METHOD FOR COHERENT WATERMARK INSERTION AND DETECTION IN COLOR HALFTONE IMAGES
First Claim
1. A method for generating a color image carrying an embedded watermark image, the color image including a plurality of separations, wherein a watermark image inserted into the color image is not readily visually perceptible, comprising:
- a. providing a single halftoning process for the plurality of separations, wherein the halftoning process includes a periodic tile, each tile offset from its neighbors by a fixed displacement, and where said periodic tile includes a first region and a second region and a first part of the first region is substantially identical to a corresponding part of the second region, and a second part of the first region is substantially conjugate to a corresponding part of the second region;
b. halftoning image data from the color image using the single halftoning process wherein a set of pixel locations associated with a first threshold value are filled by a first of the plurality of separations;
c. halftoning the image data using the single halftoning process wherein a second set of pixel locations associated with second of the plurality of separations, the second set of pixel locations are filled successively to the first set of pixel locations, such that when a first copy of the color image is spatially offset from a second copy of the color image by an integral multiple of the fixed displacement, at least the first part of the first region aligns with a second part of the second region and a second part of the first region aligns with a first part of the second region and contrast of the identical and conjugate first and second parts become visible to reveal the watermark image.
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Accused Products
Abstract
A method for generating an authenticable color image, the color image including a plurality of color separations, wherein an authentication image inserted in the multicolor image is not readily visually perceptible, includes halftoning image data corresponding to a first color separation using a single halftone screen, wherein the halftone screen includes means for generating an authentication image in a color image; and halftoning image data corresponding to a second color separation using the halftone screen and dot placement information for the image data corresponding to the first color separation to form a multicolor image; wherein halftoning of image data corresponding to the second color separation includes placing dots for the second color separation in thresholds of the halftone screen relative to those thresholds occupied by the first color separation in the halftone screen in accordance with a predetermined relationship.
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Citations
17 Claims
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1. A method for generating a color image carrying an embedded watermark image, the color image including a plurality of separations, wherein a watermark image inserted into the color image is not readily visually perceptible, comprising:
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a. providing a single halftoning process for the plurality of separations, wherein the halftoning process includes a periodic tile, each tile offset from its neighbors by a fixed displacement, and where said periodic tile includes a first region and a second region and a first part of the first region is substantially identical to a corresponding part of the second region, and a second part of the first region is substantially conjugate to a corresponding part of the second region; b. halftoning image data from the color image using the single halftoning process wherein a set of pixel locations associated with a first threshold value are filled by a first of the plurality of separations; c. halftoning the image data using the single halftoning process wherein a second set of pixel locations associated with second of the plurality of separations, the second set of pixel locations are filled successively to the first set of pixel locations, such that when a first copy of the color image is spatially offset from a second copy of the color image by an integral multiple of the fixed displacement, at least the first part of the first region aligns with a second part of the second region and a second part of the first region aligns with a first part of the second region and contrast of the identical and conjugate first and second parts become visible to reveal the watermark image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for generating an authenticable color image, the color image containing a plurality of separations, wherein an authenticable image inserted into the color image is not readily visible, comprising:
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a circuit to receive color image data for the image to be authenticated; a halftoning circuit coupled to the receiving circuit that halftones the color image data, generating a binary color image therefrom; a tiling circuit coupled to the halftoning circuit that adds a tile to the halftoning circuit, the tile being periodically and regularly repeated throughout the halftoned image; and a control circuit coupled to the receiving circuit and the halftoning circuit that controls the successive halftoning of each of the plurality of separations, wherein each successive separation fills pixels successive to the previously halftoned separation. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification