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System and method for the generation of multiple angle correlation-based digital watermarks

  • US 7,894,626 B2
  • Filed: 08/31/2007
  • Issued: 02/22/2011
  • Est. Priority Date: 08/31/2007
  • Status: Expired due to Fees
First Claim
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1. A method creating digital watermarks in grayscale images, comprising:

  • receiving the first image to be watermarked;

    determining the first watermark to be embedded in the first image;

    embedding the first watermark into the first image by halftoning the first image using a three-dimensional threshold array having a phase shift value as an input and a first halftone structure defined by the spatial vectors Va1(xa1, ya1) and Vb1(xb1, yb1);

    outputting a first watermarked grayscale image containing the first digital watermark embedded with the first halftone structure;

    receiving the second image to be watermarked;

    determining the second watermark to be embedded in the second image;

    embedding the second watermark into the second image by halftoning the second image with a three-dimensional threshold array having a phase shift value as an input and a second halftone structure defined by the spatial vectors Va2(xa2, ya2) and Vb2(xb2, yb2), wherein the interior angle between the two vectors Va1(xa1, ya1) and Vb1(xb1, yb1) of the first halftone structure is equal to the interior angle between the two vectors Va2(xa2, ya2) and Vb2(xb2, yb2) of the second halftone structure, the vector amplitude |Va1(xa1, ya1)| of the first vector of the first halftone structure is equal to the vector amplitude |Va2(xa2, ya2)| of the first vector of the second halftone structure, and the vector amplitude |Vb1(xb1, yb1)| of the second vector of the first halftone structure is equal to the vector amplitude |Vb2(xa2, yb2)| of the second vector of the second halftone structure; and

    outputting a second watermarked grayscale image containing the second watermark embedded with the second halftone structure.

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