[reactos.git] / reactos / dll / 3rdparty / libjpeg / README
1 The Independent JPEG Group's JPEG software
2 ==========================================
4 README for release 9a of 19-Jan-2014
5 ====================================
7 This distribution contains the ninth public release of the Independent JPEG
8 Group's free JPEG software. You are welcome to redistribute this software and
9 to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.
11 This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone,
12 Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson,
13 Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,
14 and other members of the Independent JPEG Group.
16 IJG is not affiliated with the ISO/IEC JTC1/SC29/WG1 standards committee
17 (previously known as JPEG, together with ITU-T SG16).
21 =====================
23 This file contains the following sections:
25 OVERVIEW General description of JPEG and the IJG software.
26 LEGAL ISSUES Copyright, lack of warranty, terms of distribution.
27 REFERENCES Where to learn more about JPEG.
28 ARCHIVE LOCATIONS Where to find newer versions of this software.
29 ACKNOWLEDGMENTS Special thanks.
30 FILE FORMAT WARS Software *not* to get.
31 TO DO Plans for future IJG releases.
33 Other documentation files in the distribution are:
35 User documentation:
36 install.txt How to configure and install the IJG software.
37 usage.txt Usage instructions for cjpeg, djpeg, jpegtran,
38 rdjpgcom, and wrjpgcom.
39 *.1 Unix-style man pages for programs (same info as usage.txt).
40 wizard.txt Advanced usage instructions for JPEG wizards only.
41 change.log Version-to-version change highlights.
42 Programmer and internal documentation:
43 libjpeg.txt How to use the JPEG library in your own programs.
44 example.c Sample code for calling the JPEG library.
45 structure.txt Overview of the JPEG library's internal structure.
46 filelist.txt Road map of IJG files.
47 coderules.txt Coding style rules --- please read if you contribute code.
49 Please read at least the files install.txt and usage.txt. Some information
50 can also be found in the JPEG FAQ (Frequently Asked Questions) article. See
51 ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.
53 If you want to understand how the JPEG code works, we suggest reading one or
54 more of the REFERENCES, then looking at the documentation files (in roughly
55 the order listed) before diving into the code.
59 ========
61 This package contains C software to implement JPEG image encoding, decoding,
62 and transcoding. JPEG (pronounced "jay-peg") is a standardized compression
63 method for full-color and gray-scale images.
65 This software implements JPEG baseline, extended-sequential, and progressive
66 compression processes. Provision is made for supporting all variants of these
67 processes, although some uncommon parameter settings aren't implemented yet.
68 We have made no provision for supporting the hierarchical or lossless
69 processes defined in the standard.
71 We provide a set of library routines for reading and writing JPEG image files,
72 plus two sample applications "cjpeg" and "djpeg", which use the library to
73 perform conversion between JPEG and some other popular image file formats.
74 The library is intended to be reused in other applications.
76 In order to support file conversion and viewing software, we have included
77 considerable functionality beyond the bare JPEG coding/decoding capability;
78 for example, the color quantization modules are not strictly part of JPEG
79 decoding, but they are essential for output to colormapped file formats or
80 colormapped displays. These extra functions can be compiled out of the
81 library if not required for a particular application.
83 We have also included "jpegtran", a utility for lossless transcoding between
84 different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple
85 applications for inserting and extracting textual comments in JFIF files.
87 The emphasis in designing this software has been on achieving portability and
88 flexibility, while also making it fast enough to be useful. In particular,
89 the software is not intended to be read as a tutorial on JPEG. (See the
90 REFERENCES section for introductory material.) Rather, it is intended to
91 be reliable, portable, industrial-strength code. We do not claim to have
92 achieved that goal in every aspect of the software, but we strive for it.
94 We welcome the use of this software as a component of commercial products.
95 No royalty is required, but we do ask for an acknowledgement in product
96 documentation, as described under LEGAL ISSUES.
100 ============
102 In plain English:
104 1. We don't promise that this software works. (But if you find any bugs,
105 please let us know!)
106 2. You can use this software for whatever you want. You don't have to pay us.
107 3. You may not pretend that you wrote this software. If you use it in a
108 program, you must acknowledge somewhere in your documentation that
109 you've used the IJG code.
111 In legalese:
113 The authors make NO WARRANTY or representation, either express or implied,
114 with respect to this software, its quality, accuracy, merchantability, or
115 fitness for a particular purpose. This software is provided "AS IS", and you,
116 its user, assume the entire risk as to its quality and accuracy.
118 This software is copyright (C) 1991-2014, Thomas G. Lane, Guido Vollbeding.
119 All Rights Reserved except as specified below.
121 Permission is hereby granted to use, copy, modify, and distribute this
122 software (or portions thereof) for any purpose, without fee, subject to these
123 conditions:
124 (1) If any part of the source code for this software is distributed, then this
125 README file must be included, with this copyright and no-warranty notice
126 unaltered; and any additions, deletions, or changes to the original files
127 must be clearly indicated in accompanying documentation.
128 (2) If only executable code is distributed, then the accompanying
129 documentation must state that "this software is based in part on the work of
130 the Independent JPEG Group".
131 (3) Permission for use of this software is granted only if the user accepts
132 full responsibility for any undesirable consequences; the authors accept
133 NO LIABILITY for damages of any kind.
135 These conditions apply to any software derived from or based on the IJG code,
136 not just to the unmodified library. If you use our work, you ought to
137 acknowledge us.
139 Permission is NOT granted for the use of any IJG author's name or company name
140 in advertising or publicity relating to this software or products derived from
141 it. This software may be referred to only as "the Independent JPEG Group's
142 software".
144 We specifically permit and encourage the use of this software as the basis of
145 commercial products, provided that all warranty or liability claims are
146 assumed by the product vendor.
149 The Unix configuration script "configure" was produced with GNU Autoconf.
150 It is copyright by the Free Software Foundation but is freely distributable.
151 The same holds for its supporting scripts (config.guess, config.sub,
152 ltmain.sh). Another support script, install-sh, is copyright by X Consortium
153 but is also freely distributable.
155 The IJG distribution formerly included code to read and write GIF files.
156 To avoid entanglement with the Unisys LZW patent (now expired), GIF reading
157 support has been removed altogether, and the GIF writer has been simplified
158 to produce "uncompressed GIFs". This technique does not use the LZW
159 algorithm; the resulting GIF files are larger than usual, but are readable
160 by all standard GIF decoders.
162 We are required to state that
163 "The Graphics Interchange Format(c) is the Copyright property of
164 CompuServe Incorporated. GIF(sm) is a Service Mark property of
165 CompuServe Incorporated."
169 ==========
171 We recommend reading one or more of these references before trying to
172 understand the innards of the JPEG software.
174 The best short technical introduction to the JPEG compression algorithm is
175 Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
176 Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
177 (Adjacent articles in that issue discuss MPEG motion picture compression,
178 applications of JPEG, and related topics.) If you don't have the CACM issue
179 handy, a PostScript file containing a revised version of Wallace's article is
180 available at http://www.ijg.org/files/wallace.ps.gz. The file (actually
181 a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
182 omits the sample images that appeared in CACM, but it includes corrections
183 and some added material. Note: the Wallace article is copyright ACM and IEEE,
184 and it may not be used for commercial purposes.
186 A somewhat less technical, more leisurely introduction to JPEG can be found in
187 "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
188 M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
189 good explanations and example C code for a multitude of compression methods
190 including JPEG. It is an excellent source if you are comfortable reading C
191 code but don't know much about data compression in general. The book's JPEG
192 sample code is far from industrial-strength, but when you are ready to look
193 at a full implementation, you've got one here...
195 The best currently available description of JPEG is the textbook "JPEG Still
196 Image Data Compression Standard" by William B. Pennebaker and Joan L.
197 Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.
198 Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG
199 standards (DIS 10918-1 and draft DIS 10918-2).
200 Although this is by far the most detailed and comprehensive exposition of
201 JPEG publicly available, we point out that it is still missing an explanation
202 of the most essential properties and algorithms of the underlying DCT
203 technology.
204 If you think that you know about DCT-based JPEG after reading this book,
205 then you are in delusion. The real fundamentals and corresponding potential
206 of DCT-based JPEG are not publicly known so far, and that is the reason for
207 all the mistaken developments taking place in the image coding domain.
209 The original JPEG standard is divided into two parts, Part 1 being the actual
210 specification, while Part 2 covers compliance testing methods. Part 1 is
211 titled "Digital Compression and Coding of Continuous-tone Still Images,
212 Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
213 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of
214 Continuous-tone Still Images, Part 2: Compliance testing" and has document
215 numbers ISO/IEC IS 10918-2, ITU-T T.83.
216 IJG JPEG 8 introduced an implementation of the JPEG SmartScale extension
217 which is specified in two documents: A contributed document at ITU and ISO
218 with title "ITU-T JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced
219 Image Coding", April 2006, Geneva, Switzerland. The latest version of this
220 document is Revision 3. And a contributed document ISO/IEC JTC1/SC29/WG1 N
221 5799 with title "Evolution of JPEG", June/July 2011, Berlin, Germany.
222 IJG JPEG 9 introduces a reversible color transform for improved lossless
223 compression which is described in a contributed document ISO/IEC JTC1/SC29/
224 WG1 N 6080 with title "JPEG 9 Lossless Coding", June/July 2012, Paris,
225 France.
227 The JPEG standard does not specify all details of an interchangeable file
228 format. For the omitted details we follow the "JFIF" conventions, revision
229 1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report
230 and thus received a formal publication status. It is available as a free
231 download in PDF format from
232 http://www.ecma-international.org/publications/techreports/E-TR-098.htm.
233 A PostScript version of the JFIF document is available at
234 http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at
235 http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures.
237 The TIFF 6.0 file format specification can be obtained by FTP from
238 ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme
239 found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
240 IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
241 Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
242 (Compression tag 7). Copies of this Note can be obtained from
243 http://www.ijg.org/files/. It is expected that the next revision
244 of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
245 Although IJG's own code does not support TIFF/JPEG, the free libtiff library
246 uses our library to implement TIFF/JPEG per the Note.
250 =================
252 The "official" archive site for this software is www.ijg.org.
253 The most recent released version can always be found there in
254 directory "files". This particular version will be archived as
255 http://www.ijg.org/files/jpegsrc.v9a.tar.gz, and in Windows-compatible
256 "zip" archive format as http://www.ijg.org/files/jpegsr9a.zip.
258 The JPEG FAQ (Frequently Asked Questions) article is a source of some
259 general information about JPEG.
260 It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
261 and other news.answers archive sites, including the official news.answers
262 archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
263 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
264 with body
265 send usenet/news.answers/jpeg-faq/part1
266 send usenet/news.answers/jpeg-faq/part2
270 ===============
272 Thank to Juergen Bruder for providing me with a copy of the common DCT
273 algorithm article, only to find out that I had come to the same result
274 in a more direct and comprehensible way with a more generative approach.
276 Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
277 ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.
279 Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
280 Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.
282 Thank to Thomas Richter and Daniel Lee for inviting me to the
283 ISO/IEC JTC1/SC29/WG1 (previously known as JPEG, together with ITU-T SG16)
284 meeting in Berlin, Germany.
286 Thank to John Korejwa and Massimo Ballerini for inviting me to
287 fruitful consultations in Boston, MA and Milan, Italy.
289 Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
290 Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel
291 for corresponding business development.
293 Thank to Nico Zschach and Dirk Stelling of the technical support team
294 at the Digital Images company in Halle for providing me with extra
295 equipment for configuration tests.
297 Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
298 communication about JPEG configuration in Sigma Photo Pro software.
300 Thank to Andrew Finkenstadt for hosting the ijg.org site.
302 Last but not least special thank to Thomas G. Lane for the original
303 design and development of this singular software package.
307 ================
309 The ISO/IEC JTC1/SC29/WG1 standards committee (previously known as JPEG,
310 together with ITU-T SG16) currently promotes different formats containing
311 the name "JPEG" which is misleading because these formats are incompatible
312 with original DCT-based JPEG and are based on faulty technologies.
313 IJG therefore does not and will not support such momentary mistakes
314 (see REFERENCES).
315 There exist also distributions under the name "OpenJPEG" promoting such
316 kind of formats which is misleading because they don't support original
317 JPEG images.
318 We have no sympathy for the promotion of inferior formats. Indeed, one of
319 the original reasons for developing this free software was to help force
320 convergence on common, interoperable format standards for JPEG files.
321 Don't use an incompatible file format!
322 (In any case, our decoder will remain capable of reading existing JPEG
323 image files indefinitely.)
325 The ISO committee pretends to be "responsible for the popular JPEG" in their
326 public reports which is not true because they don't respond to actual
327 requirements for the maintenance of the original JPEG specification.
328 Furthermore, the ISO committee pretends to "ensure interoperability" with
329 their standards which is not true because their "standards" support only
330 application-specific and proprietary use cases and contain mathematically
331 incorrect code.
333 There are currently different distributions in circulation containing the
334 name "libjpeg" which is misleading because they don't have the features and
335 are incompatible with formats supported by actual IJG libjpeg distributions.
336 One of those fakes is released by members of the ISO committee and just uses
337 the name of libjpeg for misdirection of people, similar to the abuse of the
338 name JPEG as described above, while having nothing in common with actual IJG
339 libjpeg distributions and containing mathematically incorrect code.
340 The other one claims to be a "derivative" or "fork" of the original libjpeg,
341 but violates the license conditions as described under LEGAL ISSUES above
342 and violates basic C programming properties.
343 We have no sympathy for the release of misleading, incorrect and illegal
344 distributions derived from obsolete code bases.
345 Don't use an obsolete code base!
347 According to the UCC (Uniform Commercial Code) law, IJG has the lawful and
348 legal right to foreclose on certain standardization bodies and other
349 institutions or corporations that knowingly perform substantial and
350 systematic deceptive acts and practices, fraud, theft, and damaging of the
351 value of the people of this planet without their knowing, willing and
352 intentional consent.
353 The titles, ownership, and rights of these institutions and all their assets
354 are now duly secured and held in trust for the free people of this planet.
355 People of the planet, on every country, may have a financial interest in
356 the assets of these former principals, agents, and beneficiaries of the
357 foreclosed institutions and corporations.
358 IJG asserts what is: that each man, woman, and child has unalienable value
359 and rights granted and deposited in them by the Creator and not any one of
360 the people is subordinate to any artificial principality, corporate fiction
361 or the special interest of another without their appropriate knowing,
362 willing and intentional consent made by contract or accommodation agreement.
363 IJG expresses that which already was.
364 The people have already determined and demanded that public administration
365 entities, national governments, and their supporting judicial systems must
366 be fully transparent, accountable, and liable.
367 IJG has secured the value for all concerned free people of the planet.
369 A partial list of foreclosed institutions and corporations ("Hall of Shame")
370 is currently prepared and will be published later.
373 TO DO
374 =====
376 Version 9 is the second release of a new generation JPEG standard
377 to overcome the limitations of the original JPEG specification,
378 and is the first true source reference JPEG codec.
379 More features are being prepared for coming releases...
381 Please send bug reports, offers of help, etc. to jpeg-info@jpegclub.org.