Digital watermark-embedding apparatus and method, digital watermark-detecting apparatus and method, and recording medium
First Claim
Patent Images
1. A digital watermark-embedding apparatus comprising:
- an embedment signal-generating unit operable to generate an embedment signal in accordance with embedment information, the embedment signal being embedded as a digital watermark;
a block-dividing unit operable to divide a digital image signal into blocks that are formed by several pixels;
an orthogonal transform unit operable to practice orthogonal transformation of each of the blocks, thereby transforming the blocks into several frequency components;
a digital watermark-embedding unit operable to operate, under a predetermined rule, a value of at least one of the several frequency components in accordance with the embedment signal generated by said embedment signal-generating unit, in which the value is operated in such a manner that amounts of variations in image within the blocks follow a predetermined specific pattern in consideration of detection;
a first characteristic amount-extracting unit operable to extract a first characteristic amount in accordance with the several frequency components; and
a selecting unit operable to select a value of at least one of the several frequency components in accordance with the extracted first characteristic amount;
wherein the specific pattern has two different regions arranged in alternating sequence, one of the two different regions being where the amounts of variations in image serve as positive, and the other region being where the amounts of variations in image serve as negative; and
wherein the first characteristic amount is a combination of one or more frequency components selected from a total of specific frequency components corresponding to vertical edges in an image within the blocks, a total of specific frequency components corresponding to horizontal edges therein, and a total of specific frequency components corresponding to slanted edges therein.
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Abstract
A digital image signal is divided into blocks. Each of the divided blocks is subjected to orthogonal transformation. As a result, the divided blocks are transformed into several frequency components. One or more frequency components are selected in accordance with a characteristic amount that is extracted from the several frequency components. Values of the selected frequency components are operated under a predetermined rule in accordance with an embedment signal that is generated from embedment information.
53 Citations
20 Claims
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1. A digital watermark-embedding apparatus comprising:
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an embedment signal-generating unit operable to generate an embedment signal in accordance with embedment information, the embedment signal being embedded as a digital watermark; a block-dividing unit operable to divide a digital image signal into blocks that are formed by several pixels; an orthogonal transform unit operable to practice orthogonal transformation of each of the blocks, thereby transforming the blocks into several frequency components; a digital watermark-embedding unit operable to operate, under a predetermined rule, a value of at least one of the several frequency components in accordance with the embedment signal generated by said embedment signal-generating unit, in which the value is operated in such a manner that amounts of variations in image within the blocks follow a predetermined specific pattern in consideration of detection; a first characteristic amount-extracting unit operable to extract a first characteristic amount in accordance with the several frequency components; and a selecting unit operable to select a value of at least one of the several frequency components in accordance with the extracted first characteristic amount; wherein the specific pattern has two different regions arranged in alternating sequence, one of the two different regions being where the amounts of variations in image serve as positive, and the other region being where the amounts of variations in image serve as negative; and wherein the first characteristic amount is a combination of one or more frequency components selected from a total of specific frequency components corresponding to vertical edges in an image within the blocks, a total of specific frequency components corresponding to horizontal edges therein, and a total of specific frequency components corresponding to slanted edges therein. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A digital watermark-embedding method comprising:
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generating an embedment signal in accordance with embedment information, the embedment signal being embedded as a digital watermark; dividing a digital image signal into blocks that are formed by several pixels; practicing orthogonal transformation of each of the blocks, thereby transforming the blocks into several frequency components; operating, under a predetermined rule, a value of at least one of the several frequency components in accordance with the embedment signal obtained by the generating the embedment signal, in which the value is operated in such a manner that amounts of variations in image within the blocks follow a predetermined specific pattern in consideration of detection; and extracting a first characteristic amount in accordance with the several frequency components; and selecting at least one of the several frequency components in accordance with the extracted first characteristic amount; wherein the specific pattern has two different regions arranged in alternating sequence, one of the two different regions being where the amounts of variations in image serve as positive, and the other region being where the amounts of variations in image serve as negative; and wherein the first characteristic amount is a combination of one or more frequency components selected from a total of specific frequency components corresponding to vertical edges in an image within the blocks, a total of specific frequency components corresponding to horizontal edges therein, and a total of specific frequency components corresponding to slanted edges therein. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification