Patent ID: 8625156

Claim:
An image forming apparatus which includes, for respective printing materials of a plurality of colors, a plurality of color image forming sections each for forming a visible image by exposure scanning and development on an image carrier, and forms a color image by superimposing visible images formed on a print medium by the plurality of color image forming sections, each of the plurality of color image forming sections comprising: an exposure shift amount storage unit configured to store shift amount information representing a shift amount between an ideal scanning line and an actual scanning line in an exposure scanning direction on the image carrier; an image data storage unit configured to store image data to be formed; address conversion unit configured to convert a readout address in the image data storage unit, based on the shift amount information stored in the exposure shift amount storage unit, and read out image data in accordance with the converted address; a tone correction unit configured to perform, based on the address, tone correction for the image data read out by the address conversion unit; a multi-level error diffusion unit configured to perform quantization by multi-level error diffusion processing for the image data having undergone the tone correction by the tone correction unit; and an exposure control signal generation unit configured to generate an exposure control signal to perform exposure scanning of the image data, based on a quantization level of the quantization by the multi-level error diffusion unit, wherein the multi-level error diffusion unit switches the number of quantization levels based on the shift amount information stored in the exposure shift amount storage unit.