rev |
line source |
nuclear@39
|
1 The Independent JPEG Group's JPEG software
|
nuclear@39
|
2 ==========================================
|
nuclear@39
|
3
|
nuclear@39
|
4 README for release 8c of 16-Jan-2011
|
nuclear@39
|
5 ====================================
|
nuclear@39
|
6
|
nuclear@39
|
7 This distribution contains the eighth public release of the Independent JPEG
|
nuclear@39
|
8 Group's free JPEG software. You are welcome to redistribute this software and
|
nuclear@39
|
9 to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.
|
nuclear@39
|
10
|
nuclear@39
|
11 This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone,
|
nuclear@39
|
12 Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson,
|
nuclear@39
|
13 Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,
|
nuclear@39
|
14 and other members of the Independent JPEG Group.
|
nuclear@39
|
15
|
nuclear@39
|
16 IJG is not affiliated with the official ISO JPEG standards committee.
|
nuclear@39
|
17
|
nuclear@39
|
18
|
nuclear@39
|
19 DOCUMENTATION ROADMAP
|
nuclear@39
|
20 =====================
|
nuclear@39
|
21
|
nuclear@39
|
22 This file contains the following sections:
|
nuclear@39
|
23
|
nuclear@39
|
24 OVERVIEW General description of JPEG and the IJG software.
|
nuclear@39
|
25 LEGAL ISSUES Copyright, lack of warranty, terms of distribution.
|
nuclear@39
|
26 REFERENCES Where to learn more about JPEG.
|
nuclear@39
|
27 ARCHIVE LOCATIONS Where to find newer versions of this software.
|
nuclear@39
|
28 ACKNOWLEDGMENTS Special thanks.
|
nuclear@39
|
29 FILE FORMAT WARS Software *not* to get.
|
nuclear@39
|
30 TO DO Plans for future IJG releases.
|
nuclear@39
|
31
|
nuclear@39
|
32 Other documentation files in the distribution are:
|
nuclear@39
|
33
|
nuclear@39
|
34 User documentation:
|
nuclear@39
|
35 install.txt How to configure and install the IJG software.
|
nuclear@39
|
36 usage.txt Usage instructions for cjpeg, djpeg, jpegtran,
|
nuclear@39
|
37 rdjpgcom, and wrjpgcom.
|
nuclear@39
|
38 *.1 Unix-style man pages for programs (same info as usage.txt).
|
nuclear@39
|
39 wizard.txt Advanced usage instructions for JPEG wizards only.
|
nuclear@39
|
40 change.log Version-to-version change highlights.
|
nuclear@39
|
41 Programmer and internal documentation:
|
nuclear@39
|
42 libjpeg.txt How to use the JPEG library in your own programs.
|
nuclear@39
|
43 example.c Sample code for calling the JPEG library.
|
nuclear@39
|
44 structure.txt Overview of the JPEG library's internal structure.
|
nuclear@39
|
45 filelist.txt Road map of IJG files.
|
nuclear@39
|
46 coderules.txt Coding style rules --- please read if you contribute code.
|
nuclear@39
|
47
|
nuclear@39
|
48 Please read at least the files install.txt and usage.txt. Some information
|
nuclear@39
|
49 can also be found in the JPEG FAQ (Frequently Asked Questions) article. See
|
nuclear@39
|
50 ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.
|
nuclear@39
|
51
|
nuclear@39
|
52 If you want to understand how the JPEG code works, we suggest reading one or
|
nuclear@39
|
53 more of the REFERENCES, then looking at the documentation files (in roughly
|
nuclear@39
|
54 the order listed) before diving into the code.
|
nuclear@39
|
55
|
nuclear@39
|
56
|
nuclear@39
|
57 OVERVIEW
|
nuclear@39
|
58 ========
|
nuclear@39
|
59
|
nuclear@39
|
60 This package contains C software to implement JPEG image encoding, decoding,
|
nuclear@39
|
61 and transcoding. JPEG (pronounced "jay-peg") is a standardized compression
|
nuclear@39
|
62 method for full-color and gray-scale images.
|
nuclear@39
|
63
|
nuclear@39
|
64 This software implements JPEG baseline, extended-sequential, and progressive
|
nuclear@39
|
65 compression processes. Provision is made for supporting all variants of these
|
nuclear@39
|
66 processes, although some uncommon parameter settings aren't implemented yet.
|
nuclear@39
|
67 We have made no provision for supporting the hierarchical or lossless
|
nuclear@39
|
68 processes defined in the standard.
|
nuclear@39
|
69
|
nuclear@39
|
70 We provide a set of library routines for reading and writing JPEG image files,
|
nuclear@39
|
71 plus two sample applications "cjpeg" and "djpeg", which use the library to
|
nuclear@39
|
72 perform conversion between JPEG and some other popular image file formats.
|
nuclear@39
|
73 The library is intended to be reused in other applications.
|
nuclear@39
|
74
|
nuclear@39
|
75 In order to support file conversion and viewing software, we have included
|
nuclear@39
|
76 considerable functionality beyond the bare JPEG coding/decoding capability;
|
nuclear@39
|
77 for example, the color quantization modules are not strictly part of JPEG
|
nuclear@39
|
78 decoding, but they are essential for output to colormapped file formats or
|
nuclear@39
|
79 colormapped displays. These extra functions can be compiled out of the
|
nuclear@39
|
80 library if not required for a particular application.
|
nuclear@39
|
81
|
nuclear@39
|
82 We have also included "jpegtran", a utility for lossless transcoding between
|
nuclear@39
|
83 different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple
|
nuclear@39
|
84 applications for inserting and extracting textual comments in JFIF files.
|
nuclear@39
|
85
|
nuclear@39
|
86 The emphasis in designing this software has been on achieving portability and
|
nuclear@39
|
87 flexibility, while also making it fast enough to be useful. In particular,
|
nuclear@39
|
88 the software is not intended to be read as a tutorial on JPEG. (See the
|
nuclear@39
|
89 REFERENCES section for introductory material.) Rather, it is intended to
|
nuclear@39
|
90 be reliable, portable, industrial-strength code. We do not claim to have
|
nuclear@39
|
91 achieved that goal in every aspect of the software, but we strive for it.
|
nuclear@39
|
92
|
nuclear@39
|
93 We welcome the use of this software as a component of commercial products.
|
nuclear@39
|
94 No royalty is required, but we do ask for an acknowledgement in product
|
nuclear@39
|
95 documentation, as described under LEGAL ISSUES.
|
nuclear@39
|
96
|
nuclear@39
|
97
|
nuclear@39
|
98 LEGAL ISSUES
|
nuclear@39
|
99 ============
|
nuclear@39
|
100
|
nuclear@39
|
101 In plain English:
|
nuclear@39
|
102
|
nuclear@39
|
103 1. We don't promise that this software works. (But if you find any bugs,
|
nuclear@39
|
104 please let us know!)
|
nuclear@39
|
105 2. You can use this software for whatever you want. You don't have to pay us.
|
nuclear@39
|
106 3. You may not pretend that you wrote this software. If you use it in a
|
nuclear@39
|
107 program, you must acknowledge somewhere in your documentation that
|
nuclear@39
|
108 you've used the IJG code.
|
nuclear@39
|
109
|
nuclear@39
|
110 In legalese:
|
nuclear@39
|
111
|
nuclear@39
|
112 The authors make NO WARRANTY or representation, either express or implied,
|
nuclear@39
|
113 with respect to this software, its quality, accuracy, merchantability, or
|
nuclear@39
|
114 fitness for a particular purpose. This software is provided "AS IS", and you,
|
nuclear@39
|
115 its user, assume the entire risk as to its quality and accuracy.
|
nuclear@39
|
116
|
nuclear@39
|
117 This software is copyright (C) 1991-2011, Thomas G. Lane, Guido Vollbeding.
|
nuclear@39
|
118 All Rights Reserved except as specified below.
|
nuclear@39
|
119
|
nuclear@39
|
120 Permission is hereby granted to use, copy, modify, and distribute this
|
nuclear@39
|
121 software (or portions thereof) for any purpose, without fee, subject to these
|
nuclear@39
|
122 conditions:
|
nuclear@39
|
123 (1) If any part of the source code for this software is distributed, then this
|
nuclear@39
|
124 README file must be included, with this copyright and no-warranty notice
|
nuclear@39
|
125 unaltered; and any additions, deletions, or changes to the original files
|
nuclear@39
|
126 must be clearly indicated in accompanying documentation.
|
nuclear@39
|
127 (2) If only executable code is distributed, then the accompanying
|
nuclear@39
|
128 documentation must state that "this software is based in part on the work of
|
nuclear@39
|
129 the Independent JPEG Group".
|
nuclear@39
|
130 (3) Permission for use of this software is granted only if the user accepts
|
nuclear@39
|
131 full responsibility for any undesirable consequences; the authors accept
|
nuclear@39
|
132 NO LIABILITY for damages of any kind.
|
nuclear@39
|
133
|
nuclear@39
|
134 These conditions apply to any software derived from or based on the IJG code,
|
nuclear@39
|
135 not just to the unmodified library. If you use our work, you ought to
|
nuclear@39
|
136 acknowledge us.
|
nuclear@39
|
137
|
nuclear@39
|
138 Permission is NOT granted for the use of any IJG author's name or company name
|
nuclear@39
|
139 in advertising or publicity relating to this software or products derived from
|
nuclear@39
|
140 it. This software may be referred to only as "the Independent JPEG Group's
|
nuclear@39
|
141 software".
|
nuclear@39
|
142
|
nuclear@39
|
143 We specifically permit and encourage the use of this software as the basis of
|
nuclear@39
|
144 commercial products, provided that all warranty or liability claims are
|
nuclear@39
|
145 assumed by the product vendor.
|
nuclear@39
|
146
|
nuclear@39
|
147
|
nuclear@39
|
148 ansi2knr.c is included in this distribution by permission of L. Peter Deutsch,
|
nuclear@39
|
149 sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA.
|
nuclear@39
|
150 ansi2knr.c is NOT covered by the above copyright and conditions, but instead
|
nuclear@39
|
151 by the usual distribution terms of the Free Software Foundation; principally,
|
nuclear@39
|
152 that you must include source code if you redistribute it. (See the file
|
nuclear@39
|
153 ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part
|
nuclear@39
|
154 of any program generated from the IJG code, this does not limit you more than
|
nuclear@39
|
155 the foregoing paragraphs do.
|
nuclear@39
|
156
|
nuclear@39
|
157 The Unix configuration script "configure" was produced with GNU Autoconf.
|
nuclear@39
|
158 It is copyright by the Free Software Foundation but is freely distributable.
|
nuclear@39
|
159 The same holds for its supporting scripts (config.guess, config.sub,
|
nuclear@39
|
160 ltmain.sh). Another support script, install-sh, is copyright by X Consortium
|
nuclear@39
|
161 but is also freely distributable.
|
nuclear@39
|
162
|
nuclear@39
|
163 The IJG distribution formerly included code to read and write GIF files.
|
nuclear@39
|
164 To avoid entanglement with the Unisys LZW patent, GIF reading support has
|
nuclear@39
|
165 been removed altogether, and the GIF writer has been simplified to produce
|
nuclear@39
|
166 "uncompressed GIFs". This technique does not use the LZW algorithm; the
|
nuclear@39
|
167 resulting GIF files are larger than usual, but are readable by all standard
|
nuclear@39
|
168 GIF decoders.
|
nuclear@39
|
169
|
nuclear@39
|
170 We are required to state that
|
nuclear@39
|
171 "The Graphics Interchange Format(c) is the Copyright property of
|
nuclear@39
|
172 CompuServe Incorporated. GIF(sm) is a Service Mark property of
|
nuclear@39
|
173 CompuServe Incorporated."
|
nuclear@39
|
174
|
nuclear@39
|
175
|
nuclear@39
|
176 REFERENCES
|
nuclear@39
|
177 ==========
|
nuclear@39
|
178
|
nuclear@39
|
179 We recommend reading one or more of these references before trying to
|
nuclear@39
|
180 understand the innards of the JPEG software.
|
nuclear@39
|
181
|
nuclear@39
|
182 The best short technical introduction to the JPEG compression algorithm is
|
nuclear@39
|
183 Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
|
nuclear@39
|
184 Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
|
nuclear@39
|
185 (Adjacent articles in that issue discuss MPEG motion picture compression,
|
nuclear@39
|
186 applications of JPEG, and related topics.) If you don't have the CACM issue
|
nuclear@39
|
187 handy, a PostScript file containing a revised version of Wallace's article is
|
nuclear@39
|
188 available at http://www.ijg.org/files/wallace.ps.gz. The file (actually
|
nuclear@39
|
189 a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
|
nuclear@39
|
190 omits the sample images that appeared in CACM, but it includes corrections
|
nuclear@39
|
191 and some added material. Note: the Wallace article is copyright ACM and IEEE,
|
nuclear@39
|
192 and it may not be used for commercial purposes.
|
nuclear@39
|
193
|
nuclear@39
|
194 A somewhat less technical, more leisurely introduction to JPEG can be found in
|
nuclear@39
|
195 "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
|
nuclear@39
|
196 M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
|
nuclear@39
|
197 good explanations and example C code for a multitude of compression methods
|
nuclear@39
|
198 including JPEG. It is an excellent source if you are comfortable reading C
|
nuclear@39
|
199 code but don't know much about data compression in general. The book's JPEG
|
nuclear@39
|
200 sample code is far from industrial-strength, but when you are ready to look
|
nuclear@39
|
201 at a full implementation, you've got one here...
|
nuclear@39
|
202
|
nuclear@39
|
203 The best currently available description of JPEG is the textbook "JPEG Still
|
nuclear@39
|
204 Image Data Compression Standard" by William B. Pennebaker and Joan L.
|
nuclear@39
|
205 Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.
|
nuclear@39
|
206 Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG
|
nuclear@39
|
207 standards (DIS 10918-1 and draft DIS 10918-2).
|
nuclear@39
|
208 Although this is by far the most detailed and comprehensive exposition of
|
nuclear@39
|
209 JPEG publicly available, we point out that it is still missing an explanation
|
nuclear@39
|
210 of the most essential properties and algorithms of the underlying DCT
|
nuclear@39
|
211 technology.
|
nuclear@39
|
212 If you think that you know about DCT-based JPEG after reading this book,
|
nuclear@39
|
213 then you are in delusion. The real fundamentals and corresponding potential
|
nuclear@39
|
214 of DCT-based JPEG are not publicly known so far, and that is the reason for
|
nuclear@39
|
215 all the mistaken developments taking place in the image coding domain.
|
nuclear@39
|
216
|
nuclear@39
|
217 The original JPEG standard is divided into two parts, Part 1 being the actual
|
nuclear@39
|
218 specification, while Part 2 covers compliance testing methods. Part 1 is
|
nuclear@39
|
219 titled "Digital Compression and Coding of Continuous-tone Still Images,
|
nuclear@39
|
220 Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
|
nuclear@39
|
221 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of
|
nuclear@39
|
222 Continuous-tone Still Images, Part 2: Compliance testing" and has document
|
nuclear@39
|
223 numbers ISO/IEC IS 10918-2, ITU-T T.83.
|
nuclear@39
|
224 IJG JPEG 8 introduces an implementation of the JPEG SmartScale extension
|
nuclear@39
|
225 which is specified in a contributed document at ITU and ISO with title "ITU-T
|
nuclear@39
|
226 JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced Image Coding", April
|
nuclear@39
|
227 2006, Geneva, Switzerland. The latest version of the document is Revision 3.
|
nuclear@39
|
228
|
nuclear@39
|
229 The JPEG standard does not specify all details of an interchangeable file
|
nuclear@39
|
230 format. For the omitted details we follow the "JFIF" conventions, revision
|
nuclear@39
|
231 1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report
|
nuclear@39
|
232 and thus received a formal publication status. It is available as a free
|
nuclear@39
|
233 download in PDF format from
|
nuclear@39
|
234 http://www.ecma-international.org/publications/techreports/E-TR-098.htm.
|
nuclear@39
|
235 A PostScript version of the JFIF document is available at
|
nuclear@39
|
236 http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at
|
nuclear@39
|
237 http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures.
|
nuclear@39
|
238
|
nuclear@39
|
239 The TIFF 6.0 file format specification can be obtained by FTP from
|
nuclear@39
|
240 ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme
|
nuclear@39
|
241 found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
|
nuclear@39
|
242 IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
|
nuclear@39
|
243 Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
|
nuclear@39
|
244 (Compression tag 7). Copies of this Note can be obtained from
|
nuclear@39
|
245 http://www.ijg.org/files/. It is expected that the next revision
|
nuclear@39
|
246 of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
|
nuclear@39
|
247 Although IJG's own code does not support TIFF/JPEG, the free libtiff library
|
nuclear@39
|
248 uses our library to implement TIFF/JPEG per the Note.
|
nuclear@39
|
249
|
nuclear@39
|
250
|
nuclear@39
|
251 ARCHIVE LOCATIONS
|
nuclear@39
|
252 =================
|
nuclear@39
|
253
|
nuclear@39
|
254 The "official" archive site for this software is www.ijg.org.
|
nuclear@39
|
255 The most recent released version can always be found there in
|
nuclear@39
|
256 directory "files". This particular version will be archived as
|
nuclear@39
|
257 http://www.ijg.org/files/jpegsrc.v8c.tar.gz, and in Windows-compatible
|
nuclear@39
|
258 "zip" archive format as http://www.ijg.org/files/jpegsr8c.zip.
|
nuclear@39
|
259
|
nuclear@39
|
260 The JPEG FAQ (Frequently Asked Questions) article is a source of some
|
nuclear@39
|
261 general information about JPEG.
|
nuclear@39
|
262 It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
|
nuclear@39
|
263 and other news.answers archive sites, including the official news.answers
|
nuclear@39
|
264 archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
|
nuclear@39
|
265 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
|
nuclear@39
|
266 with body
|
nuclear@39
|
267 send usenet/news.answers/jpeg-faq/part1
|
nuclear@39
|
268 send usenet/news.answers/jpeg-faq/part2
|
nuclear@39
|
269
|
nuclear@39
|
270
|
nuclear@39
|
271 ACKNOWLEDGMENTS
|
nuclear@39
|
272 ===============
|
nuclear@39
|
273
|
nuclear@39
|
274 Thank to Juergen Bruder for providing me with a copy of the common DCT
|
nuclear@39
|
275 algorithm article, only to find out that I had come to the same result
|
nuclear@39
|
276 in a more direct and comprehensible way with a more generative approach.
|
nuclear@39
|
277
|
nuclear@39
|
278 Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
|
nuclear@39
|
279 ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.
|
nuclear@39
|
280
|
nuclear@39
|
281 Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
|
nuclear@39
|
282 Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.
|
nuclear@39
|
283
|
nuclear@39
|
284 Thank to John Korejwa and Massimo Ballerini for inviting me to
|
nuclear@39
|
285 fruitful consultations in Boston, MA and Milan, Italy.
|
nuclear@39
|
286
|
nuclear@39
|
287 Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
|
nuclear@39
|
288 Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel
|
nuclear@39
|
289 for corresponding business development.
|
nuclear@39
|
290
|
nuclear@39
|
291 Thank to Nico Zschach and Dirk Stelling of the technical support team
|
nuclear@39
|
292 at the Digital Images company in Halle for providing me with extra
|
nuclear@39
|
293 equipment for configuration tests.
|
nuclear@39
|
294
|
nuclear@39
|
295 Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
|
nuclear@39
|
296 communication about JPEG configuration in Sigma Photo Pro software.
|
nuclear@39
|
297
|
nuclear@39
|
298 Thank to Andrew Finkenstadt for hosting the ijg.org site.
|
nuclear@39
|
299
|
nuclear@39
|
300 Last but not least special thank to Thomas G. Lane for the original
|
nuclear@39
|
301 design and development of this singular software package.
|
nuclear@39
|
302
|
nuclear@39
|
303
|
nuclear@39
|
304 FILE FORMAT WARS
|
nuclear@39
|
305 ================
|
nuclear@39
|
306
|
nuclear@39
|
307 The ISO JPEG standards committee actually promotes different formats like
|
nuclear@39
|
308 "JPEG 2000" or "JPEG XR" which are incompatible with original DCT-based
|
nuclear@39
|
309 JPEG and which are based on faulty technologies. IJG therefore does not
|
nuclear@39
|
310 and will not support such momentary mistakes (see REFERENCES).
|
nuclear@39
|
311 We have little or no sympathy for the promotion of these formats. Indeed,
|
nuclear@39
|
312 one of the original reasons for developing this free software was to help
|
nuclear@39
|
313 force convergence on common, interoperable format standards for JPEG files.
|
nuclear@39
|
314 Don't use an incompatible file format!
|
nuclear@39
|
315 (In any case, our decoder will remain capable of reading existing JPEG
|
nuclear@39
|
316 image files indefinitely.)
|
nuclear@39
|
317
|
nuclear@39
|
318
|
nuclear@39
|
319 TO DO
|
nuclear@39
|
320 =====
|
nuclear@39
|
321
|
nuclear@39
|
322 Version 8 is the first release of a new generation JPEG standard
|
nuclear@39
|
323 to overcome the limitations of the original JPEG specification.
|
nuclear@39
|
324 More features are being prepared for coming releases...
|
nuclear@39
|
325
|
nuclear@39
|
326 Please send bug reports, offers of help, etc. to jpeg-info@uc.ag.
|