Image analysis – Pattern recognition – Template matching
Patent
1997-01-21
1998-08-04
Rogers, Scott
Image analysis
Pattern recognition
Template matching
382237, 358456, 380 54, 283113, 283 94, G06K 974, H04N 1405, H04N 152
Patent
active
057907030
ABSTRACT:
A method for generating watermarks in a digitally reproducible document which are substantially invisible when viewed including the steps of: (1) producing a first screen pattern suitable for reproducing a gray image on a document; (2) deriving at least one conjugate screen description that is related to said first pattern; (3) producing an image containing the first screen; (4) producing a second image containing the first and the second screens in combination, whereby upon placing the first and second images in a superposed relationship autocorrelation between the first pattern on each document occurs everywhere within the documents where the first screen is used, and conjugate correlation occurs where the first and second screens occur and the image placed therein using the conjugate screens becomes detectable (e.g., visible) due to the high contrast between the autocorrelated and conjugately correlated regions. As a result of the use of the first and second screens in an alternating fashion within a document, the images created therefrom are self-referencing, meaning that the superposition of the images in an offset manner maximizes the contrast of the watermark.
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Basch Duane C.
Rogers Scott
Xerox Corporation
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