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From: thomas%gr.utah.edu@cs.utah.edu (Spencer W. Thomas)
Newsgroups: comp.graphics
Subject: Re: What's the best colormap for a 24 bit color image?
Message-ID: <1990Aug19.152331.27847@hellgate.utah.edu>
Date: 19 Aug 90 21:23:31 GMT
References: <15019@samsung.samsung.com> <5738@adobe.UUCP>
Organization: University of Utah CS Dept
Lines: 30

[I'm posting this from Utah because outgoing news from umich is not
working at the moment.  Please reply to the address below.]

Steve Hawley writes: 
>  A good general reference for dithering
> is "Digital Halftoning" by Robert Ulichney published by MIT press.  I
> don't recall if it has anything about color, though.

No, Ulichney's book doesn't say anything about color (well, nothing
useful).  'Twould be nice if someone wrote as good a book about color
quantization and dithering.

The Utah Raster Toolkit has several tools that do color quantization
(and dithering).  These are
	to8	Very simple ordered dither to a fixed colormap.  Quick
		but dumb.
	mcut	Median cut with optional Floyd-Steinberg dither.  Will
		quantize to any number of colors (<= 256).
	rlequant 
		Variance based quantization with optional
		(Floyd-Steinberg) dither.  Will quantize to any number
		of colors (<= 256).
	rledither
		Floyd-Steinberg dither with optional edge enhancement.
		Takes a color image to a given set of colors.

=Spencer W. Thomas 		EECS Dept, U of Michigan, Ann Arbor, MI 48109
spencer@eecs.umich.edu		313-936-2616 (8-6 E[SD]T M-F)

=Spencer   (spencer@eecs.umich.edu)