Patent US 5,436,736

Disclosed is a binarization method for binarizing multi-level image data of an object pixel in accordance with binarized data of neighboring pixels of the object pixel which have been binarized. Multi-level image data corresponding to an object pixel are input, then a first portion of the input data is binarized in accordance with a random number, and a second portion of the data is binarized in accordance with the binarized data. The binary data of the first portion and the binary data of the second portion are output as binary data of the object pixel.