Patent ID: 7509060

Claim:
An image forming apparatus configured to form a copy-forgery-inhibited pattern image, which includes a latent image and a background image, on a sheet, the image forming apparatus comprising: a formation unit configured to form a plurality of latent image patches, which are generated by using a plurality of density signal values, and a plurality of background image patches, which are generated by using a plurality of density signal values, on at least one sheet; a luminance information obtaining unit configured to obtain luminance information presenting luminance values of the plurality of latent image patches and the plurality of background image patches in image data obtained by reading the sheet on which the plurality of latent image patches and the plurality of background image patches are formed; and a determination unit configured to determine a density signal value that is used to generate a latent image, and a density signal value that is used to generate a background image, according to the luminance information obtained by the luminance information obtaining unit, wherein the determination unit determines a density signal value that is used to generate a latent image, and a density signal value that is used to generate a background image, by selecting one of the plurality of latent image patches, which has luminance information representing a luminance value closest to a predetermined value, and one of the plurality of background image patches, which has luminance information representing a luminance value closest to the predetermined value, according to the luminance information representing luminance values of the plurality of latent image patches and the plurality of background image patches obtained by the luminance information obtaining unit.