Method for inserting, in the fourier domain, a digital watermark in an image and corresponding method for detecting a digital watermark in an image to be analyzed
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G06K-009/00
G06T-001/00
H04N-001/32
출원번호
US-0378502
(2013-02-12)
등록번호
US-9401002
(2016-07-26)
우선권정보
FR-12 51325 (2012-02-13)
국제출원번호
PCT/EP2013/052787
(2013-02-12)
국제공개번호
WO2013/120850
(2013-08-22)
발명자
/ 주소
Autrusseau, Florent
출원인 / 주소
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE—CNRS
대리인 / 주소
Brush, David D.
인용정보
피인용 횟수 :
0인용 특허 :
1
초록▼
A method is provided for inserting a digital watermark in an image by an insertion device. Inserting includes: applying a Fourier transform to the image, delivering a 2D Fourier spectrum; inserting the watermark in the Fourier spectrum delivering a modified Fourier spectrum; and applying an inverse
A method is provided for inserting a digital watermark in an image by an insertion device. Inserting includes: applying a Fourier transform to the image, delivering a 2D Fourier spectrum; inserting the watermark in the Fourier spectrum delivering a modified Fourier spectrum; and applying an inverse Fourier transform to the modified Fourier spectrum delivering a watermarked image. The watermark includes a set of watermarking coefficients each associated with a distinct determined position of a given quadrant among the quadrants of the Fourier domain, the spectral coordinates u and v of which, measured along the two axes of coordinates of the given quadrant and starting from the continuous component and expressed in percentage of the dimensions U and V of the given quadrant, are such that: u66%×U and v66%×V. The set of positions associated with the watermarking coefficients defines a convex pattern in the given quadrant.
대표청구항▼
1. A method comprising: inserting a digital watermark in an image by means of an insertion device, wherein inserting comprises:applying a Fourier transform to said image, to obtain a two dimensional Fourier spectrum defined by Fourier coefficients at different positions of a Fourier domain comprisin
1. A method comprising: inserting a digital watermark in an image by means of an insertion device, wherein inserting comprises:applying a Fourier transform to said image, to obtain a two dimensional Fourier spectrum defined by Fourier coefficients at different positions of a Fourier domain comprising four quadrants, each possessing two axes of coordinates extending from the continuous component;inserting said watermark in said Fourier spectrum by modification of Fourier coefficients of said Fourier spectrum, as a function of watermarking coefficients comprised in the watermark, to obtain a modified Fourier spectrum; andapplying an inverse Fourier transform to said modified Fourier spectrum to obtain a watermarked image; wherein said watermark comprises a set of watermarking coefficients each associated with a distinct determined position of a given quadrant among said quadrants of the Fourier domain, the spectral coordinates u and v of which, measured along the two axes of coordinates of the given quadrant and starting from the continuous component and expressed in percentage of the dimensions U and V of the given quadrant, are such that: u>66%×U and v>66%×V,and wherein the set of positions associated with said watermarking coefficients defines a convex pattern determined in the given quadrant. 2. The method according to claim 1, wherein said convex pattern is a square or a rectangle. 3. The method according to claim 2, wherein said convex pattern is a square with 2n×2n positions, n being an integer greater than two. 4. The method according to claim 3, wherein: 3≦n≦6. 5. The method according to claim 1, wherein said watermark is inserted in complying with the central symmetry of the Fourier spectrum: for each Fourier coefficient that is situated in the given quadrant and undergoes a modification as a function of the given watermark, a Fourier coefficient that is situated in the quadrant symmetrical to the given quadrant, relative to the center of the Fourier domain, also undergoes a modification as a function of said given watermarking coefficient. 6. The method according to claim 1, wherein said convex pattern is centered on a diagonal of the given quadrant, oriented by 45° relative to the two axes of coordinates serving to define the spectral coordinates u and v of a position in the given quadrant. 7. The method according to claim 1, wherein the watermark is inserted according to the following insertion equation: yu,v=xu,v+α×xu,v×wu,v, where: yu,v is a modified Fourier coefficient, at the position in the given quadrant of the Fourier domain;xu,v is an original Fourier coefficient at the position in the given quadrant of the Fourier domain;α is a weighting coefficient for the watermarking strength; andwu,v is a watermarking coefficient taking the value +1 or −1. 8. The method according to claim 1, wherein the watermark is inserted according to the following insertion equation: yu,v=α×xu,v×wu,v, where: yu,v is a modified Fourier coefficient at the position in the given quadrant of the Fourier domain;xu,v is an original Fourier coefficient at the position in the given quadrant of the Fourier domain;α is a weighting coefficient of the watermarking strength; andwu,v is a weighting coefficient taking the value +1 or −1. 9. The method according to claim 1, wherein the watermark is inserted according to the following insertion equation: yu,v=wu,v, where: yu,v is a modified Fourier coefficient at the position in the given quadrant of the Fourier domain;wu,v is a watermarking coefficient comprised in a predetermined range. 10. The method according to claim 9, wherein the minimum and maximum values of said predetermined range are a function of the values of the real parts of the Fourier coefficients each undergoing a modification as a function of said watermarking coefficients. 11. The method according to claim 1, wherein the watermark is inserted by modifying only the real part of each Fourier coefficient undergoing a modification as a function of said watermarking coefficients. 12. A method comprising: detecting a digital watermark in an image to be analyzed, by means of a detection device, wherein detecting comprises:applying a Fourier transform to the image to be analyzed to obtain a two dimensional Fourier spectrum, defined by the Fourier coefficients at different positions of a Fourier domain comprising four quadrants each possessing two axes of coordinates extending from the continuous component;measuring similarities between two Fourier spectrum portions: a reference portion and a portion to be analyzed, extracted from said Fourier spectrum of the image to be analyzed;taking a decision on presence or absence of a watermark in said portion to be analyzed as a function of the result of measuring similarities;wherein the detection device has at its disposal:a reference watermark comprising a set of watermarking coefficients each associated with a distinct determined position of one given quadrant among said quadrants of the Fourier domain, of which the spectral coordinates u and v, measured along both axes of coordinates of the given quadrant and starting from the continuous component, and expressed in percentage of the dimensions U and V of the given quadrant are such that: u>66%×U and v>66%×V, andthe set of the positions associated with the watermarking coefficients, which define a determined convex pattern in the given quadrant of the Fourier domain,and wherein measuring similarities comprises:determining said reference portion, as a function of the watermarking coefficients of said reference watermark;determining said portion to be analyzed, comprising obtaining the Fourier coefficients situated, in the given quadrant, at the positions associated with the watermarking coefficients of said reference watermark;computing a two dimensional normalized cross-correlation between the reference portion and the portion to be analyzed, giving a two dimensional correlation map;and wherein a decision on presence is taken if at least one value of the two dimensional correlation map is above a given threshold. 13. The method according to claim 12, wherein determining said reference portion comprises taking, for a given position in the given quadrant of the Fourier domain, the watermarking coefficient associated with said given position in said reference watermark. 14. The method according to claim 12, wherein determining said reference portion comprises taking, for a given position in the given quadrant of the Fourier domain, the result of a weighting: of the watermarking coefficient associated with said given position,by a reference Fourier coefficient situated, in the given quadrant of the Fourier domain, at said given position, said reference Fourier coefficient belonging to a two dimensional Fourier spectrum resulting from a Fourier transform of an original image, the detection device having available said reference Fourier coefficient. 15. The method according to claim 12, wherein computing a two dimensional normalized cross-correlation is done according to the following equation: f★g=(F{tilde over (()}v)G(v)) where: f is the reference portion;g is the portion to be analyzed; represents the inverse Fourier transform;F{tilde over (()}v) is the complex conjugate of the Fourier transform of f; andG(v) is the Fourier transform of g. 16. The method according to claim 12, wherein said convex pattern is a square or a rectangle. 17. The method according to claim 16, wherein said convex pattern is a square with 2n×2n positions, n being an integer greater than two. 18. The method according to claim 17, wherein: 3≦n≦6. 19. The method according to claim 12, wherein said convex pattern is centered on a diagonal of the given quadrant of the Fourier domain, oriented by 45° relative to the axes of coordinates serving to define the spectral coordinates u and v of a position in the given quadrant of the Fourier domain. 20. A computer-readable non-transitory medium storing a computer program comprising a set of instructions executable by a computer to implement a method for inserting when said program is executed on a computer, wherein the method comprises: inserting a digital watermark in an image by an insertion device, wherein inserting comprises:applying a Fourier transform to said image, to obtain a two dimensional Fourier spectrum defined by Fourier coefficients at different positions of a Fourier domain comprising four quadrants, each possessing two axes of coordinates extending from the continuous component;inserting said watermark in said Fourier spectrum by modification of Fourier coefficients of said Fourier spectrum, as a function of watermarking coefficients comprised in the watermark, to obtain a modified Fourier spectrum; andapplying an inverse Fourier transform to said modified Fourier spectrum to obtain a watermarked image; wherein said watermark comprises a set of watermarking coefficients each associated with a distinct determined position of a given quadrant among said quadrants of the Fourier domain, the spectral coordinates u and v of which, measured along the two axes of coordinates of the given quadrant and starting from the continuous component and expressed in percentage of the dimensions U and V of the given quadrant, are such that: u>66%×U and v>66%×V,and wherein the set of positions associated with said watermarking coefficients defines a convex pattern determined in the given quadrant. 21. A computer-readable non-transitory medium storing a computer program comprising a set of instructions executable by a computer to implement a method for detecting when said program is executed on a computer, wherein the method comprises: detecting a digital watermark in an image to be analyzed, by a detection device, the method comprising: applying a Fourier transform to the image to be analyzed to obtain a two dimensional Fourier spectrum, defined by the Fourier coefficients at different positions of a Fourier domain comprising four quadrants each possessing two axes of coordinates extending from the continuous component;measuring similarities between two Fourier spectrum portions: a reference portion and a portion to be analyzed, extracted from said Fourier spectrum of the image to be analyzed;taking a decision on presence or absence of a watermark in said portion to be analyzed as a function of the result of measuring similarities;wherein the detection device has at its disposal: a reference watermark comprising a set of watermarking coefficients each associated with a distinct determined position of one given quadrant among said quadrants of the Fourier domain, of which the spectral coordinates u and v, measured along both axes of coordinates of the given quadrant and starting from the continuous component, and expressed in percentage of the dimensions U and V of the given quadrant are such that: u>66%×U and v>66%×V, andthe set of the positions associated with the watermarking coefficients, which define a determined convex pattern in the given quadrant of the Fourier domain,and wherein measuring similarities comprises: determining said reference portion, as a function of the watermarking coefficients of said reference watermark;determining said portion to be analyzed, comprising obtaining the Fourier coefficients situated, in the given quadrant, at the positions associated with the watermarking coefficients of said reference watermark;computing a two dimensional normalized cross-correlation between the reference portion and the portion to be analyzed, giving a two dimensional correlation map;and wherein a decision on presence is taken if at least one value of the two dimensional correlation map is above a given threshold. 22. A device for inserting a digital watermark in an image, the device comprising: means for applying a Fourier transform to said image; to obtain a 2D Fourier spectrum, defined by Fourier coefficients at different positions of a Fourier domain comprising four quadrants each possessing two axes of coordinates extending from the continuous component;means for inserting said watermark in said Fourier spectrum by modification of Fourier coefficients of said Fourier spectrum, as a function of watermarking coefficients comprised in the watermark, to obtain a modified Fourier spectrum;means for applying an inverse Fourier transform to said modified Fourier spectrum making it possible to obtain a watermarked image;wherein said watermark comprises a set of watermarking coefficients each associated with a distinct determined position of a given quadrant among said quadrants of the Fourier domain, the spectral coordinates u and v of which, measured along the two axes of coordinates of the given quadrant and starting from the continuous component and expressed in percentage of the dimensions U and V of the given quadrant, are such that: u>66%×U and v>66%×V,and wherein the set of positions associated with said watermarking coefficients defines a determined convex pattern in the given quadrant. 23. A device for detecting a digital watermark in an image to be analyzed, the device comprising: means for applying a Fourier transform to the image to be analyzed to obtain a two dimensional Fourier spectrum, defined by the Fourier coefficients at different positions of a Fourier domain comprising four quadrants each possessing two axes of coordinates extending from the continuous component;means for measuring similarities between two Fourier spectrum portions: a reference portion and a portion to be analyzed, extracted from said Fourier spectrum of the image to be analyzed;means for taking a decision on presence or absence of a watermark in said portion to be analyzed as a function of the result of measuring similarities;wherein the device for detecting has at its disposal:a reference watermark comprising a set of watermarking coefficients each associated with a distinct determined position of one given quadrant among said quadrants of the Fourier domain, of which the spectral coordinates u and v, measured along both axes of coordinates of the given quadrant and starting from the continuous component, and expressed in percentage of the dimensions U and V of the given quadrant are such that: u>66%×U and v>66%×V; andthe set of the positions associated with the watermarking coefficients, which define a determined convex pattern in the given quadrant of the Fourier domain,wherein the means for measuring similarities comprise:means for determining said reference portion as a function of the watermarking coefficients of said reference watermark;means for determining said portion to be analyzed, to obtain the Fourier coefficients situated, in the given quadrant, at the positions associated with the watermarking coefficients of said reference watermark;means for computing a two dimensional normalized cross-correlation between the reference portion and the portion to be analyzed, giving a two dimensional correlation map;and wherein the means for taking a decision are adapted to taking a decision on presence if at least one value of the two dimensional correlation map is above a given threshold.
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이 특허에 인용된 특허 (1)
Rhoads, Geoffrey B.; Sharma, Ravi K., Image processing using embedded registration data to determine and compensate for geometric transformation.
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