1 The Independent JPEG Group's JPEG software
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2 ==========================================
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4 README for release 8d of 15-Jan-2012
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5 ====================================
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7 This distribution contains the eighth public release of the Independent JPEG
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8 Group's free JPEG software. You are welcome to redistribute this software and
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9 to use it for any purpose, subject to the conditions under LEGAL ISSUES, below.
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11 This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone,
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12 Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson,
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13 Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,
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14 and other members of the Independent JPEG Group.
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16 IJG is not affiliated with the ISO/IEC JTC1/SC29/WG1 standards committee
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17 (also known as JPEG, together with ITU-T SG16).
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20 DOCUMENTATION ROADMAP
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21 =====================
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23 This file contains the following sections:
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25 OVERVIEW General description of JPEG and the IJG software.
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26 LEGAL ISSUES Copyright, lack of warranty, terms of distribution.
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27 REFERENCES Where to learn more about JPEG.
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28 ARCHIVE LOCATIONS Where to find newer versions of this software.
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29 ACKNOWLEDGMENTS Special thanks.
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30 FILE FORMAT WARS Software *not* to get.
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31 TO DO Plans for future IJG releases.
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33 Other documentation files in the distribution are:
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36 install.txt How to configure and install the IJG software.
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37 usage.txt Usage instructions for cjpeg, djpeg, jpegtran,
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38 rdjpgcom, and wrjpgcom.
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39 *.1 Unix-style man pages for programs (same info as usage.txt).
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40 wizard.txt Advanced usage instructions for JPEG wizards only.
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41 change.log Version-to-version change highlights.
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42 Programmer and internal documentation:
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43 libjpeg.txt How to use the JPEG library in your own programs.
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44 example.c Sample code for calling the JPEG library.
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45 structure.txt Overview of the JPEG library's internal structure.
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46 filelist.txt Road map of IJG files.
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47 coderules.txt Coding style rules --- please read if you contribute code.
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49 Please read at least the files install.txt and usage.txt. Some information
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50 can also be found in the JPEG FAQ (Frequently Asked Questions) article. See
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51 ARCHIVE LOCATIONS below to find out where to obtain the FAQ article.
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53 If you want to understand how the JPEG code works, we suggest reading one or
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54 more of the REFERENCES, then looking at the documentation files (in roughly
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55 the order listed) before diving into the code.
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61 This package contains C software to implement JPEG image encoding, decoding,
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62 and transcoding. JPEG (pronounced "jay-peg") is a standardized compression
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63 method for full-color and gray-scale images.
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65 This software implements JPEG baseline, extended-sequential, and progressive
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66 compression processes. Provision is made for supporting all variants of these
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67 processes, although some uncommon parameter settings aren't implemented yet.
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68 We have made no provision for supporting the hierarchical or lossless
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69 processes defined in the standard.
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71 We provide a set of library routines for reading and writing JPEG image files,
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72 plus two sample applications "cjpeg" and "djpeg", which use the library to
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73 perform conversion between JPEG and some other popular image file formats.
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74 The library is intended to be reused in other applications.
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76 In order to support file conversion and viewing software, we have included
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77 considerable functionality beyond the bare JPEG coding/decoding capability;
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78 for example, the color quantization modules are not strictly part of JPEG
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79 decoding, but they are essential for output to colormapped file formats or
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80 colormapped displays. These extra functions can be compiled out of the
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81 library if not required for a particular application.
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83 We have also included "jpegtran", a utility for lossless transcoding between
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84 different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple
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85 applications for inserting and extracting textual comments in JFIF files.
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87 The emphasis in designing this software has been on achieving portability and
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88 flexibility, while also making it fast enough to be useful. In particular,
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89 the software is not intended to be read as a tutorial on JPEG. (See the
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90 REFERENCES section for introductory material.) Rather, it is intended to
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91 be reliable, portable, industrial-strength code. We do not claim to have
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92 achieved that goal in every aspect of the software, but we strive for it.
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94 We welcome the use of this software as a component of commercial products.
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95 No royalty is required, but we do ask for an acknowledgement in product
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96 documentation, as described under LEGAL ISSUES.
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104 1. We don't promise that this software works. (But if you find any bugs,
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105 please let us know!)
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106 2. You can use this software for whatever you want. You don't have to pay us.
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107 3. You may not pretend that you wrote this software. If you use it in a
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108 program, you must acknowledge somewhere in your documentation that
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109 you've used the IJG code.
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113 The authors make NO WARRANTY or representation, either express or implied,
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114 with respect to this software, its quality, accuracy, merchantability, or
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115 fitness for a particular purpose. This software is provided "AS IS", and you,
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116 its user, assume the entire risk as to its quality and accuracy.
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118 This software is copyright (C) 1991-2012, Thomas G. Lane, Guido Vollbeding.
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119 All Rights Reserved except as specified below.
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121 Permission is hereby granted to use, copy, modify, and distribute this
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122 software (or portions thereof) for any purpose, without fee, subject to these
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124 (1) If any part of the source code for this software is distributed, then this
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125 README file must be included, with this copyright and no-warranty notice
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126 unaltered; and any additions, deletions, or changes to the original files
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127 must be clearly indicated in accompanying documentation.
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128 (2) If only executable code is distributed, then the accompanying
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129 documentation must state that "this software is based in part on the work of
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130 the Independent JPEG Group".
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131 (3) Permission for use of this software is granted only if the user accepts
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132 full responsibility for any undesirable consequences; the authors accept
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133 NO LIABILITY for damages of any kind.
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135 These conditions apply to any software derived from or based on the IJG code,
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136 not just to the unmodified library. If you use our work, you ought to
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139 Permission is NOT granted for the use of any IJG author's name or company name
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140 in advertising or publicity relating to this software or products derived from
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141 it. This software may be referred to only as "the Independent JPEG Group's
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144 We specifically permit and encourage the use of this software as the basis of
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145 commercial products, provided that all warranty or liability claims are
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146 assumed by the product vendor.
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149 ansi2knr.c is included in this distribution by permission of L. Peter Deutsch,
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150 sole proprietor of its copyright holder, Aladdin Enterprises of Menlo Park, CA.
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151 ansi2knr.c is NOT covered by the above copyright and conditions, but instead
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152 by the usual distribution terms of the Free Software Foundation; principally,
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153 that you must include source code if you redistribute it. (See the file
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154 ansi2knr.c for full details.) However, since ansi2knr.c is not needed as part
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155 of any program generated from the IJG code, this does not limit you more than
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156 the foregoing paragraphs do.
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158 The Unix configuration script "configure" was produced with GNU Autoconf.
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159 It is copyright by the Free Software Foundation but is freely distributable.
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160 The same holds for its supporting scripts (config.guess, config.sub,
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161 ltmain.sh). Another support script, install-sh, is copyright by X Consortium
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162 but is also freely distributable.
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164 The IJG distribution formerly included code to read and write GIF files.
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165 To avoid entanglement with the Unisys LZW patent, GIF reading support has
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166 been removed altogether, and the GIF writer has been simplified to produce
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167 "uncompressed GIFs". This technique does not use the LZW algorithm; the
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168 resulting GIF files are larger than usual, but are readable by all standard
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171 We are required to state that
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172 "The Graphics Interchange Format(c) is the Copyright property of
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173 CompuServe Incorporated. GIF(sm) is a Service Mark property of
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174 CompuServe Incorporated."
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180 We recommend reading one or more of these references before trying to
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181 understand the innards of the JPEG software.
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183 The best short technical introduction to the JPEG compression algorithm is
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184 Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
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185 Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.
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186 (Adjacent articles in that issue discuss MPEG motion picture compression,
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187 applications of JPEG, and related topics.) If you don't have the CACM issue
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188 handy, a PostScript file containing a revised version of Wallace's article is
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189 available at http://www.ijg.org/files/wallace.ps.gz. The file (actually
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190 a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
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191 omits the sample images that appeared in CACM, but it includes corrections
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192 and some added material. Note: the Wallace article is copyright ACM and IEEE,
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193 and it may not be used for commercial purposes.
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195 A somewhat less technical, more leisurely introduction to JPEG can be found in
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196 "The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published by
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197 M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1. This book provides
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198 good explanations and example C code for a multitude of compression methods
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199 including JPEG. It is an excellent source if you are comfortable reading C
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200 code but don't know much about data compression in general. The book's JPEG
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201 sample code is far from industrial-strength, but when you are ready to look
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202 at a full implementation, you've got one here...
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204 The best currently available description of JPEG is the textbook "JPEG Still
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205 Image Data Compression Standard" by William B. Pennebaker and Joan L.
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206 Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.
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207 Price US$59.95, 638 pp. The book includes the complete text of the ISO JPEG
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208 standards (DIS 10918-1 and draft DIS 10918-2).
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209 Although this is by far the most detailed and comprehensive exposition of
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210 JPEG publicly available, we point out that it is still missing an explanation
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211 of the most essential properties and algorithms of the underlying DCT
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213 If you think that you know about DCT-based JPEG after reading this book,
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214 then you are in delusion. The real fundamentals and corresponding potential
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215 of DCT-based JPEG are not publicly known so far, and that is the reason for
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216 all the mistaken developments taking place in the image coding domain.
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218 The original JPEG standard is divided into two parts, Part 1 being the actual
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219 specification, while Part 2 covers compliance testing methods. Part 1 is
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220 titled "Digital Compression and Coding of Continuous-tone Still Images,
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221 Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
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222 10918-1, ITU-T T.81. Part 2 is titled "Digital Compression and Coding of
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223 Continuous-tone Still Images, Part 2: Compliance testing" and has document
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224 numbers ISO/IEC IS 10918-2, ITU-T T.83.
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225 IJG JPEG 8 introduces an implementation of the JPEG SmartScale extension
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226 which is specified in two documents: A contributed document at ITU and ISO
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227 with title "ITU-T JPEG-Plus Proposal for Extending ITU-T T.81 for Advanced
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228 Image Coding", April 2006, Geneva, Switzerland. The latest version of this
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229 document is Revision 3. And a contributed document ISO/IEC JTC1/SC29/WG1 N
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230 5799 with title "Evolution of JPEG", June/July 2011, Berlin, Germany.
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232 The JPEG standard does not specify all details of an interchangeable file
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233 format. For the omitted details we follow the "JFIF" conventions, revision
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234 1.02. JFIF 1.02 has been adopted as an Ecma International Technical Report
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235 and thus received a formal publication status. It is available as a free
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236 download in PDF format from
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237 http://www.ecma-international.org/publications/techreports/E-TR-098.htm.
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238 A PostScript version of the JFIF document is available at
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239 http://www.ijg.org/files/jfif.ps.gz. There is also a plain text version at
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240 http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures.
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242 The TIFF 6.0 file format specification can be obtained by FTP from
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243 ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz. The JPEG incorporation scheme
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244 found in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.
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245 IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).
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246 Instead, we recommend the JPEG design proposed by TIFF Technical Note #2
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247 (Compression tag 7). Copies of this Note can be obtained from
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248 http://www.ijg.org/files/. It is expected that the next revision
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249 of the TIFF spec will replace the 6.0 JPEG design with the Note's design.
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250 Although IJG's own code does not support TIFF/JPEG, the free libtiff library
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251 uses our library to implement TIFF/JPEG per the Note.
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257 The "official" archive site for this software is www.ijg.org.
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258 The most recent released version can always be found there in
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259 directory "files". This particular version will be archived as
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260 http://www.ijg.org/files/jpegsrc.v8d.tar.gz, and in Windows-compatible
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261 "zip" archive format as http://www.ijg.org/files/jpegsr8d.zip.
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263 The JPEG FAQ (Frequently Asked Questions) article is a source of some
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264 general information about JPEG.
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265 It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
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266 and other news.answers archive sites, including the official news.answers
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267 archive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.
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268 If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.edu
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270 send usenet/news.answers/jpeg-faq/part1
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271 send usenet/news.answers/jpeg-faq/part2
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277 Thank to Juergen Bruder for providing me with a copy of the common DCT
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278 algorithm article, only to find out that I had come to the same result
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279 in a more direct and comprehensible way with a more generative approach.
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281 Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to the
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282 ITU JPEG (Study Group 16) meeting in Geneva, Switzerland.
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284 Thank to Thomas Wiegand and Gary Sullivan for inviting me to the
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285 Joint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.
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287 Thank to Thomas Richter and Daniel Lee for inviting me to the
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288 ISO/IEC JTC1/SC29/WG1 (also known as JPEG, together with ITU-T SG16)
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289 meeting in Berlin, Germany.
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291 Thank to John Korejwa and Massimo Ballerini for inviting me to
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292 fruitful consultations in Boston, MA and Milan, Italy.
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294 Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, Guenther
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295 Maier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagel
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296 for corresponding business development.
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298 Thank to Nico Zschach and Dirk Stelling of the technical support team
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299 at the Digital Images company in Halle for providing me with extra
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300 equipment for configuration tests.
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302 Thank to Richard F. Lyon (then of Foveon Inc.) for fruitful
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303 communication about JPEG configuration in Sigma Photo Pro software.
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305 Thank to Andrew Finkenstadt for hosting the ijg.org site.
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307 Last but not least special thank to Thomas G. Lane for the original
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308 design and development of this singular software package.
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314 The ISO/IEC JTC1/SC29/WG1 standards committee (also known as JPEG, together
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315 with ITU-T SG16) currently promotes different formats containing the name
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316 "JPEG" which is misleading because these formats are incompatible with
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317 original DCT-based JPEG and are based on faulty technologies.
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318 IJG therefore does not and will not support such momentary mistakes
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320 There exist also distributions under the name "OpenJPEG" promoting such
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321 kind of formats which is misleading because they don't support original
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323 We have no sympathy for the promotion of inferior formats. Indeed, one of
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324 the original reasons for developing this free software was to help force
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325 convergence on common, interoperable format standards for JPEG files.
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326 Don't use an incompatible file format!
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327 (In any case, our decoder will remain capable of reading existing JPEG
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328 image files indefinitely.)
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330 Furthermore, the ISO committee pretends to be "responsible for the popular
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331 JPEG" in their public reports which is not true because they don't respond to
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332 actual requirements for the maintenance of the original JPEG specification.
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334 There are currently distributions in circulation containing the name
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335 "libjpeg" which claim to be a "derivative" or "fork" of the original
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336 libjpeg, but don't have the features and are incompatible with formats
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337 supported by actual IJG libjpeg distributions. Furthermore, they
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338 violate the license conditions as described under LEGAL ISSUES above.
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339 We have no sympathy for the release of misleading and illegal
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340 distributions derived from obsolete code bases.
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341 Don't use an obsolete code base!
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347 Version 8 is the first release of a new generation JPEG standard
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348 to overcome the limitations of the original JPEG specification.
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349 More features are being prepared for coming releases...
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351 Please send bug reports, offers of help, etc. to jpeg-info@jpegclub.org.
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projects / irrlicht.git / blob