JP6326082B2 - Digital watermark embedding device, digital watermark detection device, method, and program - Google Patents

Description

  The present invention relates to a digital watermark embedding device, a digital watermark detection device, a method, and a program.

  For the purpose of content identification / management, copyright protection / management, related information provision, etc. when distributing content such as images and videos, digital watermark technology that embeds other information in the content so that it is not perceived by the human eye The method used is known. In particular, in a digital watermark technique for image content, a method based on minute changes in pixel values is common.

  Specifically, for example, a technique that combines geometric distortion correction using a frame line and digital watermark based on a two-dimensional block pattern modulation method is known (for example, Non-Patent Document 1). According to this method, even when an image in which a digital watermark is embedded in advance is printed on paper, the digital watermark can be detected at high speed and stably using a camera of a mobile phone or a smartphone. In particular, when an image is printed, it is a great advantage that it can be detected even if it is taken from an oblique direction.

Takao Nakamura, Atsushi Katayama, Masashi Yamamuro, Noboru Sone “High-speed watermark detection method from analog images using a mobile phone with camera”, IEICE Transactions, D-II Vol.J87-D-II, No.12 , pp.2145-2155, 2004

  However, in order to enable watermark detection by photographing from an oblique direction, it is necessary to explicitly add a frame to the watermark embedded image. This is the principle of detecting a watermark stably by normalizing to an image of a specific scale viewed from the front by the four corner coordinates of the watermark embedding position specified by the detection of the frame.

  However, for example, when applied to a company logo or a product logo attached to a product package, there is a possibility that the logo design is greatly impaired by adding a frame. Therefore, there is a problem that the application range is remarkably limited.

  The present invention has been made to solve the above-described problems, and it is possible to embed a digital watermark that is stably detected in an image without adding a frame for the digital watermark to the image. It is an object to provide a digital watermark embedding apparatus, method, and program that can be used.

  It is another object of the present invention to provide a digital watermark detection apparatus, method, and program capable of stably detecting a digital watermark from an image even if a frame for the digital watermark is not attached to the image.

  In order to achieve the above object, a digital watermark embedding device according to a first aspect of the present invention is a digital watermark embedding device for embedding a digital watermark representing a specific ID in an image, and shows a specific two-dimensional pattern. A reference image input unit for inputting a reference image as digital data, position coordinates of each feature point extracted from the reference image, local feature amounts detected from the positions of the feature points, and four corners of the reference image A registration unit that stores position coordinates in a storage unit, a digital watermark superimposing unit that embeds a digital watermark in a specific area of the reference image obtained by the reference image input unit, and And an embedded image output unit that outputs the embedded reference image.

  A digital watermark embedding method according to a second invention includes a reference image input unit, a registration unit, a digital watermark superimposing unit, and an embedded image output unit, and is an electronic for embedding a digital watermark representing a specific ID in an image An electronic watermark embedding method in a watermark embedding device, wherein the reference image input unit inputs a reference image for indicating a specific two-dimensional pattern as digital data, and the registration unit is extracted from the reference image Storing the position coordinates of each feature point, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image in a storage unit, and the digital watermark superimposing unit includes the reference image A step of embedding a digital watermark in a specific area of the reference image obtained by the input unit; and the embedded image output unit is a digital watermark superimposing unit. Serial comprising a step of outputting the reference image watermark is embedded, a.

  A digital watermark embedding device according to a third invention is a digital watermark embedding device for embedding a digital watermark representing a specific ID in an image, and uses a reference image for indicating a specific two-dimensional pattern as digital data. The reference image input unit to be input, the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image are stored in the storage unit A registration unit, an image input unit that inputs an image to be embedded with a digital watermark as digital data, and a position coordinate of each feature point is extracted from the image input by the image input unit, and from the position of each feature point The local feature amount is detected, and the feature point stored in the storage unit is associated by matching the local feature amount. From the result of the feature point correspondence, An image search unit for identifying which of the reference images the image input by the image input unit corresponds to, and a specific identification of the image input by the image input unit based on the identification result by the image search unit A digital watermark superimposing unit that embeds a digital watermark in an area, and an embedded image output unit that outputs the image in which the digital watermark is embedded by the digital watermark superimposing unit.

  A digital watermark embedding method according to a fourth invention includes a reference image input unit, a registration unit, an image input unit, an image search unit, a digital watermark superimposing unit, and an embedded image output unit, and a specific ID for the image. An electronic watermark embedding method in an electronic watermark embedding device for embedding an electronic watermark to be represented, wherein the reference image input unit inputs a reference image for indicating a specific two-dimensional pattern as digital data, and the registration unit Storing the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image in the storage unit, the image input A unit that inputs an image to be embedded with a digital watermark as digital data, and the image search unit is input by the image input unit The position coordinates of each feature point are extracted from the image, the local feature amount is detected from the position of each feature point, and correspondence with the feature point stored in the storage unit is performed by collating the local feature amount. A step of identifying which of the reference images the image input by the image input unit corresponds to from the result of the association of the feature points; and the identification result of the digital watermark superimposing unit by the image search unit And embedding a digital watermark in a specific area of the image input by the image input unit, and the embedded image output unit includes the image embedded with the digital watermark by the digital watermark superimposing unit. Outputting.

  An electronic watermark detection apparatus according to a fifth aspect of the present invention is an electronic watermark detection apparatus for detecting an embedded electronic watermark and reading ID information represented by the electronic watermark for an image embedded with an electronic watermark, A reference image input unit for inputting a reference image for indicating a specific two-dimensional pattern as digital data, position coordinates of each feature point extracted from the reference image, and local feature amount detected from the position of each feature point A registration unit that stores the four corner position coordinates of the reference image in a storage unit, an image input unit that inputs an image to be detected as a digital watermark as digital data, and an image input by the image input unit The position coordinates of each feature point are extracted, the local feature amount is detected from the position of each feature point, and the correspondence with the feature point stored in the storage unit is associated with the local feature. The image search unit for identifying whether the image input by the image input unit corresponds to the reference image from the result of the feature point correlation, and the image search unit Based on the difference in position between the feature points that are obtained, the projection transformation matrix parameter representing the projection transformation applied to the image input by the image input unit is estimated, based on the projection transformation matrix parameter, the In the image input by the image input unit, a four-corner coordinate calculation unit that calculates position coordinates corresponding to the four-corner position coordinates of the reference image stored in the storage unit, and the image calculated by the four-corner coordinate calculation unit Based on the position coordinates in the image input by the input unit, the image input by the image input unit is projected onto an image having a specified size when viewed from the front. A projection conversion correction unit that corrects and corrects, an electronic watermark detection unit that detects an embedded digital watermark based on the image corrected by the projection conversion correction unit, and reads ID information represented by the digital watermark; and And a result output unit that outputs ID information representing the digital watermark detected by the digital watermark detection unit as digital data.

  A digital watermark detection method according to a sixth invention includes a reference image input unit, a registration unit, an image input unit, an image search unit, a four-corner coordinate calculation unit, a projective transformation correction unit, a digital watermark detection unit, and a result output unit, A digital watermark detection method in a digital watermark detection apparatus for detecting an embedded digital watermark and reading ID information represented by the digital watermark with respect to an image embedded with a digital watermark, wherein the reference image input unit includes: A step of inputting a reference image for showing a specific two-dimensional pattern as digital data, and a position detected by the registration unit from the position coordinates of each feature point extracted from the reference image and the position of each feature point Storing a feature amount and four-corner position coordinates of the reference image in a storage unit; and the image input unit digitally detects an image for which a digital watermark is to be detected. And the image search unit extracts the position coordinates of each feature point from the image input by the image input unit, detects a local feature amount from the position of each feature point, and stores it in the storage unit Correspondence with the stored feature points is performed by collating the local feature amounts, and the image input by the image input unit corresponds to any of the reference images based on the result of the feature point association. A projection that is added to the image input by the image input unit based on a difference in position between the feature points associated by the image search unit. The reference image stored in the storage unit in the image input by the image input unit based on the projection conversion matrix parameter is estimated based on the projection conversion matrix parameter representing the conversion. Calculating the position coordinates corresponding to the four corner position coordinates; and the projective transformation correction unit based on the position coordinates in the image input by the image input unit calculated by the four corner coordinate calculation unit. A step of projecting and correcting an image input by the unit into a predetermined size image when viewed from the front, and the digital watermark detecting unit is embedded based on the image corrected by the projective transformation correcting unit. Detecting the digital watermark and reading the ID information represented by the digital watermark; and the result output unit outputting the ID information representing the digital watermark detected by the digital watermark detection unit as digital data; ,including.

  In the digital watermark detection apparatus and the digital watermark detection method, the four corner coordinate calculation unit may use a least square algorithm based on RANSAC when estimating the projective transformation matrix parameters.

  A program according to a seventh aspect of the invention is a program for causing a computer to function as each part of the digital watermark embedding apparatus.

  A program according to an eighth invention is a program for causing a computer to function as each part of the digital watermark detection apparatus.

  According to the digital watermark embedding device, method, and program of the present invention, the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image Is stored in the storage unit, and the digital watermark is embedded in a specific area of the reference image, so that the digital watermark can be detected stably with respect to the image without adding a frame for the digital watermark to the image. The effect that can be embedded is obtained.

  According to the digital watermark detection apparatus, method, and program of the present invention, the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corners of the reference image The position coordinates are stored in the storage unit, the position coordinates of each feature point are extracted from the image for which the digital watermark is detected, the local feature amount is detected from the position of each feature point, and stored in the storage unit Matching with feature points is performed by collating local feature amounts to identify which of the reference images the image corresponds to, and projective transformation matrix parameters estimated based on the difference in position between feature points. Based on the position coordinates corresponding to the four corner position coordinates of the reference image stored in the storage unit in the image based on the image, based on the position coordinates in the image, the image having a specified size when viewed from the front. Project to image In other words, the embedded digital watermark is detected based on the corrected image, and the ID information represented by the digital watermark is read, so that the frame for the digital watermark is not added to the image. There is an effect that the digital watermark can be detected stably from the image.

It is a block diagram which shows the structure of the digital watermark embedding apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the digital watermark detection apparatus which concerns on 1st Embodiment. It is a flowchart which shows the digital watermark embedding process routine in the digital watermark embedding apparatus which concerns on 1st Embodiment. It is a flowchart which shows the digital watermark detection process routine in the digital watermark detection apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the digital watermark embedding apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the digital watermark detection process routine in the digital watermark detection apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the digital watermark detection process routine in the digital watermark detection apparatus which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Outline of Embodiment of the Present Invention>
The embodiment of the present invention relates to a technique for facilitating detection of a digital watermark when projective transformation is performed on an image in which the digital watermark is embedded.

  In order to detect a digital watermark from an image taken by a camera, projective transformation is required, and for the projective transformation, information on the four corners of the image is required. In the conventional technique, a frame is provided on the image to identify the four corner information. In the embodiment of the present invention, the position coordinates and the four corner position coordinates of the feature points of the image are registered in advance, and the four corner position coordinates are obtained in accordance with the association of the feature points.

  In the present embodiment, when embedding a digital watermark in an image, the feature points of the target image are detected, the coordinates of the detected feature points, the local feature amounts related to the feature points, and the four corner positions of the image Register the coordinates. Then, with respect to an image in which the coordinates of each feature point, the local feature amount relating to each feature point, and the four corner position coordinates of the image are registered, a digital watermark is embedded in the entire image, and the image is printed and distributed.

  In the embodiment of the present invention, when detecting a digital watermark, a feature point is extracted from an image captured by a camera and embedded with the digital watermark, and the local feature amount obtained from the feature point is used to extract the feature point. Identify which of the registered images the image corresponds to. Based on the position of each feature point, the distortion (positional deviation) of the registered image to the position of the corresponding feature point is obtained as a projective transformation matrix. Then, based on the projective transformation matrix, the four-corner position coordinates of the digital watermark embedding position are back-calculated to normalize the image in which the digital watermark is embedded into a specific scale image viewed from the front.

  Accordingly, it is possible to stably detect the digital watermark for capturing an image from an oblique direction without using a frame for the digital watermark.

  In the above method, it is necessary to determine in advance a reference image to be embedded with a digital watermark. For example, if you register a private brand logo of a specific company as a reference image and embed an electronic watermark with a different ID for each product in a registered logo and paste it, the product can be found just by photographing the logo with a camera. It is possible to specify what is, and to provide detailed information on the product to the user.

  In addition, the private brand logo can be limited to at most several types of patterns, and the identification thereof is relatively easy, so that the false identification rate of the logo and the false detection rate of the digital watermark can be kept very small.

  In the present embodiment, a case where the present invention is applied to an electronic watermark embedding apparatus that embeds an electronic watermark in a reference image and an electronic watermark detection apparatus that detects an electronic watermark from an image embedded with an electronic watermark will be described as an example.

<First embodiment of the present invention>

(Configuration of the digital watermark embedding device according to the first embodiment)
A configuration of the digital watermark embedding device according to the first embodiment will be described. The digital watermark embedding apparatus 100 according to the first embodiment is configured by a computer including a CPU, a RAM, and a ROM that stores a program for executing a digital watermark embedding process routine described later and various data. I can do it. Functionally, the digital watermark device 100 includes a reference image input unit 10, a calculation unit 20, and an embedded image output unit 30, as shown in FIG. The digital watermark embedding device 100 is a device for embedding a digital watermark representing a specific ID in an image. In the first embodiment, an example in which an image to be embedded with a digital watermark is predetermined as a single image pattern, and the image to be embedded and the reference image are the same as an example.

  The reference image input unit 10 inputs a reference image for indicating a specific two-dimensional pattern as digital data. Specifically, the reference image input unit 10 inputs a reference image to be embedded with a digital watermark as digital data, and outputs the digital image to a registration unit 22 of the arithmetic unit 20 described later.

  The computing unit 20 includes a registration unit 22, a storage unit 23, and a digital watermark superimposing unit 24.

  The registration unit 22 includes the position coordinates of each feature point extracted from the reference image received by the reference image input unit 10, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image. It memorize | stores in the memory | storage part 23 mentioned later.

  Specifically, first, the registration unit 22 extracts each feature point of the reference image input by the reference image input unit 10. Then, the registration unit 22 registers the extracted position coordinates of each feature point, the local feature amount of each feature point, and the four corner position coordinates of the reference image in the storage unit 23 as an identification dictionary.

  Here, the four corner position coordinates of the reference image are defined by information that can specify the coordinates of the four points of the rectangle, for example, the coordinates of the four points, or the start point coordinates and the size of the image. For example, when the four corner position coordinates are the coordinates of the four corner positions of the reference image itself, the four corner position coordinates are also automatically registered by inputting the reference image.

  On the other hand, when defining the four corner positions at arbitrary positions on the reference image, the four corner position coordinates are input by the manual operation in the registration unit 22. At this time, the coordinate values of the four corner position coordinates may be input as text, or may be input by designating the position with a pointing device or the like while viewing the image. For the registration of the four corner position coordinates, for example, a method disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2015-201123) can be used.

  In the storage unit 23, the position coordinates of each feature point extracted from the reference image received by the reference image input unit 10, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image are stored. It is stored as an identification dictionary. The storage unit 23 may be referred to via the Internet using, for example, a server.

  The digital watermark superimposing unit 24 embeds a digital watermark in a specific area of the reference image obtained by the reference image input unit 10.

  Specifically, the digital watermark superimposing unit 24 embeds a digital watermark representing a specific ID in the image with respect to the reference image obtained by the reference image input unit 10. Here, the digital watermark superimposing unit 24 embeds the digital watermark as the digital watermark embedding position, for example, in the entire rectangular area represented by connecting the four corner points of the reference image input by the reference image input unit 10.

  Note that a digital watermark may be embedded in a specific area that can be calculated backward from the rectangular area of the reference image according to a predetermined rule. In this case, it is necessary to store a specific area designation rule in the storage unit 23 in the registration unit 22 and the registration unit 62 of the digital watermark detection apparatus 110 described later.

  As a digital watermark embedding method, for example, the method disclosed in Non-Patent Document 1 can be used. In addition, a secret key (for example, information on pseudorandom number generation in spread spectrum modulation in the digital watermark embedding algorithm) used when generating a digital watermark pattern for embedding a digital watermark is described later. It is also used in the digital watermark detection unit 70 of the detection device 110.

  Here, there is a method in which the secret key is changed for each reference image in which the position coordinates and the like of each feature point are registered by the registration unit 22, and the digital watermark detection apparatus 110 described later selects and uses the secret key according to the image search result. Conceivable. In this case, the number of IDs that can be embedded with a digital watermark can be increased by the number of secret keys. Therefore, it is an effective method when it is necessary to use a lot of IDs.

  The embedded image output unit 30 outputs the reference image embedded with the digital watermark by the digital watermark superimposing unit 24 as an embedded image. As an output destination, for example, in addition to outputting as a printed matter with a printer or the like, it may be possible to temporarily store an image file on an electronic medium such as an HDD and then display the image on a display or perform printer printing.

(Configuration of the digital watermark detection apparatus according to the first embodiment)
Next, the configuration of the digital watermark detection apparatus according to the first embodiment will be described. The digital watermark detection apparatus 110 according to the first embodiment is configured by a computer including a CPU, a RAM, and a ROM that stores a program and various data for executing a digital watermark detection processing routine described later. I can do it. Functionally, the digital watermark detection apparatus 110 includes a reference image input unit 50, an image input unit 52, a calculation unit 60, and a result output unit 80 as shown in FIG. The digital watermark detection apparatus 110 is an apparatus for detecting an embedded digital watermark in an image in which the digital watermark is embedded and reading ID information represented by the digital watermark.

  The reference image input unit 50 inputs a reference image for indicating a specific two-dimensional pattern as digital data. The reference image input unit 50 inputs an image having the same pattern as the image in which the digital watermark is embedded as digital data, and outputs the digital data to the registration unit 62 of the calculation unit 60. This performs the same processing as the reference image input unit 10 of the digital watermark embedding apparatus 100, and the content of the reference image to be input is the same. Therefore, the reference image input unit 50 and the reference image input unit 50 of the digital watermark embedding apparatus 100 may be shared.

  The image input unit 52 inputs an image to be detected as a digital watermark as digital data. And the image input part 52 outputs an image to the image search part 64 of the calculating part 60 mentioned later. For example, an image to be detected as a digital watermark is photographed and digitally input by a camera such as a smartphone.

  The calculation unit 60 includes a registration unit 62, a storage unit 63, an image search unit 64, a four corner coordinate calculation unit 66, a projective transformation correction unit 68, and a digital watermark detection unit 70.

  Similar to the registration unit 22 of the digital watermark embedding device 100, the registration unit 62 is detected from the position coordinates of each feature point extracted from the reference image input by the reference image input unit 50 and the position of each feature point. The local feature amount and the four corner position coordinates of the reference image are stored in the storage unit 63 described later.

  As a method for the registration unit 62 to acquire the position coordinates of each feature point, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image from the reference image, for example, in Patent Document 1 described above. The indicated method can be used. The registration unit 62 performs the same processing as the registration unit 22 of the digital watermark embedding apparatus 100, and the content of the reference image to be registered needs to be the same. Therefore, the registration unit 62 may be configured to be shared with the registration unit 22 of the digital watermark embedding apparatus 100.

  The storage unit 63 stores the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image as an identification dictionary. The storage unit 63 may be referred to via the Internet using a server or the like.

  The image search unit 64 extracts the position coordinates of each feature point from the image input by the image input unit 52, detects the local feature amount from the position of each feature point, and the feature points stored in the storage unit 63 Are matched by collating local feature amounts. Then, the image search unit 64 identifies which of the reference images the image input by the image input unit 52 corresponds to from the result of the feature point association.

  Specifically, the image search unit 64 retrieves a reference image identification dictionary from the storage unit 63 and performs a search by collating with the image input by the image input unit 52. Here, the technique disclosed in Patent Document 1 can be used. According to this method, it is possible to identify which of the reference images registered in advance is a pattern included in the image input by the image input unit 52, and to be registered in advance as feature points detected from the subject. It is also possible to associate feature points of the subject.

  The four corner coordinate calculation unit 66 performs projective transformation applied to the image input by the image input unit 52 based on the difference in position between the feature points associated with the reference image identified by the image search unit 64. Estimate the projective transformation matrix parameters to represent. The four-corner coordinate calculation unit 66 then positions coordinates corresponding to the four-corner position coordinates of the reference image stored in the storage unit 63 in the image input by the image input unit 52 based on the estimated projective transformation matrix parameters. Is calculated.

  For example, the four-corner coordinate calculation unit 66 can use a least squares algorithm based on RANSAC when estimating the projective transformation matrix parameters. By applying a least squares algorithm based on RANSAC (Non-Patent Document 2: Simon JD Prince “Computer Vision: Model, Learning, and Interface”, Cambridge University Press, pp.342-345, 2012), parameters of the projective transformation matrix Can be accurately estimated.

  Then, the four-corner coordinate calculation unit 66 uses the projection transformation matrix parameter estimated as to which position of the image input by the image input unit 52 the four-corner position coordinates of the reference image stored in the storage unit 63 are associated with. Calculate back to the base. Then, the four corner coordinate calculation unit 66 outputs the result of the position coordinates corresponding to the four corner position coordinates to the projective transformation correction unit 68.

  The projective transformation correction unit 68 is based on the position coordinates in the image input by the image input unit 52 calculated by the four-corner coordinate calculation unit 66 and has a specified size when the image input by the image input unit 52 is viewed from the front. Correct by projective conversion to the image.

  Accordingly, the image input by the image input unit 52 can be normalized to the same orientation and size as the reference image stored in the storage unit 63 regardless of the shooting direction of the camera. Further, a portion outside the rectangular area formed by connecting the four corner position coordinates is clipped because it is not necessary in the processing of the digital watermark detection unit 70 described later (however, the digital watermark superimposing unit 24 of the digital watermark embedding device 100 performs the digital watermarking). In the case where the entire embedded image is not the entire image, clipping is performed based on the specific rule for the embedded region).

  The digital watermark detection unit 70 detects an embedded digital watermark based on the image corrected by the projective transformation correction unit 68 and reads ID information represented by the digital watermark.

  Here, the digital watermark detection unit 70 applies the secret key used in the digital watermark superimposing unit 24 of the digital watermark embedding apparatus 100 here. Specifically, the digital watermark method described in Non-Patent Document 1 can be used. Then, the digital watermark detection unit 70 outputs the detection result of the digital watermark to the result output unit 80.

  The result output unit 80 outputs ID information representing the digital watermark detected by the digital watermark detection unit 70 as digital data. Alternatively, the result output unit 80 outputs Web URL information associated with the ID information. In this case, a table for converting ID information and URL information is saved in the storage area, and the table is referred to each time.

<Operation of the digital watermark embedding apparatus according to the first embodiment>

  Next, the operation of the digital watermark embedding apparatus 100 according to the embodiment of the present invention will be described. When the reference image is input to the digital watermark embedding apparatus 100, the digital watermark embedding apparatus 100 executes a digital watermark embedding process routine shown in FIG.

  First, in step S100, the reference image input unit 10 receives the input reference image.

  In step S102, the registration unit 22 determines the position coordinates of each feature point extracted from the reference image received in step S100, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image. Is stored in the storage unit 23.

  In step S104, the digital watermark superimposing unit 24 embeds the digital watermark in a specific area of the reference image received in step S100.

  In step S106, the embedded image output unit 30 outputs the reference image embedded with the digital watermark in step S104 as an embedded image, and ends the process.

<Operation of the digital watermark detection apparatus according to the first embodiment>

  Next, the operation of the digital watermark detection apparatus 110 according to the embodiment of the present invention will be described. When the reference image and the image for which the digital watermark is to be detected are input to the digital watermark detection apparatus 110, the digital watermark detection apparatus 110 executes a digital watermark detection processing routine shown in FIG.

  In step S200, the reference image input unit 50 receives the input reference image.

  In step S202, the registration unit 62 determines the position coordinates of each feature point extracted from the reference image received in step S200, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image. Is stored in the storage unit 63.

  In step S <b> 204, the image input unit 52 receives an input image that is a target for detecting a digital watermark.

  In step S206, the image search unit 64 extracts the position coordinates of each feature point from the image received in step S204, detects the local feature amount from the position of each feature point, and stores the feature stored in the storage unit 63. Correspondence with points is performed by collating local feature amounts. Then, the image search unit 64 identifies which of the reference images the image received in step S204 corresponds to from the result of the feature point association.

  In step S208, the four-corner coordinate calculation unit 66 performs projective transformation added to the image received in step S204 based on the difference in position between the feature points associated with the reference image identified in step S206. Projective transformation matrix parameters representing are estimated. Then, the four corner coordinate calculation unit 66 calculates position coordinates corresponding to the four corner position coordinates of the reference image stored in the storage unit 63 in the image received in step S204, based on the estimated projective transformation matrix parameters. To do.

  In step S210, the projective transformation correcting unit 68 performs projective transformation on the image received in step S204 to an image having a predetermined size as viewed from the front based on the position coordinates calculated in step S208 and corrects the image.

  In step S212, the digital watermark detection unit 70 detects the digital watermark embedded in the image received in step S204 based on the image corrected in step S210, and reads ID information represented by the digital watermark.

  In step S214, the result output unit 80 outputs the ID information representing the digital watermark detected in step S212 as digital data, and ends the process.

  As described above, according to the digital watermark embedding device according to the first embodiment, the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, By storing the four corner position coordinates of the reference image in the storage unit and embedding the digital watermark in a specific area of the reference image, the digital watermark can be added to the image without adding a frame for the digital watermark to the image. Can be embedded.

  Further, according to the digital watermark detection apparatus according to the first embodiment, the position coordinates of each feature point are extracted from the image that is the target for detecting the digital watermark, and the local feature amount is detected from the position of each feature point. , Matching with the feature points stored in the storage unit is performed by collating local feature amounts, identifying which of the reference images the image corresponds to, and based on the difference in position between the feature points Based on the estimated projective transformation matrix parameters, position coordinates corresponding to the four corner position coordinates of the reference image stored in the storage unit in the image are calculated, and based on the position coordinates in the image, the image is displayed in front. Projective conversion to an image of a prescribed size as seen from the image, correction is performed, embedded digital watermark is detected based on the corrected image, and ID information represented by the digital watermark is read to There may not have been added to the image, it is possible to detect the watermark from the image.

  In addition, when detecting a digital watermark by shooting a digital watermark embedded image with a camera, the digital watermark can be detected robustly even when shooting from an oblique direction without explicitly adding a frame. Can do.

<Second embodiment of the present invention>
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in that there are a plurality of image patterns of images to be embedded.

(Configuration of the digital watermark embedding device of the second embodiment)
A configuration of the digital watermark embedding apparatus according to the second embodiment will be described. As shown in FIG. 5, the digital watermark embedding device 200 according to the second embodiment includes a CPU, a RAM, a ROM that stores a program and various data for executing a digital watermark embedding process routine to be described later, Can be configured with a computer including Functionally, the digital watermarking device 200 includes a reference image input unit 10, an image input unit 212, a calculation unit 220, and an embedded image output unit 30, as shown in FIG. As shown in FIG. 5, the digital watermark embedding apparatus 200 according to the second embodiment includes an image input unit 212 and an image search unit 223 in embedding a digital watermark, as compared with the first embodiment. Different.

  The reference image input unit 210 inputs a reference image for indicating a specific two-dimensional pattern as digital data. Here, in the reference image input unit 210, when there are a plurality of reference images, input is repeated by the number of patterns. In the second embodiment, a case where a plurality of reference images exist and a plurality of reference images are input by the reference image input unit 210 will be described as an example.

  The image input unit 212 inputs an image to be embedded with a digital watermark as digital data. And the image input part 52 outputs an image to the image search part 64 of the calculating part 60 mentioned later.

  The calculation unit 220 includes a registration unit 222, a storage unit 23, an image search unit 223, and a digital watermark superimposing unit 24.

  The registration unit 222 includes the position coordinates of each feature point extracted from the reference image input by the reference image input unit 210, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image. And stored in the storage unit 23. Since a plurality of patterns of reference images are input by the reference image input unit 210, registration in the storage unit 23 is repeated by the number of image patterns.

  The image search unit 223 extracts the position coordinates of each feature point from the image input by the image input unit 212, detects a local feature amount from the position of each feature point, and the feature points stored in the storage unit 23 Are matched by collating local feature amounts. Then, the image search unit 223 identifies which of the reference images the image input by the image input unit 212 corresponds to from the result of the feature point association. Note that the search processing by the image search unit 223 is not automatically performed by the machine, but may be performed manually by a human with visual confirmation.

  The digital watermark superimposing unit 24 embeds a digital watermark in a specific area of the image obtained by the image input unit 212 based on the identification result by the image search unit 223.

  Specifically, when the image search unit 223 identifies that the digital watermark superimposing unit 24 corresponds to any reference image, the digital watermark superimposing unit 24 applies a digital watermark representing a specific ID to the image obtained by the image input unit 212. Is embedded in the image. Here, the digital watermark superimposing unit 24 embeds the digital watermark as the digital watermark embedding position, for example, in the entire rectangular area represented by connecting the four corner points of the reference image identified by the image search unit 223.

  The embedded image output unit 30 outputs the image embedded with the digital watermark by the digital watermark superimposing unit 24 as an embedded image.

  Note that the configuration of the digital watermark detection apparatus according to the second embodiment is the same as the configuration of the digital watermark detection apparatus 110 according to the first embodiment, and thus the same reference numerals are given and description thereof is omitted.

  <Operation of the digital watermark embedding apparatus according to the second embodiment>

  Next, the operation of the digital watermark embedding apparatus 200 according to the second embodiment will be described. When a plurality of reference images and an image for which a digital watermark is to be detected are input to the digital watermark embedding apparatus 200, the digital watermark embedding apparatus 200 executes a digital watermark embedding process routine shown in FIG.

  First, in step S300, the reference image input unit 210 receives a plurality of input reference images.

  In step S302, the registration unit 22 sets one reference image from the plurality of reference images received in step S300, and detects from the position coordinates of each feature point extracted from the reference image and the position of each feature point. The local feature amount and the four corner position coordinates of the reference image are stored in the storage unit 23.

  In step S303, the registration unit 22 determines whether or not the process of step S302 has been executed for all of the plurality of reference images received in step S300. When the process of step S302 is executed for all reference images, the process proceeds to step S304. On the other hand, if there is a reference image that has not been subjected to the process of step S302, the process returns to step S302.

  In step S <b> 304, the image input unit 212 receives an input image that is a target for detecting a digital watermark.

  In step S306, the image search unit 223 extracts the position coordinates of each feature point from the image received in step S304, detects a local feature amount from the position of each feature point, and stores the feature stored in the storage unit 23. Correspondence with points is performed by collating local feature amounts. Then, the image search unit 223 identifies which of the reference images the image received in step S304 corresponds to from the result of the feature point association.

  In step S308, the digital watermark superimposing unit 24 embeds the digital watermark in a specific area of the image received in step S304.

  In step S310, the embedded image output unit 30 outputs the image in which the digital watermark is embedded in step S308, and ends the process.

<Operation of the digital watermark detection apparatus according to the second embodiment>

  Next, the operation of the digital watermark detection apparatus according to the embodiment of the present invention will be described. When a plurality of reference images and an image to be detected as a digital watermark are input to the digital watermark detection apparatus according to the second embodiment, the digital watermark detection apparatus executes the digital watermark detection processing routine shown in FIG. Run.

  In step S400, the reference image input unit 50 receives a plurality of input reference images.

  In step S402, the registration unit 62 sets one reference image among the reference images received in step S400, and is detected from the position coordinates of each feature point extracted from the reference image and the position of each feature point. The local feature amount and the four corner position coordinates of the reference image are stored in the storage unit 63.

  In step S403, the registration unit 62 determines whether or not the processing in step S402 has been executed for all of the plurality of reference images received in step S400. When the process of step S402 is executed for all reference images, the process proceeds to step S204. On the other hand, if there is a reference image that has not been subjected to the process of step S402, the process returns to step S402.

  Note that the other configuration and operation of the document evaluation apparatus according to the second embodiment are the same as those in the first embodiment, and thus the description thereof is omitted.

  As described above, according to the digital watermark embedding device according to the second embodiment, the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, The four corner position coordinates of the reference image are stored in the storage unit, the image to be embedded with the digital watermark is input as digital data, the position coordinates of each feature point are extracted from the input image, and the position of each feature point is extracted. The local feature amount is detected, and the feature point stored in the storage unit is associated by collating the local feature amount. From the result of the feature point correspondence, the input image is any of the reference images. It is possible to embed a digital watermark into an image without identifying a frame for the digital watermark by embedding a digital watermark in a specific area of the input image by identifying whether it is applicable.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention.

  For example, in the second embodiment, the case where a plurality of reference images are input has been described as an example. However, the present invention is not limited to this, and one reference image may be input.

  In the above embodiment, the case where the digital watermark embedding apparatus and the digital watermark detection apparatus include the storage unit has been described. However, the present invention is not limited to this. For example, the storage unit is provided in an external device of the digital watermark embedding device and the digital watermark detection device, and the digital watermark embedding device and the digital watermark detection device refer to the storage unit by communicating with the external device using communication means. It may be.

  Although the above-described digital watermark embedding device and digital watermark detection device have a computer system inside, if the “computer system” uses a WWW system, a homepage providing environment (or display environment) Shall also be included.

  In addition, a storage medium storing software program codes for realizing the functions of the embodiment is supplied to the system or apparatus, and the CPU (MPU) of the system or apparatus reads and executes the program codes stored in the storage medium. Can also be realized. In that case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code, for example, CD-ROM, DVD-ROM, CD-R, CD-RW, MO, HDD, etc. constitute the present invention.

DESCRIPTION OF SYMBOLS 10 Reference image input part 20,220 Operation part 22,222 Registration part 23 Storage part 24 Digital watermark superimposition part 30 Embedded image output part 50,210 Reference image input part 52,212 Image input part 60 Calculation part 62 Registration part 63 Storage part 64, 223 Image search unit 66 Four-corner coordinate calculation unit 68 Projective transformation correction unit 70 Digital watermark detection unit 80 Result output unit 100, 200 Digital watermark embedding device 110 Digital watermark detection device

Claims (8)

An electronic watermark embedding device for embedding an electronic watermark representing a specific ID in an image,
A reference image input unit for inputting a reference image for indicating a specific two-dimensional pattern as digital data;
A registration unit that stores in the storage unit the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image;
An image input unit for inputting an image to be embedded with a digital watermark as digital data;
Extracting the position coordinates of each feature point from the image input by the image input unit, detecting a local feature amount from the position of each feature point, and associating with the feature point stored in the storage unit, An image search unit for identifying which of the reference images the image input by the image input unit corresponds to as a result of matching of the feature points, by performing local feature amount matching;
A digital watermark superimposing unit that embeds a digital watermark in a specific region of the image input by the image input unit based on the identification result by the image search unit;
An embedded image output unit for outputting the image in which the digital watermark is embedded in the digital watermark superimposing unit;
An electronic watermark embedding device including: A digital watermark detection apparatus for detecting an embedded digital watermark and reading ID information represented by the digital watermark with respect to an image in which the digital watermark is embedded,
A reference image input unit for inputting a reference image for indicating a specific two-dimensional pattern as digital data;
A registration unit that stores in the storage unit the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image;
An image input unit that inputs an image to be detected as a digital watermark as digital data;
Extracting the position coordinates of each feature point from the image input by the image input unit, detecting a local feature amount from the position of each feature point, and associating with the feature point stored in the storage unit, An image search unit for identifying which of the reference images the image input by the image input unit corresponds to as a result of matching of the feature points, by performing local feature amount matching;
Based on a difference in position between the feature points associated by the image search unit, a projective transformation matrix parameter representing a projective transformation added to the image input by the image input unit is estimated, and the projective transformation Four corner coordinate calculation unit for calculating position coordinates corresponding to the four corner position coordinates of the reference image stored in the storage unit in the image input by the image input unit based on matrix parameters;
Based on the position coordinates in the image input by the image input unit calculated by the four-corner coordinate calculation unit, the image input by the image input unit is projectively converted into an image having a specified size as viewed from the front. A projective transformation correction unit that corrects
An electronic watermark detection unit that detects an embedded digital watermark based on the image corrected by the projective transformation correction unit and reads ID information represented by the digital watermark;
A result output unit that outputs ID information representing the digital watermark detected by the digital watermark detection unit as digital data;
An electronic watermark detection apparatus including: The digital watermark detection apparatus according to claim 2 , wherein the four-corner coordinate calculation unit uses a least squares algorithm based on RANSAC when estimating the projective transformation matrix parameters. In a digital watermark embedding device for embedding a digital watermark representing a specific ID in an image, including a reference image input unit, a registration unit, an image input unit, an image search unit, a digital watermark superimposing unit, and an embedded image output unit An electronic watermark embedding method,
The reference image input unit inputting a reference image for indicating a specific two-dimensional pattern as digital data;
When the registration unit stores the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image in the storage unit,
The image input unit inputting an image to be embedded with a digital watermark as digital data;
The image search unit extracts the position coordinates of each feature point from the image input by the image input unit, detects a local feature amount from the position of each feature point, and stores the feature points stored in the storage unit Identifying the image corresponding to the reference image corresponding to the image input by the image input unit based on the result of the feature point matching,
The digital watermark superimposing unit embeds a digital watermark in a specific area of the image input by the image input unit based on the identification result by the image search unit;
The embedded image output unit outputting the image in which the digital watermark is embedded in the digital watermark superimposing unit;
An electronic watermark embedding method including: A reference image input unit, a registration unit, an image input unit, an image search unit, a four-corner coordinate calculation unit, a projective transformation correction unit, a digital watermark detection unit, and a result output unit. A digital watermark detection method in a digital watermark detection apparatus for detecting a digital watermark and reading ID information represented by the digital watermark,
The reference image input unit inputting a reference image for indicating a specific two-dimensional pattern as digital data;
Storing the position coordinates of each feature point extracted from the reference image, the local feature amount detected from the position of each feature point, and the four corner position coordinates of the reference image in the storage unit; ,
The image input unit inputting an image to be detected as a digital watermark as digital data;
The image search unit extracts the position coordinates of each feature point from the image input by the image input unit, detects a local feature amount from the position of each feature point, and stores the feature points stored in the storage unit Identifying the image corresponding to the reference image corresponding to the image input by the image input unit based on the result of the feature point matching,
Projection transformation matrix parameters representing the projection transformation applied to the image input by the image input unit based on the difference in position between the feature points associated by the image search unit by the four corner coordinate calculation unit. And calculating position coordinates corresponding to the four corner position coordinates of the reference image stored in the storage unit in the image input by the image input unit based on the projective transformation matrix parameter;
Based on the position coordinates in the image input by the image input unit calculated by the four-corner coordinate calculation unit, the projective transformation correction unit has a specified size when the image input by the image input unit is viewed from the front. A projective transformation to the image of the size and correcting,
The digital watermark detection unit detects an embedded digital watermark based on the image corrected by the projective transformation correction unit, and reads ID information represented by the digital watermark;
The result output unit outputting ID information representing the digital watermark detected by the digital watermark detection unit as digital data;
An electronic watermark detection method including: 6. The digital watermark detection method according to claim 5 , wherein the step of calculating the position coordinates by the four-corner coordinate calculation unit uses a least squares algorithm based on RANSAC when estimating the projective transformation matrix parameters. A program for causing a computer to function as each unit of the digital watermark embedding apparatus according to claim 1 . The program for functioning a computer as each part of the electronic watermark detection apparatus of Claim 2 or Claim 3 .

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