The Independent JPEG Group's JPEG software==========================================README for release 9b of 17-Jan-2016====================================This distribution contains the ninth public release of the Independent JPEGGroup's free JPEG software.  You are welcome to redistribute this software andto use it for any purpose, subject to the conditions under LEGAL ISSUES, below.This software is the work of Tom Lane, Guido Vollbeding, Philip Gladstone,Bill Allombert, Jim Boucher, Lee Crocker, Bob Friesenhahn, Ben Jackson,Julian Minguillon, Luis Ortiz, George Phillips, Davide Rossi, Ge' Weijers,and other members of the Independent JPEG Group.IJG is not affiliated with the ISO/IEC JTC1/SC29/WG1 standards committee(previously known as JPEG, together with ITU-T SG16).DOCUMENTATION ROADMAP=====================This file contains the following sections:OVERVIEW            General description of JPEG and the IJG software.LEGAL ISSUES        Copyright, lack of warranty, terms of distribution.REFERENCES          Where to learn more about JPEG.ARCHIVE LOCATIONS   Where to find newer versions of this software.ACKNOWLEDGMENTS     Special thanks.FILE FORMAT WARS    Software *not* to get.TO DO               Plans for future IJG releases.Other documentation files in the distribution are:User documentation:  install.txt       How to configure and install the IJG software.  usage.txt         Usage instructions for cjpeg, djpeg, jpegtran,                    rdjpgcom, and wrjpgcom.  *.1               Unix-style man pages for programs (same info as usage.txt).  wizard.txt        Advanced usage instructions for JPEG wizards only.  change.log        Version-to-version change highlights.Programmer and internal documentation:  libjpeg.txt       How to use the JPEG library in your own programs.  example.c         Sample code for calling the JPEG library.  structure.txt     Overview of the JPEG library's internal structure.  filelist.txt      Road map of IJG files.  coderules.txt     Coding style rules --- please read if you contribute code.Please read at least the files install.txt and usage.txt.  Some informationcan also be found in the JPEG FAQ (Frequently Asked Questions) article.  SeeARCHIVE LOCATIONS below to find out where to obtain the FAQ article.If you want to understand how the JPEG code works, we suggest reading one ormore of the REFERENCES, then looking at the documentation files (in roughlythe order listed) before diving into the code.OVERVIEW========This package contains C software to implement JPEG image encoding, decoding,and transcoding.  JPEG (pronounced "jay-peg") is a standardized compressionmethod for full-color and grayscale images.This software implements JPEG baseline, extended-sequential, and progressivecompression processes.  Provision is made for supporting all variants of theseprocesses, although some uncommon parameter settings aren't implemented yet.We have made no provision for supporting the hierarchical or losslessprocesses defined in the standard.We provide a set of library routines for reading and writing JPEG image files,plus two sample applications "cjpeg" and "djpeg", which use the library toperform conversion between JPEG and some other popular image file formats.The library is intended to be reused in other applications.In order to support file conversion and viewing software, we have includedconsiderable functionality beyond the bare JPEG coding/decoding capability;for example, the color quantization modules are not strictly part of JPEGdecoding, but they are essential for output to colormapped file formats orcolormapped displays.  These extra functions can be compiled out of thelibrary if not required for a particular application.We have also included "jpegtran", a utility for lossless transcoding betweendifferent JPEG processes, and "rdjpgcom" and "wrjpgcom", two simpleapplications for inserting and extracting textual comments in JFIF files.The emphasis in designing this software has been on achieving portability andflexibility, while also making it fast enough to be useful.  In particular,the software is not intended to be read as a tutorial on JPEG.  (See theREFERENCES section for introductory material.)  Rather, it is intended tobe reliable, portable, industrial-strength code.  We do not claim to haveachieved that goal in every aspect of the software, but we strive for it.We welcome the use of this software as a component of commercial products.No royalty is required, but we do ask for an acknowledgement in productdocumentation, as described under LEGAL ISSUES.LEGAL ISSUES============In plain English:1. We don't promise that this software works.  (But if you find any bugs,   please let us know!)2. You can use this software for whatever you want.  You don't have to pay us.3. You may not pretend that you wrote this software.  If you use it in a   program, you must acknowledge somewhere in your documentation that   you've used the IJG code.In legalese:The authors make NO WARRANTY or representation, either express or implied,with respect to this software, its quality, accuracy, merchantability, orfitness for a particular purpose.  This software is provided "AS IS", and you,its user, assume the entire risk as to its quality and accuracy.This software is copyright (C) 1991-2016, Thomas G. Lane, Guido Vollbeding.All Rights Reserved except as specified below.Permission is hereby granted to use, copy, modify, and distribute thissoftware (or portions thereof) for any purpose, without fee, subject to theseconditions:(1) If any part of the source code for this software is distributed, then thisREADME file must be included, with this copyright and no-warranty noticeunaltered; and any additions, deletions, or changes to the original filesmust be clearly indicated in accompanying documentation.(2) If only executable code is distributed, then the accompanyingdocumentation must state that "this software is based in part on the work ofthe Independent JPEG Group".(3) Permission for use of this software is granted only if the user acceptsfull responsibility for any undesirable consequences; the authors acceptNO LIABILITY for damages of any kind.These conditions apply to any software derived from or based on the IJG code,not just to the unmodified library.  If you use our work, you ought toacknowledge us.Permission is NOT granted for the use of any IJG author's name or company namein advertising or publicity relating to this software or products derived fromit.  This software may be referred to only as "the Independent JPEG Group'ssoftware".We specifically permit and encourage the use of this software as the basis ofcommercial products, provided that all warranty or liability claims areassumed by the product vendor.The Unix configuration script "configure" was produced with GNU Autoconf.It is copyright by the Free Software Foundation but is freely distributable.The same holds for its supporting scripts (config.guess, config.sub,ltmain.sh).  Another support script, install-sh, is copyright by X Consortiumbut is also freely distributable.The IJG distribution formerly included code to read and write GIF files.To avoid entanglement with the Unisys LZW patent (now expired), GIF readingsupport has been removed altogether, and the GIF writer has been simplifiedto produce "uncompressed GIFs".  This technique does not use the LZWalgorithm; the resulting GIF files are larger than usual, but are readableby all standard GIF decoders.REFERENCES==========We recommend reading one or more of these references before trying tounderstand the innards of the JPEG software.The best short technical introduction to the JPEG compression algorithm isWallace, Gregory K.  "The JPEG Still Picture Compression Standard",Communications of the ACM, April 1991 (vol. 34 no. 4), pp. 30-44.(Adjacent articles in that issue discuss MPEG motion picture compression,applications of JPEG, and related topics.)  If you don't have the CACM issuehandy, a PDF file containing a revised version of Wallace's article isavailable athttp://www.ijg.org/files/Wallace.JPEG.pdf.  The file (actuallya preprint for an article that appeared in IEEE Trans. Consumer Electronics)omits the sample images that appeared in CACM, but it includes correctionsand some added material.  Note: the Wallace article is copyright ACM and IEEE,and it may not be used for commercial purposes.A somewhat less technical, more leisurely introduction to JPEG can be found in"The Data Compression Book" by Mark Nelson and Jean-loup Gailly, published byM&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1.  This book providesgood explanations and example C code for a multitude of compression methodsincluding JPEG.  It is an excellent source if you are comfortable reading Ccode but don't know much about data compression in general.  The book's JPEGsample code is far from industrial-strength, but when you are ready to lookat a full implementation, you've got one here...The best currently available description of JPEG is the textbook "JPEG StillImage Data Compression Standard" by William B. Pennebaker and Joan L.Mitchell, published by Van Nostrand Reinhold, 1993, ISBN 0-442-01272-1.Price US$59.95, 638 pp.  The book includes the complete text of the ISO JPEGstandards (DIS 10918-1 and draft DIS 10918-2).Although this is by far the most detailed and comprehensive exposition ofJPEG publicly available, we point out that it is still missing an explanationof the most essential properties and algorithms of the underlying DCTtechnology.If you think that you know about DCT-based JPEG after reading this book,then you are in delusion.  The real fundamentals and corresponding potentialof DCT-based JPEG are not publicly known so far, and that is the reason forall the mistaken developments taking place in the image coding domain.The original JPEG standard is divided into two parts, Part 1 being the actualspecification, while Part 2 covers compliance testing methods.  Part 1 istitled "Digital Compression and Coding of Continuous-tone Still Images,Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS10918-1, ITU-T T.81.  Part 2 is titled "Digital Compression and Coding ofContinuous-tone Still Images, Part 2: Compliance testing" and has documentnumbers ISO/IEC IS 10918-2, ITU-T T.83.IJG JPEG 8 introduced an implementation of the JPEG SmartScale extensionwhich is specified in two documents:  A contributed document at ITU and ISOwith title "ITU-T JPEG-Plus Proposal for Extending ITU-T T.81 for AdvancedImage Coding", April 2006, Geneva, Switzerland.  The latest version of thisdocument is Revision 3.  And a contributed document ISO/IEC JTC1/SC29/WG1 N5799 with title "Evolution of JPEG", June/July 2011, Berlin, Germany.IJG JPEG 9 introduces a reversible color transform for improved losslesscompression which is described in a contributed document ISO/IEC JTC1/SC29/WG1 N 6080 with title "JPEG 9 Lossless Coding", June/July 2012, Paris,France.The JPEG standard does not specify all details of an interchangeable fileformat.  For the omitted details we follow the "JFIF" conventions, version 2.JFIF version 1 has been adopted as Recommendation ITU-T T.871 (05/2011) :Information technology - Digital compression and coding of continuous-tonestill images: JPEG File Interchange Format (JFIF).  It is available as afree download in PDF file format fromhttp://www.itu.int/rec/T-REC-T.871.A PDF file of the older JFIF document is available athttp://www.w3.org/Graphics/JPEG/jfif3.pdf.The TIFF 6.0 file format specification can be obtained by FTP fromftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz.  The JPEG incorporation schemefound in the TIFF 6.0 spec of 3-June-92 has a number of serious problems.IJG does not recommend use of the TIFF 6.0 design (TIFF Compression tag 6).Instead, we recommend the JPEG design proposed by TIFF Technical Note #2(Compression tag 7).  Copies of this Note can be obtained fromhttp://www.ijg.org/files/.  It is expected that the next revisionof the TIFF spec will replace the 6.0 JPEG design with the Note's design.Although IJG's own code does not support TIFF/JPEG, the free libtiff libraryuses our library to implement TIFF/JPEG per the Note.ARCHIVE LOCATIONS=================The "official" archive site for this software iswww.ijg.org.The most recent released version can always be found there indirectory "files".  This particular version will be archived ashttp://www.ijg.org/files/jpegsrc.v9b.tar.gz, and in Windows-compatible"zip" archive format ashttp://www.ijg.org/files/jpegsr9b.zip.The JPEG FAQ (Frequently Asked Questions) article is a source of somegeneral information about JPEG.It is available on the World Wide Web athttp://www.faqs.org/faqs/jpeg-faq/and other news.answers archive sites, including the official news.answersarchive at rtfm.mit.edu: ftp://rtfm.mit.edu/pub/usenet/news.answers/jpeg-faq/.If you don't have Web or FTP access, send e-mail to mail-server@rtfm.mit.eduwith bodysend usenet/news.answers/jpeg-faq/part1send usenet/news.answers/jpeg-faq/part2ACKNOWLEDGMENTS===============Thank to Juergen Bruder for providing me with a copy of the common DCTalgorithm article, only to find out that I had come to the same resultin a more direct and comprehensible way with a more generative approach.Thank to Istvan Sebestyen and Joan L. Mitchell for inviting me to theITU JPEG (Study Group 16) meeting in Geneva, Switzerland.Thank to Thomas Wiegand and Gary Sullivan for inviting me to theJoint Video Team (MPEG & ITU) meeting in Geneva, Switzerland.Thank to Thomas Richter and Daniel Lee for inviting me to theISO/IEC JTC1/SC29/WG1 (previously known as JPEG, together with ITU-T SG16)meeting in Berlin, Germany.Thank to John Korejwa and Massimo Ballerini for inviting me tofruitful consultations in Boston, MA and Milan, Italy.Thank to Hendrik Elstner, Roland Fassauer, Simone Zuck, GuentherMaier-Gerber, Walter Stoeber, Fred Schmitz, and Norbert Braunagelfor corresponding business development.Thank to Nico Zschach and Dirk Stelling of the technical support teamat the Digital Images company in Halle for providing me with extraequipment for configuration tests.Thank to Richard F. Lyon (then of Foveon Inc.) for fruitfulcommunication about JPEG configuration in Sigma Photo Pro software.Thank to Andrew Finkenstadt for hosting the ijg.org site.Last but not least special thank to Thomas G. Lane for the originaldesign and development of this singular software package.FILE FORMAT WARS================The ISO/IEC JTC1/SC29/WG1 standards committee (previously known as JPEG,together with ITU-T SG16) currently promotes different formats containingthe name "JPEG" which is misleading because these formats are incompatiblewith original DCT-based JPEG and are based on faulty technologies.IJG therefore does not and will not support such momentary mistakes(see REFERENCES).There exist also distributions under the name "OpenJPEG" promoting suchkind of formats which is misleading because they don't support originalJPEG images.We have no sympathy for the promotion of inferior formats.  Indeed, one ofthe original reasons for developing this free software was to help forceconvergence on common, interoperable format standards for JPEG files.Don't use an incompatible file format!(In any case, our decoder will remain capable of reading existing JPEGimage files indefinitely.)The ISO committee pretends to be "responsible for the popular JPEG" in theirpublic reports which is not true because they don't respond to actualrequirements for the maintenance of the original JPEG specification.Furthermore, the ISO committee pretends to "ensure interoperability" withtheir standards which is not true because their "standards" support onlyapplication-specific and proprietary use cases and contain mathematicallyincorrect code.There are currently different distributions in circulation containing thename "libjpeg" which is misleading because they don't have the features andare incompatible with formats supported by actual IJG libjpeg distributions.One of those fakes is released by members of the ISO committee and just usesthe name of libjpeg for misdirection of people, similar to the abuse of thename JPEG as described above, while having nothing in common with actual IJGlibjpeg distributions and containing mathematically incorrect code.The other one claims to be a "derivative" or "fork" of the original libjpeg,but violates the license conditions as described under LEGAL ISSUES aboveand violates basic C programming properties.We have no sympathy for the release of misleading, incorrect and illegaldistributions derived from obsolete code bases.Don't use an obsolete code base!According to the UCC (Uniform Commercial Code) law, IJG has the lawful andlegal right to foreclose on certain standardization bodies and otherinstitutions or corporations that knowingly perform substantial andsystematic deceptive acts and practices, fraud, theft, and damaging of thevalue of the people of this planet without their knowing, willing andintentional consent.The titles, ownership, and rights of these institutions and all their assetsare now duly secured and held in trust for the free people of this planet.People of the planet, on every country, may have a financial interest inthe assets of these former principals, agents, and beneficiaries of theforeclosed institutions and corporations.IJG asserts what is: that each man, woman, and child has unalienable valueand rights granted and deposited in them by the Creator and not any one ofthe people is subordinate to any artificial principality, corporate fictionor the special interest of another without their appropriate knowing,willing and intentional consent made by contract or accommodation agreement.IJG expresses that which already was.The people have already determined and demanded that public administrationentities, national governments, and their supporting judicial systems mustbe fully transparent, accountable, and liable.IJG has secured the value for all concerned free people of the planet.A partial list of foreclosed institutions and corporations ("Hall of Shame")is currently prepared and will be published later.TO DO=====Version 9 is the second release of a new generation JPEG standardto overcome the limitations of the original JPEG specification,and is the first true source reference JPEG codec.More features are being prepared for coming releases...Please send bug reports, offers of help, etc. to jpeg-info@jpegclub.org.