Image forming device, control method thereof, and storage medium

Abstract

The present disclosure relates to an image forming apparatus, a control method thereof, and a storage medium. The purpose is to match the texture and chromaticity of printed materials between different printing devices. To achieve this purpose, the printed material output by the destination device is scanned, and it is determined whether a specific area in the image data obtained by scanning is an area printed in K color or an area printed in CMY mixed color on the printed material. Then, based on the determination result, the printing parameters are determined.

Description

Technical Field

[0001] The technology disclosed herein relates to a color adjustment technology in an image forming apparatus that prints digital image data. Background Art

[0002] In the case of replacing an image forming apparatus capable of so-called full-color printing with another one, or in the case of purchasing a new image forming apparatus, it is necessary to maintain the tint of the printed material of the image forming apparatus before replacement or the existing one in the replaced or purchased image forming apparatus as well. Here, the printing device as the destination (such as the image forming apparatus before replacement and the existing image forming apparatus) is referred to as a "destination device", and the printing device to be adjusted (such as the replaced image forming apparatus and the newly purchased image forming apparatus) is referred to as an "adjustment device". Then, conventionally, a technology has been proposed that matches the tint of printed materials between different devices by adjusting color profiles. For example, Japanese Patent Publication No. 2004-153667 discloses a color proofing system that matches the tint of printed materials of an inexpensive color printer as an adjustment device with the tint of printed materials of a large-size proofreading device as a destination device.

[0003] In the case where the color of an object (text, graphic, photo, etc.) within a print target image is, for example, gray, the color may be represented by CMYK (print color) or K color. However, the texture of the finished printed material differs depending on whether the color is represented by the four mixed colors of CMYK or K color (the number configuration of the color components of gray). In addition, in the destination device, the above configuration of the number of color components may have changed for each object attribute (such as text, graphic, and image). That is, in the case where not only the chromaticity but also the texture is matched in the adjustment device, it is necessary to determine which configuration of the number of color components is used when representing a certain color in the destination device, whether the configuration has been changed for each object attribute, etc. In this regard, using the conventional technology of matching the chromaticity of printed materials between different devices by adjusting the color profile, it is impossible to match the chromaticity and texture at the same time. Summary of the invention

[0004] The image forming device according to the present disclosure includes: a scanning unit configured to scan a printed material; a first determining unit configured to determine whether a specific area in image data obtained by scanning is an area printed in K color or an area printed in CMY mixed colors on the printed material; and a second determining unit configured to determine printing parameters based on a result determined by the first determining unit.

[0005] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a diagram showing an example of a configuration of a printing system;

[0007] Figure 2 is a diagram showing an example of a configuration of a printer image processing unit;

[0008] Figure 3A is a diagram showing a cube of a three-dimensional color space, Figure 3B is a diagram showing an example of a LUT for converting RGB into L*a*b, and Figure 3C is a diagram showing an example of a LUT for converting RGB into CMYK;

[0009] Figure 4A and Figure 4B Each is a diagram showing an example of a print setting screen;

[0010] Figure 5 is a diagram for explaining a rough flow at the time of creation of a color conversion LUT according to the first embodiment;

[0011] Fig. 6A is a diagram showing an example of a printer characteristics chart, and Figure 6B is a diagram showing an example of a target graph;

[0012] Fig. 7A is a diagram showing an example of a color conversion LUT for mixed grays, and Figure 7B is a diagram showing an example of a color conversion LUT for non-mixed gray;

[0013] Figure 8 is a flowchart showing a process flow of creating a color conversion LUT according to the number configuration of the color components of gray in the destination device;

[0014] Fig. 9 is a diagram explaining a process of creating a color conversion LUT for mixed grays;

[0015] Fig.10 is a flowchart showing the flow of preference registration processing related to a color matching method;

[0016] Fig.11 is a diagram showing an example of a preference registration screen;

[0017] Fig.12 is a diagram showing an example of an adjustment / maintenance screen;

[0018] FIG. 13A to FIG. 13C Each is a diagram showing an example of a print job in which an instruction to print a target chart is given for each object attribute;

[0019] Fig.14 is a flowchart showing the flow of a process of creating a color conversion LUT according to Modification Example 1;

[0020] FIG. 15A to FIG. 15D Each is a diagram showing an example of a color patch quantity setting screen;

[0021] Fig.16 is a diagram showing an example of a property check graph; and

[0022] Fig.17 : is a flowchart showing the flow of a process of creating a color conversion LUT according to Modification Example 3. DETAILED DESCRIPTION

[0023] Hereinafter, the present disclosure is explained in detail according to preferred embodiments with reference to the accompanying drawings. The configurations shown in the following embodiments are merely exemplary, and the present disclosure is not limited to the schematically shown configurations.

[0024] [First embodiment]

[0025] In this embodiment, an aspect is explained in which: first, the quantity configuration of the color components of gray is determined by scanning the gray patch on the printed material (color chart) output by the destination device and analyzing the obtained image data; then, based on the determination result, the color conversion parameter of the adjustment device is determined so that the quantity configuration of the color components of gray becomes the same as the quantity configuration of the color components of gray of the destination device; and the printing process is performed by performing the color conversion process using the color conversion parameter in the adjustment device. As the printing device of this embodiment, an electrophotographic color image forming device that forms an image on a sheet in which toner images of four colors of CMYK are superimposed is envisioned, but the printing device may be an image forming device that adopts another printing method such as an inkjet method.

[0026] <Printing System Configuration>

[0027] Figure 1 1 is a diagram showing an example of a configuration of a printing system according to the present embodiment. An image forming apparatus 100 is connected to a PC (Personal Computer) 120 via a network 140. The network 140 is, for example, a LAN, a WAN, or the like.

[0028] In the PC 120, in addition to the application for executing document creation and form creation, a print driver is installed. In the case of printing digital image data created by any application, the user converts the digital image data into PDL (page description language) data through the printer driver, and transmits the print job including the PDL data to the image forming apparatus 100 via the network 140. In addition, the monitor 130 is connected to the PC 120, and the monitor 130 displays digital image data created by various applications, etc.

[0029] As the image forming apparatus 100, there is mentioned, for example, a device such as a digital copying machine, a laser printer for which a scanner is separately prepared, and a facsimile machine. The image forming apparatus 100 includes a CPU 101, a ROM 102, a RAM 103, an HDD 104, a display unit 105, an operation unit 106, a scanner unit 107, a scanner image processing unit 108, a network I / F 109, a printer image processing unit 110, a printer unit 111, a system bus 112, a monitor 113, and a computer 114. Hereinafter, each unit of the image forming apparatus 100 is explained.

[0030] The CPU 101 is a central processing unit that performs control of the entire device, operation processing, etc. based on the program stored in the ROM 102 and performs each image processing that will be described later. The ROM 102 is a read-only memory and a storage area for a system activation program, a program for controlling the scanner unit 107 and the printer unit 111, character data, character code information, etc. The RAM 103 is a random access memory and is used in the case where the program and data stored in the ROM 102 are loaded by the CPU 101 and executed for each of various processing. In addition, the RAM 103 is used as a data storage area for image files received from the scanner unit 107 or the network I / F 109. The HDD 104 is composed of, for example, a hard disk, etc., and is used to store the results of the processing performed by the CPU 101, each information file, and various data of the print target image and the chart image. In addition, in the case where the CPU 101 performs processing, the HDD 104 is also used as a work area. The display unit 105 displays a screen on a liquid crystal display, for example, and is used to display the setting state of the device, the processing of each unit of the device (such as the CPU 101), an error state, etc. The operation unit 106 is a unit through which a user inputs various instructions for executing various processes, changing settings, etc. Information about the user instructions input via the operation unit 106 is stored in the RAM 103 and is used in the case of executing the processing of the CPU 101. The scanner unit 107 irradiates a document placed on a document table not schematically shown, converts the reflected light into an electric signal using a CCD including a color filter of RGB, etc., and obtains RGB image data corresponding to the document. In addition, the scanner unit 107 transmits this RGB image data to the scanner image processing unit 108. The scanner image processing unit 108 performs image processing such as shading processing on the RGB image data obtained by the scanner unit 107. The network I / F 109 is an interface for connecting the image forming apparatus 100 to a network such as an intranet. Via this network I / F 109, a print job is input from the PC 120 through the network. The printer image processing unit 110 performs image processing suitable for the printer unit 111 on the RGB image data on which the image processing has been performed by the scanner image processing unit 108 or the PDL data in the print job received via the network I / F 109. The printer unit 111 forms an image including the CMYK image data of four colors of cyan, magenta, yellow, and black, which has been processed by the printer image processing unit 110, by performing each electrophotographic process of exposure, latent image formation, development, transfer, and fixing. The system bus 112 connects each of the above units to each other and serves as a data path between each unit.

[0031] <Details of Image Processing Unit>

[0032] Figure 2 2 is a block diagram showing the internal configuration of the printer image processing unit 110 according to the present embodiment (i.e., functions related to image processing for generating print data from PDL data within print data). The printer image processing unit 110 has a rendering unit 201, a color conversion unit 202, a tone correction unit (gamma correction unit) 203, a quantization unit 204, and a color conversion LUT creation unit 205. "LUT" is an abbreviation for a lookup table and stores input values ​​and output values ​​in association with each other at a plurality of discrete points (corresponding to grid points, which will be described later) within a color space. Each functional block is explained below.

[0033] The rendering unit 201 interprets the PDL data included in the print job received from the PC 110 with a PDL interpreter, and converts the PDL data into bitmap data for printing. This bitmap data has multiple color components per pixel. Here, in the case of the present embodiment, multiple color components refer to independent color components of R (red), G (green) and B (blue) defined in the sRGB color space. The bitmap data has a value represented by 8 bits (256 tones) for each color component for each pixel. That is, the bitmap data of the present embodiment is image data (RGB image data) in which each pixel has an RGB value. In addition, in rendering, information (attribute information) indicating the object attributes of each pixel in the print target image data is also generated. This attribute information indicates which object each pixel belongs to and stores, for example, a value identifying the object type (such as text, graphics, and images).

[0034] The color conversion unit 202 performs processing (color conversion processing) to convert the RGB image data input from the rendering unit 201 into image data (CMYK image data) in which each pixel has a CMYK value by using the color conversion LUT 206. Thereby, the color reproduction area of ​​the monitor 130 matches the color reproduction area of ​​the printer unit 111. In the color conversion LUT 206 that converts a color expressed in an RGB color space into a color expressed in a CMYK color space, the color reproduction area is determined based on the value of 8-bit data (0 to 255) of each RGB. Figure 3A The coordinates in the cube in the three-dimensional color space shown in . The coordinates of the eight vertices of the cube represent each of R, G, B, Y, M, C, K, and W, and in the case of R=G=B (gray, in which the amounts of R, G, and B are equal), the coordinates of the diagonal line (gray axis) of the cube connecting K and W are referenced. In addition, the color conversion LUT 206 has 16×16×16 grid points specified by the RGB values ​​of the input image data, and stores the CMYK values ​​corresponding to these grid points as output values. For example, in Figure 3BIn the color conversion LUT shown, a CMYK value (0, 255, 255, 0) is stored as grid point data corresponding to an RGB value (255, 0, 0). When an RGB value not defined by a grid point is input, a CMYK value corresponding to the input RGB value is obtained by interpolation using the CMYK value associated with the RGB value defined by the grid point.

[0035] The tone correction unit 203 performs tone correction processing by using a tone correction LUT (not schematically shown) prepared in advance for bitmap data in the CMYK space obtained by the color conversion processing so that a target output density can be obtained in the print processing of the printer unit 111 .

[0036] The quantization unit 204 performs quantization processing (also referred to as "halftone processing") on the bitmap data of each color plane of CMYK after the tone correction processing. Thus, halftone image data is obtained by converting into a halftone dot pattern having N values ​​(N is a natural number not less than 2), wherein the halftone within the print target image is represented by the regional grayscale. As the halftone processing, various methods have been proposed, such as a density pattern method, a system dithering method, and an error diffusion method, but any method can be used. The obtained halftone image data is sent to the printer unit 111 as print data.

[0037] The color conversion LUT creation unit 205 creates a color conversion LUT 206 that the color conversion unit 202 refers to in the color conversion process. The details of the color conversion LUT creation process will be described later.

[0038] In the present embodiment, such a configuration is adopted that all printer image processing is performed within the image forming apparatus 100, but the technology of the present disclosure is not limited to such a configuration. For example, such a system configuration may be accepted in which a part of processing such as color conversion processing and quantization processing is performed by the PC 120 that transmits the print job. Alternatively, such a configuration may be accepted in which the image forming apparatus 100 and the PC 120 perform processing in cooperation with each other in a distributed manner.

[0039] <Print Function Settings>

[0040] Next, the print function setting in the image forming apparatus 100 is explained. Figure 4A 1 is a diagram showing an example of a user interface screen for function setting (hereinafter, described as a “print setting screen”) displayed on the display unit 105 of the image forming apparatus 100. Figure 4AIn the "Setting Item" field in the "Item List" on the print setting screen shown, "Color Matching Method" is displayed as an item name of a function that can be specified as an option. Here, the color matching method is a function of setting a color gamut compression method in the matching process. The color reproduction range (color gamut) of different devices is different, so a matching process for matching the color gamut becomes necessary. In the matching process of matching the color gamut from an input device with a wide color gamut (such as a display) to an output device with a narrow color gamut (such as a printer), color gamut compression is performed. Then, in the "Setting Contents" field on the right side of the "Setting Item", a matching mode can be specified for each object attribute. There are the following three matching modes prepared as default.

[0041] Chroma Priority: A mode in which priority is given to chroma to make the photo look more desirable

[0042] Minimum Color Difference: A mode in which the colors of the original image are accurately output within the color reproduction range of the printer

[0043] Saturation Priority: A mode in which overall vivid color rendering (saturation) is prioritized.

[0044] The user can perform various function settings, including settings related to the color matching method, via a similar UI screen provided by an application installed in the PC 120 or a printer driver at the time of printing.

[0045] <Overview of Color Conversion LUT Creation Process>

[0046] Next, refer to Figure 5 A rough flow of color conversion LUT creation in the color conversion LUT creation unit 205 is explained. Figure 5 The following shows the transition of the UI screen (adjustment / maintenance screen) when color adjustment is performed between devices. Figure 5 Explains the outline of color conversion LUT creation.

[0047] <<Adjusting the acquisition of the color characteristics of the device>>

[0048] First, the user opens the initial screen 501 of the adjustment / maintenance screen by using the operation unit 106 of the image forming apparatus 100 as the adjustment device. Next, the user brings the state of the chart output screen 502 by operating the initial screen 501, and gives an instruction to print a color chart composed of color patches of various colors (hereinafter referred to as a "printer characteristic chart") to obtain color characteristics in the printer unit 111. Based on the print instruction, the printer unit 111 performs a print process by using the image data of the printer characteristic chart prepared in advance. Fig. 6A6 is a diagram showing an example of a printer characteristics chart. The printer characteristics chart is composed of a plurality of color blocks 601 corresponding to values ​​obtained by sampling 8-bit RGB signal values ​​(0 to 255) at regular intervals. Here, in the present embodiment, in order to suppress the difference in color adjustment accuracy due to the number configuration of the color components of the grayscale, two color characteristics are acquired by performing two color conversion processes on the image data of the printer characteristics chart respectively and printing and outputting them respectively. At this time, in the first color conversion process, by using the color conversion LUT for mixed gray (see Fig. 7A ), color conversion is performed on gray patches having signal values ​​R=G=B among the patches in the printer characteristic chart. Thus, color characteristics in the case where gray is expressed by four colors of CMYK (CMY color mixed gray) can be obtained. In another color conversion process, by using a color conversion LUT for non-mixed gray (see Figure 7B ), color conversion is performed on the gray color block having the signal value R=G=B. Thus, the color characteristics in the case where gray is represented by K color (non-mixed gray) can be obtained.

[0049] Then, in the case where the above-mentioned two printer characteristics charts are printed by the printer unit 111, the user brings the UI screen into the state of the chart reading screen 503 and gives instructions to read the two printed and output printer characteristics charts respectively after setting them on a document table (not shown schematically). Based on the reading instruction, the scanner unit 107 generates RGB image data represented in the RGB color space by optically reading the printer characteristics chart set on the document table. The generated RGB image data is sent to the scanner image processing unit 108. The scanner image processing unit 108 first performs processing to extract the average RGB value for each color block on the chart for each RGB image data of the two printer characteristics charts. Then, the scanner image processing unit 108 converts the RGB value into the L*a*b* value by using a scanning color conversion LUT (see Figure 3C ) to obtain the above two color characteristics. Information on the two color characteristics thus obtained is stored in RAM 103.

[0050] <<Acquisition of color characteristics of the destination device>>

[0051] Next, the user causes the UI screen to enter the state of the chart reading screen 504, and gives an instruction to read a colorimetric chart (hereinafter referred to as a "target chart") pre-printed and output by another image forming apparatus (not schematically shown) as a destination device after setting a target chart on a document table (not schematically shown). Based on the reading instruction, the scanner unit 107 generates RGB image data represented in an RGB color space by optically reading the target chart set on the document table. The generated RGB image data is sent to the scanner image processing unit 108, and a process of acquiring color characteristics in another image forming apparatus is performed. Here, the target chart is explained. Figure 6B 61 is a diagram showing an example of a target chart. The target chart consists of a first color block area 611 for checking the configuration of the quantity of color components of gray and a second color block area for obtaining normal color characteristics. In the first color block area 611, halftone gray color blocks corresponding to each of the text attribute, graphic attribute, and image attribute are arranged. The color blocks of the image attribute are defined by JPEG, TIFF, etc., the color blocks of the graphic attribute are defined by a rectangular diagram that specifies the coordinate position, width, and height of the rectangle, and the color blocks of the text attribute are defined by a character diagram that specifies the shape, size, etc. of the font. In the second color block area 612, the color blocks corresponding to the text attribute, graphic attribute, and image attribute are arranged. Fig. 6A As in the printer characteristic chart in FIG. 1 , color patches corresponding to each color and to which, for example, image attributes are attached are arranged. For the second color patch area 612 of the two color patch areas, the same processing as in the case of the above-mentioned printer characteristic chart is performed. That is, by extracting the average RGB value of each color patch from the RGB image data corresponding to the second color patch area 612 and converting the average RGB value into an L*a*b* value, the color characteristics in the destination device are acquired and stored in the RAM 103. On the other hand, in the first color patch area 611, a predetermined analysis process is performed on the gray patches of each object attribute in the area, and it is determined whether each gray patch is expressed as a mixed gray or a non-mixed gray.

[0052] <<Configure creating a color conversion LUT based on the number of gray color components>>

[0053] In the case of acquiring information about the color characteristics in the adjustment device and the color characteristics in the destination device as described above, a color conversion LUT is created for each object attribute according to the configuration of the number of color components of gray. The data of the created color conversion LUT is stored in the RAM 103, and at the same time, the state of the UI screen is changed to the notification screen 505 and a message that the creation of the color conversion LUT for each object attribute is completed is displayed. The details of the process of creating the color conversion LUT according to the configuration of the number of color components of gray will be described later.

[0054] The above is a rough flow until the color conversion LUT 206 is created in the color conversion LUT creation unit 205 according to the present embodiment.

[0055] Generally speaking, in many cases, for each object attribute (such as text, graphics, and images), the quantity configuration of the gray color component is switched to another, so in this embodiment, it is assumed that a color conversion LUT is created for each object attribute. However, it is not necessary to create a color conversion LUT for each object attribute.

[0056] In addition, the color (average RGB value) of each color block of the printer characteristic chart and the target chart can also be acquired by using, for example, a color measuring device. In addition, it is not necessarily required to acquire the color characteristics of the adjustment device every time. For example, in the case where the time elapsed since the last acquisition is short, in the case where it is desired to suppress the consumption of color materials due to color adjustment, in the case where it is desired to save time and effort spent on color adjustment, etc., the information at the time of the last acquisition can also be stored and reused. In the case of performing this operation, for example, a skip button (not schematically shown) is provided in advance within the UI screen and in the case where the skip button is pressed, it is sufficient to read and use the information about the color characteristics (or the initial color characteristics at the time of shipment) that was acquired in advance and stored in the HDD 104.

[0057] In addition, in the present embodiment, both color characteristics for mixed gray and for non-mixed gray are acquired for the adjustment device, but this is not essential. In the case where it is sufficient for the configuration of the number of color components of gray to match the configuration of the number of color components of gray of the destination device, such a configuration of acquiring only the color characteristics for mixed gray may be acceptable.

[0058] <Details of the color conversion LUT creation process configured according to the number of gray color components>

[0059] Next, details of a process of creating a color conversion LUT according to the quantity configuration of the color components of gray for each object attribute by acquiring the quantity configuration of the color components of gray in the destination device for each of the text attribute, the graphic attribute, and the image attribute are explained. Figure 8 : is a flowchart showing the flow of a process of creating a color conversion LUT according to the configuration of the number of color components of gray in a destination device according to the present embodiment. Figure 8 A series of processing shown in the flowchart of FIG. 1 is realized by the CPU 101 loading a predetermined program from the ROM 102 onto the RAM 103 and executing the program. In the following explanation, symbol "S" represents a step.

[0060] First, at S801, the saturation counter is initialized ("0" is set to the count value Cnt). Here, the saturation counter is used to count the number of times the saturation C specified by the L*a*b* value found for each pixel (see S803 described later) exceeds a predetermined threshold value C_th.

[0061] At S802 , the object attribute of interest is determined among text attributes, graphic attributes, and image attributes, and a partial image (gray block image) corresponding to the gray block of the determined object attribute is acquired from the first block area of ​​the target chart.

[0062] At S803, the L*a*b* value of the pixel of interest in the gray patch image obtained at S802 is derived. The color of each pixel in the gray patch image has an RGB value. Then, by using a scanning color conversion LUT (see Figure 3C ) to convert RGB values ​​into L*a*b* values.

[0063] At S804, based on the L*a*b* value derived at S803, it is determined whether the color of the pixel of interest is a color. Specifically, according to the a* value and the b* value in the L*a*b* value, the saturation C is found by using the following formula (1), and when the found saturation C exceeds the threshold value C_th, it is determined that the color is a color.

[0064] [Mathematical formula 1]

[0065] Saturation C = √a* 2 +b* 2 ...Formula (1)

[0066] Here, it is sufficient to set the threshold value C_th to a saturation value at a level at which the color can be said to be substantially colored, for example, about C_th = 20. In the case where the color of the pixel of interest is determined to be colored as a result of the above-mentioned threshold processing, the process proceeds to S805. Then, at S805, the above-mentioned count value Cnt of the saturation counter is incremented (+1). On the other hand, in the case where the color of the pixel of interest is determined not to be colored (determined to be non-colored) as a result of the above-mentioned threshold processing, the process skips S805 and proceeds to S806.

[0067] At S806, it is determined whether the determination process of whether the color is a color is completed for all pixels in the gray block image acquired at S802. In the case where the determination process is not completed, the process returns to S803, and the next pixel of interest is determined from the unprocessed pixels, and the same process is determined. On the other hand, in the case where the determination process is completed, the process proceeds to S807.

[0068] At S807, based on the count value Cnt of the above-mentioned saturation counter, it is determined whether the gray patch image obtained at S802 is printed in mixed gray or non-mixed gray. Specifically, in the case where the count value Cnt at the current time point is greater than or equal to the preset threshold value Cnt_th, it is determined that the gray patch image is printed in mixed gray, and when the count value Cnt is less than the threshold value, it is determined that the gray patch image is printed in non-mixed gray. Here, as the threshold value Cnt_th, a value is set so that the ratio of color pixels to all pixels constituting the gray patch image is about 10% to 20%. For example, in the case where the resolution of the gray patch image is 600dpi and the size is 1cm×1cm, the total number of pixels is 55,696, so in this case, it is sufficient to set the threshold value Cnt_th to about 5,500 to 11,000. In the case where the count value Cnt of the saturation counter is greater than or equal to the threshold value Cnt_th, pixels with high saturation are included in the gray patch image at a predetermined ratio, so it can be determined that the number configuration of the color components of the gray is mixed gray. On the other hand, when the count value Cnt is less than the threshold value Cnt_th, not many pixels with high saturation are included in the gray block image, so it can be determined that the number configuration of the color components of the gray is non-mixed gray. When the result of the above threshold processing indicates that the count value Cnt of the saturation counter is greater than or equal to the threshold, the process proceeds to S808, and when the count value Cnt is less than the threshold, the process proceeds to S809.

[0069] At S808, a color conversion LUT for mixed gray is created. In addition, at S809, a color conversion LUT for non-mixed gray is created. The specific creation methods of these color conversion LUTs will be described later.

[0070] Then, at S810, it is determined whether the creation of the color conversion LUT configured according to the number of gray color components has been completed for all object attributes. If the creation has not been completed, the process returns to S801, and the next object attribute of interest is determined and the process is continued, and if the creation is completed, this process is terminated.

[0071] The above is the content of the color conversion LUT creation processing according to the configuration of the number of color components of gray according to the present embodiment. The method for determining the configuration of the number of color components of gray is not limited to the method based on the saturation of the pixels constituting the gray patch image. For example, the difference between the channels can also be found from the RGB values ​​of the pixels constituting the gray patch image, and the number configuration of the color components of gray can be determined to be mixed gray when the number of pixels whose difference is found to be greater than or equal to a predetermined threshold is greater than or equal to a predetermined number, and it can be determined to be non-mixed gray when the number is less than a predetermined number. In addition, instead of finding the average value, median, standard deviation, etc. of each of the R component, G component, and B component in the entire gray patch image for each pixel, the determination can be performed based on the magnitude of the difference between its channels.

[0072] <How to create a color conversion LUT>

[0073] Next, the details of the creation method of the color conversion LUT at S808 and S809 are explained. The creation process itself is common to S808 and S809, so the following explanation is given by taking the case of creating a color conversion LUT for mixed gray as an example. Fig. 9 This is a diagram that explains the creation process of a color conversion LUT for mixed grays. Fig. 9 Give an explanation.

[0074] First, data of the color characteristics of the adjustment device and the color characteristics of the destination device are acquired from the RAM 103. The color characteristics of the adjustment device at this time are the color characteristics obtained based on the output result of the printer characteristic chart that performs color conversion by the color conversion LUT for mixed gray, of the two color characteristics described above. Fig. 9 901 shows the color characteristics of the destination device and table 902 shows the color characteristics of the adjustment device. In the following explanation, the RGB values ​​in table 901 are described as "T_RGB", and the corresponding L*a*b* values ​​are described as "T-Lab", and the RGB values ​​in table 902 are described as "P_RGB", and the corresponding L*a*b* values ​​are described as "P_Lab".

[0075] Next, from the P_Lab in the color characteristics of the adjustment device, a P_Lab having a value matching the value of T_Lab corresponding to T_RGB as the destination color is searched, and a P_RGB corresponding to the matching P_Lab is found through reverse calculation. Fig. 9In the example of , T_RGB is "204, 34, 0", T_Lab is "50, 50, 0" and P_Lab is "50, 50, 40", and as P_RGB corresponding to P_Lab, "221, 51, 0" is found. In the following explanation, P_RGB found by reverse calculations such as this is described as "T-P_RGB". In this way, the above-mentioned reverse calculation processing is performed for each of the RGB values ​​of the destination color, and a combination group of T_RBG and T-P_RGB is obtained. Then, a table consisting of the obtained combination groups is created and stored in RAM 103 as a color adjustment conversion table. Fig. 9 903 is an example of a color adjustment conversion table that puts together a combination of T_RGB and T-P_RGB. It can be seen that by performing color conversion processing in the adjustment device after converting T_RGB values ​​into T-P_RGB values ​​with reference to the color adjustment conversion table 903 thus obtained, a color matching the color reproduced in the destination device can be reproduced in the adjustment device.

[0076] Then, based on the above-mentioned color adjustment conversion table 903 and the configuration of the number of color components of gray in the destination device for the object attribute of interest, the previously described Fig. 7A The input RGB values ​​in the color conversion LUT for mixed gray shown in . For example, suppose that in the case of creating a color conversion LUT for image attributes, gray is represented by mixed gray in the destination device. In this case, referring to the color adjustment conversion table 903, the corresponding output value (CMYK) in the color conversion LUT 904 for mixed gray is found under the condition that T-P_RGB (here, "221, 51, 0") corresponding to T_RGB (here, "204, 34, 0") is used as an input value. Here, as the output value, CMYK = "0, 200, 200, 30" is found as a result. Then, in the color conversion LUT 904 for mixed gray, the input RGB value associated with the found output CMYK value is changed to the value of T_RGB (here, "204, 34, 0"). In this way, a new color conversion LUT 905 for mixed gray is obtained, in which T_RGB and CMYK are associated with each other. In the case where the gray is non-mixed gray, it is sufficient to perform the same processing with the color conversion LUT for non-mixed gray indicating the other color characteristic of the two color characteristics acquired for the adjustment device as a target. The color conversion LUT for mixed gray and the color conversion LUT for non-mixed gray on which modifications such as these have been performed are stored in the RAM 103 as the color conversion LUT 206 for which color adjustment with respect to the destination device has been completed.

[0077] There is a case where the range of reproducible colors (color gamut, color gamut) is different between the destination device and the adjustment device. In the case where the gamut of the destination device exceeds the gamut of the adjustment device, it is necessary to replace T_Lab with P_Lab, which is within the gamut of the adjustment device and is an approximate color. The method used for this is generally called gamut mapping. As a specific method, there is, for example, color difference minimum gamut mapping. The color difference (ΔE) mentioned here is expressed by the following formula (2) according to the CIE 1976Lab color system.

[0078] [Mathematical formula 2]

[0079] ΔE=√ΔL 2 +Δa 2 +Δb 2 ...Formula (2)

[0080] In the above formula (2), ΔL=L1-L2, Δa=a1-a2, and Δb=b1-b2. In addition, as a formula for finding color difference, in addition to the above formula (2), there are CIE1994 color difference formula, CIE 2000 color difference formula, etc. Color gamut mapping can be achieved by replacing with L*a*b* values ​​within the color gamut of the adjustment device and with the smallest color difference.

[0081] The above is the content of the creation processing of the color conversion LUT according to the present embodiment. The color conversion LUT for mixed gray and the color conversion LUT for non-mixed gray for which the color adjustment with respect to the destination device has been completed are stored in the HDD 104 or the like, and are added to the previously described color conversion LUT as an alternative item that can be set for each object attribute. Figure 4A In the setting of the color matching method on the print setting screen shown in . In the case where the user desires to match the impression (chromaticity) when reproducing gray with the impression (chromaticity) of a specific destination device, the user is only required to select a color conversion LUT for which color adjustment with respect to the destination device has been completed for each object attribute when printing the document (see Figure 4B ) and give a print instruction. In this case, it takes time and effort for the user to select a color conversion LUT for each object attribute each time a print instruction is given, and the user needs to acquire a certain level or higher of knowledge. Therefore, the user may also pre-store the color conversion LUT in a form such as "preference settings" or "default settings" after creating the color conversion LUT for each object attribute as described above. Thereby, the convenience of the user can be improved. Below, the specific process is explained by taking the case where the color conversion LUT is stored and registered as "preference settings" as an example.

[0082] <Preference registration process>

[0083] Fig.10: is a flowchart showing the flow of preference registration processing related to the color matching method. Fig.10 A series of processing shown in the flowchart of FIG. 1 is realized by the CPU 101 loading a predetermined program from the ROM 102 onto the RAM 103 and executing the program. In the following explanation, symbol "S" represents a step.

[0084] At S1001, the display unit 105 displays the following Fig.11 1004. A UI screen (preference registration screen) for preference registration processing shown in 1005 is displayed. At the next S1002, based on the setting value in the setting name field 1101 within the preference registration screen, information about the preference setting used as a basis is acquired based on the user instruction input via the operation unit 106. It is assumed that information about some preference settings (here, two settings: standard setting A and standard setting B) as shown in the following Table 1 is prepared in advance and stored in the RAM 103 or the like. Then, the user selects and specifies the name of a desired preference setting from the list displayed in a pull-down manner.

[0085] [Table 1]

[0086]

[0087] Fig.11 The example in FIG. 1 shows a state in which the user selects "Standard Setting A" and the word "<Edit>" is appended (automatically inserted) in the setting name field 1101. This indicates that the content of the selected preference setting (matching pattern for each object attribute) is described above. Figure 8 Possibility to replace color conversion LUTs created in the workflow.

[0088] At S1003, the item name of the function that the user can customize (here, "color matching method") is displayed in the "setting item" field in the "item list" within the preference registration screen. At subsequent S1004, the setting value corresponding to the item name displayed at S1003 is displayed in the "setting content" field. As the setting value displayed in this case, instead of the matching mode specified by the preference setting selected by the user, the setting value indicated in the previously described setting is preferentially displayed. Figure 8 As will be described later, for example, in the case where a color conversion LUT is not created for a specific object attribute, etc., the result shows a matching mode specified by the preference setting associated with the user selection. At S1005, based on the user instruction input via the operation unit 106, the preference setting having the setting value displayed in the "setting content" field is stored. For example, assuming that the user Fig.11In this case, the new preference setting is stored, in which the matching mode for each object attribute of images, graphics, and text has been changed to the content being displayed. At this time, the user can also store the new preference setting by entering a new name into the setting name field 1101 or store it by overwriting. In addition, the user can also change the matching mode for an arbitrary object attribute to an arbitrary content by selecting from the list in the "Setting content" field. In addition, by pressing the "Return to automatic generation of settings" button 1103 after performing the list selection, it is possible to return to the state indicated in the "Return to automatic generation of settings" field. Figure 8 1102. In addition, by pressing "Return to Preferences" 1104, it is possible to return to the contents specified by the information on the preferences related to the user selection acquired at S1002. Furthermore, by checking a check box 1105, it is possible to specify the preferences newly registered by pressing the "OK" button 1102 as the default settings in the color matching method.

[0089] As mentioned above, when users expect Figure 8 When printing is performed according to the destination device after creating a color conversion LUT in the process in , registering the color conversion LUT as a preference setting related to color matching, the user can easily specify the optimal color conversion LUT. Fig.11 The settings related to the above-described preference registration process are performed using a UI screen similar to a UI screen in , which is provided by an application or a printer driver installed in the PC 120.

[0090] <Modification Example 1>

[0091] In the above Figure 8 In the process in , the quantity configuration of the color components of gray is specified by printing a chart including gray patches for each object attribute in the destination device, and a color conversion LUT matching the quantity configuration of the color components of gray is created for each object attribute. However, the color conversion LUT for each object attribute is not always necessary. Therefore, one aspect is explained as a modified example 1, in which only the necessary color conversion LUT is created by outputting a dedicated chart for each object attribute in the destination device and determining whether the chromaticity is different between the object attributes based on the scanned image thereof.

[0092] First, refer to Fig.12 The rough flow until the color conversion LUT is created according to this modification example is explained. Figure 5 Like in Fig.12The following diagram shows the transition of the UI screen (adjustment / maintenance screen) displayed on the display unit 105 when creating the color conversion LUT. Figure 5 The common parts are explained first, and the differences are mainly explained below.

[0093] <<Adjusting the acquisition of the color characteristics of the device>>

[0094] First, by using the operation unit 106 of the adjustment device, the initial screen 1201 of the adjustment / maintenance screen is opened. The user brings the state of the chart output screen 1202 by operating the initial screen 1201, and gives an instruction to print a printer characteristic chart to obtain color characteristics in the printer unit 111. Based on the print instruction, the printer unit 111 prints the printer characteristic chart. At the time of printing, the color conversion LUT used in the color conversion process may be only the color conversion LUT for mixed gray, or it may also obtain two color characteristics by performing color conversion using the color conversion LUT for non-mixed gray in addition.

[0095] Then, in the case where the printer characteristics chart is printed and output by the printer unit 111, the user brings the UI screen to the state of the chart reading screen 1203, and gives an instruction to read the printer characteristics chart that is printed and output. Based on the reading instruction, the scanner unit 107 generates RGB image data by optically reading the printer characteristics chart set on the document table (not schematically shown). The generated RGB image data is sent to the scanner image processing unit 108, and information on the color characteristics in the adjustment device is acquired.

[0096] <<Acquisition of color characteristics of the destination device>>

[0097] Next, the user sequentially changes the UI screen to the state of the chart reading screens 1204 to 1206, and gives an instruction to read a target chart for each attribute that is pre-printed and output in the destination device. In this modified example, a target chart consisting of 9×9×9=729 color patches is used for each of the three attributes of the image attribute, the graphic attribute, and the text attribute. FIG. 13A to FIG. 13CEach shows an example of a print job input from PC 120 to a destination device when an instruction is given to print a target chart for each attribute. In the "job attribute definition part", the type of print medium (in the example, plain paper) of the first page of the physical page is specified, and in the case where the target chart is continuous across multiple pages, the second and subsequent pages of the physical page are also specified, but it is expected that the print medium is common to the pages. The physical page is a concept paired with the concept of a logical page indicating an image formed on the memory space of the printing device, and refers to a page of a print medium on which an image of the logical page is formed. One page of the physical page has the same meaning as one type of print medium. In addition, in the "drawing information definition part", the object attributes when drawing each color block are specified. For example, in Fig.13A In the case of a print job in , "Image" is specified, and in this case, each patch is configured as JPEG, TIFF, etc. Fig. 13B In the case of a print job in which "Graphics" is specified, each color block is configured by a rectangular diagram (formed by specifying the width and height of a rectangle at a specified coordinate position). Fig. 13C In the case of a print job in which "text" is specified, each color block is configured by a character chart (formed by specifying the shape, size, etc. of a font). Based on a reading instruction from the user, the scanner unit 107 sequentially reads the above-mentioned target chart for each attribute output for each attribute, and generates RGB image data for each attribute. The generated RGB image data for each attribute is sent to the scanner image processing unit 108, and information on color characteristics for each attribute in the destination device is acquired.

[0098] <<Creating a Color Conversion LUT>>

[0099] In the case of acquiring information about the color characteristics in the adjustment device and the color characteristics for each attribute in the destination device as described above, a color conversion LUT is created according to its necessity. The data of the created color conversion LUT is stored in the RAM 103, and at the same time, the state of the UI screen is changed to the notification screen 1207 and a message that the creation of X (in this example, up to three) color conversion LUTs is completed is displayed according to its necessity.

[0100] Fig.14 1 is a flowchart showing the processing flow of creating a color conversion LUT according to this modification example. Fig.14 The process in is explained.

[0101] First, at S1401, by using the color characteristics of the image attributes used as a reference, a color conversion LUT corresponding to the image attributes is created among the color characteristics for each attribute acquired for the destination device and the color characteristics acquired for the adjustment device. The creation method of the color conversion LUT here is the same as in the case of S808, S809 described previously, so its explanation is omitted.

[0102] At the next S1402, based on the color characteristics of the image attribute and the color characteristics of the graphic attribute in the destination device, the color difference between the two attributes is found, and it is determined whether the color difference is so large as to exceed the allowable range. Specifically, the color difference between the L*a*b* value in the color characteristics of the image attribute and the L*a*b* value in the color characteristics of the graphic attribute is calculated for each color block, and the average color difference ΔE of the color difference of each color block is found, and it is determined whether the average color difference ΔE is less than or equal to a predetermined threshold. In the case where the average color difference ΔE exceeds the threshold, the process proceeds to S1403, and in the case where the average color difference ΔE is less than or equal to the threshold, the process proceeds to S1404.

[0103] At S1403, a color conversion LUT corresponding to the graphic attribute is created by using the color characteristics of the graphic attribute among the color characteristics for each attribute acquired for the destination device and the color characteristics of the adjustment device. Then, at S1404, based on the color characteristics of the image attribute and the color characteristics of the text attribute in the destination device, the color difference between the two attributes is found, and it is determined whether the color difference is so large as to exceed the allowable range. Specifically, the color difference between the L*a*b* value in the color characteristics of the image attribute and the L*a*b* value in the color characteristics of the text attribute is calculated for each color block, and the average color difference ΔE of the color difference of each color block is found, and it is determined whether the average color difference ΔE is less than or equal to a predetermined threshold. In the case where the average color difference ΔE exceeds the threshold, the process proceeds to S1405, and in the case where the average color difference ΔE is less than or equal to the threshold, this process is terminated.

[0104] At S1405, a color conversion LUT corresponding to the text attribute is created by using the color characteristic of the text attribute among the color characteristics for each attribute acquired for the destination device and the color characteristic of the adjustment device.

[0105] The above is the creation process of the color conversion LUT according to the present modification example. In the case of the present modification example, it is determined in the destination device whether the chromaticity as a result of the color processing is different between the object attributes, and only when the chromaticity is different, a color conversion LUT for reproducing the color of the destination device can be created for each object attribute.

[0106] <Modification Example 2>

[0107] With the method of the modified example 1 in which a target chart different for each object attribute is prepared and printed, the number of output charts increases, and therefore, time cost and economic cost will be increased with chart printing. In this regard, there is also a case where it is desired to perform accurate color adjustment on an image, but for text, it is sufficient to perform color adjustment only on the main color. Therefore, the user can also pre-set the number of color blocks to be formed on the target chart for each of the image attribute, the graphic attribute, and the text attribute, and form only the minimum necessary color blocks on the target chart. FIG. 15A to FIG. 15D Each is a diagram showing an example of a UI screen (number of color patches setting screen) for setting the number of color patches on a target chart. Fig.15A When you select any object property in the main screen, the screen display switches to FIG. 15B to FIG. 15D . The user selects "Large" in the case where the user desires to perform more accurate color adjustment or selects "Small" in the case where performing simple color adjustment is sufficient. Then, a print job of a target chart is generated for each attribute according to the number of color patches set for each object attribute and is printed and output in a destination device. Instead of a configuration in which the user is made to set the number of color patches, a configuration in which "Large" or "Small" in which the number of color patches is predetermined for each object attribute may be accepted. For example, "Large" is set for images, "Standard" is set for graphics, and "Small" is set for text. In this case, the time and effort to perform target chart printing can be reduced.

[0108] As described above, according to the present modification example, for a target chart of object properties for which simple color adjustment is sufficient, the number of color patches is reduced, and therefore, the number of charts can be reduced and the cost of chart printing can be suppressed.

[0109] <Modification Example 3>

[0110] Next, as a modification example 3, a method of reducing the cost of target chart printing by another method is explained. In this modification example, first, a target chart that refers to an object attribute (e.g., an image attribute) and a dedicated chart for determining whether the content of color processing is different for each object attribute (hereinafter referred to as a "attribute check chart") are printed and output. Then, by using the attribute check chart, it is determined whether the destination device has switched the color processing for each object attribute and the result is notified to the user, and the user is allowed to determine whether additional creation of a color conversion LUT is necessary.

[0111] Here, reference Fig.16 Interpret the property inspection chart. Fig.16The property check chart 1600 shown in is divided into an area for each of the three object attributes of image attribute, graphic attribute and text attribute. Then, in the area of ​​image attribute, a color block group 1601 and a color block group 1602 are included. Similarly, in the area of ​​graphic attribute, a color block group 1603 and a color block group 1604 are included, and in the area of ​​text attribute, a color block group 1605 and a color block group 1606 are included. Then, in each of the color block groups 1601 to 1606, six primary colors are arranged respectively, and the color block groups 1601, 1603 and 1605 are composed of color blocks with high concentration, while the color block groups 1602, 1604 and 1606 are composed of color blocks with low concentration. The six primary colors are cyan, magenta, yellow, red, green and blue. Table 2 below shows the color values ​​in the color blocks with high concentration, and Table 3 shows the color values ​​in the color blocks with low concentration.

[0112] [Table 2]

[0113]

[0114] Table 3

[0115]

[0116] As described above, in the attribute check chart, a color patch group of six primary colors with different concentrations is arranged for each object attribute. By reading a dedicated chart such as this to find the color difference between the object attributes, it is possible to determine whether the color processing has been switched for each object attribute in the destination device. In addition, by providing two color patches for each color, i.e., a dark patch and a pale patch, it is also possible to determine whether the object attributes have different gamma characteristics.

[0117] Fig.17 1 is a flowchart showing the processing flow of creating a color conversion LUT according to this modification example. Fig.17 The process in is explained.

[0118] First, at S1701, a color conversion LUT corresponding to the image attribute is created by using the color characteristics of the reference image attribute and the color characteristics acquired for the adjustment device. In the case of this modified example, at this time, for the object attributes other than the image attribute (i.e., the graphic attribute and the text attribute), the printing of the target chart is not performed, and therefore, the color characteristics are not acquired. This modified example is different from the modified example 1 in this point. The method of creating the color conversion LUT is the same as in the case of S808, S809 described previously, so its explanation is omitted.

[0119] At S1702, based on the color characteristics obtained from the above-mentioned attribute check chart, it is determined whether the color difference between the object attribute of interest, which is one of the other object attributes other than the image attribute, and the image attribute is less than or equal to a predetermined threshold value. At this time, in the case of, for example, taking the graphic attribute as another object attribute of interest, a total of 12 color blocks included in the color block groups 1601 and 1602 of the image attribute and a total of 12 color blocks included in the color block groups 1603 and 1604 of the graphic attribute are used. Specifically, it is sufficient to calculate the color difference between the image attribute and the graphic attribute by comparing the L*a*b* values ​​between the color blocks of corresponding colors (for example, between the color blocks of dark cyan) and determine whether the found color difference is less than or equal to a predetermined threshold value. Then, in the case where the color difference is less than or equal to the threshold value in all 12 color blocks, the processing proceeds to S1707, and in the case where there is even one color difference exceeding the threshold value among the 12 color blocks, the processing proceeds to S1703. This threshold processing is the same as that at S1402. In the case where the result of the determination indicates that the color difference ΔE exceeds a predetermined threshold value, the process proceeds to S1703 , and in the case where it is less than or equal to the threshold value, the process proceeds to S1707 .

[0120] At S1703, a warning that chromaticity is different between the reference image attribute and another object attribute of interest is notified to the user. As an aspect of notification, for example, an aspect of displaying a warning message on the display unit 105 is considered. At subsequent S1704, it is determined whether an instruction to create a color conversion LUT suitable for another object attribute of interest is input via a UI screen not schematically shown. In the case where the user inputs a creation instruction, the process proceeds to S1705, and in the absence of such an instruction, the process proceeds to S1707.

[0121] At S1705, a target chart of another object property of interest is printed and output in the destination device and the result is read, thereby acquiring the color characteristics of another object property of interest. Next, at S1706, a color conversion LUT is created by using the color characteristics of another object property of interest acquired at S1705. The method of creating the color conversion LUT here is also the same as the case of S808 and S809 described previously, so its explanation is omitted.

[0122] At S1707, determine whether all other object attributes except the image object have been checked for color difference with the image attribute. In the case of another unprocessed object attribute, the process returns to S1702 and continues to process, and in the case of having checked all other object attributes, terminate this process.

[0123] The above is the creation process of the color conversion LUT according to this modified example. In the case of this modified example, for other object attributes other than the reference object attribute, color characteristics are obtained only when necessary, so the number of target charts used is suppressed, and time cost and economic cost can be reduced.

[0124] <Modification Example 4>

[0125] In the above-mentioned embodiments including each of the above-mentioned modification examples, an example in which color adjustment between the destination device and the adjustment device is achieved by a color conversion LUT that converts RGB values ​​into CMYK values ​​is explained, but color adjustment between devices can also be performed by using another printing parameter. For example, it is also possible to fix the color conversion LUT from RGB to CMYK used in the adjustment device, and create a LUT for converting RGB into R'G'B', which is used to adjust the RGB value input to the fixed color conversion LUT so as to obtain the same color characteristics as the destination device. Alternatively, it is also possible to create a LUT for converting CMYK into C'M'Y'K', which is used to adjust the CMYK value output from the fixed color conversion LUT. In addition, it can also be achieved by replacing the function of the LUT format.

[0126] As described above, according to the present embodiment, a color conversion LUT is created for each object attribute by specifying the number configuration of the color components of gray in the destination device, etc. Thus, not only the chromaticity of the printed material in the adjustment device but also the texture in the adjustment device can be matched.

[0127] [Other embodiments]

[0128] The (one or more) embodiments of the present disclosure may also be implemented by a computer of a system or device that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more completely referred to as a "non-transitory computer-readable storage medium") to perform the functions of one or more of the above (one or more) embodiments and / or includes one or more circuits (e.g., application specific integrated circuits (ASICs)) for performing the functions of one or more of the above (one or more) embodiments, and by a method performed by a computer of the system or device, for example, by reading out and executing computer executable instructions from a storage medium to perform the functions of one or more of the above (one or more) embodiments and / or controlling one or more circuits to perform the functions of one or more of the above (one or more) embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessing unit (MPU)), and may include a network of separate computers or separate processors to read out and execute computer executable instructions. Computer executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, a hard disk, a random access memory (RAM), a read-only memory (ROM), a storage device of a distributed computing system, an optical disk (such as a compact disk (CD), a digital versatile disk (DVD), or a Blu-ray disk (BD)) TM ), one or more of flash memory devices, memory cards, etc.

[0129] According to the technology of the present disclosure, not only the chromaticity but also the texture of printed materials can be matched between different printing devices.

[0130] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the present disclosure is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0131] This application claims the benefit of Japanese Patent Application No. 2020-170576, filed on October 8, 2020, which is hereby incorporated by reference herein in its entirety.

Claims

1. An image forming device, comprising: a printing unit configured to print an image on a sheet; a scanning unit configured to scan a first sheet on which another image forming device has printed a first object in gray and to scan a second sheet on which a printing unit has printed a second object; a determination unit configured to determine, based on first image data generated by scanning of the first sheet, whether a gray color of a first object on the scanned first sheet is a gray color represented by only a black color material K or a gray color represented by a color material including a cyan color material C, a magenta color material M, and a yellow color material Y; as well as The control unit is configured to perform a color matching process for matching between the color characteristics of the printing unit and the color characteristics of the another image forming apparatus based on the first image data, the second image data generated by scanning of the second sheet, and the determination result of the determination unit.

2. The image forming apparatus according to claim 1, wherein The first object is a gray object in which the value of each of the R component, the G component, and the B component in the pixel values ​​of the pixels constituting the generated image data is equal, and The determination unit performs the determination based on saturation of pixels constituting the first object.

3. The image forming apparatus according to claim 2, wherein The determining unit obtains the saturation of pixels constituting the first object, and Sure: In a case where the number of pixels having a saturation corresponding to a color is greater than or equal to a predetermined number, the first object on the scanned first sheet has been printed with color materials including a color material of C, a color material of M, and a color material of Y; and In a case where the number of pixels having the saturation corresponding to the color is less than a predetermined number, the first object on the scanned first sheet has been printed with only the color material of K.

4. The image forming apparatus according to claim 2, wherein Determine the unit to determine: In a case where the number of pixels in which the difference between channels of the R component, the G component, and the B component in the pixel values ​​of the pixels constituting the gray area is greater than or equal to the predetermined threshold value is greater than or equal to the predetermined number, the first object on the scanned first sheet has been printed with color materials including the color material of C, the color material of M, and the color material of Y; and Wherein, in a case where the number of pixels in which the difference between the channels is greater than or equal to the predetermined threshold is less than a predetermined number, the first object on the scanned first sheet has been printed with only the color material of K.

5. The image forming apparatus according to claim 1, wherein The first object is a gray object in which the value of each of the R component, the G component, and the B component in the pixel values ​​of the pixels constituting the image data is equal, and The determination unit obtains one of a mean value, a median value, and a standard deviation of each of the R component, the G component, and the B component in the entire gray area, and performs determination based on the magnitude of the difference between the channels.

6. The image forming apparatus according to claim 1, wherein generating information used in a color conversion process by performing a color matching process based on the first image data, the second image data, and a determination result of the determination unit, and In the color conversion process, pixel values ​​of pixels constituting print target input image data are converted from the RGB color space into the CMYK color space.

7. The image forming apparatus according to claim 6, wherein another image forming apparatus, a first sheet on which a first object has been printed includes a plurality of gray areas corresponding to each of different object attributes, The determination unit performs determination for each object attribute.

8. The image forming apparatus according to claim 7, wherein The different object attributes include at least image attributes, graphic attributes and text attributes.

9. The image forming apparatus according to claim 7, further comprising: The registration unit is configured to register a combination of information used in the color conversion process determined for each object attribute.

10. A method for controlling an image forming apparatus, the image forming apparatus performing a printing process based on input image data, the method comprising the following steps: printing an image on a sheet; scanning a first sheet on which another image forming device has printed a first object in gray and scanning a second sheet on which a printing unit has printed a second object; determining, based on first image data generated by scanning of the first sheet, whether a gray color of a first object on the scanned first sheet is a gray color represented by only a black K color material or a gray color represented by a color material including a cyan C color material, a magenta M color material, and a yellow Y color material; and A color matching process for matching between the color characteristic of the printing unit and the color characteristic of the another image forming apparatus is performed based on the first image data, the second image data generated by scanning of the second sheet, and the determination result of the determination unit.

11. A non-transitory computer-readable storage medium storing a program for causing a computer to execute a control method of an image forming apparatus, the image forming apparatus performing a printing process based on input image data, the control method comprising the following steps: printing an image on a sheet; scanning a first sheet on which another image forming device has printed a first object in gray and scanning a second sheet on which a printing unit has printed a second object; determining, based on first image data generated by scanning of the first sheet, whether a gray color of a first object on the scanned first sheet is a gray color represented by only a black K color material or a gray color represented by a color material including a cyan C color material, a magenta M color material, and a yellow Y color material; and A color matching process for matching between the color characteristic of the printing unit and the color characteristic of the another image forming apparatus is performed based on the first image data, the second image data generated by scanning of the second sheet, and the determination result of the determination unit.

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