METHOD FOR EXTRACTING DISCRIMINATION INFORMATION EMBEDDED IN PRINTED MATTER AND PRINTED MATTER HAVING DISCRIMINATION INFORMATION EMBEDDED

摘要

PROBLEM TO BE SOLVED: To provide an extracting method for discrimination information embedded in printed matter and the printed matter having the discrimination information embedded. SOLUTION: An enlarged image is generated by enlarging a binary image, obtained by binarizing image data of a source image, twice longitudinally and laterally and all the arrays obtained by dividing the enlarged image into 2×2 pixel units are varied according to a prescribed array substitution rule to generate two kinds of array substitution images. The property that pixels having a value 1 and a value 0 are different in arrangement between the two kinds of array substitution images is used to embed 1-bit discrimination information in respective array substitution images, and image data of array substitution images having the discrimination information embedded are outputted to obtain printed matter. When the discrimination information is extracted, a Fourier spectrum is extracted from the image data of the array substitution image read out of the printed matter and the property that the Fourier spectra of the two kinds of array substitution images are different in the deflection is used to extract the discrimination information.