JP2016082527A - Calibration system, calibration method, image forming apparatus, and calibration program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a calibration system, calibration method, image forming apparatus, and calibration program that can update an appropriate gamma correction table out of a plurality of gamma correction tables.SOLUTION: An MFP in a calibration system prints a test sheet provided with a figure for identifying a gamma correction table to be applied during printing of a test chart out of a plurality of gamma correction tables (S101), creates a gamma correction table on the basis of color values of patches included in a test chart and a reference chart in an image created by photographing in S102 the test sheet and reference chart simultaneously with a smartphone (S104), and updates the gamma correction table specified in S103 by the figure on the test sheet in the image to the gamma correction table created in S104.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a calibration system, a calibration method, an image forming apparatus, and a calibration program for correcting gradation characteristics.

  2. Description of the Related Art Conventionally, as a calibration method for correcting input / output characteristics due to aging of image forming apparatuses such as a printer dedicated machine and an MFP (Multifunction Peripheral), so-called gamma correction, a scanner or an image forming apparatus attached to the MFP A method is known in which the current output color is measured using the density sensor in the image sensor, and the input / output characteristics are corrected so that the color value of the output color becomes the target color value.

  However, an expensive dedicated colorimeter such as a spectrocolorimeter is required in order to align the color values of output colors between image forming apparatuses of different models. However, preparing and using a dedicated colorimeter is a hurdle for general users.

  Therefore, a calibration system has been proposed that realizes simple and low-cost calibration by using a photographing device such as a digital camera or a camera-equipped mobile phone as an alternative device for a dedicated colorimeter (for example, patents). References 1 and 2).

  In the calibration system described in Patent Document 1, first, a reference chart including a plurality of color patches and a test chart printed by the image forming apparatus corresponding to the reference chart are simultaneously photographed by the photographing device. . Then, the gradation characteristics of the image forming apparatus are corrected based on the RGB values of the patches of the reference chart and the test chart in the image captured and generated by the imaging device.

  In the calibration system described in Patent Document 2, first, a reference chart including a plurality of color patches and a test chart printed by an image forming apparatus corresponding to the reference chart are separately photographed by a photographing device. The Next, the color value of the patch of the reference chart in the first image captured and generated by the imaging device and the color value of the patch of the test chart in the second image captured and generated by the imaging device Based on this, a first correction value is calculated. Further, the second correction value is based on the color value of the patch of the reference chart in the first image captured and generated by the image capturing device and the reference color value stored in advance in the image forming apparatus. Is calculated. Then, the gradation characteristics of the image forming apparatus are corrected based on the first correction value and the second correction value.

JP 2006-222552 A JP 2010-226562 A

  However, the calibration system described in Patent Document 1 or Patent Document 2 does not consider the case where any of a plurality of gamma correction tables is applied when printing a test chart. When any one of the plurality of gamma correction tables is applied at this time, there is a problem that an appropriate gamma correction table is not always updated among the plurality of gamma correction tables.

  Accordingly, an object of the present invention is to provide a calibration system, a calibration method, an image forming apparatus, and a calibration program that can update an appropriate gamma correction table among a plurality of gamma correction tables.

  The calibration system of the present invention generates an imaging device, an image forming apparatus that generates a sheet by printing a chart including a plurality of color patches, and a gamma correction table for correcting gradation characteristics of the image forming apparatus. The image forming apparatus identifies a gamma correction table to be applied when printing the chart among the plurality of gamma correction tables. Sheet printing means for printing the sheet to which identification information has been added, and the table generation means includes the sheet and a reference chart corresponding to the chart that are simultaneously captured by the imaging device and generated in the image. Based on the color values of the chart and the patch of the reference chart Generating the gamma correction table for correcting the gradation characteristic of the image forming apparatus to the gradation characteristic according to the reference chart, and the table updating means is specified by the identification information of the sheet in the image The gamma correction table is updated to the gamma correction table generated by the table generating means.

  With this configuration, the calibration system of the present invention prints a sheet to which identification information for identifying a gamma correction table applied when printing a chart among a plurality of gamma correction tables is printed by the image forming apparatus. Since the gamma correction table specified by the sheet identification information in the image captured and generated by the imaging device is updated to generate the correction table, an appropriate gamma correction table among the plurality of gamma correction tables is updated. Can do.

  In the calibration system of the present invention, the sheet printing unit may add the identification information including at least one of the shape and the number of figures to the sheet.

  With this configuration, the calibration system of the present invention can easily read the identification information from the image captured and generated by the imaging device to generate the gamma correction table. The processing load of reading can be reduced.

  In the calibration system of the present invention, the image forming apparatus is applied by the screen processing unit that reproduces a halftone by applying any of a plurality of screens to the image data, and the screen processing unit. Gamma correction means for correcting the gradation characteristics of the image forming apparatus by applying the gamma correction table corresponding to the screen, and the identification information identifies the screen applied at the time of printing the chart It may be information.

  With this configuration, the calibration system of the present invention can specify not only the gamma correction table applied at the time of printing the chart but also the screen, so that convenience can be improved.

  In the calibration system of the present invention, the image forming apparatus may include the table generating unit.

  With this configuration, in the calibration system of the present invention, since the photographing device does not need to include a table generating unit, a general photographing device can be used, and convenience can be improved.

  In the calibration system of the present invention, the imaging device includes the table generation unit and a table transmission unit that transmits the gamma correction table generated by the table generation unit to the image forming apparatus. The transmission unit may also transmit information of the gamma correction table specified by the identification information of the sheet in the image to the image forming apparatus.

  With this configuration, the calibration system of the present invention does not need to include a table generating unit in the image forming apparatus, so that the processing load on the image forming apparatus when updating the gamma correction table can be suppressed.

  The calibration method of the present invention includes a table generation step for generating a gamma correction table for correcting gradation characteristics of an image forming apparatus that generates a sheet by printing a chart including a plurality of color patches, and the gamma correction table. A table updating step for updating the sheet, and a sheet printing step for printing the sheet to which identification information for identifying a gamma correction table applied when printing the chart among a plurality of the gamma correction tables is printed, The table generating step is based on the color values of the chart and the patch of the reference chart in the image generated by simultaneously shooting the sheet and the reference chart corresponding to the chart by the shooting device. The reference characteristics The gamma correction table for correcting the gradation characteristics along the line is generated, and the table update step includes the step of generating the gamma correction table specified by the identification information of the sheet in the image by the table generation step. The step is to update the generated gamma correction table.

  With this configuration, the calibration method of the present invention prints a sheet to which identification information for identifying a gamma correction table applied when printing a chart among a plurality of gamma correction tables is printed by the image forming apparatus. Since the gamma correction table specified by the sheet identification information in the image captured and generated by the imaging device is updated to generate the correction table, an appropriate gamma correction table among the plurality of gamma correction tables is updated. Can do.

  The image forming apparatus of the present invention is an image forming apparatus that generates a sheet by printing a chart including a plurality of color patches, and a table that generates a gamma correction table for correcting gradation characteristics of the image forming apparatus. Generating means; table updating means for updating the gamma correction table; and printing the sheet to which identification information for identifying a gamma correction table to be applied when printing the chart among a plurality of gamma correction tables is provided. A sheet printing unit, and the table generating unit converts the chart and a reference chart corresponding to the chart into color values of the chart and the patch of the reference chart in an image generated by shooting simultaneously with a shooting device. Based on the reference char- acteristics, The gamma correction table that corrects the gradation characteristics along the line is generated, and the table update unit generates the gamma correction table specified by the identification information of the sheet in the image. The gamma correction table is updated.

  With this configuration, the image forming apparatus of the present invention prints a sheet to which identification information for identifying a gamma correction table applied when printing a chart is printed out of a plurality of gamma correction tables, and generates a gamma correction table. For this reason, the gamma correction table specified by the sheet identification information in the image captured and generated by the imaging device is updated, so that an appropriate gamma correction table among the plurality of gamma correction tables can be updated.

  A calibration program according to the present invention is a calibration program executed by an image forming apparatus that generates a sheet by printing a chart including a plurality of color patches, and corrects gradation characteristics of the image forming apparatus. Table generating means for generating a gamma correction table, table updating means for updating the gamma correction table, and identification information for identifying a gamma correction table applied when printing the chart among the plurality of gamma correction tables. The image forming apparatus is caused to function as a sheet printing unit that prints the applied sheet, and the table generation unit is configured to display an image generated by photographing the sheet and a reference chart corresponding to the chart at the same time by a photographing device. The chart and the referrer Generating a gamma correction table for correcting the tone characteristics of the image forming apparatus to the tone characteristics according to the reference chart based on the color values of the patches of the activity chart, and the table updating means The gamma correction table specified by the identification information of the sheet is updated to the gamma correction table generated by the table generating means.

  With this configuration, the image forming apparatus that executes the calibration program of the present invention prints a sheet to which identification information for identifying a gamma correction table applied when printing a chart among a plurality of gamma correction tables is added. Since the gamma correction table specified by the sheet identification information in the image captured and generated by the imaging device is updated to generate the gamma correction table, the appropriate gamma correction table is updated among the plurality of gamma correction tables. can do.

  The calibration system, calibration method, image forming apparatus, and calibration program of the present invention can update an appropriate gamma correction table among a plurality of gamma correction tables.

1 is a block diagram of a calibration system according to an embodiment of the present invention. It is a block diagram of the smart phone shown in FIG. FIG. 2 is a block diagram of the MFP shown in FIG. 1. It is a figure which shows the principle of the gamma correction table shown in FIG. (A) It is a figure which shows an example of the test sheet printed based on the chart image data shown in FIG. (B) It is a figure which shows an example of the reference sheet used with the test sheet shown to Fig.5 (a). It is a figure which shows an example of the corresponding relationship information shown in FIG. It is a flowchart of the method of the calibration in the calibration system shown in FIG. It is a flowchart of the image analysis process shown in FIG. 8 is a flowchart of a gamma correction table generation process shown in FIG. It is a figure which shows an example of the relational expression produced | generated in the gamma correction table production | generation process shown in FIG. FIG. 4 is a diagram illustrating an example of gradation characteristics of the MFP illustrated in FIG. 3. It is a block diagram of the smart phone shown in FIG. 1, Comprising: It is a figure which shows the example different from the example shown in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of the calibration system according to the present embodiment will be described.

  FIG. 1 is a block diagram of a calibration system 10 according to the present embodiment.

  As shown in FIG. 1, the calibration system 10 includes a smartphone 20 as an imaging device and an MFP (Multifunction Peripheral) 30 as an image forming apparatus. The smartphone 20 and the MFP 30 are configured to be able to communicate with each other. Here, the smartphone 20 and the MFP 30 may be able to communicate with each other via a network 11 such as a LAN (Local Area Network) or the Internet, or a USB (Universal Serial Bus) cable or the like without going through the network 11. It may be possible to communicate directly with each other via a communication cable.

  FIG. 2 is a block diagram of the smartphone 20.

  As shown in FIG. 2, the smartphone 20 includes an operation unit 21 that is an input device such as buttons for inputting various operations, and a display unit that is a display device such as an LCD (Liquid Crystal Display) that displays various information. 22, a camera 23, a communication unit 24 that is a communication device that communicates with an external device via a network 11 (see FIG. 1) or a communication cable, and an HDD (Hard Disk Drive) that stores various data. A storage unit 25 that is a non-volatile storage device, and a control unit 26 that controls the entire smartphone 20.

  The control unit 26 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory) storing various data, and a RAM (Random Access Memory) used as a work area of the CPU. The CPU executes a program stored in the ROM or the storage unit 25.

  FIG. 3 is a block diagram of the MFP 30.

  As shown in FIG. 3, the MFP 30 includes an operation unit 31 that is an input device such as buttons for inputting various operations, a display unit 32 that is a display device such as an LCD that displays various information, and an image from a document. Fax communication is performed via a communication line such as a public telephone line such as a scanner 33 which is a reading device, a printer 34 which is a printing device which performs printing on a recording medium such as paper, and an external facsimile apparatus (not shown). A fax communication unit 35 that is a fax device, a communication unit 36 that is a communication device that communicates with an external device via the network 11 (see FIG. 1) or a communication cable, and an EEPROM (Electrically) that stores various data. Erasable Programmable Read Only Memory ry), a storage unit 37 that is a nonvolatile storage device such as an HDD, and a control unit 38 that controls the entire MFP 30.

  The storage unit 37 stores a calibration program 37 a for correcting the gradation characteristics of the printer 34. The calibration program 37a may be installed in the MFP 30 at the manufacturing stage of the MFP 30, or may be additionally installed in the MFP 30 from a storage medium such as an SD card or a USB (Universal Serial Bus) memory, or on the network 11. To the MFP 30 may be additionally installed.

  In addition, the storage unit 37 stores a plurality of gamma correction tables (LUT: Lookup Table) 37 b for correcting the gradation characteristics of the MFP 30.

  FIG. 4 is a diagram showing the principle of the gamma correction table 37b.

  As shown in FIG. 4, even if the actual gradation characteristic 41 of the printer 34 deviates from the expected gradation characteristic 42, by applying the gamma correction table 37b to the actual gradation characteristic 41 of the printer 34, The expected gradation characteristic 42 can be realized.

  As shown in FIG. 3, the storage unit 37 includes chart image data 37c as image data of a chart including a plurality of color patches, and a reference chart in which chromaticity values independent of devices are known for the patches. Reference chromaticity value information 37d indicating the chromaticity value of each patch is stored.

  In the following description, the chromaticity value independent of the device is described as an XYZ value.

  FIG. 5A is a diagram illustrating an example of a test sheet 50 as a sheet printed based on the chart image data 37c. FIG. 5B is a diagram illustrating an example of a reference sheet 60 that is used together with the test sheet 50.

  As shown in FIG. 5, the test sheet 50 includes a test chart 51 as a chart including a plurality of color patches 51 a, a frame line 52 indicating a position where the reference sheet 60 is disposed, and a frame line surrounding the test chart 51. 53 and a frame line 52 and a frame line 54 surrounding the frame line 53 are printed by the printer 34. The test sheet 50 is printed with a graphic 55 for identifying a screen to be described later.

  In the reference sheet 60, a reference chart 61 including a plurality of color patches 61a is drawn. The reference chart 61 is the same as the test chart 51 that is horizontally inverted, and is a chart corresponding to the test chart 51. Since the reference chart 61 is not printed by the printer 34, the color value is superior to the test chart 51 in terms of accuracy.

  As shown in FIG. 3, the storage unit 37 includes a plurality of screens 37e applied to the image data to reproduce halftones, and correspondence information 37f indicating the correspondence between the screens 37e and the gamma correction table 37b. Is remembered.

  FIG. 6 is a diagram illustrating an example of the correspondence relationship information 37f.

  As shown in FIG. 6, the correspondence information 37f includes a combination of the shape and number of figures 55, a screen number indicating a number for identifying the screen 37e, and a gamma correction table number indicating a number for identifying the gamma correction table 37b. This is information indicating the correspondence relationship. For example, in the test sheet 50 shown in FIG. 5A, since the figure 55 is three black squares (■), the screen 37e with the screen number 3 and the gamma correction table 37b with the gamma correction table number 1. It can be seen that this is a sheet printed with.

  The control unit 38 illustrated in FIG. 3 includes, for example, a CPU, a ROM that stores programs and various data, and a RAM as a main storage device that is used as a work area of the CPU. The CPU executes a program stored in the ROM.

  The control unit 38 executes a calibration program 37a stored in the storage unit 37, thereby applying any one of the plurality of screens 37e to the image data to reproduce halftones. The gamma correction table 37b corresponding to the screen 37e applied by the processing unit 38a is applied to correct the gradation characteristics of the MFP 30. The gamma correction table 38b is applied when printing the test chart 51 among the plurality of gamma correction tables 37b. A sheet printing unit 38c for printing the test sheet 50 provided with the graphic 55 as identification information for identifying the gamma correction table 37b, and a table generating unit 38d for generating a gamma correction table for correcting the gradation characteristics of the MFP 30. And gamma correction table 37b To function as new to the table updating means 38e.

  Next, a calibration method in the calibration system 10 will be described.

  FIG. 7 is a flowchart of a calibration method in the calibration system 10.

  As illustrated in FIG. 7, the user instructs the MFP 30 to generate the test sheet 50 via the operation unit 31 of the MFP 30 or the like. Therefore, the sheet printing unit 38c of the MFP 30 generates the test sheet 50 by printing the test chart 51 with the printer 34 (S101). Here, when the test chart 51 is printed, the screen processing unit 38a applies a specific screen 37e such as the screen 37e designated by the user among the plurality of screens 37e to the chart image data 37c. Reproduce halftone. Further, when the test chart 51 is printed, the gamma correction unit 38b applies the gamma correction table 37b corresponding in the correspondence information 37f to the screen 37e applied by the screen processing unit 38a to apply the gradation characteristics of the MFP 30. Correct. Then, the sheet printing unit 38c prints the test sheet 50 to which the graphic 55 for identifying the gamma correction table 37b applied at the time of printing the test chart 51 is given based on the correspondence information 37f.

  After the step of S101, the user photographs the test sheet 50 with the camera 23 of the smartphone 20 in a state where the reference sheet 60 is disposed within the frame line 52 of the test sheet 50 (S102). Therefore, the smartphone 20 simultaneously captures the test chart 51 and the reference chart 61 to generate an image, and transmits the generated image to the MFP 30.

  Next, the table generation unit 38d of the MFP 30 executes the image analysis process shown in FIG. 8 for analyzing the image transmitted from the smartphone 20 (S103).

  FIG. 8 is a flowchart of the image analysis process shown in FIG.

  As shown in FIG. 8, the table generating unit 38d acquires a color value for each patch of the chart in the image (S131).

  In the following description, the color values in the image are described as RGB values.

  The table generation means 38d recognizes the shape and number of figures 55 in the image after the process of S131 (S132).

  Next, the table generating unit 38d specifies the gamma correction table 37b and the screen 37e associated with the shape and number recognized in S132 in the correspondence information 37f (S133), and ends the image analysis processing shown in FIG. To do.

  As shown in FIG. 7, the table generation unit 38d executes the gamma correction table generation process shown in FIG. 9 after the image analysis process of S103 (S104).

  FIG. 9 is a flowchart of the gamma correction table generation process shown in FIG.

  As shown in FIG. 9, the table generating unit 38d obtains a relational expression as shown in FIG. 10 showing the correspondence between the RGB value of the patch 61a of the reference chart 61 in the image and the known XYZ value of the patch 61a. (S161). Here, the table generating unit 38d can acquire each known XYZ value of the patch 61a of the reference chart 61 based on the reference chromaticity value information 37d. Therefore, the table generating unit 38 d can recognize what XYZ values the RGB values in the image correspond to based on the plurality of patches 61 a of the reference chart 61.

  After the process of S161, the table generating unit 38d substitutes the RGB values of the patches 51a of the test chart 51 in the image into the relational expression acquired in S161, thereby outputting the output colors of the MFP 51 of the patches 51a of the test chart 51. XYZ values are acquired (S162). Therefore, the table generating unit 38d can acquire the gradation characteristic 71 of the MFP 30 as shown in FIG. The gradation characteristic 71 is a relationship between the color value in the chart image data 37c for the patch 51a of the test chart 51, that is, the input color value, and the XYZ value acquired in S162 for this patch 51a. Further, as shown in FIG. 11, the table generating unit 38d applies the color value in the chart image data 37c for the patch 51a of the test chart 51, that is, the input color value and the patch of the reference chart 61 corresponding to the patch 51a. Thus, the relationship 72 with the XYZ values set in the reference chromaticity value information 37d can be acquired.

  After the process of S162, the table generating unit 38d generates a gamma correction table for correcting the gradation characteristic 71 of the MFP 30 to the relationship 72 in the reference chart 61 as shown by the arrow in FIG. 11 (S163). That is, the table generating unit 38d references the gradation characteristic 71 of the MFP 30 based on the difference between the XYZ value of the output color of the patch 51a of the test chart 51 from the MFP 30 and the known XYZ value of the patch 61a of the reference chart 61. A gamma correction table for correcting the gradation characteristics along the chart 61 is generated.

  After completing the process of S163, the table generating unit 38d ends the gamma correction table generating process shown in FIG.

  As shown in FIG. 7, the table updating unit 38e uses the gamma correction table 37b specified in S133 among the plurality of gamma correction tables 37b on the storage unit 37 as the gamma correction table generated in the gamma correction table generation process in S104. Calibration is executed by updating the correction table (S105).

  As described above, the calibration system 10 uses the MFP 30 to add the test sheet 50 to which the graphic 55 for identifying the gamma correction table 37b applied when printing the test chart 51 among the plurality of gamma correction tables 37b. At the same time as printing (S101), the gamma correction table 37b specified in S133 is updated by the graphic 55 of the test sheet 50 in the image captured and generated by the smartphone 20 in S102 to generate the gamma correction table 37b (S105). Therefore, an appropriate gamma correction table 37b among the plurality of gamma correction tables 37b can be updated.

  Since the calibration system 10 employs the shape and number of figures 55 as the identification information of the gamma correction table 37b, the identification information from the image captured and generated by the smartphone 20 to generate the gamma correction table 37b. Therefore, it is possible to reduce the processing load of reading the identification information from the image.

  Note that the calibration system 10 may employ a combination other than the combination of the shape and the number of the figures 55 as the identification information of the gamma correction table 37b. For example, the calibration system 10 may express the identification information of the gamma correction table 37b with only one of the shape and the number of the figure 55.

  In the calibration system 10, since the identification information expressed by the combination of the shape and the number of the figure 55 is also information for identifying the screen 37e, not only the gamma correction table 37b applied when the test chart 51 is printed. The screen 37e can also be specified, and convenience can be improved.

  Note that the calibration system 10 may be configured to identify only the gamma correction table 37b without identifying the screen 37e by the combination of the shape and the number of figures 55.

  In the calibration system 10, since the MFP 30 includes the table generating unit 38d, the photographing device does not need to include the table generating unit. Therefore, the calibration system 10 does not need to use a highly functional device such as the smartphone 20 as an imaging device, and can use a general imaging device, thereby improving convenience. .

  In the calibration system 10 described above, the processes of S103 and S104 are executed by the MFP 30, but at least a part of the processes of S103 and S104 may be executed by the smartphone 20. For example, when all of the processes of S103 and S104 are executed in the smartphone 20, the control unit 26 of the smartphone 20 generates a gamma correction table for correcting the gradation characteristics of the MFP 30, as shown in FIG. The unit 26 a and the table transmission unit 26 b that transmits the gamma correction table generated by the table generation unit 26 a to the MFP 30. The table transmission unit 26 b also transmits information of the gamma correction table 37 b specified by the graphic 55 of the test sheet 50 in the image to the MFP 30. When all of the processes of S103 and S104 are executed in the smartphone 20, it is not necessary to provide the MFP 30 with a table generation unit, so that the processing load on the MFP 30 when updating the gamma correction table 37b can be suppressed.

  The image forming apparatus of the present invention is an MFP in the present embodiment, but may be an image forming apparatus other than the MFP. For example, the image forming apparatus of the present invention may be an image forming apparatus such as a printer dedicated machine, a copy dedicated machine, or a fax dedicated machine.

  The photographing device of the present invention is a smartphone in the present embodiment, but may be a photographing device other than a smartphone. For example, the photographing device of the present invention may be a photographing device such as a digital camera.

10 Calibration system 20 Smartphone (photographing device)
26a Table generation means 26b Table transmission means 30 MFP (image forming apparatus)
37a Calibration program 37b Gamma correction table 37c Chart image data (image data)
37e screen 38a screen processing means 38b gamma correction means 38c sheet printing means 38d table generation means 38e table updating means 41 gradation characteristics 42 gradation characteristics 50 test sheet (sheet)
51 Test chart (chart)
51a Patch 55 Figure (identification information)
61 Reference chart 61a Patch 71 Gradation characteristics

Claims (8)

A shooting device;
An image forming apparatus that generates a sheet by printing a chart including patches of a plurality of colors;
Table generating means for generating a gamma correction table for correcting the gradation characteristics of the image forming apparatus,
The image forming apparatus includes:
Table updating means for updating the gamma correction table;
Sheet printing means for printing the sheet with identification information for identifying a gamma correction table applied when printing the chart among the plurality of gamma correction tables;
The table generating means is configured to form the image based on color values of the chart and a patch of the reference chart in an image generated by simultaneously shooting the sheet and a reference chart corresponding to the chart by the imaging device. Generating the gamma correction table for correcting the gradation characteristics of the apparatus to the gradation characteristics according to the reference chart;
The table updating unit updates the gamma correction table specified by the identification information of the sheet in the image to the gamma correction table generated by the table generation unit.   The calibration system according to claim 1, wherein the sheet printing unit adds the identification information configured by at least one of a shape and a number of figures to the sheet. The image forming apparatus includes:
Screen processing means for reproducing halftones by applying any of a plurality of screens to image data;
Gamma correction means for correcting gradation characteristics of the image forming apparatus by applying the gamma correction table corresponding to the screen applied by the screen processing means,
The calibration system according to claim 1, wherein the identification information is information for identifying the screen applied when the chart is printed.   The calibration system according to claim 1, wherein the image forming apparatus includes the table generating unit. The photographing device is
The table generating means;
Table transmission means for transmitting the gamma correction table generated by the table generation means to the image forming apparatus,
4. The table transmission unit also transmits information on the gamma correction table specified by the identification information of the sheet in the image to the image forming apparatus. The described calibration system. A table generation step for generating a gamma correction table for correcting gradation characteristics of an image forming apparatus that generates a sheet by printing a chart including a plurality of color patches;
A table update step for updating the gamma correction table;
A sheet printing step of printing the sheet to which identification information for identifying a gamma correction table applied at the time of printing the chart among a plurality of the gamma correction tables is provided;
The table generating step is based on color values of the chart and a patch of the reference chart in an image generated by simultaneously shooting the sheet and a reference chart corresponding to the chart by a shooting device. Generating the gamma correction table for correcting the tone characteristics to the tone characteristics according to the reference chart,
The table updating step is a step of updating the gamma correction table specified by the identification information of the sheet in the image to the gamma correction table generated by the table generation step. Method. An image forming apparatus that generates a sheet by printing a chart including a plurality of color patches,
Table generating means for generating a gamma correction table for correcting gradation characteristics of the image forming apparatus;
Table updating means for updating the gamma correction table;
Sheet printing means for printing the sheet with identification information for identifying a gamma correction table applied when printing the chart among the plurality of gamma correction tables;
The table generating means is configured to generate the image forming apparatus based on color values of the chart and the reference chart patch in an image generated by simultaneously shooting the sheet and a reference chart corresponding to the chart by a shooting device Generating the gamma correction table for correcting the tone characteristics of the tone characteristics according to the reference chart,
The table update unit updates the gamma correction table specified by the identification information of the sheet in the image to the gamma correction table generated by the table generation unit. A calibration program executed by an image forming apparatus that generates a sheet by printing a chart including patches of a plurality of colors,
Table generating means for generating a gamma correction table for correcting gradation characteristics of the image forming apparatus;
Table updating means for updating the gamma correction table; and
Causing the image forming apparatus to function as a sheet printing unit that prints the sheet provided with identification information for identifying a gamma correction table to be applied when printing the chart among the plurality of gamma correction tables;
The table generating means is configured to generate the image forming apparatus based on color values of the chart and the reference chart patch in an image generated by simultaneously shooting the sheet and a reference chart corresponding to the chart by a shooting device. Generating the gamma correction table for correcting the tone characteristics of the tone characteristics according to the reference chart,
The table update means updates the gamma correction table specified by the identification information of the sheet in the image to the gamma correction table generated by the table generation means.