JP4407342B2 - Imaging apparatus, digital watermark detection program, and digital watermark embedding method - Google Patents

Description

  The present invention relates to an imaging apparatus, a digital watermark detection program, and a digital watermark embedding method.

  2. Description of the Related Art Conventionally, a technique for embedding copyright information or the like as “digital watermark” in image data for the purpose of copyright protection is known (for example, see Non-Patent Document 1). As a method for embedding a digital watermark, several methods have been proposed depending on the target image such as a binary image, a monochrome grayscale image, a color image, or a moving image, and each method is used according to the application. However, an effective embedding method has not been proposed for image data before being subjected to image processing.

  This is because, for example, even if digital watermark information is embedded in image data before image processing in a camera and recorded on a memory card, it is embedded when image processing necessary for reproduction as an image is performed on the image data. Because the information is greatly damaged. In this specification, image processing (color interpolation or the like) necessary for reproducing an image is hereinafter referred to as “development processing”.

  In Patent Document 1, digital watermark information and a flag for instructing embedding of a digital watermark are added to RAW data before development processing, and an attempt is made to protect copyright on the RAW data before development processing. Note that the RAW data before development processing in Patent Document 1 is generated in a shooting recording mode (CCD-RAW mode) in a signal form corresponding to the pixel configuration of the imaging device, and is subjected to image processing. Corresponds to previous image data. Then, the RAW data to which the flag is added is transferred to the computer, and the development process and the digital watermark information embedding process are continuously executed by the computer.

In this specification, the expression “image data” is used to mean color information (for example, pixel value) corresponding to each pixel, and does not include shooting information or the like included in the header of the file. That is, the image file is composed of “image data” and information recorded in a header or the like. When digital watermark information is embedded as each pixel value, the information represented by the pixel value may be slightly different from the pure color information of the photographed subject. To do. “RAW data” in Patent Document 1 is different from “image data” in this specification if it is interpreted as including a flag.
JP 2003-46758 A Published by Kokoo Matsui “Basics of Digital Watermarking”, Morikita Publishing Co., Ltd., August 21, 1998

  Even if the electronic watermark information and the information for instructing embedding are added to the RAW data as in Patent Document 1, unauthorized use of the RAW data cannot be reliably prevented. This is because if the information is ignored during the development process, the image data subjected to the development process can be generated without a digital watermark. On the other hand, professional photographers often record image data after shooting in a state before image processing. For this reason, there has been a demand for a method for reliably protecting the copyright even for image data before image processing.

  An object of the present invention is to provide a technique for protecting copyright even for image data before being subjected to image processing.

  The image pickup apparatus according to claim 1 includes an image pickup unit and a direct embedding unit. The imaging unit images a subject and generates image data including color information of a plurality of pixels and color information of one color component for each pixel. The direct embedding unit embeds digital watermark information in the image data according to the image processing parameters before the image processing is performed on the image data.

According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, the “parameter includes a white balance adjustment parameter” .

According to a third aspect of the present invention, in the image pickup apparatus according to the first or second aspect , the image pickup apparatus includes a “detection unit that detects digital watermark information from image data in which the digital watermark information is embedded”.

The invention of claim 4 is a digital watermark detection program for causing a computer to execute the following steps. One is a step of acquiring image data in which digital watermark information is embedded by the imaging apparatus according to any one of claims 1 to 3 . One is a step of detecting digital watermark information from the acquired image data.
The digital watermark embedding method according to claim 5 is: “image data having color information of a plurality of pixels and color information of one color component in one pixel and not subjected to image processing; The digital watermark information is embedded in accordance with processing parameters ”.

The invention of claim 6 is the digital watermark embedding method according to claim 5 , characterized in that “the parameter includes a parameter for white balance adjustment” .

  In one embodiment of the present invention, digital watermark information is embedded in image data before image processing in accordance with image processing parameters. In another embodiment of the present invention, the digital watermark information is embedded after the white balance adjustment processing is performed on the image data before the image processing. Therefore, even if necessary image processing such as color interpolation is performed on the image data after embedding, the degree of damage of the embedded information is reduced as compared with the conventional case. Furthermore, image quality deterioration due to embedding digital watermark information can be reduced. As a result, it is possible to protect the copyright of the image data before image processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Configuration of this embodiment>
FIG. 1 is a diagram illustrating the principle of this embodiment. In the present embodiment, first, image data is generated by photographing with the electronic camera 2 ([1] in FIG. 1). Next, the digital watermark information is embedded in the image data generated by the imaging unit 4 immediately after A / D conversion without performing any image processing, or only after white balance adjustment processing is performed. The watermark information is embedded ([2] in FIG. 1). The image data after embedding is recorded in the memory card 10 without being subjected to image processing ([3] in FIG. 1) and then acquired by the image processing computer 8 ([4] in FIG. 1). Hereinafter, an example of a configuration for realizing this will be described in detail.

The image processing computer 8, the digital watermark detection program P (not Figure shown) installed. The electronic watermark detection program P corresponds to the electronic camera 2 and detects (decodes) the electronic watermark information embedded by the electronic camera 2.
FIG. 2 is a block diagram showing details of the electronic camera 2. As shown in the figure, the electronic camera 2 includes a photographing lens 12, a focal plane shutter 16, an image sensor 20, an analog signal processing unit 24, an A / D conversion unit 28, a timing generator 32, and a color measurement unit. 36, an MPU (Micro Processor Unit) 40, an operation unit 44, a system bus 48, an image processing unit 52, an image memory 56, a program memory (EEPROM) 60, a card interface 64, and a replaceable memory. The card (recording medium) 10, a USB (Universal Serial Bus) 72, a USB interface 76, a monitor control unit 80, and a liquid crystal monitor 84 are configured.

The analog signal processing unit 24 and the A / D conversion unit 28 perform a clamp process, a sensitivity correction process, an A / D conversion, and the like on the analog pixel signal output from the image sensor 20 to generate digital image data. . Since the pixel signal is analog before the A / D conversion, it is not in the data state. Therefore, the processing performed before the A / D conversion is different from the image processing.
The operation unit 44 includes a group of buttons such as a power button, a shooting condition input button, a release button, a recording mode selection button, and a digital watermark information input button, and a digital watermark information detection instruction button (not shown). (Illustrated).

The MPU 40 performs system control of the electronic camera 2. The MPU 40 is installed with the digital watermark detection program P and a digital watermark embedding program (corresponding to steps S5 to S10 and steps S11 to S17 described later).
The electronic camera 2 is an example of an imaging apparatus described in the claims. 1 corresponds to the functions of the photographing lens 12, the focal plane shutter 16, the image sensor 20, the analog signal processing unit 24, the A / D conversion unit 28, the timing generator 32, and the MPU 40 that controls the photographing operation. To do. The “operation for capturing an image of a subject and generating image data” by the imaging unit is well known, and thus the description thereof is omitted.

<Description of operation of this embodiment>
3, 4 and 5 are flowcharts showing the operation of the present embodiment. 3 mainly shows the processing contents in the digital watermark first mode, FIG. 4 mainly shows the processing contents in the digital watermark second mode, and FIG. 5 shows the processing contents in the image processing computer 8. Mainly shows. The operation of this embodiment will be described below according to the step numbers shown in the figure.

  [Step S1] Image data is generated by a known photographing operation and output from the A / D converter 28. The image data immediately after A / D conversion output here has a pixel value of one color component for one pixel, and no image processing is performed. In the present embodiment, as an example, the image sensor 20 has a primary color Bayer array, and each pixel value is one of a red pixel signal R, a green pixel signal G, and a blue pixel signal B. In this specification, the following four pieces of image data are defined as “RAW image data”.

  One is the image data immediately after A / D conversion output here. One is one in which digital watermark information is embedded in image data immediately after A / D conversion. One is obtained by performing only white balance adjustment processing on image data immediately after A / D conversion. One is obtained by performing white balance adjustment processing and embedding digital watermark information on image data immediately after A / D conversion. Therefore, in this specification, image data that has been subjected to white balance adjustment processing and other image processing excluding embedding of digital watermark information is not referred to as “RAW image image data”.

  At the time of shooting in step S1, the MPU 40 determines the white balance gains Wr, Wg, and Wb based on the color temperature of the shooting light source detected by the color measurement unit 36. As an example of the white balance adjustment processing in the present embodiment, the white pixel gains Wr, Wg, and Wb are multiplied by the red pixel signal R, the green pixel signal G, and the blue pixel signal B, respectively.

  The white balance gains Wr, Wg, and Wb are adjusted so that the signal levels of the red pixel signal R, the green pixel signal G, and the blue pixel signal B when an achromatic color is photographed are output from the image sensor 20. It also includes the sensitivity ratio correction of the pixel signals of the respective color components. If the white balance adjustment conditions are set in advance by the user, the white balance gains Wr, Wg, and Wb are determined using the conditions. Thereafter, the process proceeds to step S2.

[Step S2] The MPU 40 determines whether or not the recording mode of the electronic camera 2 is set to the digital watermark first mode. If set, the process proceeds to step S5, and if not, the process proceeds to step S3.
[Step S3] The MPU 40 determines whether or not the recording mode of the electronic camera 2 is set to the digital watermark second mode. If it is set, the process proceeds to step S11 in FIG. 4, and if not, the process proceeds to step S4.

  [Step S4] When this step is reached, the electronic camera 2 is set to another known recording mode. The image processing unit 52 performs development processing on the image data of the RAW image immediately after A / D conversion in accordance with an instruction from the MPU 40. Thereby, image data in which each pixel has pixel values of three color components of red, blue, and green is generated. In the following description, image data in which each pixel has pixel values of red, blue, and green color components is referred to as RGB image data. Thereafter, the RGB image data is recorded on the memory card 10 via the card interface 64. Thereby, the operation of the electronic camera 2 ends.

  [Step S5] When this step is reached, the electronic camera 2 is set to the first digital watermark mode. The image processing unit 52 embeds digital watermark information by the method of the digital watermark first mode without performing other image processing on the image data of the RAW image immediately after the A / D conversion in accordance with a command from the MPU 40. The embedding method may be any invisible watermark as long as it can be applied to a monochrome grayscale image. The embedding method may be on the image region or the frequency domain type (see, for example, p. 61 of Non-Patent Document 1). ).

  At this time, “image data generated by embedding digital watermark information in the image data of the RAW image by the method of the digital watermark first mode and then performing white balance adjustment processing” and “image of the RAW image” After the white balance adjustment process is performed on the data, the image data is embedded so as to be the same as “image data generated by embedding digital watermark information by a normal method”.

  Specifically, in the image data of the RAW image, the pixel value of a certain pixel Pxr corresponding to the red component is Qr, the pixel value of a certain pixel Pxg corresponding to the green component is Qg, and Let Qb be the pixel value of the pixel Pxb. Further, when digital watermark information is embedded in the RAW image image data without performing any other image processing by a normal method, the pixel value of the pixel Pxr is Qr + Δdr, and the pixel value of the pixel Pxg is Qg + Δdg. And the pixel value of the pixel Pxb is Qb + Δdb.

  In the digital watermark first mode, the pixel value of the pixel Pxb is Qb + (Δdb) so that the pixel value of the pixel Pxr is Qr + (Δdr / Wr) and the pixel value of the pixel Pxg is Qg + (Δdg / Wg). / Wb), the digital watermark information is embedded. For this purpose, for example, the digital watermark information is embedded in the image data of the RAW image by a normal method without performing any other image processing, and the pixel value of the pixel Pxr (that is, Qr + Δdr) is increased. Ask for. Then, by subtracting Qr which is the pixel value before embedding from the pixel value obtained here, Δdr is obtained. If Δdr is obtained, the pixel value of the pixel Pxr can be embedded so as to be Qr + (Δdr / Wr).

  The pixel value of the pixel Pxr is Qr + (Δdr / Wr) immediately after the digital watermark information is embedded by the digital watermark first mode method, and is multiplied by Wr when white balance adjustment processing is performed thereafter. Therefore, (Qr × Wr) + Δdr. This is equivalent to embedding digital watermark information by a normal method after white balance adjustment processing. The same applies to the pixel Pxg and the pixel Pxb. The digital watermark information to be embedded here is set in advance by, for example, user input. Thereafter, the process proceeds to step S6.

[Step S6] The MPU 40 determines whether or not an instruction to detect digital watermark information is given by the digital watermark information detection instruction button. If yes, go to step S7, otherwise go to step S8.
[Step S7] The MPU 40 uses the digital watermark detection program P to detect digital watermark information from the image data of the RAW image after the processing in step S5. The detection method here is a method corresponding to the embedding method used in step S5 and needs to be a method for a monochrome grayscale image. Thereafter, the MPU 40 displays the detected electronic watermark information on the liquid crystal monitor 84. As a result, the user can confirm that the digital watermark information is correctly embedded and the contents of the embedded digital watermark information. Thereafter, the process proceeds to step S8.

  [Step S8] The MPU 40 stores the “RAW image data after processing in Step S5” and the “shooting information at the time of shooting in Step S1” as one file via the card interface 64. To record. A file composed of RAW image data and shooting information like the file recorded here is hereinafter referred to as a “RAW image file”. The shooting information is, for example, shooting time and pixel array information (in this example, information indicating a Bayer array), and is recorded as a file header. Further, the photographing information here always includes the white balance gains Wr, Wg, and Wb determined in step S1. Thereafter, the process proceeds to step S9.

[Steps S9 and S10] The same processes as in steps S6 and S7 are performed. Thereafter, the process proceeds to step S18 in FIG.
[Step S11] When this step is reached, the recording mode of the electronic camera 2 is set to the digital watermark second mode. In the digital watermark second mode, the image processing unit 52 performs white balance adjustment processing on the image data of the RAW image using the white balances Wr, Wg, and Wb determined in step S1 in accordance with an instruction from the MPU 40. Thereafter, the process proceeds to step S12.

[Step S12] The image processing unit 52 embeds the digital watermark information in the image data of the RAW image subjected to the processing in step S11 in accordance with the instruction from the MPU 40. The embedding method here is an invisible watermark as long as it can be applied to a monochrome grayscale image. Thereafter, the process proceeds to step S13.
[Step S13] The MPU 40 determines whether an instruction to detect digital watermark information is given by the digital watermark information detection instruction button. If so, the process proceeds to step S14; otherwise, the process proceeds to step S15.

  [Step S14] The MPU 40 uses the digital watermark detection program P to detect digital watermark information from the image data of the RAW image after the processing in step S12. The detection method here is different from the detection method in step S7 (corresponding to the embedding method used in step S5) in that it corresponds to the embedding method in step S12. Thereafter, the MPU 40 displays the detected electronic watermark information on the liquid crystal monitor 84. Then, the process proceeds to step S15.

  [Step S15] As in step S8, the MPU 40 stores “image data of the RAW image after processing in step S12” and “shooting information at the time of shooting in step S1” in the memory card 10 as a RAW image file. Let me record. However, the white balance gains Wr, Wg, Wb in the photographing information here are not the values used for the processing in step S11, but are all recorded as 1. This is to indicate that the white balance adjustment processing has already been performed on the image data of the RAW image to be recorded. Thereafter, the process proceeds to step S16.

[Steps S16 and S17] The same processing as in steps S13 and S14 is performed. Thereafter, the process proceeds to step S18 in FIG.
[Step S18] The image processing computer 8 obtains a RAW image file recorded in the memory card 10. Then, the process proceeds to step S19.
[Step S19] The image processing computer 8 determines whether or not an instruction to detect digital watermark information is given (for example, by keyboard input). If given, the process proceeds to step S20, and if not, the process proceeds to step S21.

  [Step S20] The image processing computer 8 refers to the header of the RAW image file to determine whether or not the white balance gains Wr, Wg, and Wb are all 1. If all the values are 1, it means that this RAW image file is recorded in the digital watermark second mode, and otherwise, it means that this RAW image file is recorded in the digital watermark first mode. To do.

  Thereafter, the image processing computer 8 uses the digital watermark detection program P to detect digital watermark information from the image data of the RAW image in the acquired RAW image file. At this time, if the white balance gains Wr, Wg, Wb are all 1, they are detected by the same method as in step S14, and if not, they are detected by the same method as in step S7. Thereafter, the image processing computer 8 displays the detected digital watermark information on the screen. Then, the process proceeds to step S21.

[Step S21] The image processing computer 8 refers to the header of the RAW image file and determines whether the white balance gains Wr, Wg, and Wb are all 1. If all are 1 (when recorded in the digital watermark second mode), the process proceeds to step S23; otherwise (when recorded in the digital watermark first mode), the process proceeds to step S22.
[Step S22] The image processing computer 8 performs development processing on the image data of the RAW image in the acquired RAW image file to generate RGB image data. The development processing here includes white balance adjustment processing, color interpolation, color correction, contour enhancement processing, gamma correction, and the like. In this white balance adjustment process, white balance gains Wr, Wg, and Wb recorded in the header of the RAW image file are used. Thereafter, the process proceeds to step S24.

[Step S23] The image processing computer 8 subjects the RAW image data in the acquired RAW image file to development processing excluding white balance adjustment processing to generate RGB image data. Thereafter, the process proceeds to step S24.
[Step S24] The image processing computer 8 determines whether or not an instruction to detect digital watermark information is given. If given, the process proceeds to step S25, and if not, the process proceeds to step S26.

  [Step S25] The image processing computer 8 uses the digital watermark detection program P to detect digital watermark information from the RGB image data generated in step S22 or S23. The detection method here needs to be a method corresponding to the embedding method (steps S5 and S14) used in the electronic camera 2 and a method corresponding to a color image composed of three primary colors. Then, the image processing computer 8 displays the image represented by the RGB image data on the screen together with the detected digital watermark information. Thereafter, the process proceeds to step S27.

[Step S26] The image processing computer 8 displays the image represented by the RGB image data generated in Step S22 or S23 on the screen as it is (without providing digital watermark information). Thereafter, the process proceeds to step S27.
[Step S27] The image processing computer 8 continues the processing in accordance with a user instruction. For example, when an instruction to detect digital watermark information is given, an image represented by RGB image data is displayed on the screen together with the detected digital watermark information. Alternatively, if an instruction to record the generated RGB image data is given, it is recorded. The above is the description of the operation of the present embodiment.

<Effect of this embodiment>
“Data generated by embedding digital watermark information in the method of the digital watermark first mode in the image data of a RAW image immediately after A / D conversion” is subjected to white balance adjustment processing after embedding. This is the same as “image data generated by embedding digital watermark information by a normal method after white balance adjustment processing is first performed on the image data of a RAW image immediately after A / D conversion (step S5). .

  For this reason, even if the white balance adjustment process is performed on the image data of the RAW image recorded on the memory card 10 in the digital watermark first mode, the digital watermark information embedded therein is not damaged at all. Therefore, when the development processing is performed on the image data of the RAW image recorded in the digital watermark first mode, the degree of damage of the embedded information is reduced as compared with the conventional case. In addition, image quality deterioration due to embedding digital watermark information can be reduced.

  In other words, in the digital watermark first mode, the digital watermark information is embedded once in the image data of the RAW image immediately after A / D conversion, and all the image data generated by processing and the like thereafter are performed. Copyright protection is possible. Further, since it is embedded in the image data of the RAW image before image processing, it can be automatically embedded in the camera at the time of shooting. As a result, user convenience is greatly improved. Further, since an invisible electronic watermark for a monochrome grayscale image is compatible with various embedding methods, it is easy to implement.

  In the digital watermark second mode, white balance adjustment processing is first performed on the image data of the RAW image immediately after A / D conversion, and then the digital watermark information is embedded by a normal method. That is, the image data of the RAW image recorded in the digital watermark second mode is different from that recorded in the digital watermark first mode in that white balance adjustment processing has already been performed. The same effect as described above can be obtained. Note that since white balance gains Wr, Wg, and Wb are all recorded as 1 when recording to the memory card 10, the white balance adjustment process is not erroneously performed twice.

<Supplementary items of this embodiment>
[1] It has been described that the white balance gains Wr, Wg, and Wb to be applied are the same for all the pixels of the red, green, or blue component in the image data of the RAW image. The present invention is not limited to such an embodiment. When the gain of each color component applied for color adjustment with respect to the red, green, or blue component pixel in the image data of the RAW image varies depending on the image region, the electronic component is based on the gain corresponding to each image region. Just embed a watermark.

[2] The example in which the RAW image file is acquired by the image processing computer 8 via the memory card 10 has been described. The present invention is not limited to such an embodiment. The RAW image file may be transferred to the image processing computer 8 via the USB 72 without being recorded in the memory card 10.
[3] The example in which the image sensor 20 is the primary color Bayer array has been described. The present invention is not limited to such an embodiment. The present invention is also applicable to, for example, cyan, yellow, and magenta complementary color systems.

  [4] In steps S22 and S23, an example has been described in which the image processing computer 8 continuously performs all image processing necessary for reproducing as an image. The present invention is not limited to such an embodiment. Image processing such as color interpolation and gamma correction may be performed one by one in accordance with user instructions. In this case, each image processing condition may be changed by user input. In this case, if there is a user instruction, the embedded digital watermark information may be detected and displayed after each image processing.

  [5] An example in which image data of a RAW image immediately after A / D conversion is recorded in the memory card 10 as a RAW image file without performing image processing other than white balance adjustment processing and digital watermark embedding will be described. It was. Development processing may be performed on the image data of the RAW image to form RGB image data, which may be recorded as a separate file together with the RAW image file.

  As described above in detail, the present invention can be used greatly in the field of digital watermarking.

It is a principle explanatory view of this embodiment. It is a block diagram which shows the structure of the electronic camera of this embodiment. This is an introductory part of a flowchart showing the operation of the present embodiment, and mainly shows the processing contents in the digital watermark first mode. It is a part of flowchart which shows operation | movement of this embodiment, and shows the processing content in a digital watermark 2nd mode. This is the final part of the flowchart showing the operation of this embodiment, and shows the processing contents in the image processing computer 8.

Explanation of symbols

2 Electronic camera 4 Imaging unit 8 Image processing computer 10 Memory card 12 Shooting lens 16 Focal plane shutter 20 Imaging element 24 Analog signal processing unit 28 A / D conversion unit 32 Timing generator 36 Color measurement unit 40 MPU
44 Operation Unit 48 System Bus 52 Image Processing Unit 56 Image Memory 60 Program Memory 64 Card Interface 72 USB
76 USB interface 80 Monitor control unit 84 LCD monitor

Claims (6)

An imaging unit that images a subject and generates image data including color information of a plurality of pixels and color information of one color component in one pixel;
An image pickup apparatus comprising: a direct embedding unit that embeds digital watermark information in the image data according to parameters of the image processing before image processing is performed on the image data. The imaging device according to claim 1,
The parameter includes a parameter for white balance adjustment. The imaging apparatus according to claim 1 or 2 ,
An image pickup apparatus comprising: a detection unit that detects the digital watermark information from the image data in which the digital watermark information is embedded. A step of said electronic watermark information to acquire the image data embedded by the image pickup apparatus of any one of claims 1 to 3,
A digital watermark detection program for causing a computer to execute the step of detecting the digital watermark information from the acquired image data. The digital watermark information is embedded in image data that includes color information of a plurality of pixels and has color information of one color component in one pixel and is not subjected to image processing. An electronic watermark embedding method characterized by the above. The digital watermark embedding method according to claim 5 .
The digital watermark embedding method, wherein the parameter includes a white balance adjustment parameter.

Images