To allow the processing unit to apply division of image data to such areas as character, photographic and background areas and to apply compensation to each of the data suitable for each area consistently with high efficiency.

Rectangular areas are detected, unified and the result is added to a rectangular list by retrieving black pixels from an image that has been reduced and binarized from an original image duing preliminary scanning. Pixel data of each rectangular area extracted, based on the coordinates in the rectangular list among pixel data as a result of main scanning area given to an image discrimination circuit 135, in which each image characteristic is discriminated and the pixel data are coded by a low-frequency image high efficiency coding circuit 152 or a high-frequency image high efficiency coding circuit 153, depending on the image characteristic discriminated. Pixel data other than the data in the rectangular areas are coded by a background high efficiency coding circuit 154. After the end of coding processing, data in the rectangular list are compressed and stored in a main body memory 160. When an image is output, the rectangular data are decoded, and the image is expanded based thereon.