JP6445796B2 - Image obfuscation apparatus, image obfuscation method, program, and recording medium - Google Patents

Description

  The present invention mainly relates to an apparatus for obfuscating an image.

  Recently, contents including images (for example, electronic book contents such as “cartoon” and “novel including illustration”) are sold on various WEB sites.

  In addition, various obfuscation techniques (for example, the technique disclosed in Patent Document 1) that can be used to prevent such an image from being read by anyone other than a specific person (for example, a content purchaser) are proposed. Has been.

  An example of such an obfuscation technique is a technique schematically shown in FIG. FIG. 17 is a diagram schematically illustrating a conventional obfuscation technique.

  As shown in FIG. 17, this technique is a technique for obfuscating an original image by performing a scramble process on the original image transformed from the frequency domain to the spatial domain (for example, inverse discrete cosine transformed).

International Publication No. 2012/127578 (Released on September 27, 2012)

  However, as shown in FIG. 17, in this conventional technique, the original image and the obfuscated image are subjected to a decoding process due to the processing when the obfuscated image is stored (specifically, discrete cosine transform). Therefore, there is a drawback that a difference is generated between the decoded image and the decoded image (that is, deterioration of image quality occurs).

  The present invention has been made in view of the above problems, and its main object is to realize an image obfuscation apparatus that obfuscates an image so that little or no degradation in image quality is visually recognized after restoration. .

  An image obfuscation apparatus according to an aspect of the present invention includes a reading unit that reads an image that has been subjected to a process of converting to a frequency component, and an obfuscation unit that performs an obfuscation process on the image. Is configured to perform the obfuscation process on the image by replacing all or part of the plurality of blocks obtained by dividing the image with other blocks in the image.

  An image obfuscation method according to an aspect of the present invention is an image obfuscation method executed by an apparatus, which includes a reading step of reading an image that has been subjected to processing for conversion to a frequency component, and subjecting the image to obfuscation processing. An obfuscation step, and the obfuscation step performs obfuscation processing on the image by replacing all or part of the plurality of blocks obtained by dividing the image with other blocks in the image. .

  The image obfuscation apparatus and the image obfuscation method according to one embodiment of the present invention have an effect that an image can be obfuscated so that little or no degradation in image quality is visually recognized after restoration.

It is a block diagram of each apparatus which comprises the system which concerns on Embodiment 1-3 of this invention. It is a flowchart which shows operation | movement of the content conversion server contained in the system which concerns on Embodiment 1-3. It is the figure which showed the function used in order for the content conversion server which concerns on Embodiment 1-3 to divide | segment the image (original image) contained in an electronic book content into a some block. It is a figure for demonstrating the method in which the content conversion server which concerns on Embodiments 1-3 divides | segments the image contained in an electronic book content into a some block. It is a figure regarding Embodiments 1-3, and is a figure for demonstrating that the appearance of an obfuscated image changes according to how to determine the size of the block located in the outer edge part of an original image. FIG. 5 is a diagram for explaining a method in which the content conversion server according to the first embodiment creates a specified image group (an image group used for restoring an original image from an obfuscated image) from an original image. It is a figure for demonstrating the method in which the content conversion server which concerns on Embodiments 1-3 produces an obfuscated image from an original image. It is the figure which illustrated typically the data containing the decoding key (Decryption key for decoding an original image) which the content conversion server which concerns on Embodiments 1-3 produces. 4 is a flowchart illustrating an operation of a tablet terminal (terminal used for browsing electronic book content) included in the system according to the first embodiment. It is a figure for demonstrating the method the tablet terminal which concerns on Embodiment 1 restore | restores an original image, without producing deterioration from an obfuscated image. FIG. 10 is a diagram related to Embodiments 1 to 3, for explaining pixel values (boundary pixel values) of boundary pixels (pixels adjacent to pixels of blocks adjacent to the block) of each block of an obfuscated image that has been up-sampled. FIG. It is a figure for demonstrating how the tablet terminal concerning Embodiment 1 displays the image contained in an electronic book content. FIG. 10 is a diagram for describing a method in which the content conversion server according to the second embodiment creates a specified image (an image used for restoring an original image from an obfuscated image) from an original image. It is a figure for demonstrating the method the tablet terminal which concerns on Embodiment 2 restore | restores an original image, without producing deterioration from an obfuscated image. FIG. 10 is a diagram for explaining a method in which a content conversion server according to a third embodiment creates prescribed data (data used for restoring an original image from an obfuscated image) from an original image. It is a figure for demonstrating the method the tablet terminal which concerns on Embodiment 3 restore | restores an original image, without producing deterioration from an obfuscated image. It is the figure which showed the conventional obfuscation technique typically.

<Embodiment 1>
Hereinafter, a system according to an embodiment of the present invention will be described with reference to FIGS.

(Outline of the system according to this embodiment)
An overview of a system according to the present embodiment (hereinafter simply referred to as “system”) will be described with reference to FIG. FIG. 1 is a block diagram of each device constituting the system.

  As shown in FIG. 1, the system includes a content conversion server 100, a book sales server 200, and a tablet terminal 300.

  The content conversion server 100 is an apparatus that performs encryption of electronic book content (specifically, obfuscation of images and text included in the electronic book content).

  The book sales server 200 is a server constituting an electronic book site, and the book sales server 200 stores a large number of electronic book contents in an encrypted state. The book sales server 200 decrypts the encrypted electronic book content and the images and text in the electronic book content toward the terminal (tablet terminal 300 or the like) on which the operation for purchasing the electronic book content has been performed. And a decryption key for transmitting.

  The tablet terminal 300 is a terminal that can be used for browsing electronic book content.

(Configuration of each device included in the system)
Next, the configuration of each device included in the system will be described with reference to FIG.

(Content conversion server 100)
The content conversion server 100 includes a storage unit 110, a control unit 120, and a communication I / F unit 130.

  The storage unit 110 is a recording medium that stores various data such as electronic book content (unencrypted electronic book content) before being registered in the electronic book site.

  The control unit 120 is a CPU that comprehensively controls the entire content conversion server 100.

  The control unit 120 functions as the encryption unit 121 by reading the encryption program recorded in the storage unit 110.

  The encryption unit 121 obfuscates each image included in the electronic book content in addition to the text included in the electronic book content.

  Specifically, the encryption unit 121 replaces the block with another block for each of a plurality of blocks obtained by dividing the image (or the remaining blocks excluding a part of the plurality of blocks). The obfuscation process is performed on the image. That is, the encryption unit 121 performs scramble processing on the image.

  In the present embodiment, the encryption unit 121 also performs the above-described scramble process on an image (such as a JPEG image that has been subjected to discrete cosine transform) that has been subjected to the process of converting to a frequency component. Yes.

  The communication I / F unit 130 is a communication interface provided to enable the content conversion server 100 to perform IP communication with other devices.

(Book sales server 200)
The book sales server 200 includes a storage unit 210, a storage unit 215, a control unit 220, and a communication I / F unit 230. Note that the storage unit 215 and the storage unit 215 may be included in one recording medium or may be included in different recording media.

  The storage unit 210 is a recording area that can be accessed from the outside by specifying a URL. The storage unit 210 stores a large number of electronic book contents (encrypted electronic book contents) registered in the electronic book site.

  The storage unit 215 is a recording area that cannot be accessed from the outside with a URL specified. The storage unit 215 includes bibliographic information of each user (information indicating how many pages of the electronic book content were last viewed by the target user for the purchased electronic book content).

  The control unit 220 is a CPU that comprehensively controls the entire book sales server 200.

  The communication I / F unit 230 is a communication interface provided to enable the book sales server 200 to perform IP communication with other devices.

(Tablet terminal 300)
The tablet terminal 300 includes a storage unit 310, a control unit 320, a communication I / F unit 330, and a touch panel display unit 340.

  The storage unit 310 is a recording medium that stores various data such as an encrypted electronic book content and a decryption key used for decrypting an obfuscated image included in the electronic book content.

  The control unit 320 is a CPU that controls the entire tablet terminal 300.

  The control unit 320 functions as a download processing unit 321, a decryption unit 322, a book display processing unit 323, and a book information upload processing unit 324 by reading a specific program recorded in the storage unit 310. The specific program may be, for example, a script that runs on a web browser application or an electronic book application program.

  The download processing unit 321 downloads the encrypted electronic book content and the decryption key from the book sales server 200.

  The decryption unit 322 decrypts the encrypted electronic book content using the decryption key. Specifically, the decryption unit 322 decrypts text and / or images in a page to be displayed on the touch panel display unit 340 using a decryption key.

  The book display processing unit 323 displays the image and / or text in the page specified by the user on the touch panel display unit 340.

  The bibliographic information upload processing unit 324, when the touch panel display unit 340 accepts an operation for ending the display of the electronic book content, shows information indicating the number of the page that has been displayed (for the user using the tablet terminal 300). Bibliographic information) is uploaded to the book sales server 200.

  The communication I / F unit 330 is a communication interface provided to enable the tablet terminal 300 to perform IP communication with other devices.

  The touch panel display unit 340 is a display device that also functions as an operation device. When touch panel type display unit 340 accepts a touch operation, information corresponding to the content of the touch operation is displayed on touch panel type display unit 340.

  The configuration of each device included in the system has been described above.

(Operation of Content Conversion Server 100)
Next, the operation of the content conversion server 100 will be described with reference to FIGS.

  FIG. 2 is a flowchart illustrating an operation of performing obfuscation processing on an image (original image) included in the electronic book content. FIG. 3 is a diagram illustrating a function used by the content conversion server 100 to divide an original image included in electronic book content into a plurality of blocks. FIG. 4 is a diagram for explaining a method in which the content conversion server 100 divides an original image included in electronic book content into a plurality of blocks. FIG. 5 is a diagram for explaining how the obfuscated image looks different depending on how the size of the block located at the outer edge of the original image is determined.

  FIG. 6 is a diagram for explaining a method in which the content conversion server 100 creates a plurality of bar images (images used to restore an original image from an obfuscated image) from the original image. FIG. 7 is a diagram for explaining a method by which the content conversion server 100 creates an obfuscated image from an original image. FIG. 8 is a diagram schematically and schematically illustrating data including a decryption key (decryption key for decrypting an original image) created by the content conversion server 100 (that is, only the decryption key portion). .

  In FIG. 3, the argument length is a numerical value indicating the vertical (horizontal) size of the original image, and the argument div_num is a numerical value indicating the number of divisions in the vertical direction (horizontal direction). The argument block_min_unit is a specified constant according to the format of the original image, and the argument fraction is a rectangle composed of blocks that are not located at the top or bottom of the original image, based on the vertical (horizontal) size of the original image. This is a numerical value obtained by subtracting the vertical size of a region (the horizontal size of a rectangular region consisting of blocks that are not located at the left or right end of the original image).

  When the encryption unit 121 reads the original image from the electronic book content (reading step), in S1, the encryption unit 121 specifies the vertical and horizontal sizes of the original image, and the number of divisions (number of blocks) of the original image in the vertical and horizontal directions. ). The number of divisions in the vertical direction and the horizontal direction may be, for example, the number input by the administrator of the content conversion server 100, or the number determined by the encryption unit 121 according to some algorithm. . Also, the vertical and horizontal sizes of each block (specifically, each block that does not correspond to the lowermost block or the rightmost block) are specified constants according to the format of the original image (the original image is a JPEG image). In this case, it is desirable that the number of divisions in the vertical direction and the horizontal direction is determined so as to be an integral multiple of “8” (preferably an even multiple).

  In S1, the encryption unit 121, for each of a plurality of blocks defined by the division of the original image, the upper left coordinate of the block in the coordinate system with the upper left coordinate of the original image as the origin and the vertical length of the block. And determine the horizontal size.

  Specifically, the encryption unit 121 calculates the vertical and horizontal sizes of each block using the getBlockLengthCenter function and the getFirstFractionLength function shown in FIG.

  More specifically, the encryption unit 121 uses the getBlockLengthCenter function to calculate the vertical size of each block that is not located at the top or bottom of the original image, and then uses the getFirstFractionLength function to The vertical size of each block located at is calculated, and further the vertical size of each block located at the lower end of the original image is calculated.

  Similarly, the encryption unit 121 calculates the horizontal size of each block that is not located at the right end or the left end of the original image using the getBlockLengthCenter function, and then is located at the left end of the original image using the getFirstFractionLength function. The horizontal size of each block is calculated, and further, the horizontal size of each block located at the right end of the original image is calculated.

  For example, the original image is an image of vertical 128 dots and horizontal 128 dots as shown in FIG. 4, the number of divisions in the vertical direction and the horizontal direction is “4”, and the prescribed constant according to the image format is “8”. ”, The encryption unit 121 uses the getBlockLengthCenter function to determine the vertical size of the block that is not located at the top or bottom of the original image (and the horizontal size of the block that is not located at the right or left end of the original image). Size) value “32” is derived. Furthermore, the encryption unit 121 can derive the value “32” of the horizontal size of the leftmost block of the original image (and the vertical size of the uppermost block of the original image) using the getFirstFractionLength function. From these values, the upper left coordinate values and the vertical and horizontal sizes of all blocks in the original image are determined.

  Note that the encryption unit 121 may perform the division process so that the vertical and horizontal sizes of all blocks that are not located at the lower end or the right end of the original image are always the same. It is more desirable to perform division processing using the function shown. This is because, in the former division processing, the sufficiently obfuscated area is biased to the upper left of the obfuscated image depending on the size of the original image.

  With reference to FIG. 5 (a diagram showing an obfuscated image in the case where the number of divisions in the vertical and horizontal directions is 8 and the prescribed constant according to the format of the original image is 16, this point is a little more concrete. I will explain it.

  FIG. 5A shows an obfuscated image obtained by replacing each block defined by the former division processing with another block from the original image of 224 dots vertically and 224 dots horizontally. FIG. 5B shows an obfuscated image obtained by replacing each block defined by the latter division process with another block from the original image of 208 dots vertically and 208 dots horizontally.

  As can be seen from the obfuscated image in FIG. 5A, when the encryption unit 121 performs the former division processing, it is not located at the lower end or the right end of the original image (the upper left quarter of the original image is The total 49 blocks (7 vertical x 7 horizontal) are 16 dots vertically and 16 dots horizontally. Similarly, the size of seven blocks located at the lower end of the original image (which constitutes the lower left quarter of the original image) is 112 dots long and 16 dots wide, and is located at the right end of the original image (the original image The size of the seven blocks (which constitute the upper right quarter) is 16 dots long and 112 dots wide, and the size of the block in the lower right corner of the original image is 112 dots high and 112 dots wide.

  Therefore, the encryption unit 121 cannot sufficiently obfuscate the original image even if the obfuscation process is performed after the former division process (as can be seen from (a) of FIG. 5). The lower right quarter is not obfuscated at all).

  On the other hand, as can be seen from the obfuscated image in FIG. 5B, when the encryption unit 121 performs the latter division processing, the block in the lower right corner having the largest vertical and horizontal block size among all the blocks. Even so, the size is at most 64 dots long and 64 dots wide (the block size in the upper left corner is 48 dots long and 48 dots wide, and the size of the block that is not located at any of the top, bottom, left, or right edges) Is 16 dots vertically and 16 dots horizontally).

  Therefore, when performing the latter division processing, the encryption unit 121 can perform sufficient obfuscation as can be seen from the obfuscated image in FIG. 5B (as can be seen from FIG. 5). The central part of the obfuscated image in FIG. 5B is more obfuscated than the central part of the obfuscated image in FIG.

  After S1, the encryption unit 121 determines whether the original image is an upsampled image (for example, a JPEG image having a sampling ratio of 4: 2: 0) (S2). The encryption unit 121 proceeds to S3 if it determines that “the original image is an upsampled image”, and proceeds to S4 if it determines that “the original image is not an upsampled image”.

  In S3, the encryption unit 121 creates two PNG images (a vertically long bar image and a horizontally long bar image) as shown in FIG. A vertically long bar image combines all boundary pixels at the boundary between two adjacent blocks on the left and right (specifically, the boundary pixel group (boundary image) of each column adjacent to the boundary is horizontally aligned) Are combined images created by combining them side by side. Similarly, a horizontally long bar image combines all boundary pixels at the boundary between two vertically adjacent blocks (specifically, a group of pixels (boundary image) in each row adjacent to the boundary vertically A combined image created by combining side by side in the direction.

  That is, it can be said that “two bar images are data relating to an area composed of boundary pixels (specific pixels) in each of a plurality of blocks obtained by dividing the original image”. In addition, “each part of the image occupying the entire region (a part of the image consisting of boundary pixels arranged in the row direction and a part of the image consisting of boundary pixels arranged in the column direction) is composed of two bar images. It can be said that it is represented by any one of (the prescribed image group).

  After S3, the encryption unit 121 proceeds to S4.

  In S4, the encryption unit 121 creates a block replacement rule at random. The block replacement rule is a rule indicating which block of the original image should replace each block obtained by dividing the original image.

After S4, the encryption unit 121 scrambles the original image (processing to replace all or part of the plurality of blocks obtained by dividing the original image with other blocks in the original image based on the block replacement rule). The obfuscated image is generated (S5: obfuscation step)
The process of S5 will be described more specifically.

  When the original image is an image obtained by discrete cosine transform (for example, a JPEG image converted to the frequency domain as shown in FIG. 7A), the encryption unit 121 calculates the DCT coefficient group of each block. The DCT coefficient group of another corresponding block is replaced. For example, as illustrated in (a) of FIG. 7, the encryption unit 121 converts the DCT coefficient group of each block to the DCT coefficient group of the corresponding other block for a part of the plurality of blocks obtained by dividing the original image. Replace. 7A, the numerical value i given to each block of the obfuscated image is “in the original image, the block corresponding to the block given the numerical value i is at the i-th position in the raster scan order. It is shown that.

  On the other hand, when the original image is not a discrete cosine transformed image, the encryption unit 121 replaces the pixel value group of each block with the pixel value group of another corresponding block. For example, when the original image is a PNG image as shown in FIG. 7B, the encryption unit 121 replaces the pixel value group of each block with the pixel value group of the corresponding other block. An obfuscated image as shown in (b) of FIG. 7 is generated.

  A known tool can be used to replace the blocks in S5.

After S5, the encryption unit 121 (second generation means) uses a decryption key (information including the size of the original image, the number of vertical and horizontal divisions, and the block replacement rule used for the obfuscation process). A decryption key as illustrated in FIG. 8 is created (S6). The “sequence a _i indicating the block replacement rule” in FIG. 8 replaces the i-th block in the raster scan order with the a _i- th block in the raster scan order for each i where “i ≠ a _i ”. Indicates that an obfuscated image has been generated.

  The operation for performing the obfuscation process on the original image has been described above. However, the content conversion server 100 performs the operation on all original images included in the electronic book content. However, the content conversion server 100 does not perform the operation for an original image having a small vertical and horizontal size (an image that cannot be divided into a plurality of blocks).

  The content conversion server 100 also obfuscates the text included in the electronic book content, and generates a decryption key for decrypting the text. This process may be a process based on an arbitrary algorithm (for example, a known algorithm).

  Then, the content conversion server 100 decrypts the encrypted electronic book content (the electronic book content in which each original image and text are obfuscated), the decryption key group for decrypting all the original images, and the text. The data 5 including the decryption key to be transmitted is transmitted to the book sales server 200.

(Operation of tablet terminal 300)
Next, the operation of the tablet terminal 300 will be described with reference to FIGS.

  FIG. 9 is a flowchart illustrating an operation of restoring an original image without causing deterioration from an obfuscated image and displaying the restored image. FIG. 10 is a diagram for explaining a method in which the tablet terminal 300 restores an original image without causing deterioration from an obfuscated image. FIG. 11 is a diagram for explaining the boundary pixels of each block of the up-obfuscated obfuscated image. FIG. 12 is a diagram for explaining how the tablet terminal 300 displays an image included in the electronic book content.

  Before the tablet terminal 300 performs the operation according to the flowchart of FIG. 9, the download processing unit 321 accepts an operation for browsing the purchased electronic book content and downloads the bibliographic information of the user of the tablet terminal 300. Shall be. Then, based on the bibliographic information, the download processing unit 321 identifies the page that the user last viewed in the electronic book content, and adds the obfuscated image, the obfuscated text, and the obfuscated image of the identified page. It is assumed that the decryption key used for performing the decryption process and the decryption key for decrypting the original text from the obfuscated text are downloaded.

  In S11, the decryption unit 322 reads the downloaded obfuscated image and the decryption key from the storage unit 310, and performs the decryption process on the obfuscated image using the decryption key.

  The process of S11 will be described more specifically.

  First, the decryption unit 322 identifies the position and size of each block in the obfuscated image by referring to the decryption key. For example, referring to the vertical and horizontal sizes of the obfuscated image and the decoding key shown in FIG. 8, the decoding unit 322 recognizes that the vertical and horizontal sizes of each block are 32 dots. Further, the upper left coordinate of each block is recognized.

  When the downloaded obfuscated image is an image obtained by performing discrete cosine transform (for example, a JPEG image), the decoding unit 322 performs inverse discrete cosine transform on the obfuscated image. Then, the decoded image is obtained by performing decoding processing based on the block replacement rule (processing for replacing the pixel value group of each block with the pixel value group of the corresponding original block) on the obfuscated image after the inverse discrete cosine transform. Is generated.

  On the other hand, if the downloaded obfuscated image is not a discrete cosine transformed image, a decoded image is generated by performing the same decoding process on the obfuscated image.

  When the original image is an upsampled image, the generated decoded image may include grid noise as shown in FIG. When the original image is an upsampled image, as can be seen from FIGS. 11A and 11B, this is because the color difference value of the boundary pixel of the block of the obfuscated image is obtained by interpolation processing (specifically, This is because it differs from the original color difference value (the color difference value of the corresponding boundary pixel of the corresponding block in the original image) due to the influence of the color difference value of the boundary pixel of the adjacent block. Therefore, when the original image is an upsampled image, it can be said that “the decoded image needs to be corrected in order to restore the original image without causing deterioration from the obfuscated image”.

  After S11, the decoding unit 322 determines whether there are two bar images corresponding to the obfuscated image. When it is determined that “two bar images corresponding to the obfuscated image exist”, the decoding unit 322 proceeds to S13, and when it is determined that “two bar images corresponding to the obfuscated image do not exist”. Advances to S14.

In S13, the decoding unit 322 corrects the decoded image using the two bar images. That is, a vertically long bar image is divided into H _d −1 (H _d : number of blocks in the horizontal direction) boundary images (images composed of boundary pixel groups belonging to the same column), and each boundary image is associated with a decoded image. Overlay each area you want. Similarly, a horizontally long bar image is divided into V _d −1 (V _d : number of blocks in the vertical direction) boundary images (images consisting of boundary pixel groups belonging to the same row), and each boundary image is decoded. Overlay each corresponding area. By the process of S13, in the area where the boundary image in the decoded image is superimposed, an image occupying the entire corresponding area (specific area) in the original image is restored.

  In S14, the book display processing unit 323 displays the image restored by the decoding unit 322 through the most recent process in an area for displaying the image. If the vertical and / or horizontal size of the area is different from the vertical and / or horizontal size of the image, the restored image is resized to the same size as the area as shown in FIG. And display it in the area.

  As described above, the operation of restoring the original image without causing deterioration from the obfuscated image and displaying the restored image has been described. However, the tablet terminal 300 is configured to display all the obfuscated images included in the display target page. Perform this operation.

  The tablet terminal 300 also performs a decryption process using the decryption key on the text included in the display target page, and displays the text together with the original image.

  Each time the display target page is changed, the tablet terminal 300 displays the display target page as described above.

  When the touch panel display unit 340 accepts an operation to end the reproduction of the electronic book content, the bibliographic information upload processing unit 324 displays bibliographic information (information indicating a page displayed at the time when the operation is performed (bookmark). Information)) is uploaded to the book sales server 200.

(Advantages of content conversion server 100)
The following can be said from the above description.

  That is, the encryption unit 121 (reading unit, obfuscation unit) of the content conversion server 100 reads an image that has been subjected to processing (for example, discrete cosine transform) for conversion to a frequency component, The obfuscation process is performed on the image itself without performing the “conversion process (for example, inverse discrete cosine transform)”.

  The encryption unit 121 (obfuscation means) is configured to scramble the image by replacing all or some of the plurality of blocks obtained by dividing the image with other blocks in the image. .

  According to the above configuration, the obfuscated image generated by the content conversion server 100 is generated due to noise (specifically, processing for converting to a frequency component (for example, discrete cosine transform) due to conventional technology. Noise that is not in the original image). Therefore, it can be said that the content conversion server 100 can obfuscate the image so that little or no degradation in image quality is visually recognized after restoration.

(Appendix 1)
In the prior art shown in FIG. 17, a difference occurs between the original image and the decoded image obtained by performing the decoding process on the obfuscated image (that is, the decoded image has a grid-like shape that is not found in the original image). Noise). This disadvantage is due to the interpolation processing when the upsampled original image is obfuscated by the scramble processing and / or obfuscation generated from the original image (upsampled image or non-upsampled image). This is due to the decoding processing algorithm applied to the image.

  The encryption unit 121 has a region (a lattice noise due to interpolation processing) composed of specific pixels (pixels adjacent to the boundary between two adjacent blocks) in each of a plurality of blocks obtained by dividing an image. Data for a certain area).

  Specifically, the encryption unit 121 generates, from the original image (the image before the obfuscation process), two bar images representing each part of the image that occupies the entire area as the data. As described above, the two bar images can be used to restore the original image.

  Therefore, it can also be said that “the content conversion server 100 is a data generation device that generates data that can be used to restore an image so that grid noise is not visually recognized after restoration”.

(Appendix 2)
As described in the first embodiment, the decoding unit 322 of the tablet terminal 300 is a decoding unit that performs a decoding process on the obfuscated image. Specifically, the decoding unit 322 performs descrambling processing on the obfuscated image by replacing all or part of the plurality of blocks obtained by dividing the obfuscated image with other blocks in the obfuscated image. It has come to give.

  In addition, the decoding unit 322 is an area composed of specific pixels (pixels adjacent to the boundary between two adjacent blocks) in each of a plurality of blocks constituting the entire decoded image obtained by the decoding process (descrambling process). Using the data relating to (a region in which lattice-like noise may be generated due to interpolation processing), correction for eliminating noise in the region is performed on the decoded image.

  Therefore, it can be said that “the tablet terminal 300 is an image restoration device that restores an image so that grid-like noise is not visually recognized after restoration”.

(Appendix 3)
In order to perform the descrambling process on the obfuscated image (replace all or part of the plurality of blocks obtained by dividing the obfuscated image with other blocks in the obfuscated image), the position of each block in the original image And information to identify the size is needed.

  As such information, information indicating the position and size of each block itself can be considered. However, there is a problem that as the number of blocks constituting the original image increases, the information amount of the information increases greatly.

  As described in the first exemplary embodiment, the encryption unit 121 of the content conversion server 100 is also a generation unit that generates decryption information (decryption key) used for decrypting an obfuscated image.

  The decoding information includes information indicating the number of divisions in the vertical and horizontal directions of the image in addition to the information indicating the replacement rule. Information indicating the position and size of each block itself is included in the decoding information. Not included.

  Therefore, “the content conversion server 100 generates information that is used to perform a decoding process (descrambling process) on an obfuscated image so that the amount of information does not increase so much as the number of blocks increases. It can also be said to be an “apparatus”.

(Appendix 4)
It can be said that the decoding unit 322 of the tablet terminal 300 is a generation unit that generates a decoded image having the same size as the obfuscated image from the obfuscated image. The decoding unit 322 is a resizing unit that resizes the decoded image so that the size of the display area is the same as the size of the display area when the size of the display area of the decoded image is different from the size of the decoded image. I can say that. Furthermore, it can be said that the book display processing unit 323 of the tablet terminal 300 according to the first embodiment is a display processing unit that displays the resized decoded image.

  However, the present invention is not limited to the configuration of the tablet terminal 300. That is, when the size of the display area of the decoded image is different from the size of the decoded image, the terminal for browsing the electronic book content is the same size as the display area as shown in FIG. You may perform the decoding process accompanied by the resizing of an obfuscated image which becomes like this. However, as shown in FIG. 12B, in the decoded image obtained in such a manner, lattice-like noise due to the interpolation processing at the time of resizing may appear. Therefore, the decoding process accompanied by the resizing of the obfuscated image is not desirable.

  It can be said that, unlike an apparatus that performs a decoding process accompanied by resizing an obfuscated image, “tablet terminal 300 is an image decoding apparatus that decodes an image so that lattice-like noise is not visually recognized after decoding”.

(Appendix 5)
In the first embodiment, pixel values of pixels at the corners of the block (upper right corner, upper left corner, lower right corner, and / or lower left corner) are included in both the horizontally long bar image and the vertically long bar image. The pixel value of the pixel at the corner of the block may be included in only one of the horizontally long bar image and the vertically long bar image.

(Appendix 6)
In the illustrated example, the content conversion server 100 replaces some of the plurality of blocks obtained by dividing the original image with other blocks in the original image. Of course, the content conversion server 100 may replace all of a plurality of blocks obtained by dividing the original image with other blocks in the original image.

<Embodiment 2>
Hereinafter, a system according to another embodiment of the present invention will be described with reference to FIGS. 13 and 14. FIG. 13 is a diagram for explaining a method in which the content conversion server according to the present embodiment creates a prescribed image (an image used for restoring an original image from an obfuscated image) from the original image. FIG. 14 is a diagram for explaining a method in which the tablet terminal according to the present embodiment restores an original image without causing deterioration from an obfuscated image. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is basically omitted.

(Outline of the system according to this embodiment)
The system according to the present embodiment is similar to the system according to the first embodiment, but differs in the following points.

  That is, the content conversion server 100 according to the present embodiment is not a two-bar image showing each part of an image that occupies the entire area composed of boundary pixels of each block of the original image as the prescribed image, but a transmission showing the image. An image is configured to generate a transmission image in which only pixels constituting the image are non-transmission.

  In addition, the tablet terminal 300 according to the present embodiment corrects a decoded image in which lattice-like noise appears using this transmitted image instead of two bar images.

(System configuration according to this embodiment)
Since the system according to the present embodiment is configured similarly to the system according to the first embodiment, a specific description of the configuration of the system according to the present embodiment is omitted.

(Operation of Content Conversion Server 100)
The content conversion server 100 performs an operation according to a flowchart obtained by replacing “S3” in the flowchart of FIG. 2 with an “alternative process” described below.

  That is, the encryption unit 121 of the content conversion server 100 generates a transparent image having the same size as the original image from the original image in the alternative process. This transparent image is a transparent image as illustrated in FIG. 13 (that is, the α value of the pixels constituting the image is 1 and the α value of the pixels not constituting the image is 0). Transmission image). That is, it can be said that “this transparent image is data relating to an area composed of boundary pixels (specific pixels) in each of a plurality of blocks obtained by dividing the original image”.

(Operation of tablet terminal 300)
The tablet terminal 300 performs an operation according to a flowchart obtained by replacing “S13” in the flowchart of FIG. 9 with an “alternative process” described below.

  That is, in the alternative process, the decoding unit 322 of the tablet terminal 300 corrects the decoded image in which lattice-like noise appears using the transmission image. Specifically, as illustrated in FIG. 14, the decoding unit 322 performs alpha blending processing after setting the foreground image and the background image as a transparent image and a decoded image, respectively.

(Advantages of tablet terminal 300)
As described above, the decoding unit 322 of the tablet terminal 300 is a decoding unit that performs a decoding process on an obfuscated image.

  The decoding unit 322 is also a correction unit that performs a correction process on the decoded image obtained by the decoding process. Specifically, the decoding unit 322 converts a predetermined image (an image in which no lattice noise appears) into the region where the lattice noise appears in the decoded image (that is, “in the original image”). It overlaps with “area in the decoded image” corresponding to “area consisting of boundary pixels of each block”.

  As a result, grid-like noise is not visually recognized in the corrected decoded image. Therefore, the tablet terminal 300 according to the present embodiment can also restore the image so that the lattice noise is not visually recognized after the restoration.

<Embodiment 3>
Hereinafter, a system according to still another embodiment of the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 is a diagram for explaining a method in which the content conversion server according to the present embodiment creates prescribed data (data used to restore an original image from an obfuscated image) from the original image. FIG. 16 is a diagram for explaining a method in which the tablet terminal according to the present embodiment restores an original image without causing deterioration from an obfuscated image. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is basically omitted.

(Outline of the system according to this embodiment)
The system according to the present embodiment is similar to the systems according to the first and second embodiments, but differs in the following points.

  That is, the content conversion server 100 according to the present embodiment uses, as the specified data, data related to an area composed of boundary pixels in each of the plurality of blocks (specifically, text data or binary data that is not an image). Is different from the content conversion server according to the first and second embodiments that generate an image as the prescribed data.

  In addition, the tablet terminal 300 according to the present embodiment corrects a decoded image in which lattice-like noise appears using this data, not an image.

(System configuration according to this embodiment)
Since the system according to the present embodiment is configured similarly to the systems according to the first and second embodiments, a specific description of the configuration of the system according to the present embodiment is omitted.

(Operation of Content Conversion Server 100)
The content conversion server 100 replaces “S3” in the flowchart of FIG. 2 with “alternative process” described below, and further adds an “addition process” described below immediately after “S5” or “S6”. The operation according to the flowchart obtained by the above is performed.

  That is, the encryption unit 121 of the content conversion server 100 temporarily stores the pixel values of all the boundary pixels of the block in the storage unit 110 for each block of the original image in the alternative process.

  Moreover, the encryption part 121 temporarily preserve | saves the pixel value of all the boundary pixels of the said block in the memory | storage part 110 about each block of an obfuscated image in an additional process. Then, in the additional step, as illustrated in FIG. 15, the encryption unit 121, for each boundary pixel of the original image, the pixel value of the boundary pixel and the pixel of “boundary pixel of the obfuscated image” corresponding to the boundary pixel. The difference value from the value is calculated. Here, the “obfuscated image boundary pixel” corresponding to the “original image boundary pixel” refers to the “obfuscated image block” corresponding to the block to which the “original image boundary pixel” belongs in the raster scan order. i (i: a value indicating what position the “boundary pixel of the original image” is in the raster scan order in the block to which the “boundary pixel of the original image” belongs) .

  Further, the encryption unit 121 generates data (difference value data) indicating the difference value for each boundary pixel of the obfuscated image in the additional step. The difference value data may be text format data, but is preferably binary format data. This is because the difference value data in binary format can be easily reduced in data size compared to the difference value data in text format.

(Operation of tablet terminal 300)
The tablet terminal 300 performs an operation according to a flowchart obtained by replacing “S13” in the flowchart of FIG. 9 with an “alternative process” described below.

  That is, in the alternative process, the decoding unit 322 of the tablet terminal 300 corrects a decoded image in which lattice noise appears, using the difference value data, as illustrated in FIG. Specifically, the decoding unit 322 performs, for each pixel in an area occupied by grid noise (an area composed of pixels having the same coordinate value as the “boundary pixel of the original image”), The pixel value is corrected using the difference value calculated for the “original image boundary pixel” having the same coordinate value as the pixel. As a result, the pixel value of each pixel in the region of the decoded image is the same as the pixel value of the corresponding “original image boundary pixel”.

(Advantages of tablet terminal 300)
As described above, the decoding unit 322 of the tablet terminal 300 is a decoding unit that performs a decoding process on an obfuscated image.

  The decoding unit 322 is also a correction unit that performs a correction process on the decoded image obtained by the decoding process. Specifically, the decoding unit 322 uses the above-described difference value data to correspond to a region where lattice noise appears in the decoded image (that is, “region consisting of boundary pixels of each block in the original image”). Each pixel value of “region in decoded image”) is corrected.

  As a result, grid-like noise is not visually recognized in the corrected decoded image. Therefore, the tablet terminal 300 according to the present embodiment can also restore the image so that the lattice noise is not visually recognized after the restoration.

(Appendix 7)
The device for browsing the electronic book content is not limited to the tablet terminal 300, but may be another type of device (personal computer, feature phone, smartphone, electronic book terminal, etc.) having the same characteristics as the tablet terminal 300. May be.

  In the first to third embodiments, two servers are used. However, one server having both the function of the content conversion server 100 and the function of the book sales server 200 may be used, or three or more servers. It may be used.

  Further, instead of the content conversion server 100, a terminal that is not a server may be caused to perform the same processing as the content conversion server 100. In this case, the terminal operator uses the removable recording medium to transmit the data (encrypted electronic book content, decryption key, etc.) transmitted from the content conversion server 100 according to the first to third embodiments to the book sales server 200. It may be moved manually from the terminal to the book sales server 200. Alternatively, when the terminal and the book sales server 200 are connected to each other via a network, the content conversion server 100 can generate the generated data manually (that is, triggered by an operator's operation) or automatically (for example, The data may be uploaded to the book sales server 200 (triggered by the completion of generation of the data).

(Appendix 8)
In the first embodiment, the encryption unit 121 generates a vertically long bar image by combining all boundary pixels adjacent to the boundary between two blocks adjacent on the left and right, and between the two blocks adjacent vertically A horizontally long bar image is generated by combining all boundary pixels adjacent to the boundary.

  However, the bar image generated by the encryption unit 121 is not limited to that. For example, the encryption unit 121 creates a vertically long bar image by combining all the pixels whose distance from the boundary between two adjacent blocks on the left and right is less than a certain value, and two adjacent blocks vertically A horizontally long bar image may be created by combining all the pixels whose distance from the boundary between them is less than a certain distance.

  In the second embodiment, the encryption unit 121 generates a transparent image from the original image, and the transparent image makes only the boundary pixels in the original image non-transparent (that is, the boundary in the original image). The pixel other than the pixel is made transparent).

  However, the transparent image generated by the encryption unit 121 is not limited to that. For example, the transparent image generated by the encryption unit 121 makes only “a pixel whose distance from the boundary between two adjacent blocks is less than a certain value” in the original image non-transparent (that is, “ It may be obtained by making a “pixel whose distance from a boundary between two adjacent blocks is a certain distance or more” transparent.

(Appendix 9)
The content conversion server 100 is configured to have the following features 1 to 3.
Feature 1: A scramble process is performed on an image that has been subjected to a process of converting to a frequency domain (frequency component) (for example, a discrete cosine transform).
Feature 2: Data for deleting grid noise in the decoded image is generated.
Feature 3: Information indicating the number of blocks in the vertical and horizontal directions is generated as information for specifying the position and size of each block in the obfuscated image.

  The image obfuscation apparatus according to the present invention is not limited to the content conversion server 100, and may be provided with at least one of the above-described features 1 to 3.

  Note that an image obfuscation apparatus that does not include the feature 1 may perform scramble processing on an image that has been subjected to processing for conversion into a spatial region (pixel component) (for example, inverse discrete cosine transform). In addition, the image obfuscation apparatus that does not include the feature 3 sets the vertical and horizontal division numbers to predetermined fixed values, or the vertical and horizontal division numbers according to the vertical and horizontal sizes of the image. Should be determined.

The tablet terminal 300 is configured to have the following features 4 to 6.
Feature 4: A decoded image having the same size as the obfuscated image is generated.
Feature 5: Using the data generated by the image obfuscation device, the grid noise in the decoded image is eliminated.
Feature 6: The position and size of each block in the obfuscated image are specified by referring to information indicating the number of blocks in the vertical and horizontal directions of the obfuscated image.

  The image restoration apparatus (image decoding apparatus) according to the present invention is not limited to the tablet terminal 300, and may be provided with at least one of the above feature 4 to feature 6.

  Note that the image obfuscation apparatus that does not include the feature 4 only needs to be configured to generate a decoded image from the obfuscated image. In addition, the image obfuscation apparatus that does not include the feature 6 sets the vertical and horizontal division numbers to predetermined fixed values, or the vertical and horizontal division numbers according to the vertical and horizontal sizes of the image. As long as the position and size of each block in the obfuscated image are specified.

(Appendix 10)
In the first to third embodiments, the content conversion server 100 is configured to delete data (for example, in the first embodiment, 2 in the first embodiment) only when the original image is an upsampled image. Two bar images). The reason is that, as described above, when the original image is an upsampled image, lattice-like noise may appear in the decoded image.

  In this regard, even when the original image is not an upsampled image, lattice-like noise may appear depending on the decoding algorithm.

  In view of this point, regardless of whether or not the original image is an upsampled image, data for eliminating grid noise in the decoded image (for example, one transmission image in the second embodiment) The content conversion server 100 may be configured to generate. Similarly, regardless of whether or not the original image is an upsampled image, the data (for example, difference value data in the third embodiment) is used to decode the correction for eliminating the lattice noise. You may comprise the tablet terminal 300 so that it may apply to an image.

(Appendix 11)
As described above, in the first to third embodiments, the decryption key (data 5) includes information indicating the block replacement rule, the vertical division number, and the horizontal division number. However, the information referred to perform the decryption process on the obfuscated image is not limited to such a decryption key (data 5). That is, the information is not information indicating both the number of divisions in the vertical direction and the number of divisions in the horizontal direction, but information indicating either the number of divisions in the vertical direction or the number of divisions in the horizontal direction is stored. It may come to be.

  In this case, the tablet terminal 300 specifies the total number of blocks from the sequence indicating the block replacement rule, and uses one of the information indicating either the number of divisions in the vertical direction or the number of divisions in the horizontal direction ( For example, the number of vertical divisions) is specified. Then, the other (for example, the number of divisions in the horizontal direction) is specified by dividing the total number of blocks by the specified number of divisions.

(Program etc.)
The control blocks (particularly, the encryption unit 121, the decryption unit 322, and the book display processing unit 323) of each device according to the first to third embodiments are realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like. Alternatively, it may be realized by software using a CPU (Central Processing Unit).

  In the latter case, each device includes a CPU that executes instructions of a program that is software that implements each function, a ROM (Read Only Memory) or a storage in which the above-described program and various data are recorded so as to be readable by a computer (or CPU). An apparatus (these are referred to as “recording media”), a RAM (Random Access Memory) for expanding the program, and the like are provided. And the objective of this invention is achieved when a computer (or CPU) reads the said program from the said recording medium and runs it. As the recording medium, a “non-temporary tangible medium” such as a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. The program may be supplied to the computer via an arbitrary transmission medium (such as a communication network or a broadcast wave) that can transmit the program. The present invention can also be realized in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

[Summary]
The image obfuscation apparatus according to the first aspect of the present invention includes a reading unit (encrypting unit 121) that reads an image (JPEG image) that has been subjected to processing (discrete cosine transform) for conversion to a frequency component, and obfuscation of the image. Obfuscation means (encrypting unit 121) that performs processing, and the obfuscation means replaces all or some of the plurality of blocks obtained by dividing the image with other blocks in the image, thereby The image is subjected to the obfuscation process (scramble process).

  According to the above configuration, the image subjected to the obfuscation process by the image obfuscation apparatus according to aspect 1 includes noise (noise not found in the image read by the reading unit) due to the prior art. I can't. Therefore, it can be said that the image obfuscation apparatus according to aspect 1 can obfuscate the image so that little or no degradation in image quality is visually recognized after restoration.

  The image obfuscation device according to aspect 2 of the present invention further includes generation means (encryption unit 121) for generating data related to a specific area in the image (original image) in the aspect 1, and the specific identification The region is a region composed of specific pixels in each of the plurality of blocks, the specific pixel is a pixel adjacent to the boundary between two adjacent blocks, and the data includes the entire specific region. It may be data for restoring an occupied image. The data related to the specific area may be data including only information related to the area, or the information related to the area and the peripheral area of the area (for example, the distance from the nearest boundary pixel is not more than a certain value). Such information may be data including information on “regions including“ pixels that are not boundary pixels ”.

  When the decoding process is performed on the image (obfuscated image) output by the obfuscation process, a region in the decoded image corresponding to the specific region has a lattice resulting from the generation of the upsampled obfuscated image. Noise may be visible.

  According to the above configuration, the image obfuscation apparatus according to the aspect 2 includes the original image from the obfuscated image, even when the image to be obfuscated is an upsampled image. There is a further effect that it is possible to restore the noise so that it is not visually recognized.

  The image obfuscation apparatus according to aspect 3 of the present invention is the image obfuscation apparatus according to aspect 2, in which the generation unit is a specified image representing the image as the data from the image, or any part of the image. A defined group of images as represented by may be generated.

  According to the above configuration, the image obfuscation apparatus according to the aspect 3 described above is as follows: “The decoding process is performed on the obfuscated image, and the specified image (or the specified image group) is superimposed on the obtained decoded image. This makes it possible to restore the original image from the obfuscated image so that the noise is not visually recognized.

  The image obfuscation device according to aspect 4 of the present invention is the image obfuscation apparatus according to aspect 2, in which the generation unit has a pixel value of the specific pixel that is positioned i-th in the block in the raster scan order for each block of the image. And data indicating the difference between the pixel value of the specific pixel located i-th in the raster scan order in the block corresponding to the block in the image output by the obfuscation process. Good.

  According to said structure, the image obfuscation apparatus which concerns on the said aspect 4 data of the said data produced | generated in order to enable it to "restore the original image so that the said noise is not visually recognized from an obfuscated image" There is a further effect that the amount can be reduced.

  The image obfuscation apparatus according to aspect 5 of the present invention is the image obfuscation apparatus that generates decoding information (data 5) used for decoding the image read by the reading means in any of the aspects 1 to 4. 2 generating means (encrypting unit 121), and the decryption information includes information indicating the vertical and horizontal division numbers of the image in addition to the information indicating the replacement rule. Also good.

  According to the above configuration, even when the number of blocks is large, the information amount of the decoding information is not so large.

  Therefore, the image obfuscation apparatus according to aspect 5 has the further effect that the information amount of the decoding information can be reduced.

  An image obfuscation method according to an aspect 6 of the present invention is an image obfuscation method executed by an apparatus, and includes a reading step of reading an image that has been subjected to processing for conversion to a frequency component, and subjecting the image to obfuscation processing. An obfuscation step, and in the obfuscation step, the image is subjected to the obfuscation process by replacing all or part of a plurality of blocks obtained by dividing the image with other blocks in the image. May be.

  According to said structure, the image obfuscation method which concerns on the said aspect 6 has an effect similar to the image obfuscation apparatus which concerns on the said aspect 1. FIG.

  The image obfuscation apparatus according to the first to fifth aspects of the present invention may be realized by a computer. In this case, the computer is operated as each unit included in the image obfuscation apparatus so that the above-described units are set in the computer. The program to be realized and the computer-readable recording medium on which the program is recorded also fall within the scope of the present invention.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention. Furthermore, a new technical feature can be formed by combining the technical means disclosed in each embodiment.

  The present invention can be suitably used in fields related to electronic books.

100 content conversion server (image obfuscation device)
110 storage unit 120 control unit 121 encryption unit (reading unit, obfuscation unit, generation unit, second generation unit)
200 Book Sales Server 300 Tablet Terminal (Image Decoding Device, Image Restoration Device)
310 Storage Unit 320 Control Unit 321 Download Processing Unit 322 Decoding Unit 323 Book Display Processing Unit 324 Book Information Upload Processing Unit

Claims (6)

Reading means for reading an image subjected to processing for conversion to a frequency component;
Obfuscation means for obfuscating the image;
Generating means for generating data relating to a specific region in the image ,
The obfuscation means, all or part of the plurality of blocks obtained by dividing the image by replacing the other blocks in the image, which is configured to perform the obfuscation process on the image,
The specific area is an area composed of specific pixels in each of the plurality of blocks,
The specific pixel is a pixel adjacent to a boundary between two adjacent blocks,
The data is data for restoring an image occupying the entire specific area,
For each block of the image, the generation unit corresponds to the block of the pixel value of the specific pixel located i-th in the raster scan order in the block and the image output by the obfuscation process. In the block, data indicating a difference between the pixel value of the specific pixel located i-th in the raster scan order is generated.
An image obfuscation apparatus characterized by the above. The generating means generates, as the data, a defined image representing the image or a defined image group in which each part of the image is represented by any image as the data. The image obfuscation apparatus according to claim 1 . A second generating means for generating decoding information used for decoding the image read by the reading means;
To the decoding information in addition to information indicating a rule in replacement, according to claim 1 or 2, longitudinal and information indicating the number of divisions in the lateral direction is included, wherein the of the image Image obfuscation device. An image obfuscation method performed by an apparatus,
A reading step in which the device reads an image that has been processed to be converted into a frequency component;
An obfuscation step in which the apparatus performs obfuscation processing on the image;
Generating data relating to a specific region in the image ,
The apparatus at the obfuscation step, all or part of the plurality of blocks obtained by dividing the image by replacing the other blocks in the image, and facilities the obfuscation process on the image,
The specific area is an area composed of specific pixels in each of the plurality of blocks,
The specific pixel is a pixel adjacent to a boundary between two adjacent blocks,
The data is data for restoring an image occupying the entire specific area,
In the generation step, for each block of the image, the pixel value of the specific pixel located i-th in the raster scan order in the block and the block in the image output by the obfuscation process In the block, data indicating a difference between the pixel value of the specific pixel located i-th in the raster scan order is generated.
An image obfuscation method characterized by the above. The program for functioning a computer as said each means with which the image obfuscation apparatus of any one of Claim 1 to 3 is provided. A computer-readable recording medium on which the program according to claim 5 is recorded.

Images