WO2020116176A1

WO2020116176A1 - Embedding device, extracting device and program

Info

Publication number: WO2020116176A1
Application number: PCT/JP2019/045551
Authority: WO
Inventors: 勇五十嵐; 伊藤　直己; 片山　淳; 慎吾安藤; 淳嵯峨田
Original assignee: 日本電信電話株式会社
Priority date: 2018-12-05
Filing date: 2019-11-21
Publication date: 2020-06-11
Also published as: JP2020090032A

Abstract

An embedding device for embedding watermark information into a target image comprises a superimposing unit that superimposes, on each of a plurality of areas into which the target image is divided, one of at least two types of features expressed by use of respective pixel values, the embedding device being characterized in that the superimposing unit embeds the watermark information into the target image such that, for each of a plurality of sets each consisting of a prescribed number of ones of the areas, the watermark information is expressed by a pattern determined by the position of each area, in which the feature is embedded, in each set.

Description

Embedded device, extraction device and program

The present invention relates to an embedding device, an extracting device and a program.

A technology called digital watermarking is known as a technology for embedding other information in content such as images and videos in a form that cannot be perceived by the human eye. The electronic watermark is often used for the purpose of identifying and managing the content, protecting and managing the copyright, providing information related to the content, and the like in the distribution of the content.

In digital watermark technology for image content, methods based on minute changes in pixel values are known. For example, a method is known in which geometric distortion correction using a frame line and a digital watermark algorithm based on a two-dimensional block pattern modulation method are combined (Non-Patent Document 1).

According to the method disclosed in Non-Patent Document 1, even when an image in which a digital watermark is embedded in advance is printed on paper, a digital watermark is detected at high speed and stably using a camera such as a mobile phone or a smartphone. be able to. Further, when the image is printed, the digital watermark can be detected even if the image is taken from an oblique direction.

However, depending on the target of embedding the digital watermark, the area where the digital watermark can be embedded may be limited. For example, when embedding a digital watermark in an image including a product logo, a company logo, etc. (specifically, an image of a product package, etc.), there is a need not to embed the digital watermark in the logo portion. For this reason, it is necessary to embed the digital watermark pattern other than the logo portion, and the area in which the digital watermark can be embedded is limited.

Also, when printing an image in which a digital watermark is embedded with a printing machine, there is a lower limit to the size of the block area used when embedding a digital watermark depending on the resolution of the printing machine. Therefore, the amount of information that can be extracted from the unit area of the printed matter of the image in which the digital watermark is embedded is limited.

Therefore, it is necessary to increase the amount of digital watermark information that can be embedded in the area when comparing the same area in the image where the digital watermark is embedded.

The present invention has been made in view of the above points, and an object thereof is to improve the amount of watermark information that can be embedded in a target image.

In order to achieve the above object, an embedding device according to an embodiment of the present invention is an embedding device for embedding watermark information in a target image, and includes a pixel value for each divided area of the target image. A superimposing unit that superimposes one of the at least two types of expressed features on the region, the superimposing unit is configured such that the watermark information includes the feature for each set of the regions in a predetermined unit. The watermark information is embedded in the target image so as to be expressed by a pattern determined by the position of each embedded region in the set.

The extraction device according to the embodiment of the present invention is an extraction device for extracting watermark information embedded in a target image, and is expressed by a pixel value for each divided area of the target image. There is a detection unit that detects one type of features from at least two types of features from the region, and the detection unit includes, for each set of the regions of a predetermined unit, the features of each region in which the features are embedded. The watermark information is extracted from the target image by detecting the watermark information according to a pattern determined by a position in the set.

The amount of watermark information that can be embedded in the target image can be improved.

It is a figure which shows an example of a structure of the watermark information embedding apparatus and watermark information extraction apparatus in embodiment of this invention. It is a figure which shows an example of the hardware constitutions of a computer. It is a figure showing an example of functional composition of an embedding processing part in an embodiment of the invention. It is a figure which shows an example of a functional structure of the extraction process part in embodiment of this invention. 6 is a flowchart showing an example of watermark information embedding processing according to the embodiment of the present invention. FIG. 7 is a diagram showing an example of an embedding target image divided into a plurality of block areas. It is a figure (1) which shows an example of grouping of block areas. It is a figure (2) which shows an example of grouping of block areas. It is a figure which shows an example of division|segmentation into a block area|region and grouping when a logo is contained in an image for embedding. It is a figure which shows an example of the correspondence of the block pattern in a group and the value which each digit can take in K=hexadecimal in the case of N=4 and M=2. It is a figure which shows an example of overwriting of a black dot and a white dot in case N=4 and M=2. It is a figure which shows an example of the corresponding relationship between the block pattern in a group in the case of N=9, and M=2, and the value which each digit can take in K=36 base. It is a figure which shows an example of the overwriting of the black dot and the white dot in case N=9 and M=2. It is a figure which shows an example of the corresponding relationship between the block pattern in a group in case of N=4, M=0-4, and the value which each digit can take in a hexadecimal number. It is a flow chart which shows an example of watermark information extraction processing in an embodiment of the invention.

Embodiments of the present invention will be described below with reference to the drawings. In the embodiment of the present invention, a watermark information embedding device 10 capable of improving the amount of information that can be embedded in a target image (hereinafter also referred to as “embedding target image”) in which digital watermark information is to be embedded, A watermark information extraction device 20 capable of extracting information from an image in which electronic watermark information is embedded (hereinafter, also referred to as “embedded image”) or a printed matter thereof will be described.

Note that digital watermarks are sometimes called tint block watermarks. In particular, a technique for extracting the information from a printed matter on which an image in which information is embedded is printed in a manner that cannot be perceived by human eyes is sometimes referred to as a tint block watermark. In the embodiment of the present invention, a digital watermark and a tint block watermark are not distinguished, and are collectively referred to simply as “watermark”. Therefore, information that is embedded in the target image as electronic data (digital watermark information) and information that is embedded in the printed matter with ink or the like are not distinguished and are collectively referred to as “watermark information”.

In the embodiment of the present invention, the embedding target image is described as a still image, but the target image in which the watermark information is embedded may be a moving image. In this case, each of the frame images included in the moving image may be the embedding target image.

<Structures of Watermark Information Embedding Device 10 and Watermark Information Extracting Device 20>
First, the configurations of the watermark information embedding device 10 and the watermark information extracting device 20 according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an example of the configurations of a watermark information embedding device 10 and a watermark information extracting device 20 according to an embodiment of the present invention.

The watermark information embedding device 10 shown in FIG. 1A is, for example, a computer such as a PC (personal computer), a smartphone, or a tablet terminal. The watermark information embedding device 10 may be an image forming device having a scanner or a plotter, a digital camera, or the like. The watermark information embedding device 10 may be any device that can input and output images.

The watermark information embedding device 10 has an embedding processing unit 100. In the watermark information embedding device 10, the embedding processing unit 100 performs watermark information embedding processing. That is, the embedding processing unit 100 embeds watermark information in the input embedding target image G100 to create an embedded image G200, and outputs the created embedded image G200. The watermark information is arbitrary information (data) embedded in the embedding target image G100.

The watermark information extraction device 20 shown in FIG. 1B is a computer such as a PC, a smartphone, or a tablet terminal. The watermark information extraction device 20 may be an image forming device having at least a scanner, a digital camera, or the like. The watermark information extraction device 20 may be any device that can input at least an image.

The watermark information extraction device 20 has an extraction processing unit 200. In the watermark information extraction device 20, the extraction processing unit 200 performs watermark information extraction processing. That is, the extraction processing unit 200 extracts watermark information from the input embedded image G300 and outputs the extracted watermark information. The embedded image G300 may be the embedded image G200, or may be an image created by scanning or photographing a printed matter on which the embedded image G200 is printed. Hereinafter, the embedded image G300 is also referred to as a “query image G300”.

The configurations of the watermark information embedding device 10 and the watermark information extracting device 20 shown in FIG. 1 are examples, and other configurations may be used. For example, the embedding processing unit 100 and the extraction processing unit 200 may be included in one device.

<Hardware configuration>
Next, the hardware configuration of the computer 300 that realizes the watermark information embedding device 10 and the watermark information extracting device 20 will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the hardware configuration of the computer 300.

The computer 300 illustrated in FIG. 2 includes an input device 301, a display device 302, an external I/F 303, a RAM (Random Access Memory) 304, a ROM (Read Only Memory) 305, and a CPU (Central Processing Unit) 306. , A communication I/F 307 and an auxiliary storage device 308. These pieces of hardware are connected to each other via a bus B so that they can communicate with each other.

The input device 301 is, for example, a keyboard, a mouse, a touch panel, etc., and is used by the user to input various operations. The display device 302 is, for example, a display or the like, and displays the processing result of the computer 300 and the like.

The external I/F 303 is an interface with an external device. The external device includes a recording medium 303a and the like. The computer 300 can read and write the recording medium 303a via the external I/F 303. The recording medium 303a may store, for example, one or more programs that implement the embedding processing unit 100, one or more programs that implement the extraction processing unit 200, and the like.

The recording medium 303a includes, for example, a flexible disk, a CD (Compact Disc), a DVD (Digital Versatile Disk), an SD memory card (Secure Digital memory card), and a USV (Universal Serial Bus) memory card.

RAM 304 is a volatile semiconductor memory that temporarily holds programs and data. The ROM 305 is a non-volatile semiconductor memory that can retain programs and data even when the power is turned off. The ROM 305 stores, for example, OS (Operating System) setting information, communication network setting information, and the like.

The CPU 306 is an arithmetic unit that reads programs and data from the ROM 305 and the auxiliary storage device 308 onto the RAM 304 and executes processing. The CPU may be referred to as an MPU (Micro Processing Unit) or the like, for example.

The communication I/F 307 is an interface for connecting the computer 300 to a communication network.

The auxiliary storage device 308 is, for example, a HDD (Hard Disk Drive) or an SSD (Solid State Drive), and is a non-volatile storage device that stores programs and data. The programs and data stored in the auxiliary storage device 308 include, for example, an OS, an application program that implements various functions on the OS, one or more programs that implement the embedding processing unit 100, and an extraction processing unit 200. There are one or more programs.

Note that the watermark information embedding device 10 may include, as hardware, a printing device such as a plotter, an imaging device such as a camera, or the like. Further, the watermark information extraction device 20 may include, as hardware, an imaging device such as a camera and a reading device such as a scanner.

<Functional configuration of the embedding processing unit 100>
Next, the functional configuration of the embedding processing unit 100 according to the embodiment of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing an example of a functional configuration of the embedding processing unit 100 according to the embodiment of the present invention.

The embedding processing unit 100 shown in FIG. 3 is realized by a process of causing the CPU 306 of the watermark information embedding device 10 to execute one or more programs installed in the watermark information embedding device 10.

The embedding processing unit 100 includes an input unit 101, a registration unit 102, a superposition unit 103, and an output unit 104.

The input unit 101 inputs the embedding target image G100. That is, the input unit 101 inputs the embedding target image G100 as digital data (electronic data). The input embedding target image G100 is transmitted to the registration unit 102 and the superimposing unit 103.

The registration unit 102 calculates the position specifying information of the embedding target image G100 input by the input unit 101, and registers (stores) the calculated position specifying information in a predetermined storage area. Here, the position identification information is information for identifying the embedded image G200 from the query image G300 in the watermark information extraction process. The position identification information is calculated using, for example, the image recognition method disclosed in JP-A-2015-201123. That is, for example, the registration unit 102 specifies the coordinates indicating the positions of the feature points extracted from the embedding target image G100, the local feature amount at the positions of these feature points, and the coordinates of the four vertices of the embedding target image G100. Calculate as information. The predetermined storage area may be, for example, a storage area on the storage device that is accessible by both the watermark information embedding device 10 and the watermark information extracting device 20.

The superimposing unit 103 embeds watermark information in the embedding target image G100 input by the input unit 101 to create an embedded image G200.

That is, the superimposing unit 103 divides the embedding target image G100 input by the input unit 101 into a plurality of block areas, and then groups each of the N block areas. Then, the superimposing unit 103 determines that the block information represented by M (1≦M≦N−1) block areas and NM block areas for each group has the watermark information K( However, K= _N C _M , that is, a combination of M block areas that can be selected from N block areas) A combination of M block areas corresponding to one digit when expressed in a base number Watermark information is embedded by superimposing black dots and white dots on the NM block areas. As a result, the embedded image G200 is created. The created embedded image G200 is transmitted to the output unit 104. Note that N is a preset integer of 2 or more, and M is a preset integer of 1 or more and N-1 or less.

The output unit 104 outputs the embedded image G200 created by the superimposing unit 103 to a predetermined output destination. Here, the output unit 104 may output the embedded image G200 to any preset output destination. For example, the output unit 104 may output the embedded image G200 to the auxiliary storage device 308, output the embedded image G200 to the display device 302, or output the embedded image G200 to a printing device such as a plotter. May be output. Further, for example, the output unit 104 may output the embedded image G200 to another device (for example, another computer, an image forming device, a printer, a display device, etc.) connected via the communication I/F 307. .

<Functional configuration of the extraction processing unit 200>
Next, the functional configuration of the extraction processing unit 200 according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing an example of a functional configuration of the extraction processing unit 200 according to the embodiment of the present invention.

The extraction processing unit 200 shown in FIG. 4 is realized by a process of causing the CPU 306 of the watermark information extracting device 20 to execute one or more programs installed in the watermark information extracting device 20.

The extraction processing unit 200 includes an input unit 201, a specification unit 202, a correction unit 203, an extraction unit 204, and an output unit 205.

The input unit 201 inputs the query image G300. The query image G300 is, for example, digital data (electronic data) input by photographing a printed matter on which the embedded image G200 is printed or a display or the like displaying the embedded image G200 with a camera. The input query image G300 is transmitted to the identifying unit 202. The query image G300 may be, for example, one input by scanning a printed matter on which the embedded image G200 is printed with a scanner, or may be the embedded image G200 itself.

The specifying unit 202 uses the position specifying information registered in a predetermined storage area to search for four of the embedded image G200 (that is, the image area corresponding to the embedded image G200) from the query image G300 input by the input unit 201. Specify the coordinates of the vertices. This identification can be performed by using, for example, the image recognition method disclosed in JP-A-2015-201123. That is, for example, the identifying unit 202 extracts feature points from the query image G300, and associates the extracted feature points with the feature points included in the position identification information by matching the local feature amounts. Then, the specifying unit 202 calculates the parameters of the projective transformation matrix by the least-squares method or the like from the degree of positional shift between these feature points, and then the four vertices included in the position specifying information (that is, 4 of the embedding target image G100). Which coordinate of the query image G300 the coordinate of the (vertex) is associated with is calculated by the projective transformation matrix using the parameter. The obtained coordinates of the query image G300 (coordinates corresponding to each of the above four vertices) are coordinates of four vertices of the image area in which the watermark information is embedded (that is, the image area corresponding to the embedded image G200). Is.

With this, in the query image G300, the coordinates of the four vertices of the image area corresponding to the embedded image G200 are specified. The identified result (coordinates of four vertices) is transmitted to the correction unit 203.

The correction unit 203 corrects the query image G300 using the coordinates of the four vertices identified by the identification unit 202. That is, the correction unit 203 normalizes the query image G300. Further, the correction unit 203 deletes (clipping) a portion other than the rectangular image area indicated by the coordinates of the four vertices. Note that the normalization is, for example, conversion of a query image G300 input by shooting a printed matter or the like on which the embedded image G200 is printed with a camera into an image input when the printed matter or the like is photographed from the front. It is to be. The corrected query image G300 is transmitted to the extraction unit 204. Hereinafter, the corrected query image G300 is also simply referred to as “query image G300”.

The extraction unit 204 extracts watermark information from the query image G300 corrected by the correction unit 203. That is, the extraction unit 204 detects, for example, a block pattern represented by M block areas and NM block areas for each group including N block areas, thereby extracting the block pattern. Extract the K-adic watermark information in which is one digit. The extracted watermark information (or the watermark information obtained by converting the K-adic watermark information into a bit string) is transmitted to the output unit 205.

The output unit 205 outputs the watermark information extracted by the extraction unit 204 to a predetermined output destination. Here, the output unit 205 may output the watermark information to any preset output destination. For example, the output unit 205 may output the watermark information to the auxiliary storage device 308, or may output the watermark information to the display device 302. Further, for example, the output unit 205 may output the watermark information to another device connected via the communication I/F 307. Alternatively, for example, the output unit 205 outputs the URL corresponding to the watermark information extracted by the extraction unit 204 to a Web browser or the like by referring to a table in which the watermark information and the URL (Uniform Resource Locator) are associated with each other. Alternatively, a mail address corresponding to the watermark information extracted by the extraction unit 204 may be output to a mailer or the like by referring to a table in which the watermark information and the mail address are associated with each other.

<Watermark information embedding process>
Hereinafter, a process of creating the embedded image G200 in which watermark information is embedded in the embedding target image G100 and outputting the created embedded image G200 will be described with reference to FIG. FIG. 5 is a flowchart showing an example of the watermark information embedding process according to the embodiment of the present invention.

First, the input unit 101 inputs the embedding target image G100 (step S11). The input unit 101 may input, for example, the embedding target image G100 stored in the auxiliary storage device 308, or may input the embedding target image G100 by shooting an arbitrary target with a camera or the like.

Next, the registration unit 102 calculates the position identification information of the embedding target image G100 input by the input unit 101, and registers the calculated position identification information in a predetermined storage area (step S12). The method of calculating the position specifying information is as described above.

Note that the registration unit 102 may add a predetermined marker to the embedding target image G100, for example, instead of calculating and registering the position specifying information in step S12 described above. Specifically, for example, an explicit frame line may be provided as a marker around the embedding target image G100, or a QR code (registered trademark) or the like may be provided as a marker at four corners of the embedding target image G100. Good.

Next, the superimposing unit 103 divides the embedding target image G100 input by the input unit 101 into a plurality of block areas (step S13). When the marker is added in step S12 described above, the superimposing unit 103 may divide the embedding target image G100 to which the marker is added into a plurality of block areas. The block area may be a rectangular area and may be a square or a rectangle.

Here, FIG. 6 shows an embedding target image G100 divided into a plurality of block areas. In the example shown in FIG. 6, the embedding target image G100 is divided into 64 block regions of 8×8. Note that division into 8×8 64 block regions is an example, and the superimposing unit 103 divides the embedding target image G100 into a predetermined arbitrary number of block regions.

Next, the superimposing unit 103 groups the plurality of block areas obtained by the division in the above step S13 into N block areas (step S14).

Here, as an example, FIG. 7 shows a case where N=4 block areas are grouped. The example shown in FIG. 7 is an example in which four block areas are grouped into one group when the embedding target image G100 is divided into 64 block areas of 8×8 in step S13. is there.

Further, as an example, FIG. 8 shows a case where N=9 block areas are grouped. In the example shown in FIG. 8, when the embedding target image G100 is divided into 144 block areas of 12×12 in step S13, nine block areas are grouped into one group. is there.

Note that the examples shown in FIGS. 7 and 8 show the case where the image area represented by each group is a single connected area, but the image area represented by each group does not necessarily have to be a single connected area. Therefore, the superposition unit 103 may group any N block areas into one group.

Here, when the embedding target image G100 is used for a product package or the like, a company logo, a product logo, or the like (hereinafter simply referred to as “logo”) may be included in the embedding target image G100. In such a case, there is a need not to embed the watermark information in the logo portion. Therefore, if there is a margin around the logo, the margin is divided into a plurality of block areas in step S13, and then the plurality of block areas are grouped in step S14. Generally, a margin is often provided around the logo so that the logo stands out.

FIG. 9 shows an example of a case where a logo is included in the embedding target image G100, a margin portion around the logo is divided into a plurality of block areas, and the plurality of block areas are grouped into N=4 pieces. Show. In the example shown in FIG. 9, N=4 block areas are grouped into one group in the margin portion around the logo. Since there are few textures in the margins around the logo and there are few elements that cause noise, by dividing and grouping such margins into multiple block areas, in the watermark information extraction process, It becomes possible to easily detect the black dot and the white dot that are superimposed on the block area in the group.

Next, the superimposing unit 103 determines that the block pattern represented by M (where 1≦M≦N−1) block areas and NM block areas is watermark information K for each group. (However, K= _N C _M ) In order to correspond to one digit when expressed in a base number, black dots and white dots are respectively set for the M block regions and the NM block regions. Are superimposed to create an embedded image G200 (step S15). As a result, an embedded image G200 in which watermark information is embedded in the embedding target image G100 is created.

Hereafter, a set composed of M block areas will be referred to as a “first group”, and a set composed of NM block areas will be referred to as a “second group”.

At this time, as an example, a case where N=4 and M=2 and the number of groups grouped in step S14 is 16 will be specifically described. In this case, first, superimposing unit _103, K = _{4 C} 2 = the watermark information represented in hexadecimal numbers as _{_{_x}} 0 _x 1 ··· _x _15, group i (i = 0, ··, 15) Block Pattern X _i is expressed by superimposing black dots on the block areas of the first group and white dots on the block areas of the second group included in the group i.

For example, since x _i can take any value from 0 to 5, the block pattern of each group i and the possible values of x _i can be associated as shown in FIG. Therefore, the superimposing unit 103 expresses the value of x _i as a block pattern corresponding to the value.

Then, the superimposing unit 103 superimposes black dots on the block area of the first group represented by the block pattern and superimposes white dots on the block area of the second group represented by the block pattern. For example, when x _i =0, the superimposing unit 103 forms black dots in the block area of the first group represented by the block pattern of the group i (the block pattern corresponding to x _i =0) as shown in FIG. While superimposing, white dots are superposed on the block area of the second group represented by the block pattern. At this time, the superimposing unit 103 spatially randomly disperses dots in one block area (black dots in the case of the block area of the first group, white dots in the case of the block area of the second group). Is overwritten with a predetermined density.

Similarly, as an example, a case where N=9 and M=2 and the number of groups grouped in step S14 is 16 will be specifically described. In this case, first, superimposing unit _103, K _{= 9} C 2 ₌ the watermark information represented by 36 binary as _{_{_x}} 0 _x 1 ··· _x _15, group i (i = 0, ··, 15) Block Pattern X _i is expressed by superimposing black dots on the block areas of the first group and white dots on the block areas of the second group included in the group i.

For example, since x _i can take any value of 0 to 9 and A to Z, the block pattern of each group i and the possible value of x _i can be associated as shown in FIG. Therefore, the superimposing unit 103 expresses the value of x _i as a block pattern corresponding to the value.

As described above, by representing one digit of the watermark information expressed by K= _N C _M base number with one group, the watermark information can be embedded in the embedding target image G100. At this time, if the number of groups included in the embedding target image G100 is I, it is possible to embed K ^I watermark information in the embedding target image G100.

Note that at least one black dot may be superimposed on the first group block area, and at least one white dot may be superimposed on the second group block area. However, the present invention is not limited to this. For example, only one of superimposing a black dot on the block area of the first group or superimposing a white dot on the second block area may be performed.

Also, when dots (black dots in the case of the first group of block areas and white dots in the case of the second group of block areas) are to be superimposed on the block area, one dot may be added to one block area depending on the dot density setting. Sometimes only a few dots are overwritten. In this case, in order to improve the robustness (robustness) of the block area with respect to positional displacement, it is preferable that at least one dot is overwritten in the vicinity of the center of the block area for each block area.

The size of the dots (dot diameter) to be superimposed on each block area can be set arbitrarily. For example, in consideration of the case of printing the embedded image G200, the dot diameter corresponding to the dpi of the printing machine. It is preferable that

Here, in the above, M is one of 1≦M≦N−1. However, for example, if M can take any value of 0 or more and N or less for each group, It becomes possible to embed watermark information having a larger amount of information in the embedding target image G100. For example, in the case of N=4, if M can take an arbitrary value of 0 or more and N=4 or less for each group, as shown in FIG. Each digit in the case where the information is expressed in hexadecimal can be expressed. However, in this case, since the group pattern for one group increases, there is a high possibility that erroneous watermark information will be extracted due to noise in the watermark information extraction process. Therefore, the texture of the image area in which dots can be superimposed, the performance of the printing machine when printing the embedded image G200, the performance of the camera that captures the printed material in the watermark information extraction processing, and the performance of the scanner that scans the printed material in the watermark information extraction processing. In consideration of performance and the like, it is preferable to limit the number of group patterns to a number that enables stable extraction of watermark information.

In the above, the watermark information is embedded in the embedding target image G100 as it is, but it is preferable to embed the watermark information in the embedding target image G100 after performing various kinds of redundancy such as spectrum spreading and error correction coding. Thereby, for example, in the watermark information extraction process, robustness against various deterioration factors such as partial occlusion can be enhanced.

Also, it is not always necessary to match each digit when the watermark information is expressed in a K-adic number with the arrangement of each group of the embedding target image G100, and for example, the watermark information may be scrambled.

Note that black dots and white dots may be referred to as black dots and white dots, respectively. Further, it is not always necessary to use black dots or white dots, and any one kind or two or more kinds of feature points for distinguishing the block area included in the first group from the block area included in the second group are used. May be

Next, the output unit 104 outputs the embedded image G200 created by the superposition unit 103 to a predetermined output destination (step S16). Here, when outputting the embedded image G200 to the printing machine, it is preferable to output to the printing machine that can use white ink in addition to the CMYK ink. As a result, the white dots superimposed on the block area of the second group can be printed with white ink. When outputting the embedded image G200 to the printing machine, for example, the embedded image G200 is temporarily stored as an image file in the auxiliary storage device 308, the recording medium 303a, or the like, and then the image file is printed. You can print with.

<Watermark information extraction process>
Hereinafter, a process of extracting watermark information from the query image G300 in which the watermark information is embedded will be described with reference to FIG. FIG. 15 is a flowchart showing an example of watermark information extraction processing according to the embodiment of the present invention.

First, the input unit 201 inputs the query image G300 (step S21). The input unit 201 may input the query image G300 by, for example, photographing a printed matter or the like on which the embedded image G200 is printed with a camera, or scanning the printed matter on which the embedded image G200 is printed with a scanner. Therefore, the query image G300 may be input, or the embedded image G200 stored in the auxiliary storage device 308 or the like may be input as the query image G300.

Next, the specifying unit 202 uses the position specifying information registered in the predetermined storage area, from the query image G300 input by the input unit 201 to the embedded image G200 (that is, the image area corresponding to the embedded image G200). ) Coordinates of the four vertices are identified (step S22). The method of specifying the coordinates of these four vertices is as described above.

If a marker is attached to the embedded image G200, the identifying unit 202 may identify the coordinates of the four vertices of the embedded image G200 by detecting the marker.

Next, the correction unit 203 corrects the query image G300 using the coordinates of the four vertices identified by the identification unit 202 (step S23). That is, the correction unit 203 normalizes the query image G300 using the coordinates of the four vertices, and then clips a portion other than the rectangular image area indicated by the coordinates of the four vertices.

The reason for clipping is that the area other than the rectangular image area indicated by the coordinates of the four vertices is unnecessary. Therefore, in step S23 described above, clipping does not necessarily have to be performed, and clipping may not be performed.

Next, watermark information is extracted from the query image G300 corrected by the correction unit 203 (step S24). That is, the extraction unit 204 detects the block pattern represented by the block area included in the first group and the block area included in the second group for each group of the query image G300, and thus the block pattern is set to 1 The K-adic watermark information having one digit is extracted.

Here, the extraction unit 204 detects, for example, a block region in which the black dots are superimposed as a block region included in the first group, and a block region in which the white dots are superimposed is a block region included in the second group. Then, the block pattern is detected. Then, the extraction unit 204 extracts the watermark information by setting the value corresponding to the block pattern of each group as the value of the digit corresponding to the group among the digits of the K-adic watermark information. At this time, the extraction unit 204 may convert the K-adic number watermark information into a bit string.

Also, the extraction unit 204 may use top hat processing or black hat processing in order to detect black dots or white dots. The top hat process is a process of creating an image represented by the difference between the query image G300 and the query image G300 subjected to the opening process. By this processing, white dots can be detected. On the other hand, the black hat process is a process of creating an image represented by the difference between the query image G300 and the closing query image G300. By this processing, black dots can be detected.

Furthermore, in the watermark information embedding process, for example, when the watermark information is made redundant or the watermark information is scrambled, the extraction unit 204 decodes the watermark information before the redundancy or before the scramble. Take appropriate action.

In the watermark information embedding process, if only one of the black dot superimposition on the first group block area or the white dot superimposition on the second group block area is performed, the above-described step S24 is performed. Then, it suffices to detect only the dots (either black dots or white dots) that are superimposed in the watermark information embedding process.

Next, the output unit 205 outputs the watermark information extracted by the extraction unit 204 to a predetermined output destination (step S25).

<Summary>
As described above, the watermark information embedding device 10 according to the embodiment of the present invention regards N block areas in the embedding target image G100 as one group, and sets M block areas and NM block areas in the group. The watermark information expressed in K= _N C _M base number by the block pattern with the block area of is embedded in the embedding target image G100. Therefore, according to the watermark information embedding device 10 in the embodiment of the present invention, for example, even when the image area in which the watermark information can be embedded in the embedding target image G100 is limited, it is possible to achieve high density. The watermark information can be embedded, and the amount of watermark information that can be embedded in the embedding target image G100 can be improved.

Note that with the watermark information embedding device 10 according to the embodiment of the present invention, the greater the value of N, the higher the density of watermark information that can be embedded in the embedding target image G100. Further, since 0 to K-1 can be expressed by one group, it becomes possible to embed the watermark information most efficiently when M=N/2.

Further, the watermark information extracting device 20 according to the embodiment of the present invention can extract the watermark information embedded by the watermark information embedding device 10 from the query image G300.

The present invention is not limited to the above specifically disclosed embodiments, and various modifications and changes can be made without departing from the scope of the claims.

10 watermark information embedding device 20 watermark information extracting device 100 embedding processing unit 101 input unit 102 registration unit 103 superimposing unit 104 output unit 200 extraction processing unit 201 input unit 202 specifying unit 203 correcting unit 204 extracting unit 205 output unit

Claims

An embedding device for embedding watermark information in a target image,
For each of the divided regions of the target image, a superimposing unit that superimposes one type of features among the at least two types of features represented by pixel values on the region,
The superimposing section is
Embedding the watermark information in the target image so that the watermark information is expressed by a pattern determined by the position of each region in which the feature is embedded in the set, for each set of the regions in a predetermined unit.
An embedded device characterized by the above.
The superimposing section is
When the target image includes a logo, in each of the divided regions of the image other than the logo in the target image, the one type of feature is superimposed on the region.
The implanting device according to claim 1, wherein:
The superimposing section is
One or more features of the one type are superimposed on the region, and at least one of the one or more features is superimposed near the center of the region;
The implanting device according to claim 1 or 2, characterized in that:
The one characteristic is a white dot,
A printing unit for printing the white dots included in the image in which the watermark information is embedded with white ink for the image in which the watermark information is embedded in the target image. 4. The implantable device according to any one of 3 above.
An extraction device for extracting watermark information embedded in a target image,
A detection unit that detects, from each of the divided regions of the target image, one feature from at least two features represented by a pixel value,
The detection unit,
For each set of the regions of a predetermined unit, the watermark information is extracted from the target image by detecting the watermark information by a pattern determined by the position of each region in which the feature is embedded in the set,
An extraction device characterized by the above.
The two characteristics are black dots and white dots,
The detection unit,
By subjecting the target image to a top hat process or a black hat process, the black dots or the white dots are detected as the features, and for each set, in the set of each region in which the detected features are embedded. The extraction device according to claim 5, wherein the watermark information is detected by a pattern determined by a position.
A program for causing a computer to function as each part of the embedded device according to any one of claims 1 to 4 or each part of the extraction device according to claim 5 or 6.