pixel_at(15,15).should_be_of_color 0xffffff
pixel_at(4,50).should_be_of_color 0xff0000
pixel_at(21,52).should_be_of_color 0x00ff00
pixel_at(15,15).should_be_of_color 0xffffff
pixel_at(4,50).should_be_of_color 0xff0000
pixel_at(21,52).should_be_of_color 0x00ff00