[LIBJPEG]
[reactos.git] / reactos / dll / 3rdparty / libjpeg / README
1 The Independent JPEG Group's JPEG software
2 ==========================================
3
4 README for release 9b of 17-Jan-2016
5 ====================================
6
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.
10
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.
15
16 IJG is not affiliated with the ISO/IEC JTC1/SC29/WG1 standards committee
17 (previously known as JPEG, together with ITU-T SG16).
18
19
20 DOCUMENTATION ROADMAP
21 =====================
22
23 This file contains the following sections:
24
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.
32
33 Other documentation files in the distribution are:
34
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.
48
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.
52
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.
56
57
58 OVERVIEW
59 ========
60
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 grayscale images.
64
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.
70
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.
75
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.
82
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.
86
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.
93
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.
97
98
99 LEGAL ISSUES
100 ============
101
102 In plain English:
103
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.
110
111 In legalese:
112
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.
117
118 This software is copyright (C) 1991-2016, Thomas G. Lane, Guido Vollbeding.
119 All Rights Reserved except as specified below.
120
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.
134
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.
138
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".
143
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.
147
148
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.
154
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.
161
162
163 REFERENCES
164 ==========
165
166 We recommend reading one or more of these references before trying to
167 understand the innards of the JPEG software.
168
169 The best short technical introduction to the JPEG compression algorithm is
170 Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
171 Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
172 (Adjacent articles in that issue discuss MPEG motion picture compression,
173 applications of JPEG, and related topics.) If you don't have the CACM issue
174 handy, a PDF file containing a revised version of Wallace's article is
175 available at http://www.ijg.org/files/Wallace.JPEG.pdf. The file (actually
176 a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
177 omits the sample images that appeared in CACM, but it includes corrections
178 and some added material. Note: the Wallace article is copyright ACM and IEEE,
179 and it may not be used for commercial purposes.
180
181 A somewhat less technical, more leisurely introduction to JPEG can be found in
182 "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
183 M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
184 good explanations and example C code for a multitude of compression methods
185 including JPEG. It is an excellent source if you are comfortable reading C
186 code but don't know much about data compression in general. The book's JPEG
187 sample code is far from industrial-strength, but when you are ready to look
188 at a full implementation, you've got one here...
189
190 The best currently available description of JPEG is the textbook "JPEG Still
191 Image Data Compression Standard" by William B. Pennebaker and Joan L.
192 Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.
193 Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG
194 standards (DIS 10918-1 and draft DIS 10918-2).
195 Although this is by far the most detailed and comprehensive exposition of
196 JPEG publicly available, we point out that it is still missing an explanation
197 of the most essential properties and algorithms of the underlying DCT
198 technology.
199 If you think that you know about DCT-based JPEG after reading this book,
200 then you are in delusion. The real fundamentals and corresponding potential
201 of DCT-based JPEG are not publicly known so far, and that is the reason for
202 all the mistaken developments taking place in the image coding domain.
203
204 The original JPEG standard is divided into two parts, Part 1 being the actual
205 specification, while Part 2 covers compliance testing methods. Part 1 is
206 titled "Digital Compression and Coding of Continuous-tone Still Images,
207 Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
208 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of
209 Continuous-tone Still Images, Part 2: Compliance testing" and has document
210 numbers ISO/IEC IS 10918-2, ITU-T T.83.
211 IJG JPEG 8 introduced an implementation of the JPEG SmartScale extension
212 which is specified in two documents: A contributed document at ITU and ISO
213 with title "ITU-T JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced
214 Image Coding", April 2006, Geneva, Switzerland. The latest version of this
215 document is Revision 3. And a contributed document ISO/IEC JTC1/SC29/WG1 N
216 5799 with title "Evolution of JPEG", June/July 2011, Berlin, Germany.
217 IJG JPEG 9 introduces a reversible color transform for improved lossless
218 compression which is described in a contributed document ISO/IEC JTC1/SC29/
219 WG1 N 6080 with title "JPEG 9 Lossless Coding", June/July 2012, Paris,
220 France.
221
222 The JPEG standard does not specify all details of an interchangeable file
223 format. For the omitted details we follow the "JFIF" conventions, version 2.
224 JFIF version 1 has been adopted as Recommendation ITU-T T.871 (05/2011) :
225 Information technology - Digital compression and coding of continuous-tone
226 still images: JPEG File Interchange Format (JFIF). It is available as a
227 free download in PDF file format from http://www.itu.int/rec/T-REC-T.871.
228 A PDF file of the older JFIF document is available at
229 http://www.w3.org/Graphics/JPEG/jfif3.pdf.
230
231 The TIFF 6.0 file format specification can be obtained by FTP from
232 ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme
233 found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
234 IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
235 Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
236 (Compression tag 7). Copies of this Note can be obtained from
237 http://www.ijg.org/files/. It is expected that the next revision
238 of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
239 Although IJG's own code does not support TIFF/JPEG, the free libtiff library
240 uses our library to implement TIFF/JPEG per the Note.
241
242
243 ARCHIVE LOCATIONS
244 =================
245
246 The "official" archive site for this software is www.ijg.org.
247 The most recent released version can always be found there in
248 directory "files". This particular version will be archived as
249 http://www.ijg.org/files/jpegsrc.v9b.tar.gz, and in Windows-compatible
250 "zip" archive format as http://www.ijg.org/files/jpegsr9b.zip.
251
252 The JPEG FAQ (Frequently Asked Questions) article is a source of some
253 general information about JPEG.
254 It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
255 and other news.answers archive sites, including the official news.answers
256 archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
257 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
258 with body
259 send usenet/news.answers/jpeg-faq/part1
260 send usenet/news.answers/jpeg-faq/part2
261
262
263 ACKNOWLEDGMENTS
264 ===============
265
266 Thank to Juergen Bruder for providing me with a copy of the common DCT
267 algorithm article, only to find out that I had come to the same result
268 in a more direct and comprehensible way with a more generative approach.
269
270 Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
271 ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.
272
273 Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
274 Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.
275
276 Thank to Thomas Richter and Daniel Lee for inviting me to the
277 ISO/IEC JTC1/SC29/WG1 (previously known as JPEG, together with ITU-T SG16)
278 meeting in Berlin, Germany.
279
280 Thank to John Korejwa and Massimo Ballerini for inviting me to
281 fruitful consultations in Boston, MA and Milan, Italy.
282
283 Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
284 Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel
285 for corresponding business development.
286
287 Thank to Nico Zschach and Dirk Stelling of the technical support team
288 at the Digital Images company in Halle for providing me with extra
289 equipment for configuration tests.
290
291 Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
292 communication about JPEG configuration in Sigma Photo Pro software.
293
294 Thank to Andrew Finkenstadt for hosting the ijg.org site.
295
296 Last but not least special thank to Thomas G. Lane for the original
297 design and development of this singular software package.
298
299
300 FILE FORMAT WARS
301 ================
302
303 The ISO/IEC JTC1/SC29/WG1 standards committee (previously known as JPEG,
304 together with ITU-T SG16) currently promotes different formats containing
305 the name "JPEG" which is misleading because these formats are incompatible
306 with original DCT-based JPEG and are based on faulty technologies.
307 IJG therefore does not and will not support such momentary mistakes
308 (see REFERENCES).
309 There exist also distributions under the name "OpenJPEG" promoting such
310 kind of formats which is misleading because they don't support original
311 JPEG images.
312 We have no sympathy for the promotion of inferior formats. Indeed, one of
313 the original reasons for developing this free software was to help force
314 convergence on common, interoperable format standards for JPEG files.
315 Don't use an incompatible file format!
316 (In any case, our decoder will remain capable of reading existing JPEG
317 image files indefinitely.)
318
319 The ISO committee pretends to be "responsible for the popular JPEG" in their
320 public reports which is not true because they don't respond to actual
321 requirements for the maintenance of the original JPEG specification.
322 Furthermore, the ISO committee pretends to "ensure interoperability" with
323 their standards which is not true because their "standards" support only
324 application-specific and proprietary use cases and contain mathematically
325 incorrect code.
326
327 There are currently different distributions in circulation containing the
328 name "libjpeg" which is misleading because they don't have the features and
329 are incompatible with formats supported by actual IJG libjpeg distributions.
330 One of those fakes is released by members of the ISO committee and just uses
331 the name of libjpeg for misdirection of people, similar to the abuse of the
332 name JPEG as described above, while having nothing in common with actual IJG
333 libjpeg distributions and containing mathematically incorrect code.
334 The other one claims to be a "derivative" or "fork" of the original libjpeg,
335 but violates the license conditions as described under LEGAL ISSUES above
336 and violates basic C programming properties.
337 We have no sympathy for the release of misleading, incorrect and illegal
338 distributions derived from obsolete code bases.
339 Don't use an obsolete code base!
340
341 According to the UCC (Uniform Commercial Code) law, IJG has the lawful and
342 legal right to foreclose on certain standardization bodies and other
343 institutions or corporations that knowingly perform substantial and
344 systematic deceptive acts and practices, fraud, theft, and damaging of the
345 value of the people of this planet without their knowing, willing and
346 intentional consent.
347 The titles, ownership, and rights of these institutions and all their assets
348 are now duly secured and held in trust for the free people of this planet.
349 People of the planet, on every country, may have a financial interest in
350 the assets of these former principals, agents, and beneficiaries of the
351 foreclosed institutions and corporations.
352 IJG asserts what is: that each man, woman, and child has unalienable value
353 and rights granted and deposited in them by the Creator and not any one of
354 the people is subordinate to any artificial principality, corporate fiction
355 or the special interest of another without their appropriate knowing,
356 willing and intentional consent made by contract or accommodation agreement.
357 IJG expresses that which already was.
358 The people have already determined and demanded that public administration
359 entities, national governments, and their supporting judicial systems must
360 be fully transparent, accountable, and liable.
361 IJG has secured the value for all concerned free people of the planet.
362
363 A partial list of foreclosed institutions and corporations ("Hall of Shame")
364 is currently prepared and will be published later.
365
366
367 TO DO
368 =====
369
370 Version 9 is the second release of a new generation JPEG standard
371 to overcome the limitations of the original JPEG specification,
372 and is the first true source reference JPEG codec.
373 More features are being prepared for coming releases...
374
375 Please send bug reports, offers of help, etc. to jpeg-info@jpegclub.org.