JP2002232694A - Watermark information embedding device and watermark information extracting device for digital watermark - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a digital watermark technique for embedding watermark information in a vector image. A watermark information embedding apparatus acquires vector data which is a column of vector data elements including a graphic type and a color attribute indicating a color of the graphic, and sets the graphic type to a line segment (L).
Ine), the largest value of the color attribute value of the vector data element is determined as the first specific value, and the value indicating the color B similar to the color A indicated by the first specific value is determined as the second specific value. One bit from the first bit of the bit string to be embedded is assigned to each of a plurality of vector data elements whose type is Line and the value of the color attribute is the first specific value or the second specific value in the order of the column, The image represented by the vector data is updated by updating the color attribute of the element so that if the assigned 1 bit is 0, the first specific value is obtained, and if the assigned 1 bit is 1, the second specific value is obtained. A bit string is embedded as a digital watermark in the.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called digital watermarking technique, and more particularly to a technique for embedding other information as a digital watermark in graphic drawing data such as map data, that is, so-called vector data, and a technique for embedding digital information in a digital image. The present invention relates to a technique for extracting watermark information.

[0002]

2. Description of the Related Art In recent years, with the rapid spread of use of the Internet and the like, digital images have been frequently provided, distributed, received, and used among public institutions, companies, individuals, and the like. Since digital images can be easily duplicated during the distribution process, development of copyright protection technology for images is desired. One of the copyright protection technologies is to protect the image by the creator so that the image cannot be seen by human eyes. Digital watermark technology for embedding information such as names has attracted attention. Hereinafter, information embedded in an image is referred to as watermark information.

[0003] Most of the conventional digital watermarking techniques are for photographic images, and basically, an image is regarded as a set of M pixel data in the horizontal direction and N pixel data in the vertical direction.
This is a technique for embedding watermark information in an image by slightly changing the value of each pixel data under a specific rule.

[0004]

By the way, not only a photographic image but also an image represented by so-called vector data such as a map image (hereinafter referred to as a "vector image") is exchanged through a recording medium, the Internet or the like. May be the subject of strategic transactions. Vector data is a set of sets of information indicating the type of figure such as a line segment, a circle, and a polygon and information indicating the form of the figure, such as size and color. Image data.

Although the need for copyright protection is high for this vector image, the conventional digital watermarking technique for photographic images cannot be applied to vector images. For this reason,
The urgent development of digital watermark technology applicable to vector images is desired. Therefore, an object of the present invention is to provide a digital watermark technique for embedding watermark information in a vector image.

[0006]

In order to solve the above-mentioned problems, a watermark information embedding device according to the present invention comprises a set of vector data elements including a figure type and a form attribute indicating the form of a figure. A watermark information embedding device that embeds bit data as an electronic watermark in vector data to be represented, a vector data acquisition unit that acquires vector data, a bit data acquisition unit that acquires bit data,
Embedding means for embedding the bit data in the vector data by changing the value of the morphological attribute included in some vector data elements constituting the obtained vector data according to the bit data. Features.

[0007] With the above configuration, it is possible to embed watermark information in vector data for drawing the vector image as a digital watermark to the vector image. Further, the watermark information extracting apparatus according to the present invention extracts the bit data from vector data including a set of vector data elements including a figure type and a form attribute indicating a form of the figure and in which bit data is embedded as an electronic watermark. Data extraction means for obtaining vector data in which bit data is embedded, and a bit based on a value of a morphological attribute included in a plurality of vector data elements constituting the obtained vector data. Extracting means for extracting data.

[0008] With the above arrangement, the watermark information embedding apparatus converts the form of the graphic constituting the vector image within an approximate range based on a predetermined criterion to convert the watermark information from the vector image into which the watermark information is embedded. It can be extracted and used.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a watermark information embedding device according to an embodiment of the present invention will be described. <Configuration of Watermark Information Embedding Apparatus> FIG. 1 is a functional block diagram of a watermark information embedding apparatus 100 according to an embodiment of the present invention.

The watermark information embedding device 100 is a device for embedding information as a digital watermark in a vector image such as a map image, and is composed of a computer including a CPU, a memory, a hard disk, a keyboard, and the like in terms of hardware. Functionally, as shown in the figure, a vector data acquisition unit 101, a vector data storage unit 102, an embedding target color A specifying unit 103, an embedding target color B determination unit 104, a watermark information acquisition unit 105, and an embedding unit 106 And a vector data output unit 107.

Here, the vector data acquisition unit 101
A data file for drawing a vector image (hereinafter, referred to as a “vector data file”) is obtained from a recording medium such as a hard disk or an external network, and the vector data as the file contents is stored in the vector data storage unit 102. Has functions. This vector data file is a file created by, for example, so-called draw-based software. In this example, a map image is formed by two bits of red (Red) such as a line segment, a circle, and a polygon, and green (Gre
(en) 4 bits and blue (Blue) 2 bits, that is, a total of 8 bits, that is, vector data represented by a set of graphics represented by 256 colors, in a file format.

The vector data storage section 102 is an area of a memory for storing vector data. Less than,
Data of each figure among vector data is called a vector data element. Vector data for drawing a map image generally includes a plurality of vector data elements. The embedding target color A specifying unit 103 includes the vector data storage unit 10.
2 by referring to each vector data element stored in the second color (hereinafter, referred to as one color to be embedded with watermark information).
Called "color A". ).

The embedding target color B determining unit 104 has a function of determining a color (hereinafter, referred to as “color B”) similar to the color A specified by the embedding target color A specifying unit 103. The watermark information acquiring unit 105 has a function of acquiring watermark information input by a user or already recorded on a recording medium such as a hard disk, and transmitting the acquired watermark information to the embedding unit 106. Note that the obtained watermark information is a bit string.

[0014] The embedding unit 106 is a vector data storage unit 1
02 is a vector data element relating to a line (Line) among the vector data elements stored in the color A, and the value of an attribute (line color attribute) relating to a line color included in the vector data element is a specific one color. Alternatively, for a vector data element indicating one of the colors B that is a color similar to the color A, the value of the line color attribute is set to the watermark information acquisition unit 1.
It has a function of changing to color A or color B in accordance with the watermark information transmitted from 05, that is, a function of actually embedding watermark information in a vector image.

The vector data output unit 107 is stored in the vector data storage unit 102, and the embedding unit 1
06, the function is to convert the vector data into which the watermark information has been embedded into a file format, and output the vector data to the outside of the watermark information embedding apparatus 100 as a vector data file. The output destination is a recording medium such as a hard disk or an external network.

The vector data obtaining unit 101, embedding target color A specifying unit 103, embedding target color B determining unit 104, watermark information obtaining unit 105, embedding unit 106, and vector data output unit 107 are stored in a memory. The function is realized by executing the control program executed by the CPU. <Data Handled by Watermark Information Embedding Apparatus> FIG. 2 is a diagram showing an example of a map image drawn based on a vector data file input to the watermark information embedding apparatus 100.

The map image shown in FIG. 1 is a city map around the station No. 2, where land divisions, tracks, buildings, and the like are represented by figures such as line segments and polygons. FIG. 3 is a diagram showing an example of the contents of a vector data file input to the watermark information embedding device 100. In the figure, vector data file 3
Each vector data element, which is the content of a part of 00, is represented one by one in one row. Rows 301-30
3, line 305, line 306, lines 308-311 and line 31
Reference numerals 3 to 316 denote vector data elements representing line segments (Line). Lines 304 and 312 are rectangles (Rectan
gle). Line 3
Reference numeral 07 denotes a vector data element representing a circle.

A map image as shown in FIG. 2 is represented by a set of these vector data elements. The vector data element has a data structure including a graphic type and a graphic attribute. Graphic type is Line, Rec
Tangle, Circle, or the like.

The graphic attribute has a unique structure for each graphic type. For example, Line is two ends of a line segment.
The coordinates of the point in the two-dimensional coordinate space and R
The line color attribute is represented by a total of 8 bit values of ed2 bits, Green4 bits, and Blue2 bits. For example, Rectangle includes coordinates of two diagonal points on a two-dimensional coordinate space, a line color attribute, and a color attribute (region color attribute) of an internal region surrounded by a rectangular line. Note that the region color attribute is also represented by a total of 8 bits of RGB similarly to the line color attribute. Also, if this 8-bit value is 0x00, black,
0xff represents white.

Therefore, for example, the row 301 has the coordinates (10,
This is a line segment connecting the point of 10) and the point of coordinates (20, 11), and has a line color attribute value of 0x3F, that is, a line segment of light blue. Further, the row 304 includes the coordinates (100, 10).
And a rectangle having a line color attribute of 0x3F, that is, light blue, and a region color attribute of 0x3C, that is, light green.

FIG. 4 is a diagram showing the relationship between colors A and B to be embedded with watermark information for an 8-bit value indicating a line color attribute. As shown in the figure, the 8-bit value obtained by inverting the least significant bit of Green in the 8-bit value 31 for the color A becomes the 8-bit value 32 indicating the color B. For an 8-bit value 32 for color A, Red,
When the least significant bit of Green, which is a color element expressed using the most bits in Green and Blue, is inverted, an 8-bit value 32 indicating Color B in which the Green component of Color A has slightly changed is obtained. Therefore, the color A and the color B are similar colors. <Operation of Watermark Information Embedding Device> The operation of the watermark information embedding device 100 will be described below.

FIG. 5 is a flowchart showing the operation of the watermark information embedding device 100. Hereinafter, "Elizabe
th ", a nine-character string representing the author name
0x45, 0x6C, 0 in ASCII code in bytes
x69,..., 0x68, and embedding a vector image represented by a vector data file having the contents illustrated in FIG. 3 as a watermark information using a bit string of a total of 72 bits in which each ASCII code is arranged from upper bits. Next, the operation shown in FIG. 5 will be described step by step.

First, the vector data acquisition unit 101 of the watermark information embedding device 100 acquires a vector data file to be embedded with watermark information from the outside, and stores the vector data as its contents in the vector data storage unit 102.
(Step S501). As a result, the vector data elements and the like shown in rows 301 to 316 in FIG.

The vector data is stored in the vector data storage 1
02, the embedding target color A specifying unit 103 refers to each vector data element constituting the vector data, and selects one of the colors used as the line color attribute of the vector data element for Line. The color used in the vector data element for the most Line is searched for, and the color, that is, the 8-bit value is determined as the color A (step S).
502). Here, it is assumed that the color represented by 0x3F, which is a bright light blue, is used most (see FIG. 3), and the color represented by 0x3F is determined to be color A. Note that specifying a certain color means specifying a value indicating the certain color.

Here, for simplicity of description, it is assumed that the number of vector data elements more than twice the number of bits of the watermark information is for Line and the line color attribute indicates color A. And After the color A is specified, the embedding target color B determination unit 104 determines a color that is close to the color A as the color B (step S503). That is, the embedding target color B determining unit 104 determines the 8-bit value representing the color B by inverting the third bit from the bottom based on the 8-bit value of the color A as shown in FIG. This allows
0x3B which is the third bit inverted from 0x3F is color B
Is an 8-bit value.

Subsequently, the watermark information acquiring unit 105 acquires the watermark information and transmits it to the embedding unit 106 (step S5).
04). As a result, the watermark information “Elizabe
A 72-bit bit string representing “th” is obtained by the watermark information obtaining unit 105 and transmitted to the embedding unit 106. After specifying the color A, determining the color B, and transmitting the bit string as the watermark information, the embedding unit 106 embeds the bit string into the vector data stored in the vector data storage unit 102 (Step S505)
To S511).

That is, the embedding unit 106 first searches for vector data elements for Line in order from the vector data element corresponding to the head of the vector data file (step S505). After searching one of the vector data elements for the Line, the embedding unit 106 determines whether the value of the line color attribute of the vector data element for the searched Line is an 8-bit value indicating the color A or the color B. If it is neither color A nor color B (step S506), a vector data element for the next Line is searched (step S507), and the process returns to the determination in step S506.

Note that among the vector data elements which are the contents of the vector data file 300 shown in FIG.
The line data attributes of ne for which the line color attribute is 0x3F indicating color A or 0x3B indicating color B are line 301, line 303, line 305, line 308, line 31
0, row 311, row 313, and row 315 vector data elements.

If it is determined in step S506 that the value of the line color attribute of the vector data element for the searched Line is an 8-bit value indicating color A or color B, the embedding unit 106 transmits It is determined whether or not the value of the next bit to be embedded in the bit string of the watermark information is 0 (step S508). The bit string of the watermark information is one bit at a time starting from the first bit.
It is embedded in the line color attribute of each vector data element for Line having a value indicating color A or color B. Therefore, in step S508, it is first determined whether or not the value of the first bit of the bit string is 0.

If it is determined in step S508 that the value of the next bit to be embedded is 0, the embedding unit 106
Updates the line color attribute of the vector data element for the searched Line so as to be an 8-bit value indicating the color A (step S509). If the value of the line color attribute to be updated is an 8-bit value indicating the color A in step S509, the update can be omitted.

If it is determined in step S508 that the value of the next bit to be embedded is not 0, ie, it is 1, the embedding unit 106 sets the line color attribute of the vector data element for the searched Line to the color B (Step S510). In step S510, the value of the line color attribute to be updated is
If the value is an 8-bit value, the update can be omitted.

After performing step S509 or S510, the embedding unit 106 determines whether or not bits that have not been embedded yet remain in the bit string that is the watermark information (step S511). A vector data element for the next Line is searched (Step S507), and the process returns to Step S506.

In step S511, when all the bits of the bit string as the watermark information are embedded, the embedding unit 1
06, the vector data output unit 10
7 outputs all the vector data elements stored in the vector data storage unit 102 as a vector data file (step S512), whereby the operation of the watermark information embedding device 100 is completed.

The contents of the vector data file output in step S512 are “Elizabe
A bit string representing a character string “th” is dispersed and embedded in a vector data element for Line. FIG. 6 is a diagram illustrating the contents of a part of the vector data file 400 output when the vector data file 300 having the contents illustrated in FIG. 3 is input to the watermark information embedding device 100.

In FIG. 6, the watermark information 350 includes a character string "E
lizabeth "
... ". In the figure, each bit of this bit string is a vector data element for a Line, whose line color attribute indicates a color A or a color B in advance,
That is, row 301, row 303, row 305, row 308, row 31
The line color attribute is sequentially associated with the vector data elements of 0, row 311, row 313, and row 315, and the line color attribute is 0x3F indicating color A if the bit value is 0, and color B if the bit value is 1.
Is updated to 0x3B, which indicates the result.

As described above, the watermark information embedding device 100
Can embed watermark information consisting of a bit string such as a character code string that explicitly or implicitly identifies the copyright holder of the vector image. Hereinafter, a watermark information extraction device according to an embodiment of the present invention will be described. <Configuration of Watermark Information Extraction Device> FIG. 7 is a functional block diagram of a watermark information extraction device 200 according to an embodiment of the present invention.

The watermark information extracting device 200 is a device for extracting watermark information from a vector data file for drawing a vector image in which watermark information is embedded as a digital watermark by the watermark information embedding device 100. In terms of hardware, it is composed of a computer having a CPU, a memory, a hard disk, a keyboard, and the like. Functionally, as shown in the figure, a vector data acquisition unit 201, a vector data storage unit 202, an extraction target color A
Specification unit 203, extraction target color B specification unit 204, extraction unit 20
5 and a watermark information output unit 206.

Here, the vector data acquisition unit 201
It has a function of acquiring a vector data file in which watermark information is embedded from a recording medium such as a hard disk or an external network, and storing the vector data as its contents in the vector data storage unit 202. In addition,
It is assumed that the vector data file obtained by the vector data obtaining unit 201 is output to the watermark information embedding device 100 and passed through various distribution channels.

The vector data storage section 202 is an area of a memory for storing vector data. The extraction target color A specifying unit 203 embeds the bit string of the watermark information by referring to the vector data stored in the vector data storage unit 202, that is, the vector data element group. It has a function of specifying A.

The extraction target color B specifying unit 204 includes a color B approximating the color A specified by the extraction target color A specifying unit 203,
That is, it has a function of specifying the color B indicated by the value to be embedded with the watermark information together with the value indicating the color A. The extraction unit 205 is a vector data element for Line among the vector data elements stored in the vector data storage unit 202, and the value of the line color attribute included in the vector data element is either color A or color B. By extracting a bit value embedded based on the value of the line color attribute and storing the bit value in a working memory area, a bit string corresponding to watermark information is extracted. It has a function of notifying the watermark information output unit 206.

The watermark information output unit 206 outputs the bit sequence transmitted from the extraction unit 205 to the watermark information extraction device 2.
00 has the function of outputting to the outside. The output destination is a recording medium such as a hard disk, a display, or an external network. Note that the vector data acquisition unit 20
1. Extraction target color A specifying unit 203, extraction target color B specifying unit 2
The functions of the extraction unit 205, the extraction unit 205, and the watermark information output unit 206 are realized by the CPU executing the control program stored in the memory. <Operation of Watermark Information Extraction Device> The operation of the watermark information extraction device 200 will be described below.

FIG. 8 is a flowchart showing the operation of the watermark information extracting device 200. Hereinafter, “Elizabet” described in the operation example of the watermark information embedding device 100 described above.
When extracting the watermark information from the vector image in which the 72-bit watermark information representing "h" is embedded, that is, actually extracting the watermark information from the vector data file 400 shown in FIG. The operation shown in FIG. 8 will be described step by step. Here, for simplicity of description, it is assumed that the watermark information is predetermined to be 72 bits.

First, the vector data acquisition unit 201 of the watermark information extraction device 200 acquires a vector data file for drawing a vector image in which the watermark information is embedded from the outside, and stores the contents of the vector data as vector data. (Step S60)
1). When the vector data, that is, the vector data element group is stored in the vector data storage unit 202, the extraction target color A
The specifying unit 203 refers to each vector data element and
Among the colors used as the line color attribute of the vector data element for the ine, the color used for the vector data element for the most Line is searched, and the color, that is, the 8-bit value is specified as the color A. (Step S60
2). Here, it is assumed that the color represented by 0x3F, which is a bright light blue, has been used the most, and the color represented by 0x3F has been determined to be color A.

After the color A is specified, the extraction target color B specifying unit 204 specifies a color similar to the color A as the color B (step S603). That is, the extraction target color B specifying unit 204
Specifies the 8-bit value indicating color B by inverting the third bit from the bottom based on the 8-bit value of color A as shown in FIG. As a result, 0x3B obtained by inverting the third bit from the bottom of 0x3F becomes an 8-bit value indicating color B.

After the color A and the color B are specified, the extraction unit 20
5 performs a process of extracting a bit string as watermark information from the vector data stored in the vector data storage unit 202 (steps S604 to S610). That is, the extraction unit 205 first searches for vector data elements for Line in order starting from the vector data element corresponding to the head of the vector data file (step S60).
4).

After searching for one of the vector data elements for Line, the extraction unit 205
The value of the line color attribute of the vector data element for e is color A
It is determined whether or not the value is an 8-bit value (step S6).
05) If the value indicates the color A, 0 is stored in the working memory area as a bit value constituting the watermark information (step S606).

If it is determined in step S605 that the value of the line color attribute is not the 8-bit value indicating the color A, the extraction unit 205 determines whether the value of the line color attribute is an 8-bit value indicating the color B. It is determined whether or not it is a color B (step S607). If the value indicates the color B, 1 is stored in the working memory area as a bit value constituting the watermark information (step S608). By this step S606 or S608, the row 301, the row 303, the row 305, and the row 30 of the vector data elements which are the contents of the vector data file 400 shown in FIG.
8, 0, 1, 0, 0, 0, 1, 0, 1 are sequentially stored as bit values constituting watermark information in the working memory area for row 8, row 310, row 311, row 313, and row 315. Will be.

If it is determined in step S607 that the value of the line color attribute is not an 8-bit value indicating the color B, the extraction unit 205 searches for a vector data element for the next Line (step S609). The process returns to the determination in step S605. After accumulating the bit value of 0 or 1 in the work memory area in step S606 or step S608, the extraction unit 205 determines whether the accumulated bit value has reached a predetermined amount of watermark information (step S61).
0). That is, it is determined whether 72 bits have been accumulated.

If the accumulated bit value does not reach the predetermined amount of the watermark information, the extraction unit 205 determines the next Lin
The vector data element for e is searched (step S609), and the process returns to the determination in step S605. If the accumulated bit value in step S610 has reached the predetermined amount of watermark information, the extraction unit 205 transmits a bit string composed of all the accumulated bits to the watermark information output unit 206, and outputs the watermark information to the watermark information output unit 206. Is the extraction unit 20
5 is used to extract the bit string transmitted from
(Step S611), whereby the operation of the watermark information extracting apparatus 200 is completed. As a result, for example, "Elizab" which is watermark information is displayed on a display or the like.
eth "is output. <Supplement> The watermark information embedding device and the watermark information extracting device according to the present invention have been described based on the embodiments. However, it is needless to say that the present invention is not limited to the embodiments. That is, (1) The content of the watermark information described in the embodiment is not limited to information used for copyright protection of an author or the like, and may be any information. (2) In the present embodiment, the watermark information embedding device 100 determines the value of the line color attribute in the vector data element for a line (Line) generally used as an element constituting a vector image based on a predetermined rule. Although the watermark information is embedded by changing, if the figure has not only the Line but also the attribute relating to the color, a circle (Circle)
A vector data element of a graphic of any graphic type, such as a Bezier curve or a Bezier curve, may be set as the embedding target. Further, as long as the graphic has an attribute related to color, vector data elements of a plurality of graphics or all available graphics may be set as the embedding target.

For example, the watermark information embedding apparatus 100 is modified to embed watermark information by embedding vector data elements of all available graphics having attributes relating to colors as embedding targets. Considering this, the vector data file output by the modified watermark embedding device is as illustrated in FIG. FIG.
FIG. 4 is a diagram illustrating a part of a vector data file 450 output when a vector data file 300 having the contents illustrated in FIG. 3 is input to the modified watermark information embedding device.

According to the modified watermark information embedding device, the rectangular (R
The vector data element for “Electangle” is also targeted for embedding, and as a result, in the output vector data file 450, as shown in FIG.
Also reflect the bits constituting the watermark information. Corresponding to this, the watermark information extracting device can also extract vector data elements of all available graphics having attributes relating to colors.

Further, the watermark information embedding apparatus includes a plurality of vector data elements for a graphic type, such as a continuous line (PolyLine) and a polygon (Polygon), which can be graphically represented by a plurality of line segments. Line segment (Lin
After performing the conversion to replace the vector data element of e), the watermark information as described in the present embodiment may be embedded in the vector data element of Line. (3) In the present embodiment, the color most frequently used as the line color attribute of the vector data element for Line is specified as the color A to be embedded with the watermark information. It is not limited to the most commonly used colors. When the watermark information is embedded by specifying a color having some characteristic as the color A, when the watermark information is extracted from the vector data file, the embedded color A is specified based on the characteristic. It becomes easier.

Further, in this embodiment, the color A, which is most frequently used as the line color attribute, is associated with 0 and its approximate color is associated with 1, but the color A is associated with 1 The approximate color may be associated with 0. (4) In the present embodiment, instead of the color A specified as the embedding target by the watermark information embedding device 100, the color A, the color C, and the color E
, And a plurality of colors such as a color B approximating the color A, a color D approximating the color C, and a color F approximating the color E instead of the color B determined as the embedding target. A plurality of approximate colors are determined as embedding targets, and a vector data element whose line color attribute value is color A or color B in advance is color A if the bit value to be embedded is 0 and color B if the bit value to be embedded is 1 Is updated in advance, and for the vector data element whose line color attribute value is color C or color D in advance, the line color attribute For a vector data element whose line color attribute value is color E or F in advance, the line color attribute is updated so that the bit value to be embedded is 0 if the bit value is 0, and 1 if the bit value to be embedded is 1 color. May be embedded. In response to this, the watermark information extracting device can also specify the colors A to E and the like as the colors to be extracted and extract the watermark information.

Further, all the vector data elements for Line are to be embedded regardless of the value of the line color attribute, and the bit string of the watermark information corresponds to the vector data element for Line in the vector data file in the order of 1 bit. In addition, among the values of the line color attribute, for example, Gre
By setting a bit having a low effect on human vision such as the least significant bit of en to 0 or 1, each bit value of the watermark information may be represented, that is, the watermark information may be embedded. (5) In the present embodiment, the watermark information embedding apparatus 100 associates each bit value of the watermark information with the line color attribute of a specific vector data element from the first bit in the order of the vector data elements in the vector data file. Therefore, the watermark information is embedded. However, the order of the specific vector data elements that associate each bit value may be the reverse order of the order in the vector data file, or may be the order determined by a predetermined rule. Good. (6) In the present embodiment, the line color attribute and the area color attribute in the vector data element serving as the contents of the vector data file are 8-bit RGB values, but the value representing the color is limited to this. Any number of bits, such as 24 bits, may be used. Red, Green, Bl
The color may be represented by any expression method other than the three components of ue, such as the components of center, cyan, and yellow.

In this embodiment, in order to determine a color B that is similar to the color A, an 8-bit value indicating the color B is determined by inverting the least significant bit of Green in an RGB 8-bit value indicating the color A. However, the method of determining the approximate color is not limited to this, and the least significant bit of Red or the least significant bit of Blue may be inverted, or any other method may be used. Note that the stronger the degree of recognition that the color A specified by the embedding target color A specifying unit 103 and the color B determined by the embedding target color B determining unit 104 approximate to human vision, the stronger the digital watermark is. It becomes suitable.

In the present embodiment, the watermark information is embedded by changing one bit of the eight-bit value constituting the line color attribute in the vector data element. Watermark information may be embedded. (7) In the present embodiment, the number of vector data elements for the Line having the line color attribute indicating the color A specified by the embedding target color A specifying unit 103 is 2 bits of the watermark information bit number.
Although the description has been made on the assumption that the watermark information exists twice or more times, in this case, even when there is no regularity in the watermark information, the watermark information extracting device can extract the watermark information from the vector data element group in which the watermark information is embedded. Can reliably specify the color A to be extracted.

However, the watermark information can be embedded as long as the number of the vector data elements having the attribute relating to the color indicating the color A and the color B which is the approximate color is the minimum number of bits of the watermark information. . For example, a method may be used in which the watermark information is provided with some regularity, and the extracting side uses the regularity to adjust the color A and the color B while extracting the watermark information. Further, in the embedding target color A specifying unit 103 and the extraction target color A specifying unit 203, a vector data element having a color-related attribute whose attribute is a certain unspecified color X and a color Y approximate to the color is specified. Among the vector data elements that use the value indicating the color X that satisfies the condition that the number of values is equal to or greater than the number of bits of the watermark information as the attribute regarding the color, the vector data existing at the forefront of the vector data file The color X related to the element may be specified as the color A. (8) In the present embodiment, the watermark information extraction device 200
Is determined using the predetermined number of bits of the watermark information in step S610. However, if the number of bits of the watermark information is not predetermined, step S61 is performed.
The determination of 0 may be replaced with a process of determining whether the search in step S609 has been completed for all the vector data elements in the vector data file, and the process may proceed to step S611 when all the vector data elements have been completely searched. . (9) In the present embodiment, embedding of watermark information is performed by changing the value of the line color attribute, which is one of the attribute information of the graphic in the vector data element, to an approximate color according to the bit value of the watermark information. In addition to the above, the technique of changing one of the attribute information that specifies the form of the graphic in the vector data element is changed.
The watermark information may be embedded. In addition,
The form is a color, shape, pattern, or the like.

For example, as a data structure of vector data, line type attribute data such as a solid line, a dashed line, and a dashed line is generally used for a line segment (Line). The value of the line type attribute data may be changed to a solid line or a dashed line according to the line width attribute data. If line width attribute data such as a thick line, a normal line, a thin line, or a very thin line is used, each bit of the line width attribute data is changed. The value of the line width attribute data may be changed to a fine line or an extra fine line according to whether the value is 0 or 1. It should be noted that the stronger the degree of recognition that the value of some attribute data corresponding to 0 and the value of attribute data corresponding to 1 is closer to human vision, the more suitable as a digital watermark. Therefore, a value suitable for an electronic watermark may be determined in advance as a value of attribute data corresponding to 0 and 1 by theoretical consideration or experiment, and a watermark information embedding device and a watermark information extracting device may be constructed based on this. (10) A computer program for causing a general-purpose computer or the like to execute the processing procedure (the procedure shown in FIGS. 5 and 8 and the like) of the watermark information embedding device or the watermark information extracting device in the present embodiment is recorded on a recording medium. , Or can be distributed and distributed via various communication channels.
Such a recording medium includes an IC card, an optical disk, a flexible disk, a ROM, and the like. The distributed and distributed computer program is used by being installed in a computer or the like, and the computer or the like executes the computer program and executes the watermark information embedding device or the watermark as described in the present embodiment. Implement an information extraction device.

[0059]

As is apparent from the above description, the watermark information embedding apparatus according to the present invention comprises a set of vector data elements each including a graphic type and a form attribute indicating the form of a graphic, and representing a vector data representing an image. A watermark information embedding device that embeds bit data as an electronic watermark into a vector data acquisition unit that acquires vector data, a bit data acquisition unit that acquires bit data, and a number of bits that constitute the acquired vector data. Embedding means for embedding the bit data in the vector data by changing the value of the morphological attribute included in the vector data element in accordance with the bit data.

This makes it possible to embed watermark information in vector data for drawing the vector image as a digital watermark on the vector image. Also,
The morphological attribute is a color attribute indicating a color of a graphic, and the embedding unit sets a value of a color attribute included in some vector data elements constituting the obtained vector data according to the bit data. The bit data may be embedded in the vector data by changing to a value indicating a color similar to the color indicated by the value.

As a result, the value of the color attribute included in the vector data element for each figure in the vector data for drawing the vector image is changed within an approximate range based on a certain standard, that is, the color indicated by the value is changed. The watermark information can be embedded by changing the change within a range that is hardly noticed by a human. Further, there is no possibility that the data amount increases due to the embedding. The color is represented by 8 bits or more.
Under the current situation in which a large number of vector data in a format capable of expressing six or more colors are present and distributed, a slight change in color has little effect on the entire vector image in many cases. If the criterion is set to a high degree of approximation, it becomes possible to embed watermark information in vector data that cannot be easily discriminated by a person.

Further, the bit data is composed of a bit string, the color attribute is represented by a set of bit strings for representing a plurality of color components, and the embedding means determines each bit constituting the bit data. , One bit having the smallest weight in a bit string for representing a predetermined color component in a color attribute included in several vector data elements constituting the vector data is associated with the one bit, thereby forming the bit data. Performing the above change so that the value corresponding to whether the value of each bit to be performed is 0 or 1 is the content of 1 bit representing a color component associated with the bits constituting the bit data. It may be.

This makes it possible to embed watermark information so that a person does not notice by slightly changing the colors of some figures constituting the vector image. Further, the bit data is composed of a bit string, the vector data obtaining means obtains a vector data file containing a sequence of vector data elements constituting the vector data, and the embedding means includes the vector data element. Of each of a plurality of vector data elements in which the graphic type is a line segment and the value of the color attribute is one of a first value and a second value indicating a color similar to the color indicated by the first value , One bit is allocated from the first bit of the bit data in an order according to the column of the vector data element, and the value of the color attribute of the vector data element is changed to the first value and the first value in response to the value of the allocated one bit. The change may be made so as to take one of two values.

Since the watermark information is embedded by changing the line color of a line segment (Line) which is generally used frequently in a vector image, a large amount of watermark information is generally embedded. It becomes possible. In addition, since a line is generally an elongated shape unlike a surface, the line color is affected by the background color of the line and the like, and the color is difficult to be accurately identified by human vision, so that the watermark information is embedded in the line color. That is useful.

The embedding means is included in the most vector data elements among the color attribute values included in all the vector data elements whose graphic type is a line segment in the column of the vector data elements. Change the value of the color attribute to the first
The value may be determined and the change may be made. Accordingly, since the watermark information is represented by the color most frequently used as the line color and a color close to the color, a large amount of watermark information can be embedded.

The watermark information embedding device according to the present invention comprises a set of vector data elements including a graphic type and a color attribute capable of indicating the color of the graphic in 256 colors or more. A watermark information embedding device for embedding bit data as an electronic watermark in vector data representing an image, comprising: vector data obtaining means for obtaining vector data; bit data obtaining means for obtaining bit data; Embedding the bit data in the vector data by changing the value of the color attribute included in some of the constituent vector data elements to a value indicating a color similar to the color indicated by the value according to the bit data And embedding means.

As a result, in the vector data of a 256-color or more multicolor map image, a color is represented by a value of 8 bits or more, and a certain color and its approximate color cannot be easily distinguished by human vision. Therefore, it is possible to suitably embed watermark information in a map image. Further, the watermark information extracting apparatus according to the present invention extracts the bit data from vector data including a set of vector data elements including a figure type and a form attribute indicating a form of the figure and in which bit data is embedded as an electronic watermark. Data extraction means for obtaining vector data in which bit data is embedded, and a bit based on a value of a morphological attribute included in a plurality of vector data elements constituting the obtained vector data. Extracting means for extracting data.

Thus, the watermark information embedding apparatus extracts the watermark information from the vector image in which the watermark information is embedded by changing the form of the graphic constituting the vector image within an approximate range based on a certain standard. Will be available. Further, the morphological attribute is a color attribute indicating a color of a figure, and the extracting unit determines that a plurality of values of the color attribute among a plurality of color attributes included in the vector data element constituting the acquired vector data are included. Bit data is extracted based on a plurality of color attributes that are any of the specific values, and the plurality of specific values are determined so that each of the plurality of specific values indicates an approximate color. It may be.

Thus, the value of the color attribute included in the vector data element for each figure in the vector data for drawing the vector image is changed within a range in which the change in color indicated by the value is hard to be noticed by a human. Thus, the embedded watermark information can be extracted from the vector data. Further, the bit data embedded in the vector data is composed of a plurality of bits, the color attribute is a set of bit strings for representing each of a plurality of color components, and the extracting unit converts the acquired vector data into From a plurality of color attributes included in the constituent vector data element and having any one of the plurality of specific values as values, a minimum weight of a bit string for representing a predetermined color component included in the color attribute The bit data may be extracted by integrating 1-bit values having the following.

As a result, for some figures constituting the vector image, the watermark information embedded in the vector data can be easily and quickly extracted by changing one bit in the bit string indicating the color of the figure. become able to. Further, the bit data is composed of a bit string, the vector data obtaining means obtains a vector data file containing a sequence of vector data elements constituting the vector data, and the extracting means obtains a vector data file of the vector data element. A plurality of vector data elements in which the graphic type in the column is a line segment and the value of the color attribute is one of the first specific value and a second specific value indicating a color similar to the color indicated by the first specific value Each bit constituting the bit data is sequentially extracted from each of them in the order according to the column of the vector data element, and the extraction is performed by checking whether a color attribute included in the extraction source vector data element is a first specific value. Second
The determination may be performed by specifying whether the bit forming the vector data is 0 or 1 in response to the specific value.

As a result, the watermark information embedded in the line color attribute of the line segment in the vector data file for drawing the vector image can be extracted as an ordered bit string. Further, the extracting means includes:
Of the color attribute values included in all the vector data elements whose graphic type is a line segment in the column of the vector data elements, the value of the color attribute included in the most vector data element is defined as the first specific value. Alternatively, the extraction may be performed.

Thus, when the watermark information is embedded by slightly changing the color most frequently used as the line color attribute of the line segment graphic, the watermark information can be appropriately extracted. Become. In other words, the watermark information can be extracted even if the color in which the watermark information is embedded is not fixed.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a watermark information embedding device 100 according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a map image drawn based on a vector data file input to the watermark information embedding device 100.

3 is a diagram showing an example of the contents of a vector data file input to the watermark information embedding device 100. FIG.

FIG. 4 is a diagram illustrating a relationship between colors A and B, which are watermark information embedding targets, for an 8-bit value indicating a line color attribute.

FIG. 5 is a flowchart showing an operation of the watermark information embedding device 100.

6 is a diagram showing a part of a vector data file 400 output when a vector data file 300 having the contents illustrated in FIG. 3 is input to the watermark information embedding device 100. FIG.

FIG. 7 is a functional block diagram of a watermark information extracting device 200 according to the embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the watermark information extraction device 200.

9 is a diagram showing the contents of a part of the vector data file 450 output when the vector data file 300 having the contents illustrated in FIG. 3 is input to the modified watermark information embedding device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 watermark information embedding device 101 vector data acquisition unit 102 vector data storage unit 103 embedding target color A specifying unit 104 embedding target color B determination unit 105 watermark information acquisition unit 106 embedding unit 107 vector data output unit 200 watermark information extraction Apparatus 201 Vector data acquisition unit 202 Vector data storage unit 203 Extraction target color A specifying unit 204 Extraction target color B specifying unit 205 Extraction unit 206 Watermark information output unit

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (13)

[Claims] 1. A watermark information embedding device for embedding bit data as an electronic watermark in vector data representing an image, comprising a set of vector data elements including a graphic type and a form attribute indicating the form of the figure, comprising: Vector data obtaining means for obtaining, bit data obtaining means for obtaining bit data, and changing a value of a shape attribute included in some vector data elements constituting the obtained vector data according to the bit data Embedding means for embedding the bit data in the vector data. 2. The morphological attribute is a color attribute indicating a color of a graphic, and the embedding means sets the value of the color attribute included in some vector data elements constituting the obtained vector data to the 2. The watermark information embedding device according to claim 1, wherein the bit data is embedded in the vector data by changing the bit data to a value indicating a color similar to the color indicated by the value according to the bit data. 3. The bit data is composed of a bit string, the color attribute is represented by a set of bit strings for representing a plurality of color components, and the embedding unit is configured to replace each bit constituting the bit data with , One-to-one correspondence with one bit having the smallest weight in a bit string for representing a predetermined color component in a color attribute included in some vector data elements constituting the vector data, Performing the above change so that the value corresponding to whether the value of each bit to be performed is 0 or 1 is the content of 1 bit representing a color component associated with the bits constituting the bit data. 3. The watermark information embedding device according to claim 2, wherein: 4. The bit data comprises a bit string, the vector data obtaining means obtains a vector data file containing a sequence of vector data elements constituting the vector data, and the embedding means includes: In the column of the vector data element, the graphic type is a line segment and the value of the color attribute is a first value and a first value.
For each of a plurality of vector data elements each of which is a second value indicating a color similar to the color indicated by the value, one bit is allocated from the first bit of the bit data in the order according to the column of the vector data element 3. The watermark according to claim 2, wherein the change is performed so that the value of the color attribute of the vector data element is set to one of the first value and the second value in response to the assigned 1-bit value. Information embedding device. 5. The embedding means is included in the most vector data elements among the color attribute values included in all the vector data elements having the graphic type of the line segment in the column of the vector data elements. The watermark information embedding device according to claim 4, wherein the change is performed by defining a value of a color attribute as the first value. 6. A vector data representing a map image by a group of figures of a plurality of colors, comprising a set of vector data elements including a figure type and a color attribute capable of indicating the color of the figure in 256 colors or more, as bit data as an electronic watermark. A watermark information embedding device that embeds vector data, includes vector data obtaining means for obtaining vector data, bit data obtaining means for obtaining bit data, and some vector data elements constituting the obtained vector data. An embedding unit that embeds the bit data in the vector data by changing a value of a color attribute to a value indicating a color similar to the color indicated by the value according to the bit data. Watermark information embedding device. 7. A watermark information extracting apparatus for extracting bit data from vector data including a set of vector data elements including a graphic type and a form attribute indicating a form of the figure and having bit data embedded as an electronic watermark. Vector data obtaining means for obtaining vector data in which bit data is embedded; extracting means for extracting bit data based on a value of a morphological attribute included in a plurality of vector data elements constituting the obtained vector data; A watermark information extraction device comprising: 8. The morphological attribute is a color attribute indicating a color of a graphic, and the extracting unit determines a value of the color attribute among color attributes included in vector data elements constituting the obtained vector data. Extracts bit data based on a plurality of color attributes that are any of a plurality of specific values, and the plurality of specific values are determined such that all the colors indicated by the plurality of specific values are similar colors. The watermark information extracting device according to claim 7, wherein 9. The bit data embedded in the vector data is composed of a plurality of bits, the color attribute is a set of bit strings representing each of a plurality of color components, and the extracting unit From a plurality of color attributes included in the vector data elements constituting the vector data and having a value of any of the plurality of specific values,
9. The watermark information extraction according to claim 8, wherein the bit data is extracted by accumulating 1-bit values having the minimum weight in a bit string representing a predetermined color component included in the color attribute. apparatus. 10. The bit data comprises a bit sequence, the vector data obtaining means obtains a vector data file containing a sequence of vector data elements constituting the vector data, and the extracting means sets the vector data A plurality of data element columns in which the graphic type is a line segment and the value of the color attribute is one of a first specific value and a second specific value indicating a color similar to the color indicated by the first specific value Extracting, from each of the vector data elements, each bit constituting the bit data in an order according to the column of the vector data elements, wherein the color attribute included in the extraction source vector data element is a first specific value; The method is performed by specifying whether a bit constituting the vector data is 0 or 1 in response to whether the bit is a second specific value. 8. The watermark information extracting device according to item 8. 11. The method according to claim 1, wherein the extracting unit is configured to determine a color included in the most vector data element among color attribute values included in all the vector data elements whose graphic type is a line segment in the column of the vector data element. 11. The watermark information embedding device according to claim 10, wherein the extraction is performed by defining a value of an attribute as the first specific value. 12. A program for causing a computer to execute a watermark information embedding process for embedding bit data as an electronic watermark in vector data representing an image, which is composed of a set of vector data elements including a graphic type and a form attribute indicating a form of the figure. A recording medium on which a control program is recorded, wherein the watermark information embedding process includes a step of acquiring vector data, a step of acquiring bit data, and a step of acquiring bit data. An embedding step of embedding the bit data in the vector data by changing a value of a form attribute included in the vector data element to a value indicating a form similar to the form indicated by the value according to the bit data And a recording medium comprising: 13. A watermark information extracting process for extracting bit data from vector data including a set of vector data elements including a graphic type and a form attribute indicating a form of the figure and having bit data embedded as an electronic watermark. Wherein the watermark information extracting process includes a step of obtaining vector data in which bit data is embedded, and a plurality of specific values serving as values of a form attribute. A specific value determining step of determining that the form indicated by the plurality of specific values is all an approximate form; and of the form attributes included in the vector data elements constituting the obtained vector data, The value is based on a plurality of morphological attributes that are any of the determined specific values. Recording medium, characterized in that it comprises an extraction step of extracting a bit data.