Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!ucsfcgl!pixar!mccoy
From: mccoy@pixar.UUCP (Daniel McCoy)
Newsgroups: comp.graphics
Subject: Re: Optimal palette selection for dither?
Message-ID: <9231@pixar.UUCP>
Date: 17 Feb 90 02:22:24 GMT
References: <10675@primitive.ADS.COM> <SPENCER.90Jan30042240@spline.eecs.umich.edu>
Reply-To: mccoy@pixar.UUCP (Daniel McCoy)
Distribution: na
Organization: Pixar -- Marin County, California
Lines: 16

In article <SPENCER.90Jan30042240@spline.eecs.umich.edu> spencer@eecs.umich.edu (Spencer W. Thomas) writes:
> ...  We concluded that if you were going to do some sort of
>error-propagation dither (e.g. Floyd-Steinberg), that you might want
>to make sure to pick representative colors that spanned the convex
>hull of your actual colors.  This way your error propagation would
>never diverge.

You would have to know the maximum possible propagated error and expand 
the convex hull by that much to insure that the error never diverges.  
(You could control it by clamping.)
Even then there can still be large gaps inside of the convex hull where
the error can get noticable.
An "optimal" pallete is hard to define, you remove error from one place
and it squirts out somewhere else.

Dan McCoy  {ucbvax,sun}!pixar!mccoy