PURPOSE: To maximize picture compression rate while deterioration in image quality is minimized and to minimize the capacity of a memory in the image processing unit where an input image signal is compressed irreversibly and stored in a memory and outputted with expansion.

CONSTITUTION: A pre-stage image processing section 70 processing received image data R, G, B and generating an image area signal used to identify a character part and a pattern of the received image is provided with a smoothing spatial filter 77 applying smooth processing to image data depending on the image area signal. The image data from the pre-stage image processing section 70 are coded by a coding circuit 81 and processed for irreversible compression and written in an image memory 82 and the image area signal is written in an image area memory 84. Coded image data are read from the image memory 82 synchronously with an external read request and the image area signal is read from the image area memory 84 and the coded image data are decoded by a decoding circuit 89 and restored to original image data.