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(3alleg), _getpixel(3alleg), is_inside_bitmap(3alleg),
getr(3alleg), getg(3alleg), getb(3alleg), geta(3alleg),
ex12bit(3alleg), exalpha(3alleg), exflame(3alleg), exlights(3alleg)