Patent ID: 8253968

Claim:
An image forming apparatus which forms an image based on image data, and based on an unmasked area where an output of an image is permitted inside and restricted outside, by using an image processing section having an image carrier, an exposure unit which scans and exposes the image carrier, and a developing unit which visualizes, on a printing medium, an electrostatic latent image formed on the image carrier by scanning exposure of the exposure unit, comprising: storage means for storing error amount information representing an error amount of a scanning line of exposure light from an ideal scanning line in an exposure scanning direction on the image carrier; first modification means for modifying the image data on the basis of the error amount information stored in said storage means; second modification means for enlarging the unmasked area so as to include an area of an image of the image data after modification by the first modification means, on the basis of the error amount information stored in said storage means, which is used for modifying the image data; and outputting means for outputting the image data having been modified by the first modification means, based on the enlarged unmasked area by the second modification means.