getpixel - Reads a pixel from a bitmap. Allegro game programming library.

       Reads a pixel from point (x, y) in the bitmap.

       getpixel - Reads a pixel from a bitmap. Allegro game programming library.

       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)

Allegro                                           version 4.4.3                                getpixel(3alleg4)

#include<allegro.h>intgetpixel(BITMAP*bmp,intx,inty);