Patent ID: 7952767
Filing Date: 2011-05-31
Classification: H04N

Abstract:
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.