Request for algorithm to reduce number of used colours...

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#146

From: Angus "Fluffy" Rae
Date: Wed, 22 Jul 1992 15:33

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Hi. 

A friend of mine has written a program to take (on an Atari ST) a 512
colour picture produced by GFA-Raytrace and reduce the number of colours
to 16 to make a standard Degas picture. This he does by simply counting
the number of times each of the 512 possible colours are used and using
the 16 most popular, converting the rest to the closest of the popular
16. This is a) slow and b) doesn't give the 16 most _useful_ colours.

Can anyone point me at an algorithm for this sort of colourmap
reduction? a) and b) above might be mutually exclusive - a fast routine
that is pretty kludgy as far as colour selection goes would also be
useful. I've heard the phrase "mean-cut" or something like it in
reference to b).

Thanks in advance for any help.

-- 
Angus G Rae, the Cuddly Vampire Teddy Bear [asr@castle.edinburgh.ac.uk]
CATHY VoiceMail, Computer Science Dept., Edinburgh University
"I'm on the run from the Facist Police with a murderer and
 a mass murderer and a man in a bri-nylon shirt."  Rimmer, Red Dwarf V

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Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!uknet!edcastle!asr
From: asr@castle.ed.ac.uk (Angus "Fluffy" Rae)
Newsgroups: sci.image.processing
Subject: Request for algorithm to reduce number of used colours...
Message-ID: <24050@castle.ed.ac.uk>
Date: 22 Jul 92 15:33:33 GMT
Distribution: sci
Organization: CATHY_VoiceMail_Project
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