Pattern encoding and decoding method and encoder and decoder using the

Abstract

Pattern encoding is carried out by 1) substituting an index data of a registered pattern for a position data in a library with respect to an index data peculiar to each of the extracted patterns, 2) taking a difference between an off-set position data of the extracted pattern and an off-set position data of the registered pattern whereby an off-set position difference data is provided, and 3) encoding the position data and the off-set position difference data and providing an encoded data. A pattern extracting unit obtains the extracted patterns from image data. An accumulating/checking unit accumulates the extracted patterns as accumulated patterns, assigns indexes specific to the accumulated patterns, and checks each extracted pattern by comparison with the accumulated patterns. When an accumulated pattern is found to match the extracted pattern, the accumulating/checking unit provides a position data within a library instead of the index data, and also provides the off-set position difference data. When no pattern is found to match the accumulated pattern libraries, the accumulating/checking unit provides the off-set position data and bit map data of the extracted pattern to the encoding unit. The arrangement enables the reduction in codes in pattern encoding, thus improving the code transmission efficiency.