1. A method for identifying edge pixels in a rendered image that consists of a plurality of tiles, each of the plurality of tiles consisting of a plurality of pixels, the method comprising: accessing data, using a processor, to determine whether or not a selected tile in the plurality of tiles is fully compressed; and identifying, using the processor, the selected tile either as including only non-edge pixels responsive to a determination that the selected tile is fully compressed, or as including one or more edge pixels responsive to a determination that the selected tile is not fully compressed.