1. A computer-implemented method for drawing a first image on top of a second image, the method comprising: receiving transparency information for a first pixel in the first image, wherein a set of bits represents a color of the first pixel; modifying, using a computer, a subset of the set of bits based on the transparency information for the first pixel; drawing the first pixel of the first image if the subset of the set of bits indicates that the first pixel is opaque, wherein the first pixel is drawn using a color that is determined using all of the bits in the set of bits; and drawing a second pixel of the second image if the subset of the set of bits indicates that the first pixel is transparent, wherein the second pixel in the second image corresponds to the first pixel in the first image.