Image processing method, image printing method, image printing mechanism and printed matter

摘要

A multi-gradation image such as a face image of a person in which sub-information is to be embedded is subjected to a preprocess by a preprocessing section (17) based on a relationship between certain image data and read image data of a printed matter on which the certain image data is printed, sub-information is embedded into the multi-gradation image subjected to the preprocess by the preprocessing section (17) by use of an electronic watermark embedding section (18) in an invisible state to the human eye, and the multi-gradation image having the sub-information embedded therein by the electronic watermark embedding section (18) is subjected to a post-process corresponding to the preprocess performed by the preprocessing section (17) by use of a post-processing section (19).