Method of extracting digital watermark information and method of judging bit value of digital watermark information
First Claim
1. A digital watermark information extracting method in which digital watermark information is extracted from image data which has the digital watermark information embedded therein by altering at least one pixel data located at a predetermined position on a specific coordinate and is geometrically deformed. comprising:
- an embedding position check step of performing the processing of extracting at least one pixel data at a predetermined position on the specific coordinate from the image data, obtaining difference between a data value of the pixel data thus extracted and a reference value, and outputting a bit value of the pixel data thus extracted which is judged from the difference and reliability of the bit value thus judged to judge whether the information is embedded in the pixel data while applying the geometrical deformation on the image data until it is confirmed that the reliability is higher than a predetermined value.
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Abstract
A digital watermark information is extracted from geometrically deformed image without using a calibrating digital watermark. Pixel data at positions predetermined in an X-Y coordinate used when embedding the watermark is extracted from image data in which the digital watermark has been embedded for given pixel data and compared with a reference value to determine whether the watermark has been embedded in the pixel data concerned or not. This processing is repeated until it is confirmed that the information is embedded in the pixel data concerned, while applying geometric deformation to the image data.
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Citations
11 Claims
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1. A digital watermark information extracting method in which digital watermark information is extracted from image data which has the digital watermark information embedded therein by altering at least one pixel data located at a predetermined position on a specific coordinate and is geometrically deformed. comprising:
an embedding position check step of performing the processing of extracting at least one pixel data at a predetermined position on the specific coordinate from the image data, obtaining difference between a data value of the pixel data thus extracted and a reference value, and outputting a bit value of the pixel data thus extracted which is judged from the difference and reliability of the bit value thus judged to judge whether the information is embedded in the pixel data while applying the geometrical deformation on the image data until it is confirmed that the reliability is higher than a predetermined value. - View Dependent Claims (2, 3, 4)
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5. A digital watermark information extracting method in which digital watermark information is extracted from image data which has the digital watermark information embedded therein by altering at least one pixel data located at a predetermined position on a specific coordinate and is geometrically deformed, comprising:
an embedding position check step of performing the processing of extracting at least one pixel data at a predetermined position on the specific coordinate from the image data, obtaining difference between a data value of the pixel data thus extracted and a reference value, and outputting a bit value of the pixel data thus extracted which is judged from the difference and reliability of the bit value thus judged to judge whether the in-formation is embedded in the pixel data while altering the predetermined position on the image data by applying an deformation on the specific coordinate until it is confirmed that the reliability is higher than a predetermined value. - View Dependent Claims (6, 7, 8, 9)
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10. A bit value judgment method of digital watermark information in which each of bit data items constituting the digital watermark information is embedded in image data by applying an alteration on at least one pixel data located at a predetermined position on a specific coordinate, said method executing as to each of at least two bit data items among the bit data items constituting the digital watermark information;
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a bit value judgment step for obtaining difference between a data value of pixel data in which the bit data item concerned is to be embedded and a reference value, and judging a bit value of the bit data item concerned from the difference;
a reliability calculation step for calculating reliability of the bit value thus judged from the difference; and
a reliability output step for outputting the bit value at the pixel data thus judged and the reliability of the bit value thus calculated.
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11. A bit value judgment method as claimed 10, wherein said reliability calculation step calculates the reliability of the bit value of the bit data item, on the basis of a probability distribution curve which is defined by distribution of difference between the data value of the pixel data in which the bit data item concerned is to be embedded and the reference value.
Specification