Compression Software

John A Mess jamess at athena.mit.edu
Fri Dec 6 14:06:57 EST 1991


In article <1991Dec4.083835.23158 at nic.funet.fi> harper at convex.csc.FI (Rob Harper) writes:
>In <1991Dec4.043820.7565 at alw.nih.gov> donnel at helix.nih.gov (Donald A. Lehn) writes:
>
>
>>	I'm afraid that you will be hard pressed to compress these files.
>>I'm pretty sure that they are TIFF files and as such are about as
>>compressed as they can get.  (You can compress the header info though and
>>that is how you squeezed the 3Mb out of the file.)
>
>This is also true for GIF files, they are already compressed, so there is
>not much point trying to compress them further... and in some cases if
>you do try it you will get a BIGGER file than you started with.
>
I am not an authority, however I have been following the ongoing discus-
sions in alt.sources.pixutils, alt.comp.graphics, etc. regarding this
issue.  From what I've gleaned, JPEG utilities can lead to an 18:1 com-
pression with small loss and higher compressions for greater loss of
picture quality.  Since JPEG is 24bit/pixel based, it should be relatively
small visual loss.  The PBM utilities available by ftp offer many form
conversions.  You might want to tap their expertise.




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