Reads a pixel from a bitmap. allegro game programming library.
#include <allegro.h>
int getpixel(BITMAP *bmp, int x, int y);
Reads a pixel from point (x, y) in the bitmap.
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.
putpixel(3alleg4), _getpixel(3alleg4), is_inside_bitmap(3alleg4), getr(3alleg4), getg(3alleg4), getb(3alleg4), geta(3alleg4), ex12bit(3alleg4), exalpha(3alleg4), exflame(3alleg4), exlights(3alleg4)