> I have the following questions: What is the best lossless compression
> algorithm for images (continuos tone) on the market (in the labs?) today,
> and how well does it perform (compression ratio). Can a working version be
> downloaded for testing/comparison purposes? What are the best algorithms
> for lossless compression of images containing e.g. diagrams, text etc, and
> how do these perform (downloads?)? Are there any compression algorithms for
> lossless compression of video, and how do these perform?
Best continuous-tone image compressor wrt compression ratio? CALIC.
For other types of images (e.g. GIF: 256-colormap) the answer is
Quote:> I've heard that an algorithm by the name LOCO is supposed to be very good,
> anybody heard of it?
It is a very good tradeoff between good compression ratio, low memory
consumption and high coding/decoding speed.
Quote:> Who as interest in lossless image compression? That is, who needs lossless
> compression? I'm interested in knowing what the market is for a lossless
> image compressor.
Medical imaging. And they tend to use images of 256 over 4096 to 65536
gray levels (some people claim to see more than 8 bits). Some of the
least-significant bits usually are noise. And the underlying physics,
scanners and software causes a much greater diversion in the imagery
than the undetectable loss introduced by near-lossless or lossy
compression schemes. It's mainly a matter of responsability and legal
arguments. Another reason for lossless compression might be that though
our eyes don't see the subtle gray-levels, statistical image processing
(or others) might and you never know what the images from today will be
used for in the future.
Other fields might include: prepress imagery (especially the high-end)
and digital printing, satellite images.
Many companies/organizations are very reluctant to compression
algorithms which are covered by patents, so don't expect to make a lot
of money from a new world-record breaking algorithm which is 10% better
than the state-of-the-art. The economical value of a good compression
scheme lies in its "added value": fast, transparent in use, portable to
a whole gamma of architectures ranging from palm-top computer
communication to really huge archiving systems, applicable to all types
of data, progressive reconstruction, randomly accessible, etc. By
introducing lossless compression, people only want the benefits and not
The research field of lossless compression is comparable to trying to
achieve the "0 Kelvin point". By tuning and optimizing, you could do it
maybe 10% or 20% better than CALIC, but never expect to achieve twice as
good compression as CALIC does. No one can compress noise.
Koen Denecker RUG - ELIS - MEDISIP
Tel: ++32(9)264.89.08 GSM: ++32(477)55.39.04 Fax: ++32(9)264.35.94
University of Ghent - Department of Electronics and Information Systems
Sint-Pietersnieuwstraat 41 B-9000 Gent Belgium