1. A method for compressing image data, comprising the steps of: identifying a plurality of image tiles within a composite image data set, wherein a mask data value and a valid data value are associated with each of one or more pixels within the composite image data set and wherein the image tiles are identified through analysis of a plurality of mask data values and valid data values; characterizing an image data group within at least one image tile within the plurality of image tiles as one of linework image data or continuous tone image data; and encoding the image data group for at least the one image tile, wherein the image data group is encoded by an encoding algorithm selected based upon the characterization of the image data group.