Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!columbia!rutgers!ll-xn!mit-eddie!genrad!decvax!mcnc!rti-sel!ge-rtp!ge-dab!ponte
From: ponte@ge-dab.UUCP (Ponte)
Newsgroups: net.wanted.sources,net.graphics
Subject: Re: Half-Tone Program for Monochrome Suns Wanted
Message-ID: <410@ge-dab.UUCP>
Date: Tue, 21-Oct-86 10:05:46 EDT
Article-I.D.: ge-dab.410
Posted: Tue Oct 21 10:05:46 1986
Date-Received: Thu, 23-Oct-86 18:53:14 EDT
References: <667@nike.UUCP>
Distribution: world
Organization: GE Simulation & Controls, Daytona Beach, FL
Lines: 22
Xref: mnetor net.wanted.sources:2482 net.graphics:1374

In article <667@nike.UUCP>, watson@nike.UUCP (John S. Watson) writes:
> /*********************************************************************/
> 
> Does anybody have a public domain half-tone program that will take
> 3 image files (Red Green and Blue), and produce a half-tone image/file, 
> suitible for displaying in monochrome screen?  
> 

There is a simple formula to convert a color value (RGB) to a monochrome
value (Intensity).  It is the same way a color picture is shown on a black
and white TV.  The equation is:

          I = RED * 0.30 + GREEN * 0.59 + BLUE * 0.11

The percentage values used for multiplying all add up to 1.  (.3+.59+.11).
If this information does indeed answer your question, it wouldn't be hard
for you to write your own program to read in a color value (RGB) and spit
out an intensity value (I).

My source of information is "Introduction to Computer Graphics" by Foley
and VanDam.  If you have access to a copy of this book you may want to 
look at pg. 613, (Chapter 17.15).