Patent ID: 8102567

Claim:
An image forming apparatus comprising: a coordinate transformation unit configured to transform a recording pixel coordinate of a pixel of interest in a pixel space into an address coordinate of the pixel of interest in a dither space; a representative point calculation unit configured to calculate a representative point of threshold information in the dither space nearest to the address coordinate of the pixel of interest in the dither space obtained by said coordinate transformation unit; a deviation amount calculation unit configured to calculate a deviation amount between the address coordinate in the dither space corresponding to a pixel coordinate of an integer in said pixel space and the representative point in said dither space by obtaining the pixel coordinate of the integer in the pixel space nearest to said representative point from the representative point in the dither space obtained by said representative point calculation unit; a correction value determination unit configured to determine whether or not to make a correction by adding the deviation amount calculated by said deviation amount calculation unit to the address coordinate of the pixel of interest in said dither space; an address correction unit configured to make the correction by adding the deviation amount calculated by said deviation amount calculation unit to the address coordinate of the pixel of interest in said dither space, if the addition is determined to be made by said correction value determination unit; and a threshold value processing unit configured to compare a dither threshold value represented by threshold information in the dither space corresponding to the coordinate obtained by rounding the address coordinate of the pixel of interest in the dither space obtained by addition in said address correction unit and a pixel value of the pixel of interest in said pixel space.