CN1269342C - Method and device for uniting digital water print based on singular value analysis and spread spectrum technique - Google Patents

Method and device for uniting digital water print based on singular value analysis and spread spectrum technique Download PDF

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CN1269342C
CN1269342C CN 03125461 CN03125461A CN1269342C CN 1269342 C CN1269342 C CN 1269342C CN 03125461 CN03125461 CN 03125461 CN 03125461 A CN03125461 A CN 03125461A CN 1269342 C CN1269342 C CN 1269342C
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watermark
singular value
image
value decomposition
spread spectrum
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CN1529282A (en
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周祖德
刘泉
李方敏
姜雪梅
梁小宇
钟毅
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Wuhan University of Technology WUT
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Abstract

The present invention relates to a method and a device for digital watermark unification based on singular value decomposition and the spread spectrum technology. The method comprises the two parts of digital watermark embedding and digital watermark extraction; the first part of encoding for digital watermark embedding comprises the steps: the singular value decomposition of the original image, the spread spectrum of watermark information, watermark embedding, the singular value decomposition of the image after the watermark embedding, and the formation of an image with watermarks; the second part of decoding for digital watermark extraction comprises the steps: the singular value decomposition of the image with watermarks, watermark extraction, the singular value decomposition of the image after the watermark extraction, and the recovery of the original image. Compared with old digital watermark methods, the present invention is obviously improved in the aspects of the confidentiality and the robustness of watermarks. The comprehensive technologies of singular value decomposition, the spread spectrum technology, etc. are used in the present invention; consequently, not only is the information content of watermarks increased, but also watermark images have strong robustness; as a result, the purpose of copyright protection is reached.

Description

Method and device based on the unified digital watermarking of singular value decomposition and spread spectrum
Technical field
The invention belongs to information security, image processing and area of pattern recognition; the utilization computer software; in digital picture, embed data; reach the purpose of copyright protection; be method and the device of a kind of unified digital watermarking (Digital Watermarking based onSingular Value Decomposition (SVD) and Spread Spectrum Technology) specifically based on singular value decomposition and spread spectrum; be that copyright information is at first expanded by the spread spectrum mode, be embedded into then in the singular value decomposition territory of original image.
Background technology
Along with the fast development of computer network, it is very outstanding that information security issue seems.Information Hiding Techniques is used in many applications as a kind of emerging information security technology.At present, also receive the concern of research institution and business circles just day by day, its major impetus is from the needs of people to copyright protection.Along with the digitlization of phonotape and videotape, image and other electronic products, the piracy of digital product is more prone to, and this has caused the very big concern of music, film, books and software publisher, has therefore caused the research in the important branch field " digital watermarking " of Information hiding.Digital watermark technology need provide a potential effective means as the copyright protection of electronic data etc., thereby has caused the extensive concern of international academic community and business circles, is the popular direction in a forward position of present international academic community research.Digital watermarking was used for copyright protection and checks whether data are destroyed by permanent being embedded in the multi-medium data.Digital watermark technology is as the new technique of protection copyright under open network environment; it can establish the copyright owner; identification buyer or other additional informations about digital content are provided; and these information are embedded in digital picture, digital audio and the video sequence with the sightless form of human eye, be used to confirm ownership and copyright tracking behavior.
At present, water mark method mainly is divided into two big classes: spatial domain water mark method and frequency domain water mark method.Most of spatial domain water mark methods can provide simple and direct efficient watermark to embed scheme, and have bigger information embedded quantity, but it lacks the robustness to image processing.Early stage spatial domain water mark method is least significant bit (Least Significant Bits is called for short LSB) method and improves one's methods.People such as L.F Turner and R.G.van Schynde successively utilize this method that specific markers is hidden in digital audio and the digital picture.Because this method is to hide Info by adjusting minimum several of initial data, makes the general user visually be difficult to discover for hiding Info.Though it has bigger information embedded quantity, as digital watermark method, because of its basic principle restriction, the digital watermark information of being hidden is very fragile, can't stand the signal processing that some diminish.
The frequency domain water mark method is subjected to numerous scholars' favor because of its strong antinoise signal processing that has and the ability of malicious attack.Part then is the most promising research direction in the digital watermark in conjunction with the image adaptive water mark method of both characteristics.Most of frequency domain water mark method has all adopted spread spectrum communication (Spread spectrum communication) technology.People such as Tirkel notice that at first spread spectrum technic can be applied to digital watermark method, have occurred a large amount of digital watermark methods based on the spread spectrum communication principle subsequently, and are wherein the most representative with the spread-spectrum watermark method of people such as Cox proposition.The spread-spectrum watermark method that people such as Cox propose proposes, and at first image is done discrete cosine transform (DCT), on preceding k the coefficient of amplitude maximum (not comprising DC component), is generally the low frequency component of image in the DCT territory that then watermark is added to.Decoding functions then calculates the discrete cosine transform of original image and watermarking images respectively, and extracts the watermark that embeds, and remakes correlation detection whether the existing with definite watermark of extracting watermark and original watermark.Even this method still can extract a reliable watermarked copies through some general geometric deformations and signal processing operations when watermarking images after producing apparent in view distortion.A simple modifications to the Cox method is watermark not to be embedded on the low frequency component in DCT territory, but is embedded on the intermediate frequency component with the robustness of adjusting watermark and the contradiction between the invisibility.A significant contribution of spread-spectrum watermark method is to propose the part that watermark is embedded into the image information perceptual important, reaches the purpose that improves the watermark robustness.
Singular value decomposition is the most useful of numerical linear algebra and one of the most effective instrument, and it is widely used in statistical analysis, signal and image processing, Systems Theory and control.Liu Ruizhen etc. have proposed a kind of digital image watermarking method based on singular value decomposition, its general thought is similar to the method for Cox, method replaces overall dct transform with the singular value decomposition of image, in the SVD territory with the pseudo random number embedded images of Gaussian Profile, the main theory of using SVD is according to being: 1) the image singular value is stable very good, and promptly the singular value of image does not have big variation when image is applied in little disturbance; 2) accumulate characteristic but not visual characteristic in the image that singular value showed.
Relevant technical literature has following five pieces:
[1] Yang Ming, Liu Xianzhong. " matrix theory ", publishing house of the Central China University of Science and Technology, 2003.10
[2] Liu Ruizhen, Tan Tieniu. based on the digital image watermarking method of singular value decomposition. electronic letters, vol, 2001.2.
[3]I.J.Cox，J.Killian，F.T.Leighton，etc.，Secure?spreadspectrum?watermarking?for?multimedia，IEEE?Transaction?on?ImageProcessing，1997，6(12)：1673-1687.
[4]Kwok，S.H.，Yang，C.C.，Tam，K.Y.“Watermark?design?patternfor?intellectual?property?protection?in?electronic?commerceapplications”，Proceedings?of?the?Hawaii?InternationalConference?on?System?Sciences?Jan?4-Jan?7?2000?IEEE?p?151.
[5]R.G.Van?Schndel，A.Z.Tirkel，C.F.Osborne.A?digitalwatermark.Proc.of?ICIP’94，1994，2：86-90.
[6]C.T.Hsuand，J.L.Wu.Hidden?digital?watermarks?in?images.IEEE?Trans.On?Image?Processing，1999，8(1)：58-68.
[7]G.C.Langelaar，R.L.Lagendijk，J.Biemond.Removing?spatialspread?spectrum?watermarks?by?non-linear?filtering.Proc?ofEUSIPCO’98.1998，2281-2284。
Summary of the invention
The objective of the invention is to disclose a kind of method and device that in digital picture, embeds and extract copyright information based on the unified digital watermarking of singular value decomposition and spread spectrum; with the method original image being carried out watermark embeds; the band watermarking images that obtains is compared with original image; its image size is constant; naked eyes can not be differentiated the difference of embed digital watermark front and back image; thereby under the requirement that guarantees invisibility and robustness, reached the purpose of multi-medium data copyright protection.
To achieve these goals, method of the present invention comprises embed digital watermark and extracts digital watermarking two parts:
First is the coding of embed digital watermark, comprising: the singular value decomposition of original image, the spread spectrum of watermark information, watermark embed, the singular value decomposition of watermarked back image, form the image of band watermark at last;
Second portion comprises for extracting the decoding of digital watermarking: the singular value decomposition of image after the singular value decomposition of band watermarking images, watermark extracting, the extraction watermark, recover original image at last,
Wherein: first---the coding of embed digital watermark, a step below comprising:
First step: N * N gray level image is made singular value decomposition, obtain two orthogonal matrix U, V and a diagonal matrix S, singular value decomposition SVD method is exactly that watermark information is embedded in the singular value decomposition of original image, and purpose is to improve the robustness of digital picture;
Second step: various forms of watermarks are unified to handle.The present invention is positioned in the meaningful watermark, and mainly considers character type and icons type watermark.In the present invention, constructed a set of signals (signal can change, reduce or expand with purposes) with 64 signals, each signal has 32bits.Each signal is 32 matched filter corresponding to a dimension, wherein " 0 " and " 1,, in matched filter, be converted into respectively-a and a.Hamming distance between any two signals is all greater than 16.The relevant of the signal extracted and all matched filters then calculated in decoding.Determine that the matched filter with maximal correlation output is the signal after deciphering.When producing set of signals, encoding mechanism has produced binary string at random, and wherein the appearance of " 0 " and " 1 " clothes people Bernoulli distributes.Therefore, although watermark is a significant character string, the signal of final embedded images has kept feature at random;
Third step: watermark information is carried out spread spectrum according to the spread spectrum communication theory.In general, the information that is used as watermark belongs to narrow band signal for the camouflage carrier (being image) in broadband, and by cryptochannel (image) transmission information (watermark) before, the spread spectrum technology can make information and frequency band coupling.Because it is highly beneficial to the invisibility of watermark information that the high frequency region watermark embeds, but to robustness effect extreme difference, and low frequency range watermark embedding is favourable to robustness, but unavailable because visual effect can't receive.The spread spectrum technology can be alleviated these contradiction by a low-yield signal is embedded into each frequency band.The present invention adopts the direct sequence spread spectrum method that watermark is added in the singular value decomposition territory repeatedly.Dimension and image self-capacity situation according to the sequence that obtains after the watermark processing can obtain the number of times that watermark sequence can repeat to load;
The 4th step: watermark embeds, the frequency expansion sequence W of watermark k, k=1,2 ..., be embedded on the diagonal matrix S in the scramble mode, obtain a new matrix S w
The 5th step: to S wCarry out singular value decomposition, obtain U w, S wAnd V w, wherein: S w=U wS wV w T, compute matrix A then w=US wV TJust can obtain the image after watermarked;
Second portion the steps include: for extracting the decoding of digital watermarking
1 . [ U ′ , S ′ , V ′ ] = SVD ( A w * ) ;
2 . D = U w S ′ V w T ;
3.W *＝(D-S)/β；
4 . d j = 1 C r Σ i p i | W i * | + β C r Σ i | W i * | p i 2 ;
5.If d j＞thd，d j＝1，
If d j＜thd，d j＝0，
Wherein: U, V are orthogonal matrix;
S is a diagonal matrix;
S wBe diagonal matrix;
D is for calculating median;
A w *: be image information;
W *Be watermark information;
β is the intensity that watermark embeds;
C rBe the sheet rate;
p iBe spread spectrum code sequence;
Thd is a threshold value.
The present invention also provides a kind of device of the unified digital watermarking based on singular value decomposition and spread spectrum, the inventive system comprises the embed digital watermark device and extract code translator two parts of digital watermarking: the code device of embed digital watermark, the singular value decomposition device, the spread spectrum device of watermark information, watermark flush mounting, the watermarked singular value decomposition device of image afterwards that comprise original image, form the image of band watermark at last, wherein:
The singular value decomposition device of original image: be that N * N gray level image is made singular value decomposition, obtain two orthogonal matrix U, V and a diagonal matrix S, the SVD method is exactly that watermark information is embedded in the singular value decomposition of original image, and purpose is to improve the robustness of digital picture;
The spread spectrum device of watermark information: be that various forms of watermarks are unified to handle.The present invention is positioned in the meaningful watermark, and mainly considers character type and icons type watermark.In the present invention, constructed a set of signals (signal can change, reduce or expand with purposes) with 64 signals, each signal has 32bits.Each signal is 32 matched filter corresponding to a dimension, and wherein " 0 " and " 1 " is converted in matched filter respectively-a and a.Hamming distance between any two signals is all greater than 16.The relevant of the signal extracted and all matched filters then calculated in decoding.Determine that the matched filter with maximal correlation output is the signal after deciphering.When producing set of signals, encoding mechanism has produced binary string at random, and wherein the Bernoulli distribution is obeyed in the appearance of " 0 " and " 1 ".Therefore, although watermark is a significant character string, the signal of final embedded images has kept feature at random.According to the spread spectrum communication theory watermark information is carried out spread spectrum.In general, the information that is used as watermark belongs to narrow band signal for the camouflage carrier (being image) in broadband, and by cryptochannel (image) transmission information (watermark) before, the spread spectrum technology can make information and frequency band coupling.Because it is highly beneficial to the invisibility of watermark information that the high frequency region watermark embeds, but to robustness effect extreme difference, and low frequency range watermark embedding is favourable to robustness, but unavailable because visual effect can't receive.The spread spectrum technology can be alleviated these contradiction by a low-yield signal is embedded into each frequency band.The present invention adopts the direct sequence spread spectrum method that watermark is added in the singular value decomposition territory repeatedly.Dimension and image self-capacity situation according to the sequence that obtains after the watermark processing can obtain the number of times that watermark sequence can repeat to load.
Watermark flush mounting: the frequency expansion sequence W of watermark k, k=1,2 ..., be embedded on the diagonal matrix S in the scramble mode, obtain a new matrix S w
The singular value decomposition device of watermarked back image: be to S wCarry out singular value decomposition, obtain U w, S wAnd V w, wherein: S w=U wS wV w T, compute matrix A then w=US wV TJust can obtain the image after watermarked.
The present invention extracts the code translator of digital watermarking, comprises the singular value decomposition device of image after the singular value decomposition device of being with watermarking images, watermark extraction apparatus, the extraction watermark, recovers original image at last;
Extract the code translator of digital watermarking and finish decoding by following step:
1 . [ U ′ , S ′ , V ′ ] = SVD ( A w * ) ;
2 . D = U w S ′ V w T ;
3.W *＝(D-S)/β；
4 . d j = 1 C r Σ i p i | W i * | + β C r Σ i | W i * | p i 2 ;
5.If d j＞thd，d j＝1，
If d j＜thd，d j＝0，
Wherein: U, V are orthogonal matrix;
S is a diagonal matrix;
S wBe diagonal matrix;
D is for calculating median;
A w *Be image information;
W *Be watermark information;
β is the intensity that watermark embeds;
C rBe the sheet rate;
p iBe spread spectrum code sequence;
Thd is a threshold value.
The present invention proposes unified digital watermark method and device based on singular value decomposition and spread spectrum.Compare with digital watermark method in the past, this technology all increases significantly on the confidentiality of watermark and robustness.Because the present invention adopts complex arts such as singular value decomposition and spread spectrum, has both improved the amount of information of watermark, make watermarking images have very strong robustness again simultaneously, thereby reach the purpose of copyright protection.This is an innovation part of the present invention.One of its key technology is that various forms of watermarks are unified to handle, and its objective is to make this technology can be applicable to various forms of meaningful digital watermarkings.Two of key technology is watermark spread spectrums: before watermark embeds watermark information is carried out spread spectrum, can improve the capacity of watermark signal like this.Three of key technology is singular value decomposition of digital picture: before watermark embeds original image is carried out singular value decomposition, can improve the robustness of image like this.So, can guarantee the invisibility of digital picture with the digital watermarking of the inventive method making, and processing all has good robustness to common image, mainly shows low-pass filtering, medium filtering, Wiener filtering, image cutting, image rotation and diminish the JPEG compression to handle.A large amount of test datas shows that this technology is unusual robust.In addition, method proposed by the invention can adapt to the embedding of various forms of meaningful digital watermarkings.
Description of drawings
Fig. 1 is a flow chart of the present invention.
Fig. 2 is the image of the watermarked front and back of the inventive method.
(a) image of original picture (b) watermark image (c) after watermarked
Fig. 3 is the robustness check of the inventive method under low-pass filtering.
(a) watermark image of the extraction of the band watermark image (b) after low-pass filtering
BER＝0.0049，N c＝0.9879
Fig. 4 is the robustness check of the inventive method under the medium filtering.
(a) watermark image of the extraction of the band watermark image (b) behind medium filtering
BER＝0，N c＝1
Fig. 5 is the robustness check of the inventive method under the Wiener filtering.
(a) watermark image of the extraction of the band watermark image (b) after Wiener filtering
BER＝0，N c＝1
Fig. 6 is with the robustness check of the inventive method to visual cutting.
(a) watermark image of the extraction of the band watermark image (b) after the cutting
BER＝0.0039，N c＝0.9903
The robustness check of Fig. 7 for image being turned clockwise with the inventive method.
(a) the image watermark image that 20 ° band watermark image (b) extracts that turns clockwise
BER＝0.0009756，N c＝0.9976
The robustness check of Fig. 8 for image being rotated counterclockwise with the inventive method.
(a) image is rotated counterclockwise the watermark image of 20 ° band watermark image (b) extraction
BER＝0.0009756，N c＝0.9976
Fig. 9 is with the robustness check of the inventive method to visual change of scale.
(a) image is carried out the watermark image that the band watermark image (b) behind the change of scale extracts
BER＝0.0273，N c＝0.9324
Figure 10 is for diminishing the robustness check of JPEG compression to image with the inventive method.
(a) diminish band watermark image behind the JPEG, compression ratio is the watermark image that 60% (b) extracts
BER＝0.0039，N c＝0.9903
Figure 11 is for diminishing the robustness check of JPEG compression to image with the inventive method.
(a) diminish band watermark image behind the JPEG, compression ratio is the watermark image that 35% (b) extracts
BER＝0.0127，N c＝0.9686
Figure 12 is the BER value and the Nc value of the inventive method under different JPEG compression ratios.
(a) BER VS.JPEG compression ratio (b) N cThe VS.JPEG compression ratio
Figure 13 is the functional-block diagram of embed digital watermark device of the present invention.
Figure 14 extracts the functional-block diagram of digital watermarking device for the present invention.
Embodiment
The present invention is described in further detail below in conjunction with drawings and Examples, but this embodiment should not be construed as limitation of the present invention.
Singular value decomposition:
Singular value decomposition in the numerical analysis (SVD) is a kind of numerical method with diagonalization of matrix.The main theory of using SVD in Digital Image Processing is according to being: 1) the image singular value is stable very good, and promptly the singular value of image does not have big variation when image is applied in little disturbance; 2) accumulate characteristic but not visual characteristic in the image that singular value showed.
From the angle of linear algebra, a secondary gray level image can be seen as a nonnegative matrix.If a sub-picture is represented with A, be defined as A ∈ R N * N, wherein R represents real number field, then the singular value decomposition of matrix A is defined as follows:
A＝USV T
Wherein U and V are orthogonal matrix, i.e. UU T=I ∈ R N * N, VV T=I ∈ R N * N, and ‖ U ‖=‖ V ‖=1, S is a diagonal matrix, diagonal element λ iSatisfy λ 1〉=λ 2〉=Λ 〉=λ n〉=0, subscript T representing matrix transposition.
Spread spectrum:
So-called spread spectrum communication, it is a kind of information transmission mode, the frequency bandwidth that its signal occupied is much larger than the essential minimum bandwidth of transmitted breath.Then carrying out correlation demodulation with identical spreading code at receiving terminal separates to extend to and recovers transmitted breath data.Because expanding to very wide frequency band with the information that transmits, spread spectrum system gets on, its power density reduces with the broadening of frequency spectrum, even signal can be submerged in the noise, therefore its confidentiality is very strong, it is very difficult intercepting and capturing or eavesdrop, scout such signal, detect unless adopt, otherwise be helpless spread-spectrum signal with used spreading code and the synchronous with it laggard line correlation of transmitting terminal.Adopt spread spectrum among the present invention, watermark is added in the singular value decomposition territory repeatedly.Dimension and image self-capacity situation according to the sequence that obtains after the watermark processing can obtain the number of times that watermark sequence can repeat to load.
Unified watermark processing:
The watermark of former studies mostly is pseudo random sequence, automatically produces a random sequence in method it is embedded, and can only judge whether this pseudo random sequence exists during check.And many times need watermark can directly indicate the owner or the information such as publisher, publication date of copyright in the ecommerce.This method needs that obviously can not adapt to the copyright protection of Modern Electronic commercial affairs far away.Therefore, the embedding grammar of studying meaningful watermark signal more is of practical significance.Meaningful watermark not only various informative (can be character string, icon), and can carry copyright information (as author, publishing house, unit, date etc.).
Water mark method in the past also has minority to relate to meaningful watermark, but all can only handle the watermark of a certain form, can't adapt to requirement of actual application.Therefore, a kind of embedding grammar that can adapt to the various forms watermark has been proposed in the present invention.Concrete processing method to watermark is as follows:
1), each character is become the sequence of one 32 dimension with glossary of symbols for character string.This glossary of symbols is by the test gained, the binary system random sequence of a 32bits of each sign map, and promptly each symbol is 32 matched filter corresponding to a dimension, any two intersymbol Hamming distances are all greater than 16;
2) if watermark is an icon, earlier icon transformation is become character string, press aforesaid operations again and handle.
The present invention now explains embedding and the extraction that realizes watermark with SVD and spread spectrum method.In the experiment, the carrier image that the present invention adopts is shown in Fig. 2 (a), and size is 256 grades of gray scale image Lena of 512 * 512.Watermark copyright signal is shown in Fig. 2 (b), and size is 50 * 20.Here provided a large amount of robustness test results, had seven aspects: low-pass filtering, medium filtering, Wiener filtering, image cutting, image rotation, change of scale and diminish JPEG compression.
At different disturbed conditions, extract the error rate that hides Info for relatively, we provide the definition of Several Parameters.
1) normalized coefficient correlation (NC)
N c = Σ i Σ j m ( i , j ) m ~ ( i , j ) Σ i Σ j [ m ( i , j ) ] 2 - - - ( 1 )
Here, m represents original copyright information,
Figure C0312546100182
The copyright information that expression is extracted.
2) error rate (BER)
BER = Σ i Σ j ( m ( i , j ) - m ~ ( i , j ) ) Σ i Σ j [ m ( i , j ) ] - - - ( 2 )
3) Y-PSNR (PSNR)
PSNR = 10 log 10 255 2 MSE ( dB ) - - - ( 3 )
Adopt the inventive method to obtain being embedded with the image of watermark shown in Fig. 2 (c).Fig. 2 (c) is carried out low-pass filtering, medium filtering and Wiener Filtering Processing respectively, the watermark signal of extraction such as Fig. 3 (b), Fig. 4 (b), Fig. 5 (b), obviously the result is gratifying.Fig. 6 (a) is the band watermark image after cutting is handled, Fig. 6 (b) is for extracting the result of watermark, Fig. 7 (a) and Fig. 8 (a) turn clockwise 20 ° to the image that is embedded with watermark, are rotated counterclockwise 20 ° then, and Fig. 7 (b) and Fig. 8 (b) are respectively the result who extracts watermark.Fig. 9 (a) at first carries out down-sampling to the image that is embedded with watermark, obtains 256 * 256 images, and adopting bilinear interpolation to return to size then is 512 * 512 image, and Fig. 9 (b) is for extracting the result of watermark.Be to diminish the experimental result that the JPEG compression is handled at last, as Figure 10, Figure 11 and Figure 12.
The operation principle of each device of the present invention is consistent with method of the present invention.

Claims (4)

1, a kind of method of the unified digital watermarking based on singular value decomposition and spread spectrum comprises embed digital watermark and extracts digital watermarking two parts:
First is the coding of embed digital watermark, comprising: the singular value decomposition of original image, the spread spectrum of watermark information, watermark embed, the singular value decomposition of watermarked back image, form the image of band watermark at last;
Second portion comprises for extracting the decoding of digital watermarking: the singular value decomposition of image after the singular value decomposition of band watermarking images, watermark extracting, the extraction watermark, recover original image at last,
Wherein: first---the coding of embed digital watermark, a step below comprising:
First step: N * N gray level image is made singular value decomposition, obtain two orthogonal matrix U, V and a diagonal matrix S, singular value decomposition SVD method is exactly that watermark information is embedded in the singular value decomposition of original image;
Second step: various forms of watermarks are unified to handle;
Third step: watermark information is carried out spread spectrum according to the spread spectrum communication theory;
The 4th step: watermark embeds, the frequency expansion sequence W of watermark k, k=1,2 ..., be embedded on the diagonal matrix S in the scramble mode, obtain a new matrix S w
The 5th step: to S wCarry out singular value decomposition, obtain U w, S wAnd V w, wherein: S w = U w S w V w T , Compute matrix A then w=US wV TJust can obtain the image after watermarked.
2, the method for the unified digital watermarking based on singular value decomposition and spread spectrum as claimed in claim 1, second portion the steps include: for extracting the decoding of digital watermarking
1 . - - - [ U ′ , S ′ , V ′ ] = SVD ( A w * ) ;
2 . - - - D = U w S ′ V w T ;
3.W *＝(D-S)/β；
4 . - - - d j = 1 C r Σ i p i | W i * | + β C r Σ i | W i * | p i 2 ;
5.If?d j＞thd，d j＝1，
If?d j＜thd，d j＝0，
Wherein: U, V are orthogonal matrix;
S is a diagonal matrix;
S wBe diagonal matrix;
D is for calculating median;
A w *Be image information;
W *Be watermark information;
β is the intensity that watermark embeds;
C rBe the sheet rate;
p iBe spread spectrum code sequence;
Thd is a threshold value.
3, a kind of device of the unified digital watermarking based on singular value decomposition and spread spectrum, comprise the code device of embed digital watermark and extract code translator two parts of digital watermarking, the code device of embed digital watermark, the singular value decomposition device, the spread spectrum device of watermark information, watermark flush mounting, the watermarked singular value decomposition device of image afterwards that comprise original image, form the image of band watermark at last, wherein:
The singular value decomposition device of original image: be that N * N gray level image is made singular value decomposition, obtain two orthogonal matrix U, V and a diagonal matrix S, the SVD method is exactly that watermark information is embedded in the singular value decomposition of original image;
The spread spectrum device of watermark information: be that various forms of watermarks are unified to handle;
Watermark flush mounting: the frequency expansion sequence W of watermark k, k=1,2 ..., be embedded on the diagonal matrix S in the scramble mode, obtain a new matrix S w
The singular value decomposition device of watermarked back image: be to S wCarry out singular value decomposition, obtain U w, S wAnd V w, wherein: S w = U w S w V w T , Compute matrix A then w=US wV TJust can obtain the image after watermarked.
4, the device of the unified digital watermarking based on singular value decomposition and spread spectrum as claimed in claim 3, it is characterized in that: the code translator that extracts digital watermarking, comprise the singular value decomposition device of image after the singular value decomposition device of being with watermarking images, watermark extraction apparatus, the extraction watermark, recover original image at last;
Extract the code translator of digital watermarking and finish decoding by following step:
1 . - - - [ U ′ , S ′ , V ′ ] = SVD ( A w * ) ;
2 . - - - D = U w S ′ V w T ;
3.W *＝(D-S)/β；
4 . - - - d j = 1 C r Σ i p i | W i * | + β C r Σ i | W i * | p i 2 ;
5.If?d j＞thd，d j＝1，
If?d j＜thd，d j＝0，
Wherein: U, V are orthogonal matrix;
S is a diagonal matrix;
S wBe diagonal matrix;
D is for calculating median;
A w *Be image information;
W *Be watermark information;
β is the intensity that watermark embeds;
C rBe the sheet rate;
p iBe spread spectrum code sequence;
Thd is a threshold value.
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