Patent US 5,282,256

An image data coding method for a case where image data are transmitted or filed upon being binary coded includes steps of replacing a predetermined pixel by a predicted value predicted by a plurality of pixels peripheral to the predetermined pixel, in conformance with a coded image data compression technique, and performing binary coding while dispersing an error, which is generated by the replacement, among peripheral pixels. Also provided are a variety of image data coding apparatus for practicing this image data coding method. The invention makes it possible to perform binary coding and compression of half-tone image data very efficiently.