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1 libjpeg-turbo note: This file is mostly taken from the libjpeg v8b README | 1 libjpeg-turbo note: This file is mostly taken from the libjpeg v8b README |
2 file, and it is included only for reference. Some parts of it may not apply to | 2 file, and it is included only for reference. Some parts of it may not apply to |
3 libjpeg-turbo. Please see README-turbo.txt for information specific to the | 3 libjpeg-turbo. Please see README-turbo.txt for information specific to the |
4 turbo version. | 4 turbo version. |
5 | 5 |
6 | 6 |
7 The Independent JPEG Group's JPEG software | 7 The Independent JPEG Group's JPEG software |
8 ========================================== | 8 ========================================== |
9 | 9 |
10 This distribution contains a release of the Independent JPEG Group's free JPEG | 10 This distribution contains a release of the Independent JPEG Group's free JPEG |
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55 more of the REFERENCES, then looking at the documentation files (in roughly | 55 more of the REFERENCES, then looking at the documentation files (in roughly |
56 the order listed) before diving into the code. | 56 the order listed) before diving into the code. |
57 | 57 |
58 | 58 |
59 OVERVIEW | 59 OVERVIEW |
60 ======== | 60 ======== |
61 | 61 |
62 This package contains C software to implement JPEG image encoding, decoding, | 62 This package contains C software to implement JPEG image encoding, decoding, |
63 and transcoding. JPEG (pronounced "jay-peg") is a standardized compression | 63 and transcoding. JPEG (pronounced "jay-peg") is a standardized compression |
64 method for full-color and gray-scale images. JPEG's strong suit is compressing | 64 method for full-color and gray-scale images. JPEG's strong suit is compressing |
65 photographic images or other types of images which have smooth color and | 65 photographic images or other types of images that have smooth color and |
66 brightness transitions between neighboring pixels. Images with sharp lines or | 66 brightness transitions between neighboring pixels. Images with sharp lines or |
67 other abrupt features may not compress well with JPEG, and a higher JPEG | 67 other abrupt features may not compress well with JPEG, and a higher JPEG |
68 quality may have to be used to avoid visible compression artifacts with such | 68 quality may have to be used to avoid visible compression artifacts with such |
69 images. | 69 images. |
70 | 70 |
71 JPEG is lossy, meaning that the output pixels are not necessarily identical to | 71 JPEG is lossy, meaning that the output pixels are not necessarily identical to |
72 the input pixels. However, on photographic content and other "smooth" images, | 72 the input pixels. However, on photographic content and other "smooth" images, |
73 very good compression ratios can be obtained with no visible compression | 73 very good compression ratios can be obtained with no visible compression |
74 artifacts, and extremely high compression ratios are possible if you are | 74 artifacts, and extremely high compression ratios are possible if you are |
75 willing to sacrifice image quality (by reducing the "quality" setting in the | 75 willing to sacrifice image quality (by reducing the "quality" setting in the |
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267 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu | 267 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu |
268 with body | 268 with body |
269 send usenet/news.answers/jpeg-faq/part1 | 269 send usenet/news.answers/jpeg-faq/part1 |
270 send usenet/news.answers/jpeg-faq/part2 | 270 send usenet/news.answers/jpeg-faq/part2 |
271 | 271 |
272 | 272 |
273 FILE FORMAT WARS | 273 FILE FORMAT WARS |
274 ================ | 274 ================ |
275 | 275 |
276 The ISO JPEG standards committee actually promotes different formats like | 276 The ISO JPEG standards committee actually promotes different formats like |
277 "JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based | 277 "JPEG 2000" or "JPEG XR", which are incompatible with original DCT-based |
278 JPEG. IJG therefore does not support these formats (see REFERENCES). Indeed, | 278 JPEG. IJG therefore does not support these formats (see REFERENCES). Indeed, |
279 one of the original reasons for developing this free software was to help | 279 one of the original reasons for developing this free software was to help |
280 force convergence on common, interoperable format standards for JPEG files. | 280 force convergence on common, interoperable format standards for JPEG files. |
281 Don't use an incompatible file format! | 281 Don't use an incompatible file format! |
282 (In any case, our decoder will remain capable of reading existing JPEG | 282 (In any case, our decoder will remain capable of reading existing JPEG |
283 image files indefinitely.) | 283 image files indefinitely.) |
284 | 284 |
285 | 285 |
286 TO DO | 286 TO DO |
287 ===== | 287 ===== |
288 | 288 |
289 Please send bug reports, offers of help, etc. to jpeg-info@uc.ag. | 289 Please send bug reports, offers of help, etc. to jpeg-info@uc.ag. |
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