JP2014042205A - Image processing device, image processing method, and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device and the like that are capable of creating image data faithfully representing a color of a subject without the need to create a profile each time the subject is photographed.SOLUTION: A plurality of profiles created for respective exposure settings are prepared in advance, an optimum profile is selected therefrom on the basis of an exposure setting in photographing a subject, and image data is corrected using the selected profile.

Description

  The present invention relates to a technical field such as an apparatus for creating image data that faithfully reproduces the color of a subject.

  Conventionally, art objects such as paintings are photographed with a digital camera, and images are posted on a website or printed. An image obtained by photographing such a work of art is required to faithfully reproduce the actual color. However, a general digital camera performs color adjustment such as making the color brighter than the actual product, and the degree of adjustment varies depending on the model or camera manufacturer.

  For this reason, a technique has been adopted in which the actual color is faithfully reproduced by correcting image data obtained by photographing with a digital camera. For example, as in the technique described in Patent Document 1, a method is known in which a color chart is photographed, a profile (including a LUT (Look up Table)) is created, and the color of the subject is obtained with high colorimetric accuracy. ing.

JP 2007-324970 A

  However, in the conventional technique such as the technique described in Patent Document 1, it is necessary to create a profile by photographing a color chart for each subject. In addition, if the exposure setting at the time of shooting is not performed accurately, the image becomes brighter or darker, and there is a problem that the color of the artwork cannot be expressed faithfully. Therefore, every time a subject is photographed, it is necessary to perform exposure setting accurately and create a profile, and much labor is required when photographing a large number of subjects.

  The present invention has been made in view of such problems, and it is not necessary to create a profile every time a subject is photographed, and image processing that can create image data that faithfully represents the color of the subject. It is an object to provide a device or the like.

  In order to solve the above-mentioned problem, the invention according to claim 1 is based on image data obtained by photographing a color chart with a camera at different exposure settings, and includes a plurality of profiles created for each exposure setting. Profile storage means for storing, image data acquisition means for acquiring image data obtained by photographing the plane portion of a subject having a plane portion with a camera, and an image represented by the image data acquired by the image data acquisition means Created by shooting the color chart with the same exposure setting as the specified exposure setting from among a plurality of profiles stored in the profile storage means, and an exposure specifying means for specifying the exposure setting when shooting A profile selection means for selecting the selected profile, and the acquired image using the selected profile. Corrected over data, an image processing apparatus characterized by comprising, a corrected image data generating means for generating corrected image data.

  A second aspect of the present invention is the image processing apparatus according to the first aspect, wherein the profile storage means obtains image data obtained by changing the exposure setting for photographing the color chart by n stages. Created based on color values (for example, RGB values) specified for each color and color measurement values (for example, L * a * b * values) specified by measuring the color chart with a colorimeter. The n number of profiles are stored.

  A third aspect of the present invention is the image processing apparatus according to the second aspect, wherein the color value fixes a shutter speed setting value in a camera that captures the color chart, and an aperture value (F value). Is changed for n stages, and is specified for each image data obtained by changing the exposure setting for n stages.

  The invention according to claim 4 is the image processing apparatus according to claim 2 or 3, wherein n profiles are created based on the color values for n stages and the colorimetric values. It is characterized by further comprising creation means.

  A fifth aspect of the present invention is the image processing apparatus according to any one of the first to fourth aspects, wherein the image data acquired by the image data acquiring unit is captured when the image data is captured. Exposure setting information indicating the exposure setting is associated, and the exposure specifying unit specifies the exposure setting with reference to the exposure setting information associated with the image data.

  The invention according to claim 6 is an image processing method performed by an image processing apparatus, and an image data acquisition step of acquiring image data obtained by photographing the plane portion of a subject having a plane portion with a camera; An exposure specifying step for specifying an exposure setting when the image represented by the image data acquired by the image data acquisition step is shot, and image data obtained by shooting a color chart with different exposure settings by the camera. The color chart is created by photographing the color chart with the same exposure setting as the specified exposure setting from the plurality of profiles stored in the profile storage means for storing the plurality of profiles created for each exposure setting. A profile selection step of selecting the acquired profile and the acquired image data using the selected profile. Corrected, characterized in that it comprises a and a corrected image data creation step of creating the corrected image data.

  The invention according to claim 7 is an image comprising profile storage means for storing a plurality of profiles created for each exposure setting based on image data obtained by photographing a color chart with a camera at different exposure settings. A computer included in the processing apparatus represents image data acquired by the image data acquisition unit, image data acquisition unit for acquiring image data obtained by photographing the plane unit of a subject having a plane unit with the camera, and the image data acquired by the image data acquisition unit Created by photographing the color chart with the same exposure setting as the identified exposure setting from among a plurality of profiles stored in the profile storage means, an exposure specifying means for specifying an exposure setting at the time of taking an image Profile selection means for selecting the selected profile, using the selected profile, Correcting the acquired image data, corrected image data generating means for generating corrected image data, an image processing program to function as a.

  According to the present invention, since the image data is corrected based on the optimum profile selected from the profiles created in advance for each exposure setting, it is not necessary to create a profile each time a subject is photographed. Image data that faithfully represents the color of the subject can be created.

3 is a conceptual diagram for explaining functions of the image processing apparatus 1. FIG. 1 is a block diagram illustrating an example of a configuration of an image processing device 1. FIG. (A) It is a figure which shows an example of input profile IPF (scanner profile). (B) It is a figure which shows an example of output profile OPF (color space profile). It is a figure which shows an example of arrangement | positioning of the camera 31 at the time of imaging | photography the color chart 33 with the camera 31. FIG. 4 is a flowchart illustrating an example of image correction processing by a control unit 11 of the image processing apparatus 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present embodiment is an embodiment in which the present invention is applied to the image processing apparatus 1.

  As shown in FIG. 1, the image processing apparatus 1 (an example of “image processing apparatus”) according to the present embodiment has a plurality of input profiles IPFn (n = 1, 2, 3,..., 9) and outputs. A profile OPF is stored. In the present embodiment, the nine input profiles IPFn include image data (data holding RGB values for each pixel) obtained by photographing a color chart while changing exposure settings in nine steps, and a color chart. It is created on the basis of the colorimetric values obtained by performing colorimetry with. When the image processing apparatus 1 captures image data BD obtained by capturing a surface (an example of a “plane part”) on which a picture of a painting (an example of a “subject”) is drawn, the image processing apparatus 1 includes the input profile IPF and the output profile OPF. An image correction process for creating corrected image data AD corrected based on the image data is performed. Specifically, the image processing apparatus 1 uses intermediate data MD (L * a * b * value for each pixel) using an input profile IPF that appropriately selects image data BD (data that holds RGB values for each pixel). ), And intermediate image MD is created as corrected image data AD (data holding RGB values for each pixel) using output profile OPF.

  Next, the configuration of the image processing apparatus 1 will be described with reference to FIG. The image processing apparatus 1 includes a control unit 11, a storage unit 12, an interface unit 13, a display unit 14, and an operation unit 15.

  The storage unit 12 includes, for example, a hard disk drive (HDD) and stores various programs such as an operating system and application programs. In particular, the storage unit 12 of the present embodiment stores an application program (hereinafter referred to as “image correction application”) for performing image correction processing. Note that the various programs may be acquired from another server device or the like via a network, or may be recorded on a recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc) to be a drive device. You may make it read via.

  The storage unit 12 (an example of “profile storage unit”) stores the input profiles IPF1 to IPF9 and the output profile OPF.

  Here, the input profile IPFn and the output profile OPF will be described. The input profile IPFn is a so-called scanner profile. A profile is generally structured to hold two LUTs, one is a LUT (AtoB) that converts color values to L * a * b * values, and the other is L * a * b *. LUT (BtoA) that converts values to color values. As shown in FIG. 3A, the scanner profile (input profile IPFn) holds an LUT (AtoB) that converts an RGB value (an example of “color value”) into an L * a * b * value.

  On the other hand, the output profile OPF is a so-called color space profile. As shown in FIG. 3B, the color space profile (output profile OPF) includes an LUT (AtoB) that converts RGB values to L * a * b * values, and L * a * b * values to RGB values. This profile holds the LUT (BtoA) value to be converted. As the output profile OPF in this embodiment, a conventionally known profile (a profile installed in image processing software or a camera, a profile that can be downloaded from a manufacturer's website, or the like) is used. The output profile OPF can use sRGB of the international standard defined by the International Electrotechnical Commission (IEC) or AdobeRGB defined by Adobe Systems.

  That is, the image processing apparatus 1 converts the image data BD (RGB value) into the intermediate data MD (L * a * b * value) using the AtoB LUT of the input profile IPFn, and also outputs the BtoA of the output profile OPF. The intermediate data MD (L * a * b * value) is converted into corrected image data AD (RGB value) using the LUT.

  Next, a method for creating the input profile IPFn will be briefly described.

  First, as shown in FIGS. 4A and 4B, a color chart 33 (for example, “Color Checker SG” manufactured by x-rite, etc. can be used) is photographed by the digital camera 31. As shown in FIG. 4A, light sources 32L and 32R are provided at 45 degrees to the left and 45 degrees to the right with respect to the color chart 33. The light sources 32L and 32R have light source unevenness on the color chart 33. Let the light shine evenly to prevent it from happening. It should be noted that whether or not the light source unevenness has occurred is determined by the PC (Personal Computer) connected to the digital camera 31 using the RGB values of the gray patches (color patches representing gray) provided at the four corners of the color chart 33. This can be done by checking on the display unit. That is, if the RGB values at the four corners are substantially the same value, it can be determined that light source unevenness has not occurred. Further, the illuminance at the four corners is measured using an illuminometer, and if the values are substantially the same, it can be determined that light source unevenness has not occurred.

  The color chart 33 is shot for nine stages while changing the exposure setting. Specifically, the exposure settings are -2, -1, 1/2, --1, -1/2, proper exposure, +1/2, +1, +1 1/2, Change to +2 steps and shoot. The exposure setting can be changed by changing the aperture value (F value) of the digital camera 31. At this time, the shutter speed is constant (fixed). The appropriate exposure is such that the R value, G value, and B value of the color patch representing white are about 240, respectively.

  When shooting for nine stages is completed, each image data is taken into the image processing apparatus 1.

  Next, in a state where light is uniformly applied to the color chart 33 so as not to cause light source unevenness, L * a * b * values (“second colorimetry”) which are colorimetric values of each color patch in the color chart 33. An example of “value”.) Is measured using a colorimeter. The measured L * a * b * value is taken into the image processing apparatus 1.

  Next, the input profiles IPF1 to IPF9 for nine levels are obtained from the correspondence between the RGB values of the nine levels of image data captured in the image processing apparatus 1 and the L * a * b * values measured by the colorimeter. create. For creating the input profile IPFn, conventionally known profile creation software (for example, ProfileMaker of x-rite) can be used. In the profile creation software, the user selects “scanner” as the type of profile to be created, and captures the image data of the color chart 33 and the L * a * b * values of the color chart 33 measured in advance by a colorimeter. Later, by selecting a profile creation button, a profile is created from the correspondence between the RGB values of the image data and the L * a * b * values. The input profiles IPF1 to IPF9 created in this way are stored in the storage unit 12.

  The interface unit 13 serves as a window for data exchanged with other devices and devices. For example, the interface unit 13 performs data conversion when receiving image data captured by a digital camera (not shown), data conversion when receiving colorimetric value data obtained from a colorimeter (not shown), and the like.

  The display unit 14 is configured by a liquid crystal display, for example, and displays an operation screen or the like when the operator operates the image processing apparatus 1. The operation unit 15 includes, for example, a keyboard, a mouse, and the like. The operation unit 15 receives an operation by the operator and transmits an operation signal indicating the operation content to the control unit 11.

  The control unit 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. And the control part 11 as a computer performs an image correction process by reading and executing the image correction application memorize | stored in the memory | storage part 12. FIG. The control unit 11 functions as an image data obtaining unit, an exposure specifying unit, a profile selecting unit, a corrected image data creating unit, and a profile creating unit.

  Next, image correction processing by the control unit 11 will be described with reference to FIG. Note that the input profiles IPF1 to IPF9 and the output profile OPF are stored in the storage unit 12 before the processing shown in FIG.

  First, the control unit 11 acquires image data BD obtained by photographing a picture with the digital camera 31 (step S1). When shooting a picture, the exposure setting can be changed according to the size of the area of the white part or black part used in the picture. At this time, it is not necessary to measure the exposure strictly, and the exposure setting can be appropriately determined within the range of common sense. However, the shutter speed is set to the same setting as when the color chart 33 is photographed. The image data BD is associated with aperture value information (an example of “exposure setting information”) indicating an aperture value (F value) when a picture is taken. The aperture value information may be embedded in the image data BD, or may be associated in another format. Note that the control unit 11 acquires aperture value information associated with the image data BD together with the image data BD in the process of step S1.

  Next, the control unit 11 specifies the exposure setting when the image represented by the image data BD is taken (step S2). Specifically, the control unit 11 specifies an aperture value (F value) with reference to aperture value information associated with the image data BD acquired in step S1.

  Next, the control unit 11 selects an appropriate input profile from the input profiles IPF1 to IPF9 stored in the storage unit 12 (step S3). Specifically, the control unit 11 selects an input profile IPF obtained by photographing a color chart with the same aperture value (F value) as the aperture value (F value) specified in the process of step S2. For example, if the aperture value (F value) specified in the process of step S2 is F4.0, the aperture value (F value) is set to F4.0 and is created by photographing a color chart. Select the input profile IPF.

  Next, the control unit 11 corrects the image data BD acquired in the process of step S1 using the input profile IPF and the output profile OPF selected in the process of step S3, and creates corrected image data AD (step). S4).

  Next, the control unit 11 records (saves) the corrected image data AD created in the process of step S4 in the storage unit 12 (step S5), and ends the image correction process shown in this flowchart.

  As described above, in the image processing apparatus 1 according to the present embodiment, the storage unit 12 converts image data obtained by photographing the color chart 33 with different exposure settings using the digital camera 31 (an example of “camera”). Based on this, a plurality of profile IPFs created for each exposure setting are stored, and the control unit 11 (“image data acquisition unit”, “exposure specifying unit”, “profile selection unit”, “corrected image data generation unit”). Image data BD obtained by photographing a surface (an example of a “planar portion”) on which a picture of an image of painting (an example of “subject”) is drawn (an example of a “planar portion”) with a digital camera 31; The exposure setting when the image represented by the image data BD is captured is identified, and the color chart 33 is captured with the same exposure setting as the identified exposure setting from the plurality of profiles IPF stored in the storage unit 12. Select the profile IPF created by using the profile IPF selected, the image data is corrected BD, it creates the corrected image data AD.

  According to the image processing apparatus 1 of the present embodiment, since the image data BD is corrected based on the optimal input profile IPF selected from the input profiles IPF created for each exposure setting in advance, the painting is There is no need to create an input profile IPF each time a picture is taken, and corrected image data AD that faithfully represents the color of a painting can be created.

  The present invention is not limited to the present embodiment, and various other changes can be made.

  In the present embodiment, in the process of step S3 in FIG. 5, the input profile IPF obtained by photographing the color chart with the same aperture value (F value) as the aperture value (F value) specified in the process of step S2 is obtained. For example, if the aperture value (F value) specified in step S2 does not match the aperture value (F value) when the color chart is taken, the closest aperture value is selected. An input profile IPF obtained by photographing a color chart with (F value) is selected. This eliminates the restriction that you must shoot with the same aperture value (F value) as any of the aperture values (F value) when shooting a color chart. The degree of freedom increases.

  Furthermore, in the present embodiment, the storage unit 12 stores nine profile IPFs created based on the colorimetric values obtained by photographing the color chart while changing the exposure setting in nine steps. The number n of profile IPFs can be changed as appropriate. In that case, the profile IPF is created based on the colorimetric values obtained by photographing the color chart while changing the exposure setting by n steps according to the number n of profile IPFs to be created.

  Furthermore, in this embodiment, the shutter speed is fixed, and the aperture value (F value) is changed in multiple steps (in this embodiment, 9 steps), thereby defining the exposure setting in multiple steps. It is also possible to define a plurality of exposure settings by changing the aperture value (F value). Since exposure is determined by a combination of shutter speed and aperture value (F value), a plurality of exposure settings can be defined for each combination of shutter speed and aperture value (F value). In the case of this configuration, an input profile IPF is created and stored in the storage unit 12 for each combination. Further, at the time of taking a picture, exposure information indicating a shutter speed and an aperture value (F value) is associated with the image data BD. In the process of step S2, the control unit 11 specifies the exposure setting with reference to the exposure information, and in the process of step S3, selects the input profile IPF created with the same exposure setting as the specified exposure setting. To do.

DESCRIPTION OF SYMBOLS 1 Image processing apparatus 11 Control part 12 Storage part 13 Interface part 14 Display part 15 Operation part BD Image data AD Corrected image data

Claims (7)

Profile storage means for storing a plurality of profiles created for each exposure setting based on image data obtained by photographing a color chart with a camera using different exposure settings;
Image data acquisition means for acquiring image data obtained by photographing the plane portion of a subject having a plane portion with the camera;
Exposure specifying means for specifying an exposure setting when the image represented by the image data acquired by the image data acquiring means is captured;
Profile selection means for selecting a profile created by photographing the color chart with the same exposure setting as the specified exposure setting from a plurality of profiles stored in the profile storage means;
Corrected image data creating means for correcting the acquired image data and creating corrected image data using the selected profile;
An image processing apparatus comprising: The image processing apparatus according to claim 1,
The profile storage means performs colorimetry on the color value specified for each image data obtained by changing the exposure setting at the time of photographing the color chart by n steps, and the color chart by a colorimeter. An image processing apparatus that stores n profiles created based on specified colorimetric values. The image processing apparatus according to claim 2,
The image obtained by changing the exposure setting by n steps by fixing the setting value of the shutter speed in the camera that captures the color chart and changing the aperture value (F value) by n steps. An image processing apparatus characterized by being specified for each data. The image processing apparatus according to claim 2 or 3,
An image processing apparatus, further comprising: profile creation means for creating n profiles based on the color values for n stages and the colorimetric values. The image processing apparatus according to any one of claims 1 to 4,
The image data acquired by the image data acquisition means is associated with exposure setting information indicating exposure setting when the image data is captured,
The image processing apparatus characterized in that the exposure specifying means specifies exposure setting with reference to exposure setting information associated with image data. An image processing method performed by an image processing apparatus,
An image data acquisition step of acquiring image data obtained by photographing the plane portion of the subject having the plane portion with a camera;
An exposure specifying step for specifying an exposure setting when the image represented by the image data acquired by the image data acquiring step is captured;
Based on image data obtained by photographing a color chart with a different exposure setting by the camera, from among a plurality of profiles stored in a profile storage means for storing a plurality of profiles created for each exposure setting. A profile selection step of selecting a profile created by photographing the color chart with the same exposure setting as the specified exposure setting;
A corrected image data creation step of correcting the acquired image data and creating corrected image data using the selected profile;
An image processing method comprising: A computer included in an image processing apparatus including profile storage means for storing a plurality of profiles created for each exposure setting based on image data obtained by photographing a color chart with a camera using different exposure settings,
Image data acquisition means for acquiring image data obtained by photographing the plane portion of a subject having a plane portion with the camera;
Exposure specifying means for specifying an exposure setting when the image represented by the image data acquired by the image data acquiring means is captured;
Profile selection means for selecting a profile created by photographing the color chart with the same exposure setting as the specified exposure setting from a plurality of profiles stored in the profile storage means,
Corrected image data creating means for correcting the acquired image data and creating corrected image data using the selected profile;
An image processing program that functions as

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