JP2005159879A - Image processing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for automatically designing color processing parameters whereby a desired color reproduction characteristic is obtained by each exposure even when an image is photographed at variable exposures, as well as when an image is photographed at a proper exposure. <P>SOLUTION: In the information processing method for editing the color processing parameter used for image data processing, a data entry section 101 receives first target data corresponding to proper exposure and image data obtained by photographing at a second exposure different from the proper exposure. An exposure change data calculation section 103 calculates second target data corresponding to the second exposure on the basis of the first target data. A color conversion section 104 converts a color of the image data by using the color processing parameter stored in a parameter storage section 111. An evaluation calculation section 105 and a parameter update section 109 update the color processing parameters so that the color of the image data converted by the color conversion section is close to a color of the second target data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing method and apparatus for editing color processing parameters of a digital camera.

  A digital camera converts light from a subject into a digital signal using a sensor such as a CCD, stores this digitally, and performs color correction using a color processing parameter such as an internal matrix or Look Up Table. Thus, an image is generated. This color processing parameter is optimal for matching image data obtained by photographing a color chart under a specific exposure condition, for example, proper exposure, to a predetermined target (also referred to as target data), for example, a colorimetric value of the color chart. It is designed by By using this optimized color processing parameter, it is possible to give a desired color reproduction characteristic to an image photographed with appropriate exposure.

  However, in the above-described method, color processing parameters are optimized using shooting data shot under a specific condition of proper exposure. Therefore, a desired color reproduction is performed for an image shot with appropriate exposure. Although the characteristics can be obtained, there has been a problem that desired color reproduction characteristics cannot be obtained for an image photographed by changing the exposure correction amount. For example, when a human face is photographed, an image with the desired skin color is output with proper exposure, but when shooting with overexposure, a reddish or yellowish color is output. There is. In order to solve such a problem, target data for photographing data photographed under an exposure condition different from the proper exposure is required.

In the technique disclosed in Patent Document 1, shooting data of a digital camera shot with different exposure is used for designing color processing parameters. Here, the target of the photographic data with different exposure is the one obtained by photographing with the same exposure as the digital camera with a silver salt camera, printing, and colorimetry.
JP 2001-194238 A

  If the color processing parameters obtained by the technique described in Patent Document 1 are used, the same color as that of a silver salt camera can be output even when shooting is performed with different exposures. However, because the target is an image of a silver halide camera shot with the same exposure compensation amount, only color reproduction characteristics similar to those of a silver halide camera can be reproduced, and color processing parameters that have color reproduction characteristics different from those of a silver halide camera Cannot be designed.

  The present invention has been made in view of the above problems, and obtains desired color reproduction characteristics for each exposure when shooting with different exposure as well as with a captured image taken with appropriate exposure. An object of the present invention is to provide an apparatus for designing color processing parameters that can be processed.

In order to achieve the above object, an information processing method according to an aspect of the present invention includes:
An information processing method for editing color processing parameters used for image data processing,
An acquisition step of acquiring first target data including color information corresponding to the first exposure;
Calculating a second target data corresponding to a second exposure different from the first exposure based on the first target data;
A color conversion step of converting the color of the image data obtained by photographing at the second exposure using a color processing parameter;
A change step of changing the color processing parameter so that the color of the image data converted by the color conversion step approaches the second target data.

An information processing apparatus according to another aspect of the present invention for achieving the above object is
An information processing apparatus for editing color processing parameters used for image data processing,
Obtaining means for obtaining first target data including color information corresponding to the first exposure;
Calculating means for calculating second target data corresponding to a second exposure different from the first exposure based on the first target data;
Color conversion means for converting the color of image data obtained by photographing at the second exposure using color processing parameters;
Changing means for changing the color processing parameter so that the color of the image data converted by the color conversion means approaches the second target data.

  According to the above configuration, it becomes possible to create target data in the case of shooting with an exposure correction amount different from the appropriate exposure, and by designing color processing parameters using this target data, Even for an image shot with an exposure correction amount, it is possible to provide desired color reproduction characteristics for each exposure.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
<Configuration of image processing apparatus>
FIG. 1 is a block diagram showing a hardware configuration according to the first embodiment. In FIG. 1, reference numeral 1 denotes an image processing apparatus. Reference numeral 101 denotes a data input unit, which is an interface for taking in image data and target data serving as a target of an image photographed with appropriate exposure from the outside. In this embodiment, in particular, the input unit 101 inputs image data obtained by photographing the color chart 2 as shown in FIG. 2 with appropriate exposure. An average value calculation unit 102 calculates the RGB average value of each patch of the color chart image data input from the data input unit 101. Reference numeral 103 denotes an exposure change data calculation unit that calculates target data corresponding to the exposure from target data corresponding to the appropriate exposure input in the data input unit 101. A color conversion unit 104 converts input data using color processing parameters stored in the parameter holding unit 111. An evaluation value calculation unit 105 calculates an evaluation value from the input data converted by the color conversion unit 104 and the target data calculated by the exposure change data calculation unit 103.

  Reference numeral 106 denotes an output unit that outputs color processing parameters. A minimum value setting unit 107 stores the minimum value of the evaluation value calculated by the evaluation value calculation unit 105 and the color processing parameter at that time. An evaluation value determination unit 108 determines whether the evaluation value calculated by the evaluation value calculation unit 105 is equal to or less than a reference threshold value, and whether a predetermined number of calculations is satisfied. A parameter update unit 109 updates the color processing parameters held in the parameter holding unit 111.

  An input data holding unit 110 stores an RGB average value of each patch of the input image data calculated by the average value calculation unit 102 and an exposure correction amount when the input image is captured. A parameter holding unit 111 holds color processing parameters for color conversion of input data, color system conversion parameters for converting RGB values into XYZ values in CIE tristimulus values, and the number of calculations.

  Each configuration described above may be realized by software or hardware. The image processing apparatus 1 can be realized by a computer device that can connect a digital camera or the like as an external device, for example. In this case, the color processing parameter output from the output unit 106 is stored in a predetermined storage unit of the digital camera.

  FIG. 2 is a diagram illustrating an example of a color chart according to the present embodiment. The color chart 2 shown in FIG. 2 is a 4-by-6 color chart, and is composed of a patch group in which the hue changes in the row direction and the saturation changes in the column direction. The bottom row is provided with a patch group of white to black gray gradation. As described above, it is preferable that the color chart 2 covers all hues and saturations and has gray gradation. However, the number and arrangement of the color charts, the color types, and the like are merely examples, and any color chart may be used as long as it is useful for changing the color processing parameters.

<Operation in Image Processing Device>
FIG. 3 is a flowchart illustrating the process executed by the image processing apparatus 1. In step S <b> 1, the data input unit 101 reads target data corresponding to image data and image data captured with appropriate exposure. Here, the target data is color information of each patch when the color chart as shown in FIG. That is, the target data is obtained by registering a target color value, for example, a colorimetric value of the patch, for each of N patches (N = 16 in the color chart of FIG. 2) of the color chart. In this embodiment, it is assumed that the X, Y, and Z values (colorimetric values) of the patches are arranged in a predetermined order as shown in FIG. On the other hand, for example, when the color processing parameters of the digital camera are edited by the image processing apparatus 1, the image data is a color chart 2 (same color chart used to obtain the target data) as shown in FIG. It must be obtained by photographing with the digital camera. Further, if the color processing parameter at the proper exposure is adjusted, this image data needs to be image data obtained by photographing the color chart with the proper exposure by the digital camera. Further, if the color processing parameter at an exposure correction amount different from the proper exposure is adjusted, the image data obtained by photographing the color chart with the exposure correction amount needs to be obtained.

  In step S <b> 2, the average value calculation unit 102 obtains an RGB average value of each patch of the image data read in advance, uses the data as input data, and records it in the input data holding unit 110. At this time, the exposure correction amount when each input image is photographed is recorded simultaneously. In step S3, the exposure change data calculation unit 103 calculates target data other than the appropriate exposure based on the target data input in step S1. Then, target data of appropriate exposure or target data other than the calculated appropriate exposure is held as a Lab value. Note that target data calculation processing other than appropriate exposure will be described later.

  Next, the color processing parameters are updated in steps S4 to S9. First, in step S <b> 4, the parameter update unit 109 inputs an initial value 0 for the calculation count K. In step S <b> 5, the color conversion unit 104 performs color conversion of input data using the color processing parameters held in the parameter holding unit 111. An example of the internal structure of the parameter holding unit 111 is shown in FIG. As shown in FIG. 5, the parameters held by the parameter holding unit 111 are a color processing parameter, a color system conversion parameter, a maximum number of times Th1 and an evaluation reference value Th2.

In the color conversion processing, for example, the RGB value (average value) of each patch of the input data is set to (R _i , G _i , B _i ), and the color processing parameter is a matrix of 3 rows and 3 columns (a _{00 to} a ₂₂ ). In this case, conversion is performed using the following equation (1).

Further, the converted RGB data (R _Pi , G _Pi , B _Pi ) is converted into XYZ by CIE tristimulus values using the color system conversion parameters (b _{00 to} b ₂₂ ) held in the parameter holding unit 111. Convert. For example, if the held color system conversion parameter is a conversion matrix in the sRGB color space defined by IEC61966-2-1, it is converted into CIE tristimulus values XYZ using the following equation (2).

Thereafter, the white point is converted to CIELAB with D65 as post-conversion LAB data (L _Pi , a _Pi , b _Pi ). The conversion formula is shown in Formula (3).

  In this embodiment, since the case where the color system conversion parameter held in the parameter holding unit 111 is a conversion matrix in the sRGB color space defined in IEC61966-2-1 has been described as an example, conversion to CIELAB is performed. At that time, the white point was set to D65. However, when the color system conversion parameter is in another color space, it goes without saying that a white point corresponding to the color space is used.

In step S6, the evaluation value calculation unit 105 converts the converted data (L _Pi , a _Pi , b _Pi ) calculated by the color conversion unit 104 and the target data (L _Ti , a _Ti , The evaluation value is calculated from b _Ti ). For example, when the evaluation function of each patch is E _i and the overall evaluation function is E, the calculation is performed as shown in the following formula (4).

Moreover, you may set a weight individually to each patch. The evaluation function at that time is calculated using the following equation (5), where w _i is the weight value.

  In step S <b> 7, the minimum value setting unit 107 determines the minimum value of the evaluation value E calculated by the evaluation value calculation unit 105. In the present embodiment, when the evaluation value E calculated by the evaluation value calculation unit 105 is smaller than the stored minimum value Emin, the evaluation value E is overwritten on the minimum value Emin, and the color processing parameter at that time is stored. To do. If the evaluation value E is larger than the minimum value Emin, nothing is done.

  In step S8, the number of operations K is determined. If K = Th1 with respect to the maximum number of operations Th1 previously stored in the parameter storage unit 111, the process proceeds to step S9. Otherwise, if K <Th1, the process proceeds to step S11, where the parameter update unit 109 updates the color processing parameter based on a predetermined optimization method, sets the number of operations K to K = K + 1, and proceeds to step S5. Return.

  In step S9, the minimum evaluation value set in step S7 is determined. If Emin <Th2 with respect to the evaluation reference value Th2 previously held in the parameter holding unit 110, the process proceeds to step S10. Otherwise, if Emin ≧ Th2, the process proceeds to step S12, the parameter update unit 109 updates the initial value of the color processing parameter, sets the number of operations K to K = 0, and returns to step S5. When the optimization process is performed again as in step S12, a plurality of initial values are held in advance, and initial values different from the previously used initial values are used. Although it is conceivable to set the result when K = Th1 as an initial value, this method merely increases the number of repetitions, and there is a possibility that a good result cannot be obtained.

  In step S <b> 10, the output unit 106 outputs the color processing parameters stored in the minimum value setting unit 107. A well-known optimization method such as a DLS method can be used for the processing in steps S6 to S8 and step S11.

<Processing by Exposure Change Data Calculation Unit 103>
FIG. 6 is a detailed flowchart of the exposure change data calculation process (target data calculation process for other exposures) in step S3.

In step S <b> 11, the exposure change data calculation unit 103 reads input data from the input data holding unit 104. The internal structure of the input data holding unit 104 is shown in FIG. As shown in FIG. 7, the input data holding unit 104 stores the RGB average value I _T (R _Ai ) of each exposure correction amount A and each patch (0 ≦ i ≦ N: N is the number of patches) of the image corresponding thereto. , G _Ai , B _Ai ) are held. As described above, the input data holding unit 104 stores at least one different exposure correction and the RGB average value of each patch obtained from the image (A = 0 in FIG. 7) when the exposure correction amount is appropriate. An RGB average value of each patch calculated from an image obtained by using the quantity (two images of A = + a and A = −b are used in FIG. 7) is registered.

In step S12, the exposure change data calculation unit 103 reads target data (X _0i , Y _0i , Z _0i ) corresponding to the appropriate exposure input in the data input unit 101.

In step S13, the exposure change data calculation unit 103 uses an exposure correction amount A (for example, + a or −a) different from the appropriate exposure read in step S11 from the target data (X _0i , Y _0i , Z _0i ) corresponding to the appropriate exposure. Target data corresponding to the input data of b) is calculated. In the present embodiment, for example, the following digital camera characteristics are used to calculate from target data corresponding to appropriate exposure.

In a general digital camera, when the exposure correction amount is increased by one step, the amount of light received by the camera sensor from the object scene is doubled. Using this characteristic, target data when the exposure changes is calculated. Specifically, the target data (X _Ai , Y _Ai , Z _Ai ) for the input data obtained by increasing the exposure correction amount by A steps from the appropriate exposure (if A is negative, the exposure correction amount is decreased) is Is calculated by the following equation (6).

  Further, for example, as in the following formula (7), the brightness of an image shot with different exposures may be freely controlled.

  Using the calculation method as described above, target data corresponding to the RGB average value of each patch of an image taken with each exposure correction amount is calculated.

  As described above, according to the first embodiment, by inputting target data corresponding to an image photographed with proper exposure to the image processing apparatus 1, it is possible to cope with an image photographed with an exposure different from the proper exposure. Target data can be created. Furthermore, by optimizing the color processing parameters using at least a plurality of image data including images captured with appropriate exposure and the above-described target data, only images captured under limited exposure conditions of appropriate exposure Instead, desired color reproducibility can be obtained even for an image shot with an exposure different from the proper exposure.

[Second Embodiment]
FIG. 8 is a block diagram showing a hardware configuration according to the second embodiment. In FIG. 8, 3 is a target data creation device, and 4 is a color processing parameter editing device. The target creation device 3 and the color processing parameter editing device 4 are realized by one or a plurality of computer devices. The output unit 106 provides color processing parameters to a connected digital camera, for example.

  In the target data creation apparatus 3, reference numeral 301 denotes an exposure correction amount input unit for inputting an exposure correction amount. Reference numeral 302 denotes a proper target input unit that inputs target data of an image photographed with proper exposure, for example, a colorimetric value of a patch. A target data output unit 303 outputs target data. An exposure change data calculation unit 304 calculates a target corresponding to the exposure from target data corresponding to the appropriate exposure input by the appropriate target input unit 302.

  In the color processing parameter editing apparatus 4, reference numeral 401 denotes an image data input unit, which is an interface with an external apparatus for inputting image data. Reference numeral 402 denotes an average value calculation unit that calculates an RGB average value of each patch of the image data input from the image data input unit 401. Reference numeral 403 denotes a target data input unit which reads target data that is an output of the target creation device 3. Reference numeral 404 denotes a color conversion unit that converts input data using color processing parameters stored in the parameter holding unit 410. An evaluation value calculation unit 405 calculates an evaluation value from the input data converted by the color conversion unit 404 and the target data input by the target data input unit 403.

  Reference numeral 406 denotes an output unit that outputs color processing parameters. A minimum value setting unit 407 stores the minimum value of the evaluation value calculated by the evaluation value calculation unit 405 and the color processing parameter at that time. Reference numeral 408 denotes an evaluation value determination unit that determines whether the evaluation value calculated by the evaluation value calculation unit 406 is equal to or less than a reference threshold value and whether a predetermined number of operations is satisfied. A parameter update unit 409 updates the color processing parameters held in the parameter holding unit 410. A parameter holding unit 410 holds color processing parameters for color conversion of input data, color system conversion parameters for converting RGB values into CIE tristimulus values XYZ values, and the number of calculations.

  FIG. 9 is a flowchart illustrating processing according to the second embodiment. In step S <b> 21, target data is created by the target data creation device 3. In step S <b> 22, the color processing parameter editing device 4 optimizes the color processing parameters using the target created by the target data creation device 3. The target data creation device 3 and the color processing parameter editing device 4 can be directly connected by a connection means such as USB or IEEE1394, and can exchange target data. Hereinafter, the operation of each apparatus will be described.

<Operation in Target Creation Device 3>
FIG. 10 is a flowchart for explaining the details of the target data creation process executed by the target data creation device 3 in step S21.

  In step S31, the exposure correction amount input unit 301 reads the exposure correction amount. The user can input an arbitrary exposure correction amount, and target data corresponding to the input exposure correction amount is generated in the subsequent processing. In step S32, the reference data input unit 302 sets the target data of each patch in the image obtained by photographing the color chart 2 as shown in FIG. 2 with appropriate exposure (for example, the colorimetric value of each patch of the color chart 2). Is read. A file described in a predetermined format is used for data input. For example, a patch in which the XYZ values of patches are described in a predetermined order as shown in FIG. In step S <b> 33, the exposure change data calculation unit 304 calculates target data corresponding to the exposure correction amount input by the exposure correction amount input unit 301. Since the calculation method is the same as step S13 of the first embodiment, a description thereof will be omitted. In step S34, the target data output unit 303 outputs the target data created by the exposure change data calculation unit 304.

<Operation in Color Processing Parameter Editing Device 4>
FIG. 11 is a flowchart for explaining the details of the color parameter editing process executed by the color processing parameter editing device 4 in step S22.

  In step S41, the data input unit 401 reads image data. In order to edit the color processing parameters of the digital camera by the color processing parameter editing device 4, this image data needs to be an image obtained by photographing an image such as the color chart 2 shown in FIG. 2 with the digital camera. There is. If it is desired to edit the color processing parameter at the appropriate exposure, the image data is data obtained by photographing the color chart 2 with the appropriate exposure. If the color processing parameter at the desired exposure correction amount is to be edited, the exposure correction amount. The color chart 2 is taken as data. At this time, the exposure correction amount is input to the target data creation device 3 via the exposure correction amount input unit 301, and target data corresponding to the exposure correction amount is supplied to the color processing parameter editing device 4.

  In step S42, the average value calculation unit 402 obtains an RGB average value of each patch for each image data read in step S41, and holds the obtained data as input data. In step S43, the target data input unit 403 reads target data corresponding to the exposure (appropriate exposure or desired exposure correction amount) corresponding to the color processing parameter to be edited from the creation device 3.

  In step S <b> 44, the parameter update unit 409 inputs an initial value 0 for the number of operations K. In step S <b> 45, the color conversion unit 404 performs color conversion of input data using the color processing parameters held in the parameter holding unit 410. Note that the color conversion process is the same as that in the first embodiment, and is omitted.

In step S46, the evaluation value calculation unit 405 converts the converted data (L _Pi , a _Pi , b _Pi ) calculated by the color conversion unit 404 and the target data (L _Ti , a _Ti , The evaluation value is calculated from b _Ti ). In step S <b> 47, the minimum value setting unit 407 performs minimum value determination of the evaluation value E calculated by the evaluation value calculation unit 405. When the evaluation value E calculated by the evaluation value calculation unit 405 is smaller than the stored minimum value Emin, the evaluation value E is overwritten on the minimum value Emin, and the color processing parameter at that time is stored. If the evaluation value E is greater than the minimum value Emin, nothing is done.

  In step S48, the number of operations K is determined. If K = Th1 with respect to the maximum number of operations Th1 previously held in the parameter holding unit 410, the process proceeds to step S49. Otherwise, if K <Th1, the process proceeds to step S51, where the parameter updating unit 409 updates the color processing parameter in accordance with a predetermined optimization method, sets the number of operations K to K = K + 1, and proceeds to step S45. Return to.

  In step S49, the minimum evaluation value set in step S47 is determined. If Emin <Th2 with respect to the evaluation reference value Th2 previously held in the parameter holding unit 410, the process proceeds to step S50. Otherwise, if Emin ≧ Th2, the process proceeds to step S52, the parameter update unit 409 updates the initial value of the color processing parameter, sets the calculation count K to K = 0, and returns to step S45. In step S50, the output unit 406 outputs the color processing parameters stored in the minimum value setting unit 407. Note that an optimization method such as a DLS method may be used for the optimization of the color processing parameters in steps S46 to S48 and step S51. The initial value change in step S52 is as described above with respect to step S12.

  As described above, according to the second embodiment, by inputting target data corresponding to an image photographed with appropriate exposure and a value of a necessary exposure correction amount to the target creation device 3, photographing with various exposures is possible. Target data corresponding to the processed image can be created. The created target data can be freely input to a device for optimizing color processing parameters such as the color processing parameter editing device 4 using a network or a recording medium. Design becomes possible.

  As described above, according to the configuration of each embodiment, it is possible to create target data when shooting is performed with an exposure correction amount different from the appropriate exposure. By designing color processing parameters using this target, it is possible to give a desired color reproduction characteristic for each exposure to an image captured with any exposure correction amount. That is, the target at the proper exposure is set to obtain a desired color reproduction characteristic, and based on this, the target data for each exposure correction amount is derived, so the desired color reproduction characteristic is obtained for each exposure. You can have it.

<Modification>
In each of the above embodiments, the CIE tristimulus values XYZ are used as target data. However, the color system representing the target data is not limited to the XYZ space, and may be a CIELAB space or a CIELUV space. good.

  In the second embodiment, the target data created by the target creation device 3 is directly input to the color processing parameter editing device 4. However, the target data is once stored in a recording medium such as a compact flash (registered trademark) card or an optical disk. Data may be recorded.

  In each of the above embodiments, the DLS method is used to optimize the color processing parameter. For example, the steepest descent method, the Newton method, the quasi-Newton method, and the optimization method such as the genetic algorithm GA are used. It goes without saying that can be used.

<Storage medium>
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

  As a storage medium for supplying the program code, for example, a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the computer based on the instruction of the program code. It goes without saying that a part of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.

  Further, after the program code read from the storage medium is written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

It is a block diagram which shows the structure of the image processing apparatus by 1st Embodiment. It is a figure which shows the example of a color chart. 3 is a flowchart illustrating a processing flow in the image processing apparatus according to the first embodiment. It is a figure which shows the example of description of target data. It is a figure which shows the data structural example in a parameter holding | maintenance part. It is a flowchart explaining the procedure of the target data generation by the exposure change data calculation part in 1st Embodiment. It is a figure which shows the data structural example in an input data holding part. It is a block diagram which shows the structure of the system by 2nd Embodiment. It is a flowchart which shows the outline | summary of the process by 2nd Embodiment. Figure. It is a flowchart explaining the procedure of the target data production | generation by the target production apparatus in 2nd Embodiment. It is a flowchart explaining the process by the color processing parameter editing apparatus in 2nd Embodiment.

Claims (12)

An information processing method for editing color processing parameters used for image data processing,
An acquisition step of acquiring first target data including color information corresponding to the first exposure;
Calculating a second target data corresponding to a second exposure different from the first exposure based on the first target data;
A color conversion step of converting the color of the image data obtained by photographing at the second exposure using a color processing parameter;
An information processing method comprising: a changing step of changing the color processing parameter so that the color of the image data converted by the color conversion step approaches the second target data.   The information processing method according to claim 1, wherein the first exposure is a proper exposure. The changing step includes
An evaluation value calculating step for calculating an evaluation value corresponding to a deviation amount between the color of the image data after the conversion by the color conversion step and the second target data;
The information processing method according to claim 1, further comprising a parameter update step of optimizing the color processing parameter so that the evaluation value is equal to or less than a predetermined value.   The information processing method according to claim 1, wherein the first target data is a colorimetric XYZ value of a predetermined color chart. In the calculating step, when the second exposure is obtained by changing the exposure correction amount from the first exposure by an A level, the colors in the first target data are set to X ₀ , Y ₀ , and Z ₀ . The colors X _A , Y _A , Z _A in the second target data,

The information processing method according to claim 4, wherein the information processing method is calculated by:   The information processing method according to claim 1, wherein the first and second target data are expressed in a model-independent color space.   4. The information processing method according to claim 3, wherein the evaluation value calculating step converts the color of the image data and the second target data into LAB data by CIELAB, and calculates a deviation amount thereof.   The information processing method according to claim 1, further comprising an output step of outputting the color processing parameter changed in the changing step together with exposure information indicating the second exposure. .     The color processing parameter according to claim 1, further comprising a color processing step of changing a color of image data obtained by photographing with the second exposure using the color processing parameter changed in the changing step. Information processing method. An information processing apparatus for editing color processing parameters used for image data processing,
Obtaining means for obtaining first target data including color information corresponding to the first exposure;
Calculating means for calculating second target data corresponding to a second exposure different from the first exposure based on the first target data;
Color conversion means for converting the color of image data obtained by photographing at the second exposure using color processing parameters;
An information processing apparatus comprising: a changing unit that changes the color processing parameter so that the color of the image data converted by the color conversion unit approaches the second target data.   A control program for causing a computer to execute the information processing method according to claim 1.   A storage medium for storing a control program for causing a computer to execute the information processing method according to claim 1.

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