An algorithm for the construction of a critical clustered exponential code for use in image data compression

The author demonstrates that the compression ratio of the adaptive block/location coding (ABLC) technique can be increased by an average of 37% if the original image is preprocessed and if rectangles, not squares, are location coded. A statistical data compression based on a modified exponential code, called the critical clustered exponential code (CCEC), is of interest for time-critical applications. An algorithm for the construction of the CCEC is presented. The author demonstrates that compression ratios within a few percent of those achievable using a Huffman code can be reached using a CCEC, and that the decoding time is on the order of 20% faster. Using the CCEC for the location coding for the modified ABLC reduced the ABLC decoding time by 16%. Exclusive OR image preprocessing and ABLC with CCEC location coded 4×2 basic picture block is implemented in Geac mainframes and terminal devices to store and retrieve lossless image data