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From: pepke@gw.scri.fsu.edu (Eric Pepke)
Newsgroups: comp.sys.mac.programmer
Subject: Re: CLUT problem
Message-ID: <615@sun13.scri.fsu.edu>
Date: 4 Sep 90 21:32:25 GMT
References: <20089@well.sf.ca.us>
Sender: news@sun13.scri.fsu.edu
Organization: Florida State University, but I don't speak for them
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In article <20089@well.sf.ca.us> crunch@well.sf.ca.us (John Draper) writes:
>   We are having some problems in dealing with CLUT+s.   We are 
developing software  
> (A TV Board) which has to fill in a CLUT by hand in order to meet our 
stringent
> performance needs (Live Video).   In page 145 in IM Vol 5,  in the 
description of 
> the "RestoreEntries" call,  the 3rd paragraph mentions "this may cause 
RGBForeColor 
> to act strangely".   Is there a Tech note that describes this problem,   
and how 
> do I get around it,  because it certainly does what the manual says 
> (IE:   Act strangley).

The reason RGBForeColor behaves strangely is that RestoreEntries does not 
reset the inverse table, which is used by RGBForeColor to get close to the 
correct color.  You have to make a new inverse table using MakeITable, 
which is described on page 142.  Of course, then you've got to stick it in 
the gDevice.

I use an offscreen gDevice with offscreen 8-bit pixmaps, which are filled 
using Color2Index.  I CopyBits the pixmaps onto the screen into a window 
with palettes the same as the desired color table, all tolerant colors 
with a tolerance of 0.  It works fine.

Apple's quantization scheme is OK but not perfect.  If you want to, you 
can write your own search procedure.  All the really good ones are slow.

Eric Pepke                                    INTERNET: pepke@gw.scri.fsu.edu
Supercomputer Computations Research Institute MFENET:   pepke@fsu
Florida State University                      SPAN:     scri::pepke
Tallahassee, FL 32306-4052                    BITNET:   pepke@fsu

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