Patent ID: 7620255

Claim:
An image processor for converting input image data that has multi-grayscale image data for each pixel with a predetermined resolution into binary data for each of said pixels, comprising: a binary unit, wherein if a grayscale value of multi-grayscale image data of a processing target pixel is lower than a reference value, which is less than ½ of a maximum grayscale value of said multi-grayscale image data, said binary unit performs a first binary processing for converting the input image data of said processing target pixel into binary data of “dot present” or “dot absent” based on a threshold matrix, in which a plurality of threshold values are dispersed without concentrating a plurality of low threshold values, and if the grayscale value of the multi-grayscale image data of the processing target pixel is higher than said reference value, said binary unit performs a second binary processing for converting the input image data of said processing target pixel into binary data of “dot present”, and an error diffusion processing for adding an error between the grayscale value of said processing target pixel and the maximum grayscale value to said multi-grayscale image data of peripheral pixels based on a first error diffusion matrix.