Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcdc!hpfcdq!jlg
From: jlg@hpfcdq.HP.COM (Jeff Gerckens)
Newsgroups: comp.graphics
Subject: Re: RGB -> CYMK conversion
Message-ID: <390026@hpfcdq.HP.COM>
Date: 30 Mar 89 02:12:18 GMT
References: <28994@sri-unix.SRI.COM>
Organization: Hewlett-Packard - Fort Collins, CO
Lines: 20

> Does someone have some good ideas and/or snippets of C code
> for doing RGB -> CYMK conversion? TIA.  ...doug beck
> dbeck@unix.sri.com

 A good basic coverage of color space conversions appears in
 both Rogers and Foley and Van Dam's texts on graphics, although
 care should be taken with older revisions.  They do contain some
 errors.

 The basic conversion for RGB -> CMY is:

	  [ C M Y ] = [ 1 1 1 ] - [ R G B ]
 
 The K is black and is used when C=M=Y=1 (or within some user defined
 tolerance).  This is because most inks used don't do a very good job
 at mixing to form black.

 -- Jeff Gerckens, Hewlett-Packard Graphics Technology Division
	jlg%hpfcrg@hplabs.hp.com 
	"Nice computers don't go down."