Re: Differential intra-interchannel filters for RGB images lossless compression
- From: giorgio.tani@xxxxxxxx
- Date: 12 Dec 2005 05:57:18 -0800
> if there is a better alternative to png, that manages to gain some
> popularity (eg: gimp support), I will be interested.
AFAIK there are projects to use better compression algorithms on PNG, I
read something about using the 7-Zip's optimized implementation of
deflate that gives slightly better compression.
PNG differential filters seem (referring to Waterloo Colorset) to be
significantly less efficient than JPEG-LS/JPEG2000 (lossless) filters
on the photographic images, but seem dramathically more efficient on
computer graphic images (according to literature results in PNG
documentation and with some tests I just made with the ISA compressor
linked by Nils, with .jp2, .hck and .isa formats), so, depending on the
test set, PNG may seem more or less efficient than lossless JPEG
related...
Shifting from filter stage to compression stage, as you may note in my
work, the compression algorithm chosen is very important in determining
output size, with PAQ giving awesome results at the cost of very high
computational complexity and with LZMA seeming a reasonable tradeoff
between compression and speed; however, even with a compressor powerful
like PAQ a proper filtering of the input data is very important to
achieve better results than compression on plain, unfiltered data.
This is consistent with the projects about giving PNG a better
compressor limited by a tradeoff in speed that on today's machine would
be acceptable.
.
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