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From: wes@uh.msc.umn.edu (Wes Barris)
Newsgroups: comp.graphics
Subject: Re: What's the best colormap for a 24 bit color image?
Message-ID: <2383@uc.msc.umn.edu>
Date: 17 Aug 90 19:48:52 GMT
References: <15019@samsung.samsung.com>
Sender: news@uc.msc.umn.edu
Reply-To: wes@msc.edu
Organization: Minnesota Supercomputer Center
Lines: 25

In article <15019@samsung.samsung.com>, mdich@schizo.samsung.com (Mike
Dichiappari) writes:
> I want to display some 24 bit color images on my Mac and Sun.  Both
> machines have 8 bit display boards.
> 
> What is a good algorithm or method for determining the best (or a
> very good) colormap given a 24 bit image?  I'd like the algorithm
> to work for various sized colormaps (although 256 will be most
> commonly used).
> 
Popular algorithms for doing this are the "median-cut algorithm" or the
"variance-based method".  Both are used to quantize 24 bit images down to
8 bit mapped images.  Depending on the image format you wish to use, I
would check out either the PBMPLUS toolkit or the Utah Raster Toolkit.
They both are very useful toolkits.  PBMPLUS is available at
expo.lcs.mit.edu:contrib/pbmplus.tar.Z and the Utah Raster Toolkit is
available at cs.utah.edu:pub/urt-3.0.tar.Z

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