Patent ID: 7345791

Claim:
An image processing device for processing an input image so as to reproduce a halftone, comprising: a matrix setting section for setting a threshold matrix having a plurality of elements arranged in M columns×N rows, at least two threshold values being stored in each of the elements; an element specifying section for specifying an element of the threshold matrix that corresponds to a position of a pixel in the input image; and a multilevel signal generating section for fetching the threshold values from the specified element and for generating a multilevel signal by transforming an input pixel value of the pixel to one of multiple levels in accordance with the fetched threshold values; wherein the multilevel signal generating section: (i) outputs a constant value Doutmin as the multilevel signal when a first condition, that the input pixel value is smaller than or not larger than a minimum value of the threshold values, is satisfied; (ii) outputs a constant value Doutmax as the multilevel signal when a second condition, that the input pixel value is larger than or not smaller than a maximum value of the threshold values, is satisfied; and (iii) outputs an interpolation value that is between the two constant values Doutmin and Doutmax as the multilevel signal by carrying out a predetermined operation when both the first condition and the second condition are not satisfied.