Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!eos!jbm
From: jbm@eos.UUCP (Jeffrey Mulligan)
Newsgroups: comp.graphics
Subject: Re: Color lookup tables
Message-ID: <3166@eos.UUCP>
Date: 11 Apr 89 20:04:06 GMT
References: <1322@gwusun.gwu.edu>
Distribution: usa
Organization: NASA Ames Research Center, California
Lines: 23

From article <1322@gwusun.gwu.edu>, by viraf@gwusun.gwu.edu (Viraf Bankwalla):

>   I have written a program that converts sun raster files to PICT
> format, but the colors are off.  The sun uses 8 bit values in its
> color lookup table, while the Mac uses 16 bit values.  I simply shift
> the RGB components left 8 times - but that introduces green in some
> parts of the image, that should be orange.

I suspect the problem is caused by different nonlinearities (gamma
functions) in your two monitors.  If the monitors were both
perfectly linear, then what you did should have worked.

The best way to go would be to calibrate each monitor
(i.e., measure the luminance produced at each gun setting).
Then you can convert from the hardware LUT settings to luminance,
and then back again to the other hardware.


-- 

	Jeff Mulligan (jbm@aurora.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035
	(415) 694-6290