Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!sun-barr!newstop!sun!falk
From: falk@sun.Eng.Sun.COM (Ed Falk)
Newsgroups: comp.graphics
Subject: Re: Color quantization: flesh tones
Keywords: color rgb quantization flesh tone preferences histograms
Message-ID: <124742@sun.Eng.Sun.COM>
Date: 15 Sep 89 00:33:41 GMT
References: <6087@pt.cs.cmu.edu>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 23

> Has anyone experimented with psychological color preferences in
> quantizing using Heckbert's median cut?  Here's an example problem:
> 
>     In some images containing people's faces, where the face is
>     only a small part of the image, very few colors are assigned
>     to "flesh" color.  The result is banding/loss of resolution in
>     an area of the image that is interesting to the viewer out of
>     proportion to its relative size.  The problem is most severe
>     when quantizing to 32 or fewer colors.
> 

Here's a thought; try converting RGB to the NTSC IYQ coordinates
and quantize in IYQ space.  I suggest this because NTSC chose
the Y axis to be biased towards flesh tones and TV pictures transmit
more power along that axis than along the Q axis (I is intensity).

I'm sorry, but I don't have the transformation matrix from RGB to IYQ handy.

-- 
		-ed falk, sun microsystems, sun!falk, falk@sun.com

  "If you wrapped yourself in the flag like George Bush does, you'd
  be worried about flag-burning too"