Image forming apparatus and image correction method for correcting scan-line position error

摘要

A scan line profile characteristic representing the distortion of a scan line is detected. Dot image data undergoes the screen process using a dither matrix. At this time, the quantization process is done by shifting a dither matrix element in the sub-scanning direction opposite to the direction of the scan line changing process at a scan line changing point in the scan line changing process in accordance with the profile characteristic. The image data after the screen process undergoes the scan line changing process, and the interpolation process smooths the scan line changing point.