Symmetry watermark
First Claim
Patent Images
1. A method of digital watermark embedding in a two dimensional signal, the method comprising:
- generating a digital watermark signal carrying one more auxiliary data symbols to be embedded in the two dimensional signal; and
embedding the digital watermark signal in the two dimensional signal such that the digital watermark has radial symmetry and circumferential symmetry;
wherein the circumferential symmetry enables detection of rotation of the digital watermark, and the radial symmetry enables detection of scaling of the digital watermark.
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Abstract
A digital watermark is generated with radial and circumferential symmetries in a particular domain of a host signal into which it is embedded. These symmetries enable a detector to compute the projective transformation and rotation angle of the embedded signal using only the symmetry properties. The embedded signal may be variable, such as being modulated with a variable message payload, yet the scale and rotation of this variable signal is detectable based on its symmetry properties.
97 Citations
20 Claims
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1. A method of digital watermark embedding in a two dimensional signal, the method comprising:
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generating a digital watermark signal carrying one more auxiliary data symbols to be embedded in the two dimensional signal; and embedding the digital watermark signal in the two dimensional signal such that the digital watermark has radial symmetry and circumferential symmetry;
wherein the circumferential symmetry enables detection of rotation of the digital watermark, and the radial symmetry enables detection of scaling of the digital watermark. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of detecting a symmetric digital watermark embedded in an image, the method comprising:
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computing radial symmetry in an embedding domain of the image to detect a radial symmetry property of the digital watermark; based on the radial symmetry, determining spatial scaling of the digital watermark as a function of rotation angle; computing circumferential symmetry in an embedding domain to detect a circumferential symmetry property of the digital watermark; and based on use of the circumferential symmetry, determining a rotation angle of the digital watermark. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of detecting a symmetric digital watermark embedded in an image, the method comprising:
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transforming the image into an embedding domain; computing radial symmetry of the image as a function of angle to detect signal energy attributable to radial symmetry of the digital watermark; computing circumferential symmetry to detect signal energy attributable to circumferential symmetry of the digital watermark; using the radial and circumferential symmetries to extract a message payload from the digital watermark. - View Dependent Claims (20)
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Specification