Cross Reference: /external/libjpeg-turbo/

libjpeg-turbo note:  This file has been modified by The libjpeg-turbo Project
to include only information relevant to libjpeg-turbo, to wordsmith certain
sections, and to remove impolitic language that existed in the libjpeg v8
README.  It is included only for reference.  Please see README-turbo.txt for
information specific to libjpeg-turbo.


The Independent JPEG Group's JPEG software
==========================================

This distribution contains a release of the Independent JPEG Group's free JPEG
software.  You are welcome to redistribute this software and to 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
(also 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.
FILE FORMAT WARS    Software *not* to get.
TO DO               Plans for future IJG releases.

Other documentation files in the distribution are:

User documentation:
  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.
  coderules.txt     Coding style rules --- please read if you contribute code.

Please read at least usage.txt.  Some information can also be found in the JPEG
FAQ (Frequently Asked Questions) article.  See ARCHIVE 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 or
more of the REFERENCES, then looking at the documentation files (in roughly
the 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 compression
method for full-color and grayscale images.  JPEG's strong suit is compressing
photographic images or other types of images that have smooth color and
brightness transitions between neighboring pixels.  Images with sharp lines or
other abrupt features may not compress well with JPEG, and a higher JPEG
quality may have to be used to avoid visible compression artifacts with such
images.

JPEG is lossy, meaning that the output pixels are not necessarily identical to
the input pixels.  However, on photographic content and other "smooth" images,
very good compression ratios can be obtained with no visible compression
artifacts, and extremely high compression ratios are possible if you are
willing to sacrifice image quality (by reducing the "quality" setting in the
compressor.)

This software implements JPEG baseline, extended-sequential, and progressive
compression processes.  Provision is made for supporting all variants of these
processes, although some uncommon parameter settings aren't implemented yet.
We have made no provision for supporting the hierarchical or lossless
processes 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 to
perform 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 included
considerable functionality beyond the bare JPEG coding/decoding capability;
for example, the color quantization modules are not strictly part of JPEG
decoding, but they are essential for output to colormapped file formats or
colormapped displays.  These extra functions can be compiled out of the
library if not required for a particular application.

We have also included "jpegtran", a utility for lossless transcoding between
different JPEG processes, and "rdjpgcom" and "wrjpgcom", two simple
applications for inserting and extracting textual comments in JFIF files.

The emphasis in designing this software has been on achieving portability and
flexibility, 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 the
REFERENCES section for introductory material.)  Rather, it is intended to
be reliable, portable, industrial-strength code.  We do not claim to have
achieved 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 product
documentation, 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, or
fitness 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) 1991-2012, Thomas G. Lane, Guido Vollbeding.
All Rights Reserved except as specified below.

Permission is hereby granted to use, copy, modify, and distribute this
software (or portions thereof) for any purpose, without fee, subject to these
conditions:
(1) If any part of the source code for this software is distributed, then this
README file must be included, with this copyright and no-warranty notice
unaltered; and any additions, deletions, or changes to the original files
must be clearly indicated in accompanying documentation.
(2) If only executable code is distributed, then the accompanying
documentation must state that "this software is based in part on the work of
the Independent JPEG Group".
(3) Permission for use of this software is granted only if the user accepts
full responsibility for any undesirable consequences; the authors accept
NO 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 to
acknowledge us.

Permission is NOT granted for the use of any IJG author's name or company name
in advertising or publicity relating to this software or products derived from
it.  This software may be referred to only as "the Independent JPEG Group's
software".

We specifically permit and encourage the use of this software as the basis of
commercial products, provided that all warranty or liability claims are
assumed 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 Consortium
but is also freely distributable.

The IJG distribution formerly included code to read and write GIF files.
To avoid entanglement with the Unisys LZW patent, GIF reading support has
been removed altogether, and the GIF writer has been simplified to produce
"uncompressed GIFs".  This technique does not use the LZW algorithm; the
resulting GIF files are larger than usual, but are readable by all standard
GIF decoders.

We are required to state that
    "The Graphics Interchange Format(c) is the Copyright property of
    CompuServe Incorporated.  GIF(sm) is a Service Mark property of
    CompuServe Incorporated."


REFERENCES
==========

We recommend reading one or more of these references before trying to
understand the innards of the JPEG software.

The best short technical introduction to the JPEG compression algorithm is
	Wallace, 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 issue
handy, a PostScript file containing a revised version of Wallace's article is
available at http://www.ijg.org/files/wallace.ps.gz.  The file (actually
a preprint for an article that appeared in IEEE Trans. Consumer Electronics)
omits the sample images that appeared in CACM, but it includes corrections
and 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 by
M&T Books (New York), 2nd ed. 1996, ISBN 1-55851-434-1.  This book provides
good explanations and example C code for a multitude of compression methods
including JPEG.  It is an excellent source if you are comfortable reading C
code but don't know much about data compression in general.  The book's JPEG
sample code is far from industrial-strength, but when you are ready to look
at a full implementation, you've got one here...

The best currently available description of JPEG is the textbook "JPEG Still
Image 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 JPEG
standards (DIS 10918-1 and draft DIS 10918-2).

The original JPEG standard is divided into two parts, Part 1 being the actual
specification, while Part 2 covers compliance testing methods.  Part 1 is
titled "Digital Compression and Coding of Continuous-tone Still Images,
Part 1: Requirements and guidelines" and has document numbers ISO/IEC IS
10918-1, ITU-T T.81.  Part 2 is titled "Digital Compression and Coding of
Continuous-tone Still Images, Part 2: Compliance testing" and has document
numbers ISO/IEC IS 10918-2, ITU-T T.83.

The JPEG standard does not specify all details of an interchangeable file
format.  For the omitted details we follow the "JFIF" conventions, revision
1.02.  JFIF 1.02 has been adopted as an Ecma International Technical Report
and thus received a formal publication status.  It is available as a free
download in PDF format from
http://www.ecma-international.org/publications/techreports/E-TR-098.htm.
A PostScript version of the JFIF document is available at
http://www.ijg.org/files/jfif.ps.gz.  There is also a plain text version at
http://www.ijg.org/files/jfif.txt.gz, but it is missing the figures.

The TIFF 6.0 file format specification can be obtained by FTP from
ftp://ftp.sgi.com/graphics/tiff/TIFF6.ps.gz.  The JPEG incorporation scheme
found 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 from
http://www.ijg.org/files/.  It is expected that the next revision
of 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 library
uses our library to implement TIFF/JPEG per the Note.


ARCHIVE LOCATIONS
=================

The "official" archive site for this software is www.ijg.org.
The most recent released version can always be found there in
directory "files".  This particular version will be archived as
http://www.ijg.org/files/jpegsrc.v8d.tar.gz, and in Windows-compatible
"zip" archive format as http://www.ijg.org/files/jpegsr8d.zip.

The JPEG FAQ (Frequently Asked Questions) article is a source of some
general information about JPEG.
It is available on the World Wide Web at http://www.faqs.org/faqs/jpeg-faq/
and other news.answers archive sites, including the official news.answers
archive 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.edu
with body
	send usenet/news.answers/jpeg-faq/part1
	send usenet/news.answers/jpeg-faq/part2


FILE FORMAT WARS
================

The ISO/IEC JTC1/SC29/WG1 standards committee (also known as JPEG, together
with ITU-T SG16) currently promotes different formats containing the name
"JPEG" which are incompatible with original DCT-based JPEG.  IJG therefore does
not support these formats (see REFERENCES).  Indeed, one of the original
reasons for developing this free software was to help force convergence 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 JPEG
image files indefinitely.)


TO DO
=====

Please send bug reports, offers of help, etc. to jpeg-info@jpegclub.org.
Name	Date	Size
..	10-Aug-2018	12 KiB
.gitignore	10-Aug-2018	146
acinclude.m4	10-Aug-2018	6.7 KiB
Android.bp	10-Aug-2018	5.9 KiB
appveyor.yml	10-Aug-2018	1.8 KiB
bmp.c	10-Aug-2018	9.7 KiB
bmp.h	10-Aug-2018	1.8 KiB
BUILDING.md	10-Aug-2018	34.3 KiB
cderror.h	10-Aug-2018	5.3 KiB
cdjpeg.c	10-Aug-2018	3.9 KiB
cdjpeg.h	10-Aug-2018	5.5 KiB
change.log	10-Aug-2018	12.1 KiB
ChangeLog.md	10-Aug-2018	55.1 KiB
ci/	10-Aug-2018	4 KiB
cjpeg.1	10-Aug-2018	13.2 KiB
cjpeg.c	10-Aug-2018	21.3 KiB
CMakeLists.txt	10-Aug-2018	37.2 KiB
cmakescripts/	10-Aug-2018	4 KiB
coderules.txt	10-Aug-2018	3.4 KiB
configure.ac	10-Aug-2018	19.4 KiB
djpeg.1	10-Aug-2018	9.6 KiB
djpeg.c	10-Aug-2018	25.8 KiB
doc/	10-Aug-2018	4 KiB
doxygen-extra.css	10-Aug-2018	26
doxygen.config	10-Aug-2018	401
example.c	10-Aug-2018	16.8 KiB
jaricom.c	10-Aug-2018	5 KiB
java/	10-Aug-2018	4 KiB
jcapimin.c	10-Aug-2018	9.5 KiB
jcapistd.c	10-Aug-2018	5.8 KiB
jcarith.c	10-Aug-2018	28.9 KiB
jccoefct.c	10-Aug-2018	16.8 KiB
jccolext.c	10-Aug-2018	4.5 KiB
jccolor.c	10-Aug-2018	23.4 KiB
jcdctmgr.c	10-Aug-2018	22 KiB
jchuff.c	10-Aug-2018	33.6 KiB
jchuff.h	10-Aug-2018	1.4 KiB
jcinit.c	10-Aug-2018	2.4 KiB
jcmainct.c	10-Aug-2018	5 KiB
jcmarker.c	10-Aug-2018	17.2 KiB
jcmaster.c	10-Aug-2018	21.4 KiB
jcomapi.c	10-Aug-2018	3.2 KiB
jconfig.h	10-Aug-2018	2.2 KiB
jconfig.h.in	10-Aug-2018	2.1 KiB
jconfig.txt	10-Aug-2018	4.8 KiB
jconfigint.h	10-Aug-2018	1 KiB
jconfigint.h.in	10-Aug-2018	336
jcparam.c	10-Aug-2018	17.7 KiB
jcphuff.c	10-Aug-2018	25.3 KiB
jcprepct.c	10-Aug-2018	12.9 KiB
jcsample.c	10-Aug-2018	19.8 KiB
jcstest.c	10-Aug-2018	3.8 KiB
jctrans.c	10-Aug-2018	14.6 KiB
jdapimin.c	10-Aug-2018	12.9 KiB
jdapistd.c	10-Aug-2018	23.2 KiB
jdarith.c	10-Aug-2018	24.4 KiB
jdatadst-tj.c	10-Aug-2018	6.6 KiB
jdatadst.c	10-Aug-2018	9.5 KiB
jdatasrc-tj.c	10-Aug-2018	6.7 KiB
jdatasrc.c	10-Aug-2018	10.1 KiB
jdcoefct.c	10-Aug-2018	24.7 KiB
jdcoefct.h	10-Aug-2018	2.6 KiB
jdcol565.c	10-Aug-2018	12 KiB
jdcolext.c	10-Aug-2018	4.4 KiB
jdcolor.c	10-Aug-2018	28.5 KiB
jdct.h	10-Aug-2018	8.8 KiB
jddctmgr.c	10-Aug-2018	11.2 KiB
jdhuff.c	10-Aug-2018	25.4 KiB
jdhuff.h	10-Aug-2018	9.2 KiB
jdinput.c	10-Aug-2018	14.2 KiB
jdmainct.c	10-Aug-2018	18.9 KiB
jdmainct.h	10-Aug-2018	2.4 KiB
jdmarker.c	10-Aug-2018	41.9 KiB
jdmaster.c	10-Aug-2018	27.3 KiB
jdmaster.h	10-Aug-2018	788
jdmerge.c	10-Aug-2018	20.9 KiB
jdmrg565.c	10-Aug-2018	11.2 KiB
jdmrgext.c	10-Aug-2018	5.9 KiB
jdphuff.c	10-Aug-2018	21.4 KiB
jdpostct.c	10-Aug-2018	10.1 KiB
jdsample.c	10-Aug-2018	17.7 KiB
jdsample.h	10-Aug-2018	1.7 KiB
jdtrans.c	10-Aug-2018	5.3 KiB
jerror.c	10-Aug-2018	7.7 KiB
jerror.h	10-Aug-2018	14.7 KiB
jfdctflt.c	10-Aug-2018	5.4 KiB
jfdctfst.c	10-Aug-2018	7.6 KiB
jfdctint.c	10-Aug-2018	11.2 KiB
jidctflt.c	10-Aug-2018	8.5 KiB
jidctfst.c	10-Aug-2018	13.4 KiB
jidctint.c	10-Aug-2018	102.7 KiB
jidctred.c	10-Aug-2018	13.9 KiB
jinclude.h	10-Aug-2018	2.9 KiB
jmemmgr.c	10-Aug-2018	43.8 KiB
jmemnobs.c	10-Aug-2018	2.8 KiB
jmemsys.h	10-Aug-2018	7.6 KiB
jmorecfg.h	10-Aug-2018	14.7 KiB
jpeg_nbits_table.h	10-Aug-2018	264.1 KiB
jpegcomp.h	10-Aug-2018	1 KiB
jpegint.h	10-Aug-2018	15.2 KiB
jpeglib.h	10-Aug-2018	48.7 KiB
jpegtran.1	10-Aug-2018	9.4 KiB
jpegtran.c	10-Aug-2018	18.3 KiB
jquant1.c	10-Aug-2018	31.7 KiB
jquant2.c	10-Aug-2018	47.7 KiB
jsimd.h	10-Aug-2018	3.6 KiB
jsimd_none.c	10-Aug-2018	7.4 KiB
jsimddct.h	10-Aug-2018	3.2 KiB
jstdhuff.c	10-Aug-2018	5.2 KiB
jutils.c	10-Aug-2018	3.7 KiB
jversion.h	10-Aug-2018	1.8 KiB
libjpeg.map.in	10-Aug-2018	164
libjpeg.txt	10-Aug-2018	163.9 KiB
LICENSE.md	10-Aug-2018	5.2 KiB
Makefile.am	10-Aug-2018	33.5 KiB
md5/	10-Aug-2018	4 KiB
MODULE_LICENSE_BSD	10-Aug-2018	0
NOTICE	10-Aug-2018	2.9 KiB
OWNERS	10-Aug-2018	19
rdbmp.c	10-Aug-2018	15.1 KiB
rdcolmap.c	10-Aug-2018	6.9 KiB
rdgif.c	10-Aug-2018	1.3 KiB
rdjpgcom.1	10-Aug-2018	1.7 KiB
rdjpgcom.c	10-Aug-2018	14.7 KiB
rdppm.c	10-Aug-2018	14.3 KiB
rdrle.c	10-Aug-2018	11.5 KiB
rdswitch.c	10-Aug-2018	12.7 KiB
rdtarga.c	10-Aug-2018	15 KiB
README	10-Aug-2018	13.5 KiB
README-turbo.txt	10-Aug-2018	16.4 KiB
README.android	10-Aug-2018	1.2 KiB
README.ijg	10-Aug-2018	13.3 KiB
README.md	10-Aug-2018	15.8 KiB
README.version	10-Aug-2018	151
release/	10-Aug-2018	4 KiB
sharedlib/	10-Aug-2018	4 KiB
simd/	10-Aug-2018	4 KiB
structure.txt	10-Aug-2018	48.6 KiB
testimages/	10-Aug-2018	4 KiB
tjbench.c	10-Aug-2018	31.1 KiB
tjbenchtest.in	10-Aug-2018	11.4 KiB
tjbenchtest.java.in	10-Aug-2018	9.6 KiB
tjexampletest.in	10-Aug-2018	8 KiB
tjunittest.c	10-Aug-2018	18.6 KiB
tjutil.c	10-Aug-2018	2.1 KiB
tjutil.h	10-Aug-2018	1.9 KiB
transupp.c	10-Aug-2018	61 KiB
transupp.h	10-Aug-2018	9.4 KiB
turbojpeg-jni.c	10-Aug-2018	41.6 KiB
turbojpeg-mapfile	10-Aug-2018	794
turbojpeg-mapfile.jni	10-Aug-2018	2.9 KiB
turbojpeg.c	10-Aug-2018	61.9 KiB
turbojpeg.h	10-Aug-2018	63.6 KiB
usage.txt	10-Aug-2018	34.2 KiB
win/	10-Aug-2018	4 KiB
wizard.txt	10-Aug-2018	10.1 KiB
wrbmp.c	10-Aug-2018	15.3 KiB
wrgif.c	10-Aug-2018	13.2 KiB
wrjpgcom.1	10-Aug-2018	2.6 KiB
wrjpgcom.c	10-Aug-2018	17.5 KiB
wrppm.c	10-Aug-2018	8.3 KiB
wrppm.h	10-Aug-2018	721
wrrle.c	10-Aug-2018	9.2 KiB
wrtarga.c	10-Aug-2018	7.5 KiB