Compression Software

Brad Jones brad at ahi.pbrc.hawaii.edu
Sun Dec 15 04:50:46 EST 1991


In article <1991Dec11.105454.5317 at nic.funet.fi>, harper at nic.funet.fi (Rob Harper) writes:
> In <9112040401.AA01955 at mendel.llnl.gov.> greg at MENDEL.LLNL.GOV writes:
> 
> *>Would anyone know of a good (completely reversible) compression
> *>routine suitable for running on a SUN, on files produced by the
> *>Molecular Dynamics PhosphorImager ?

[section deleted]

> I have done some WAIS queries on the availability of JPEG and there
> is quite alot of information about. I saved four of the most interesting 
> posts which gives pointers to those who want to look at JPEG further.
> 
> From what I have seem over the past couple of days really good compression
> rates can be achived, but as I said before it works best on "real world"
> pictures and is not suited for "cartoons"

I think this requires some clarification.  Jpeg was designed to achieve
high compression on images by taking advantage of psychophysical
properties of human vision.  As such, it is a "lossy" compression
technique.  If you have a bitmap of your lab picnic jpeg would be a
fine way to store it compressed.  The losses associated with jpeg
compression will probably not be obvious to most observers.  If you are
compressing valuable data that will be subjected to quantitative
analysis at some point jpeg is _definitely_ _not_ an acceptable
method.

I think the best (though not the fastest) compression is currently
achieved by lharc (or lha) which is available in the public domain.
There are sources and executables for both unix and msdos.

-- 
		Brad Jones  bjones at ahi.pbrc.hawaii.edu
			    bjones at uhunix.bitnet




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