From:	Xavier Prat Recio <prat AT mmt DOT upc DOT es>
Newsgroups:	comp.os.msdos.djgpp
Subject:	grx22 bug???
Date:	Mon, 11 May 1998 12:09:49 +0200
Organization:	Universitat Politècnica de Catalunya
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To:	djgpp AT delorie DOT com
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Hi everybody

I don't know wether I've found a bug in grx22, which also stands for
grx20, or it's just my little knowledge of that library which makes me
think so. Let's explain what happens.

I am building a numerical solver programa with djgpp2.0 which also tries
to print graphically its results. When doing so, I convert each
numerical value, double precission, into a rgb 'color' ranging from 0 to
255, that is GrNumColors()-1. The fucntion I use is
c=GrAllocColor(r,g,b). Then, I also implement a graphical reading
procedure which qeries for the color represented in each pixel and
converts that color into its correct numerical value. However, when
performing that action with GrQueryColor(c,&r,&g,&b) I found that those
rgb values set to GrNumColors()-1, that is 255 in my graphics mode, once
read become 252!!!. Those set to 0 are 0 equally, but what happen to
those in between?

If it's any help, my graphics board is a S3 with 1Mb.

Any hint?. Let me know, please.

Xavier Prat Recio
Universitat Politècnica de Catalunya

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