Embedding data in material
First Claim
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1. A method of embedding data in material, the method comprising the steps of:
- producing transform coefficients Ci representing a transform of the material, andcombining the coefficients Ci with data symbols Ri to produce modified coefficients Ci′
where
Ci′
=Ci+α
iRi the method further comprising determining an adaptation strength α
i for each unmodified coefficient Ci as a function F{Cn}i of a predetermined set {Cn}i of transform coefficients Cn which set excludes the coefficient Ci wherein the coefficients are serially ordered and the coefficients Cn are coefficients preceding coefficient Ci.
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Abstract
A method of embedding data in material comprises the steps of:
- embedding data in original material to produce data embedded material;
- removing the watermark from the data embedded material to produce recovered material;
- comparing the original and recovered material to determine the differences and locations of differences therebetween; and
- storing the said locations and corrections which correct the said differences.
A method of removing the data embedded in the material, comprises the steps of:
- removing the data from the material to produce recovered material;
- deriving the said corrections and locations from the said store; and
- using the corrections to correct the recovered material at the said locations.
A method of embedding data in material, preferably comprises the steps of:
- producing transform coefficients Ci representing a spatial frequency transform of the material, and
- combining the coefficients Ci with the data bits Ri to produce a modified coefficient Ci′ where
Ci′=Ci+αiRi - the method further comprising determining αi for each unmodified coefficient Ci as a function F{Cn}i of a predetermined set {Cn}i of transform coefficients Cn which set excludes the coefficient Ci.
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Citations
42 Claims
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1. A method of embedding data in material, the method comprising the steps of:
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producing transform coefficients Ci representing a transform of the material, and combining the coefficients Ci with data symbols Ri to produce modified coefficients Ci′
where
Ci′
=Ci+α
iRithe method further comprising determining an adaptation strength α
i for each unmodified coefficient Ci as a function F{Cn}i of a predetermined set {Cn}i of transform coefficients Cn which set excludes the coefficient Ci wherein the coefficients are serially ordered and the coefficients Cn are coefficients preceding coefficient Ci. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. An apparatus for embedding data in material, comprising
a transformer for producing transform coefficients Ci representing a transform of the material, and a combiner for combining the coefficients Ci with data symbols Ri to produce modified coefficients Ci′ - where
Ci′
=Ci+α
iRi,the apparatus further comprising a calculator for calculating an adaptation strength α
i for each unmodified coefficient Ci as a function F{Cn}i of a predetermined set {Cn}i of transform coefficients Cn which set excludes the coefficient Ci, wherein the coefficients are serially ordered and the coefficients Cn are coefficients preceding coefficient Ci. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
- where
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33. An apparatus for removing data embedded in material, the apparatus comprising:
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a processor for determining the values of the symbols Ri; a calculator for calculating, for each modified coefficient Ci′
, the value of the said function F{Cn}i of the corresponding set {Cn}i of coefficients Cn to determine α
i; anda subtractor which, for each modified coefficient Ci′
, subtracts therefrom α
i.Ri to restore the unmodified coefficient value Ci, which thereby becomes available for use as an unmodified coefficient of another set {Cn}i of unmodified coefficients Cn for restoring another coefficient Ci′
, wherein the coefficients are serially ordered and the said set {Cn}i consists of coefficients preceding coefficient Ci. - View Dependent Claims (34, 35, 36, 37)
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38. A method of removing data embedded in material, the method comprising:
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determining the values of the data symbols Ri; calculating, for each modified coefficient Ci′
, the value of the said function;
F{Cn}i of the corresponding set {Cn}i of coefficients Cn to determine α
i; andfor each modified coefficient Ci′
, subtracting therefrom α
i.Ri to restore the unmodified coefficient value Ci, wherein the coefficients are serially ordered and the said set {Cn}i consists of modified coefficients preceding coefficient Ci. - View Dependent Claims (39, 40, 41, 42)
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Specification