EFFICIENT STORAGE OF DITHERED RASTAR IMAGE DATA IN A PRINTER OR THE LIKE

Already stored uncompressed raster data are selectively compressed before any new raster data can be processed and stored. Both compressed and uncompressed raster data is preferably stored in the same size blocks, and the Raster Objects are preferably divided at Render Swath boundaries. Assuming that the Raster Object data has been or will be compressed by means of a known dither matrix, that dither matrix is used in the compression process to eliminate all but the data essential to reconstruct the dithered image, and the pixels of the original image are preferably successively processed along a predetermined scan path and the resultant linear pixel array is divided into successive runs which may each be encoded such that when those encoded runs are assembled into a replica of the original image and both the original image and the replica image are dithered with the same predetermined dither matrix, the dithered replica image is identical to the dithered original image. The dither-matrix based compression of the raster data is preferably followed by Golomb Rice compression.