Newsgroups: comp.graphics
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From: fsset@bach.lerc.nasa.gov (Scott E. Townsend)
Subject: Question regarding YIQ color system
Message-ID: <1991Jun21.203745.8532@eagle.lerc.nasa.gov>
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Organization: Nasa Lewis Research Center ( Cleveland )
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Date: Fri, 21 Jun 1991 20:37:45 GMT
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I've been experimenting with different color systems and I'm having some
trouble translating to/from YIQ.  I've looked in Foley & Van Dam (1st edition)
and it wasn't quite enough help.

Specifically, is there some relation or limit for the I and Q components?
If I take an arbitrary set of Y, I, and Q I don't see a smooth mapping
to RGB.  It appears that there's some relation/constraint between I & Q
(which would make sense if I & Q stand for in-phase & quadrature, but that's
 some radar background sneeking-in.  I haven't seen a definition for what
 the I and Q stand for)

From the definition in Foley & Van Dam things should be smooth, but displaying
the results of yiq_to_rgb() at 8 bits per component doesn't look so smooth.
(yiq_to_rgb is taken from SGI's libgutil.a.  I've seen the source and it
looks simple & reasonable)

Any enlightenment from the net?

-- 
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Scott Townsend               |   Mail Stop: 5-11
NASA Lewis Research Center   |   Email: fsset@bach.lerc.nasa.gov
Cleveland, Ohio  44135       |