Patent ID: 8422079

Claim:
An image forming apparatus which has an image forming unit for forming an image, comprising: a storage configured to store profile information representing a profile of a scan line on an image carrier of the image forming unit, wherein the profile information contains at least one pair of a pixel position in the scan line direction and a shift amount of pixels following the pixel position in the scan line in a sub-scanning direction, and wherein the profile of the scan line is due to positional errors of the image forming unit; an error diffusion processing unit configured to perform an error diffusion process for image data; and a registration error correction unit configured to correct the image data by shifting by one pixel, for each pixel data in the sub-scanning direction, a position of each pixel data in the image data quantized by said error diffusion processing unit, on the basis of the profile information so as to offset the shift amount of the scan line in the sub-scanning direction on the image carrier of the image forming unit, wherein said error diffusion processing unit diffuses an error on the basis of the profile information, at distributions different between a predetermined second area including a position where the image data is shifted in the sub-scanning direction by said registration error correction unit, and a first area separate from the second area, wherein the second area and the first area are in the image data.