To provide a more sophisticated copy guard function by using information unique to an original as a mark attached to the original in order to permit or inhibit copying of the original so as to discriminate the legitimacy of the mark included in a read image of the original thereby accurately discriminating the permission or inhibition of copying.

Because copy guard information unique to the original is attached to a printed matter, that is, the original obtained by image forming processing in an image forming apparatus such as a printer, for example, the guard function compares and discriminates whether the unique information calculated from image data of the original read by a scanner or a copying machine or the like is coincident or dissident with the unique information included in the copy guard information attached to the original.

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