Method for embedding electronic watermark, decoding method, and devices for the same
First Claim
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1. A method of embedding a digital watermark in a master image, said embedding method comprising the steps of:
- extracting blocks of a predetermined size from said master image;
processing image data corresponding to each block by orthogonal transform;
comparing orthogonal transformed coefficients between at least two blocks having a predetermined relationship with each other and making the coefficients satisfy a preset order of magnitude according to bit information specified as the digital watermark;
quantizing the coefficients obtained by the orthogonal transform with a quantization table and using the quantized coefficients to embed the bit information, wherein embedding the bit information is carried out when, are not all equal to zero; and
processing each block with the embedded bit information by inverse orthogonal transform, so as to output a resulting image with the digital watermark embedded therein;
introducing a logic function that is true when a difference between the orthogonal transformed coefficients of the at least two blocks having the predetermined relationship is in a preset range; and
modifying a procedure adopted to embed the bit information, based on the true and false state of the logic function.
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Abstract
The method extracts a plurality of blocks from a master image, processes image data corresponding to each block by orthogonal transform, compares coefficients of adjoining blocks with each other, and modifies the order of magnitude of the coefficients, based on bit information to be embedded. The bit information to be embedded is constructed as a basic pattern, which is generated, for example, by the density pattern method. The basic pattern is embedded in image data iteratively. The process of iteratively embedding the basic pattern enhances the resistance against various attacks.
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Citations
16 Claims
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1. A method of embedding a digital watermark in a master image, said embedding method comprising the steps of:
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extracting blocks of a predetermined size from said master image; processing image data corresponding to each block by orthogonal transform; comparing orthogonal transformed coefficients between at least two blocks having a predetermined relationship with each other and making the coefficients satisfy a preset order of magnitude according to bit information specified as the digital watermark; quantizing the coefficients obtained by the orthogonal transform with a quantization table and using the quantized coefficients to embed the bit information, wherein embedding the bit information is carried out when, are not all equal to zero; and processing each block with the embedded bit information by inverse orthogonal transform, so as to output a resulting image with the digital watermark embedded therein; introducing a logic function that is true when a difference between the orthogonal transformed coefficients of the at least two blocks having the predetermined relationship is in a preset range; and modifying a procedure adopted to embed the bit information, based on the true and false state of the logic function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for embedding a digital watermark in a master image, said digital watermark embedding apparatus comprising:
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block extraction means that extracts blocks of a predetermined size from said master image; transformation means that processes image data corresponding to each block by orthogonal transform; bit information embedding means that compares orthogonal transformed coefficients between at least two blocks having a predetermined relationship with each other and makes the coefficients satisfy a preset order of magnitude according to bit information specified as the digital watermark; coefficient quantizing means that quantize the coefficients obtained by the orthogonal transform with a quantization table and use the quantized coefficients to embed the bit information, wherein embedding the bit information is carried out when the quantized coefficients of the at least two blocks are not all equal to zero; output means that processes each block with the embedded bit information by inverse orthogonal transform, so as to output a resulting image with the digital watermark embedded therein; logic function introduction means that introduces a logic function that is true when a difference between the orthogonal transformed coefficients of the at least two blocks having the predetermined relationship is in a preset range; and procedure modification means that modifies a procedure adopted to embed the bit information, based on the true and false state of the logic function. - View Dependent Claims (14)
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15. A computer storage device in which a program for embedding a digital watermark in a master image is recorded in a computer readable manner, said program causing a computer to attain the functions of:
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extracting blocks of a predetermined size from said master image; processing image data corresponding to each block by orthogonal transform; comparing orthogonal transformed coefficients between at least two blocks having a predetermined relationship with each other and making the coefficients satisfy a preset order of magnitude according to bit information specified as the digital watermark; quantizing the coefficients obtained by the orthogonal transform with a quantization table and using the quantized coefficients to embed the bit information, wherein embedding the bit information is carried out when the quantized coefficients of the at least two blocks are not all equal to zero; processing each block with the embedded bit information by inverse orthogonal transform, so as to output a resulting image with the digital watermark embedded therein introducing a logic function that is true when a difference between the orthogonal transformed coefficients of the at least two blocks having the predetermined relationship is in a preset range; and modifying a procedure adopted to embed the bit information, based on the true and false state of the logic function. - View Dependent Claims (16)
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Specification