Path: utzoo!utgpu!water!watmath!clyde!att!alberta!ubc-cs!uw-beaver!cornell!mailrus!ames!hc!hi.unm.edu!cyrus
From: cyrus@hi.unm.edu (Tait Cyrus)
Newsgroups: comp.graphics
Subject: RGB -> CMY -> hardcopy
Keywords: RGB,CMY,printer,halftoning
Message-ID: <23632@hi.unm.edu>
Date: 28 Aug 88 21:10:03 GMT
Organization: U. of New Mexico, Albuquerque
Lines: 33


I am working on a utility that takes an RGB image (3 files, 1 for R, 1
for G and 1 for B), converts it halftones, and then converts it to CMY
so that I can print it on a color CMYB versatec printer we have.

My problem is that the colors don't seem to be coming out looking
correct.  Cyan comes out looking blue, blue comes out looking purple,
green comes out too dark, etc.....

Several people have suggested looking into using chromaticity.  Looking
at Foley and Van Dam's "Fundamentals of Interactive Computer Graphics",
as well as Roger's "Procedural Elements for Computer Graphics", I find
that I am totally lost.

Are there scale factors I need to multiply with my colors to get them
to come out looking correct on my CMY printer?

Can I use chromaticity concepts to solve my problem?

Thanks in advance for any comments, pointers to other books, pointers
to PD software that already does this, etc....

The solution is probably staring me right in the face, all I need is
someone to shove my face in it. :^)

---
Tait Cyrus   (505) 277-0806
University of New Mexico
Dept of Electrical & Computer Engineering 
Albuquerque, New Mexico 87131
	e-mail:      
	cyrus@hi.unm.edu or
	cyrus%hi.unm.edu@ariel.unm.edu