1. A method of applying a flat region filter to pixels in an image, comprising: dividing a region of the image into pixel blocks; determining block average pixel values for each of the pixel blocks; and using the determined block average pixel values to smooth a value of a first pixel located outside of the region and downstream of the pixel blocks, wherein the block average pixel values are used to smooth the value of the first pixel only if the first pixel differs in value with each of the block average pixel values by less than a threshold value.