LICENSE
install.doc How to
IJG software.
usage.doc Usage instructions for cjpeg,
djpeg, jpegtran, rdjpgcom, and
wrjpgcom.
*.1 Unix man pages for
programs (same info as usage.
doc).
wizard.doc Advanced usage
JPEG wizards only
change.log V change
highlights.
P
libjpeg.doc How to the JPEG in
your own programs.
example.c Sample code for calling the
JPEG library
structure.doc Overview of the JPEG library
internal structure.
lelist.doc Road map of IJG les.
coderules.doc Coding style rules ---
if you contribute code.
Please read the les
Useful information can also be found in the JPEG F
(F Ask Questions) article. See ARCHIVE
L where obtain
article.
If you
suggest one REFERENCES
looking at les (in order
listed) before diving into the code.
OVERVIEW
This
compression
peg”) is a
and gray
“ scenes; line drawings, cartoons and other
non-realistic images are not its strong suit. JPEG is lossy
meaning
the input you not use if
have to have output bits. However on typical
photographic levels can
be
compression levels
quality
experiment with various compression settings.
This software implements JPEG baseline, extended-
sequential, and progressive
compression processes.
all variants of these
processes,
aren
F legal reasons, we are not distributing code for the
arithmetic-coding
variants of
provision for supporting
the hierarchical or lossless processes dened in the
standard.
W
JPEG image two “cjpeg”
and
between JPEG and some other popular image le
formats.
The library is intended to be reused in other applications.
In
we have considerable functionality the
bare JPEG coding/decoding for example,
color quantization are strictly part JPEG
decoding,
le
can be compiled out the library if not required a
particular
a lossless
processes, “ and simple
applications
in JFIF les.
The emphasis in designing this software has been on
achieving portability and exibility while also making it
fast enough to be In particular the software is
not to on the
REFERENCES for material.)
it is to be portable,
code.
aspect of the software, but we strive for it.
W
commercial products.
No royalty is required, but we do ask for an
acknowledgement
under LEGAL ISSUES.
LEGAL ISSUES
In plain English:
1. W
nd any bugs, please let us know!)
2. Y
don
3. Y may not pretend that you wrote this software.
If you use it in a program, you must acknowledge
somewhere in documentation that used
the IJG code.
In legalese:
The authors mak NO W or representation,
either
quality
purpose. is provided “
user
This software is copyright (C) 1991-1998, Thomas G.
Lane.
All Rights Reserved except as specied below
P is hereby 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,
with
and
les 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) P software
the user accepts full
consequences; the NO for
damages of any kind.
These conditions to software from
based
If you use our work, you ought to acknowledge us.
P
name or
to
may
software”.
W and encourage the use of this
software the commercial
that all warranty or liability claims are assumed by the
product vendor
ansi2knr
L. P proprietor copyright
Aladdin Enterprises of Menlo P
ansi2knr is NO covered by the above copyright and
conditions,
the must
include source code redistribute it.
ansi2knr full details.) However since ansi2knr is
not needed part of program the
IJG code,
paragraphs do.
The Unix “congure” was produced
with GNU Autoconf
It is copyright by the Free Software F but is
freely distributable.
The same holds for its supporting scripts (cong.
guess, cong ltcong ltmain.sh).
script, install-sh, is by M.I.T is also
distributable.
It arithmetic coding option of the JPEG
spec is covered by patents owned by IBM, A& T and
Mitsubishi. Hence arithmetic coding cannot legally be
used without obtaining one or more licenses. F this
reason,
from the free JPEG software.
(Since arithmetic coding provides only a marginal gain
over the
many implementations will support it.)
So far
the remaining code.
The IJG formerly code read
write GIF les.
T avoid the GIF
reading support has been removed altogether and the
GIF writer has
GIFs”.
resulting
all standard GIF decoders.
W
“The
property of CompuServe GIF(sm) is
Service Mark property of CompuServe Incorporated.”
REFERENCES
W recommend reading one or more of these
references
JPEG software.
The best short technical introduction to the JPEG
compression algorithm is
Wallace, Gregory K “The JPEG Still Picture
Compression
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 the CACM issue handy a
P le version of W
article is available at ftp://ftp.uu.net/graphics/jpeg/
wallace.ps.gz. le preprint article
that appeared in IEEE T
the sample
corrections and
article is copyright ACM and IEEE, and it may not be used
for commercial purposes.
A somewhat less technical, more leisurely introduction
to can “The Book”
by Nelson M&T
Books
book provides good explanations and example C code for
a of compression methods It
is an excellent if you are reading C
code but don know much about data compression
in general. The book JPEG sample code is far from
industrial-strength, but
implementation, you
The best description JPEG the textbook
Still Image Data Compression Standard” by William
B. Pennebak and Joan L Mitchell, published by V
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).
This is by the most exposition of in
existence, and we highly recommend it.
The JPEG standard itself is not available electronically;
you must order
you feel a need to own a certied ofcial copy
recommend buying the P
instead; it’s cheaper includes a deal
useful explanatory material.)
In
ANSI Sales
Documents (ANSI doesn’t
card orders,
ANSI was
7% is two
parts, being actual P
covers
Compression and
P
numbers ISO/IEC 10918-1, T 2 titled
“Digital Compression
Images, P Compliance testing” has document
numbers ISO/IEC IS 10918-2, ITU-
Some
in
IS 10918-3 and
any P
The JPEG standard does not specify all details of an
interchangeable le F details
follow the
JFIF spec is available from:
Literature Department
C-
1778 McCarthy Blvd.
Milpitas, CA 95035
phone (408) 944-6300, fax (408) 944-6314
