Digital image processing method suitable for halftone representation based on dither process

摘要

A digital image processing method includes first through fifth steps. The first step is providing a first matrix pattern having a plurality of threshold values stored in a storage memory. The second step is defining a size of each of second matrix patterns based on a predetermined area of the first matrix pattern. The first matrix pattern is composed of the second matrix patterns each of which includes a partial set of the threshold values and has the defined size so that a line density of an output image is determined. The third step is reading two or more threshold values of one of a plurality of basic matrix patterns from the storage memory at specified addresses. Each second matrix pattern is composed of the basic matrix patterns each of which has two or more threshold values and corresponds to one pixel. The fourth step is comparing the digital image data relating to one pixel with the threshold values of the basic matrix pattern to produce a multilevel image signal based on the comparison result. The fifth step is outputting the multilevel image signal relating to one dot, so that each dot is represented by a plurality of tone levels determined by each basic matrix pattern.