IMAGE CODER, IMAGE DECODER, IMAGE PROCESSING UNIT, IMAGE CODING METHOD, IMAGE DECODING METHOD AND IMAGE PROCESSING METHOD

摘要

PROBLEM TO BE SOLVED: To obtain an image with high quality by applying efficient coding even to an image where areas with largely different image characteristics such as a CG and a natural image are intermingled so as to minimize image quality deterioration of an expanded image even when the capacity of a coding data memory is small. SOLUTION: An input image from an image input device 11 is divided into blocks by a raster/block conversion circuit 12 and an image characteristic discrimination circuit 13 calculates an image characteristic for each block to discriminate kinds of an image for each block. Then a changeover circuit 18 based on the discrimination circuit result selects adaptively an ADCT coding circuit 14 of a variable length irreversible coding system, an in-block four-value coding circuit 15 of a fixed length irreversible coding system, an in-block binary coding circuit 16 or a block run length coding circuit 17.