0.5e-r | ||
5648 | 1.0.5s-v 10006 2.1.0.5s-v | ||
5649 | 1.0.6 (+ 3 patches) 10006 2.1.0.6 | ||
5650 | 1.0.6d-g 10007 2.1.0.6d-g | ||
5651 | 1.0.6h 10007 10.6h | ||
5652 | 1.0.6i 10007 10.6i | ||
5653 | 1.0.6j 10007 2.1.0.6j | ||
5654 | 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14 | ||
5655 | 1.0.7beta15-18 1 10007 2.1.0.7beta15-18 | ||
5656 | 1.0.7rc1-2 1 10007 2.1.0.7rc1-2 | ||
5657 | 1.0.7 1 10007 2.1.0.7 | ||
5658 | 1.0.8beta1-4 1 10008 2.1.0.8beta1-4 | ||
5659 | 1.0.8rc1 1 10008 2.1.0.8rc1 | ||
5660 | 1.0.8 1 10008 2.1.0.8 | ||
5661 | 1.0.9beta1-6 1 10009 2.1.0.9beta1-6 | ||
5662 | 1.0.9rc1 1 10009 2.1.0.9rc1 | ||
5663 | 1.0.9beta7-10 1 10009 2.1.0.9beta7-10 | ||
5664 | 1.0.9rc2 1 10009 2.1.0.9rc2 | ||
5665 | 1.0.9 1 10009 2.1.0.9 | ||
5666 | 1.0.10beta1 1 10010 2.1.0.10beta1 | ||
5667 | 1.0.10rc1 1 10010 2.1.0.10rc1 | ||
5668 | 1.0.10 1 10010 2.1.0.10 | ||
5669 | 1.0.11beta1-3 1 10011 2.1.0.11beta1-3 | ||
5670 | 1.0.11rc1 1 10011 2.1.0.11rc1 | ||
5671 | 1.0.11 1 10011 2.1.0.11 | ||
5672 | 1.0.12beta1-2 2 10012 2.1.0.12beta1-2 | ||
5673 | 1.0.12rc1 2 10012 2.1.0.12rc1 | ||
5674 | 1.0.12 2 10012 2.1.0.12 | ||
5675 | 1.1.0a-f - 10100 2.1.1.0a-f abandoned | ||
5676 | 1.2.0beta1-2 2 10200 2.1.2.0beta1-2 | ||
5677 | 1.2.0beta3-5 3 10200 3.1.2.0beta3-5 | ||
5678 | 1.2.0rc1 3 10200 3.1.2.0rc1 | ||
5679 | 1.2.0 3 10200 3.1.2.0 | ||
5680 | 1.2.1beta-4 3 10201 3.1.2.1beta1-4 | ||
5681 | 1.2.1rc1-2 3 10201 3.1.2.1rc1-2 | ||
5682 | 1.2.1 3 10201 3.1.2.1 | ||
5683 | 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6 | ||
5684 | 1.0.13beta1 10 10013 10.so.0.1.0.13beta1 | ||
5685 | 1.0.13rc1 10 10013 10.so.0.1.0.13rc1 | ||
5686 | 1.2.2rc1 12 10202 12.so.0.1.2.2rc1 | ||
5687 | 1.0.13 10 10013 10.so.0.1.0.13 | ||
5688 | 1.2.2 12 10202 12.so.0.1.2.2 | ||
5689 | 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6 | ||
5690 | 1.2.3 12 10203 12.so.0.1.2.3 | ||
5691 | 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3 | ||
5692 | 1.2.4rc1 13 10204 12.so.0.1.2.4rc1 | ||
5693 | 1.0.14 10 10014 10.so.0.1.0.14 | ||
5694 | 1.2.4 13 10204 12.so.0.1.2.4 | ||
5695 | 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2 | ||
5696 | 1.0.15rc1 10 10015 10.so.0.1.0.15rc1 | ||
5697 | 1.0.15 10 10015 10.so.0.1.0.15 | ||
5698 | 1.2.5 13 10205 12.so.0.1.2.5 | ||
5699 | 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4 | ||
5700 | 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5 | ||
5701 | 1.0.16 10 10016 10.so.0.1.0.16 | ||
5702 | 1.2.6 13 10206 12.so.0.1.2.6 | ||
5703 | 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2 | ||
5704 | 1.0.17rc1 10 10017 12.so.0.1.0.17rc1 | ||
5705 | 1.2.7rc1 13 10207 12.so.0.1.2.7rc1 | ||
5706 | 1.0.17 10 10017 12.so.0.1.0.17 | ||
5707 | 1.2.7 13 10207 12.so.0.1.2.7 | ||
5708 | 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5 | ||
5709 | 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5 | ||
5710 | 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5 | ||
5711 | 1.0.18 10 10018 12.so.0.1.0.18 | ||
5712 | 1.2.8 13 10208 12.so.0.1.2.8 | ||
5713 | 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3 | ||
5714 | 1.2.9beta4-11 13 10209 12.so.0.9[.0] | ||
5715 | 1.2.9rc1 13 10209 12.so.0.9[.0] | ||
5716 | 1.2.9 13 10209 12.so.0.9[.0] | ||
5717 | 1.2.10beta1-7 13 10210 12.so.0.10[.0] | ||
5718 | 1.2.10rc1-2 13 10210 12.so.0.10[.0] | ||
5719 | 1.2.10 13 10210 12.so.0.10[.0] | ||
5720 | 1.4.0beta1-6 14 10400 14.so.0.0[.0] | ||
5721 | 1.2.11beta1-4 13 10210 12.so.0.11[.0] | ||
5722 | 1.4.0beta7-8 14 10400 14.so.0.0[.0] | ||
5723 | 1.2.11 13 10211 12.so.0.11[.0] | ||
5724 | 1.2.12 13 10212 12.so.0.12[.0] | ||
5725 | 1.4.0beta9-14 14 10400 14.so.0.0[.0] | ||
5726 | 1.2.13 13 10213 12.so.0.13[.0] | ||
5727 | 1.4.0beta15-36 14 10400 14.so.0.0[.0] | ||
5728 | 1.4.0beta37-87 14 10400 14.so.14.0[.0] | ||
5729 | 1.4.0rc01 14 10400 14.so.14.0[.0] | ||
5730 | 1.4.0beta88-109 14 10400 14.so.14.0[.0] | ||
5731 | 1.4.0rc02-08 14 10400 14.so.14.0[.0] | ||
5732 | 1.4.0 14 10400 14.so.14.0[.0] | ||
5733 | 1.4.1beta01-03 14 10401 14.so.14.1[.0] | ||
5734 | 1.4.1rc01 14 10401 14.so.14.1[.0] | ||
5735 | 1.4.1beta04-12 14 10401 14.so.14.1[.0] | ||
5736 | 1.4.1 14 10401 14.so.14.1[.0] | ||
5737 | 1.4.2 14 10402 14.so.14.2[.0] | ||
5738 | 1.4.3 14 10403 14.so.14.3[.0] | ||
5739 | 1.4.4 14 10404 14.so.14.4[.0] | ||
5740 | 1.5.0beta01-58 15 10500 15.so.15.0[.0] | ||
5741 | 1.5.0rc01-07 15 10500 15.so.15.0[.0] | ||
5742 | 1.5.0 15 10500 15.so.15.0[.0] | ||
5743 | 1.5.1beta01-11 15 10501 15.so.15.1[.0] | ||
5744 | 1.5.1rc01-02 15 10501 15.so.15.1[.0] | ||
5745 | 1.5.1 15 10501 15.so.15.1[.0] | ||
5746 | 1.5.2beta01-03 15 10502 15.so.15.2[.0] | ||
5747 | 1.5.2rc01-03 15 10502 15.so.15.2[.0] | ||
5748 | 1.5.2 15 10502 15.so.15.2[.0] | ||
5749 | 1.5.3beta01-10 15 10503 15.so.15.3[.0] | ||
5750 | 1.5.3rc01-02 15 10503 15.so.15.3[.0] | ||
5751 | 1.5.3beta11 15 10503 15.so.15.3[.0] | ||
5752 | 1.5.3 [omitted] | ||
5753 | 1.5.4beta01-08 15 10504 15.so.15.4[.0] | ||
5754 | 1.5.4rc01 15 10504 15.so.15.4[.0] | ||
5755 | 1.5.4 15 10504 15.so.15.4[.0] | ||
5756 | 1.5.5beta01-08 15 10505 15.so.15.5[.0] | ||
5757 | 1.5.5rc01 15 10505 15.so.15.5[.0] | ||
5758 | 1.5.5 15 10505 15.so.15.5[.0] | ||
5759 | 1.5.6beta01-07 15 10506 15.so.15.6[.0] | ||
5760 | 1.5.6rc01-03 15 10506 15.so.15.6[.0] | ||
5761 | 1.5.6 15 10506 15.so.15.6[.0] | ||
5762 | 1.5.7beta01-05 15 10507 15.so.15.7[.0] | ||
5763 | 1.5.7rc01-03 15 10507 15.so.15.7[.0] | ||
5764 | 1.5.7 15 10507 15.so.15.7[.0] | ||
5765 | 1.5.8beta01 15 10508 15.so.15.8[.0] | ||
5766 | 1.5.8rc01 15 10508 15.so.15.8[.0] | ||
5767 | 1.5.8 15 10508 15.so.15.8[.0] | ||
5768 | 1.5.9beta01-02 15 10509 15.so.15.9[.0] | ||
5769 | 1.5.9rc01 15 10509 15.so.15.9[.0] | ||
5770 | 1.5.9 15 10509 15.so.15.9[.0] | ||
5771 | |||
5772 | Henceforth the source version will match the shared-library minor | ||
5773 | and patch numbers; the shared-library major version number will be | ||
5774 | used for changes in backward compatibility, as it is intended. The | ||
5775 | PNG_PNGLIB_VER macro, which is not used within libpng but is available | ||
5776 | for applications, is an unsigned integer of the form xyyzz corresponding | ||
5777 | to the source version x.y.z (leading zeros in y and z). Beta versions | ||
5778 | were given the previous public release number plus a letter, until | ||
5779 | version 1.0.6j; from then on they were given the upcoming public | ||
5780 | release number plus "betaNN" or "rcN". | ||
5781 | |||
5782 | .SH "SEE ALSO" | ||
5783 | .BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5) | ||
5784 | |||
5785 | .LP | ||
5786 | .IR libpng : | ||
5787 | .IP | ||
5788 | http://libpng.sourceforge.net (follow the [DOWNLOAD] link) | ||
5789 | http://www.libpng.org/pub/png | ||
5790 | |||
5791 | .LP | ||
5792 | .IR zlib : | ||
5793 | .IP | ||
5794 | (generally) at the same location as | ||
5795 | .I libpng | ||
5796 | or at | ||
5797 | .br | ||
5798 | ftp://ftp.info-zip.org/pub/infozip/zlib | ||
5799 | |||
5800 | .LP | ||
5801 | .IR PNG specification: RFC 2083 | ||
5802 | .IP | ||
5803 | (generally) at the same location as | ||
5804 | .I libpng | ||
5805 | or at | ||
5806 | .br | ||
5807 | ftp://ds.internic.net/rfc/rfc2083.txt | ||
5808 | .br | ||
5809 | or (as a W3C Recommendation) at | ||
5810 | .br | ||
5811 | http://www.w3.org/TR/REC-png.html | ||
5812 | |||
5813 | .LP | ||
5814 | In the case of any inconsistency between the PNG specification | ||
5815 | and this library, the specification takes precedence. | ||
5816 | |||
5817 | .SH AUTHORS | ||
5818 | This man page: Glenn Randers-Pehrson | ||
5819 | <glennrp at users.sourceforge.net> | ||
5820 | |||
5821 | The contributing authors would like to thank all those who helped | ||
5822 | with testing, bug fixes, and patience. This wouldn't have been | ||
5823 | possible without all of you. | ||
5824 | |||
5825 | Thanks to Frank J. T. Wojcik for helping with the documentation. | ||
5826 | |||
5827 | Libpng version 1.5.9 - February 18, 2012: | ||
5828 | Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. | ||
5829 | Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). | ||
5830 | |||
5831 | Supported by the PNG development group | ||
5832 | .br | ||
5833 | png-mng-implement at lists.sf.net | ||
5834 | (subscription required; visit | ||
5835 | png-mng-implement at lists.sourceforge.net (subscription required; visit | ||
5836 | https://lists.sourceforge.net/lists/listinfo/png-mng-implement | ||
5837 | to subscribe). | ||
5838 | |||
5839 | .SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE: | ||
5840 | |||
5841 | (This copy of the libpng notices is provided for your convenience. In case of | ||
5842 | any discrepancy between this copy and the notices in the file png.h that is | ||
5843 | included in the libpng distribution, the latter shall prevail.) | ||
5844 | |||
5845 | If you modify libpng you may insert additional notices immediately following | ||
5846 | this sentence. | ||
5847 | |||
5848 | This code is released under the libpng license. | ||
5849 | |||
5850 | libpng versions 1.2.6, August 15, 2004, through 1.5.9, February 18, 2012, are | ||
5851 | Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are | ||
5852 | distributed according to the same disclaimer and license as libpng-1.2.5 | ||
5853 | with the following individual added to the list of Contributing Authors | ||
5854 | |||
5855 | Cosmin Truta | ||
5856 | |||
5857 | libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are | ||
5858 | Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are | ||
5859 | distributed according to the same disclaimer and license as libpng-1.0.6 | ||
5860 | with the following individuals added to the list of Contributing Authors | ||
5861 | |||
5862 | Simon-Pierre Cadieux | ||
5863 | Eric S. Raymond | ||
5864 | Gilles Vollant | ||
5865 | |||
5866 | and with the following additions to the disclaimer: | ||
5867 | |||
5868 | There is no warranty against interference with your | ||
5869 | enjoyment of the library or against infringement. | ||
5870 | There is no warranty that our efforts or the library | ||
5871 | will fulfill any of your particular purposes or needs. | ||
5872 | This library is provided with all faults, and the entire | ||
5873 | risk of satisfactory quality, performance, accuracy, and | ||
5874 | effort is with the user. | ||
5875 | |||
5876 | libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are | ||
5877 | Copyright (c) 1998, 1999 Glenn Randers-Pehrson | ||
5878 | Distributed according to the same disclaimer and license as libpng-0.96, | ||
5879 | with the following individuals added to the list of Contributing Authors: | ||
5880 | |||
5881 | Tom Lane | ||
5882 | Glenn Randers-Pehrson | ||
5883 | Willem van Schaik | ||
5884 | |||
5885 | libpng versions 0.89, June 1996, through 0.96, May 1997, are | ||
5886 | Copyright (c) 1996, 1997 Andreas Dilger | ||
5887 | Distributed according to the same disclaimer and license as libpng-0.88, | ||
5888 | with the following individuals added to the list of Contributing Authors: | ||
5889 | |||
5890 | John Bowler | ||
5891 | Kevin Bracey | ||
5892 | Sam Bushell | ||
5893 | Magnus Holmgren | ||
5894 | Greg Roelofs | ||
5895 | Tom Tanner | ||
5896 | |||
5897 | libpng versions 0.5, May 1995, through 0.88, January 1996, are | ||
5898 | Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. | ||
5899 | |||
5900 | For the purposes of this copyright and license, "Contributing Authors" | ||
5901 | is defined as the following set of individuals: | ||
5902 | |||
5903 | Andreas Dilger | ||
5904 | Dave Martindale | ||
5905 | Guy Eric Schalnat | ||
5906 | Paul Schmidt | ||
5907 | Tim Wegner | ||
5908 | |||
5909 | The PNG Reference Library is supplied "AS IS". The Contributing Authors | ||
5910 | and Group 42, Inc. disclaim all warranties, expressed or implied, | ||
5911 | including, without limitation, the warranties of merchantability and of | ||
5912 | fitness for any purpose. The Contributing Authors and Group 42, Inc. | ||
5913 | assume no liability for direct, indirect, incidental, special, exemplary, | ||
5914 | or consequential damages, which may result from the use of the PNG | ||
5915 | Reference Library, even if advised of the possibility of such damage. | ||
5916 | |||
5917 | Permission is hereby granted to use, copy, modify, and distribute this | ||
5918 | source code, or portions hereof, for any purpose, without fee, subject | ||
5919 | to the following restrictions: | ||
5920 | |||
5921 | 1. The origin of this source code must not be misrepresented. | ||
5922 | |||
5923 | 2. Altered versions must be plainly marked as such and | ||
5924 | must not be misrepresented as being the original source. | ||
5925 | |||
5926 | 3. This Copyright notice may not be removed or altered from | ||
5927 | any source or altered source distribution. | ||
5928 | |||
5929 | The Contributing Authors and Group 42, Inc. specifically permit, without | ||
5930 | fee, and encourage the use of this source code as a component to | ||
5931 | supporting the PNG file format in commercial products. If you use this | ||
5932 | source code in a product, acknowledgment is not required but would be | ||
5933 | appreciated. | ||
5934 | |||
5935 | |||
5936 | A "png_get_copyright" function is available, for convenient use in "about" | ||
5937 | boxes and the like: | ||
5938 | |||
5939 | printf("%s",png_get_copyright(NULL)); | ||
5940 | |||
5941 | Also, the PNG logo (in PNG format, of course) is supplied in the | ||
5942 | files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31). | ||
5943 | |||
5944 | Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a | ||
5945 | certification mark of the Open Source Initiative. | ||
5946 | |||
5947 | Glenn Randers-Pehrson | ||
5948 | glennrp at users.sourceforge.net | ||
5949 | February 18, 2012 | ||
5950 | |||
5951 | .\" end of man page | ||
5952 | |||