1. A method for processing a frame of image data comprising the steps of: partitioning said frame of image data into a plurality of partitioned blocks of pixels; identifying each partitioned block as being color variant or color invariant, including identifying partitioned blocks of pixels as being of a user-specified classification, and storing information which identifies those partitioned blocks identified as being of the user-specified classification; storing color values of at least some of said pixels; storing information which identifies each partitioned block as being color variant or color invariant; and compressing the partitioned blocks of pixels of the frame of image data in groups by retrieving the information which identifies each partitioned block as being either color variant or color invariant, controlling a retrieval of said color values in response to said retrieved information, and retrieving stored color values for all pixels in each group of partitioned blocks when any one of said partitioned blocks within the group is identified as being color variant.