JP2006014171A - Electronic watermark inserting method, electronic watermark inserting apparatus, electronic watermark inserting program, electronic watermark detection method, electronic watermark detecting apparatus, electronic watermark detection program, data transmission method, data transmission system, and data transmission program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase non-zero frequency components utilized for representing data among points provided to a frequency region. <P>SOLUTION: The electronic watermark inserting apparatus inserts non-zero frequency components representing data to an outermost circle in the frequency region and inserts non-zero frequency component for detecting rotation angles to an innermost circle. An electronic watermark detecting apparatus detects the non-zero frequency components for detecting rotation angles on the innermost circle by changing the radius to detect the angles and detects the non-zero frequency components for data on the outermost circle while changing the radius. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital watermark insertion method for inserting a digital watermark into image data, its apparatus and its program, a digital watermark detection method for detecting a digital watermark from image data into which the digital watermark has been inserted, its apparatus and its The present invention relates to a program, a data transmission method for transmitting data using digital watermarking, a data transmission system, and a data transmission program.

  In recent years, a technique for inserting a digital watermark into image data has been developed, and information for identifying a person who has a copyright, etc., information on usage methods and conditions for permitting the use of a copyrighted work, etc. in the form of a digital watermark. Insertion into image data has been put into practical use.

  Normally, a digital watermark is inserted and detected in the form of electronic data, but a digital watermark corresponding to printing has also appeared. This makes it possible to detect a digital watermark from the printed image data even when the image data into which the digital watermark is inserted is printed.

  However, conventional digital watermarking that also supports printing is premised on reading a printed matter using a scanner. Under such a premise, the scale of the read image is known in advance, and the image is never rotated. Further, since the scanner has a high resolution of about 6400 dpi, it can detect a digital watermark embedded in a high frequency component. Further, unlike the case of reading with a camera, there is no case of camera shake. Further, since the image is emitted from the scanner with a constant light source, the signal-to-noise ratio and the contrast are good.

  On the other hand, cellular phones with built-in cameras and electronic mail functions and WWW (World Wide Web) browser functions have recently become widespread. If an image with a digital watermark inserted is read by the camera of such a mobile phone, and the image is sent from the mobile phone as an attached file of an e-mail or form information on a homepage, the WWW server side detects the digital watermark, Based on this, information is retrieved from the database, and the mobile phone can receive various services such as provision of such information from a WWW server, a mail server, or the like.

  Therefore, the advent of a digital watermark insertion method, apparatus and program thereof, and digital watermark detection method, apparatus and program thereof that enable detection of a digital watermark from an image read by a built-in camera or the like of a mobile phone is desired. It was.

  However, the scale of an image read by a built-in camera of a mobile phone is indefinite due to factors such as the distance between the image and the camera. In addition, an image read by a built-in camera of a mobile phone is often rotated not a little because of a variation factor such as a relative rotation angle between the image and the camera. Furthermore, the resolution of the images read by the built-in cameras of most mobile phones is low. For example, the number of pixels when a 3 cm × 4 cm image is read by a 6400 dpi scanner is about 76 million, whereas the number of built-in cameras of the majority of mobile phones currently popular is about 300,000. It is clearer than there is. Further, an image read by a built-in camera of a mobile phone may cause camera shake. Furthermore, since an image read with a built-in camera of a mobile phone is read under ordinary external light, the signal-to-noise ratio and contrast are often insufficient.

Therefore, even if the image is unscaled, rotated, has low resolution, has camera shake, has a low signal-to-noise ratio, and has a poor contrast, the data embedded in the form of a digital watermark is stabilized. A robust digital watermark insertion method, apparatus and program thereof, and digital watermark detection method, apparatus and program thereof have been invented and disclosed in Patent Document 1. ing.
JP 2004-15396 A

  However, when a non-zero frequency component for detecting the enlargement / reduction ratio is provided in the frequency domain as in the invention described in Patent Document 1, when this is inverse Fourier transformed and added to the original image, The image quality will deteriorate to some extent. In addition, a point for detecting the rotation angle and a non-zero frequency component representing data are also provided in the frequency domain, and an inverse Fourier transform of this is also added to the original image, which also reduces the image quality of the original image to some extent. End up. Therefore, it is desirable to reduce the number of non-zero frequency components provided in the frequency domain as much as possible without increasing the frequency from the viewpoint of not deteriorating the image quality.

  On the other hand, if the same number of non-zero frequency components are provided in the frequency domain, using as many non-zero frequency components as possible to represent the data increases the number of possible values of the data to be embedded. From this point of view, it is desirable. Then, data having a larger amount of information can be embedded in the image.

  In addition, according to the invention described in Patent Document 1, since the radius of a circle in a frequency region into which a non-zero frequency component representing data is inserted is determined in advance, if the enlargement / reduction ratio of the captured image is known, the data Since the radius position of the circle in which the non-zero frequency component representing is inserted can be predicted, the confidentiality of the data is weak, and therefore, there is a possibility of being misused by a malicious third party, for example.

  Therefore, the present invention provides a digital watermark insertion method, apparatus and program thereof, digital watermark detection method and apparatus capable of increasing non-zero frequency components used for representing data among points provided in the frequency domain. And a program thereof, a data transmission method, a system thereof, and a program thereof.

  The present invention also provides a digital watermark insertion method, apparatus and program thereof, digital watermark detection method, apparatus and program thereof, data transmission method, system and program thereof that can enhance data confidentiality. The purpose is to do.

  According to the first aspect of the present invention, in the frequency domain, the first predetermined number of candidate positions arranged on a first circle having an indefinite radius are positions that are combined with each other by data to be inserted. Generating a non-zero frequency component for a second predetermined number less than the first predetermined number, and rotating the image to a position on a second circle different from the first circle in the frequency domain Generating a non-zero frequency component for detecting an angle; transforming the generated non-zero frequency component together from the frequency domain to a spatial domain; and adding all or a part of a block of an original image to the block And a step of adding or subtracting an image obtained by the conversion.

  In the above-described digital watermark insertion method, the positions on the second circle are all the positions before all the positions after being rotated by an angle other than 180 degrees around the origin of the frequency domain. The angle may not be any value other than 180 degrees.

  In the above-described electronic watermark insertion method, the data to be inserted are combined with each other among the third predetermined number of candidate positions arranged on a third circle different from the first circle and the second circle. And generating a non-zero frequency component at a fourth predetermined number less than the third predetermined number, wherein the converting step includes generating a non-zero frequency component on the third circle. Zero frequency components may also be transformed from the frequency domain to the spatial domain.

  According to a second aspect of the present invention, obtaining one or more image blocks from an image, converting data of the one or more image blocks from a spatial domain to a frequency domain, Obtaining an amplitude of each frequency component based on each frequency component; and detecting a non-zero frequency component for detecting a rotation angle of the image based on the amplitude of each frequency component in the frequency domain. And detecting the rotation angle of the image by the first predetermined number of rotations at the first predetermined number of positions on the circumference and using the detected rotation angles as a rotation reference in the frequency domain. Detecting whether there is a non-zero frequency component at any of a second predetermined number of positions less than the number for each circle of different radii, and at any of the second predetermined number of positions Said has been detected based on the combination of the position of the non-zero frequency component, digital watermark detection method characterized by comprising the steps of: detecting the data inserted in the image is provided.

  In the digital watermark detection method, the non-zero frequency component for detecting the rotation angle of the image may be distributed at positions on a circle.

  In the above-described digital watermark detection method, the positions on the circle are such that all the positions after rotating an angle other than 180 degrees centering on the origin of the frequency domain overlap all the positions before the rotation. However, the angle may not be any value other than 180 degrees.

  In the above-described digital watermark detection method, the step of detecting whether there is the non-zero frequency component related to data for each different radius is performed from a circle with a short radius toward a circle with a long radius, and the data related to the data By detecting whether or not there is a non-zero frequency component for each different radius, after the non-zero frequency component related to data is detected, it is detected at a third position on the circumference in the frequency domain. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the rotation images that are used as a rotation reference is determined based on the non-zero value related to the data The method further comprises a step of detecting each circle having a radius longer than that of the circle in which the frequency component is detected, and the step of detecting data inserted in the image has a position at any one of the second predetermined number. Not only the combination of the positions of the non-zero frequency components detected to be detected, but also the combination of the positions of the non-zero frequency components detected to be in any one of the fourth predetermined number of positions. The data inserted in the image may be detected.

  In the above digital watermark detection method, the step of detecting whether or not there is the non-zero frequency component related to the data for each different radius is performed from a circle with a long radius toward a circle with a short radius, and the data related to the data By detecting whether or not there is a non-zero frequency component for each different radius, after the non-zero frequency component related to data is detected, it is detected at a third position on the circumference in the frequency domain. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the rotation images that are used as a rotation reference is determined based on the non-zero value related to the data The method further comprises a step of detecting each circle having a radius shorter than that of the circle in which the frequency component is detected, and the step of detecting the data inserted in the image has a position at any one of the second predetermined number. Not only the combination of the positions of the non-zero frequency components detected to be detected, but also the combination of the positions of the non-zero frequency components detected to be in any one of the fourth predetermined number of positions. The data inserted in the image may be detected.

  In the above-described digital watermark detection method, the method further includes the step of passing the image through a spatial filter, and the step of obtaining one or more image blocks from the image is a step of obtaining one or more image blocks from the image passed through the spatial filter. There may be.

  According to the third aspect of the present invention, in the frequency domain, the first predetermined number of candidate positions arranged on a first circle having an indefinite radius are positions that are combined with each other by data to be inserted. Generating a non-zero frequency component for a second predetermined number less than the first predetermined number, and rotating the image to a position on a second circle different from the first circle in the frequency domain Generating a non-zero frequency component for detecting an angle; transforming the generated non-zero frequency component together from the frequency domain to a spatial domain; and adding all or a part of a block of an original image to the block A step of adding or subtracting the image obtained by the conversion, a step of obtaining one or more image blocks from the image that has undergone the addition or subtraction, and the frequency of the data of the one or more image blocks from a spatial domain Converting to a region; obtaining an amplitude of each frequency component based on each frequency component of the one or more image blocks; and rotating the image based on the amplitude of each frequency component in the frequency region. Detecting a rotation angle of the image by detecting a non-zero frequency component for detecting an angle; and the rotation detected at a first predetermined number of positions on a circumference in the frequency domain. Detecting for each circle of different radii whether or not there is a non-zero frequency component at any of a second predetermined number less than the first predetermined number of angles based on rotation. Detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be at any one of the second predetermined number of positions. Data transmission method according to claim is provided.

  According to the present invention, since it is not necessary to arrange non-zero frequency components for detecting the enlargement / reduction ratio, the non-zero frequency components are represented in order to represent data under the assumption that the number of non-zero frequency components is a predetermined number. The zero frequency component can be used effectively.

  In addition, according to the present invention, since it is not necessary to arrange non-zero frequency components for detecting the enlargement / reduction ratio, the number of non-zero frequency components for representing data and the non-zero frequency for detecting the rotation angle are used. Under the assumption that the number of components is a predetermined number, the image quality can be improved.

  Furthermore, according to the present invention, since the radius of the circle in the frequency region where the non-zero frequency component representing the data is inserted is indefinite, the confidentiality of the data can be improved.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a pattern in the frequency domain used in the embodiment of the present invention. In FIG. 1, black circles indicate non-zero frequency components, and white circles indicate zero frequency components. Here, the non-zero frequency component is a frequency component whose amplitude is not zero, and the zero frequency component is a frequency component whose amplitude is zero.

  As shown in FIG. 1, the outermost circle is divided into 20 equal parts, and non-zero frequency components or zero frequency components are arranged at 20 positions. The outermost circle is divided into 20 equal parts by providing an angle offset so that none of the 20 positions overlaps the X axis or the Y axis. The innermost circle is also divided into 20 equal parts, and non-zero frequency components are arranged at 10 positions out of the 20 positions.

  In the pattern shown in FIG. 1, the position where the non-zero frequency component or the zero frequency component is arranged is selected so as not to overlap with the X axis or the Y axis. In the frequency domain obtained by conversion, a large number of non-zero frequency components due to noise are generated on the X-axis and the Y-axis, and such non-zero frequency components are inserted by the digital watermark insertion device. This is because there is a high possibility that they cannot be distinguished from each other.

  The pattern shown in FIG. 1 can be decomposed into the patterns shown in FIGS. The pattern shown in FIG. 2 is a pattern representing data, and the pattern shown in FIG. 3 is a pattern for detecting a rotation angle.

Referring to FIG. 2, patterns representing data are formed at 20 positions obtained by dividing the outermost circle into 20 equal parts. Non-zero frequency components are arranged at 10 of the 20 positions, and zero frequency components are arranged at the remaining 10 positions (non-zero frequency components are not arranged). Since the amplitude of the frequency component is distributed point-symmetrically around the origin, selecting 10 positions from 20 positions is equivalent to selecting 5 positions from 10 positions. Therefore, the pattern representing data can represent ₁₀ C ₅ = 252 kinds of data.

  Referring to FIG. 3, the pattern for detecting the rotation angle is formed by arranging non-zero frequency components at 10 positions out of 20 positions obtained by dividing the innermost circle into 20 equal parts. The

  In order to detect the rotation angle of the image, the radius of the circle is gradually increased from zero until it is detected that there are 10 non-zero frequency components on the circle, and the 10 non-zero when detected. The angle of the position seen in polar coordinates in the frequency domain of the zero frequency component is detected.

  If the rotation angle of the image is detected, we can know the angle seen in polar coordinates in the frequency domain of the 20 positions where there should be non-zero frequency components or zero frequency components, so those on the circle A window is provided at the angle position, and the radius of the circle is gradually increased from the radius of the innermost circle until it is detected that there are 10 non-zero frequency components at the position of the window. The position seen in the polar coordinate in the frequency domain of the non-zero frequency component of is detected. Data is detected from the combination of the positions and the rotation angle.

  The pattern for detecting the rotation angle is not limited to that shown in FIG. For example, even if a non-zero frequency component is inserted into two positions obtained by dividing the innermost circle into two, the rotation angle can be detected. Further, as shown in FIG. 4, the rotation angle can be detected even when non-zero frequency components distributed in the innermost circle are inserted. Here, when the rotation angle is 0 degree and when the rotation angle is 180 degrees, the amplitude distribution of the frequency components is the same, so it is necessary to distinguish between the 0 degree rotation angle and the 180 degree rotation angle. There is no. Therefore, the pattern for detecting the rotation angle is generally all positions in the pattern before rotating the positions in all patterns after rotating an angle other than 180 degrees around the origin of the frequency domain. The angle does not overlap with any value other than 180 degrees.

Further, as shown in FIG. 4, a circle having a radius longer than the outermost circle shown in FIG. 1 is provided, and non-zero frequency components are inserted into 10 positions out of 20 positions on the circle, and the rest The zero frequency components may be inserted at the ten positions (not to insert non-zero frequency components). In this case, since the number of combinations of the positions of the non-zero frequency components on the circle is ₁₀ C ₅ = 252, it is multiplied by the combination of the positions of the non-zero frequency components on the outermost circle shown in FIG. 252 × 252 = 63504 data can be represented.

  Furthermore, in the example of FIGS. 1 and 4, all the circles are divided into 20 parts, but the number of divisions may be different for each circle. Moreover, you may change the angle seen in the polar coordinate of the frequency domain of a division position for every circle. However, it is necessary to make the relative angle between the number of divisions and the circles of the division positions uniform between the digital watermark insertion side and the digital watermark detection side.

  FIG. 5 is a block diagram showing the configuration of the digital watermark insertion apparatus according to the embodiment of the present invention.

  Referring to FIG. 5, the digital watermark insertion apparatus according to the embodiment of the present invention includes a rotation angle detection pattern generation unit 101, a data holding unit 102, a data pattern generation unit 103, a synthesis unit 104, an inverse discrete Fourier transform unit 105, two A valuation unit 106 and an addition unit 107 are provided. These parts can be realized by hardware, but can also be realized by reading and executing a program for causing a computer to function as these parts.

  Next, a digital watermark insertion method performed by the digital watermark insertion apparatus will be described with reference to FIGS.

  The rotation angle detection pattern generation unit 101 generates a rotation angle detection pattern as shown in FIG. 3 (step S151). The data holding unit 102 holds data to be inserted. The data pattern generation unit 103 generates a data pattern as shown in FIG. 2 according to the data value held in the data holding unit 102 (step S152). The combining unit 104 combines the rotation angle detection pattern generated by the rotation angle detection pattern generation unit 101 and the data pattern generated by the data pattern generation unit 103 to generate a pattern as shown in FIG. 1 (step S153). ). The inverse Fourier transform unit 105 performs inverse Fourier transform on the pattern as shown in FIG. 1 generated by the synthesis unit 104 to generate a pattern in the spatial domain (spatial domain pattern) (step S154). The binarization unit 106 binarizes the space area pattern generated by the inverse Fourier transform unit 105 (step S155). The adding unit 107 adds the spatial region pattern binarized by the binarizing unit 106 to all or some of the yellow components of the original image (step S156).

  Note that a spatial region pattern that does not pass through the binarization unit 106 may be added to the yellow component of the original image. Alternatively, the adding unit 107 may be replaced with a subtracting unit, and a binarized spatial region pattern or a non-binarized spatial region pattern may be subtracted from the yellow component of the original image.

  FIG. 7 is a block diagram showing the configuration of the digital watermark detection apparatus according to the embodiment of the present invention.

  Referring to FIG. 7, a digital watermark detection apparatus according to an embodiment of the present invention includes a spatial filter 201, a blocking unit 202, a discrete Fourier transform unit 203, an amplitude calculation unit 204, an amplitude integration unit 205, a rotation angle detection unit 206, and data. A detection unit 207 is provided. These parts can be realized by hardware, but can also be realized by reading and executing a program for causing a computer to function as these parts.

  Next, a digital watermark detection method performed by the digital watermark detection apparatus shown in FIG. 7 will be described with reference to FIGS.

  As apparent from the fact that the spatial filter 201 has weights as shown in FIG. 9, it has a band pass characteristic. The spatial filter 201 is applied to the blue component (digital watermark inserted image) of the image into which the digital watermark has been inserted (step S251). Thereby, non-zero frequency components other than the pattern shown in FIG. 1 are suppressed. The blocking unit 202 blocks the digital watermark insertion image to which the spatial filter is applied into one or more blocks (step S252). The discrete Fourier transform unit 203 performs discrete Fourier transform on the digital watermark insertion image of each block output from the blocking unit 202 to obtain each frequency component of each block (step S253). The amplitude calculator 204 calculates the amplitude of each frequency component of each block (step S254). The amplitude integrating unit 205 integrates the amplitude for each frequency between the blocks (step S255). The rotation angle detection unit 206 detects the non-zero frequency component of the innermost circle as shown in FIG. 3 based on the amplitude of each frequency component output from the amplitude integration unit 205, and based on this, the rotation angle of the image is determined. Detection is performed (step S256). Details of this detection will be described later. The data detection unit 208 detects data based on the amplitude output from the amplitude integration unit 205 and the rotation angle output from the rotation angle detection unit 206 (step S257). Details of this detection will also be described later.

  FIG. 10 is a block diagram showing a configuration of a digital watermark detection apparatus according to another embodiment of the present invention.

  Referring to FIG. 10, a digital watermark detection apparatus according to an embodiment of the present invention includes a spatial filter 201, a blocking unit 202, a discrete Fourier transform unit 203, a frequency component integration unit 304, an amplitude calculation unit 305, a rotation angle detection unit 206, and A data detection unit 207 is provided. These parts can be realized by hardware, but can also be realized by reading and executing a program for causing a computer to function as these parts.

  Next, a digital watermark detection method performed by the digital watermark detection apparatus shown in FIG. 10 will be described with reference to FIGS.

  The operations of the spatial filter 201, the blocking unit 202, and the discrete Fourier transform unit 203 are the same as those of the digital watermark detection apparatus shown in FIG. The frequency component integrating unit 304 integrates the frequency components of the blocks output from the discrete Fourier transform unit 203 as complex numbers (step S354). The amplitude calculation unit 305 calculates the amplitude of the complex integration value output by the frequency component integration unit 304 (step S355). The rotation angle detection unit 206 detects the non-zero frequency component of the innermost circle as shown in FIG. 3 based on the amplitude of each frequency component output from the amplitude calculation unit 305, and based on this, the rotation angle of the image is determined. Detection is performed (step S256). Details of this detection will be described later. The data detection unit 208 detects data based on the amplitude output from the amplitude integration unit 205 and the rotation angle output from the rotation angle detection unit 206 (step S257). Details of this detection will also be described later.

  Next, details of the step of detecting the rotation angle (step S256) will be described with reference to FIG.

  First, the parameter radius is initialized to zero corresponding to the minimum frequency in the frequency domain (step S401). Next, it is determined whether N1 (10 in the example of FIG. 1) non-zero frequency components exist on the circumference of the current radius (step S402). If it does not exist (NO in step S402), the radius is increased by ΔR corresponding to the discrete frequency unit interval in the frequency domain (step S403), and step S402 is performed again.

  In step S402, the following is performed. That is, 2 × N1 windows are provided for each angle obtained by dividing 360 degrees into 2 × N1, and N1 nonzero frequency components having amplitudes exceeding the threshold value after passing all frequency components through the window. Check if it can be detected while shifting the window angle. If it can be detected, the N1 non-zero frequency components are non-zero frequency components to be detected.

  If it exists (YES in step S402), it means that the circle with the current radius is the innermost circle, and therefore the rotation angle is detected based on the distribution of the detected N1 non-zero frequency components (step S404). ).

  Although not shown in FIG. 12, if N1 non-zero frequency components cannot be detected even when the radius becomes zero, steps S402 and S403 are repeated with the width in the radial direction of the window widened. If N1 non-zero frequency components cannot be detected at any radius, the threshold value is lowered after returning the radial width of the window, and steps S402 and S403 are repeated. If N1 non-zero frequency components still cannot be detected at any radius, steps S402 and S403 are repeated again by changing the radial width of the window. The same is repeated thereafter.

  Next, details of the step of detecting data (step S257) will be described with reference to FIG.

  First, a radius as a parameter is initialized to a radius of an innermost circle that is a circle for detecting a rotation angle (step S421). Next, it is determined whether or not N1 (10 in the example of FIG. 1) non-zero frequency components exist on the circumference of the current radius (step S422). If it does not exist (NO in step S422), the radius is increased by ΔR corresponding to the discrete frequency unit interval in the frequency domain (step S423), and step S422 is performed again.

  The detection method in step S422 is the same as the detection method in step S402. If it cannot be detected, a retry similar to the above is performed.

  If it exists (YES in step S422), it means that the circle with the current radius is the outermost circle, and therefore based on the distribution of the detected N1 non-zero frequency components and the rotation angle detected in step S256. The data is detected (step S424).

  As shown in FIG. 4, when there is a data circle outside the outermost circle shown in FIG. 1, the same processing as in steps S421 to S423 is also performed for the data circle. Data is detected based on the distribution of non-zero frequency components and the rotation angle detected in step S256.

  Note that the passband of the spatial filter shown in FIG. 9 is centered on a half of the Nyquist frequency, so that when captured by a camera, even if it is enlarged or reduced in a range of about 80% to about 130%, In the image that has passed through the spatial filter, the digital watermark is emphasized and the effect of suppressing the original image can be obtained. When the image taken by the camera is enlarged or reduced beyond the above range, the digital watermark is emphasized and the original image is suppressed in the image that has passed through the spatial filter shown in FIG. Therefore, the digital watermark may not be detected, but in such a case, the passband of the spatial filter may be changed and the detection of the digital watermark may be retried again. .

  In order to obtain data corresponding to a digital watermark by inserting a digital watermark into an image printed on a printed material, photographing the image with a camera or the like, and detecting the digital watermark from the captured image Can be used.

It is the figure which showed the electronic watermark utilized in embodiment of this invention in the frequency domain. It is a figure which shows the part showing data among the digital watermarks shown in FIG. It is a figure which shows the digital watermark for a rotation angle detection among the digital watermarks shown in FIG. It is the figure which showed the modification of the digital watermark utilized in embodiment of this invention in a frequency domain. It is a block diagram which shows the structure of the digital watermark insertion apparatus by embodiment of this invention. 5 is a flowchart illustrating a digital watermark insertion method performed by the digital watermark insertion apparatus according to the embodiment of the present invention. It is a block diagram which shows the structure of the digital watermark detection apparatus by embodiment of this invention. 5 is a flowchart illustrating a digital watermark detection method performed by the digital watermark detection apparatus according to the embodiment of the present invention. It is a figure which shows the example of the tap coefficient of the spatial filter used with the digital watermark detection apparatus by embodiment of this invention. It is a block diagram which shows the structure of the digital watermark detection apparatus by other embodiment of this invention. 6 is a flowchart illustrating a digital watermark detection method performed by a digital watermark detection apparatus according to another embodiment of the present invention. 3 is a flowchart illustrating a method for detecting a rotation angle according to an embodiment of the present invention. 3 is a flowchart illustrating a method for detecting data according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Rotation angle detection pattern generation part 102 Data holding part 103 Data pattern generation part 104 Synthesis | combination part 105 Inverse discrete Fourier transform part 106 Binarization part 107 Addition part (subtraction part)
201 Spatial Filter 202 Blocking Unit 203 Discrete Fourier Transform Unit 204 Amplitude Calculation Unit 205 Amplitude Integration Unit 206 Rotation Angle Detection Unit 207 Data Detection Unit 304 Frequency Component Integration Unit 305 Amplitude Calculation Unit

Claims (23)

In the frequency domain, the first predetermined number of candidate positions arranged on a first circle with an indefinite radius are positions that are combined with each other by data to be inserted, and the second number smaller than the first predetermined number Generating a non-zero frequency component for a predetermined number;
Generating a non-zero frequency component for detecting a rotation angle of the image at a position on a second circle different from the first circle in the frequency domain;
Combining the generated non-zero frequency components from the frequency domain to the spatial domain;
Adding or subtracting the image obtained by the conversion to all or a part of the blocks of the original image;
An electronic watermark insertion method comprising: The digital watermark insertion method according to claim 1,
The positions on the second circle are such that all the positions after rotating at an angle other than 180 degrees around the origin of the frequency domain overlap with all the positions before rotating. An electronic watermark insertion method characterized in that the angle is not set to any value other than 180 degrees. The digital watermark insertion method according to claim 1,
Of the third predetermined number of candidate positions arranged on a third circle different from the first circle and the second circle, the positions are combined with each other by the data to be inserted, and the third circle Generating a non-zero frequency component in a fourth predetermined number less than the predetermined number of
In the converting step, a non-zero frequency component generated on the third circle is also converted from the frequency domain to the spatial domain. Obtaining one or more image blocks from the image;
Converting the data of the one or more image blocks from a spatial domain to a frequency domain;
Obtaining the amplitude of each frequency component based on each frequency component of the one or more image blocks;
Detecting the rotation angle of the image in the frequency domain by detecting a non-zero frequency component for detecting the rotation angle of the image based on the amplitude of each frequency component;
Any one of a second predetermined number smaller than the first predetermined number among the first predetermined number of positions on the circumference in the frequency domain and the rotation angle detected as a rotation reference. Detecting for each circle of different radii whether there is a non-zero frequency component at the position of
Detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any of the second predetermined number of positions;
An electronic watermark detection method comprising: The digital watermark detection method according to claim 4,
The digital watermark detection method according to claim 1, wherein the non-zero frequency components for detecting the rotation angle of the image are distributed at positions on a circle. The digital watermark detection method according to claim 5, wherein
The position on the circle means that all the positions after rotating an angle other than 180 degrees around the origin of the frequency domain overlap with all the positions before rotating. A digital watermark detection method characterized in that it does not have any value other than degrees. The digital watermark detection method according to claim 4,
The step of detecting whether there is the non-zero frequency component related to the data for each different radius is performed from a circle with a short radius toward a circle with a long radius,
A third position on the circumference in the frequency domain after the non-zero frequency component related to the data is detected by detecting whether the non-zero frequency component related to the data exists for each different radius. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the detected rotation images as a rotation reference. Detecting for each circle having a longer radius than the circle in which the non-zero frequency component is detected,
In the step of detecting data inserted in the image, not only the combination of the positions of the non-zero frequency components detected to be in any of the second predetermined number of positions, but also the fourth predetermined An electronic watermark detection method, comprising: detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any position of the number. The digital watermark detection method according to claim 4,
The step of detecting whether there is the non-zero frequency component related to the data for each different radius is performed from a circle with a long radius toward a circle with a short radius,
A third position on the circumference in the frequency domain after the non-zero frequency component related to the data is detected by detecting whether the non-zero frequency component related to the data exists for each different radius. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the detected rotation images as a rotation reference. Detecting for each circle having a shorter radius than the circle in which the non-zero frequency component is detected,
In the step of detecting data inserted in the image, not only the combination of the positions of the non-zero frequency components detected to be in any of the second predetermined number of positions, but also the fourth predetermined An electronic watermark detection method, comprising: detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any position of the number. The digital watermark detection method according to claim 4,
Further comprising passing the image through a spatial filter;
The step of obtaining one or more image blocks from the image is a step of obtaining one or more image blocks from an image that has passed through the spatial filter. In the frequency domain, the first predetermined number of candidate positions arranged on a first circle with an indefinite radius are positions that are combined with each other by data to be inserted, and the second number smaller than the first predetermined number Generating a non-zero frequency component for a predetermined number;
Generating a non-zero frequency component for detecting a rotation angle of the image at a position on a second circle different from the first circle in the frequency domain;
Combining the generated non-zero frequency components from the frequency domain to the spatial domain;
Adding or subtracting the image obtained by the conversion to all or a part of the blocks of the original image;
Obtaining one or more image blocks from the image that has undergone the addition or subtraction;
Converting the data of the one or more image blocks from a spatial domain to a frequency domain;
Obtaining the amplitude of each frequency component based on each frequency component of the one or more image blocks;
Detecting the rotation angle of the image in the frequency domain by detecting a non-zero frequency component for detecting the rotation angle of the image based on the amplitude of each frequency component;
Any one of a second predetermined number smaller than the first predetermined number among the first predetermined number of positions on the circumference in the frequency domain and using the detected rotation angle as a rotation reference. Detecting for each circle of different radii whether there is a non-zero frequency component at the position of
Detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any of the second predetermined number of positions;
A data transmission method comprising: In the frequency domain, the first predetermined number of candidate positions arranged on a first circle having an indefinite radius are positions that are combined with each other by data to be inserted, and are less than the first predetermined number. Means for generating a non-zero frequency component in a predetermined number;
Means for generating a non-zero frequency component for detecting a rotation angle of the image at a position on a second circle different from the first circle in the frequency domain;
Means for combining the generated non-zero frequency components into a spatial domain from the frequency domain;
Means for adding or subtracting the image obtained by the conversion to all or a part of the blocks of the original image;
An electronic watermark insertion apparatus comprising: The digital watermark insertion apparatus according to claim 11, wherein
The positions on the second circle are such that all the positions after rotating at an angle other than 180 degrees around the origin of the frequency domain overlap with all the positions before rotating. An electronic watermark insertion apparatus characterized in that the angle is not set to any value other than 180 degrees. The digital watermark insertion apparatus according to claim 11, wherein
Of the third predetermined number of candidate positions arranged on a third circle different from the first circle and the second circle, the positions are combined with each other by the data to be inserted, and the third circle Means for generating a non-zero frequency component in a fourth predetermined number less than the predetermined number of
The digital watermark insertion apparatus characterized in that the converting means converts a non-zero frequency component generated on the third circle from the frequency domain to the spatial domain. Means for obtaining one or more image blocks from the image;
Means for transforming the data of the one or more image blocks from a spatial domain to a frequency domain;
Means for obtaining the amplitude of each frequency component based on each frequency component of the one or more image blocks;
Means for detecting the rotation angle of the image in the frequency domain by detecting a non-zero frequency component for detecting the rotation angle of the image based on the amplitude of each frequency component;
Any one of a second predetermined number smaller than the first predetermined number among the first predetermined number of positions on the circumference in the frequency domain and the rotation angle detected as a rotation reference. Means for detecting for each circle of different radii whether there is a non-zero frequency component at the position of
Means for detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any of the second predetermined number of positions;
An electronic watermark detection apparatus comprising: The digital watermark detection apparatus according to claim 14,
The digital watermark detection apparatus, wherein the non-zero frequency component for detecting the rotation angle of the image is distributed at positions on a circle. The digital watermark detection apparatus according to claim 15, wherein
The position on the circle means that all the positions after rotating an angle other than 180 degrees around the origin of the frequency domain overlap with all the positions before rotating. An electronic watermark detection apparatus characterized by having no value other than degrees. The digital watermark detection apparatus according to claim 14,
The means for detecting whether there is the non-zero frequency component related to the data for each different radius is performed from a circle with a short radius toward a circle with a long radius,
A third position on the circumference in the frequency domain after the non-zero frequency component related to the data is detected by means for detecting for each different radius whether or not the non-zero frequency component related to the data exists. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the detected rotation images as a rotation reference. Further comprising means for detecting each circle having a longer radius than the circle in which the non-zero frequency component is detected,
In the means for detecting data inserted in the image, not only the combination of the positions of the non-zero frequency components detected to be in any of the second predetermined number of positions, but also the fourth predetermined An electronic watermark detection apparatus for detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any position of the number. The digital watermark detection apparatus according to claim 14,
The means for detecting whether there is the non-zero frequency component related to the data for each different radius is performed from a circle with a long radius toward a circle with a short radius,
A third position on the circumference in the frequency domain after the non-zero frequency component related to the data is detected by means for detecting for each different radius whether or not the non-zero frequency component related to the data exists. Whether or not there is a non-zero frequency component at any position of the fourth predetermined number smaller than the third predetermined number of the detected rotation images as a rotation reference. Further comprising means for detecting each circle having a shorter radius than the circle in which the non-zero frequency component is detected,
In the means for detecting data inserted in the image, not only the combination of the positions of the non-zero frequency components detected to be in any of the second predetermined number of positions, but also the fourth predetermined An electronic watermark detection apparatus for detecting data inserted in the image based on a combination of positions of the non-zero frequency components detected to be in any position of the number. The digital watermark detection apparatus according to claim 4,
Further comprising means for passing the image through a spatial filter;
The digital watermark detection apparatus characterized in that the means for obtaining one or more image blocks from the image is means for obtaining one or more image blocks from the image that has passed through the spatial filter. In the frequency domain, the first predetermined number of candidate positions arranged on a first circle having an indefinite radius are positions that are combined with each other by data to be inserted, and the second predetermined number is less than the first predetermined number. Means for generating a non-zero frequency component in a predetermined number;
Means for generating a non-zero frequency component for detecting a rotation angle of the image at a position on a second circle different from the first circle in the frequency domain;
Means for combining the generated non-zero frequency components into a spatial domain from the frequency domain;
Means for adding or subtracting the image obtained by the conversion to all or a part of the blocks of the original image;
Means for obtaining one or more image blocks from the image that has undergone the addition or subtraction;
Means for transforming the data of the one or more image blocks from a spatial domain to a frequency domain;
Means for obtaining the amplitude of each frequency component based on each frequency component of the one or more image blocks;
Means for detecting the rotation angle of the image in the frequency domain by detecting a non-zero frequency component for detecting the rotation angle of the image based on the amplitude of each frequency component;
Any one of a second predetermined number smaller than the first predetermined number among the first predetermined number of positions on the circumference in the frequency domain and using the detected rotation angle as a rotation reference. Means for detecting for each circle of different radii whether there is a non-zero frequency component at the position of
Means for detecting data inserted into the image based on a combination of positions of the non-zero frequency components detected to be in any of the second predetermined number of positions;
A data transmission device comprising:   The program for making a computer perform the electronic watermark insertion method of any one of Claims 1 thru | or 3.   The program for making a computer perform the electronic watermark detection method of any one of Claims 4 thru | or 9.   The program for making a computer perform the data transmission method of Claim 10.

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