[Allegro 5] Problem z funkcja Sprawdzania Pixeli

ALLEGRO_DISPLAY * display = al_create_display( 800, 600 );
ALLEGRO_BITMAP * bmp = al_get_backbuffer( display );
ALLEGRO_LOCKED_REGION * lock = al_lock_bitmap( bmp, ALLEGRO_PIXEL_FORMAT_ANY, ALLEGRO_LOCK_READWRITE );
int r, g, b;
ALLEGRO_COLOR color = al_get_pixel( bmp, x, y );
al_unmap_rgb( color,( unsigned char * ) & r,( unsigned char * ) & g,( unsigned char * ) & b );
al_unlock_bitmap( bmp );
if( r == 255 && g == 255 && b == 255 )
{
    //
}