From: "Bengt Rosenberger" <rosenberger AT berlin DOT snafu DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: allegro getpixel()-problem!
Date: Tue, 28 Apr 1998 15:36:31 +0200
Organization: Unlimited Surprise Systems, Berlin
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Message-ID: <6i4m14$da7$1@unlisys.unlisys.net>
NNTP-Posting-Host: n31-107.berlin.snafu.de
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

I want to use a button (it's a bitmap(125x75)) in the middle of the screen.
Now I
blit a black/white-bitmap of that button directly behind the originally one.
When the button is pressed with left mouse button I try to check if the
color behind is white. I use:

col = getpixel(buttonbw, mouse_x, mouse_y);
if (col = 255)
    button_pressed();

When the button is pressed in the middle of the screen, the return col
is -1. But if I press the left mouse button in the upper left corner, the
return col is 255 but the b/w button is in the middle of the screen. And it
seems as the button would be in the upper left corner but is shown in
SCREEN_W / 2 - button->w/2, SCREEN_H / 2 - button->h/2

Please mail me at:
rosenberger AT snafu DOT de

Thanks a lot!