JP2005236864A - Electronic watermark system and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic watermark system and its method, in which the influences on a source image are approximately equivalent to the conventional examples and data of an embedded electronic watermark can be read from image, even after processing has been performed over a range of magnification power wider than the conventional examples. <P>SOLUTION: An electronic watermark embedding system includes an electronic watermark embedding means for embedding electronic watermarks in a source image and a reduced image of the source image in accordance with their image sizes; an image enlarging means for enlarging the reduced image in which the electronic watermark is embedded, to the image size of the source image to produce an enlarged image; and an image composing means for composing the source image, in which the electronic watermark is embedded, and the enlarged image and outputting a result as an electronic watermarked image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a digital watermark system and method for embedding a digital watermark in an original image and detecting a digital watermark embedded from a copied image.

The digital watermark technique for still images is used to embed the original information of the author in the original image in a state where it is hidden from the user and clarify the location of the copyright.
In the Internet, an image in which a digital watermark is embedded is distributed over a wide range as content.
However, the digital watermark embedded in the image is deformed with respect to the original image when the image is enlarged or reduced, so that the embedded data itself is deleted or detected accurately. Data will be tampered with in an incapable state.

For this reason, the conventional digital watermarking system detects a signal for detecting the magnification embedded in the spatial region or frequency region of the image in the case of a method that does not require the original image when detecting the digital watermark. Then, after converting to the same magnification as the original image (after returning), the digital watermark is detected, or each magnification in enlargement and reduction is searched from the image data to detect the digital watermark (for example, patents) Reference 1).
JP 2001-223882 A

However, in the above-described conventional example, that is, the digital watermark detection method disclosed in Patent Document 1, even if the magnification signal embedded in the frequency domain or the image space domain is detected, the range of the magnification that can be detected is particularly small. In the case of embedding in the image space area with luminance information or the like, the pixels themselves are lost due to the reduction of the image. Therefore, the resistance to the processing of the image is low, and it cannot be practically used.
For example, in Japanese Patent Application Laid-Open No. 2004-228867, when using a method of embedding a digital watermark in a frequency domain, which is more resistant to image processing or the like than a method of embedding a digital watermark in an image space region, The range from 0.5 to 2.0 is shown as the limit of the magnification at which digital watermark information can be read.

Also, in the conventional example, in embedding a digital watermark in the frequency domain, in order to reduce the influence on the original image, the frequency domain insensitive to human vision is often embedded in the middle or high frequency domain. Yes.
Therefore, in both cases of the medium frequency region and the high frequency region, by performing a large reduction of the reduction magnification, the similarity theorem in the Fourier transform not only causes a loss in the embedded magnification signal, but also from the content image. Even if the magnification signal is read and the content can be returned to the same magnification as that of the original image, the data in the low frequency region is also affected, so that the digital watermark data cannot be detected.

From the following equation (1) showing the similarity theorem in Fourier transform, it can be easily explained that it affects the middle and high frequency regions.
Since the image reduction processing is performed when both the coefficients α and β are larger than 1 (1 <α, 1 <β) in the equation (1), the pixel function f (αx, βy) is Fourier-transformed. Thus, F (u / α, ν / β) is obtained, and a loss occurs in the frequency region of 1 / α and 1 / β or more.
That is, if digital watermark data is embedded in the middle and high frequency regions, this data is lost together with the corresponding frequency component of the image.

  The present invention has been made in view of such circumstances, and the effect on the original image is made substantially the same as that of the conventional example, and the embedded electron is processed even after processing in a wide magnification range as compared with the conventional example. An object of the present invention is to provide a digital watermark system and method capable of reading watermark data from an image.

  An electronic watermark embedding system according to the present invention includes an electronic watermark embedding unit that embeds an electronic watermark in accordance with each image size, and a reduced image in which the electronic watermark is embedded. An image enlarging means for enlarging the image size of the original image to generate an enlarged image, and an image synthesizing means for synthesizing the original image and the enlarged image in which the digital watermark is embedded and outputting as an image with the digital watermark. It is characterized by.

The digital watermark embedding system according to the present invention includes reduced image generation means for sequentially reducing an original image at a predetermined ratio and generating a plurality of reduced images having different reduction ratios.
The digital watermark embedding system according to the present invention is characterized in that a weighting coefficient corresponding to an image size is added to information of a digital watermark embedded in an original image and a reduced image.

  The digital watermark detection system of the present invention embeds a digital watermark corresponding to the image size for each of the original image and the reduced image of the original image, and combines the images by returning the reduced image to the original image size. And a digital watermark detection system for detecting an embedded digital watermark from the digital watermarked image generated in this way and the digital watermarked image whose image size has been changed, and the image size of the digital watermarked image is changed And a digital watermark detection unit for detecting a digital watermark from the synthesized digital watermarked image and the size-changed digital watermarked image.

  In the digital watermark detection system of the present invention, when the digital watermark detection means cannot detect the digital watermark, the image size is sequentially changed so that the digital watermark detection means detects the digital watermark at the new image size. It has a control means.

  An electronic watermark embedding method according to the present invention includes an electronic watermark embedding process for embedding an electronic watermark corresponding to each image size, and a reduced image embedded with the electronic watermark, with respect to the original image and the reduced image of the original image. An image enlargement process for enlarging the image size of the original image to generate an enlarged image, and an image composition process for synthesizing the original image embedded with the digital watermark and the enlarged image and outputting the resultant image as a digital watermarked image. It is characterized by.

  The digital watermark detection method of the present invention embeds a digital watermark corresponding to the image size for each of the original image and the reduced image of the original image, and combines the images by returning the reduced image to the original image size. And a digital watermark detection method for detecting an embedded digital watermark from the digital watermarked image generated in this way and the digital watermarked image whose image size has been changed, and the image size of the digital watermarked image is changed An electronic watermark detection process for detecting an electronic watermark from an image size changing process to be performed, a synthesized image with an electronic watermark, and an image with an electronic watermark whose size has been changed, and the electronic watermark detection means cannot detect the electronic watermark Detection control process that sequentially changes the image size and causes the digital watermark detection means to detect the digital watermark at the new image size Characterized in that it has a.

  An electronic watermark embedding program according to the present invention includes an electronic watermark embedding process for embedding an electronic watermark corresponding to each image size, and a reduced image in which the electronic watermark is embedded, with respect to the original image and the reduced image of the original image. An image enlarging process for enlarging the image size of the original image to generate an enlarged image, and an image synthesizing process for synthesizing the original image embedded with the digital watermark and the enlarged image and outputting the resultant image as an image with a digital watermark. This is a program executable by a computer.

  The digital watermark detection program of the present invention embeds a digital watermark corresponding to the image size for each of the original image and the reduced image of the original image, and combines the images by returning the reduced image to the original image size. Is a program for detecting an embedded digital watermark from the digital watermarked image generated in this way and the digital watermarked image whose image size has been changed, and changes the image size of the digital watermarked image Image size changing process, digital watermark detection process for detecting digital watermark from synthesized digital watermarked image and digital watermarked image whose size has been changed, and the digital watermark detection means cannot detect the digital watermark Detecting control that changes the image size sequentially and causes the watermark detection means to detect the watermark at a new image size An executable program by a computer and having a sense.

  As described above, the digital watermark embedding system of the present invention creates a plurality of reduced images with different reduction ratios from the original image, embeds the digital watermark corresponding to each of these image sizes, and then reaches the original image size. It is possible to synthesize and synthesize these images and embed digital watermark data that can correspond to each reduction ratio, the influence on the original image can be almost the same as the conventional example, and the conventional Even after processing in a wide range of magnification compared to the above, it is possible to embed a digital watermark that allows the embedded digital watermark data to be read from the image.

  Further, the digital watermark detection system of the present invention embeds a digital watermark corresponding to the image size in each of the original image and the reduced image of the original image, and returns the reduced image to the image size of the original image. When the image with a digital watermark generated by combining the image and the image with the digital watermark whose image size has been changed is the detection target, the image size of the image with the digital watermark that is the detection target cannot be detected In order to detect the embedded digital watermark for each changed image size in order, the embedded digital watermark corresponding to multiple reduced images with different reduction ratios can be efficiently used. Can be detected.

<Digital watermark embedding system>
Hereinafter, a digital watermark embedding system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram cited for explaining the principle of the digital watermark embedding method of the present invention. Here, the original image (digital image) in which the digital watermark pattern is embedded is set at a predetermined reduction ratio α, for example, α = 1/4 (with a reduction ratio of 1/2 in the vertical and horizontal directions), and the original image is sequentially converted by this reduction ratio. A plurality of reduced images, that is, reduced images a, b, and c are generated by reduction. Here, the reduced image a is 1/4 (α) times the image size (area) of the original image, the reduced image b is 1/16 (α * α) times, and the reduced image c is 1/64 ( α * α * α) times.

For convenience, the image size of the reduced image c is assumed to be an embedding unit for embedding a digital watermark pattern. The limit of the image size of the reduced image is an image size in which the digital watermark pattern can be embedded.
Then, as shown in FIG. 1, the original image and the other reduced images a and b are divided into blocks in the area of the embedding unit, and the original image and the other reduced images a, b and c are embedded in each embedding unit. On the other hand, the same digital watermark pattern is embedded. The digital watermark pattern may be embedded either by converting into a frequency and embedding it or by embedding it in bit information representing pixel luminance information.

The reduced images a, b, and c embedded with the digital watermark are enlarged to the image size of the original image using a predetermined enlargement method, and enlarged images A, B, and C are generated.
The original image embedded with the digital watermark and the enlarged images A, B, and C are combined to generate an image with the digital watermark.
As a result, as shown in FIG. 2, the digital watermark image is embedded with digital watermark patterns at different magnifications. Therefore, even if the original image is reduced, it can be reduced to the image size of the embedding unit. If there is, a digital watermark pattern of the corresponding image size is embedded, and this digital watermark pattern can be detected. On the other hand, if the image enlarged from the original image is reduced to the image size of the original image, the digital watermark pattern can be detected.

Next, a digital watermark embedding system according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram illustrating a configuration example of the digital watermark embedding system.
The reduced image generation unit 1 sequentially reduces the input original image with a predetermined reduction magnification α, and generates reduced images with predetermined reduction magnifications α, α * α, α * α * α, for example. However, the size limit of the reduced image is limited to the image size of the embedding unit in which the digital watermark pattern can be embedded.
Further, the combination of the reduction magnifications for embedding the digital watermark may be a combination of reduction images with reduction magnifications α, α * α, α * α * α, or a reduction image with reduction magnifications α, α * α * α. A combination may be used. However, it is a condition that the image sizes of all the reduced images are not smaller than the embedding unit.
The digital watermark pattern generation unit 2 generates a digital watermark pattern to be embedded in the original image and each reduced image and outputs it to the digital watermark embedding unit 3.

The digital watermark embedding unit 3 converts an image in which a digital watermark pattern is embedded into a frequency component, as represented by, for example, Fourier transform, spread spectrum, discrete cosine transform, etc. by a predetermined method, and does not affect the image quality. A digital watermark pattern is embedded in a specific frequency (medium and high frequency region) component.
Alternatively, the digital watermark embedding unit 3 may use a method of directly embedding a digital watermark pattern in bit data representing the gradation level (luminance information) of a pixel in an embedding unit.

The image enlargement unit 4 uses the bicubic method, the bilinear method, the near neighbor method, the method for estimating the high frequency described in “IECE, A, Vol. J86, No5, pp540-551”, and the high frequency of the original image. The reduced images a, b, and c are respectively enlarged to the image size of the original image using any one of the image enlargement methods such as the method of performing the above and output as the enlarged images A, B, and C.
The image synthesizing unit 5 synthesizes the original image and the enlarged images A, B, and C, and outputs the synthesized image as a digital watermarked image.

Next, the operation of the digital watermark embedding system according to the embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a flowchart showing an operation example of the digital watermark embedding system.
The reduced image generation unit 1 selects a reduction magnification for reducing the input original image from a reduction magnification input by the user or a reduction magnification set in advance (step S1).
At this time, the reduced image generation unit 1 uses a plurality of set reduction magnifications α, α * α, α * α * α,... So that the image size is sequentially reduced each time the process of step S1 is repeated. Select a reduction ratio.
Then, the reduced image generation unit 1 reduces the original image input with the selected reduction magnification α, and generates a reduced image a (step S2).

Next, the reduced image generation unit 1 detects whether or not the created reduced image a is smaller than the minimum embedding unit in which the digital watermark pattern can be embedded. The process is stored in the storage unit, and the process returns to step S1. If small is detected, the process proceeds to step S4 (step S3).
At this time, the reduced image generation unit 1 determines whether or not the reduced image has the number of pixels in which the digital watermark pattern can be embedded or whether a specific frequency that does not affect the image quality can be obtained when converted to a frequency component. By determining, it is detected whether or not the digital watermark pattern is smaller than the smallest embedding unit that can be embedded.

For example, when the reduced image generation unit 1 detects that the reduced image d with the reduction magnification α * α * α * α is smaller than the minimum embedding unit, the reduced image generation unit 1 deletes the reduced image and advances the process to step S4. (Step S3).
Accordingly, the storage unit of the reduced image generation unit 1 stores a reduced image a having a reduction magnification α, a reduced image b having a reduction magnification α * α, and a reduced image c having a reduction magnification α * α * α.
Then, the digital watermark pattern generation unit 2 converts the security information including the creation source information having the copyright set by the user or input by the user into the digital watermark pattern, and sends it to the digital watermark embedding unit 3. Output (step S4).

The digital watermark embedding unit 3 sets an image size of an embedding unit capable of embedding a digital watermark pattern as an embedding unit, and sets the image size of the original image and other reduced images a, b. Image size (hereinafter, embedded size).
Here, for example, when the reduced image c having the highest reduction ratio has one embedding size, if the reduction ratio α is set to 1/4, the reduced image b is divided into four embedding size blocks and reduced. The image a is divided into 16 embed-sized blocks, and the original image is divided into 64 embed-sized blocks.
Then, the digital watermark embedding unit 3 embeds a digital watermark pattern in each block unit of the above-described embedding size of the original image and the reduced images a, b, and c (step 5).

  In the above description, the reduced image generation unit 1 generates a plurality of reduced images having different reduction ratios (different image sizes) based on a new reduction ratio obtained by sequentially multiplying a predetermined reduction ratio as the reduction ratio of the original image. However, the present invention is not limited to this, and the reduced image generation unit 1 generates the reduced image so that the reduction magnification (for example, the reduction magnification α, β, γ,...) Is not proportional, The digital watermark embedding unit 3 may be configured to embed a digital watermark pattern corresponding to each.

Next, the image enlargement unit 4 enlarges each of the reduced original images a, b, c embedded with the digital watermark pattern to the image size of the original image by a predetermined enlargement method (described in detail later). , B and C (step S6).
Then, the image synthesis unit 5 synthesizes the image data of the original image and each of the enlarged images A, B, and C and outputs them as an image with a digital watermark.
At this time, the image synthesizing unit 5 uses any of the synthesizing methods of the following formulas (2) to (5) as the synthesis of the image.

The composite image (image with digital watermark) fWm is obtained by any one of the following equations (2) to (5).
fWm = Σ (f + fA + fB + fC +...) / N (2)
In this equation (2), N indicates the number of added images including the original image, f is the image data of the original image in which the digital watermark pattern is embedded, and fA, fB, and fC each indicate the digital watermark pattern. This is the image data of the embedded enlarged images A, B, and C. In equation (2), the image data of each image is added and the average is obtained to obtain an image with a digital watermark.

fWm = Σ (X1 * f + X2 * fA + X3 * fB + X4 * fC + ...) (3)
In this equation (3), X1, X2, X3, X4,... Are weighting factors corresponding to the respective reduction magnifications, and are tolerances when detecting the digital watermark pattern of each reduction magnification. In equation (2), because of simple addition, this is a special case where the weighting factors of all the reduction ratios are “1”. Also, ΣXi = 1.

fWm = Σ [(f−G) + (fA−G) + (fB−G) + (fC−G) +...] / N + G (4)
In the equation (4), G indicates image data of an original image in which a digital watermark pattern is not embedded. Only the data of the digital watermark pattern embedded in each image is calculated from the original image and each reduced image, and the data obtained by adding the digital watermark pattern is added to the image data of the original image, that is, synthesized, An entering image is generated.

fWm = Σ [Y1 * (f−G) + Y2 * (fA−G)
+ Y3 * (fB-G) + Y4 * (fC-G) + ...)] + G (5)
In the equation (5), Y1, Y2, Y3, Y4,... Are weighting factors corresponding to the respective reduction magnifications, and are tolerances when detecting the digital watermark pattern of each reduction magnification. In equation (4), because of simple addition, this is a special case where the weighting factors of all the reduction ratios are “1”. Further, ΣYi = 1.

Here, the enlargement method performed by the image enlargement unit 4 in step S6 will be described.
The nearest neighbor method, bilinear method, and bicubic method are pixel data complementing methods when enlarged.
In the nearest neighbor method, when the pixel before enlargement does not correspond to the coordinate value of the pixel after enlargement, the pixel data of the nearest coordinate value of the coordinate value before enlargement is filled.
In the bilinear method, when the pixel before enlargement does not correspond to the coordinate value of the pixel after enlargement, unlike the nearest neighbor method, the density complementation of the pixel data of four neighboring coordinate values is performed, and the coordinate value after enlargement The pixel data.

That is, as shown in FIG. 5, the bilinear method expanded the image data f (x, y) of size N1 * N2 and 0 ≦ x <N1 and 0 ≦ y <N2 by S times in both the vertical and horizontal directions. Think about the case.
The enlarged image data g (x, y) is f (x / S, y / S), and the pixel coordinate values are integer values in the range of 0 ≦ x <S × N1 and 0 ≦ y <S × N2. It becomes.
At this time, when the pixel (x / S, y / S) does not correspond to the pixel of the original image, it is necessary to complement the pixel data of this coordinate value.

And the said complement is performed by (6) Formula shown below.
f (x / S, y / S) = (1−Δx) * (1−Δy) * f 0 + Δx * (1−Δy) * f 1
+ (1−Δx) * Δy * f 2 + Δx * Δy * f 3 (6)
In this equation (2), Δx = (x / S) − “x / S”, Δy = (y / S) − “y / S”, and the coordinate values (“x / S”, “y / S” )), The pixel value f1 of the coordinate value (“x / S” +1, “y / S”), and the pixel value of the coordinate value (“x / S”, “y / S” +1) The value f2 is the pixel value f3 of the coordinate value (“x / S” +1, “y / S” +1).

If the pixel value before enlargement does not correspond to the pixel value before enlargement in the coordinate value after enlargement, the bilinear method complements the pixel data in the four surrounding coordinate values, whereas the bicubic method uses the pixel value in the surrounding 16 coordinate values. The density value is used to complement by a cubic function.
Since the three complementary methods of the nearest neighbor method, the bilinear method, and the bicubic method are general methods, further explanation is omitted.

Further, in order to obtain a high-precision enlarged image, pixel data complementing methods include a method of estimating a high-frequency region (high-frequency component) when enlarged, but the original image is known in the present invention. When enlarging a once reduced image, the high frequency region of the original image in which the digital watermark pattern is not embedded can be used.
Hereinafter, the enlargement process of the reduced image that has been subjected to the discrete wavelet transform will be described. Here, there are the following two enlargement methods using the discrete wavelet transform in the present invention.

<Method 1>
After reducing the image size of the original image to a power of 2 of the reduced image size, the reduced image is enlarged to the image size after this change, and after high frequency components are complemented, it is enlarged to the original image size of the original image To do.
That is, as shown in FIG. 6, for example, a case where a reduced image reduced to A times (0.2 times) the image size of the original image is enlarged to the image size of the original image (enlarged to 5 times) is considered. .
First, as processing 1, the original image is reduced to a power of 2 of the reduced image, 4 times here, that is, 4A times (0.8 times) the image size of the original image, and a reduced original image is generated.

Then, as processing 2, wavelet transformation of the reduced original image is performed, and as shown in FIG. 7, the reduced image is regarded as the low frequency component LLi using the high frequency components LHi, HLi, and HHi, the inverse wavelet transformation is performed, and the reduced image is obtained. Is enlarged to a power of 2 times 4A times.
As a result, an intermediate image is obtained which is an image in which digital watermark is embedded and information lost by the reduction (pixels lost by the reduction and luminance information of the pixels, etc.) is complemented by the high frequency component of the original image.
Next, as processing 3, the intermediate image is enlarged to the image size of the original image using a conventional data interpolation method such as a bicubic method, and output as an enlarged image for generating a digital watermarked image. .

<Method 2>
As processing 1, the reduced image is converted to an image size that is a power of 2 (for example, 1/2, 1/4, 1/8) with respect to the image size of the original image, as shown in FIG. Expand using conventional data interpolation methods such as the bicubic method.
At this time, the intermediate image is generated by enlarging to an image size that is the power of 2 of the image size of the original image that is closest to the image size of the reduced image, that is, by enlarging to an image size that is closest to the wavelet transform rank. .

If the reduced image to be enlarged is, for example, 0.2 times the image size of the original image, the image is enlarged to 0.25 times (1/4) the image size that is a power of 2 of the nearest original image, This is an intermediate image.
As processing 2, wavelet transformation of the original image is performed, and the obtained high frequency components LHi, HLi, HHi (i is a rank) are used, the intermediate image is regarded as the low frequency component LLi, and inverse wavelet transformation is performed. Is enlarged to the image size of the original image and output as an enlarged image for generating a digital watermarked image.

<Digital watermark detection system>
Hereinafter, a digital watermark detection system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 9 is a diagram cited for explaining the principle of the digital watermark embedding method of the present invention.
Here, it is assumed that the digital watermarked image f ′ in which the digital watermark pattern is embedded has an unknown magnification X (1> X).
By sequentially reducing the X-fold image with respect to the original image, the digital watermark pattern embedded at this image size is detected when the reduction ratio up to the magnification A is reached. .

For example, as shown in FIG. 10, the original image is sequentially multiplied by a predetermined magnification A = 1/2, and the original image, a reduced image that is 1/2 the image size of the original image, and 1 / the image size of the original image. A digital watermarked image f ′ in which a digital watermark is embedded by the above-described digital watermark embedding system with respect to a four times reduced image and a reduced image that is １ ／ times the original image is detected by this digital watermark pattern. This will be described as an image.
Here, the predetermined magnification is described as a reduction magnification of A, B = A * A, C = A * A * A,..., But the reduction magnification is not sequentially multiplied. A digital watermark pattern may be embedded without regularity in the reduction magnification of the reduced image.
Assuming that the detection target image has an unknown magnification of 0.8 times, the digital watermark embedded at the reduction magnification A is reduced at the reduction magnification A (1/2 times) by sequentially reducing the images. Detected.

Hereinafter, a digital watermark detection system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 11 is a block diagram illustrating a configuration example of the digital watermark detection system.
The reduced image generating unit 10 performs a process of sequentially reducing the input digital watermarked image (input image) at a predetermined reduction magnification (for example, 0.99 times). As the reduction ratio at the time of detection, a lower reduction ratio is used so as to reduce the reduction ratio in order to increase the resolution with respect to the reduction ratio when the digital watermark embedding system embeds the digital watermark pattern. Since it becomes a problem of the accuracy of whether or not a magnification close to a certain level can be reached, the finer the change in the reduction ratio, the higher the establishment of digital watermark detection.

The enlarged image generating unit 11 performs a process of sequentially enlarging the input digital watermarked image at a predetermined enlargement magnification (for example, 1.01 times).
The digital watermark detection unit 12 performs digital watermark detection processing on the digital watermarked image reduced by the reduced image generation unit 10 and the digital watermarked image enlarged by the enlarged image generation unit 11.
When the digital watermark pattern is embedded in the frequency domain, the digital watermark detection unit 12 analyzes the frequency domain information of the digital watermarked image, reads (detects) the digital watermark pattern, and stores the digital watermark pattern in the image space domain. When the digital watermark pattern is embedded, the pixel information of the digital watermarked image is analyzed to read the digital watermark pattern.

Next, the operation of the digital watermark detection system according to the embodiment of the present invention will be described with reference to FIGS. FIG. 12 is a flowchart showing an operation example of the digital watermark detection system.
The digital watermark detection unit 12 performs a process of reading the embedded digital watermark pattern for the input digital watermark-containing image (detection target image), and advances the process to step S12 (step S11).
Next, when the digital watermark is detected from the digital watermarked image, the digital watermark detection unit 12 advances the process to step S13.
Then, the digital watermark detection unit 12 outputs the detected digital watermark pattern together with information notifying that the detection has been made to the display unit or the like, and ends the process (step S13).

On the other hand, if the digital watermark is not detected from the digital watermarked image, the digital watermark detection unit 12 advances the process to step S14.
Accordingly, the reduced image generation unit 10 reads out the detection target image from which the digital watermark pattern has been detected from the digital watermark detection unit 12, reduces the detection target image with a predetermined reduction ratio, and creates a new detection target. It is set as an image (step S14).
Then, the reduced image generation unit 10 counts the number of times the image has been reduced, and based on this count number, the image size of the current detection target image is compared with the image size from the time when the image is input. Whether it is lower or lower is detected (step S15).

At this time, when the reduced image generation unit 10 detects that the reduction magnification of the detection target image is higher than the threshold value (the reduction rate is smaller than the threshold value), the reduction image generation unit 10 outputs the detection target image to the digital watermark detection unit 12. At the same time, the process proceeds to step S11. On the other hand, when it is detected that the reduction ratio of the detection target image is lower than the threshold value (the reduction ratio is larger than the threshold value), the digital watermark detection unit 12 is notified and the process is stepped. Proceed to S16.
Here, for example, when the digital watermark pattern is embedded in an image with digital watermark, the threshold value at the time of the reduction process is set using a reduction ratio at the time of reduction (may be set as a reduction ratio).

Next, the digital watermark detection unit 12 is notified of the fact that the reduction threshold has been exceeded from the reduced image generation unit 10, and the detection target image of the image size at the time of input stored therein is The image is output to the enlarged image generation unit 11 and an instruction to enlarge the detection target image is given.
The magnified image generation unit 11 reads out the detection target image from the digital watermark detection unit 12, enlarges the detection target image with a predetermined magnification, and sets it as a new detection target image (step S16).
Then, the magnified image generation unit 11 counts the number of times the image has been magnified, and from this count number, the image size of the current detection target image is compared with the image size from the point in time when the image size is input. Whether it is lower or lower is detected (step S17).

At this time, when the magnified image generation unit 11 detects that the magnification of the detection target image is lower than the threshold value (the magnification ratio is smaller than the threshold value), the magnified image generation unit 11 outputs the detection target image to the digital watermark detection unit 12. At the same time, the process proceeds to step S18. On the other hand, when it is detected that the enlargement magnification of the detection target image is higher than the threshold (the enlargement ratio is larger than the threshold), the electronic watermark detection unit 12 is notified and the process is terminated. To do.
Here, for example, when a digital watermark pattern is embedded in an image with a digital watermark, an enlargement factor obtained as the reciprocal of the reduction magnification is used between the reduced images having the largest reduction magnification. (It may be set as a reduction ratio).

The digital watermark detection unit 12 performs a process of reading the embedded digital watermark pattern for the input detection target image, and if a digital watermark is detected from the digital watermarked image, the process proceeds to step S13.
On the other hand, if the digital watermark is not detected from the digital watermarked image, the digital watermark detection unit 12 advances the process to step S16.

  A program for realizing the functions of the digital watermark embedding system in FIG. 1 and the digital watermark detection system in FIG. 11 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is stored in the computer system. The electronic watermark embedding and detection processing may be performed by reading and executing. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

It is a conceptual diagram explaining the concept of the embedding method of the digital watermark pattern in the digital watermark embedding system of one Embodiment of this invention. It is a conceptual diagram explaining the concept of the embedding method of the digital watermark pattern in the digital watermark embedding system of one Embodiment of this invention. 1 is a block diagram illustrating a configuration example of a digital watermark embedding system according to an embodiment of the present invention. It is a flowchart which shows the operation example of the digital watermark embedding system of one Embodiment of this invention. It is a conceptual diagram for demonstrating the bilinear method which is an example of the pixel complementation method used at the time of the image expansion used with the digital watermark embedding system of this invention. It is a conceptual diagram explaining the image expansion method used with the digital watermark embedding system of this invention. It is a conceptual diagram explaining the image expansion method used with the digital watermark embedding system of this invention. It is a conceptual diagram explaining the image expansion method used with the digital watermark embedding system of this invention. It is a conceptual diagram explaining the concept of the detection method of the digital watermark pattern in the digital watermark detection system of one Embodiment of this invention. It is a conceptual diagram explaining the concept of the detection method of the digital watermark pattern in the digital watermark detection system of one Embodiment of this invention. It is a block diagram which shows the structural example of the digital watermark detection system of one Embodiment of this invention. It is a flowchart which shows the operation example of the digital watermark detection system of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Reduced image generation part 2 ... Digital watermark pattern generation part 3 ... Digital watermark embedding part 4 ... Image expansion part 5 ... Image composition part 11 ... Enlarged image generation part 12 ... Digital watermark detection part

Claims (9)

A digital watermark embedding means for embedding a digital watermark corresponding to each image size with respect to the original image and the reduced image of the original image;
An image enlarging means for enlarging the reduced image embedded with the digital watermark to the image size of the original image and generating an enlarged image;
An electronic watermark embedding system comprising: an image synthesizing unit that synthesizes the original image and the enlarged image in which the electronic watermark is embedded, and outputs the synthesized image as an electronic watermarked image.   2. The digital watermark embedding system according to claim 1, further comprising reduced image generation means for reducing the original image at a predetermined ratio and generating a plurality of reduced images having different reduction ratios.   3. The digital watermark embedding system according to claim 1, wherein a weighting coefficient corresponding to the image size is added to information on the digital watermark embedded in the original image and the reduced image. An electronic watermarked image generated by embedding a digital watermark corresponding to the image size for each of the original image and the reduced image of the original image, and combining the images by returning the reduced image to the original image size And a watermark detection system for detecting an embedded watermark from the watermarked image whose image size has been changed,
Image size changing means for changing the image size of the digital watermarked image;
A digital watermark detection system, comprising: a digital watermark detection unit that detects a digital watermark from a synthesized digital watermarked image and a digital watermarked image whose size has been changed.   When the digital watermark detection unit cannot detect a digital watermark, the digital watermark detection unit has a detection control unit that sequentially changes the image size and causes the digital watermark detection unit to detect the digital watermark at a new image size. The digital watermark detection system according to claim 4. An electronic watermark embedding process for embedding an electronic watermark corresponding to each image size with respect to the original image and a reduced image of the original image,
An image enlargement process for enlarging a reduced image embedded with a digital watermark to the image size of the original image and generating an enlarged image,
An electronic watermark embedding method comprising: combining an original image embedded with an electronic watermark and an enlarged image, and outputting the resultant image as an electronic watermarked image. An electronic watermarked image generated by embedding a digital watermark corresponding to the image size for each of the original image and the reduced image of the original image, and combining the images by returning the reduced image to the original image size And a watermark detection method for detecting an embedded watermark from the watermarked image whose image size has been changed,
An image size changing process for changing an image size of the digital watermarked image;
A digital watermark detection process for detecting a digital watermark from the synthesized digital watermarked image and the digital watermarked image whose size has been changed;
A detection control step of sequentially changing the image size when the digital watermark detection unit cannot detect the digital watermark, and causing the digital watermark detection unit to detect the digital watermark at a new image size. Digital watermark detection method. An electronic watermark embedding process for embedding an electronic watermark corresponding to each image size for an original image and a reduced image of the original image;
An image enlargement process for enlarging a reduced image embedded with a digital watermark to the image size of the original image and generating an enlarged image;
A computer-executable digital watermark embedding program comprising: an image synthesis process for synthesizing the original image embedded with a digital watermark and an enlarged image and outputting the synthesized image as a digital watermarked image. An electronic watermarked image generated by embedding a digital watermark corresponding to the image size in each of the original image and the reduced image of the original image, and returning the reduced image to the original image size and synthesizing the images. , And a program for executing detection of an embedded watermark from the watermarked image whose image size has been changed,
An image size changing process for changing an image size of the digital watermarked image;
A digital watermark detection process for detecting a digital watermark from the combined digital watermarked image and the digital watermarked image whose size has been changed;
When the digital watermark detection unit cannot detect the digital watermark, the image processing method includes: a detection control process that sequentially changes the image size and causes the digital watermark detection unit to detect the digital watermark at a new image size. A digital watermark detection program executable by a computer.

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