CN1325577A - Watermarking of digital images using wavelet and discrete cosine tranforms - Google Patents

Abstract

The present invention relates to a method for embedding a watermark into a black and white or color digital image[D(x)]. Basically the inventive method comprises the steps of transforming the digital image using a wavelet transform[WC(y)], transforming a watermark using discrete cosine transform (DCT), integrating the wavelet-transformed digital image with the DCT-transformed watermark[DW(x) + WC(y)]to insert the watermark into the image, and generating the watermarked image using inverse wavelet transform[D(x)']. For color images, RGB mode is converted into YIQ mode using a conversion matrix and the wavelet transform is applied to the Y-, I-, Q- values. This inventive digital watermarking of a color image is found to be highly robust against loss compression and other image processing operations, compared to conventionally known methods which are known to be unsuitable for watermarking color images.

Description

With small echo and discrete cosine transform digital picture is added watermark

The application is based on two parts of korean patent applications, these two parts of applications are to be submitted in Korea S Department of Intellectual Property on August 10th, 1998 by identical inventor, wherein, a application is a korean patent application sequence number 37273, be entitled as " digital picture being made to add watermark processing " with wavelet transformation and discrete cosine transform, another part application is a korean patent application sequence number 37274, is entitled as " coloured image being made to add digital watermark processing with wavelet transformation and discrete cosine transform ".

Technical field

The present invention relates to the method that digital picture is added watermark on the whole, specifically, the present invention relates to wavelet transformation (WT) and discrete cosine transform (DCT) thus with watermark imbed digital picture avoid basically such as compression, filtration, montage, again convergent-divergent, resample, rotate and other operation the image processing operations process in damage the method for watermark.The present invention is applicable to black and white image and coloured image simultaneously.

Background of invention

The appearance of ICT (information and communication technology) is just making the form of storage change over the quality digital form that is easy to be for further processing from analog format.Particularly in computer graphics, digital library, e-magazine and the Cyberspace communications field, the importance of digital information increases.In multiple digital information, text and information for still picture have circulation widely by the internet in the virtual market, and the internet can release news easily and widely in the whole world.Along with the surge of Voice ﹠ Video transmission medium, just pressing index speed by the Voice ﹠ Video information of Internet transmission increases.

But, have with snap information and issue and transmit relevant problem.One of problem is to copy without permission with illegal distribution to have the situation of the digital material of copyright to increase sharply.Multimedia messages by text, image, video and sound can easily carry out massive duplication and make this problem more complicated by the mode that accurately copies.

By copy in the Virtual Space and issue digital information and piracy of intellectual property rights increases just rapidly.Developing the kinds of protect measure, be not subjected to unwarranted copy and issue with the intellectual property of protecting the owner.The safeguard measure of developing at present comprises encryption, digital watermarking and system safety.The present invention relates to digital picture is added watermark.

It is a kind of by extraneous information being imbedded the method so that information is protected in the raw information that will be protected adding watermark (or numeral mirror name).Watermark can be divided into visible watermark and invisible watermark (see J.J.K Ruanaidh in 1996, " digital picture is added watermark so that carry out copyright protection " of F.M.Boland and 0.Sinnen, EVA).

Visible watermark increases copyright mark and information to raw information.It is illegal removing this mark, and copy also is illegal under the situation of permitting without the author.But the All rights are reserved mark is difficult to prevent infringement and illegal copies with preventing to illegally copy.Be designed to indicate proprietorial invisible watermark can prevent third party's watermark of under the situation of not damaging raw information, illegally erasing, still, in the common available formed information of watermarking method, have the problem of image fault with known prior art.So,, follow-on watermarking method is had very strong demand in order to overcome above-mentioned and relevant issues.

Adding watermark (or digital signature) is a kind of being used for to come mark ownership and sign the goods, materials and equipments that copyright is arranged to be made the method for unauthorised copies and issue by copyright mark, sign or trade mark.Adding watermark is accompanied by bore hole sightless " mark " is inserted on the information of seeking to protect.Advanced extensive studies already in many in the world industrialized countries, so that improved watermarking method is provided.Because of underlying cause has been strengthened this research.Along with emerging information technology, the multiple media such as the transmission of newspaper, magazine, library, EMuseum, video request program, Audio on Demand, MP3, website, TV, digital broadcasting and official document spare checking altogether, credit card inspection affairs, finance and securities information has been digitized day by day.Digital technology has caused revolution, and is strengthened by internet, internet TV, digital YU etc.

At present comprise space law, frequency domain method and spread spectrum method for adding the technology that watermark develops.Space law has the advantage that can increase watermark at an easy rate, but such shortcoming is arranged promptly: add the image of watermark or information and image this is easy to distortion and (sees G.C.Langelaar, 1998 " based on the multi-medium data Copy Protection of mark-on mirror technology " of J.C.A.Van Der Lubbe and J.Biemond when carrying out lossy compression method and filtering; 1998 " adding digital watermark " of H.Berghel and L.O ' GorMan; Aura T., 1998 " the actual invisibility in the digital communication "; O, Bryndonckx, 1998 " being used for digital picture is added the space law of copyright mark mirror " of J.-J.Quisquater and B.Marcq).

Frequency domain method can convert the digital data into the analog signal of frequency component and use the multiple converter technique such as DCT, FFT or wavelet transformation to insert watermark.Although make on the whole data that the watermark that forms with frequency domain method is difficult to wipe because watermark is distributed in, but the problem that exists picture distortion along with the difference of coefficient value (is seen Peticolas, F.A.P., " to the infringement of copyright mark system " in 1998 of R.J.Anderson and M.G.Kuhn; Cox.I.J, J.Kilian, 1996 " being used for the security extension spectrum watermark of image, Voice ﹠ Video " of T.Legithton and T.Shamoon, this article is stated from image processing international conference procceedings ICIP ' 96 the 3rd volume 243-246 page or leaf; Wolfgang, 1996 " digital picture is added watermark " of R.B. and E.J.Delp,, this article is stated from image processing international conference procceedingss in 1996 the 3rd volume 219-222 page or leaf that Switzerland Lausanne publishes; M.Ejima, " based on the digital watermarking of double small wave conversion and the robustness when the image compression thereof " was stated from ITC-CSSSS ' the 98 procceedings 125-128 pages or leaves that Korea S Sokcho publishes A.Miyazaki and T.Saito 1998).

The spread spectrum method is all the fashion in recent years.According to the spread spectrum method, in DCT (discrete cosine transform) process, watermark is distributed on audio frequency or the digital picture.In this course, spectrum is analyzed, and revised n the pith that significant coefficient is a spectrum.This method partly is similar to frequency domain method.This method has also partly been used CDMA technology by watermark is spread widely.This method has avoided in conversion process promptly that in JPEG, copy, scanning, reducing compressed/extension process watermark is had slightly infringement.But this method can make watermark quality variation in the data compression stage, that is to say, can damage watermark significantly in the data compression stage.

Goal of the invention

The objective of the invention is to overcome the watermarking method of prior art and the above-mentioned defective of system.

Another object of the present invention provide a kind of through improved, be difficult to erase or to remove the watermarking method and the system of watermark.

A further object of the present invention provides a kind of method that adds watermark, it can watermark experience such as image compression, montage, dithering process (dithering), color quantizes again or reducing compressed and expansion etc. image processing the time keep and keep the integrality of watermark.

Another purpose of the present invention provides a kind of watermarking method and system, and wherein, when injecting sightless watermark in the original image, the original image that has added watermark can be kept perfectly.

Also purpose of the present invention provides a kind of method that adds digital watermark, and its compressing data and filtration are reliable.

Another purpose of the present invention provides a kind of coloured image watermarking method and system.

A further object of the present invention provides a kind of method that adds digital watermark, the influence that this method is not handled by the compression such as JPEG or MPEG.

Brief summary of the invention

By being that the present invention of the unique combination of wavelet transformation (WT) and discrete cosine transform (DCT) can reach above and other objects of the present invention to use two kinds of algorithms.According to the present invention, digital picture is imbedded in watermark with wavelet transformation and discrete cosine transform.Have found that method of the present invention can prevent effectively that the watermark that is caused by the image processing operations such as compression, filtration and montage from damaging.

The present invention includes the following step: with wavelet transformation (WT) changed digital image; With discrete cosine transform (DCT) conversion watermark; To combine through the digital picture of wavelet transformation and watermark, so that image is injected in watermark through dct transform; And, generate the image (seeing Fig. 3 and 4) that has added watermark with inverse wavelet transform.

According to the present invention, wavelet transformation and discrete cosine transform can be applied to black and white image and coloured image are added watermark.

The accompanying drawing summary

Fig. 1 shows the flow chart of wavelet transform (WT) and inverse discrete wavelet transform (IWT);

Fig. 2 shows the figure that coefficient distributes;

Fig. 3 shows the flow chart that adds the embodiment of watermark with wavelet transformation and discrete cosine transform (DCT);

Fig. 4 shows the flow chart that adds another embodiment of watermark with WT and DCT;

Fig. 5 shows it is the figure that coloured image is added digital watermark process with WT and DCT;

Fig. 6 shows the flow chart that coloured image is added another embodiment of digital watermark with WT and DCT.

Detailed Description Of The Invention---black and white image

According to the present invention, such watermarking method is provided, this method comprises the following steps: to come the conversion original digital image with wavelet transformation; Come the conversion light and shade watermatk with discrete cosine transform; To combine through the digital picture of wavelet transformation and watermark through dct transform; And, generate the image that is embedded with watermark.

The usual method that adds watermark comprises a PRN (pseudo random number) as watermark, to reduce distortion in images.On the contrary, the present invention embeds a watermark that is made of normal image, so that generate " mark ".Described normal image comprises the symbol such as photo, 2D figure, sign, trade mark, badge, seal and other graphic symbol.

Can be under the hardware environment of using IBM PC Pentium MMX166 and scanner and comprising under the software environment of using the Visual C++ that is easy to buy on the market and realize the present invention.Should be realized that the computer that method of the present invention can be made with a plurality of different vendors is together with using the software with any suitable language compilation to be realized.

In general, when conversion is carried out in watermark, in changing the plane, can not discern original marking.If used the watermark that is made of pulse, then the watermark meeting after the conversion is distributed on the whole changing the plane.Can use Fourier transform, but final plural coefficient is difficult for combining with image value in the changing the plane.

In order to address the above problem, the present invention comes conversion is carried out in watermark from cosine transform (DCT) with diffusing.Although DCT and Fourier transform have similar feature, DCT has such advantage promptly: it only has real number value and does not have the complex values of Fourier transform.The mathematical definition and the principle of discrete cosine transform (DCT) below are described.1, discrete cosine transform (DCT)

With having the DCT of substantial connection that signal or image are encoded with high speed FFT.DCT is widely used for the JPEG compression of standard.Be defined as one dimension DCT as follows:

[equation 1a] $t\left(k\right)=c\left(k\right)\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}s\left(n\right)\cos \frac{\mathrm{\π}(2n+1)k}{2N}$

Wherein, s represents original coefficient, and t represents N transformed value, and c is expressed as follows given coefficient:

[equation 1b] $c\left(0\right)=\sqrt{1/N},c\left(k\right)=\sqrt{1/N}$ 1≤k≤N-1 is as for a square matrix, and DCT is defined as follows with bidimensional: [equation 2a] $t(i,j)=c(i,j)\underset{n=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}s(m,n)\cos \frac{\mathrm{\π}(2m+1)i}{2N}\cos \frac{\mathrm{\π}(2n+1)j}{2N}$ Wherein, N, it is identical that s and t and one-dimensional case are limited, and (i, j) assignment is as follows: [equation 2b] for c $c(0,j)=\frac{1}{N},c(i,0)=\frac{1}{N},c(i,j)=\frac{2}{N},$ I ≠ 0, j ≠ 0DCT can carry out inverse transformation and can limit as follows with regard to a peacekeeping bidimensional: [equation 3a] $s\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}c\left(k\right)t\left(k\right)\cos \frac{\mathrm{\π}(2n+1)k}{2N}$ [equation 3b] $s(m,n)=\underset{i=0}{\overset{N-1}{\mathrm{\Σ}}}\underset{j=0}{\overset{N-1}{\mathrm{\Σ}}}c(i,j)t(i,j)\cos \frac{\mathrm{\π}(2m+1)i}{2N}\cos \frac{\mathrm{\π}(2n+1)j}{2N}$ 2, wavelet transform (DWT)

In the present invention, with digital picture with before the watermark that dct transform is crossed combines, digital picture is made wavelet transformation (WT).Specifically, as shown in Figure 2, use wavelet transform, wavelet transform has been selected one group of wavelet coefficient with regard to convergent-divergent and transposition.Best is to have used the filter assemblies of being convenient to fast wavelet transform shown in Fig. 1 summary.The mathematical definition and the principle of wavelet transformation below are described.

Although as basic function, wavelet transformation (WT) is used as basic function with small echo to Fourier transform with sine and cosine functions.Have two types wavelet transformation: continuous wavelet transformation and discrete wavelet transformation.Continuous wavelet transformation is defined as follows:

[equation 4] $W(s,\mathrm{\τ})={\∫}_{-\∞}^{\∞}f\left(t\right)\mathrm{\ψ}(s,t)\mathrm{dt}$ ∵ s: ratio, τ: translation

Ratio relates to frequency.The little wave energy that low convergent-divergent promptly compresses extracts high fdrequency component, and the small echo of promptly expanding at high proportion can be extracted low frequency component out.

Can not realize continuous wavelet transformation in the practice, because, because of convergent-divergent and position translation different have a unlimited wavelet coefficient.So, shown in Fig. 2 summary,, will produce more effective algorithm if use the wavelet transform of having selected some subclass.But, because wavelet transform has certain computation burden, so, preferably use filter assemblies to realize the high speed wavelet transformation, as shown in Figure 1.This method has been used classical two passage sub-bands coding and progression formula algorithm.

Following the present invention who with wavelet transformation (WT) and discrete cosine transform (DCT) the black and white digital picture is added watermark with reference to the accompanying drawing detailed description.With reference to Fig. 3, Fig. 3 is the illustrative flow of one embodiment of the present of invention, and described watermarking method comprises the following steps:

1) with wavelet transformation (WT) conversion black and white original (target) image D (x);

2) with discrete cosine transform (DCT) conversion light and shade watermatk data W (y);

3) will and combine through the image DW of wavelet transformation (y) through the watermark WC of dct transform (y);

4) generate D (x) ' by synthetic image DW (x) ' being carried out conversion with inverse wavelet transform; And

5) generate the image D (x) ' that is embedded with watermark.

Flow chart among Fig. 4 is shown schematically in a kind of version of watermarking method of the present invention.According to this version, described watermarking method comprises the following steps:

1) black and white original image D (x) is changed;

2) come conversion light and shade watermatk W (y) with DCT;

3) with m level wavelet transform to doing further conversion through the watermark WC of dct transform (y);

4) will and combine through the image DW of wavelet transformation (x) through the watermark WDC of m level wavelet transformation (y); And

5) generate the image D (x) ' that is embedded with watermark.

When obtaining the image D (x) ' that is combined to watermark W (y), with the interval between zooming parameter α adjusting original image D (x) and the watermark W (y).According to the present invention, use following formula for ease of conversion:

[equation 5]

D(x)’ _i=D(x) _i+αW(y) _i

Provide software environment by C code with Visual C++.IBM PC with Pentium class carries out necessary calculating.This particular environment only is illustrative.Performance test to watermarking method of the present invention

Carried out a large amount of tests and compressed, filtered the reliability that other step of resampling and montage and described method experience is compared with JPEG to check the watermark that embeds according to the present invention.Below summarize the example and the result of test.By preceding and extract watermark after (W ') and analyze and judge final result to extracting (W), with the ability of evaluation watermarking method of the present invention with degree of correlation analytic approach.The described degree of correlation is defined as follows:

[equation 6]

Example 1: after image is made lossy compression method, watermark is kept the evaluation of situation

In general, before images, image is compressed, because the not compressed file such as BMP is huge on length.Image compression can be divided into lossy compression method and lossless compress.Although can reduce the quality of original image slightly,, it uses lossy compression method widely because of having high compression rate.JPEG is the representative example of lossy compression method.As mentioned above owing to after image processing, will keep watermark, so if watermarking method after lossy compression method no problem commercial be available.

Therefore, carried out test so that change over 50%, 30%, 20% and 10% strength retention of testing watermark by the Q factor with JPEG.As a result, can clearly identify watermark after the 20%JPEG compression.Watermark after the 10%JPEG compression has point fuzziness slightly, but still can visually be discerned.Example 2: behind the image filtering to the influence of watermark

Because image is generally through filtering eliminating noise, so carried out testing to find out after low-pass filter and intermediate filtered (median filter) image influence to watermark.This test has confirmed successfully to extract watermark out.The degree of correlation of the watermark of extracting out has been shown in the table 1.Table 1

Filter type	Low pass filter	Intermediate filter
			The degree of correlation	??26.83％	??57.84％

The above results demonstrates to filter by low pass filter and intermediate filter does not influence watermark.Example 3: after resampling to the influence of watermark

Carried out test to detect the watermark that generates by algorithm of the present invention after resampling, wherein, resampling can be removed the whole pixel value of image.Table 2 shows the degree of correlation of 2,4 of losses and 5 watermarks that extract afterwards.Table 2

Bit-loss	3	4	5
				The degree of correlation	?18.81％	?37.62％	?72.99％

Above-mentioned test demonstrates and can clearly identify the watermark of extracting out after the resampling.Example 4: behind the montage piece to the influence of watermark

Test that to have how many watermarks to be retained in picture centre be that most critical is partly located so that measure.Cut 192 * 192 image block from entire image, the degree of correlation has been shown in the table 3.Table 3

Crop size	????192×192
		The degree of correlation	????27.89％

The above results has confirmed can successfully extract watermark after the montage piece.Example 5: to adding the evaluation of digital watermarking algorithm

It is the image that has special letter that evaluation adds the employed watermarking images of digital watermarking algorithm.Because image has the form of pulse, so the value behind the dct transform should distribute widely.This is similar with the result who is found in the spread spectrum technology.By generating equally distributed watermark to making inverse wavelet transform through the watermark of dct transform.The present invention shows between watermark and the original image example of 99.85% the degree of correlation and another example that shows 88.04%, thereby has proved successful property of the present invention.

In a word, as mentioned above, the present invention who uses wavelet transformation and DCT to add digital watermark has the excellent effect that keeps watermark after lossy compression method or other image processing.Specifically, after making the JPEG lossy compression method with 50%, 30%, 20% and 10% the Q factor, it is possible extracting watermark.After image experience low-pass filter and intermediate filtered, can extract watermark out.Can also after resampling and montage, extract watermark out.In brief, have found that the present invention uses above-mentioned two kinds of algorithms (being the watermarking method of the combination of WT and DCT) to be better than using separately the known method in the past of DCT or wavelet transformation (WT) in many aspects (particularly aspect keeping watermark and adding the image that adds watermark in the watermark processing).Detailed Description Of The Invention one coloured image adds watermark

Can in the process that coloured image is added watermark, use the present invention who adds digital watermark.Followingly describe wavelet transformation (WT) and the discrete cosine transform of using when coloured image added watermark (DCT) in detail with reference to Fig. 5 and Fig. 6.

With reference to Fig. 5, described method comprises the following steps:

1) color image data under the RGB pattern (RGB (x)) is converted to Y (x) under the YIQ pattern, I (x) and Q (x);

2) with wavelet transformation Y (x) is carried out conversion;

3) with discrete cosine transform (DCT) conversion light and shade watermatk data W (y);

4) will and combine through the coloured image DW of wavelet transformation (x) through the watermark WC of dct transform (y);

5) generate Y (x) ' by synthetic image DW (x) ' being carried out conversion with inverse wavelet transform;

6) the image RGB (x) ' that becomes the image of RGB pattern to generate to be embedded with watermark by image transitions with the YIQ pattern;

With reference to Fig. 6, Fig. 6 shows the another kind of general flowchart that coloured image is added watermark, and described method comprises the following steps:

1) be that RGB (x) converts the Y (x) under the YIQ pattern to the color image data under the RGB pattern, I (x) and Q (x);

2) with I level wavelet transformation Y (x) is carried out conversion;

3) with dct transform light and shade watermatk data W (y);

4) with the watermark of the further conversion of m level wavelet transform through dct transform;

5) will and combine through the coloured image DW of wavelet transformation (x) through the watermark WDC of m level wavelet transformation (y);

6) come the synthetic image DW (x) ' of conversion so that Y (x) ' to be provided with inverse wavelet transform: and

7) the image RGB (x) ' that becomes the image of RGB pattern to generate to be embedded with watermark by image transitions with the YIQ pattern;

When the coloured image RGB (x) ' that has obtained to be combined to, with the interval between zooming parameter α adjusting original image RGB (x) and the watermark W (y) with watermark W (y).The present invention has used following formula for ease of conversion:

[equation 7]

RGB(x)’ _i=RGB(x) _i+αW(y) _i

With regard to from the RGB pattern to the YIQ mode switch, following document discloses transition matrix and inverse conversion matrix.(see Janes Blinn " NTSC: good technology, super color ", " IEEE computer graphical and application ", in March, 1993, pp17-23; James F Blinn " the digital video world ", " IEEE computer graphical and application " in August, 1992 pp106-112).

As mentioned above, provide software environment by C code with Visual C++.IBM PC with Pentium class carries out necessary calculating.This particular environment only is illustrative.

Test the reliability of comparing with JPEG compression, filtration and montage with the watermark that detects embedding according to the present invention.Final result is judged so that compare the ability of watermark with degree of correlation analytic approach.The described degree of correlation is defined as follows:

[equation 8]

In general, before images, coloured image is compressed, because the not compressed file such as BMP is huge on length.Image compression can be divided into lossy compression method and lossless compress.Although can reduce the quality of original image slightly,, it uses lossy compression method widely because of having high compression rate.JPEG is the representative example of lossy compression method.As mentioned above owing to after image processing, will keep watermark, so if watermarking method after lossy compression method no problem commercial be available.Example 6: after coloured image is made lossy compression method, watermark is kept the evaluation of situation

Carried out test so that change over 50%, 40%, 30% and 20%, 10% and 5% strength retention of testing watermark by the Q factor with JPEG.As a result, can clearly identify up to the watermark after the 5%JPEG compression.

The degree of correlation of the watermark of extracting out from the image that is embedded with watermark with the JPEG compression has been shown in the table 4.Table 4

The Q factor	???50％	???40％	???30％	???20％	???10％	???5％
							The degree of correlation	?63.41％	?45.48％	?51.82％	?62.42％	?61.41％	?62.36％

Because coloured image is generally through filtering eliminating noise, so carried out testing to find out after low pass filter and intermediate filter filtering image influence to watermark.This test has confirmed successfully to extract watermark out.The degree of correlation of the watermark of extracting out has been shown in the table 5.Table 5

Filter type	Low pass filter	Intermediate filter
			The degree of correlation	??19.71％	??1.42％

The above results demonstrates to filter by low pass filter and high pass filter does not influence watermark.This degree of correlation is lower slightly, but this can't cause serious problem when extracting and discern watermark.Example 7: coloured image is being extracted watermark after the RGB mode switch becomes the YIO pattern

Have the multiple color pattern image such as RGB pattern, CMY pattern, YIQ and HIS pattern that is used.Carried out test so that extract watermark and measure the degree of correlation of those coloured images from the RGB mode switch to the YIQ pattern.Described test shows, although compare with common RGB pattern low correlation arranged, but still can clearly identify the watermark of extraction.Example 8: behind the montage piece to the influence of watermark

Test that to have how many watermarks to be retained in the coloured image center be that most critical is partly located so that measure.Cut 192 * 192 image block from entire image, the degree of correlation has been shown in the table 6.Table 6

Crop size	????192×192
		The degree of correlation	????52.82％

The above results has confirmed can successfully extract watermark after the montage piece.Example 9: to the evaluation that adds digital watermarking algorithm under the alphabetical situation is being arranged

Employed watermarking images was a kind of image that has special letter when evaluation added digital watermarking algorithm.Because image has the form of pulse, so the value behind the dct transform should distribute widely.This will cause the result similar with spread spectrum.By generating equally distributed watermark to making inverse wavelet transform through the watermark of dct transform.

In a word, as mentioned above, the present invention who uses wavelet transformation and DCT to add digital watermark has the excellent effect that keeps watermark after lossy compression method or other image processing.Even coloured image after becoming the YIQ pattern, the RGB mode switch also can kept watermark.Specifically, after making the JPEG lossy compression method with 50%, 40%, 30%, 20% and 5% the Q factor, it is possible extracting watermark.After image experience low-pass filter, high-pass filter or image clips, can extract watermark.So, proved that the present invention is applicable to coloured image is added watermark, and this point can not be accomplished with common technology.

Although the present invention has been described with reference to most preferred embodiment,, the present invention is not limited to these embodiment.Present technique personnel should be realized that, can carry out multiple improvement to the structure and the form of the foregoing description under the situation that does not break away from the spirit and scope of the invention that only limits and limit in following claim.

Claims (20)

1, the method that digital picture is added watermark, this method comprises the following steps:

(WT) comes the changed digital image with wavelet transformation;

(DCT) comes the conversion watermark with discrete cosine transform; And

To combine through the watermark of dct transform and image, be embedded with the image of watermark with generation through wavelet transformation.

2, method as claimed in claim 1 is characterized in that, this method comprises the following steps: the image through wavelet transformation is carried out inverse wavelet transform.

3, method as claimed in claim 1 is characterized in that, before combining with image through wavelet transformation with m level wavelet transformation to doing further conversion through the watermark of dct transform.

4, method as claimed in claim 3 is characterized in that, with realizing that the filter assemblies of high speed wavelet transformation carries out said wavelet transformation.

5, method as claimed in claim 1 is characterized in that, with realizing that the filter assemblies of high speed wavelet transformation carries out said wavelet transformation.

6, method as claimed in claim 1 is characterized in that, when obtaining the image that is combined to watermark, regulates interval between original image and the watermark with zooming parameter α.

7, method as claimed in claim 1 is characterized in that, described digital picture and watermark are black and white.

8, a kind of system that is used for digital picture is added watermark, this system comprises:

Be used to provide the device of digital picture and watermark; And

Digital processing system, it comes the changed digital image by using wavelet transformation (WT), uses cosine discrete transform (DCT) to come the conversion watermark, and will combine through the watermark of dct transform and image through wavelet transformation, thereby generates the image that is embedded with watermark.

9, system as claimed in claim 8 is characterized in that, this system comprises and use wavelet transformation (WT) and discrete cosine transform (DCT) to carry out the device that black and white image is added digital watermark that wherein, described watermark is a black and white.

10, system as claimed in claim 9 is characterized in that, this system comprises the device that is used for providing m level wavelet transformation (WT) before being combined to image through wavelet transformation.

11, system as claimed in claim 9 is characterized in that, described system comprises the filter assemblies that is used to the high speed wavelet transformation is provided and inverse wavelet transform is provided.

12, a kind of coloured image is added the method for digital watermark, this method comprises the following steps:

Discrete cosine transform (DCT) is done in watermark;

Chromatic image is made wavelet transformation; And

To combine through the watermark of dct transform and coloured image through wavelet transformation (WT).

As the method for claim 12, it is characterized in that 13, this method comprises the following steps: to convert the coloured image RGB (x) under the RGB pattern under the YIQ pattern Y (x), I (x) and Q (x) with transition matrix.

As the method for claim 13, it is characterized in that 14, this method comprises the following steps:

The Y (x) of image after to conversion carries out conversion with wavelet transformation;

With discrete cosine transform (DCT) watermark W (y) is carried out conversion;

To and combine through the watermark WC of dct transform (y) through the coloured image DW of wavelet transformation (WT) (x);

Generate the Y value Y (x) ' of composograph with inverse wavelet transform; And

By Y (x) ', the inverse transformation of I (x) ' and Q (x) ' generates the image RGB (x) ' that is embedded with watermark under the RGB pattern.

15, as the method for claim 12, it is characterized in that, with combine through the coloured image DW of wavelet transformation (x) before, with m level wavelet transformation to doing further conversion through the watermark WC of dct transform (y).

16, as the method for claim 12, it is characterized in that, with realizing that the filter assemblies of high speed wavelet transformation carries out said wavelet transformation.

17, as the method for claim 12, it is characterized in that, with realizing that the filter assemblies of high speed wavelet transformation carries out said wavelet transformation.

18, a kind of system that is used for coloured image is added digital watermark, this system comprises:

Be used to provide the device of coloured image and light and shade watermatk; And

Digital Data Processing Equipment, it uses wavelet transformation (WT) and discrete cosine transform (DCT) to come coloured image is added digital watermark with light and shade watermatk.

As the system of claim 18, it is characterized in that 19, this system comprises:

Use transition matrix to convert the coloured image RGB (x) of RGB pattern to Y (x), the I (x) of YIQ pattern and the device of Q (x);

The device that the Y (x) of the image after using wavelet transformation to conversion carries out conversion:

The device that uses DCT that light and shade watermatk W (y) is carried out conversion;

Being used for will be through watermark WC of dct transform (y) and the device that combines through the coloured image DW of wavelet transformation (x);

Use inverse wavelet transform to generate the device of the Y value Y (x) ' of composograph; And

Be used for by Y (x) ', the inverse transformation of I (x) ' and Q (x) ' generates the device of the image RGB (x) ' that is embedded with watermark of RGB pattern.

20, a kind of coloured image is added the system of digital watermark, this system comprises:

Use transition matrix to convert the coloured image RGB (x) of RGB pattern to Y (x), the I (x) of YIQ pattern and the device of Q (x);

The device that the Y (x) of the image after using wavelet transformation to conversion carries out conversion;

The device that uses DCT that watermark W (y) is carried out conversion;

Use m level wavelet transformation to make the device of progressive conversion through the watermark WC of dct transform (y);

Being used for will be through watermark WC of dct transform (y) and the device that combines through the coloured image DW of wavelet transformation (x);

Use inverse wavelet transform to generate the device of the Y value Y (x) ' of composograph; And

Be used for by Y (x) ', the inverse transformation of I (x) ' and Q (x) ' generates the device of the image RGB (x) ' that is embedded with watermark of RGB pattern.

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