Free JPEG software released
harper at nic.funet.fi
Wed Dec 11 05:58:36 EST 1991
The Independent JPEG Group is proud to announce the first public release
of our free JPEG image compression software.
The C source code, documentation, and some minimal test files are available
for anonymous FTP from UUNET.UU.NET, file /graphics/jpeg/jpegsrc.v1.tar.Z.
The software has been tested on numerous Unix machines, PCs, Macs, and
Amigas; we believe it can be ported to almost any machine that has a
(reasonable) C compiler. We have successfully tested file compatibility
with several commercial JPEG implementations.
We consider this to be a preliminary release. The current software only
handles conversion between JPEG and PBMPLUS image formats, so it must be
used in conjunction with Jef Poskanzer's free PBMPLUS software. (Well,
actually it can read and write GIF files too, but writing GIF files doesn't
work very well yet.) Some operations will run out of memory on PCs and
other non-virtual-memory machines. Numerous improvements in functionality
and speed remain on our to-do list. Still, we think that the software is
useful now, and we would like to start getting feedback from users.
We are releasing this software for both noncommercial and commercial use.
Companies are welcome to use it as the basis for JPEG-related products.
We do not ask a royalty, although we do ask for an acknowledgement in
product literature (see the README file in the distribution for details).
We hope to make this software industrial-quality --- although, as with
anything that's free, we offer no warranty and accept no liability.
Please direct any questions about this software to jpeg-info at uunet.uu.net.
Excerpts from the README file follow.
JPEG is a standardized compression method for full-color and gray-scale
images. JPEG is intended for "real-world" scenes; cartoons and other
non-realistic images are not its strong suit. JPEG is lossy, meaning that
the output image is not necessarily identical to the input image. Hence you
should not use JPEG if you have to have identical output bits. However, on
typical images of real-world scenes, very good compression levels can be
obtained with hardly any visible change, and amazingly high compression
levels can be obtained if you can tolerate a low-quality image.
This software implements JPEG baseline and extended-sequential compression
processes. Provision is made for supporting all variants of these
processes, although some uncommon parameter settings aren't implemented yet.
For legal reasons, we are not distributing code for the arithmetic-coding
process. At present we have made no provision for supporting the
progressive or lossless processes defined in the standard.
The emphasis in designing this software has been on achieving portability and
flexibility, while also making it fast enough to be useful. We have not yet
undertaken serious performance measurement or tuning; we intend to do so in
This software can be used on several levels:
* As canned software for JPEG compression and decompression. Just edit the
Makefile and configuration files as needed, compile and go.
Members of the independent JPEG group will improve the out-of-the-box
functionality as time goes on.
* As the basis for other JPEG programs. For example, you could incorporate
the decompressor into a general image viewing package by replacing the
output module with write-to-screen functions. For an implementation on
specific hardware, you might want to replace some of the inner loops with
assembly code. For a non-command-line-driven system, you might want a
different user interface. (Members of the group will be producing Macintosh
and Amiga versions with appropriate user interfaces, for example.)
* As a toolkit for experimentation with JPEG and JPEG-like algorithms. Most
of the individual decisions you might want to mess with are packaged up into
separate modules. For example, the details of color-space conversion and
subsampling techniques are each localized in one compressor and one
decompressor module. You'd probably also want to extend the user interface
to give you more detailed control over the JPEG compression parameters.
Dr. Thomas G. Lane
organizer, Independent JPEG Group
Internet: tgl at cs.cmu.edu BITNET: tgl%cs.cmu.edu at cmuccvma
Rob Harper / E-mail: harper at convex.csc.fi
Finnish State Computer Centre / Molbio/software: harper at nic.funet.fi
P.O. Box 40, SF-02101 Espoo / Telephone: +358 0 457 2076
Finland / Fax: +358 0 457 2302
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