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From: johnston@adhawk.Eng.Sun.COM (Scott Johnston)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Query:  question about color on the mac...
Message-ID: <139442@sun.Eng.Sun.COM>
Date: 24 Jul 90 15:30:18 GMT
References: <10754@odin.corp.sgi.com> <23410@megaron.cs.arizona.edu>
Sender: news@sun.Eng.Sun.COM
Organization: Sun Microsystems, Mt. View, Ca.
Lines: 53

In article <23410@megaron.cs.arizona.edu> gerhard@cs.arizona.edu (Gerhard Mehldau) writes:
>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.
>>
>> [stuff deleted...}
>>
>> 	...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?).
>
> [stuff deleted...]
>
>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

I have been flailing miserably with this, too, so correct me if
I am wrong.  Isn't the color table created with the above set of 
commands still dependent upon the underlying device CLUT?  And
this device CLUT has not changed?  So, the way I understand it,
the Color Manager will attempt to find the closest RGB matches
between this newly created CLUT and the device CLUT.

What if you wanted to do 256-tone Gray Scale?  Wouldn't you need
to go in and modify the device's CLUT directly in order to get
this wide range of grays?

Just worth mentioning:  modifying the device CLUT gets ugly.
All the cached fonts, etc become invalidated, and I have had a 
difficult time trying to bring to machine back to the state it was
in before I messed with the CLUT.  Maybe there's a lesson here...:^)

Thanks in advance for any advice and/or help.

sj
johnston@portia.stanford.edu
johnston@adhawk.sun.com
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