Patent ID: 6972873

Claim:
A halftoning method of converting a multilevel input image into a binary image, comprising: converting the multilevel value of a given noteworthy pixel of the multilevel input image into a binary value while pixels of the multilevel input image are scanned successively; diffusing a possible error, which has occurred in binary value with respect to the noteworthy pixel, to unscanned pixels adjacent to the noteworthy pixel by one diffusion technique; changing the technique of said diffusing to another in accordance with a predetermined manner as the scanning of the successive pixels of the multilevel input image progresses; discriminating whether or not the noteworthy pixel is a pixel constituting part of a profile of the multilevel input image; and detecting the direction in which the profile of the multilevel input image extends with respect to the noteworthy pixel, wherein if the result of said discriminating is positive, said changing comprises changing the error diffusion technique from one to another, and values according to the occurred error are added to the values of the unscanned pixels along the detected direction of the profile as an exceptional process.