Message-ID: <8D53104ECD0CD211AF4000A0C9D60AE361DF84@probe-2.acclaim-euro.net>
From: Shawn Hargreaves <ShawnH AT Probe DOT co DOT uk>
To: djgpp AT delorie DOT com
Cc: mmurrian AT gate DOT net
Subject: Re: ALLEGRO: Using masks ...
Date: Tue, 9 Mar 1999 12:45:05 -0000 
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Reply-To: djgpp AT delorie DOT com

Matt Murrian writes:
> What I want is this ... I have 3 images ... 2 are normal images and 
> 1 is a mask. The mask contains 255,0,255 (transparent color) on one 
> side, and white on the other. I want to draw image 1 over the 
> transparent color and image 2 over the white

There's no built in Allegro support for this kind of masking. You 
could bodge the translucent drawing mode to do it by using some custom
mapping tables and a couple of drawing passes, but that would be
terribly slow. I think your best bet is to write your own drawing
code for doing this: see the "direct video memory access" section
in the docs for details of how to do that.


	Shawn Hargreaves.