JP2001053954A - Device and method for embedding information and reading information, digital watermark system and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital watermark system by which information is surely and easily reproduced from an image, in which information is embedded, without using a standard image even when that image is changed. SOLUTION: An element information extracting part 13 extracts the element information of a character from the image data of a document acquired by a main information input part 11. On the basis of this element information, an element information converting part 17 generates sub-information showing the size relation of rectangular areas surrounding characters in the document with minimum areas and changes the element information so that a copyright code acquired by a sub-information input part 15 can be matched with the prescribed part of the sub-information. A main information reconstituting part 18 changes image data on the basis of the changed element information and a main information output part 19 prints the document expressed by the changed image data. When the element information extracting part 13 extracts the element information from the document in which the copyright code is embedded, a sub-information reading part 20 extracts the sub-information from the extracted element information and the prescribed part of that sub-information is displayed by a sub-information output part 21 as a copyright code.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital watermark system, and more particularly to a digital watermark system in which information is embedded in an image.

[0002]

2. Description of the Related Art As a method for verifying the copyright or verifying the authenticity of electronic information, a method using a digital watermark technology has been considered. The digital watermark technology is a technology for embedding sub-information, which is information separate from the main information, into main information, which is information to be transmitted. The main information embedded with the sub information using the digital watermark technology can be used without being aware of the existence of the sub information, and the sub information is
The feature is that it is difficult to determine in what form it is embedded in the main information.

[0003] The main information to which the sub-information is embedded using the digital watermark technique may be information representing an image. Information of a document image representing an image in which a readable code such as a character is described, such as a dissertation or a musical score, is transmitted using paper on which the document image is printed or transmitted by facsimile.

A technique for embedding sub-information by changing the run length of a row of pixels of the same color arranged on a scanning line of a facsimile image includes a digital watermarking technique for an image assumed to be transmitted by facsimile (Tanaka, Matsui: "MH"). Multiplexing of Information in Facsimile Communication ", Journal of the Institute of Image Electronics Engineers of Japan V
ol.18 No.1 pp.2-8).

In this technique, a binary image such as a black-and-white image is decomposed into a plurality of scanning lines, and the number of pixels having the same value (run length) in a row continuously arranged on the scanning lines is embedded in the image. Is changed according to the logical value of each bit constituting the information. Specifically, for example, when the logical value of a bit constituting the information to be embedded is “0”, of the columns of pixels of the same value that are continuously arranged on the scanning line, If the run length is even, the run length is extended by one pixel. If the run length is odd, the run length is left as it is.
When the logical value of the bit is "1", the run length is reduced by one pixel if the run length of the column associated with the bit is odd, and if it is even, the run length is left as it is. I do.

As a technique that can be used when an image includes a code such as a character, an image of a code constituting main information is rotated by a predetermined amount with respect to a predetermined standard image, so that sub-information is obtained. There was also an embedding method (Nakamura, Matsui: "Digital watermarking of Japanese documents with seal images", a technology disclosed in IPSJ Transactions Vol.38 No.11 pp.2356-2361).

In this technique, for example, the logical value of a bit constituting the seal information as information to be embedded is "1".
, The character associated with the bit among the characters constituting the main information is inclined by a predetermined angle. When the logical value of the bit is “0”, the character associated with the bit is not tilted.

[0008]

However, in the case of the digital watermarking technique in which the run length is changed, even if the image representing the main information in which the sub information is embedded is slightly deteriorated, the embedded sub information is normally reproduced. Was difficult to do. Therefore, when sub-information is reproduced from an image transmitted using a facsimile or a copy of the original image, for example, the communication quality of the line used for transmission or slight deterioration in the reproducibility of the copy may cause the sub-information to be reproduced. Normal reproduction was inhibited.

When the sub-information is information indicating the copyright of the main information, it is necessary that anyone can easily confirm the sub-information. However, in the case of a method of changing an image with reference to a standard image, such as a method of rotating a code, it is necessary to prepare a standard image in advance in order to reproduce sub-information. For this reason, when the method of changing the image with reference to the standard image is used, those who do not have the standard image cannot reproduce the sub-information, and it cannot be said that anyone can easily confirm the sub-information.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and provides an electronic watermarking system capable of reliably and easily reproducing information from an image in which information is embedded without using a standard image even if the image changes. Another object of the present invention is to provide an information embedding device, an information reading device, an information embedding method, and an information reading method for configuring such a digital watermark system.

[0011]

In order to achieve the above object, an information embedding device according to a first aspect of the present invention comprises:
An element information extraction unit that acquires main information including an array of codes and generates element information indicating characteristics of the shape of the code included in the obtained main information, and from the element information, a plurality of characteristics of the shape of the code. A sub-information reading unit for extracting sub-information indicating a relative difference, and acquiring additional information for embedding in the main information, and acquiring the element information as sub-information extracted from the element information. An element information conversion unit that changes the information to substantially match the added information, and a code included in the main information, the shape of which has a characteristic indicated by the element information changed by the element information conversion unit. It is characterized by comprising a main information conversion unit for converting, and a main information output unit for outputting an array of codes indicated by the main information converted by the main information conversion unit.

According to such an information embedding device, the additional information embedded in the main information is represented as a relative difference between the shapes of a plurality of codes included in the main information. Therefore,
Even in an image obtained by enlarging, reducing, or facsimile transmitting an image representing an arrangement of codes output by the information embedding device, the relative difference in the shape of these codes is not lost. For this reason, the additional information can be normally restored without using the standard image from the image obtained by enlarging, reducing, or facsimile transmitting the image representing the arrangement of codes output by the information embedding device.

The element information may indicate, for example, the size of a code included in the main information. In this case, the sub-information only needs to indicate, for example, the magnitude relation of the plurality of codes.

[0014] The element information may indicate an area of a predetermined figure substantially enclosing a code included in the main information with a minimum area. In this case, the sub information includes a plurality of the predetermined information. What is necessary is just to show the magnitude relation of the area of the figure. In this case, the element information conversion unit may further determine that the element information is such that the sub-information extracted from the element information substantially matches the additional information acquired by itself, and If the change amount of the area is changed so as to be the minimum under a predetermined condition, the change in the shape of the code due to the embedding of the additional information is reduced, and it is unlikely that a visual discomfort occurs.

In the case where the element information indicates an area of a predetermined figure substantially enclosing a code included in the main information with a minimum area, the sub-information may include a magnitude of an area of the plurality of predetermined figures. When the relationship is classified into a plurality of types, it indicates which type the type belongs to, and each type may be associated with a predetermined value. In this case, the element information conversion unit converts the element information into each type in which the sub-information extracted from the element information is associated with substantially the same value as the value of the additional information acquired by itself. Means for storing a plurality of conversion candidates representing a change amount of the area of the plurality of predetermined graphics changed to be a minimum under predetermined conditions, and among the conversion candidates, Means for identifying the smallest amount of change in the area of the plurality of predetermined graphics, and changing the element information to the one indicated by the identified conversion candidate. A change in the shape of the code due to the embedding is reduced, and a method that is less likely to cause visual discomfort is efficiently specified, and then the embedding of the additional information is executed.

An information reading apparatus according to a second aspect of the present invention obtains main information including an array of codes and generates element information indicating characteristics of the shape of the codes included in the obtained main information. An information extraction unit, and a sub-information output unit that extracts and outputs sub-information indicating a relative difference between the features of the plurality of codes from the element information.

According to such an information reading device, the additional information embedded in the main information is converted from the image in which the additional information included in the main information is represented as a relative difference between the shapes of a plurality of codes included in the main information. The information is extracted and output.

The element information may indicate, for example, the size of a code included in the main information. In this case, the sub-information may indicate, for example, a magnitude relationship between a plurality of codes. I just need.

The element information may indicate, for example, the area of a predetermined figure which substantially encloses a code included in the main information with a minimum area. In this case, the sub-information may include:
For example, any value may be used as long as it indicates the magnitude relationship between the areas of the plurality of predetermined graphics.

A digital watermarking system according to a third aspect of the present invention obtains main information including an array of codes and generates element information indicating characteristics of the shape of the codes included in the obtained main information. An information extraction unit, from the element information, a sub-information reading unit that extracts sub-information that indicates a relative difference between the features of the shapes of the plurality of codes, and acquires additional information for embedding in the main information, An element information conversion unit that changes the element information so that sub-information extracted from the element information substantially matches the additional information obtained by the element information, and a code included in the main information, A main information conversion unit that converts the information to have the characteristic indicated by the element information changed by the element information conversion unit, and a main information output unit that outputs an array of codes indicated by the main information converted by the main information conversion unit And the element From broadcast, comprising a sub-information output unit that outputs the extracted sub information indicating a relative difference in characteristics of the plurality of the codes, and characterized in that.

According to such a digital watermarking system,
The additional information embedded in the main information is expressed as a relative difference between the shapes of a plurality of codes included in the main information. Accordingly, even in an image obtained by enlarging, reducing, or facsimile transmitting an image representing the arrangement of codes output from the main information output unit, the relative differences in the shapes of these codes are not lost. For this reason, the additional information can be normally restored from an image obtained by enlarging, reducing, or facsimile transmitting the image representing the arrangement of codes output from the main information output unit. Such a digital watermarking system extracts sub-information including additional information from an image in which the additional information embedded in the main information is expressed as a relative difference between the shapes of a plurality of codes included in the main information. And output.

Further, in an information embedding method according to a fourth aspect of the present invention, an element for acquiring main information including an array of codes and generating element information indicating characteristics of the shape of the code included in the obtained main information is provided. Information extraction step, from the element information, sub-information reading step of extracting sub-information indicating a relative difference between the features of the plurality of code shapes, to obtain additional information for embedding in the main information, An element information conversion step of changing the element information so that sub-information extracted from the element information substantially matches the additional information obtained by the element information, and a code included in the main information, A main information conversion step of converting the element information to have the characteristic indicated by the element information changed in the element information conversion step, and an array of codes indicated by the main information converted in the main information conversion step. Comprising a main information output step of, a, and wherein the.

According to such an information embedding method, the additional information embedded in the main information is represented as a relative difference between the shapes of a plurality of codes included in the main information. Therefore,
Even in an image obtained by enlarging, reducing, or facsimile transmitting an image representing an array of codes output by this information embedding method, the relative difference between the shapes of these codes is not lost. For this reason, the additional information is normally restored from an image obtained by enlarging, reducing, or facsimile transmitting an image representing an array of codes output by this information embedding method.

According to a fifth aspect of the present invention, there is provided an information reading method, comprising: obtaining main information including an array of codes; and generating element information indicating characteristics of the shape of the codes included in the obtained main information. An information extraction step; and a sub-information output step of extracting and outputting, from the element information, sub-information indicating a relative difference between the features of the shapes of the plurality of codes.

According to such an information reading method, the auxiliary information including the additional information is extracted from the image in which the additional information embedded in the main information is expressed as a relative difference between the shapes of a plurality of codes included in the main information. The information is extracted and output.

A computer-readable recording medium according to a sixth aspect of the present invention provides a computer which acquires main information including an array of codes, and shows characteristics of the shape of the codes included in the obtained main information. An element information extracting unit that generates element information; a sub information reading unit that extracts sub information indicating a relative difference between a plurality of code shape features from the element information; and an addition for embedding in the main information. An element information conversion unit that acquires information and changes the element information so that sub-information extracted from the element information substantially matches the additional information acquired by the element information; A main information conversion unit that converts a code so that its shape has a feature indicated by the element information changed by the element information conversion unit, and an array of codes indicated by the main information converted by the main information conversion unit. Wherein the main information output unit for force, to by recording a program for functioning.

A computer that executes a program recorded on such a recording medium expresses the additional information embedded in the main information as a relative difference between the shapes of a plurality of codes included in the main information. Therefore, even in an image obtained by enlarging, reducing, or facsimile transmitting an image representing an arrangement of codes output by the computer, the relative difference in the shape of these codes is not lost. For this reason, the additional information can be normally restored from an image obtained by enlarging, reducing, or facsimile transmitting an image representing the arrangement of codes output by the computer.

Further, a computer-readable recording medium according to a seventh aspect of the present invention provides a computer which acquires main information including an array of codes, and shows characteristics of the shape of the codes included in the obtained main information. An element information extraction unit that generates element information; and a sub information output unit that extracts and outputs sub information that indicates a relative difference between a plurality of the code shape features from the element information. Is recorded.

A computer that executes a program recorded on such a recording medium reads an image in which the additional information embedded in the main information is represented as a relative difference in the shape of a plurality of codes included in the main information. The sub information including the additional information is extracted and output.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an information embedding apparatus, an information reading apparatus and an electronic watermark system according to an embodiment of the present invention will be described. An electronic watermark for embedding information indicating copyright in a document and extracting the embedded information is described below. A system will be described as an example with reference to the drawings.

FIG. 1 is a diagram showing a physical configuration of the digital watermarking system. As shown in the figure, this digital watermark system physically includes a control unit 101 and a main storage unit 1.
02, an external storage unit 103, an input unit 104, a scanner 105, a printer 106, and a display unit 107. The control unit 101 is connected to the main storage unit 102, the external storage unit 103, the input unit 104, the scanner 105, the printer 106, and the display unit 107.

The control unit 101 has a CPU (Central Processes).
sing unit) and an external storage unit 10
3 reads out a program stored therein, and in accordance with the processing of this program, an element information extracting unit 13, an element information converting unit 17, a main information reconstructing unit 18, and a sub information reading unit 2 described later
0 and the function of the sub information output unit 21 are executed.

The main storage unit 102 has a RAM (Random Acces
s Memory) and the like, and stores data supplied from the control unit 101, and outputs data stored by itself according to a request issued by the control unit 101. The main storage unit 102 is used as a work area of the control unit 101, and executes functions of an element information storage unit 14 and a sub information storage unit 16, which will be described later.

The external storage unit 103 is composed of a hard disk device or the like, and stores data supplied from the control unit 101, and outputs data stored by itself according to a request issued by the control unit 101. External storage unit 10
3 executes the function of the main information storage unit 12 described later.

The input unit 104 includes a keyboard, a recording medium drive device for accessing a recording medium (for example, a floppy disk or a magneto-optical disk), and the like, and information input by an operator and stored in the recording medium. The supplied information is supplied to the control unit 101. The input unit 104
The function of the sub-information input unit 15 described below is executed.

The scanner 105 reads the front side of the original set in accordance with an instruction from the control unit 101, generates data representing an image of the front side, and supplies the data to the control unit 101. The scanner 105 performs the function of the main information input unit 11.

The printer 106 prints an image represented by data supplied from the control unit 101 to the printer 106 on a sheet of paper or the like. The printer 106 includes a main information output unit 19 described later.
Perform the function of The display unit 107 is a CRT (Cathode Ray).
Tube) etc., and displays an image according to the instruction of the control unit 101 on a display screen provided therein. Display unit 10
7 performs the function of the sub information output unit 21 together with the control unit 101.

The digital watermarking system logically includes a main information input unit 11, a main information storage unit 12, an element information extraction unit 13, and an element information storage unit 14, as shown in FIG. , Sub-information input unit 15, sub-information storage unit 16, element information conversion unit 17, main information reconstructing unit 18, main information output unit 19, sub-information reading unit 20, sub-information output unit 2,
1.

The main information input unit 11 reads the front side of the document of the document into which the sub-information is to be embedded, creates image data representing the image of the document, and supplies the created image data to the main information storage unit 12 I do. The main information storage unit 12 stores the image data supplied from the main information input unit 11, and stores the element information extraction unit 13, the main information reconstruction unit 18, and the main information output unit 1.
9 outputs the image data stored therein in accordance with the request sent from 9.

The element information extraction unit 13 is a main information storage unit 12
Requesting the output of the image data stored in the main information storage unit 12, obtaining the image data output by the main storage storage unit 12, and obtaining, from the image data, characters included in a document represented by the image data (I.e., main information) is extracted, and element information indicating a feature of the shape of the main information is generated. Then, the generated element information is supplied to the element information storage unit 14.

The element information is, for example, as shown in FIGS.
As shown in the figure, the positions of the characters included in the document on the document surface (specifically, for example, on a rectangular coordinate system having arbitrarily set x and y axes in the document surface as shown (X and y coordinates of the character) and information indicating the width and height of the character.

The element information storage unit 14 stores the element information extraction unit 1
3 and stores the element information supplied from the element information conversion unit 1.
7 updates the element information stored by itself. Further, the element information storage unit 14 outputs the element information stored by itself according to the request sent from the main information reconstructing unit 18 or the sub information reading unit 20.

The sub-information input unit 15 reads the copyright code to be embedded in the document and supplies it to the sub-information storage unit 16. The copyright code is data for proving that the copyright of the document belongs to a specific person, and is composed of, for example, a decimal number having a predetermined number of digits. Sub-information storage unit 1
Reference numeral 6 stores the copyright code supplied from the sub-information input unit 15 and outputs the copyright code stored by itself according to the request sent from the element information conversion unit 17 or the sub-information output unit 21.

The element information conversion unit 17 includes a sub information storage unit 16
The sub-information storage unit 16 sends a request to output the copyright code stored in the sub-information storage unit 16 to obtain the copyright code output by the sub-information storage unit 16. In addition, the element information conversion unit 17
A request is sent to the element information storage unit 14 to output the element information stored in the element information storage unit 14, and the element information output by the element information storage unit 14 is acquired.

Then, the element information conversion unit 17 performs the operation described later, and extracts the sub information described later based on the element information acquired by itself. Further, based on the extracted sub-information and the acquired copyright code, the following operation is performed to determine how to update the element information stored in the element information storage unit 14. The element information storage unit 14 updates the information.
Send a request to

The main information reconstructing unit 18 stores the element information storing unit 1
A request is sent to the element information storage unit 14 to output the element information stored in the element information storage unit 14, and the element information output by the element information storage unit 14 is obtained. Then, the main information storage unit 1 determines to update the image data stored in the main information storage unit 12 so as to have the characteristic indicated by the element information acquired by itself, and updates the image data according to the determination result.
Send request to 2.

The main information output unit 19 is provided with the main information storage unit 12
Sends a request to output the image data stored in the main information storage unit 12, obtains the image data output by the main information storage unit 12, and prints the image represented by the obtained image data on paper or the like. .

The sub-information reading section 20 sends a request to the element information storage section 14 to output the data stored in the element information storage section 14, and acquires this data output from the element information storage section 14. Then, the sub information is extracted from the acquired data, and the extracted sub information is supplied to the sub information storage unit 16.

The sub information output unit 21 is provided with the sub information storage unit 16
The sub-information storage unit 16 sends a request to output the copyright code stored therein, obtains the copyright code output by the sub-information storage unit 16, and displays an image representing the obtained copyright code. .

(Operation) Next, the operation of the digital watermarking system will be described. (Operation for embedding copyright code) First, the main information input unit 1
The scanner 105 performing the first function scans the front side of the document of the document in which the sub-information is to be embedded, creates image data representing an image of the document, and supplies the created image data to the main information storage unit 12 . The main information storage unit 12 stores the image data supplied from the main information input unit 11.

Next, the element information extracting unit 13 sends a request for outputting the image data stored in the main information storing unit 12 to the main information storing unit 12, and the main information storing unit 12 Output data. Then, the element information extraction unit 13 acquires the image data output by the main information storage unit 12 and generates element information indicating the characteristic of the shape of the character, which is the main information represented by the acquired image data.

More specifically, the element information extraction unit 13 performs, for example, character recognition on the acquired image data, and determines the position and shape of each character included in the image data and the scanner 105.
Identifies the order in which each of these characters is arranged in the read document. Next, for each of the identified characters, the element information extraction unit 13 determines the width and height of a rectangle surrounding the character with a minimum area (that is, the width and height of the character) based on the shape of the character identified by itself. ) Is generated.

Then, the element information extraction unit 13 supplies the generated element information to the element information storage unit 14. When supplied with the element information from the element information extraction unit 13, the element information storage unit 14 stores the element information.

On the other hand, the operator operates the keyboard of the input unit 104 that performs the function of the sub-information input unit 15 to input a copyright code, or to input a recording medium on which a copyright code has been recorded in advance. The copyright code is input by setting it in the recording medium driver 104 and causing the recording medium drive to read the copyright code recorded on the recording medium. The input copyright code is input unit 1
The information is supplied from the keyboard 04 to the sub-information storage unit 16. The sub information storage unit 16 stores the copyright code supplied from the sub information input unit 15.

Next, the element information conversion unit 17 sends a request to the sub information storage unit 16 to output the copyright code stored in the sub information storage unit 16. The sub-information storage unit 16 outputs the copyright code stored by itself according to this request,
The element information conversion unit 17 acquires the output copyright code. Then, the element information conversion unit 17 converts the obtained copyright code into a binary number. The element information conversion unit 17
Sends a request to the element information storage unit 14 to output the element information stored in the element information storage unit 14. The element information storage unit 14 outputs the element information stored by itself in accordance with the request, and the element information conversion unit 17 acquires the output element information.

The element information conversion unit 17 generates an array of character strings consisting of three characters by dividing the array of each character indicated by the obtained element information by three characters from the beginning. Then, a logical value of either “1” or “0” is associated with each character string according to a predetermined rule.

Specifically, for example, the element information conversion unit 17 determines, for each character string, the area of a rectangle surrounding the first character of the character string with a minimum area (ie, the product of the width and height of the rectangle).
Is Sa, the area of the rectangle surrounding the second character with the minimum area is Sb, the area of the rectangle surrounding the third character with the minimum area is Sc, and when Sa = Sb = Sc (for pattern 0), When Sa = Sb> Sc (in the case of pattern 1), logical value “1” is associated,
When Sb = Sc> Sa (pattern 2), a logical value “1” is associated, and when Sc = Sa> Sb (pattern 3), a logical value “1” is associated, and Sa> Sb =
When Sc (pattern 4), logical value "1" is associated, when Sb> Sc = Sa (pattern 5), logical value "1" is associated, and when Sc> Sa = Sb ( Pattern 6) is associated with a logical value “1”, and Sa> S
When b> Sc (pattern 7), the logical value “0” is associated, when Sb>Sc> Sa (pattern 8), the logical value “0” is associated, and when Sc>Sa> Sb At the time (at the time of pattern 9), the logical value “0” is associated, and S
When a>Sc> Sb (pattern 10), the logical value “0” is associated, and when Sb>Sa> Sc (pattern 11), the logical value “0” is associated. Sc> Sb
If> Sa (pattern 12), the logical value “0” is associated.

However, when comparing the areas of two rectangles each surrounding two characters with a minimum area, the element information conversion unit 17 determines that the area is strictly set if the difference between the areas is within a predetermined range. Even if they are not equal, they are treated as having equal areas.

When a logical value is associated with each character string, the element information conversion unit 17 arranges the bits indicating each logical value in data (hereinafter, referred to as an array) of the character string to which each bit is associated. (Referred to as sub-information).

Next, the element information conversion section 17 starts from a predetermined position of the sub-information (for example, the head of the sub-information) and has the same number of consecutive digits as the binary number of the copyright code acquired by itself and converted to a binary number. The part containing the logical value to be extracted is extracted. The logical value of each bit included in the extracted portion of the sub information is substantially different from the logical value of the bit forming the same digit of the copyright code converted into a binary number. Identify something. Then, it is determined whether the specified bit indicates a logical value associated with any of the above-described character strings obtained by dividing the array of characters constituting the main information.

Next, the element information conversion unit 17 enlarges or reduces the width and height of the character included in the determined character string, and sets the logical value associated with the character string to a value different from the current value. In the case where the total value of the change amount of the area of each rectangle surrounding each of the three characters included in the character string with the minimum area becomes the minimum under a predetermined condition, , One based on the element information representing the character string.

Specifically, for example, the logical value of the most significant bit of the copyright code converted into a binary number is “0”,
On the other hand, as shown in FIG. 3A, of the three characters constituting the character string associated with the first bit in the portion extracted from the sub-information by the element information conversion unit 17, the width of the first character Is 28 pixels, the height is 28 pixels, the width of the second character is 30 pixels, the height is 30 pixels, and the width of the third character is 29 pixels and the height is 26 pixels. However, in the present specification and drawings,
Each character is composed of pixels arranged in a matrix in any two colors such as black and white. Then, a predetermined unit length representing the outer diameter of the pixel is set to one pixel (pixe
l), and a length n times the unit length (n is an arbitrary positive number) is n pixels. In this case, the character string composed of these three characters belongs to the above-described pattern 5, and therefore, this character string is associated with the logical value “1”.

At this time, in order to make the character string a pattern that can be associated with the logical value “0”, the character string must be
Any of patterns 0, 7, 8, 9, 10, 11, or 12 may be used. In this case, the element information conversion unit 17 first determines whether or not the width and height of characters included in the character string are to be changed to pattern 0 and patterns 7 to 12, respectively. Are specified when the total value of the variation in the area of each rectangle surrounding each of the three characters included in. Then, from the specified cases, one having the smallest total change amount of the areas of the rectangles each surrounding the three characters included in the character string with the minimum area is specified.

For example, the element information conversion unit 17 may change the width and height of at least one of the three characters included in the character string in units of one pixel, and form two rectangles surrounding these characters with a minimum area. Is 90 square pixels (ie, 90 times the area of a square with one pixel on each side)
If they are less than, it is considered that both rectangles have the same area. "
First, (1): the second character is reduced to 29 pixels wide and 29 pixels high so that the character string belongs to pattern 0. (2): The first character is The character string is enlarged to 32 pixels wide and 32 pixels high so that the character string belongs to pattern 7. (3) The first character is reduced to 25 pixels wide and 25 pixels high, and the character string is changed to pattern 8 (4): The second character is reduced to 26 pixels in width and 26 pixels in height, and the third character is expanded to 32 pixels in width and 29 pixels in height. (5): The first character is enlarged to 29 pixels wide and 29 pixels high, and the second character is reduced to 25 pixels wide and 25 pixels high. To belong to pattern 10, 6): The third character is reduced to 27 pixels wide and 24 pixels high so that the character string belongs to the pattern 11. (7): The third character is 33 pixels wide and 30 pixels high. To specify that the character string belongs to the pattern 12 and store information in an arbitrary format representing these cases.

Next, the element information conversion unit 17 determines that, among the seven stored cases, the total value of the change in the area of the rectangle surrounding each of the three characters included in the character string with the minimum area is the minimum. The case of the above (1) is specified.

In the case where the logical value associated with the character string is different from the current value, the total value of the change in the area of each rectangle surrounding each of the three characters included in the character string with the minimum area is a predetermined value. Specifying one case that is the smallest under the conditions,
The element information conversion unit 17 determines to update the width and height of each character constituting the character string so as to conform to the specified case. For example, when the specified case is the case of the above (1), the element information conversion unit 17 converts the second character of the characters forming the character string into the width as shown in FIG. Decide to reduce to 29 pixels and 29 pixels high.

When it is determined how to update the width and height of each character constituting the character string for all the character strings constituting the main information, the element information conversion unit 17
Sends a request to the element information storage unit 14 to update the element information according to the determination result, and the element information storage unit 14 updates the element information stored by itself in accordance with the request.
For example, the element information conversion unit 17 converts the second character of the character string constituting the head character string included in the main information into the width 2
When it is determined to reduce the size to 9 pixels and the height to 29 pixels, as shown in FIG. 3B, the information indicating the width and the height of the second character is updated so as to represent 29 pixels.

Next, the main information reconstructing unit 18 sends a request to the element information storage unit 14 to output the updated element information stored in the element information storage unit 14, and the element information storage unit 14 In response to this request, the updated element information stored by itself is output, and the main information reconstructing unit 18 acquires the output element information. Then, the main information reconstruction unit 18
Sends a request to the main information storage unit 12 to change the height and width of each character forming the main information as indicated by the acquired changed element information. The main information storage unit 12 updates the image data stored therein according to the request.

When the image data is updated, the main information output unit 1
9 sends a request to the main information storage unit 12 to output the image data stored in the main information storage unit 12, and the main information storage unit 12 outputs the image data stored by itself according to the request. . The main information output unit 19 acquires the output image data, and has each character represented by the image data at a position indicated by the acquired image data, and has a width and a height indicated by the acquired image data. In this way, printing is performed on paper or the like.

By the operation described above, the digital watermark system associates the character string included in the image data with the sub-information and changes the image data so that the sub-information indicates the copyright code (ie, the copyright is added to the image data). A right code is embedded), and a document having a text in which the copyright code is embedded is created.

(Operation for Reading Copyright Code) When reading a copyright code from a document in which the copyright code is embedded in the text, the scanner 10 that performs the function of the main information input unit 11
5 reads the surface of the document in which the copyright code is embedded, creates image data representing an image of the read document, and supplies the image data to the main information storage unit 12. The main information storage unit 12 stores the image data.

Next, the element information extraction unit 13 sends a request for outputting image data to the main information storage unit 12, and the main information storage unit 12 outputs the image data stored by itself, and The unit 13 acquires this image data.
The element information extraction unit 13 extracts element information indicating the characteristic of the shape of each character constituting the main information represented by the acquired image data in substantially the same procedure as the above-described procedure, and extracts the extracted element information. Is supplied to the element information storage unit 14. The element information storage unit 14 stores this element information.

Next, the sub-information reading unit 20 sends a request to the element information storage unit 14 to output the element information, and the element information storage unit 14 outputs the element information stored by itself in accordance with the request. The sub-information reading unit 20 acquires the element information, and extracts the sub-information from the element information acquired by itself by substantially the same procedure as the above-described procedure performed by the element information conversion unit 17. Further, the sub-information reading unit 20 extracts, from a predetermined position of the extracted sub-information, a continuous portion having the same number of digits of the copyright code converted into a binary number, thereby obtaining the copyright included in the sub-information. Get the code. Then, the sub-information reading unit 20 supplies the extracted copyright code to the sub-information storage unit 16. The sub information storage unit 16 stores the supplied copyright code.

Next, the sub-information output unit 21 sends a request to the sub-information storage unit 16 to output the copyright code stored in the sub-information storage unit 16. And outputs the copyright code stored therein. The sub-information output unit 21 acquires the copyright code and displays the acquired copyright code on its own display screen. By the operation described above, the digital watermark system extracts and displays a copyright code from textual image data in which the copyright code is embedded.

Note that the digital watermarking system according to this embodiment is not limited to the above-described embodiment.
Various modifications and applications are possible. For example, the information to be embedded in the text need not be a copyright code, but may be information for proving that the text is genuine,
Other arbitrary information may be used. Further, the characters included in the text need not be composed of pixels.

When the digital watermark system does not perform the operation of reading the copyright code, it is not necessary to provide a part or all of the sub-information reading unit 20 and the sub-information output unit 21. When the digital watermarking system does not perform the operation of embedding the copyright code, a part or all of the sub information input unit 15, the element information conversion unit 17, the main information reconstructing unit 18, and the main information output unit 19 There is no need to provide.

The document into which the copyright code or the like is to be embedded does not need to include characters, but may be any document in which any visible code is described. For example,
The document into which the copyright code or the like is embedded may be a musical score. In this case, for example, a group composed of a plurality of notes is treated substantially the same as the above-described character string, and a predetermined portion of these notes (for example, a “ball” portion of a note,
In other words, the portion representing the scale of the note) may be treated substantially the same as the characters constituting the character string described above.

The number of codes included in a character string or the like constituting main information does not need to be three, but may be any number equal to or more than two. Further, the codes included in the character strings and the like constituting the main information need not be adjacent to each other on the text image, and may include any codes in the document.

Further, in the above-described embodiment, the logical value of the bit forming the sub-information is determined by the size of a rectangle surrounding each of a plurality of codes forming a character string or the like associated with the bit with a substantially minimum area. The decision was based on the relationship. However, the logical value of the bit may be determined based on any criterion as long as it is determined according to the type of the relative difference between the shapes of the plurality of codes. Therefore, the logical value of the bit may be determined based on, for example, the magnitude relationship between the height and the width of each code.

The logical values of the bits constituting the sub-information need not be binary logical values, but may be three or more. Further, the correspondence between the logical values of the bits forming the sub information and the types of the relative differences in the shapes of the plurality of codes forming the main information is also arbitrary.

However, in order to minimize the total value of the change in the area of each of the rectangles enclosing each code included in the character string or the like constituting the main information with a minimum area under predetermined conditions, the width of each code is determined. When changing the height or height, in order to reduce the visual discomfort associated with this change, character strings etc. that are associated with different logical values must have visually similar shapes. Is desirable.

For example, the above-mentioned pattern 3 and pattern 10
Thus, different logical values are associated with a set of patterns that are not different from each other except for the size relationship between the areas of the two rectangles that respectively surround the first character and the third character with the minimum area. For example, a character string classified into one of the pattern 3 and the pattern 10 has a different logical value from the conventional one if the width or height of either the first character or the third character is changed. Corresponds to bits.

The text on which the copyright code or the like is to be embedded or the text from which the copyright code or the like is to be read need not be printed on paper or the like. May be read from a recording medium or the like in which the image data representing the image data is recorded in advance, and stored in the main information storage unit 12. In this case, the digital watermarking system does not necessarily need to include the scanner 105.

The element information extracting section 13 may extract sub-information based on the element information generated by itself, and the element information storing section 14 stores the element information in addition to the element information.
3 may store the extracted sub-information. In this case, the element information conversion unit 17 does not need to extract the sub information, and may read the sub information from the element information storage unit 14.

Although the embodiments of the present invention have been described above, the information embedding device, the information reading device, and the digital watermarking system of the present invention can be realized by using a general computer system without using a dedicated system. . For example, by installing the program from a medium (floppy disk, CD-ROM, or the like) storing a program for executing the above-described operation in a personal computer, a digital watermarking system that executes the above-described processing can be configured. it can.

The medium for supplying the program to the computer may be a communication medium (a medium that temporarily and fluidly stores the program, such as a communication line, a communication network, or a communication system). For example, the program may be posted on a bulletin board (BBS) of a communication network and distributed via the network. The program may be supplied by distributing a modulated wave obtained by modulating a carrier wave by the program.
Then, by starting this program and executing it in the same manner as other application programs under the control of the OS, the above-described processing can be executed.

When the OS shares a part of the processing,
Alternatively, when the OS constitutes a part of one component of the present invention, a program excluding the part may be stored in the recording medium. Also in this case, in the present invention, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.

[0088]

As described above, according to the present invention, there is provided a digital watermark system capable of reliably and easily reproducing information from an image in which information is embedded without using a standard image even if the image changes. An information embedding device, an information reading device, an information embedding method, and an information reading method are realized to constitute such a digital watermarking system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a physical configuration of a digital watermarking system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a logical configuration of the digital watermarking system of FIG. 1;

FIG. 3A is a diagram schematically illustrating the shape and element information of a character before a change, and FIG. 3B is a diagram schematically illustrating the shape and element information of a character after a change.

[Explanation of symbols]

 101 control unit 102 main storage unit 103 external storage unit 104 input unit 105 scanner 106 printer 107 display unit 11 main information input unit 12 main information storage unit 13 element information extraction unit 14 element information storage unit 15 sub information input unit 16 sub information storage Unit 17 element information conversion unit 18 main information reconstructing unit 19 main information output unit 20 sub information read unit 21 sub information output unit

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Osamu Iwaki 3-3-3 Toyosu, Koto-ku, Tokyo F-term in NTT Data Corporation (reference) 5B057 AA11 BA02 CA02 CA06 CA12 CA16 CB02 CB06 CB12 CB16 CC03 CE08 CE09 CG07 DA08 DA17 DC04 DC36 5C076 AA02 AA14 AA40 BA06 5J104 AA14 NA27

Claims (12)

[Claims] An element information extraction unit configured to acquire main information including an array of codes and to generate element information indicating characteristics of a shape of the code included in the obtained main information; A sub-information reading unit that extracts sub-information indicating a relative difference in the shape characteristic of the sub-information, and acquires additional information for embedding in the main information, and extracts the element information from the sub-information extracted from the element information. However, the element information conversion unit that changes so that it substantially matches the additional information obtained by itself, and the code included in the main information is indicated by the element information whose shape has been changed by the element information conversion unit An information embedding device, comprising: a main information conversion unit that converts to have a characteristic; and a main information output unit that outputs an array of codes indicated by the main information converted by the main information conversion unit. 2. The method according to claim 1, wherein the element information indicates a size of a code included in the main information, and the sub-information indicates a magnitude relationship between a plurality of the codes. Item 2. An information embedding device according to Item 1. 3. The element information indicates an area of a predetermined graphic substantially enclosing a code included in the main information with a minimum area, and the sub information indicates an area of a plurality of the predetermined graphic. The element information conversion unit indicates that the sub-information extracted from the element information substantially matches the additional information acquired by itself, and The information embedding device according to claim 2, wherein the amount of change in the area of the figure is changed to be a minimum under a predetermined condition. 4. The element information indicates an area of a predetermined figure substantially enclosing a code included in the main information with a minimum area, and the sub-information indicates an area of a plurality of the predetermined figures. When the magnitude relationship is classified into a plurality of types, it indicates which type it belongs to. Each of the types is associated with a predetermined value, and the element information conversion unit converts the element information into , The sub-information extracted from the element information is
It belongs to each of the types associated with substantially the same value as the value of the additional information acquired by itself, and the amount of change in the area of the plurality of predetermined figures is minimized under predetermined conditions Means for storing a plurality of conversion candidates representing the changed one, and specifying, from among the conversion candidates, a conversion amount of the plurality of predetermined figures having the smallest change amount, and identifying the element information. Means for changing to the one indicated by the conversion candidate,
The information embedding device according to claim 3, comprising: 5. An element information extracting unit for acquiring main information including an array of codes, and generating element information indicating characteristics of a shape of a code included in the obtained main information; And a sub-information output unit that extracts and outputs sub-information indicating a relative difference between the features of the shape. 6. The information processing apparatus according to claim 1, wherein the element information indicates a size of a code included in the main information, and the sub information indicates a magnitude relationship between a plurality of the codes. Item 6. An information reading device according to item 5. 7. The element information indicates an area of a predetermined graphic substantially enclosing a code included in the main information with a minimum area, and the sub information indicates an area of a plurality of the predetermined graphic. 7. The information reading device according to claim 6, wherein the information reading device indicates a magnitude relationship. 8. An element information extraction unit for acquiring main information including an array of codes, and generating element information indicating characteristics of the shape of the code included in the obtained main information; A sub-information reading unit that extracts sub-information indicating a relative difference in the shape characteristic of the sub-information, and acquires additional information for embedding in the main information, and extracts the element information from the sub-information extracted from the element information. However, the element information conversion unit that changes so that it substantially matches the additional information obtained by itself, and the code included in the main information is indicated by the element information whose shape has been changed by the element information conversion unit A main information conversion unit that performs conversion to have a characteristic; a main information output unit that outputs an array of codes indicated by the main information converted by the main information conversion unit; Show relative differences It includes a sub-information output unit to output the extracted information, the electronic watermark system, characterized in that. 9. An element information extracting step of obtaining main information including an array of codes, and generating element information indicating characteristics of the shape of the code included in the obtained main information; A sub-information reading step of extracting sub-information indicating a relative difference between the features of the shape; acquiring additional information for embedding in the main information; and extracting the element information from the sub-information extracted from the element information. The element information conversion step of changing the element information so that it substantially matches the additional information acquired by itself, and the code included in the main information is indicated by the element information whose shape has been changed in the element information conversion step. A main information conversion step of performing conversion so as to have a characteristic, and a main information output step of outputting an array of codes indicated by the main information converted in the main information conversion step. Information embedding method to. 10. An element information extracting step of obtaining main information including an array of codes, and generating element information indicating characteristics of the shape of the code included in the obtained main information; A sub-information output step of extracting and outputting sub-information indicating a relative difference between the features of the shape of the information. 11. A computer, comprising: an element information extraction unit configured to obtain main information including an array of codes and generate element information indicating characteristics of a shape of a code included in the obtained main information; A sub-information reading unit for extracting sub-information indicating a relative difference between the features of the shape of the code, acquiring additional information for embedding in the main information, and extracting the element information from the element information. An element information conversion unit that changes the sub-information to substantially match the additional information obtained by itself, and an element whose code included in the main information has its shape changed by the element information conversion unit. A main information conversion unit for converting the information to have a characteristic indicated by the information; a main information output unit for outputting an array of codes indicated by the main information converted by the main information conversion unit; did Computer readable recording medium. 12. A computer, comprising: an element information extraction unit configured to obtain main information including an array of codes and generate element information indicating characteristics of a shape of a code included in the obtained main information; A sub-information output unit for extracting and outputting sub-information indicating a relative difference between the features of the code shape; and a computer-readable recording medium storing a program for causing the sub-information to function.