Film grain is simulated in an output image using pre-established blocks of film grain from a pool of pre-established blocks. Successive film grain blocks are selected by matching the average intensity of a block from the pool to the average intensity of a successive one of a set of M×N pixels in an incoming image. Once all of the successive pixel blocks from the image are matched to selected film grain blocks, the selected film grain blocks are “mosaiced”, that is composited into a larger image mapped to the incoming image.