getpixel
Section: Allegro manual (3)
Updated: version 4.2.2
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NAME
getpixel - Reads a pixel from a bitmap. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
int getpixel(BITMAP *bmp, int x, int y);
DESCRIPTION
Reads a pixel from point (x, y) in the bitmap.
RETURN VALUE
Returns -1 if the point lies outside the bitmap (ignoring the clipping
rectangle), otherwise the value of the pixel in the color format of the
bitmap.
Warning: -1 is also a valid value for pixels contained in 32-bit bitmaps
with alpha channel (when R,G,B,A are all equal to 255) so you can't use
the test against -1 as a predicate for such bitmaps. In this cases, the
only reliable predicate is is_inside_bitmap().
To extract the individual color components, use the getr() / getg() /
getb() / geta() family of functions.
SEE ALSO
putpixel(3),
_getpixel(3),
is_inside_bitmap(3),
getr(3),
getg(3),
getb(3),
geta(3),
ex12bit(3),
exalpha(3),
exflame(3),
exlights(3)