CN110197456A - A kind of color image hard copy holographic watermark method - Google Patents
A kind of color image hard copy holographic watermark method Download PDFInfo
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- KKAJSJJFBSOMGS-UHFFFAOYSA-N 3,6-diamino-10-methylacridinium chloride Chemical compound [Cl-].C1=C(N)C=C2[N+](C)=C(C=C(N)C=C3)C3=CC2=C1 KKAJSJJFBSOMGS-UHFFFAOYSA-N 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T1/00—General purpose image data processing
- G06T1/0021—Image watermarking
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2201/00—General purpose image data processing
- G06T2201/005—Image watermarking
- G06T2201/0065—Extraction of an embedded watermark; Reliable detection
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Abstract
The invention discloses a kind of color image hard copy holographic watermark method, include the following steps: to choose the watermarking images that size is n*n；Watermark is generated, DFT processing is expanded and carried out to watermarking images and carrier image second level dwt transformation high fdrequency component by being conjugated symmetric extension, obtains the digital hologram for the watermarking images that size is 2n*2n；It is embedded in watermark, the digital hologram of watermarking images is converted by DWT, using high frequency HL1 parts of images as watermarking images to be embedded, the R-portion for the carrier image RGB color space that size is 4n*4n is embedded in, forms the carrier image containing watermark；Watermark is extracted, second level DWT transformation is done to the R-portion of the RGB color space of the carrier image containing watermark, restores the digital hologram in carrier image, DFT transform is carried out to digital hologram and extracts amplitude information, obtains watermarking images.The watermarking algorithm provides new effective means for the copyright protection of color image, has certain practical value in printing anti-counterfeit field.
Description
Technical field
The present invention relates to printing anti-counterfeit field, especially a kind of color image hard copy holographic watermark methods.
Background technique
The technology of the development of the copyright protection technology of copyright, especially digital watermark technology as its core, wherein
Anti- printing and scanning (Print and Scan, PS) watermarking algorithm can be applied in the copyright protection of printed article.Due to PS process
Including multiple digital-to-analogue conversion, different environment can influence printed article by illumination variation, color change etc., so that the works of protection
It is subject to various attacks, the attack superposition of variation in rigidity etc., it is difficult to restore the watermark wherein hidden.Thus anti-PS digital watermark
Research become the most important thing.Ching-Yung Lin et al. had studied anti-PS digital watermark in 1999 earliest, hereafter, was attacking
A series of researchs are carried out in terms of various distortions caused by gram PS.But embedded watermark content accounting is limited by image size,
The difficult points such as the digital watermark industrialization that insertion is extracted limit always digital watermark and come into operation in copyright protection.
Computer and holographic the two combine the calculating generated holographic (Computer Generated Holography, CGH)
Technology is greatly developed in recent years, especially in field relevant with image.Existing countermeasure includes insertion template method, insertion
Watermark and searching characteristics of image with motor synchronizing characteristic carry out watermark synchronization etc..Although can partially solve robustness to ask
Topic, but still there are many shortcomings: (1) calculating step more complicated, cumbersome and hard to understand, is unfavorable for promoting the use of；(2) it lacks
The weary Unified Algorithm suitable for various images especially to color image, and not can guarantee the capacity of insertion watermark；(3) majority side
Method is only limitted to insertion binary watermarking information, and for Gray-level Watermarking, usual effect is very bad；(4) existing method can only be fought mostly
Some particular attack, and other attack types even combination attacks can not then be resisted.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of color image hard copy holographic watermark sides
Method includes the following steps:
Step 1: the watermarking images that size is n*n are chosen；
Step 2: generating watermark, and watermarking images and carrier image second level dwt transformation high fdrequency component are symmetrically prolonged by conjugation
Expansion simultaneously carries out DFT processing, obtains the digital hologram for the watermarking images that size is 2n*2n；
Step 3: the digital hologram of watermarking images is converted by DWT, high frequency HL1 parts of images is made by insertion watermark
For watermarking images to be embedded, it is embedded in the R-portion for the carrier image RGB color space that size is 4n*4n, is formed containing watermark
Carrier image；
Step 4: extracting watermark, does second level DWT transformation to the R-portion of the RGB color space of the carrier image containing watermark,
The digital hologram in carrier image is recovered, DFT transform is carried out to digital hologram and extracts amplitude information, obtains watermark figure
Picture.
Further, the watermarking images chosen in step 1 use binary bitmap or Gray-level Watermarking image.
Further, watermarking images are extended described in step 2 by way of being conjugated symmetric extension, and carries out DFT
Processing, obtains the digital hologram of watermarking images, comprises the following processes:
(1) conjugation symmetric extension extension is carried out to watermarking images M, generates extension watermarking images M1；
(2) extension watermarking images M1 is raw as amplitude and carrier image second level dwt transformation high fdrequency component conjugation symmetric extension
At image N；
(3) DFT transform is carried out to watermarking images N and obtains watermarking images O；
(4) watermarking images O is normalized, obtains the digital hologram of watermarking images.
Further, the digital hologram of watermarking images is embedded in carrier image RGB color sky described in step 3
Between R-portion, formed and included the following steps: comprising the carrier image of watermark
(1) carrier image pre-processes, and does second level DWT transformation to the R-portion of the RGB color space of carrier image, obtains face
The respective distribution map of colouring component R, G, B, and extract the wavelet coefficient H of the HL2 layer of color component R；
(2) digital hologram of watermarking images is carried out DWT transformation to extract HL1 wavelet coefficient W, W being water to be embedded
Print；
(3) it is embedded in watermark, second level DWT transformation is carried out to carrier image, obtains second level coefficient HL2, LL2, LH2, HH2, two
Grade wavelet coefficient LL2, LH2, HH2 are remained unchanged, and second level wavelet coefficient HL2 and W are combined, using following calculation formula:
Std [H] indicates the standard deviation of H in formula, the regulatory factor of embedment strength is indicated, as a=std [W]/std [H]
When, it is equivalent to and extracts the part HL2 that the part HL1 W directly replaces carrier image second level DWT with the DWT transformation of watermark；, it is W, H's
Mean value；
(4) by after in conjunction with W second level wavelet coefficient HL2 and other three second level wavelet coefficient LL2, LH2, HH2 conjunctions arrive
Another mistake DWT is converted together, obtains level-one wavelet coefficient LL1；Again by LL1 and other three level-one wavelet coefficients LH1, HL1, HH1
Inverse DWT is converted, and synthesizes R component with watermarked information, then synthesized by R component with watermarked information, color component G, color component B
Carrier image comprising watermark information.
Further, watermark extracting described in step 4 specifically comprises the following processes:
(1) it pre-processes, second level DWT transformation is done to the R-portion of the carrier image containing watermark, obtains corresponding second level wavelet systems
The coefficient distribution of number each layer of LL2, LH2, HH2, HL2；
(2) watermark is extracted, extracts HL2 layers of wavelet coefficient, and the wavelet coefficient embedment strength factor is restored to obtain
Digital hologram；
(3) restore watermark, DFT transform is carried out to digital hologram, and extract amplitude information, restore watermarking images.
Further, a wavelet basis is selected to make the wavelet coefficient W in wavelet coefficient H and step (2) in step (1)
It is equal in magnitude.
The beneficial effects of the present invention are: this method is embedded in holographic watermark in color image, watermark is the complete of conjugation continuation
Cease watermark, can not tearing to pieces property can help to blindly extract stronger watermark information.It, can be from printing and sweep by various distortion corrections
Tracing extracts preferable watermark information as in, and this method has the attack such as stronger anti-cutting, compression, noise.With it is similar
Watermarking algorithm is compared, and is obtained the PSNR value of the higher carrier image containing watermark, is enhanced watermark robustness, balance high robust
And invisibility.
Detailed description of the invention
Fig. 1 is a kind of flow chart of color image hard copy holographic watermark method；
Fig. 2 is the generating process of the digital hologram of watermarking images；
Fig. 3 is that watermark is embedded in flow diagram；
Fig. 4 is watermark extracting flow diagram；
Fig. 5 is that schematic diagram is extracted in watermark insertion；
Fig. 6 is the embedment strength factor and the schematic diagram of PSNR containing watermarking images；
Fig. 7 is to the watermark schematic diagram extracted after handling containing watermarking images；
Fig. 8 is the watermark schematic diagram of geometric attack and extraction；
Fig. 9 is the watermark schematic diagram of image and extraction after printing and scanning attack；
Figure 10 is the watermark list that the different degrees of PS attack containing watermarking images is extracted.
Specific embodiment
Technical solution of the present invention is described in further detail with reference to the accompanying drawing, but protection scope of the present invention is not limited to
It is as described below.
As shown in Figure 1, this method is adopted international standards test image lena, peppers etc. with figure, tool is
matlab2013b.Mainly for cutting, compression, noise, there are also PS etc. to attack.Carrier image pixel is 512 × 512, and watermark is complete
The pixel size for ceasing image part HL1 after DWT is converted is 128 × 128.The watermark information capacity of insertion is larger, works as watermark
When for bianry image, insertion watermark capacity is 128 × 128=16384, thus effectively content 16384bit；When watermark is gray scale
When image, insertion watermark amount is 128 × 128 × 8=131072, thus has effective content 131072bit.Fig. 5 illustrated process is
As an example with lena cromogram, (a) is lena cromogram；It (b) is original watermark image, as an example with two-value smiling face figure；
(c) hologram generated for (b)；(d) for hologram into cross the transformed HL1 part figure of DWT；(e) for by HL1 part again
Existing watermark information；It (f) is the lena color image of insertion watermark, PSNR 39.89；(g) in the lena image containing watermark
(f) watermark information extracted in.
Layout, the embedment strength factor of watermark information in watermarking images etc. influences watermark effect.When the embedment strength factor
It reducing, the PSNR value of the carrier image containing watermark then increases, but the embedment strength factor is too low then it is difficult to extract watermark information out, because
And select suitable watermark embedment strength that the robustness of watermark and invisibility are balanced well.Fig. 6 is that insertion is strong
The schematic diagram of the factor and the PSNR containing watermarking images is spent, abscissa is the intensity factor for being embedded in watermark, and intensity factor is from 0 to 1.5
It is sequentially increased, the PSNR value between ordinate carrier image and image containing watermark is successively reduced, and curve is not monotonicity
Curve, when the embedment strength factor is less than 1, PSNR is greater than 37dB.The PSNR of the figure of lena containing watermark that flavine Juan et al. proposes is
37.5dB is straight line, it is known that method of the invention is being appropriately embed under intensity, can get higher containing watermarking images
Quality.When watermark is binary watermarking, R is the watermark related coefficient for measuring watermark robustness:
When watermark is Gray-level Watermarking, R value is normalization coefficient (Normalization Coefficient, NC).
Fig. 7 be to containing watermarking images done on photoshop respectively Gaussian Blur, contrast variation, USM sharpen etc. attack
It hits, extracts the binary watermarking of watermark and the threshold values judgement of gray scale respectively.The R value for extracting watermark is calculated by formula (1) (2).
Being not subject to its R value of the watermark of any attack extracted containing watermarking images is 1；Contain watermarking images by 3 × 3 Gaussian Blurs
Its R value of the watermark information of extraction is 0.98；USM sharpens the watermark information extracted containing watermarking images, then passes through threshold values binaryzation
Its R value of watermark information is 1.00；Enhance the watermark information extracted containing watermarking images by contrast, then passes through threshold values binaryzation
Its R value of watermark information is 0.99；The watermark information extracted by contrast reduction containing watermarking images, then pass through threshold values binaryzation
Its R value of watermark information is 1.00；The watermark information that mean filter is extracted containing watermarking images, then believed by the watermark of threshold values binaryzation
Ceasing its R value is 0.98；The watermark information that median filtering is extracted containing watermarking images, then pass through its R of the watermark information of threshold values binaryzation
Value is 0.94；It rotates the watermark information extracted containing watermarking images and passes through the watermark information of threshold values binaryzation when angle is 0.1 °
Its R value is 1.00；It is 0.81 by its R value of the watermark information of threshold values binaryzation when its angle is 1 °；Pass through the bimodal of hologram
It is easy to judge that suitable threshold values makes its binaryzation, and the watermark after binaryzation is recognized more easily by human eye.
The cutting in geometric attack, noise, angle rotation, compression etc. are carried out to the image of lena containing watermark respectively to attack and mention
Take watermark information.Fig. 8 is to the geometric attack containing watermarking images, and (a) (b) (c) mainly cuts 10% to carrier image respectively,
25%, the watermark information extracted after 50%.To the watermark for cutting image zooming-out as it can be seen that this algorithm resists certain shearing attack,
But it cuts and is difficult to recognize watermark information when being greater than half.(d) the JPEG attack of (e) (f) containing carrier image, compression quality Factor minute
It is not 100,80,50, this algorithm resists slight compression attack.(g) (h) (i) adds Gaussian noise to each section containing carrier image
Attack, (j) (k) resists certain attacked by noise to the attack of containing watermarking images plus salt-pepper noise, this algorithm.
Fig. 9 is containing watermarking images by the watermark information extracted after printing and scanning attack.Printer and scanner are differentiated
Rate is both configured to most common resolution ratio, and is not corrected to color of image, and image is by geometric attack and comparison after PS
Degree distortion, when resetting the size of image, clarity is also inevitably lost.(a) image will be reset after watermarking images PS being contained
The watermark of lena image after size containing watermark and extraction, R 0.76；(b) contain watermarking images after (a) being adjusted luminance distortion,
The watermark R of extraction is 0.81.The algorithm can extract watermark after experiment shows PS attack, and can be extracted by distortion correction
The watermark information of better quality.The above is only a preferred embodiment of the present invention, it should be understood that the present invention is not limited to
Form disclosed herein should not be regarded as an exclusion of other examples, and can be used for various other combinations, modification and ring
Border, and can be in contemplated scope described herein, modifications can be made through the above teachings or related fields of technology or knowledge.And this
The modifications and changes that field personnel are carried out do not depart from the spirit and scope of the present invention, then all should be in appended claims of the present invention
Protection scope in.
Claims (6)
1. a kind of color image hard copy holographic watermark method, which comprises the steps of:
Step 1: the watermarking images that size is n*n are chosen；
Step 2: generating watermark, and watermarking images and carrier image second level dwt transformation high fdrequency component are opened up by being conjugated symmetric extension
DFT processing is opened up and carried out, the digital hologram for the watermarking images that size is 2n*2n is obtained；
Step 3: insertion watermark, by the digital hologram of watermarking images by DWT transformation, using high frequency HL1 parts of images as to
The watermarking images of insertion are embedded in the R-portion for the carrier image RGB color space that size is 4n*4n, form the carrier containing watermark
Image；
Step 4: extracting watermark, does second level DWT transformation to the R-portion of the RGB color space of the carrier image containing watermark, restores
Digital hologram in carrier image out carries out DFT transform to digital hologram and extracts amplitude information, obtains watermarking images.
2. a kind of color image hard copy holographic watermark method according to claim 1, which is characterized in that selected in step 1
The watermarking images taken use binary bitmap or Gray-level Watermarking image.
3. a kind of color image hard copy holographic watermark method according to claim 1, which is characterized in that institute in step 2
That states extends watermarking images by way of being conjugated symmetric extension, and carries out DFT processing, obtains the digital hologram of watermarking images
Figure, comprises the following processes:
(1) conjugation symmetric extension extension is carried out to watermarking images M, generates extension watermarking images M1；
(2) extension watermarking images M1 is generated and is schemed as amplitude and carrier image second level dwt transformation high fdrequency component conjugation symmetric extension
As N；
(3) DFT transform is carried out to watermarking images N and obtains watermarking images O；
(4) watermarking images O is normalized, obtains the digital hologram of watermarking images.
4. a kind of color image hard copy holographic watermark method according to claim 1, which is characterized in that institute in step 3
That states is embedded in the digital hologram of watermarking images the R-portion of carrier image RGB color space, forms the carrier comprising watermark
Image includes the following steps:
(1) carrier image pre-processes, and does second level DWT transformation to the R-portion of the RGB color space of carrier image, obtains color point
The respective distribution map of R, G, B are measured, and extracts the wavelet coefficient H of the HL2 layer of color component R；
(2) digital hologram of watermarking images is carried out DWT transformation to extract HL1 wavelet coefficient W, W being watermark to be embedded；
(3) it is embedded in watermark, second level DWT transformation is carried out to carrier image, obtains second level coefficient HL2, LL2, LH2, HH2, second level is small
Wave system number LL2, LH2, HH2 are remained unchanged, and second level wavelet coefficient HL2 and W are combined, using following calculation formula:
Std [H] indicates that the standard deviation of H, a indicate the regulatory factor of embedment strength, as a=std [W]/std [H], phase in formula
When the part HL2 for directly replacing carrier image second level DWT in the DWT transformation extraction part the HL1 W with watermark；For W, H's
Mean value；
(4) second level wavelet coefficient HL2 and other three second level wavelet coefficients LL2, LH2, HH2 after in conjunction with W are combined together
Another mistake DWT transformation, obtains level-one wavelet coefficient LL1；Again by LL1 and other three level-one wavelet coefficient LH1, HL1, HH1 against DWT
Transformation, synthesizes R component with watermarked information, then synthesized by R component with watermarked information, color component G, color component B and included
The carrier image of watermark information.
5. a kind of color image hard copy holographic watermark method according to claim 1, which is characterized in that institute in step 4
The watermark extracting stated specifically comprises the following processes:
(1) it pre-processes, second level DWT transformation is done to the R-portion of the carrier image containing watermark, obtains corresponding second level wavelet coefficient
The coefficient of each layer of LL2, LH2, HH2, HL2 is distributed；
(2) watermark is extracted, extracts HL2 layers of wavelet coefficient, and wavelet coefficient embedment strength factor a is restored to obtain number
Hologram；
(3) restore watermark, DFT transform is carried out to digital hologram, and extract amplitude information, restore watermarking images.
6. a kind of color image hard copy holographic watermark method according to claim 4, which is characterized in that selection is one small
Wave base makes the wavelet coefficient W in wavelet coefficient H and step (2) in step (1) equal in magnitude.
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| CN101520886A (en) * | 2009-02-24 | 2009-09-02 | 上海大学 | Method for watermarking hologram for resisting photo printing-scanning attack and hard copy cutting |
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