Combined Symbol Matching-A New Approach To Facsimile Data Compression
Wen-hsiung Chen, John L. Douglas, Robert D. Widergren · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1978
Presented here is an efficient facsimile data coding scheme (CSM) which cambines an extended run-length coding technique with a symbol recognition technique. The CSM scheme first partitions the data into run-length regions and symbol regions. The run-length regions are then coded by a modified Interline Coding technique, while the data within the symbol region is further subpartitioned into regions defined as symbols. A prototype symbol library is maintained, and as each new symbol is encountered, it is compared with each element of the library. These comparisons produce a signature for the new symbol. A tolerance threshold is used to evaluate the "goodness" of the comparison. If the tolerance threshold indicates a matching symbol, then only the location and the library address need be transmitted. Otherwise the new symbol is both trans-mitted and placed in the library. For finite sized libraries a scoring system determines which elements of the library are to be replaced by new prototypes. Simulation results are demonstrated for both CCITT and Xerox standard documents.