Abstract: The invention relates to a method for processing an image signal such that areas of original image data are sequentially scanned with a scanning window having a size corresponding to M picture elements in units of a predetermined number of picture elements so as to perform halftone display in accordance with black-and-white binary distribution with respect to the signal levels of the picture elements within the scanning window every time the scanning window is moved. The picture elements within the scanning window are assigned an order of preference in accordance with their image signal levels. A sum of the image signal levels of the picture elements within the scanning window is calculated, and A and N of the equations S=C.times.N+A are calculated, where C is a predetermined image signal level (e.g., black level and maximum level), N is an integer, and A is the image signal level falling within the range O.ltoreq.A<C.