Image processing system for compressing image data including binary image data and continuous tone image data by a sub-band transform method with a high-compression rate

摘要

An image processing system which compresses an image including both a binary image and a continuous tone image by a sub-band transform method with a high compression rate. A 2x2 pixel matrix block is extracted from image data. A transform factor having a plurality of frequency components is obtained from the 2x2 pixel matrix block data. The transform factor is quantized by a fixed-length quantizing method by deleting a predetermined number of lower order bits of each of the frequency components.