IMAGE DATA PROCESSOR

PROBLEM TO BE SOLVED: To realize a function for extracting selectively only a desired area from a coding data block subjected to coding compression by the DCT system and stored and decoding the result only with a simple circuit configuration by providing a discrimination means discriminating whether or not a current variable decoding position is within a valid area based on a comparison result between a count and a stored value. SOLUTION: A block counter 10 counts number of blocks of decoded data. A register 11 stores a start block length SB, a register 12 stores an invalid block length UB, and a register 15 stores a valid block line length VLB respectively. A block line counter 14 counts number of block lines BLC. A comparator 16 compares an output signal of a multiplexer 100 with a count of the block counter 10. A comparator 17 compares a count of the block line counter 14 with a storage value VLB of the register 15.