A hybrid system for real-time lossless image compression

This paper describes a hardware design-for a real-time lossless image compression system based on the organized matrix scanning methodology, SCAN. SCAN is a special purpose context-free language which describes and generates a wide range of array accessing algorithms from a short set of simple ones. These algorithms may represent scan techniques for image processing, but at the same time they stand as generic data accessing strategies. In this system, an 8-bit gray scale image is transformed into an error image using differential pulse code modulation (DPCM). This error image is subdivided into 64 x 64 pixel blocks, and the bit planes associated with each block are scanned with four different scan sequences. For each image block and each bit plane, the results of the scan which most closely matches the grain of the image is Huffman coded for transmission. High data rates associated with the real-time requirement make a software solution impossible. Pipelining is employed to simultaneously perform the functions of image input, DPCM, SCAN based run-length encoding, Huffman coding and output. Parallel processing is utilized to perform the scanning and run-length encoding on all bit planes simultaneously. In addition to compression, the use of the SCAN methodology provides good data encryption, and can be extended to include data hiding or watermarking (C) 2001 Published by Elsevier Science B.V.