Compression and expansion methods and apparatus

摘要

A compression and encoding system for bi-level image data determines the available memory capacity of a receiving device, then compresses and encodes the image data with successively increasing compression ratios until encoded data not exceeding the memory capacity of the receiving device are obtained. Preferably, the image is divided into rectangular blocks, and successive bit planes are generated on the basis of the number of dark picture elements in each block, and on the basis of adjacency relationships among like-valued picture elements in each block. Feedback may be employed to adjust the darkness of certain compressed blocks according to the darkness of the preceding block.