A method and apparatus for modifying a digitized image in which the digitized image is received as input pixel values for a plurality of pixels, first selects an unprocessed one of the pixels to be a current pixel. The current pixel is modified by adding a total error value and a screen frequency component...http://www.google.de/patents/US5446561?utm_source=gb-gplus-sharePatent US5446561 - Method and apparatus for digital scale halftoning with variable screen structure for electrophotographic printing devices
