Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!cornell!uw-beaver!ubc-cs!alberta!calgary!cpsc!jevans
From: jevans@cpsc.ucalgary.ca (David Jevans)
Newsgroups: comp.graphics
Subject: Re: Palette Optimization
Summary: color space reduction
Message-ID: <356@cs-spool.calgary.UUCP>
Date: 19 Dec 88 20:41:51 GMT
References: <AXco9BF28k-0E78UVK@andrew.cmu.edu> <12745@cup.portal.com>
Sender: news@calgary.UUCP
Lines: 18

Several articles have been written on choosing the best N colors
from >N.  I don't have them in front of me right now, but there was
one in SIGGRAPH '84 (I believe, it may have been another year) on
reducing a 24 bit color space down to a smaller number of bits.
A median split algorithm is presented.

An article in the proceedings of CGI '88 (Springer-Verlag press)
describes an octree reduction of the 24 bit color cube down to
however many bits you have available.  I implemented this and posted
the source here a couple of months ago.  I use it for displaying
24bit (16 million colors) images on an 8bit color SUN (256 colors).

Maybe this helps?

Note: Picking the most used 256 colors doesn't work.  You want to
      chose the best colors (this may involve making new colors
      which may not be present in your source image).
David Jevans, U of Calgary Computer Science, Calgary AB  T2N 1N4  Canada
uucp: ...{ubc-cs,utai,alberta}!calgary!jevans