Path: utzoo!attcan!uunet!mailrus!ncar!asuvax!noao!arizona!gerhard
From: gerhard@cs.arizona.edu (Gerhard Mehldau)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Query:  question about color on the mac...
Summary: try this...
Message-ID: <23410@megaron.cs.arizona.edu>
Date: 23 Jul 90 20:24:51 GMT
References: <10754@odin.corp.sgi.com>
Organization: U of Arizona CS Dept, Tucson
Lines: 50

In article <10754@odin.corp.sgi.com>, myoung@joker.sgi.com (Mark Young) writes:
> 
> I'm working on a class project that does simple color halftoning, and I
> want to be able to set up the color table and then write color index values
> to the pixels on the screen.
> 
> I looked over the color stuff in volume five and it wasn't obvious how 
> you would go about doing this...everything seemed to want RGB colors which
> would then get mapped for you.
> 
> is this easier than it looks?  can someone give me an RTFM reference to 
> volume V that explains this...
> 
> thanks.
> 
> 	...myoung

I have struggled through this, too - IM V and the
32-Bit QuickDraw documentation really isn't very
clear on this topic (Apple, are you listening?).

First, you need to create a color table - either
within your program, or as a resource which you
can read in from your resource file.  You then
convert the color table to a palette (with all
entries allocated as pmTolerant+pmExplicit), and
associate the palette with the window(s) in question.
You can then create an offscreen pixmap, set the
individual pixels to whatever index you want, and
do a CopyBits() to put them on-screen.

The code for the color table/palette stuff should
look like this (note that this code requires 32-Bit
QuickDraw to be installed):

CTabHandle gTable;
PaletteHandle gPalette;
gTable = GetCTable(kColorTable);	    /* read in from resource file */
gPalette = NewPalette((*gTable)->ctSize+1,gTable,pmTolerant+pmExplicit,0);
SetPalette((WindowPtr)(-1),gPalette,TRUE);  /* make default palette */

Good luck!

- Gerhard

-- 
-> Gerhard Mehldau
   Dept. of Computer Science	internet: gerhard@cs.arizona.edu
   University of Arizona	uucp:     {cmcl2,noao,uunet}!arizona!gerhard
   Tucson, AZ 85721, U.S.A.	at&t:     +1 (602) 621-4632