DRC | 39ea562 | 2010-10-12 01:55:31 +0000 | [diff] [blame] | 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 |
| 3 | libjpeg-turbo. Please see README-turbo.txt for information specific to the |
| 4 | turbo version. |
DRC | 03c3c9b | 2010-02-21 15:45:00 +0000 | [diff] [blame] | 5 | |
| 6 | |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 7 | The Independent JPEG Group's JPEG software |
| 8 | ========================================== |
| 9 | |
DRC | 39ea562 | 2010-10-12 01:55:31 +0000 | [diff] [blame] | 10 | This distribution contains a release of the Independent JPEG Group's free JPEG |
| 11 | software. You are welcome to redistribute this software and to use it for any |
| 12 | purpose, subject to the conditions under LEGAL ISSUES, below. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 13 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 14 | This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone, |
| 15 | Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson, |
| 16 | Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers, |
| 17 | and other members of the Independent JPEG Group. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 18 | |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 19 | IJG is not affiliated with the official ISO JPEG standards committee. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 20 | |
| 21 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 22 | DOCUMENTATION ROADMAP |
| 23 | ===================== |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 24 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 25 | This file contains the following sections: |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 26 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 27 | OVERVIEW General description of JPEG and the IJG software. |
| 28 | LEGAL ISSUES Copyright, lack of warranty, terms of distribution. |
| 29 | REFERENCES Where to learn more about JPEG. |
| 30 | ARCHIVE LOCATIONS Where to find newer versions of this software. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 31 | FILE FORMAT WARS Software *not* to get. |
| 32 | TO DO Plans for future IJG releases. |
| 33 | |
| 34 | Other documentation files in the distribution are: |
| 35 | |
| 36 | User documentation: |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 37 | install.txt How to configure and install the IJG software. |
| 38 | usage.txt Usage instructions for cjpeg, djpeg, jpegtran, |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 39 | rdjpgcom, and wrjpgcom. |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 40 | *.1 Unix-style man pages for programs (same info as usage.txt). |
| 41 | wizard.txt Advanced usage instructions for JPEG wizards only. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 42 | change.log Version-to-version change highlights. |
| 43 | Programmer and internal documentation: |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 44 | libjpeg.txt How to use the JPEG library in your own programs. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 45 | example.c Sample code for calling the JPEG library. |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 46 | structure.txt Overview of the JPEG library's internal structure. |
| 47 | filelist.txt Road map of IJG files. |
| 48 | coderules.txt Coding style rules --- please read if you contribute code. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 49 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 50 | Please read at least the files install.txt and usage.txt. Some information |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 51 | can also be found in the JPEG FAQ (Frequently Asked Questions) article. See |
| 52 | ARCHIVE LOCATIONS below to find out where to obtain the FAQ article. |
| 53 | |
| 54 | If you want to understand how the JPEG code works, we suggest reading one or |
| 55 | more of the REFERENCES, then looking at the documentation files (in roughly |
| 56 | the order listed) before diving into the code. |
Thomas G. Lane | bd543f0 | 1991-12-13 00:00:00 +0000 | [diff] [blame] | 57 | |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 58 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 59 | OVERVIEW |
| 60 | ======== |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 61 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 62 | This package contains C software to implement JPEG image encoding, decoding, |
| 63 | and transcoding. JPEG (pronounced "jay-peg") is a standardized compression |
DRC | 39ea562 | 2010-10-12 01:55:31 +0000 | [diff] [blame] | 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 |
| 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 |
| 68 | quality may have to be used to avoid visible compression artifacts with such |
| 69 | images. |
| 70 | |
| 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, |
| 73 | very good compression ratios can be obtained with no visible compression |
| 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 |
| 76 | compressor.) |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 77 | |
| 78 | This software implements JPEG baseline, extended-sequential, and progressive |
| 79 | compression processes. Provision is made for supporting all variants of these |
| 80 | processes, although some uncommon parameter settings aren't implemented yet. |
| 81 | For legal reasons, we are not distributing code for the arithmetic-coding |
| 82 | variants of JPEG; see LEGAL ISSUES. We have made no provision for supporting |
| 83 | the hierarchical or lossless processes defined in the standard. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 84 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 85 | We provide a set of library routines for reading and writing JPEG image files, |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 86 | plus two sample applications "cjpeg" and "djpeg", which use the library to |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 87 | perform conversion between JPEG and some other popular image file formats. |
| 88 | The library is intended to be reused in other applications. |
| 89 | |
Thomas G. Lane | 88aeed4 | 1992-12-10 00:00:00 +0000 | [diff] [blame] | 90 | In order to support file conversion and viewing software, we have included |
| 91 | considerable functionality beyond the bare JPEG coding/decoding capability; |
| 92 | for example, the color quantization modules are not strictly part of JPEG |
| 93 | decoding, but they are essential for output to colormapped file formats or |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 94 | colormapped displays. These extra functions can be compiled out of the |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 95 | library if not required for a particular application. |
| 96 | |
| 97 | We have also included "jpegtran", a utility for lossless transcoding between |
| 98 | different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple |
| 99 | applications for inserting and extracting textual comments in JFIF files. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 100 | |
| 101 | The emphasis in designing this software has been on achieving portability and |
Thomas G. Lane | 88aeed4 | 1992-12-10 00:00:00 +0000 | [diff] [blame] | 102 | flexibility, while also making it fast enough to be useful. In particular, |
| 103 | the software is not intended to be read as a tutorial on JPEG. (See the |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 104 | REFERENCES section for introductory material.) Rather, it is intended to |
| 105 | be reliable, portable, industrial-strength code. We do not claim to have |
| 106 | achieved that goal in every aspect of the software, but we strive for it. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 107 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 108 | We welcome the use of this software as a component of commercial products. |
| 109 | No royalty is required, but we do ask for an acknowledgement in product |
| 110 | documentation, as described under LEGAL ISSUES. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 111 | |
| 112 | |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 113 | LEGAL ISSUES |
| 114 | ============ |
| 115 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 116 | In plain English: |
| 117 | |
| 118 | 1. We don't promise that this software works. (But if you find any bugs, |
| 119 | please let us know!) |
| 120 | 2. You can use this software for whatever you want. You don't have to pay us. |
| 121 | 3. You may not pretend that you wrote this software. If you use it in a |
| 122 | program, you must acknowledge somewhere in your documentation that |
| 123 | you've used the IJG code. |
| 124 | |
| 125 | In legalese: |
| 126 | |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 127 | The authors make NO WARRANTY or representation, either express or implied, |
| 128 | with respect to this software, its quality, accuracy, merchantability, or |
| 129 | fitness for a particular purpose. This software is provided "AS IS", and you, |
| 130 | its user, assume the entire risk as to its quality and accuracy. |
| 131 | |
Guido Vollbeding | 989630f | 2010-01-10 00:00:00 +0000 | [diff] [blame] | 132 | This software is copyright (C) 1991-2010, Thomas G. Lane, Guido Vollbeding. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 133 | All Rights Reserved except as specified below. |
| 134 | |
| 135 | Permission is hereby granted to use, copy, modify, and distribute this |
| 136 | software (or portions thereof) for any purpose, without fee, subject to these |
| 137 | conditions: |
| 138 | (1) If any part of the source code for this software is distributed, then this |
| 139 | README file must be included, with this copyright and no-warranty notice |
| 140 | unaltered; and any additions, deletions, or changes to the original files |
| 141 | must be clearly indicated in accompanying documentation. |
| 142 | (2) If only executable code is distributed, then the accompanying |
| 143 | documentation must state that "this software is based in part on the work of |
| 144 | the Independent JPEG Group". |
| 145 | (3) Permission for use of this software is granted only if the user accepts |
| 146 | full responsibility for any undesirable consequences; the authors accept |
| 147 | NO LIABILITY for damages of any kind. |
| 148 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 149 | These conditions apply to any software derived from or based on the IJG code, |
| 150 | not just to the unmodified library. If you use our work, you ought to |
| 151 | acknowledge us. |
| 152 | |
Thomas G. Lane | 88aeed4 | 1992-12-10 00:00:00 +0000 | [diff] [blame] | 153 | Permission is NOT granted for the use of any IJG author's name or company name |
| 154 | in advertising or publicity relating to this software or products derived from |
| 155 | it. This software may be referred to only as "the Independent JPEG Group's |
| 156 | software". |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 157 | |
| 158 | We specifically permit and encourage the use of this software as the basis of |
| 159 | commercial products, provided that all warranty or liability claims are |
| 160 | assumed by the product vendor. |
| 161 | |
| 162 | |
| 163 | ansi2knr.c is included in this distribution by permission of L. Peter Deutsch, |
| 164 | sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA. |
| 165 | ansi2knr.c is NOT covered by the above copyright and conditions, but instead |
| 166 | by the usual distribution terms of the Free Software Foundation; principally, |
| 167 | that you must include source code if you redistribute it. (See the file |
| 168 | ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 169 | of any program generated from the IJG code, this does not limit you more than |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 170 | the foregoing paragraphs do. |
| 171 | |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 172 | The Unix configuration script "configure" was produced with GNU Autoconf. |
| 173 | It is copyright by the Free Software Foundation but is freely distributable. |
| 174 | The same holds for its supporting scripts (config.guess, config.sub, |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 175 | ltmain.sh). Another support script, install-sh, is copyright by X Consortium |
| 176 | but is also freely distributable. |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 177 | |
| 178 | It appears that the arithmetic coding option of the JPEG spec is covered by |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 179 | patents owned by IBM, AT&T, and Mitsubishi. Hence arithmetic coding cannot |
| 180 | legally be used without obtaining one or more licenses. For this reason, |
| 181 | support for arithmetic coding has been removed from the free JPEG software. |
| 182 | (Since arithmetic coding provides only a marginal gain over the unpatented |
| 183 | Huffman mode, it is unlikely that very many implementations will support it.) |
Thomas G. Lane | bd543f0 | 1991-12-13 00:00:00 +0000 | [diff] [blame] | 184 | So far as we are aware, there are no patent restrictions on the remaining |
| 185 | code. |
| 186 | |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 187 | The IJG distribution formerly included code to read and write GIF files. |
| 188 | To avoid entanglement with the Unisys LZW patent, GIF reading support has |
| 189 | been removed altogether, and the GIF writer has been simplified to produce |
| 190 | "uncompressed GIFs". This technique does not use the LZW algorithm; the |
| 191 | resulting GIF files are larger than usual, but are readable by all standard |
| 192 | GIF decoders. |
Thomas G. Lane | a8b67c4 | 1995-03-15 00:00:00 +0000 | [diff] [blame] | 193 | |
Thomas G. Lane | bd543f0 | 1991-12-13 00:00:00 +0000 | [diff] [blame] | 194 | We are required to state that |
| 195 | "The Graphics Interchange Format(c) is the Copyright property of |
| 196 | CompuServe Incorporated. GIF(sm) is a Service Mark property of |
| 197 | CompuServe Incorporated." |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 198 | |
| 199 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 200 | REFERENCES |
| 201 | ========== |
| 202 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 203 | We recommend reading one or more of these references before trying to |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 204 | understand the innards of the JPEG software. |
| 205 | |
| 206 | The best short technical introduction to the JPEG compression algorithm is |
| 207 | Wallace, Gregory K. "The JPEG Still Picture Compression Standard", |
| 208 | Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44. |
| 209 | (Adjacent articles in that issue discuss MPEG motion picture compression, |
| 210 | applications of JPEG, and related topics.) If you don't have the CACM issue |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 211 | handy, a PostScript file containing a revised version of Wallace's article is |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 212 | available at http://www.ijg.org/files/wallace.ps.gz. The file (actually |
Thomas G. Lane | 9ba2f5e | 1994-12-07 00:00:00 +0000 | [diff] [blame] | 213 | a preprint for an article that appeared in IEEE Trans. Consumer Electronics) |
| 214 | omits the sample images that appeared in CACM, but it includes corrections |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 215 | and some added material. Note: the Wallace article is copyright ACM and IEEE, |
| 216 | and it may not be used for commercial purposes. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 217 | |
| 218 | A somewhat less technical, more leisurely introduction to JPEG can be found in |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 219 | "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by |
| 220 | M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides |
| 221 | good explanations and example C code for a multitude of compression methods |
| 222 | including JPEG. It is an excellent source if you are comfortable reading C |
| 223 | code but don't know much about data compression in general. The book's JPEG |
| 224 | sample code is far from industrial-strength, but when you are ready to look |
| 225 | at a full implementation, you've got one here... |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 226 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 227 | The best currently available description of JPEG is the textbook "JPEG Still |
| 228 | Image Data Compression Standard" by William B. Pennebaker and Joan L. |
| 229 | Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1. |
| 230 | Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG |
| 231 | standards (DIS 10918-1 and draft DIS 10918-2). |
| 232 | Although this is by far the most detailed and comprehensive exposition of |
| 233 | JPEG publicly available, we point out that it is still missing an explanation |
| 234 | of the most essential properties and algorithms of the underlying DCT |
| 235 | technology. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 236 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 237 | The original JPEG standard is divided into two parts, Part 1 being the actual |
| 238 | specification, while Part 2 covers compliance testing methods. Part 1 is |
| 239 | titled "Digital Compression and Coding of Continuous-tone Still Images, |
Thomas G. Lane | 489583f | 1996-02-07 00:00:00 +0000 | [diff] [blame] | 240 | Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS |
| 241 | 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of |
| 242 | Continuous-tone Still Images, Part 2: Compliance testing" and has document |
| 243 | numbers ISO/IEC IS 10918-2, ITU-T T.83. |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 244 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 245 | The JPEG standard does not specify all details of an interchangeable file |
| 246 | format. For the omitted details we follow the "JFIF" conventions, revision |
Guido Vollbeding | 989630f | 2010-01-10 00:00:00 +0000 | [diff] [blame] | 247 | 1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report |
| 248 | and thus received a formal publication status. It is available as a free |
| 249 | download in PDF format from |
| 250 | http://www.ecma-international.org/publications/techreports/E-TR-098.htm. |
| 251 | A PostScript version of the JFIF document is available at |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 252 | http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at |
| 253 | http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 254 | |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 255 | The TIFF 6.0 file format specification can be obtained by FTP from |
| 256 | ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 257 | found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems. |
| 258 | IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6). |
| 259 | Instead, we recommend the JPEG design proposed by TIFF Technical Note #2 |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 260 | (Compression tag 7). Copies of this Note can be obtained from |
| 261 | http://www.ijg.org/files/. It is expected that the next revision |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 262 | of the TIFF spec will replace the 6.0 JPEG design with the Note's design. |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 263 | Although IJG's own code does not support TIFF/JPEG, the free libtiff library |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 264 | uses our library to implement TIFF/JPEG per the Note. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 265 | |
| 266 | |
| 267 | ARCHIVE LOCATIONS |
| 268 | ================= |
| 269 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 270 | The "official" archive site for this software is www.ijg.org. |
| 271 | The most recent released version can always be found there in |
| 272 | directory "files". This particular version will be archived as |
Guido Vollbeding | a4ecaac | 2010-05-16 00:00:00 +0000 | [diff] [blame] | 273 | http://www.ijg.org/files/jpegsrc.v8b.tar.gz, and in Windows-compatible |
| 274 | "zip" archive format as http://www.ijg.org/files/jpegsr8b.zip. |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 275 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 276 | The JPEG FAQ (Frequently Asked Questions) article is a source of some |
| 277 | general information about JPEG. |
Thomas G. Lane | 5ead57a | 1998-03-27 00:00:00 +0000 | [diff] [blame] | 278 | It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/ |
| 279 | and other news.answers archive sites, including the official news.answers |
| 280 | archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/. |
| 281 | If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu |
Thomas G. Lane | 9ba2f5e | 1994-12-07 00:00:00 +0000 | [diff] [blame] | 282 | with body |
| 283 | send usenet/news.answers/jpeg-faq/part1 |
| 284 | send usenet/news.answers/jpeg-faq/part2 |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 285 | |
| 286 | |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 287 | FILE FORMAT WARS |
| 288 | ================ |
| 289 | |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 290 | The ISO JPEG standards committee actually promotes different formats like |
Guido Vollbeding | 989630f | 2010-01-10 00:00:00 +0000 | [diff] [blame] | 291 | "JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based |
DRC | 39ea562 | 2010-10-12 01:55:31 +0000 | [diff] [blame] | 292 | JPEG. IJG therefore does not support these formats (see REFERENCES). Indeed, |
Thomas G. Lane | bc79e06 | 1995-08-02 00:00:00 +0000 | [diff] [blame] | 293 | one of the original reasons for developing this free software was to help |
Guido Vollbeding | 5996a25 | 2009-06-27 00:00:00 +0000 | [diff] [blame] | 294 | force convergence on common, interoperable format standards for JPEG files. |
| 295 | Don't use an incompatible file format! |
| 296 | (In any case, our decoder will remain capable of reading existing JPEG |
| 297 | image files indefinitely.) |
Thomas G. Lane | 36a4ccc | 1994-09-24 00:00:00 +0000 | [diff] [blame] | 298 | |
| 299 | |
Thomas G. Lane | 2cbeb8a | 1991-10-07 00:00:00 +0000 | [diff] [blame] | 300 | TO DO |
| 301 | ===== |
| 302 | |
Guido Vollbeding | 989630f | 2010-01-10 00:00:00 +0000 | [diff] [blame] | 303 | Please send bug reports, offers of help, etc. to jpeg-info@uc.ag. |