Patent ID: 8743423
Filing Date: 2014-06-03
Classification: H04N

Abstract:
1. An image forming apparatus for depicting an M-level gradation image formed of a plurality of pixels having pixel numbers of M gradations (M is a natural number equal to or greater than three) through a plurality of halftones, comprising: a threshold value generating unit for generating a threshold value matrix of N gradations (N is a natural number equal to or greater than two); and a comparison unit for comparing each of the pixels numbers of the pixels of the M-level gradation image with each of corresponding threshold values of the threshold value matrix so that the comparison unit converts the M-level gradation image to an N-level gradation image formed of a plurality of pixels having pixel numbers of the N gradations, wherein said threshold value generating unit is configured to determine an arrangement of standard dots, said threshold value generating unit is configured to divide all of the pixels to the halftones with an arrangement point of each of the standard dots as a center, said threshold value generating unit is configured to determine an order of the gradations of the pixels contained in each of the halftones thus divided, said threshold value generating unit is configured to determine an order of the standard dots so that the arrangement of the standard dots determined upon completing ordering of a half of a total number of the standard dots is concentrated in a specific cycle determined by the arrangement of the standard dots from the arrangement points of the standard dots as the center of the halftones, said threshold value generating unit is configured to determine a priority order of the gradations between the halftones, said threshold value generating unit is configured to determine an order of the threshold values of the gradations of all of the pixels from “1” to “N−1” according to the order of the gradations of the pixels contained in each of the halftones and the priority order of the gradations between the halftones so that the threshold value generating unit generates the threshold value matrix having the threshold values from “1” to “N−1”.