Patent ID: 7145702

Claim:
An image processing method comprising: converting image data of M-gradations in a pixel into multivalued image data of N-gradations (M>N>2) in a pixel; setting a gradation value at which a practical dot size diameter is equivalent to a theoretical square pixel dimension, as a predetermined gradation TJ (N>TJ>2) which causes a tone jump; determining whether a gradation of a remarked pixel converted into the multivalued image data is the predetermined gradation TJ; determining, when the gradation of the remarked pixel converted into the multivalued image data is determined to be the predetermined gradation TJ, whether a pixel of the predetermined gradation TJ exists in pixels located adjacent to the remarked pixel; changing the gradation of the remarked pixel to a gradation other than the predetermined gradation so as to avert the tone jump when the pixel of the predetermined gradation TJ exists in the pixels located adjacent to the remarked pixel; and storing an average density after multivalued image data conversion.