Top Document: comp.compression Frequently Asked Questions (part 1/3)
The JBIG algorithm is one of the best available for lossless image
compression. For an introduction to JBIG, see question 74 in part 2.
JBIG works best on bi-level images (like faxes) and also works well on
Gray-coded grey scale images up to about six or so bits per pixel. You
just apply JBIG to the bit planes individually. For more bits/pixel,
lossless JPEG provides better performance, sometimes. (For JPEG, see
question 19 below.)
You can find the specification of JBIG in International Standard
ISO/IEC 11544 or in ITU-T Recommendation T.82. You can order a copy
directly from ISO (www.iso.ch) or ITU (www.itu.ch) or from your
National Standards Body. In the USA, call ANSI at (212) 642-4900.
See also the MG system containing an implementation of the 'FELICS'
algorithm of P.G. Howard and J.S. Vitter. FELICS usually gives better
and faster compression than lossless JPEG, at least for 8-bit
grayscale images. (See item 15 above for ftp location). From the MG
README file:
The MG system is a suite of programs for compressing and
indexing text and images. Most of the functionality implemented
in the suite is as described in the book ``Managing Gigabytes:
Compressing and Indexing Documents and Images'', I.H. Witten, A.
Moffat, and T.C. Bell; Van Nostrand Reinhold, New York, 1994, ISBN
0-442-01863-0; US $54.95; call 1 (800) 544-0550 to order.
These features include:
-- text compression using a Huffman-coded semi-static word-based
scheme
-- two-level context-based compression of bi-level images
-- FELICS lossless compression of gray-scale images
-- combined lossy/lossless compression for textual images
-- indexing algorithms for large volumes of text in limited main
memory
-- index compression
-- a retrieval system that processes Boolean and ranked queries
-- an X windows interface to the retrieval system
Paul Howard's PhD thesis, which among other things describes FELICS,
is available in ftp://ftp.cs.brown.edu/pub/techreports/93/cs93-28.ps.Z
JPEG-LS is the emerging ISO standard for lossless/near-lossless
compression of continuous-tone images. Marcelo Weinberger
<marcelo@hplwein.hpl.hp.com> says about it:
JPEG-LS is being developed by ISO/IEC JTC1/SC29/WG1 (final committee
draft document FCD14495-1 as of July 1997), and it is based on HP's
LOCO-I algorithm (reference: M. Weinberger, G. Seroussi, G. Sapiro,
"LOCO-I: A Low Complexity, Context-Based, Lossless Image Compression
Algorithm," Proc. IEEE Data Compression Conference, Snowbird, Utah,
March-April 1996). [...]
The main feature of JPEG-LS is its superior placement in the
compression/complexity trade-off curve. Tested over a wide variety of
image types, it was shown to be, on the average, within about 4% of the
best available lossless image compression at a fraction of the
complexity. In particular, JPEG-LS significantly outperforms FELICS
and lossless JPEG Huffman at similar levels of complexity (it also
outperforms lossless JPEG arithmetic, which is of significantly higher
complexity). [...]
A software implementation of JPEG-LS, is now available at:
http://www.hpl.hp.com/loco/
There, the DCC'96 paper on LOCO-I is also available. The standard draft
is also available through a link to the official JPEG Web site.
Benchmarks of some lossless image compression programs are in
http://www.geocities.com/SiliconValley/Bay/1995/artest11.html
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