KR20110068042A - An watermarking method for digital contents using digital holography - Google Patents

Abstract

PURPOSE: A watermarking method of digital content which uses a digital hologram is provided to satisfy non-visibility without the deformation of a digital content image due to an inserted watermark. CONSTITUTION: A hologram mark generating unit converts a depth image watermark into a digital hologram(S10). A wavelet converting unit filters a content image into four images by a sub band(S20). A hologram mark inserting unit converts one image by sub band into the hologram mark(S30). A comparing unit confirms the insertion of the watermark by comparing an inserted hologram mark with an original hologram mark(S40).

Description

Watermarking method for digital contents using digital holograms {An watermarking method for digital contents using digital holography}

The present invention relates to a watermarking method of digital content using a digital hologram that converts a depth image watermark into a digital hologram to generate a holmark and inserts the holmark as a watermark.

In particular, the present invention relates to a watermarking method of digital content using a digital hologram for watermarking by substituting a holographic mark for one of the subband-specific images generated by two-dimensional discrete wavelet transform (2DDWT).

The present invention also relates to a watermarking method of digital content using a digital hologram for confirming watermarking by comparing a reproduced holographic image with a watermark by directly reproducing the content image with the holmark inserted as a watermark. .

Recently, illegal distribution and manipulation of digital contents by users of various multimedia service models have been prevalent, and forgery / modulation in the field of security application systems using digital video recorders (DVRs) and web cameras, and the intellectual property rights problem. Is highlighted. Copyright protection technology is required to prevent such illegal copying and manipulation and effectively protect ownership. Digital watermarking technology is a technology that can provide a basis for protecting such intellectual property rights and claiming copyright. Much research and application is being done.

The watermark used for digital watermarking uses a unique logo (video data) or data combination (binary data) that can prove the copyright of the content owner. These watermarks are likely to be altered or deleted by malicious or non-malicious attacks from outside after insertion. To solve this problem, techniques for embedding a watermark in the frequency domain or giving robustness to the watermark itself are being studied.

That is, with the development of digital watermarking technology, the watermark application area has been moved from the spatial domain to the frequency domain, and the technique in the frequency domain is more resistant to attack than the method applied in the spatial domain. However, there is a disadvantage in that the watermark insertion position cannot be accurately selected due to the frequency characteristics.

Watermarking in the frequency domain inserts a watermark by changing the frequency coefficient. Ruanaidh inserts a watermark into the phase component using a discrete fourier transform (DFT), and Cox and Barni use a discrete cosine transform (DCT). We proposed a method of inserting a watermark by selecting important coefficients in the frequency domain. Seo proposed a method of inserting a watermark using 2DDWT while removing the blocking effect that occurs in DCT.

Watermarking of watermarking techniques performed in such a frequency domain requires frequency conversion of the watermarked natural image. The watermarking technique using the optical system proposed by Cheng has a disadvantage in that the quality of the watermarked image is greatly reduced, which does not satisfy the invisibility and is very vulnerable to attacks such as burring.

Disclosure of Invention An object of the present invention is to solve the problems described above, and to prove the robustness of the digital watermarking algorithm, the digital hologram has been proved to be robust against external attacks such as compression, noise addition, and geometric deformation. To provide a watermarking method of digital content using a digital hologram using a watermark.

In particular, it is an object of the present invention to provide a watermarking method of digital content using a digital hologram that converts a depth image watermark into a digital hologram in an image of the digital content to generate a holmark and insert the holmark as a watermark. .

In addition, an object of the present invention is a watermarking method of digital content using a digital hologram for watermarking by substituting a holmark with one having the most similar energy distribution among the subband images generated by two-dimensional discrete wavelet transform (2DDWT). To provide.

It is still another object of the present invention to provide a watermarking method of digital content using a digital hologram that checks watermarking by comparing a reproduced hologram with a watermark by directly reproducing a content image having a holmark embedded therein as a watermark. To provide.

That is, the object of the present invention is to extract the watermark by a hybrid method using an electronic watermark extraction method and an optical system, and in particular, to use a watermark on the actual space using an electronic extraction method and an optical system based on a PC. To provide a watermarking method of digital content using a digital hologram in parallel with a method of playing a digital holographic 3D reconstructed image.

In order to achieve the above object, the present invention relates to a watermarking method of digital content using a digital hologram that inserts a depth image watermark into an image of digital content. Generating a; (b) decomposing the content image into at least four subband images by two-dimensional discrete wavelet transform (2DDWT); And (c) generating a holmark embedding image by substituting one subband image (hereinafter referred to as a substituting image) among the subband images by the holmark.

In the watermarking method of digital content using a digital hologram, in step (a), the holmark is generated from the depth image watermark according to Equation 1 below.

[Equation 1]

Where α and j are the holmark and depth image, k is the wave number of reference, and 2π / λ is defined, A _j is the intensity of the original object, and N is the depth information image. Where p is the pixel size of the display device, x _α and y _α are the coordinates of the holmark, and x _j , y _j , and z _j are the coordinates of the depth information image.

 In addition, the present invention provides a watermarking method of digital content using a digital hologram, in the step (c), it is characterized in that to replace the sub-band image with the most similar to the holmark and the image energy distribution of the sub-band image. .

In the watermarking method of digital content using a digital hologram, in the step (c), the HH subband image among the subband images may be replaced with the holmark.

In another aspect, the present invention provides a watermarking method of digital content using a digital hologram, wherein the method comprises: (d) filtering a holographic embedded image into sub-band images by a 2D discrete wavelet transform (2DDWT), and displaying the holmark. And extracting the watermark to check the watermarking.

In addition, the present invention provides a watermarking method of digital content using a digital hologram, the method comprising the steps of (d) reproducing a holographic embedded image by a holographic optical system to reproduce the reproduced holographic image and depth image watermark; And comparing the watermarking with watermarking.

The present invention also relates to a computer-readable recording medium having recorded thereon a program for performing a watermarking method of digital content using the digital hologram.

As described above, according to the watermarking method of the digital content using the digital hologram according to the present invention, one of the subband images generated by the two-dimensional discrete wavelet transform (2DDWT) has the most similar energy distribution (or coefficient distribution) characteristics. By substituting with a holmark, it satisfies the invisibility without altering the digital content image due to the inserted watermark (or the holmark), and has the robustness to check the watermark even when an illegally used attack by converting the digital content image. Effect is obtained.

In particular, the invisibility test results showed that the inserted holmark satisfies sufficient invisibility. Also, to verify the robustness, various attacks such as Gaussian noise addition, JPEG compression, JPEG2000 compression, cropping, sharpening, illusion, rotation, etc. were executed. In addition, satisfactory results were obtained from attacks using optical devices such as digital cameras.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

In addition, in describing this invention, the same code | symbol is attached | subjected and the repeated description is abbreviate | omitted.

First, a configuration of an entire system for implementing a watermarking method of digital content using a digital hologram according to the present invention will be described with reference to FIG. 1.

As shown in FIG. 1, the entire system for implementing the present invention includes a watermarking system 30 for inserting a watermark into the content image 70, and a watermark for checking the watermark inserted into the content image 70. It consists of a confirmation system 40.

As an example, the watermarking system 30 or the watermark checking system 40 may be implemented as a software tool installed and executed in the computer terminal 10. Computer terminals 11 and 12 are conventional computing terminals. Examples of computer terminals include a PC, a notebook computer, a PDA, a server, and the like, and the detailed description thereof will be omitted since the configuration and operation principle thereof are well-known techniques commonly used in the art.

As another embodiment, the watermarking system 30 or the watermark checking system 40 may be made of one control circuit and manufactured by a chip or the like.

The watermarking system 30 converts the depth image watermark into a digital hologram to generate a holmark (or one holmark), and inserts the generated holmark into the content image 70 for distribution. The content image with the holmark embedded therein (hereinafter referred to as the holmark embedded image) is distributed online or offline.

The watermark verification system 40 reproduces the holmark insertion image 80 as a holographic reconstruction image through the holographic optical system 50, extracts the holmark, and compares the holmark with the extracted holmark to check the copyright. .

In this case, when the watermark checking system 40 displays the holmark insertion image 80 on a spatial light modulator 51 connected to the computer terminal 12, the watermark checking system 40 displays the holmark optical system 50. By doing so, the holmark inserted into the holmark embedded image 80 is reproduced as a holographic reconstructed image.

Next, the configuration of the watermarking system 30 and the watermark checking system 40 according to an embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 2, the watermarking system 30 according to an exemplary embodiment of the present invention includes a holmark generating unit 31, a wavelet converting unit 32, and a holmark inserting unit 33.

The holmark generation unit 31 converts the depth image watermark 60 into a digital hologram to generate a holmark 61 (or one holmark).

As shown in FIG. 3A, the depth image watermark 60 is an image composed of depth information. 3A is a depth image of a size of 200 × 200 and a depth expressed in grayscale.

As shown in FIG. 3B, the holmark generator 31 converts the depth image watermark 60 into a digital hologram. At this time, the converted digital hologram will be referred to as "HoloMark". That is, the holmark has the meaning of a watermark converted into a digital hologram. Holomark also acts as a watermark.

For example, FIG. 3B is a hologram 61 generated by Fresnel transformation, which is a digital hologram obtained by binary numbers of 256 X 256 size.

At this time, the holmark 61 is generated using the following [Equation 1]. This equation approximates the principle of hologram generation and then obtains digital holograms through mathematical operations.

[Equation 1]

Where α and j are the holmark and depth image, k is the wave number of reference, and 2π / λ is defined, A _j is the intensity of the original object, and N is the depth information image. Where p is the pixel size of the display device, x _α and y _α are the coordinates of the holmark, and x _j , y _j , and z _j are the coordinates of the depth information image. HM _α is the hologram value at x _α and y _α .

The wavelet transform unit 32 decomposes the content image 70 into at least four subband images 71 by two-dimensional discrete wavelet transform 2DDWT.

4 is a diagram illustrating an example of discrete wavelet transform. Here, L (x) represents a low pass filtering (LPF) function, and H (x) represents a high pass filtering (HPF) function.

The low pass filtering L1 (x) and the high pass filtering H1 (x) are performed in the horizontal direction on the content image 70. Subsequently, a first low pass filtered image L and a first high pass filtered image H in which the image processed by down sampling is halved are obtained.

In addition, the low pass filtering L2 (x) and the high pass filtering H2 (x) are performed in the vertical direction on the first low pass filtering image L and the first high pass filtering image H, respectively. Subsequently, second and second low pass filtered images LL and HL discarded images processed through down sampling and second high pass filtered images LH and HH are obtained. That is, the subband image 71 for four frequency bands of LL, LH, HL, and HH is obtained.

The holmark inserting unit 33 generates a holmark embedding image 80 by replacing one subband image (hereinafter referred to as a substituting image) among the subband images 71 with the holmark 61.

As shown in FIG. 5, after replacing the HH subband image among the four subband images 71 with the holmark 61, the holmark insertion image 80 is transformed through inverse discrete wavelet transformation. Acquire.

That is, up-sampling is performed in the vertical direction with respect to the secondary-filtered image that is the image for the four frequency bands of the subband image 71 of the LL, LH, and HL and the holomark 61. The image is doubled by padding the pixels of the second-filtered image. In addition, the first-order filtered images L and H are obtained by performing inverse low pass filtering L3 (x) and inverse high pass filtering H3 (x). The image is doubled by performing upsampling in the horizontal direction on the first filtered image L and H and padding the pixels of the first filtered image. The inverse low pass filtering L4 (x) and the inverse high pass filtering H4 (x) are performed to obtain the holmark embedded image 80.

Preferably, the holmark insertion unit 33 replaces the subband image having the most similar image energy distribution with the holmark 61 among the subband images 71.

That is, the coefficient distribution (or energy distribution) characteristic of the image 71 for each subband is determined after the one-level two-dimensional discrete wavelet transform (2DDWT) of the content image 70 to select the insertion position of the holmark 61. After analysis, the holmark 61 is inserted.

As shown in FIG. 6, when analyzing coefficient distribution characteristics of the holmark 61 generated using Equation 1, the image of HDD subbands among the 2DDWT subbands 71 is very similar. 6A is a coefficient distribution of the holomark, and FIG. 6B is a distribution of images for each subband. Accordingly, the present invention selects the HH subband image of the 2DDWT image that can satisfy the invisibility of watermarking as the watermark insertion position.

A visual effect (invisibility) according to the holomark insertion according to an embodiment of the present invention will be described in more detail with reference to FIG. 7. FIG. 7 shows the results of replacing and inserting the holmark 61 in the image of each subband (LL1, HL1, LH1, HH1) after 1-level 2DDWT. That is, FIG. 7 shows images reversed by 2DDWT after the holmark 61 is inserted.

LL1 of FIG. 7 is a holmark embedded image 80 obtained by replacing the LL subband-specific image with the holmark 61 in FIG. 5. The remaining LH1, HL1, and HH1 of FIG. 7 are the holmark embedded images 80 obtained by replacing the LH, HL, and HH subband images with the holmark 61, respectively.

As shown in FIG. 7, the holmark 61 inserted into the LL1, HL1, and LH1 subband images is visually recognized in the spatial domain and affects the image quality, but the watermarking result performed in the HH1 subband is not. It can be confirmed that the visibility is sufficiently satisfied.

2 and 8, a watermarking confirmation system 40 according to an embodiment of the present invention will be described. As shown in FIG. 2, the watermarking confirmation system 40 may include a wavelet converting unit 41 or a holographic reproducing unit 32, and may further include a comparing unit 33.

As shown in FIG. 8A, as a first embodiment, the watermarking verification system 40 filters the holmark embedded image 80 into sub-band images by two-dimensional discrete wavelet transform (2DDWT) to insert the inserted holmark. Extract (81) to confirm watermarking.

That is, as shown in FIG. 5, the holmark embedded image 80 performs inverse discrete wavelet transform on the images of four frequency bands of the LL, LH, and HL subband images 71 and the holmark 61. Since it is obtained through, when the discrete wavelet transform the holmark embedded image 80 is again converted, the holmark 81 inserted in the HH subband can be extracted.

Accordingly, the watermarking confirmation system 40 performs discrete wavelet transform of the holmark embedding image 80 through the wavelet transform unit 41 to extract the holmark 81 inserted in the HH subband.

The comparison unit 33 compares the inserted holmark 81 and the original holmark 61 to confirm whether the watermark is inserted.

As shown in FIG. 8B, as a second embodiment, the watermarking confirmation system 40 filters the holmark embedding image 80 into sub-band images by two-dimensional discrete wavelet transform (2DDWT) to display the holmark 81. Extract and reproduce the extracted holmark 81 as a holographic image to check watermarking.

In other words, the inserted holmark 81 is extracted in the same manner as in the first embodiment. Thereafter, the holographic reproducing unit 42 reproduces the extracted holmark 81 using the holographic optical system 50. The comparison unit 43 compares the reproduced holographic image 82 with the depth image watermark 60 to determine whether to insert the watermark. The holographic optical system 50 will now be described in detail.

As shown in FIG. 8C, as a third embodiment, the watermarking confirmation system 40 reproduces the holmark embedding image 80 by the holographic optical system 50, and reproduces the reproduced holographic image 82. The watermarking is checked by comparing with the depth image watermark 60. That is, in the third embodiment, the holographic reproduction unit 42 directly holographically reproduces the holmark embedded image 80 without executing the 2D discrete wavelet transform (2DDWT).

As shown in FIG. 9, the holographic optical system 50 displays an image 80 in which a holmark is inserted on a spatial light modulator 51 connected to a PC, and then uses an optical system. When the laser light (reference wave) is irradiated, the holographic reconstructed image is reproduced in space. In the example of FIG. 3, the holographic optical system 50 reproduces the holmark 61 (FIG. 3B) generated from the watermark (FIG. 3A) by the holographic optical system 50, resulting in the same result as FIG. 3C. Outputs

10 is an image of each of the holmark embedded images 80 of FIG. 7 reproduced by the holographic optical system 50 according to the third embodiment. That is, FIG. 10 is a holographic image 82 (or holographic 3D objects) reconstructed in real space using FIG. 9 holographic optical system 50 of FIG. In particular, the images of FIG. 10 are images obtained by adjusting only the resolution after capturing only an object part for visual quality comparison.

Looking at the images of FIG. 10 reconstructed by the holographic optical system 50, the positions of the reconstructed holographic images 82 vary depending on the frequency characteristics of each subband, but visually recognizable (the copyright can be claimed). It can be seen. The experimental results show that the best method is to select the HH1 subband of the wavelet region as the holmark insertion position. The holomark extracted in the reverse order of the electronic watermarking insertion process is 100% extracted in the absence of external malicious / non-malicious attacks, and thus will not be described separately.

The third embodiment has the advantage that it is not necessary to perform a two-dimensional discrete wavelet transform (2DDWT) that requires a lot of calculation.

As described above, the reproduced holographic reconstructed image and the holomark extracted in the reverse order of the electronic watermarking insertion process are the basis for claiming the copyright of the original image.

Next, a watermarking method of digital content using a digital hologram according to the present invention will be described with reference to FIG.

As shown in Figure 11, the watermarking method of digital content according to an embodiment of the present invention (a) step of converting the depth image watermark to a digital hologram to generate a holmark (or one holmark) (S10) ; (b) filtering the content image into at least four subband images by two-dimensional discrete wavelet transform (2DDWT) (S10); And (c) generating a holmark embedding image by substituting one subband image (hereinafter referred to as a substituting image) among the subband images by the holmark (S10). In addition, (d) the holmark insertion image is filtered by sub-band images by 2D discrete wavelet transform (2DDWT) to extract the holmark and compare the extracted holmark with the original holmark, or holo insert the holmark image. The method may further include a step (S10) of reproducing by the graphic optical system and comparing the reproduced holographic image and the depth image watermark (S10).

Particularly, in the step (a), the holmark is generated from the depth image watermark according to [Equation 1].

Further, in the step (c), the sub-band image having the most similar distribution of the holmark and the image energy among the sub-band images is replaced with an HH sub-band image.

In the description of the watermarking method of the digital content using the digital hologram, the description of the watermarking system and the watermark verification system described above will be referred to.

Next, the toughness of the holomark according to the present invention will be described with reference to FIG. 12 is a reconstruction result after subsampling a digital hologram, and includes reconstruction results of (a) the original image, (b) one pixel unit, (c) 64 × 64 block unit, and (c) 128 × 128 block unit, respectively. admit.

In general, watermarks used for digital watermarking use unique logos (video data) or data combinations (binary data) that can prove the copyright of the content owner. These watermarks are likely to be altered or deleted by malicious or non-malicious attacks from outside after insertion. In order to solve this problem, a watermark must be inserted in the frequency domain or toughness must be given to the watermark itself. In the present invention, in order to give toughness to the watermark itself to be inserted, a digital hologram, that is, a holmark that exhibits very strong characteristics such as geometric deformation, cropping and noise, is used as a watermark.

In the case of the holomark according to the present invention, it is very robust against attacks such as compression, noise addition, cutting, and rotation of the entire image, but the sub-sampling of the pixel unit results in the original image or the original object. This results in little loss of information. This is shown in Figure 12b.

However, as shown in FIGS. 12C and 12D, if the subsampling is performed in units of blocks and then takes the same spatial resolution as that of the original image, a hazed image having a high frequency removed from the original image is generated. That is, the larger the subsampling block unit, the more reconstructed the image similar to the original object. This shows that each local area of the holomark has all the information about the entire object, and the restoration result is superior as the size of the selected area is increased.

12B, 12C, and 12D all subsample the same amount of data, but it can be seen that the restoration results are completely different. From these results, it can be seen that the adjacent pixels constituting the digital hologram (holmark) have little correlation and each contain independent information. Therefore, the present invention replaces the holmark with the entire 2DDWT frequency domain in consideration of the characteristics of the holmark without using the conventional general watermarking technique of inserting the watermark into the entire image in the spatial domain or the frequency domain. Watermarking technique is used.

On the other hand, in the case of digital hologram, that is, the holmark, the value of each pixel is greatly changed according to factors such as original object, restoration distance, type of light source, and pixel pitch of spatial light modulator (SLM). It is a very suitable data as a watermark.

Next, a comparison result of the watermarking method of the digital content using the digital hologram according to the present invention and the conventional watermarking method will be described with reference to FIG.

FIG. 13 compares the experimental results of the watermarking technique using the optical system proposed by Cheng with the results of the proposed technique. In the case of watermarking using the optical system proposed by Cheng, as shown in FIG. 13A, the watermarked image has a deterioration in image quality where a large number of high frequency components exist and the contrast value of the entire image is changed. In addition, it can be seen that the resolution of the holographic reconstructed image restored by the optical system is considerably lowered.

Figure 13b shows the experimental results of the technique proposed in the present invention. The left image of FIG. 13B is a watermarked image, and the right image is a holographic reconstruction image of a watermarked image reconstructed by an optical system. Comparing FIG. 13A and FIG. 13B, it can be seen that the technique proposed in the present invention is significantly improved compared to the previous technique.

Next, the robustness verification for various attacks of the present invention will be described with reference to FIGS. 14 and 15.

In order to verify the robustness of the proposed watermarking algorithm, Gaussian noise addition, cropping, sharpening, dreaming, and geometric deformation attack were performed on the watermarked images. Adobe's Photoshop and StirMark 4.0 were combined for various attacks. In order to verify the robustness of the proposed watermarking technique, the numerical comparison of the error marks of the holmarks extracted by electronic techniques and the visual representation of holographic 3D reconstructed images using an optical system (or holographic optical system) The measurement of image quality deterioration was performed in parallel. The extracted holmark was reproduced as a holographic reconstructed image through PC simulation and the error rate of the original holographic reconstruction with the holographic reconstructed image was measured.

In general, the robustness test results are represented by an error rate or NC (normalized correlation) value of the original watermark of the detected watermark. In the present invention, it is represented by an error rate as shown in Equation 2 below.

[Equation 2]

Here, W (i) and Wex (i) mean the i-th original watermark bit and the extracted watermark bit, and M X N represents the total number of bits of the watermark.

Figure 14 shows the error rates for various attacks. Experimental results showed that the JPEG compression attack resulted in an error from JPEG Quality 2, and the JP2K (JPEG2000) compression attack produced an error at a compression ratio of 50: 1. The Gaussian noise attack showed a relatively high error rate. In addition, geometrical attacks, such as cutting and rotation crops, also showed a fairly high error rate. However, it is unlikely that Gaussian noise will be added more than 10% in real images, and it is rare to set JPEG Quality to 2 or compress the image with a compression ratio of 50: 1 or higher. The results are excellent.

Vulnerability to geometrical attacks can be compensated by extraction techniques using the optical system as shown in FIG. 15 is a holographic reconstructed image reconstructed using an optical system, each of (a) original (no attack), JP2K compression; (b) 50: 1, (c) 100: 1, (d) Gaussian noise added (15%), (e) cut (25%), and (f) cut after rotation (회전 2­).

Visually recognizable holographic reconstructed images were reproduced even at a compression ratio of 100: 1, and the error rate was higher than 20% in 15% Gaussian noise addition, cutting, and cutting after rotation, but as shown in FIGS. 15D to 15F. The reconstructed image is visually recognizable. Therefore, it can be an excellent copyright protection method when the extraction method using the electronic holomark extraction technique and the optical system are combined.

Next, the result of the illegal image acquisition attack using the optical device of the present invention will be described with reference to FIG. Fig. 16 shows images taken using a digital camera and reconstructed images reproduced by an optical system. Fig. 16A shows a general image, Fig. 16B shows a portion of an image, and Fig. 16C shows an image when the camera angle is tilted to the left. to be.

Recently, the use of video acquisition devices such as mobile phones, digital cameras, and camcorders is becoming more common, and illegal recording of content in theaters, performance halls, exhibitions, and the like is distributed and shared over the Internet, which seriously infringes the copyright of the content owner. have.

The watermarking algorithm using the holomark proposed in the present invention is watermarked using a watermarking algorithm proposed for natural video to measure the robustness against image capture attack using optical devices such as scanners, camcorders, digital cameras, etc. The attack was performed using a digital camera to capture the image. The photographed image reproduced the holographic reconstructed image using an optical system.

The results are shown in FIG. FIG. 16A is an image restored by the optical system after selecting only a valid area in the entire captured image (left) and adjusting the resolution to SLM, FIG. 16B is an image restored by adjusting only the resolution of the entire captured image, and FIG. 16c is a reconstructed image after selecting only a valid area of the entire captured image and rotating it to the right. Looking at the reconstructed image, it can be seen that all three experimental results are visually recognizable.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example, Of course, a various change is possible in the range which does not deviate from the summary.

The present invention is applicable to the development of a watermarking system for digital content that converts and inserts a depth image watermark into a digital hologram in an image of the digital content.

1 is a diagram showing the configuration of an entire system for implementing a watermarking method of digital content using a digital hologram according to the present invention.

2 is a diagram illustrating the configuration of a watermarking system and a watermark checking system according to an embodiment of the present invention.

3 is a diagram illustrating a depth image watermark, a holmark, and a reconstructed holographic image according to an embodiment of the present invention.

4 illustrates a two-dimensional discrete wavelet transform according to an embodiment of the present invention.

5 illustrates an inverse two-dimensional discrete wavelet transform according to an embodiment of the present invention.

6 is a diagram illustrating energy distribution of an image of a holmark and subbands according to an embodiment of the present invention.

FIG. 7 illustrates a result of visual influence (invisibility) according to the insertion of a holomark in each subband image according to an embodiment of the present invention.

8 is a block diagram showing the configuration of three embodiments of a watermark checking system according to the present invention.

9 is a block diagram of a configuration of a holographic optical system according to an embodiment of the present invention.

FIG. 10 illustrates an image of a holmark embedded image reproduced by a holographic optical system according to an exemplary embodiment of the present invention.

11 is a flowchart illustrating a watermarking method of digital content using a digital hologram according to the present invention.

12 is a view for explaining the toughness of the holomark according to the present invention.

FIG. 13 is a diagram illustrating a comparison result between a watermarking method of digital content using a digital hologram and a conventional watermarking method according to the present invention.

14 is a table showing the results of attacking the embedded holmark image according to the present invention.

15 is a diagram illustrating a holographic reconstructed image reconstructed using an optical system (holographic optical system) according to the present invention.

16 is a diagram illustrating a result of an illegal image acquisition attack using the optical device of the present invention.

Explanation of symbols on the main parts of the drawings

11,12: computer terminal 20: network

30: holomarking system 31: holomark generating unit

32: wavelet converter 33: holmark insertion unit

40: Holo mark confirmation system 41: Wavelet conversion unit

42: holographic playback unit 43: comparison unit

50: holographic optical system 51: spatial light modulator (SLM)

60: depth image watermark 61: holomark

70: content footage 71: video by sub-station

80: embedded holmark image 81: subband image to be replaced

82: holographic image

Claims (7)

In the watermarking method of digital content using a digital hologram inserting a depth image watermark into an image of digital content, (a) generating a holmark by converting the depth image watermark into a digital hologram; (b) filtering the content image into at least four subband images by two-dimensional discrete wavelet transform (2DDWT); And (c) substituting one subband image (hereinafter referred to as a substitution target image) among the subband images by the holmark to generate a holmark embedding image, wherein the digital content is watermarked using a digital hologram. . The method of claim 1, wherein in step (a), A watermarking method of digital content using a digital hologram, characterized in that for generating the holmark from the depth image watermark according to [Equation 1]. [Equation 1]

Where α and j are the holmark and depth image, k is the wave number of reference, and 2π / λ is defined, A _j is the intensity of the original object, and N is the depth information image. Where p is the pixel size of the display device, x _α and y _α are the coordinates of the holmark, and x _j , y _j , and z _j are the coordinates of the depth information image. The method of claim 1, wherein in step (c), The watermarking method of digital content using a digital hologram, characterized in that for replacing the sub-band image with the most similar to the holmark and the image energy distribution of the sub-band image. The method of claim 2, wherein in step (c), The method of watermarking digital content using a digital hologram, characterized in that for replacing the HH subband image of the subband image with the holmark. The method of claim 1, wherein (d) filtering the holmark-inserted image into sub-band images by 2D discrete wavelet transform (2DDWT), and extracting the holmark to confirm the watermarking. How to watermark content. The method of claim 1, wherein (d) reproducing the holmarked image by the holographic optical system, and comparing the reproduced holographic image and the depth image watermark to confirm the watermarking. Watermarking method. A computer-readable recording medium having recorded thereon a program for performing a watermarking method of digital content using the digital hologram according to any one of claims 1 to 6.

Images