CN112561772A - Digital watermarking algorithm for solving false positive problem - Google Patents
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Abstract
The invention discloses a digital watermarking algorithm for solving the problem of false positive, which specifically comprises the following steps: step 1, selecting a carrier image and a watermark image: step 2, singular value transformation is carried out on the carrier image and the watermark image; step 3, designing a watermark embedding algorithm to obtain a watermark-containing image; step 4, designing a watermark extraction algorithm to obtain an extracted watermark image; and 5, carrying out a false positive test on the watermark-containing image. The algorithm can ensure the authenticity of extracting the watermark and improve the anti-counterfeiting coefficient.
Description
Technical Field
The invention belongs to the technical field of digital watermarking, and relates to a digital watermarking algorithm for solving the problem of false positive.
Background
With the progress of science and technology, the rapid development of network and computer communication technology makes the image information exchange simpler, and the development from the traditional paper media to the multimedia media makes the digital multimedia information spread more conveniently and rapidly under the background, and the digital multimedia information appears and is applied to various industries in the market in a large amount, so that the digital multimedia information communication system brings a great deal of opportunities to the industries such as commerce, entertainment, advertisement and the like and also brings challenges. A large amount of digital products appearing on the network are very easy to be attacked and utilized by pirates, so that the problems of information hiding, copyright protection and the like become increasingly prominent. The digital watermarking technology is widely researched and applied as an effective way for copyright protection, and both spatial watermarking and watermarking in a transform domain are greatly developed. In the current common algorithm, in order to improve the robustness of the watermark, singular value decomposition and frequency domain transformation are usually combined, although the robustness is greatly improved, a certain loophole exists, a counterfeiter can extract the false watermark from the image only embedded with the true watermark and not embedded with the false watermark by using the loophole, a good copyright protection effect cannot be achieved, the authenticity of the extracted watermark cannot be ensured, and the watermark is called as a 'false positive' watermark. If the problem of false positive can be solved, the difficulty coefficient of counterfeiting can be greatly increased, and the safety of copyright is ensured.
Disclosure of Invention
The invention aims to provide a digital watermarking algorithm for solving the problem of false positive, which can ensure the authenticity of extracted watermarks and improve anti-counterfeiting coefficients.
The invention adopts the technical scheme that a digital watermarking algorithm for solving the problem of false positive specifically comprises the following steps:
step 1, selecting a carrier image and a watermark image:
step 2, singular value transformation is carried out on the carrier image and the watermark image;
step 3, designing a watermark embedding algorithm to obtain a watermark-containing image;
step 4, designing a watermark extraction algorithm to obtain an extracted watermark image;
and 5, carrying out a false positive test on the watermark-containing image.
The present invention is also characterized in that,
the specific process of the step 1 is as follows: reading original carrier images I and watermark images W with equal sizes through MATLAB, and if the carrier images I and the watermark images W are color images, converting the carrier images and the watermark images into gray images by using an rgb2gray function.
The specific steps of the step 2 are as follows:
step 2.1, carrying out singular value decomposition on the carrier image I by adopting the following formula (1) to obtain a left singular matrix U, a singular value matrix S and a right singular matrix V of the carrier image I:
I＝USVT (1)；
step 2.2, performing singular value decomposition on the watermark image W by adopting the following formula (2) to obtain a left singular matrix U of the watermark imagemSingular value matrix SmAnd right singular matrix Vm。
W＝UmSmVm T (2)。
The specific process of the step 3 is as follows:
step 3.1, singular value matrix S of watermark image WmTransposed V to the right singular matrixm TMultiplying to obtain a multiplied matrix marked as Pc;
step 3.2, embedding the matrix Pc into a singular value matrix S of the carrier image by adopting a formula (3) with preset embedding strength alpha to obtain the matrix S2Wherein the preset embedding strength alpha has a value range of [0.01,0.5 ]]：
S2＝S+αPc (3)；
Step 3.3, obtaining the matrix S by adopting the formula (4)2Left singular matrix U of left-hand-multiplied carrier image and transposition V of right singular matrix of right-hand-multiplied carrier imageTObtaining a watermark-containing image Iw:
US2VT＝Iw (4)。
the specific steps of the step 4 are as follows:
step 4.1, subtracting the original carrier image from the image containing the watermark by adopting the formula (5) to obtain a subtracted image matrix I2：
I2＝Iw-I (5)；
Step 4.2, adopting the formula (6) to obtain an image matrix I2Transposition U of left singular matrix of left-hand-multiplied carrier imageTRight-hand singular matrix V of the carrier image, anddividing by the embedding strength α yields the extracted matrix Pcc:
Pcc＝(UTI2V)/α (6)；
and 4.3, adopting a formula (7) to pre-multiply the Pcc matrix by the left singular matrix U of the original watermark imagemTo obtain an extracted watermark image Wm：
UmPcc＝Wm (7)。
The specific process of the step 5 is as follows:
step 5.1, embedding the original watermark by adopting the process of the step 1-3, and storing the image Iw containing the watermark to prepare for a false positive test;
step 5.2, reading an uninserted gray watermark image with the same size as the original watermark image, and calling the gray watermark image as a false watermark image WfUsing formula (8) to correct the false watermark WfSingular value decomposition is carried out to obtain a left singular matrix UfAs a key at the time of extraction;
Wf＝UfSfVf T (8)；
step 5.3, repeatedly executing the step 4.1-4.2, and extracting a matrix Pcc;
step 5.4, the extracted matrix Pcc is used for left multiplication of the left singular matrix U of the false watermark mapfAnd extracting no false watermark image, namely, eliminating the false positive phenomenon.
The digital watermarking algorithm for solving the false positive problem is different from a conventional singular value embedding mode, solves the false positive problem existing in the existing watermarking algorithm utilizing singular value decomposition, improves the authenticity of watermark extraction, and increases the difficulty coefficient of counterfeiting by a counterfeiter.
Drawings
FIG. 1 is a flow chart of a watermark image embedding method of a digital watermark algorithm for solving the false positive problem of the present invention;
FIG. 2 is a flowchart of a watermark image extraction method of a digital watermark algorithm for solving the false positive problem according to the present invention;
FIG. 3 is a carrier image of an embodiment of a digital watermarking algorithm of the present invention that addresses the false positive problem;
FIG. 4 is a true watermark image of an embodiment of a digital watermarking algorithm of the present invention that addresses the false positive problem;
FIG. 5 is a false watermark image of an embodiment of a digital watermarking algorithm of the present invention that solves the false positive problem;
FIG. 6 is an image with embedded true watermark according to an embodiment of the digital watermarking algorithm for solving the false positive problem of the present invention;
FIG. 7 is a watermark image extracted from FIG. 6 using true watermarks in an embodiment of a digital watermarking algorithm for solving the false positive problem of the present invention;
fig. 8 is an image extracted from fig. 6 by using a false watermark according to an embodiment of the digital watermarking algorithm for solving the false positive problem.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention relates to a digital watermarking algorithm for solving the problem of false positive, which is implemented according to the following steps:
step 1, selecting a carrier image and a watermark:
reading original carrier images I and watermark images W with equal sizes through MATLAB, setting the sizes to be 128px multiplied by 128px to 1024px multiplied by 1024px, and if the carrier images and the watermark images are color images, converting the carrier images and the watermark images into gray images by using an rgb2gray function.
Step 2, respectively carrying out singular value decomposition on the carrier image and the watermark image;
and 2.1, carrying out singular value decomposition on the carrier image I by adopting the formula (1) to obtain a left singular matrix U, a singular value matrix S and a right singular matrix V of the carrier image.
I＝USVT (1)；
Step 2.2, performing singular value decomposition on the watermark image W by adopting the formula (2) to obtain a left singular matrix U of the watermark imagemSingular value matrix SmAnd right singular matrix Vm。
W＝UmSmVm T (2)。
Step 3, embedding the watermark to obtain the image containing the watermark, wherein the embedding method is as shown in figure 1:
singular value matrix S of watermark mapmTransposed V to the right singular matrixm TMultiplying to obtain a matrix Pc, and saving the left singular matrix of the watermark image as a secret key for extracting the watermark.
Setting a proper embedding proportion alpha, wherein the optimal value of alpha is different due to different choices of a carrier image and a watermark image, and the invisibility and the robustness of the watermark are influenced. Embedding the matrix Pc into a singular value matrix S of the carrier image with embedding strength alpha by adopting a formula (3) to obtain the matrix S2Wherein the preset embedding strength alpha has a value range of [0.01,0.5 ]]：
S2＝S+αPc (3)；
The matrix S obtained by the formula (4)2Left singular matrix U of left-hand-multiplied carrier image and transposition V of right singular matrix of right-hand-multiplied carrier imageTAnd obtaining the image Iw containing the watermark.
Step 4, extracting the watermark to obtain an extracted watermark image, wherein the extraction method is as shown in fig. 2:
subtracting the original carrier image I from the water-containing print image Iw by adopting the formula (5) to obtain a subtracted image matrix I2。
I2＝Iw-I (5)；
The obtained image matrix I is obtained by adopting the formula (6)2Transposition U of left singular matrix of left-hand-multiplied carrier imageTThe extracted matrix Pcc is obtained by right-multiplying the right singular matrix V of the carrier image by the embedding intensity α.
Pcc＝(UTI2V)/α (6)；
Multiplying Pcc matrix by left singular matrix U of original watermark image by formula (7)mTo obtain the extracted watermark Wm：
And 5, carrying out false positive test on the watermark-containing image:
the original watermark embedding process is carried out as the steps 1, 2 and 3, and the watermark-containing image Iw embedded in the original watermark is stored to prepare for a false watermark false positive experiment.
Reading another non-embedded grey scale image with the same size as the original watermark as the false watermark WfUsing formula (8) to correct the false watermark WfSingular value decomposition is carried out to obtain a left singular matrix UfAs a key at the time of extraction.
Wf＝UfSfVf T (8)；
The extraction process repeats step 4, the only difference being the use of the left singular matrix U of the pseudo-watermark patternfAnd multiplying the extracted matrix Pcc to obtain an extracted result graph, wherein the result shows that a false watermark graph cannot be extracted, and the false positive phenomenon is eliminated by the algorithm.
The digital watermarking algorithm for solving the false positive problem embeds the singular value matrix of the watermark image and the transposition of the right singular matrix into the carrier image together, changes the conventional embedding components of the watermark, is applied to the digital watermarking technology, solves the false positive problem existing in the traditional embedding mode in the prior art, ensures the authenticity of extracting the watermark and improves the anti-counterfeiting coefficient.
Examples
The invention specifically discloses a specific process for solving the problem of false positive by using a Lena image and a digital watermark image of 512px x 512px as a carrier image and a watermark image respectively to embed and extract a watermark algorithm and using a check mark image of 512px x 512px as a false watermark to perform false positive test of the algorithm.
Step 1, selecting a carrier image and a watermark:
carrier image I selected here1A Lena graph of 512px × 512px, a watermark image W1The carrier image and the watermark image are both gray level images in a 512 px-512 px digital watermark image. The carrier image is shown in fig. 3;
step 2, carrying out singular value decomposition on the carrier image and the watermark image respectively:
singular value decomposition is carried out on the Lena image of the carrier image to obtain U of a left singular matrixiSingular value matrix SiAnd right singular matrix Vi。
Singular value decomposition is carried out on the watermark image 'digital watermark' image to obtain a left singular matrix UwSingular value matrix SwAnd right singular matrix Vw。
Step 3, embedding the watermark to obtain a watermark-containing image:
singular value matrix S of watermark mapwTransposed V to the right singular matrixw TMultiplying to obtain a matrix Pc1Left singular matrix U of watermark diagramwThe key used for extracting the watermark is saved.
Setting a proper embedding proportion alpha, wherein the optimal value of alpha is different due to different choices of a carrier image and a watermark image, the invisibility and the robustness of the watermark are influenced, and alpha is 0.01. Using equation (3) to align the matrix Pc1Singular value matrix S embedded in a carrier image with an embedding strength α of 0.01iIn (1), obtain a matrix Siw。
The matrix S obtained by the formula (4)iwLeft singular matrix U of left-hand-multiplied carrier imageiTranspose of right singular matrix of right-multiplied carrier image Vi TObtaining the image I containing the watermarkw。
Step 4, extracting the watermark to obtain an extracted watermark image:
watermarking image I by adopting formula (5)wWith the original carrier image I1Subtracting to obtain a subtracted image matrix I3。
The obtained image matrix I is obtained by adopting the formula (6)3Transposition U of left singular matrix of left-hand-multiplied carrier imagei TRight ridingRight singular matrix V of volume imageiAnd then divided by the embedding strength of 0.01 to obtain an extracted matrix Pc2。
Using formula (7) to mix Pc2Left singular matrix U of matrix left-multiplication original watermark imagewTo obtain the extracted watermark W2。
And 5, carrying out false positive test on the watermark-containing image:
the original watermark embedding process is carried out as the step 1, the step 2 and the step 3, and the watermark-containing image embedded in the original watermark is stored to prepare for the false watermark and false positive experiment.
Reading another non-embedded gray watermark image 'school badge image' with the size of 512px multiplied by 512px, and calling the school badge image as a false watermark WhUsing formula (8) to correct the false watermark WhSingular value decomposition is carried out to obtain a left singular matrix UhAs a key at the time of extraction.
The extraction process repeats step 4, the only difference being the left singular matrix of the pseudo-watermark pattern and the extracted matrix Pc2And multiplying to obtain an extracted result graph, wherein the result shows that a false watermark graph cannot be extracted, and the algorithm eliminates the false positive phenomenon. Fig. 4 is a diagram of a true watermark image in the present embodiment; fig. 5 is a pseudo watermark image in the present embodiment; FIG. 6 is an image with a true watermark embedded in the present embodiment; fig. 7 is a watermark image extracted from fig. 6 by using a true watermark in the present embodiment; fig. 8 is an image extracted from fig. 6 by a false watermark in the present embodiment.
Claims (6)
1. A digital watermarking algorithm for solving the problem of false positives is characterized in that: the method specifically comprises the following steps:
step 1, selecting a carrier image and a watermark image:
step 2, singular value transformation is carried out on the carrier image and the watermark image;
step 3, designing a watermark embedding algorithm to obtain a watermark-containing image;
step 4, designing a watermark extraction algorithm to obtain an extracted watermark image;
and 5, carrying out a false positive test on the watermark-containing image.
2. A digital watermarking algorithm that solves the problem of false positives as claimed in claim 1, characterized in that: the specific process of the step 1 is as follows: reading original carrier images I and watermark images W with equal sizes through MATLAB, and if the carrier images I and the watermark images W are color images, converting the carrier images and the watermark images into gray images by using an rgb2gray function.
3. A digital watermarking algorithm that solves the problem of false positives as claimed in claim 2, characterized in that: the specific steps of the step 2 are as follows:
step 2.1, carrying out singular value decomposition on the carrier image I by adopting the following formula (1) to obtain a left singular matrix U, a singular value matrix S and a right singular matrix V of the carrier image I:
I＝USVT (1)；
step 2.2, performing singular value decomposition on the watermark image W by adopting the following formula (2) to obtain a left singular matrix U of the watermark imagemSingular value matrix SmAnd right singular matrix Vm。
W＝UmSmVm T (2)。
4. A digital watermarking algorithm that solves the problem of false positives as claimed in claim 3, characterized in that: the specific process of the step 3 is as follows:
step 3.1, singular value matrix S of watermark image WmTransposed V to the right singular matrixm TMultiplying to obtain a multiplied matrix marked as Pc;
step 3.2, embedding the matrix Pc into a singular value matrix S of the carrier image by adopting a formula (3) with preset embedding strength alpha to obtain the matrix S2Wherein the preset embedding strength alpha has a value range of [0.01,0.5 ]]：
S2＝S+αPc (3)；
Step 3.3, obtaining the matrix S by adopting the formula (4)2Left-hand carrier imageU, transpose V of right singular matrix of right-multiplied carrier imageTObtaining a watermark-containing image Iw:
US2VT＝Iw (4)。
5. a digital watermarking algorithm that solves the problem of false positives as claimed in claim 3, characterized in that: the specific steps of the step 4 are as follows:
step 4.1, subtracting the original carrier image from the image containing the watermark by adopting the formula (5) to obtain a subtracted image matrix I2：
I2＝Iw-I (5)；
Step 4.2, adopting the formula (6) to obtain an image matrix I2Transposition U of left singular matrix of left-hand-multiplied carrier imageTMultiplying the right singular matrix V of the carrier image by the right singular matrix V, and dividing by the embedding intensity α to obtain an extracted matrix Pcc:
Pcc＝(UTI2V)/α (6)；
and 4.3, adopting a formula (7) to pre-multiply the Pcc matrix by the left singular matrix U of the original watermark imagemTo obtain an extracted watermark image Wm：
UmPcc＝Wm (7)。
6. A digital watermarking algorithm that solves the problem of false positives as claimed in claim 3, characterized in that: the specific process of the step 5 is as follows:
step 5.1, embedding the original watermark by adopting the process of the step 1-3, and storing the image Iw containing the watermark to prepare for a false positive test;
step 5.2, reading an uninserted gray watermark image with the same size as the original watermark image, and calling the gray watermark image as a false watermark image WfUsing formula (8) to correct the false watermark WfSingular value decomposition is carried out to obtain a left singular matrix UfAs a key at the time of extraction;
Wf＝UfSfVf T (8)；
step 5.3, repeatedly executing the step 4.1-4.2, and extracting a matrix Pcc;
step 5.4, the extracted matrix Pcc is used for left multiplication of the left singular matrix U of the false watermark mapfAnd extracting no false watermark image, namely, eliminating the false positive phenomenon.
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