Patent ID: 7924465

Claim:
A dither matrix used in halftone processing for converting input image data having M input halftone levels into output image data having N (M>N>2) output halftone levels, wherein multiple submatrices are arranged in the dither matrix at a screen angle without overlap and without leaving space in the dither matrix so that output pixels form a halftone dot pattern or screen lines; concentration type submatrices are used as the submatrices when an input halftone level is within a range of input halftone levels corresponding to an output halftone level that is lower than a predetermined threshold level T (N>T>1); and dispersion type submatrices are used as the submatrices when the input halftone level is within a range of input halftone levels corresponding to an output halftone level that is equal to or higher than the predetermined threshold level T; and wherein, when the input halftone level is a highest input halftone level in a range of input halftone levels corresponding to a highest output halftone level (T−1) of the concentration type submatrices, the output halftone level (T−1) is used throughout the concentration type submatrices.