CN101004830A - Robust watermark technique of digital image selected from space domain of images - Google Patents
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Abstract
A method for embedding watermark on robust digital image of airspace image includes using chose sequence generated by cipher key to select initial image pixel block, seeking optimum matched block with said pixel block in complete image, recombining them as per their generated order and making DWT conversion, dividing watermark information as per their importance, realizing unequal error protection by utilizing orthogonal variable length OVSF code spread spectrum treatment and embedding spread spectrum watermark into DWT wavelet coefficient. The method for picking up watermark is also disclosed.
Description
Technical field
The present invention relates to a kind of Robust digital figure watermark technology of selecting based on the spatial domain image, is a kind of multimedia data protection method, belongs to field of multimedia signal processing.
Background technology
Along with the continuous development of multimedia technology, the copyright problem of copyright becomes a focus of present concern.In order to address this problem, digital watermark technology has been proposed in the world.Digital watermark technology is a kind of brand-new information security technology that combines technology such as signal Processing, digital communication, pattern-recognition, cryptography and Internet, and it provides a kind of new thinking for copyright protection.Digital watermark technology is one of effective ways of protection Digital Media copyright at present.
Digital watermark technology confirms the entitlement of these data by embed watermark in raw data (watermark) information. and do not influence the availability of raw data, and should be able to resist various have a mind to or attacks unintentionally, i.e. watermark should have robustness preferably.The watermark information that embeds can be the proprietorial literal of representative, product or everyone ID, two dimensional image, random series etc.
In recent years, the research of digital watermark technology has obtained very big progress, and some technology has been used for commercial object.Digital watermark technology has a variety of, according to different purposes, has a lot of different sorting techniques, for example: according to the purposes of carrier, can be divided into rest image, video, audio frequency, text document, binary code stream etc.; According to appearance characteristics, can be divided into visible watermark and invisible watermark (robust watermark, fragile watermark); According to detection method, be divided into secret and open watermark, private key and PKI watermark etc.; According to embedding strategy, be divided into spatial domain watermark, transform domain watermark etc.At present research is more transform domain digital watermarking algorithm, compression domain digital watermarking algorithm, physiological models algorithm, based on the digital watermarking algorithm of chaotic model and spread spectrum digital watermarking algorithm etc.
The most of digital watermarking schemes that propose mostly can only be resisted several frequently seen attack at present, as compression of images, and filtering, attacked by noise and other some signal processing operations.And for translation, rotation, stretch or even small its robust performance of geometric attack all relatively poor.The DFT conversion is adopted in the digital watermarking of most of resist geometric attacks, incompatible with present JPEG2000 Standard of image compression and JPEG compression standard, therefore in digital watermarking research, the digital watermark technology that obtains more efficiently resist geometric attacks and normal image processing operation becomes very important.
Summary of the invention
The objective of the invention is to propose a kind of digital watermarking embedding and extracting method that common image processing operations is had higher robustness as compression, noise etc. and geometric attack as rotation, translation etc.
The technical solution adopted for the present invention to solve the technical problems comprises that watermark embeds and extract the two large divisions.First is that watermark embeds, and comprising:
(1) original watermark information is divided into i grade by importance; carry out orthogonal spectrum expansion with the orthogonal variable spreading factor ovsf code and handle, to the long ovsf code spread spectrum of pith, according to importance; select the spreading code of unequal length successively for use, reach the effect of unequal error protection.
(2) be the chaotic maps initial value with the key, obtain the chaos random series, chaos sequence is carried out quantification treatment, as index, select the initial pictures block of pixels with quantized value.
(3) be starting point with the initial pictures block of pixels, form the block of pixels of N * N size,, in entire image, select the blocks and optimal matching blocks with size such as initial pixel piece, make the MSE that defines between itself and the initial pixel piece according to the similarity of image pixel information
MReach minimum, select MSE
MBe worth minimum p piece as blocks and optimal matching blocks, and blocks and optimal matching blocks is reconfigured, carry out the DWT wavelet transformation.
(4) watermark information behind the spread spectrum is embedded in the DWT wavelet conversion coefficient of blocks and optimal matching blocks.
Second portion is a watermark extracting, comprising:
(5) recovering key is the chaotic maps initial value, obtains the chaos random series, and chaos sequence is carried out quantification treatment, as index, selects the initial pictures block of pixels of watermarking images with quantized value.
(6) the initial pixel piece with watermarking images is a starting point, according to the MSE of definition
MIn entire image, select blocks and optimal matching blocks, it is reconfigured, and carry out the DWT wavelet transformation.
(7) adopt correlation detection, the spread-spectrum watermark information that embeds is carried out despreading handle, recover original watermark information.
The spread spectrum coding The Application of Technology has improved the confidentiality and the security of system.Along with the increase of spreading code length, the security and the robustness of system improve thereupon.The present invention has adopted the unequal error technology, by importance original watermark information is divided, it is divided into different grades, part to outbalance in the raw information adopts long spreading code to carry out spread processing, the spread spectrum code length of other part successively decreases successively, has effectively guaranteed the accuracy of watermark information when detecting.
Aspect selection watermark information position,, calculate the square error function MSE of definition according to the similarity between the block of image pixels
MIn entire image, select similar each other block of pixels, in the time of geometric attacks such as image is rotated, translation, because though the relative position between each block of image pixels has changed, but the similarity between each block of image pixels is not changed, and still can determine the position that watermark embeds comparatively accurately according to the similarity between the block of pixels, so can extract watermark information comparatively accurately, therefore aspect resist geometric attacks, have superiority.
In addition, the application of chaos random series has increased the security of algorithm, and wavelet transformation has the advantage of time-space domain and the conversion of DCT territory concurrently.The high-frequency region of DWT wavelet transformation has all shown weak robustness at aspects such as opposing JPEG compression, low-pass filtering, attacked by noise, but its invisibility is good; And low frequency region has robustness preferably aspect the various signal processing operations of opposing, but embeddable capacity is less, and invisibility is poor.Watermark information is embedded in DWT intermediate frequency zone, both guarantees the invisibility of the image of embed watermark, strengthened the robustness of various common signal Processing such as watermaking system opposing compression, filtering, noise again.
The geometric attack that the present invention suffers carrier image has resistibility preferably, particularly attacks such as rotation, translation, and general signal Processing such as operations such as filtering, compression also had good robustness.
Description of drawings
The match block of Fig. 1-initial pixel piece is selected
Fig. 2-watermark embed process
Fig. 3-watermark detection process
Fig. 4-DWT wavelet transformation
Embodiment
The invention will be further described below in conjunction with drawings and Examples:
At first with one group of binary sequence B={b that can represent copyright information
0, b
1..., b
L-1, b
i∈ 1,1} is as digital watermarking, the original image note do X={x (i, j) | i≤M
1, j≤M
2, wherein, M
1* M
2Be the image size, x (i j) is the pixel value of image, and the telescopiny of watermark is as follows as shown in Figure 2:
Step 1. couple original watermark information B={b
0, b
1..., b
L-1Be divided into i grade G by importance
1, G
2G
i, importance is successively decreased successively with the increase of i, wherein G
1For
Most important, G
2For
Inferior important, G
iImportance minimum.Carry out orthogonal spectrum expansion with the orthogonal variable spreading factor ovsf code and handle, to pith G
1With long ovsf code spread spectrum, its spreading factor is C
r=2
k, G
2And G
iThe part spreading factor is decremented to 2
K-1, 2
K-i+1(k is a positive integer) obtains the watermark information W behind the spread spectrum.
Step 2. is the chaotic maps initial value with the key, obtains the chaos random series, and chaos sequence is carried out quantification treatment, as index, selects the initial pictures block of pixels with quantized value.
Chaos is nonlinear equation (group) separating under given conditions, and its output at random determines that by one equation (group) determines.Its initial parameter can be used as system key, the characteristics that chaos system has good performance at random and regenerates easily, and this has increased the security of system.With the one dimension chaotic maps is example f:U → U, U ∈ R
z(n+1)=f(λ,z(n)),λ∈R,z(n)∈U
Wherein, n is a positive integer, the expression iterations, and λ is a systematic parameter.The real-valued sequence that the following formula iteration obtains for n time for z (1), z (2) ..., z (n) }.Choose num different chaos value, each chaos value is mapped as col (i) ∈ M1, two vectors of row (i) ∈ M2, i={1 wherein, 2 ..., num}, num are the number of initial pixel piece, col and row are the position at initial pixel piece place.
Step 3. as shown in Figure 1, (col row) is starting point with the initial pictures block of pixels, form the block of pixels of N * N size, according to the similarity of Pixel Information between image, in entire image, select the blocks and optimal matching blocks with size such as initial pixel piece, make the definition MSE between itself and the initial pixel piece
MReach minimum, select MSE
MMinimum p as blocks and optimal matching blocks.
The upper left corner of image initial block of pixels is positioned at that (i, j), then the block of pixels of N * N size can be expressed as { x
I+m, j+n| 0≤m≤N-1,0≤n≤N-1}.The spectrum transfer function is defined as x
I+m, j+n→ v (x
I+m, j-n) here, v is an one dimension real number equation.V is defined as
V (z)=a
0+ a
1Z or v (z)=z
Wherein
The block of pixels of sizes such as calculating and initial pixel piece and the MSE between the initial pixel piece
M, MSE wherein
MBe defined as:
When choosing, select MSE for use
MP block of pixels of value minimum is as initial pixel piece (i, blocks and optimal matching blocks j).
(col row) all does above-mentioned identical processing, obtains a series of blocks and optimal matching blocks, reconfigures according to the order that produces to be subimage X to each initial pixel piece
New, and to subimage X
NewCarry out the secondary wavelet transformation.
The watermark information of step 4. after with spread spectrum is embedded in subimage X
NewThe intermediate frequency HL of secondary wavelet conversion coefficient
1, LH
1, HL
2, LH
2In the sub-band coefficients.
Adopt embedding grammar commonly used, embedding formula is X
New=X
New+ α W, wherein α is an embedment strength.
Amended coefficient is carried out the IDWT inverse transformation obtain X
New, with X
NewTo original image, obtain the image X ' behind the embed watermark by the initial arrangement order recovery.
The leaching process of watermark is as follows:
It is the chaotic maps initial value that step 1. is recovered key, obtains the chaos random series, and chaos sequence is carried out quantification treatment, as index, selects the initial pictures block of pixels of watermarking images with quantized value.
After the one dimension chaotic maps being carried out n iteration, from the real-valued sequence that produces, find num identical when embedding chaos value, and it is mapped as two-dimensional vector col (i) ∈ M
1, row (i) ∈ M
2, i={1 wherein, 2 ..., num}, num are the number of initial pixel piece, col and row are the position at initial pixel piece place.
Step 2. is a starting point with the initial pixel piece of watermarking images, forms the block of pixels of N * N size, according to definition MSE
MIn entire image, select MSE
MBe worth p minimum block of pixels as blocks and optimal matching blocks, and reconfigure according to the order that produces.
Image after step 3. pair reconfigures carries out secondary DWT wavelet transformation, extracts the intermediate frequency subband wavelet coefficient HL that embeds, LH
1, HL
2, LH
2
Step 4. adopts correlation detection to extract watermark information, does relevant despreading with the orthogonal variable spreading factor ovsf code that produces with the regional wavelet coefficient of embedding and handles.
Coherent detection is:
, X wherein
New(i) for watermarking images embeds regional wavelet coefficient values, PN (i) is an ovsf code.If ρ>0 b '=1, otherwise b '=0.
Be easy to realize the extraction and the detection of digital watermarking according to above introduction.Use the present invention and can resist geometric attacks such as translation, rotation effectively, and image processing operations such as general Flame Image Process such as JPEG compression are also had good robustness.
Claims (5)
1. Robust digital figure watermark technology that the spatial domain image is selected is characterized in that: comprise following concrete steps:
First is the embedding of watermark information, mainly comprises:
1) with the initial value of key, obtains the chaos random series, the chaos random series is quantized, and select the initial pictures block of pixels with quantized value as chaotic maps;
2) be initial point with the initial pictures block of pixels, form the block of pixels of N * N size,, in entire image, seek the blocks and optimal matching blocks with size such as initial pixel piece, promptly similar, make the MSE between itself and the initial pixel piece according to the similarity between the image block
MReach minimum, select MSE
MThe p piece of value minimum is reassembled into subimage with blocks and optimal matching blocks in proper order by generation, and carries out the DWT wavelet transformation as blocks and optimal matching blocks;
3) original watermark information is carried out unequal error protection; it is divided according to importance; and carry out orthogonal variable spreading factor sign indicating number spread processing by importance; select the spreading code of unequal length successively for use; important information is used than long spreading code spread spectrum, and the watermark information behind the spread spectrum is embedded in the carrier image match block DWT wavelet coefficient.
Second portion is the extraction of watermark information, mainly comprises:
4) be the chaotic maps initial value with the key equally, obtain the chaos random series, chaos sequence is carried out quantification treatment, as index, select the initial pictures block of pixels of watermarking images with quantized value;
5) the initial pixel piece with watermarking images is a starting point, according to the MSE of definition
MIn entire image, select blocks and optimal matching blocks, it is reconfigured, and carry out the DWT wavelet transformation;
6) adopt correlation detection, the spread-spectrum watermark information that embeds is carried out despreading handle, recover original watermark information.
2. the Robust digital figure watermark technology that a kind of spatial domain according to claim 1 image is selected; it is characterized in that: original watermark information is carried out unequal error protection; it is divided into i grade according to importance; and, select for use the spreading code of unequal length to carry out the spread spectrum protection successively by importance.
3. the Robust digital figure watermark technology that a kind of spatial domain according to claim 1 image is selected, it is characterized in that: according to the susceptibility of chaos sequence initial value, when embedding, produce chaos sequence with key, and it is quantized the initial pixel piece position that image is selected in the back.
4. the Robust digital figure watermark technology that a kind of spatial domain according to claim 1 image is selected, it is characterized in that: with the initial pictures block of pixels is initial point, form the block of pixels of N * N size, according to the similarity between the block of image pixels, the blocks and optimal matching blocks of sizes such as searching and initial pixel piece in entire image, be similar, make the MSE that defines between itself and the initial pixel piece
MReach minimum, select MSE
MThe p piece of value minimum is as blocks and optimal matching blocks.
5. the Robust digital figure watermark technology that a kind of spatial domain according to claim 1 image is selected is characterized in that: the blocks and optimal matching blocks of selecting is reassembled into a new subimage according to the order that produces, and subimage is carried out the DWT conversion.
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CN101847251A (en) * | 2010-06-13 | 2010-09-29 | 电子科技大学 | Digital watermark embedding and extraction method based on chaos sequences |
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CN101782947B (en) * | 2008-12-19 | 2011-12-14 | 天津易步科技发展有限公司 | Multimedia copyright protection method |
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