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author | David Walter Seikel | 2013-01-13 18:54:10 +1000 |
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committer | David Walter Seikel | 2013-01-13 18:54:10 +1000 |
commit | 959831f4ef5a3e797f576c3de08cd65032c997ad (patch) | |
tree | e7351908be5995f0b325b2ebeaa02d5a34b82583 /libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 | |
parent | Add info about changes to Irrlicht. (diff) | |
download | SledjHamr-959831f4ef5a3e797f576c3de08cd65032c997ad.zip SledjHamr-959831f4ef5a3e797f576c3de08cd65032c997ad.tar.gz SledjHamr-959831f4ef5a3e797f576c3de08cd65032c997ad.tar.bz2 SledjHamr-959831f4ef5a3e797f576c3de08cd65032c997ad.tar.xz |
Remove damned ancient DOS line endings from Irrlicht. Hopefully I did not go overboard.
Diffstat (limited to 'libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1')
-rw-r--r-- | libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 | 696 |
1 files changed, 348 insertions, 348 deletions
diff --git a/libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 b/libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 index 18283e5..c10f971 100644 --- a/libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 +++ b/libraries/irrlicht-1.8/source/Irrlicht/jpeglib/cjpeg.1 | |||
@@ -1,348 +1,348 @@ | |||
1 | .TH CJPEG 1 "28 August 2011" | 1 | .TH CJPEG 1 "28 August 2011" |
2 | .SH NAME | 2 | .SH NAME |
3 | cjpeg \- compress an image file to a JPEG file | 3 | cjpeg \- compress an image file to a JPEG file |
4 | .SH SYNOPSIS | 4 | .SH SYNOPSIS |
5 | .B cjpeg | 5 | .B cjpeg |
6 | [ | 6 | [ |
7 | .I options | 7 | .I options |
8 | ] | 8 | ] |
9 | [ | 9 | [ |
10 | .I filename | 10 | .I filename |
11 | ] | 11 | ] |
12 | .LP | 12 | .LP |
13 | .SH DESCRIPTION | 13 | .SH DESCRIPTION |
14 | .LP | 14 | .LP |
15 | .B cjpeg | 15 | .B cjpeg |
16 | compresses the named image file, or the standard input if no file is | 16 | compresses the named image file, or the standard input if no file is |
17 | named, and produces a JPEG/JFIF file on the standard output. | 17 | named, and produces a JPEG/JFIF file on the standard output. |
18 | The currently supported input file formats are: PPM (PBMPLUS color | 18 | The currently supported input file formats are: PPM (PBMPLUS color |
19 | format), PGM (PBMPLUS gray-scale format), BMP, Targa, and RLE (Utah Raster | 19 | format), PGM (PBMPLUS gray-scale format), BMP, Targa, and RLE (Utah Raster |
20 | Toolkit format). (RLE is supported only if the URT library is available.) | 20 | Toolkit format). (RLE is supported only if the URT library is available.) |
21 | .SH OPTIONS | 21 | .SH OPTIONS |
22 | All switch names may be abbreviated; for example, | 22 | All switch names may be abbreviated; for example, |
23 | .B \-grayscale | 23 | .B \-grayscale |
24 | may be written | 24 | may be written |
25 | .B \-gray | 25 | .B \-gray |
26 | or | 26 | or |
27 | .BR \-gr . | 27 | .BR \-gr . |
28 | Most of the "basic" switches can be abbreviated to as little as one letter. | 28 | Most of the "basic" switches can be abbreviated to as little as one letter. |
29 | Upper and lower case are equivalent (thus | 29 | Upper and lower case are equivalent (thus |
30 | .B \-BMP | 30 | .B \-BMP |
31 | is the same as | 31 | is the same as |
32 | .BR \-bmp ). | 32 | .BR \-bmp ). |
33 | British spellings are also accepted (e.g., | 33 | British spellings are also accepted (e.g., |
34 | .BR \-greyscale ), | 34 | .BR \-greyscale ), |
35 | though for brevity these are not mentioned below. | 35 | though for brevity these are not mentioned below. |
36 | .PP | 36 | .PP |
37 | The basic switches are: | 37 | The basic switches are: |
38 | .TP | 38 | .TP |
39 | .BI \-quality " N[,...]" | 39 | .BI \-quality " N[,...]" |
40 | Scale quantization tables to adjust image quality. Quality is 0 (worst) to | 40 | Scale quantization tables to adjust image quality. Quality is 0 (worst) to |
41 | 100 (best); default is 75. (See below for more info.) | 41 | 100 (best); default is 75. (See below for more info.) |
42 | .TP | 42 | .TP |
43 | .B \-grayscale | 43 | .B \-grayscale |
44 | Create monochrome JPEG file from color input. Be sure to use this switch when | 44 | Create monochrome JPEG file from color input. Be sure to use this switch when |
45 | compressing a grayscale BMP file, because | 45 | compressing a grayscale BMP file, because |
46 | .B cjpeg | 46 | .B cjpeg |
47 | isn't bright enough to notice whether a BMP file uses only shades of gray. | 47 | isn't bright enough to notice whether a BMP file uses only shades of gray. |
48 | By saying | 48 | By saying |
49 | .BR \-grayscale , | 49 | .BR \-grayscale , |
50 | you'll get a smaller JPEG file that takes less time to process. | 50 | you'll get a smaller JPEG file that takes less time to process. |
51 | .TP | 51 | .TP |
52 | .B \-rgb | 52 | .B \-rgb |
53 | Create RGB JPEG file. | 53 | Create RGB JPEG file. |
54 | Using this switch suppresses the conversion from RGB | 54 | Using this switch suppresses the conversion from RGB |
55 | colorspace input to the default YCbCr JPEG colorspace. | 55 | colorspace input to the default YCbCr JPEG colorspace. |
56 | Use this switch in combination with the | 56 | Use this switch in combination with the |
57 | .BI \-block " N" | 57 | .BI \-block " N" |
58 | switch (see below) for lossless JPEG coding. | 58 | switch (see below) for lossless JPEG coding. |
59 | .TP | 59 | .TP |
60 | .B \-optimize | 60 | .B \-optimize |
61 | Perform optimization of entropy encoding parameters. Without this, default | 61 | Perform optimization of entropy encoding parameters. Without this, default |
62 | encoding parameters are used. | 62 | encoding parameters are used. |
63 | .B \-optimize | 63 | .B \-optimize |
64 | usually makes the JPEG file a little smaller, but | 64 | usually makes the JPEG file a little smaller, but |
65 | .B cjpeg | 65 | .B cjpeg |
66 | runs somewhat slower and needs much more memory. Image quality and speed of | 66 | runs somewhat slower and needs much more memory. Image quality and speed of |
67 | decompression are unaffected by | 67 | decompression are unaffected by |
68 | .BR \-optimize . | 68 | .BR \-optimize . |
69 | .TP | 69 | .TP |
70 | .B \-progressive | 70 | .B \-progressive |
71 | Create progressive JPEG file (see below). | 71 | Create progressive JPEG file (see below). |
72 | .TP | 72 | .TP |
73 | .BI \-scale " M/N" | 73 | .BI \-scale " M/N" |
74 | Scale the output image by a factor M/N. Currently supported scale factors are | 74 | Scale the output image by a factor M/N. Currently supported scale factors are |
75 | M/N with all N from 1 to 16, where M is the destination DCT size, which is 8 | 75 | M/N with all N from 1 to 16, where M is the destination DCT size, which is 8 |
76 | by default (see | 76 | by default (see |
77 | .BI \-block " N" | 77 | .BI \-block " N" |
78 | switch below). | 78 | switch below). |
79 | .TP | 79 | .TP |
80 | .B \-targa | 80 | .B \-targa |
81 | Input file is Targa format. Targa files that contain an "identification" | 81 | Input file is Targa format. Targa files that contain an "identification" |
82 | field will not be automatically recognized by | 82 | field will not be automatically recognized by |
83 | .BR cjpeg ; | 83 | .BR cjpeg ; |
84 | for such files you must specify | 84 | for such files you must specify |
85 | .B \-targa | 85 | .B \-targa |
86 | to make | 86 | to make |
87 | .B cjpeg | 87 | .B cjpeg |
88 | treat the input as Targa format. | 88 | treat the input as Targa format. |
89 | For most Targa files, you won't need this switch. | 89 | For most Targa files, you won't need this switch. |
90 | .PP | 90 | .PP |
91 | The | 91 | The |
92 | .B \-quality | 92 | .B \-quality |
93 | switch lets you trade off compressed file size against quality of the | 93 | switch lets you trade off compressed file size against quality of the |
94 | reconstructed image: the higher the quality setting, the larger the JPEG file, | 94 | reconstructed image: the higher the quality setting, the larger the JPEG file, |
95 | and the closer the output image will be to the original input. Normally you | 95 | and the closer the output image will be to the original input. Normally you |
96 | want to use the lowest quality setting (smallest file) that decompresses into | 96 | want to use the lowest quality setting (smallest file) that decompresses into |
97 | something visually indistinguishable from the original image. For this | 97 | something visually indistinguishable from the original image. For this |
98 | purpose the quality setting should be between 50 and 95; the default of 75 is | 98 | purpose the quality setting should be between 50 and 95; the default of 75 is |
99 | often about right. If you see defects at | 99 | often about right. If you see defects at |
100 | .B \-quality | 100 | .B \-quality |
101 | 75, then go up 5 or 10 counts at a time until you are happy with the output | 101 | 75, then go up 5 or 10 counts at a time until you are happy with the output |
102 | image. (The optimal setting will vary from one image to another.) | 102 | image. (The optimal setting will vary from one image to another.) |
103 | .PP | 103 | .PP |
104 | .B \-quality | 104 | .B \-quality |
105 | 100 will generate a quantization table of all 1's, minimizing loss in the | 105 | 100 will generate a quantization table of all 1's, minimizing loss in the |
106 | quantization step (but there is still information loss in subsampling, as well | 106 | quantization step (but there is still information loss in subsampling, as well |
107 | as roundoff error). This setting is mainly of interest for experimental | 107 | as roundoff error). This setting is mainly of interest for experimental |
108 | purposes. Quality values above about 95 are | 108 | purposes. Quality values above about 95 are |
109 | .B not | 109 | .B not |
110 | recommended for normal use; the compressed file size goes up dramatically for | 110 | recommended for normal use; the compressed file size goes up dramatically for |
111 | hardly any gain in output image quality. | 111 | hardly any gain in output image quality. |
112 | .PP | 112 | .PP |
113 | In the other direction, quality values below 50 will produce very small files | 113 | In the other direction, quality values below 50 will produce very small files |
114 | of low image quality. Settings around 5 to 10 might be useful in preparing an | 114 | of low image quality. Settings around 5 to 10 might be useful in preparing an |
115 | index of a large image library, for example. Try | 115 | index of a large image library, for example. Try |
116 | .B \-quality | 116 | .B \-quality |
117 | 2 (or so) for some amusing Cubist effects. (Note: quality | 117 | 2 (or so) for some amusing Cubist effects. (Note: quality |
118 | values below about 25 generate 2-byte quantization tables, which are | 118 | values below about 25 generate 2-byte quantization tables, which are |
119 | considered optional in the JPEG standard. | 119 | considered optional in the JPEG standard. |
120 | .B cjpeg | 120 | .B cjpeg |
121 | emits a warning message when you give such a quality value, because some | 121 | emits a warning message when you give such a quality value, because some |
122 | other JPEG programs may be unable to decode the resulting file. Use | 122 | other JPEG programs may be unable to decode the resulting file. Use |
123 | .B \-baseline | 123 | .B \-baseline |
124 | if you need to ensure compatibility at low quality values.) | 124 | if you need to ensure compatibility at low quality values.) |
125 | .PP | 125 | .PP |
126 | The | 126 | The |
127 | .B \-quality | 127 | .B \-quality |
128 | option has been extended in IJG version 7 for support of separate quality | 128 | option has been extended in IJG version 7 for support of separate quality |
129 | settings for luminance and chrominance (or in general, for every provided | 129 | settings for luminance and chrominance (or in general, for every provided |
130 | quantization table slot). This feature is useful for high-quality | 130 | quantization table slot). This feature is useful for high-quality |
131 | applications which cannot accept the damage of color data by coarse | 131 | applications which cannot accept the damage of color data by coarse |
132 | subsampling settings. You can now easily reduce the color data amount more | 132 | subsampling settings. You can now easily reduce the color data amount more |
133 | smoothly with finer control without separate subsampling. The resulting file | 133 | smoothly with finer control without separate subsampling. The resulting file |
134 | is fully compliant with standard JPEG decoders. | 134 | is fully compliant with standard JPEG decoders. |
135 | Note that the | 135 | Note that the |
136 | .B \-quality | 136 | .B \-quality |
137 | ratings refer to the quantization table slots, and that the last value is | 137 | ratings refer to the quantization table slots, and that the last value is |
138 | replicated if there are more q-table slots than parameters. The default | 138 | replicated if there are more q-table slots than parameters. The default |
139 | q-table slots are 0 for luminance and 1 for chrominance with default tables as | 139 | q-table slots are 0 for luminance and 1 for chrominance with default tables as |
140 | given in the JPEG standard. This is compatible with the old behaviour in case | 140 | given in the JPEG standard. This is compatible with the old behaviour in case |
141 | that only one parameter is given, which is then used for both luminance and | 141 | that only one parameter is given, which is then used for both luminance and |
142 | chrominance (slots 0 and 1). More or custom quantization tables can be set | 142 | chrominance (slots 0 and 1). More or custom quantization tables can be set |
143 | with | 143 | with |
144 | .B \-qtables | 144 | .B \-qtables |
145 | and assigned to components with | 145 | and assigned to components with |
146 | .B \-qslots | 146 | .B \-qslots |
147 | parameter (see the "wizard" switches below). | 147 | parameter (see the "wizard" switches below). |
148 | .B Caution: | 148 | .B Caution: |
149 | You must explicitly add | 149 | You must explicitly add |
150 | .BI \-sample " 1x1" | 150 | .BI \-sample " 1x1" |
151 | for efficient separate color | 151 | for efficient separate color |
152 | quality selection, since the default value used by library is 2x2! | 152 | quality selection, since the default value used by library is 2x2! |
153 | .PP | 153 | .PP |
154 | The | 154 | The |
155 | .B \-progressive | 155 | .B \-progressive |
156 | switch creates a "progressive JPEG" file. In this type of JPEG file, the data | 156 | switch creates a "progressive JPEG" file. In this type of JPEG file, the data |
157 | is stored in multiple scans of increasing quality. If the file is being | 157 | is stored in multiple scans of increasing quality. If the file is being |
158 | transmitted over a slow communications link, the decoder can use the first | 158 | transmitted over a slow communications link, the decoder can use the first |
159 | scan to display a low-quality image very quickly, and can then improve the | 159 | scan to display a low-quality image very quickly, and can then improve the |
160 | display with each subsequent scan. The final image is exactly equivalent to a | 160 | display with each subsequent scan. The final image is exactly equivalent to a |
161 | standard JPEG file of the same quality setting, and the total file size is | 161 | standard JPEG file of the same quality setting, and the total file size is |
162 | about the same --- often a little smaller. | 162 | about the same --- often a little smaller. |
163 | .PP | 163 | .PP |
164 | Switches for advanced users: | 164 | Switches for advanced users: |
165 | .TP | 165 | .TP |
166 | .B \-arithmetic | 166 | .B \-arithmetic |
167 | Use arithmetic coding. | 167 | Use arithmetic coding. |
168 | .B Caution: | 168 | .B Caution: |
169 | arithmetic coded JPEG is not yet widely implemented, so many decoders will be | 169 | arithmetic coded JPEG is not yet widely implemented, so many decoders will be |
170 | unable to view an arithmetic coded JPEG file at all. | 170 | unable to view an arithmetic coded JPEG file at all. |
171 | .TP | 171 | .TP |
172 | .BI \-block " N" | 172 | .BI \-block " N" |
173 | Set DCT block size. All N from 1 to 16 are possible. | 173 | Set DCT block size. All N from 1 to 16 are possible. |
174 | Default is 8 (baseline format). | 174 | Default is 8 (baseline format). |
175 | Larger values produce higher compression, | 175 | Larger values produce higher compression, |
176 | smaller values produce higher quality | 176 | smaller values produce higher quality |
177 | (exact DCT stage possible with 1 or 2; with the default quality of 75 and | 177 | (exact DCT stage possible with 1 or 2; with the default quality of 75 and |
178 | default Luminance qtable the DCT+Quantization stage is lossless for N=1). | 178 | default Luminance qtable the DCT+Quantization stage is lossless for N=1). |
179 | .B Caution: | 179 | .B Caution: |
180 | An implementation of the JPEG SmartScale extension is required for this | 180 | An implementation of the JPEG SmartScale extension is required for this |
181 | feature. SmartScale enabled JPEG is not yet widely implemented, so many | 181 | feature. SmartScale enabled JPEG is not yet widely implemented, so many |
182 | decoders will be unable to view a SmartScale extended JPEG file at all. | 182 | decoders will be unable to view a SmartScale extended JPEG file at all. |
183 | .TP | 183 | .TP |
184 | .B \-dct int | 184 | .B \-dct int |
185 | Use integer DCT method (default). | 185 | Use integer DCT method (default). |
186 | .TP | 186 | .TP |
187 | .B \-dct fast | 187 | .B \-dct fast |
188 | Use fast integer DCT (less accurate). | 188 | Use fast integer DCT (less accurate). |
189 | .TP | 189 | .TP |
190 | .B \-dct float | 190 | .B \-dct float |
191 | Use floating-point DCT method. | 191 | Use floating-point DCT method. |
192 | The float method is very slightly more accurate than the int method, but is | 192 | The float method is very slightly more accurate than the int method, but is |
193 | much slower unless your machine has very fast floating-point hardware. Also | 193 | much slower unless your machine has very fast floating-point hardware. Also |
194 | note that results of the floating-point method may vary slightly across | 194 | note that results of the floating-point method may vary slightly across |
195 | machines, while the integer methods should give the same results everywhere. | 195 | machines, while the integer methods should give the same results everywhere. |
196 | The fast integer method is much less accurate than the other two. | 196 | The fast integer method is much less accurate than the other two. |
197 | .TP | 197 | .TP |
198 | .B \-nosmooth | 198 | .B \-nosmooth |
199 | Don't use high-quality downsampling. | 199 | Don't use high-quality downsampling. |
200 | .TP | 200 | .TP |
201 | .BI \-restart " N" | 201 | .BI \-restart " N" |
202 | Emit a JPEG restart marker every N MCU rows, or every N MCU blocks if "B" is | 202 | Emit a JPEG restart marker every N MCU rows, or every N MCU blocks if "B" is |
203 | attached to the number. | 203 | attached to the number. |
204 | .B \-restart 0 | 204 | .B \-restart 0 |
205 | (the default) means no restart markers. | 205 | (the default) means no restart markers. |
206 | .TP | 206 | .TP |
207 | .BI \-smooth " N" | 207 | .BI \-smooth " N" |
208 | Smooth the input image to eliminate dithering noise. N, ranging from 1 to | 208 | Smooth the input image to eliminate dithering noise. N, ranging from 1 to |
209 | 100, indicates the strength of smoothing. 0 (the default) means no smoothing. | 209 | 100, indicates the strength of smoothing. 0 (the default) means no smoothing. |
210 | .TP | 210 | .TP |
211 | .BI \-maxmemory " N" | 211 | .BI \-maxmemory " N" |
212 | Set limit for amount of memory to use in processing large images. Value is | 212 | Set limit for amount of memory to use in processing large images. Value is |
213 | in thousands of bytes, or millions of bytes if "M" is attached to the | 213 | in thousands of bytes, or millions of bytes if "M" is attached to the |
214 | number. For example, | 214 | number. For example, |
215 | .B \-max 4m | 215 | .B \-max 4m |
216 | selects 4000000 bytes. If more space is needed, temporary files will be used. | 216 | selects 4000000 bytes. If more space is needed, temporary files will be used. |
217 | .TP | 217 | .TP |
218 | .BI \-outfile " name" | 218 | .BI \-outfile " name" |
219 | Send output image to the named file, not to standard output. | 219 | Send output image to the named file, not to standard output. |
220 | .TP | 220 | .TP |
221 | .B \-verbose | 221 | .B \-verbose |
222 | Enable debug printout. More | 222 | Enable debug printout. More |
223 | .BR \-v 's | 223 | .BR \-v 's |
224 | give more output. Also, version information is printed at startup. | 224 | give more output. Also, version information is printed at startup. |
225 | .TP | 225 | .TP |
226 | .B \-debug | 226 | .B \-debug |
227 | Same as | 227 | Same as |
228 | .BR \-verbose . | 228 | .BR \-verbose . |
229 | .PP | 229 | .PP |
230 | The | 230 | The |
231 | .B \-restart | 231 | .B \-restart |
232 | option inserts extra markers that allow a JPEG decoder to resynchronize after | 232 | option inserts extra markers that allow a JPEG decoder to resynchronize after |
233 | a transmission error. Without restart markers, any damage to a compressed | 233 | a transmission error. Without restart markers, any damage to a compressed |
234 | file will usually ruin the image from the point of the error to the end of the | 234 | file will usually ruin the image from the point of the error to the end of the |
235 | image; with restart markers, the damage is usually confined to the portion of | 235 | image; with restart markers, the damage is usually confined to the portion of |
236 | the image up to the next restart marker. Of course, the restart markers | 236 | the image up to the next restart marker. Of course, the restart markers |
237 | occupy extra space. We recommend | 237 | occupy extra space. We recommend |
238 | .B \-restart 1 | 238 | .B \-restart 1 |
239 | for images that will be transmitted across unreliable networks such as Usenet. | 239 | for images that will be transmitted across unreliable networks such as Usenet. |
240 | .PP | 240 | .PP |
241 | The | 241 | The |
242 | .B \-smooth | 242 | .B \-smooth |
243 | option filters the input to eliminate fine-scale noise. This is often useful | 243 | option filters the input to eliminate fine-scale noise. This is often useful |
244 | when converting dithered images to JPEG: a moderate smoothing factor of 10 to | 244 | when converting dithered images to JPEG: a moderate smoothing factor of 10 to |
245 | 50 gets rid of dithering patterns in the input file, resulting in a smaller | 245 | 50 gets rid of dithering patterns in the input file, resulting in a smaller |
246 | JPEG file and a better-looking image. Too large a smoothing factor will | 246 | JPEG file and a better-looking image. Too large a smoothing factor will |
247 | visibly blur the image, however. | 247 | visibly blur the image, however. |
248 | .PP | 248 | .PP |
249 | Switches for wizards: | 249 | Switches for wizards: |
250 | .TP | 250 | .TP |
251 | .B \-baseline | 251 | .B \-baseline |
252 | Force baseline-compatible quantization tables to be generated. This clamps | 252 | Force baseline-compatible quantization tables to be generated. This clamps |
253 | quantization values to 8 bits even at low quality settings. (This switch is | 253 | quantization values to 8 bits even at low quality settings. (This switch is |
254 | poorly named, since it does not ensure that the output is actually baseline | 254 | poorly named, since it does not ensure that the output is actually baseline |
255 | JPEG. For example, you can use | 255 | JPEG. For example, you can use |
256 | .B \-baseline | 256 | .B \-baseline |
257 | and | 257 | and |
258 | .B \-progressive | 258 | .B \-progressive |
259 | together.) | 259 | together.) |
260 | .TP | 260 | .TP |
261 | .BI \-qtables " file" | 261 | .BI \-qtables " file" |
262 | Use the quantization tables given in the specified text file. | 262 | Use the quantization tables given in the specified text file. |
263 | .TP | 263 | .TP |
264 | .BI \-qslots " N[,...]" | 264 | .BI \-qslots " N[,...]" |
265 | Select which quantization table to use for each color component. | 265 | Select which quantization table to use for each color component. |
266 | .TP | 266 | .TP |
267 | .BI \-sample " HxV[,...]" | 267 | .BI \-sample " HxV[,...]" |
268 | Set JPEG sampling factors for each color component. | 268 | Set JPEG sampling factors for each color component. |
269 | .TP | 269 | .TP |
270 | .BI \-scans " file" | 270 | .BI \-scans " file" |
271 | Use the scan script given in the specified text file. | 271 | Use the scan script given in the specified text file. |
272 | .PP | 272 | .PP |
273 | The "wizard" switches are intended for experimentation with JPEG. If you | 273 | The "wizard" switches are intended for experimentation with JPEG. If you |
274 | don't know what you are doing, \fBdon't use them\fR. These switches are | 274 | don't know what you are doing, \fBdon't use them\fR. These switches are |
275 | documented further in the file wizard.txt. | 275 | documented further in the file wizard.txt. |
276 | .SH EXAMPLES | 276 | .SH EXAMPLES |
277 | .LP | 277 | .LP |
278 | This example compresses the PPM file foo.ppm with a quality factor of | 278 | This example compresses the PPM file foo.ppm with a quality factor of |
279 | 60 and saves the output as foo.jpg: | 279 | 60 and saves the output as foo.jpg: |
280 | .IP | 280 | .IP |
281 | .B cjpeg \-quality | 281 | .B cjpeg \-quality |
282 | .I 60 foo.ppm | 282 | .I 60 foo.ppm |
283 | .B > | 283 | .B > |
284 | .I foo.jpg | 284 | .I foo.jpg |
285 | .SH HINTS | 285 | .SH HINTS |
286 | Color GIF files are not the ideal input for JPEG; JPEG is really intended for | 286 | Color GIF files are not the ideal input for JPEG; JPEG is really intended for |
287 | compressing full-color (24-bit) images. In particular, don't try to convert | 287 | compressing full-color (24-bit) images. In particular, don't try to convert |
288 | cartoons, line drawings, and other images that have only a few distinct | 288 | cartoons, line drawings, and other images that have only a few distinct |
289 | colors. GIF works great on these, JPEG does not. If you want to convert a | 289 | colors. GIF works great on these, JPEG does not. If you want to convert a |
290 | GIF to JPEG, you should experiment with | 290 | GIF to JPEG, you should experiment with |
291 | .BR cjpeg 's | 291 | .BR cjpeg 's |
292 | .B \-quality | 292 | .B \-quality |
293 | and | 293 | and |
294 | .B \-smooth | 294 | .B \-smooth |
295 | options to get a satisfactory conversion. | 295 | options to get a satisfactory conversion. |
296 | .B \-smooth 10 | 296 | .B \-smooth 10 |
297 | or so is often helpful. | 297 | or so is often helpful. |
298 | .PP | 298 | .PP |
299 | Avoid running an image through a series of JPEG compression/decompression | 299 | Avoid running an image through a series of JPEG compression/decompression |
300 | cycles. Image quality loss will accumulate; after ten or so cycles the image | 300 | cycles. Image quality loss will accumulate; after ten or so cycles the image |
301 | may be noticeably worse than it was after one cycle. It's best to use a | 301 | may be noticeably worse than it was after one cycle. It's best to use a |
302 | lossless format while manipulating an image, then convert to JPEG format when | 302 | lossless format while manipulating an image, then convert to JPEG format when |
303 | you are ready to file the image away. | 303 | you are ready to file the image away. |
304 | .PP | 304 | .PP |
305 | The | 305 | The |
306 | .B \-optimize | 306 | .B \-optimize |
307 | option to | 307 | option to |
308 | .B cjpeg | 308 | .B cjpeg |
309 | is worth using when you are making a "final" version for posting or archiving. | 309 | is worth using when you are making a "final" version for posting or archiving. |
310 | It's also a win when you are using low quality settings to make very small | 310 | It's also a win when you are using low quality settings to make very small |
311 | JPEG files; the percentage improvement is often a lot more than it is on | 311 | JPEG files; the percentage improvement is often a lot more than it is on |
312 | larger files. (At present, | 312 | larger files. (At present, |
313 | .B \-optimize | 313 | .B \-optimize |
314 | mode is always selected when generating progressive JPEG files.) | 314 | mode is always selected when generating progressive JPEG files.) |
315 | .SH ENVIRONMENT | 315 | .SH ENVIRONMENT |
316 | .TP | 316 | .TP |
317 | .B JPEGMEM | 317 | .B JPEGMEM |
318 | If this environment variable is set, its value is the default memory limit. | 318 | If this environment variable is set, its value is the default memory limit. |
319 | The value is specified as described for the | 319 | The value is specified as described for the |
320 | .B \-maxmemory | 320 | .B \-maxmemory |
321 | switch. | 321 | switch. |
322 | .B JPEGMEM | 322 | .B JPEGMEM |
323 | overrides the default value specified when the program was compiled, and | 323 | overrides the default value specified when the program was compiled, and |
324 | itself is overridden by an explicit | 324 | itself is overridden by an explicit |
325 | .BR \-maxmemory . | 325 | .BR \-maxmemory . |
326 | .SH SEE ALSO | 326 | .SH SEE ALSO |
327 | .BR djpeg (1), | 327 | .BR djpeg (1), |
328 | .BR jpegtran (1), | 328 | .BR jpegtran (1), |
329 | .BR rdjpgcom (1), | 329 | .BR rdjpgcom (1), |
330 | .BR wrjpgcom (1) | 330 | .BR wrjpgcom (1) |
331 | .br | 331 | .br |
332 | .BR ppm (5), | 332 | .BR ppm (5), |
333 | .BR pgm (5) | 333 | .BR pgm (5) |
334 | .br | 334 | .br |
335 | Wallace, Gregory K. "The JPEG Still Picture Compression Standard", | 335 | Wallace, Gregory K. "The JPEG Still Picture Compression Standard", |
336 | Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44. | 336 | Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44. |
337 | .SH AUTHOR | 337 | .SH AUTHOR |
338 | Independent JPEG Group | 338 | Independent JPEG Group |
339 | .SH BUGS | 339 | .SH BUGS |
340 | GIF input files are no longer supported, to avoid the Unisys LZW patent. | 340 | GIF input files are no longer supported, to avoid the Unisys LZW patent. |
341 | (Conversion of GIF files to JPEG is usually a bad idea anyway.) | 341 | (Conversion of GIF files to JPEG is usually a bad idea anyway.) |
342 | .PP | 342 | .PP |
343 | Not all variants of BMP and Targa file formats are supported. | 343 | Not all variants of BMP and Targa file formats are supported. |
344 | .PP | 344 | .PP |
345 | The | 345 | The |
346 | .B \-targa | 346 | .B \-targa |
347 | switch is not a bug, it's a feature. (It would be a bug if the Targa format | 347 | switch is not a bug, it's a feature. (It would be a bug if the Targa format |
348 | designers had not been clueless.) | 348 | designers had not been clueless.) |