Image processing device, image processing system, image processing method and program

Abstract

To provide an image processing apparatus, an image processing system, an image processing method, and a program that can improve the ability to deal with sheets different in printing characteristics while securing tone reproducibility.SOLUTION: An image processing apparatus comprises: a first acquisition unit that acquires colorimetric values of a plurality of single-color patches on a first chart read by a colorimetric device and printed out by an image forming apparatus; a second acquisition unit that acquires a maximum tone value set in advance according to a sheet; a conversion unit that converts the colorimetric values, maximum tone value, and a color specification value in a first target that is the characteristics of an ideal color specification value for a tone value into predetermined color values; and a determination unit that determines, as a second target, characteristics passing through points defined by a color value corresponding to the maximum tone value generated based on the first target converted into the predetermined color value.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image processing device, an image processing system, an image processing method, and a program. [Background technology]

[0002] In recent years, image forming devices using electrophotographic, thermal, inkjet, or other methods have become widespread, such as digital color copiers and color printers. These image forming devices have problems such as variations in image density due to environmental changes, such as temperature or humidity, or due to deterioration of components over time, and differences in image density due to minute variations in the components of the image forming device from the time of shipment. To solve these problems, a process is required to readjust the color conversion table before using the image forming device and align the color conversion table with the target output characteristics. This process is called calibration.

[0003] A typical specific calibration method involves outputting a reference chart using a desired image forming device, reading a printout of the output reference chart using a scanner device, measuring the colors using a colorimetric device to analyze the output characteristics of the image forming device, and correcting the color conversion table so that the target output characteristics of C (cyan), M (magenta), Y (yellow), and K (black) are obtained.

[0004] As an example of such a technique, a method is disclosed in which, when performing monochromatic calibration, if the actual printer density is different from the ideal output characteristics due to fluctuations, a gradation correction table is generated that uses a target output density table and lowers the density to offset the fluctuations (for example, Patent Document 1). However, since the above-mentioned calibration is based on density, it does not support calibration of colors other than process colors.

[0005] On the market today, image forming devices perform advanced printing by adding spot color toners such as green or orange to process colors in order to print subtle hues or a color range that cannot be reproduced using process colors. While the International Commission on Illumination defines the density for each gradation value for process colors, it does not define this for colors other than process colors. Therefore, there are no defined target values for gradation values, and the issue of how to determine targets and perform calibration for spot color toners has become an issue.

[0006] In order to achieve the above-mentioned calibration of colors other than process colors, a technology has been disclosed in which a target, which is an ideal density characteristic for a gradation value, is generated by drawing a straight line from paper white to the value (solid) corresponding to the maximum gradation value of the colorimetric data to prevent the color correction for a color that is a mixture of two colors from being affected by colors other than the two colors (for example, Patent Document 2). In this way, since the target is generated by connecting paper white and the solid, it is possible to set the target for any toner. In other words, calibration is possible for colors other than process colors, and in addition, it is possible to handle any value for the maximum gradation value. Summary of the Invention [Problem to be solved by the invention]

[0007] In the technology described in Patent Document 2, because the target is generated as a straight line, the portion of the target corresponding to the range from highlights (low gradations) to mid-range gradations (halftones) is also represented as a straight line. However, considering that human vision is sensitive to gradation changes from highlights to halftones, a straight-line target results in a gradation change from highlights to halftones that is gradual, resulting in poor color reproduction near highlights. For example, in inkjet printers, the impact is minimal for paper with a wide color reproduction gamut (such as coated paper) because the target is nearly straight, but for paper with a narrow color reproduction gamut, such as matte paper, the quality of color reproduction is affected. In other words, previous calibration technologies have a problem in that they cannot ensure gradation reproduction from highlights to halftones while being able to accommodate different paper types with different printing characteristics, such as low or high density prints.

[0008] The present invention has been made in consideration of the above, and aims to provide an image processing device, an image processing system, an image processing method, and a program that can improve the ability to adapt to various types of paper with different printing characteristics while ensuring gradation reproducibility. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the present invention is characterized by comprising a first acquisition unit that acquires colorimetric values of multiple single-color patches of a first chart that is read by a colorimetric device and printed out by an image forming device; a second acquisition unit that acquires a maximum gradation value that is preset according to the paper; a conversion unit that converts the colorimetric values, the maximum gradation value, and the color specification values in a first target that is a characteristic of an ideal color specification value for the gradation value into predetermined color values; and a determination unit that determines, as a second target, a characteristic that passes through a point determined by a color value corresponding to the maximum gradation value, generated based on the first target converted to the predetermined color value. [Effects of the Invention]

[0010] According to the present invention, it is possible to improve the ability to handle various types of paper with different printing characteristics while ensuring gradation reproducibility. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of the overall configuration of an information processing system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of the information processing device according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of the functional block configuration of the image processing unit of the information processing apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of the functional block configuration of the calibration processing unit of the information processing device according to the embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a maximum gradation value setting screen. [Figure 6] FIG. 6 is a diagram showing an example of a calibration chart. [Figure 7] FIG. 7 is a diagram showing an example of a visual chart. [Figure 8] FIG. 8 is a flowchart showing an example of the flow of the calibration operation in the information processing system according to the embodiment. [Figure 9] FIG. 9 is a flowchart showing an example of the flow of the calibration process in the information processing device according to the embodiment. [Figure 10] FIG. 10 is a diagram illustrating a new target generation process of the information processing apparatus according to the embodiment. [Figure 11] FIG. 11 is a diagram illustrating a boundary at which the method for generating a new target is switched. [Figure 12] FIG. 12 is a diagram illustrating the process of creating a γ table in the information processing apparatus according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of an image processing device, an image processing system, an image processing method, and a program according to the present invention will be described in detail with reference to the drawings. Furthermore, the present invention is not limited to the following embodiments, and the components in the following embodiments include those that would be easily conceived by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, various omissions, substitutions, modifications, and combinations of the components can be made without departing from the spirit of the following embodiments.

[0013] (Overall configuration of information processing system) 1 is a diagram showing an example of the overall configuration of an information processing system according to an embodiment, and the overall configuration of the information processing system 1 according to this embodiment will be described with reference to FIG.

[0014] As shown in FIG. 1, an information processing system 1 (image processing system) includes an information processing device 10, a host computer 20, an image forming device 30, and a color measurement device 40.

[0015] The information processing device 10 is an image processing device that receives image information from the host computer 20, performs predetermined image processing on the image information, generates image data in a format that can be printed out by the image forming device 30, and transmits the image data to the image forming device 30. Note that the information processing device 10 may be an information processing device such as a normal PC (Personal Computer), a controller dedicated to the image forming device 30, or a controller installed within the image forming device 30. As shown in FIG. 1, the information processing device 10 includes an image processing unit 11 and a calibration processing unit 12.

[0016] The image processing unit 11 is a functional unit that executes predetermined image processing on image information received from the host computer 20 using calibration data (for example, a γ table) created by the calibration processing unit 12.

[0017] The calibration processing unit 12 is a functional unit that executes calibration processing. Specifically, the calibration processing unit 12 executes calibration processing and creates a γ table using the maximum gradation value input to the host computer 20 based on the visual chart VC printed by the image forming apparatus 30 and the colorimetric values of the calibration chart CC printed by the image forming apparatus 30. The calibration processing unit 12 sends the created γ table to the image processing unit 11.

[0018] The host computer 20 is an information processing device such as a PC that, when a print processing instruction is issued from an application running on the host computer 20, operates a printer driver and transmits image information to be printed to the information processing device 10. The host computer 20 also receives parameters used for calibration processing and the like via an input device such as a mouse or keyboard.

[0019] The image forming device 30 is, for example, an inkjet color printer or the like that prints out based on image data received from the information processing device 10. The image forming device 30 also prints out a calibration chart CC (first chart) and a visual chart VC (second chart) to be used in the calibration process in the information processing device 10. In this case, image information for the calibration chart CC and the visual chart VC may be stored in, for example, the host computer 20.

[0020] As described above, the calibration process is performed using the maximum gradation value input by the user (administrator) based on the visual chart VC printed out from the image forming apparatus 30, but this is not limiting. For example, during the calibration process by the calibration processing unit 12, the display device of the host computer 20 may display an image of the visual chart VC, and the user may check the image and input the maximum gradation value. Alternatively, during the calibration process by the calibration processing unit 12, the display device of the host computer 20 may display the colorimetric values of the calibration chart CC measured by the colorimetric device 40, and the user may check the colorimetric values and input the maximum gradation value.

[0021] In addition, in the example shown in Figure 1, the color measurement device 40 is configured as a device independent of the image forming device 30, but it may also be a reading device such as a scanner, or a color measurement device built into the paper transport path of the image forming device.

[0022] The colorimetric device 40 is a device such as a spectroreflectometer that obtains colorimetric values by reading (measuring) color patches included in the calibration chart CC printed out by the image forming device 30. The colorimetric values are, for example, Lab values, which are color values in the L*a*b* color system, or tristimulus values XYZ.

[0023] Although not shown in FIG. 1, the information processing device 10, the host computer 20, the image forming device 30, and the color measurement device 40 may be capable of communicating with each other via a network such as a LAN (Local Area Network).

[0024] (Hardware configuration of information processing device) 2 is a diagram showing an example of the hardware configuration of the information processing device 10 according to the embodiment, with reference to which the hardware configuration of the information processing device 10 according to the embodiment will be described.

[0025] As shown in FIG. 2, the information processing device 10 includes a CPU (Central Processing Unit) 501, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, an auxiliary storage device 505, a media drive 507, a display 508, a network I / F 509, a keyboard 511, a mouse 512, and a DVD (Digital Versatile Disc) drive 514.

[0026] The CPU 501 is a computing device that controls the overall operation of the information processing device 10. The ROM 502 is a non-volatile storage device that stores programs such as an IPL (Initial Program Loader) that is initially executed by the CPU 501. The RAM 503 is a volatile storage device that is used as a work area for the CPU 501.

[0027] The auxiliary storage device 505 is a non-volatile storage device that stores various data such as programs, etc. The auxiliary storage device 505 is, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0028] The media drive 507 is a device that controls reading and writing of data from and to a recording medium 506 such as a flash memory.

[0029] The display 508 is a liquid crystal display (LCD) or an organic electroluminescence (EL) display that displays various types of information such as a cursor, menu, window, text, or image.

[0030] The network I / F 509 is an interface for communicating data with the host computer 20, the image forming device 30, the colorimetry device 40, etc., via a network. The network I / F 509 is, for example, a network interface card (NIC) that enables communication using a TCP (Transmission Control Protocol) / IP (Internet Protocol) protocol. The network I / F 509 may also be a communication interface having a wireless communication function based on a standard such as Wi-Fi (registered trademark).

[0031] The keyboard 511 is an example of an input device having multiple keys for inputting characters, numbers, various instructions, etc. The mouse 512 is a type of input device for selecting and executing various instructions, selecting a processing target, moving a cursor, etc.

[0032] The DVD drive 514 is a device that controls reading and writing of various data from and to a DVD 513, which is an example of a removable storage medium. The DVD 513 is, for example, a DVD-RW (Digital Versatile Disk Rewritable), a DVD-R (Digital Versatile Disk Recordable), a CD-RW (Compact Disc Rewritable), or a CD-R (Compact Disc Recordable).

[0033] The above-mentioned CPU 501, ROM 502, RAM 503, auxiliary storage device 505, media drive 507, display 508, network I / F 509, keyboard 511, mouse 512 and DVD drive 514 are connected to each other so that they can communicate with each other via bus lines 510 such as an address bus and a data bus.

[0034] 2 is an example, and does not necessarily include all of the components, and other components may also be included. For example, if operation input or information display is not required on the information processing device 10, the keyboard 511, mouse 512, display 508, etc. may not be included. The host computer 20 may also have a hardware configuration similar to that shown in FIG. 2.

[0035] (Configuration and operation of functional blocks of the image processing unit of the information processing device) 3 is a diagram showing an example of the functional block configuration of the image processing unit of the information processing device according to the embodiment. The configuration and operation of the functional block of the image processing unit 11 of the information processing device 10 according to the embodiment will be described with reference to FIG.

[0036] As shown in FIG. 3, the image processing unit 11 of the information processing device 10 includes a rasterization processing unit 111, a color rendering processing unit 112, a color separation processing unit 113, and a halftone processing unit 114.

[0037] The rasterization processing unit 111 is a functional unit that interprets the drawing commands and expands image information received from the host computer 20, which is data in the form of drawing commands composed of RGB color signals for display, into bitmap data with 8 bits for each RGB color. The rasterization processing unit 111 sends the expanded bitmap data with 8 bits for each RGB color to the color rendering processing unit 112.

[0038] The color rendering processing unit 112 is a functional unit that converts the 8-bit bitmap data for each RGB color received from the rasterization processing unit 111 into R'G'B' (8-bit) data that has undergone color gamut compression to fit the color reproduction range of the image forming device 30, using a profile associated with the device. This makes it possible to accommodate differences in the color reproduction range and color reproduction characteristics between the display and the image forming device 30. The color rendering processing unit 112 sends the converted R'G'B' (8-bit) data to the color separation processing unit 113.

[0039] The color separation processing unit 113 is a functional unit that performs color separation processing called UCR (Under Color Removal) / UCA (Under Color Addition) on the R'G'B' (8-bit) data received from the color rendering processing unit 112, thereby separating the data into 8-bit CMYK image data. Here, the image forming device 30 uses four colors: C (cyan), M (magenta), Y (yellow), and K (black). The color separation processing unit 113 sends the obtained 8-bit CMYK image data to the halftone processing unit 114.

[0040] The halftone processing unit 114 is a functional unit that converts the 8-bit CMYK image data received from the color separation processing unit 113 into CMYK image data with a smaller number of bits (for example, 3 bits) that can be output by the image forming device 30. At this time, the halftone processing unit 114 applies the γ table, which is the gradation input / output characteristic (color conversion characteristic) created by the calibration processing unit 12, to each of CMYK, and then converts the data into CMYK image data that can be output by the image forming device 30. This achieves the effect of calibration.

[0041] The rasterization processing unit 111, color rendering processing unit 112, color separation processing unit 113, and halftone processing unit 114 of the image processing unit 11 shown in Fig. 3 are realized, for example, by a program being executed by the CPU 501 shown in Fig. 2. Note that the rasterization processing unit 111, color rendering processing unit 112, color separation processing unit 113, and halftone processing unit 114 may be realized by hardware such as an integrated circuit, or may be realized by a combination of software and hardware.

[0042] Furthermore, the functional units of the image processing unit 11 shown in Fig. 3 are conceptually shown, and are not limited to such a configuration. For example, the multiple functional units shown as independent functional units in the image processing unit 11 shown in Fig. 3 may be configured as a single functional unit. On the other hand, the function of one functional unit in the image processing unit 11 shown in Fig. 3 may be divided into multiple units and configured as multiple functional units.

[0043] (Configuration and operation of functional blocks of a calibration processing unit of an information processing device) Fig. 4 is a diagram showing an example of the configuration of functional blocks of a calibration processing unit of the information processing device according to the embodiment. Fig. 5 is a diagram showing an example of a maximum gradation value setting screen. Fig. 6 is a diagram showing an example of a calibration chart. Fig. 7 is a diagram showing an example of a visual chart. The configuration and operation of functional blocks of the calibration processing unit 12 of the information processing device 10 according to the present embodiment will be described with reference to Figs. 4 to 7.

[0044] As shown in FIG. 4, the calibration processing unit 12 includes a first acquisition unit 121, a second acquisition unit 122, a conversion unit 123, a first target generation unit 124 (first generation unit), a judgment unit 125, a second target generation unit 126 (second generation unit), a target determination unit 127 (determination unit), and a table creation unit 128 (creation unit).

[0045] The first acquisition unit 121 is a functional unit that acquires, via the network I / F 509, colorimetric values obtained by the colorimetric device 40 measuring the color of the calibration chart CC.

[0046] Here, the calibration chart CC will be described. The calibration chart CC is printed by the image forming apparatus 30 based on image data in CMYK format, and is a sample chart in which rectangular areas (hereinafter referred to as patches) expressed by various gradation values are arranged. Each patch of the calibration chart CC is printed at a pitch of a predetermined gradation value for each of the primary colors C, M, Y, and K of the image forming apparatus 30. The calibration chart CC shown in FIG. 6 is configured with patches of each of the single colors C, M, Y, and K arranged for n gradations. Note that n is an integer equal to or less than 256, and in the example shown in FIG. 5, n=10. In FIG. 6, the calibration chart CC shown in FIG. 6(a) is a chart in which patches of each color and gradation are randomly arranged, while the calibration chart CC shown in FIG. 6(b) is a chart in which patches are arranged in a row in gradation order for each color. Either the calibration chart CC shown in FIG. 6(a) or FIG. 6(b) can be used. However, in order to reduce the impact of adjacent patches or the glare of the white paper on the colorimetric values, a calibration chart CC with randomly arranged patches as shown in Figure 6(a) is used, and multiple copies of this calibration chart CC are printed. The average of the colorimetric values for each patch of the same color and the same gradation can be obtained, thereby reducing the impact of adjacent patches and the glare of the white paper on the colorimetric values.

[0047] The first acquisition unit 121 stores the acquired colorimetric values in the auxiliary storage device 505.

[0048] The second acquisition unit 122 is a functional unit that acquires, via the network I / F 509, the maximum gradation value input to the host computer 20 by the user (administrator) based on the visual chart VC printed out from the image forming apparatus 30.

[0049] Here, the visual chart VC will be described. As shown in FIG. 7, the visual chart VC is printed out by the image forming apparatus 30 based on image data in CMYK format, and is a chart configured by arranging areas each representing a gradation of 0 to 100% for each color. In the example of the visual chart VC shown in FIG. 7, a memory is arranged so that the gradation value can be grasped for each color gradation area. Note that for comparison, some of the areas may be shifted by 5%. Furthermore, in the example shown in FIG. 7, the gradation areas for each color are rectangular, but this is not limited thereto and may be circular gradation areas.

[0050] The user (administrator) performing the calibration checks the visual chart VC configured as described above, and inputs the maximum gradation value of each process color (single color) on a maximum gradation value setting screen 1000 displayed on the display (display 508 shown in FIG. 2) of the host computer 20. As shown in FIG. 5, the maximum gradation value setting screen 1000 includes a setting method selection section 1001, a maximum value input section 1002, and an enter button 1003. The setting method selection section 1001 is an area for selecting the method for inputting the maximum gradation value. The maximum value input section 1002 is an input area for inputting the maximum gradation value of each process color (single color).

[0051] For example, if "Automatically Set to Maximum Value" is selected in the setting method selection unit 1001, the maximum gradation value calculated within the host computer 20 is input to the maximum value input unit 1002. In this case, if the calculation by the host computer 20 determines that the density remains almost unchanged at a gradation value of 90% or higher, 90% is automatically input as the maximum gradation value into the maximum value input unit 1002. Alternatively, the maximum gradation value may be changed to the maximum gradation value that the toner can output, or a value that is 80% of the maximum gradation value that the toner can output, or a value at which the toner density saturates, may be automatically input into the maximum value input unit 1002. In this embodiment, the maximum value input unit 1002 is described as inputting a gradation value of 0 to 100% as the maximum gradation value of each color. In this case, the user visually checks the gradation area of each color on the visual chart VC and, referring to the memory, inputs the gradation value that is deemed to be the maximum into the maximum value input unit 1002 as the maximum gradation value. That is, the maximum gradation value considered to be the maximum in the visual chart VC varies depending on the type of paper used for the visual chart VC, so the user inputs a maximum gradation value appropriate for each paper. This enables calibration using Lab values or the tristimulus values XYZ (described later) corresponding to any maximum gradation value, improving compatibility with various paper types. For example, if the user determines that there is almost no noticeable difference in density between 95 and 100% in a cyan (C) gradation, the user inputs 95% as the maximum gradation value for C (cyan). Furthermore, by inputting a gradation value considered to be the maximum density rather than 100% as the maximum gradation value, it is possible to prevent excessive ink application and resulting paper distortion when printing at a gradation value of 100%. It is also possible to reduce costs by suppressing the use of excess ink. If the maximum density can be set as the maximum gradation value, it is also possible to input a density or Lab value.

[0052] The decision button 1003 is a button for deciding the maximum gradation value input in the maximum value input section 1002. When the decision button 1003 is pressed, the host computer 20 transmits the maximum gradation value of each color input in the maximum value input section 1002 to the information processing device 10. Then, the second acquisition section 122 acquires the maximum gradation value of each color transmitted from the host computer 20 via the network I / F 509, and stores the maximum gradation value of each color in the auxiliary storage device 505.

[0053] The conversion unit 123 is a functional unit that converts the colorimetric values acquired by the first acquisition unit 121, the maximum gradation value acquired by the second acquisition unit 122, and the color specification values of the existing target (first target) into Lab distances (described later) for use in the calibration process. Here, the existing target indicates ideal density characteristics for gradation values and is stored in advance in the auxiliary storage device 505. The existing target may be, for example, any color specification value characteristics such as Lab values for gradation values, tristimulus values XYZ, or values converted from these. The existing target may be determined from a printing standard or profile, or may be artificially determined as master data. The existing target may be stored in advance in the auxiliary storage device 505 (or ROM 502) as table-format data at the time of product shipment.

[0054] Furthermore, the conversion unit 123 converts the above-mentioned colorimetric values (Lab values), maximum gradation values, and color specification values of existing targets into relative Lab values based on paper white. Relative Lab values are not absolute Lab values, which are Lab values when irradiated with CIE standard illuminant D50, but Lab values based on paper white in order to prevent ink from being applied to a gradation value of 0% (paper white). Here, the absolute Lab values are represented as L_abs, a_abs, and b_abs, the absolute Lab values of paper white are represented as L_0, a_0, and b_0, and the relative Lab values are represented as L_ref, a_ref, and b_ref. In this case, if the values converted from the CIE1976 (L*, a*, b*) color space to the tristimulus values XYZ of the CIE1931XYZ color space are X_abs, Y_abs, Z_abs, X_0, Y_0, Z_0, and X_ref, Y_ref, Z_ref, X_ref, Y_ref, and Z_ref are calculated using the following equation (1).

[0055] X_ref=(X_D50 / X_0)×X_abs ···(1) Y_ref=(Y_D50 / Y_0)×Y_abs Z_ref=(Z_D50 / Z_0)×Z_abs

[0056] Here, X_D50, Y_D50, and Z_D50 are expressed by the following equation (2).

[0057] X_D50≒0.9642 (2) Y_D50≒1 Z_D50≒0.8249

[0058] Here, the tristimulus values X_D50, Y_D50, and Z_D50 in the above formula (2) are the white point of the D50 light source. By converting the tristimulus values X_ref, Y_ref, and Z_ref obtained in the above formula (1) into Lab values, it is possible to calculate L_ref, a_ref, and b_ref, which are relative Lab values from paper white. In this way, the conversion unit 123 converts the above-mentioned colorimetric values (Lab values), maximum gradation values, and color specification values in existing targets into relative Lab values based on paper white.

[0059] Furthermore, the conversion unit 123 converts the relative Lab values into Lab distances so that the relative Lab values, which use paper white as a reference (origin), can be treated as one-dimensional indices for gradation values. For data having Lab values for gradation values, the Lab distance can be expressed as in the following formula (3), where the Lab values of paper white are defined as L_white, a_white, and b_white, and the i-th Lab value for gradation values other than paper white is defined as L_i, a_i, and b_i.

[0060] Lab distance(i)=√{(L_i-L_white) 2 +(a_i-a_white) 2 +(b_i-b_white) 2} ···(3)

[0061] The conversion unit 123 converts the relative Lab values of the colorimetric value, the maximum gradation value, and the color specification value in the existing target into Lab distances using the above formula (3).

[0062] When calculating the Lab distance, the conversion unit 123 may perform linear interpolation to interpolate between the Lab distances of the discrete chart or the Lab distances of the existing target, or may perform processing to remove outliers caused by colorimetry errors or the like by moving average processing or threshold judgment. For example, when performing interpolation, the conversion unit 123 may perform spline linear interpolation so that Y = f(X), where X is the gradation value of a patch on the calibration chart CC and Y is the Lab distance for the gradation value X. Furthermore, although the conversion unit 123 has been described as converting the colorimetric value, maximum gradation value, and color specification value of the existing target into Lab distance, the conversion is not limited to Lab distance and may also convert color values related to a predetermined color system other than Lab distance.

[0063] The first target generation unit 124 is a functional unit that generates a temporary target F'(x) (third target) from the maximum gradation value converted by the conversion unit 123 and the Lab distance of the existing target. Here, x is the gradation value, and F'(x) is the Lab distance calculated from the gradation value x. For example, if the existing target is E(x), the Lab distance corresponding to the maximum gradation value is IL, and the gradation value of the connection point is C, the first target generation unit 124 generates a temporary target F'(x) expressed by the following equations (4) and (5).

[0064] F'(x)=E(x)+(IL-E(100)){(xC) / (100-C)} 2 (x>C) (4) F'(x) = E(x) (for x ≦ C) (5)

[0065] Here, the connection point is a point that moves on the existing target E(x), as shown in Fig. 10, which will be described later, and is a point that connects the graph of the portion of the graph of the provisional target F'(x) expressed by the above-mentioned formula (4) with the graph of the portion expressed by the formula (5). Therefore, the provisional target F'(x) is a function that passes through the connection point and the Lab distance to the maximum gradation value for each color set based on the visual chart VC, and is a graph where the graph of the portion expressed by the above-mentioned formula (4) and the graph of the portion expressed by the formula (5) are continuously connected at the connection point.

[0066] It is desirable that the temporary target F'(x) generated by the first target generation unit 124 match the existing target E(x) as closely as possible, but as described above, the maximum gradation value is set by the user, and the Lab distance corresponding to that maximum gradation value is predetermined, so it is not possible to generate a temporary target F'(x) that strictly matches the existing target E(x). Therefore, the first target generation unit 124 searches for a temporary target F'(x) on the existing target E(x) that satisfies the following (Condition 1) and (Condition 2).

[0067] (Condition 1) The tentative target F'(x) has a part that follows the existing target E(x) (an example of the first condition). (Condition 2) The portion of the tentative target F'(x) that does not follow the existing target E(x) has gradation (an example of the second condition).

[0068] Here, tonality refers to the property that the Lab distance increases continuously and monotonically as the tone value increases, and is a concept that also includes a state in which the Lab distance (an example of a color value) is saturated. More specifically, in this embodiment, it is desirable for the tonality to avoid abrupt changes or extreme saturation in the Lab distance as the tone value increases. For example, when 256 patches ranging from tone values 0 to 100 are prepared, it is desirable for the color difference between adjacent patches (e.g., ΔE76) to be less than 0.1. If the Lab distance is expressed as the distance in Lab space from paper white, tonality (continuity) for this color value means that the Lab distance also increases as the tone value increases. However, there is a limit to the increase per unit tone value, for example, 0.1 per 1%. When the provisional target F'(x) is generated using the above equations (4) and (5), there will be a portion that follows the existing target E(x) according to equation (5), so in this case (condition 1) will always be satisfied. Note that (Condition 1) may be that the portion of the temporary target F'(x) that follows the existing target E(x) exists within a predetermined gradation range or more. In this case, depending on the position of the connection point, there may be cases where (Condition 1) is not satisfied.

[0069] The determination unit 125 is a functional unit that determines whether or not the tentative target F'(x) satisfies both (Condition 1) and (Condition 2) when the above-mentioned connection point is moved on the existing target E(x).

[0070] The second target generation unit 126 is a functional unit that generates G(x) (fourth target) expressed by the following equation (6) as a new target when the judgment unit 125 determines that (Condition 1) and (Condition 2) are not satisfied even if the connection point is moved on the existing target E(x).

[0071] G(x)=F”(x) / F”(100)×IL ···(6)

[0072] Here, F"(x) is the target when the connection point in the temporary target F'(x) is near the gradation value x=0. Therefore, the new target G(x) is generated based on the ratio of the target F"(x), and is obtained by normalizing the target F"(x) and multiplying it by a variable. As mentioned above, the target F"(x) is the temporary target F'(x) when the connection point is near the gradation value x=0, but it is preferable that it satisfies (Condition 2), that is, that it monotonically increases. Furthermore, the target F"(x) can be calculated in any way, but can be calculated in advance, for example, by iterating the Lab distance IL to find out up to what Lab distance IL the temporary target F'(x) can express.

[0073] The target determination unit 127 is a functional unit that determines a new target (second target) based on the result of the determination by the determination unit 125. Specifically, if a tentative target F'(x) that is determined by the determination unit 125 to satisfy both (Condition 1) and (Condition 2) is found, the target determination unit 127 determines the tentative target F'(x) as the new target F(x). On the other hand, if a tentative target F'(x) that is determined by the determination unit 125 to satisfy both (Condition 1) and (Condition 2) is not found, the target determination unit 127 determines the target G(x) generated by the second target generation unit 126 as the new target.

[0074] The table creation unit 128 is a functional unit that creates a γ table, which is a TRC (Tone Reproduction Curve) for correcting gradation values, using the new target determined by the target determination unit 127. A specific method for creating a γ table will be described later.

[0075] The first acquisition unit 121, the second acquisition unit 122, the conversion unit 123, the first target generation unit 124, the determination unit 125, the second target generation unit 126, and the target determination unit 127 of the calibration processing unit 12 shown in Fig. 4 are realized, for example, by a program being executed by the CPU 501 shown in Fig. 2. Note that the first acquisition unit 121, the second acquisition unit 122, the conversion unit 123, the first target generation unit 124, the determination unit 125, the second target generation unit 126, and the target determination unit 127 may be realized by hardware such as an integrated circuit, or may be realized by a combination of software and hardware.

[0076] Furthermore, the functional units of the calibration processing unit 12 shown in Fig. 4 are conceptually shown, and are not limited to such a configuration. For example, the multiple functional units shown as independent functional units in the image processing unit 11 shown in Fig. 4 may be configured as a single functional unit. On the other hand, the function of one functional unit in the image processing unit 11 shown in Fig. 4 may be divided into multiple units and configured as multiple functional units.

[0077] (Calibration operation flow of information processing system) 8 is a flowchart showing an example of the flow of the calibration operation in the information processing system 1 according to the embodiment. The flow of the calibration operation in the information processing system 1 according to the embodiment will be described with reference to FIG.

[0078] <Step S11> The user operates the host computer 20 to cause the image forming apparatus 30 to print out the image information of the calibration chart CC and the visual chart VC stored in the host computer 20 via the information processing apparatus 10.

[0079] <Step S12> The user then places the calibration chart CC printed out from the image forming apparatus 30 in the colorimetric device 40 and causes the colorimetric device 40 to perform a reading (colorimetric) process on the calibration chart CC. The colorimetric device 40 transmits the colorimetric values of each patch of the calibration chart CC obtained by reading the calibration chart CC to the information processing apparatus 10. The calibration processing unit 12 of the information processing apparatus 10 receives the colorimetric values from the colorimetric device 40. Then, the process proceeds to step S13.

[0080] <Step S13> The user checks the visual chart VC printed out from the image forming apparatus 30, and inputs the maximum gradation value of each process color (single color) on the maximum gradation value setting screen 1000 displayed on the display (display 508 shown in FIG. 2) of the host computer 20. The host computer 20 then transmits the maximum gradation value of each color input on the maximum gradation value setting screen 1000 to the information processing apparatus 10. Then, the process proceeds to step S14.

[0081] <Step S14> The calibration processing unit 12 of the information processing device 10 performs calibration processing for CMYK using the existing target, the colorimetric values received from the colorimetric device 40, and the maximum gradation value received from the host computer 20. When the calibration processing is completed, the calibration processing unit 12 may, for example, notify the host computer 20 of the completion, so that the user can confirm the notification. Details of the calibration processing by the calibration processing unit 12 will be described later with reference to FIGS. 9 to 12.

[0082] (Flow of calibration process of information processing device) FIG. 9 is a flowchart showing an example of the flow of calibration processing in the information processing device according to the embodiment. FIG. 10 is a diagram illustrating new target generation processing in the information processing device according to the embodiment. FIG. 11 is a diagram illustrating a boundary at which the new target generation method switches. FIG. 12 is a diagram illustrating γ table creation processing in the information processing device according to the embodiment. The flow of calibration processing in the calibration processing unit 12 of the information processing device 10 according to this embodiment will be described with reference to FIGS. 9 to 12. Note that the calibration processing by the calibration processing unit 12 is performed for each of the process colors.

[0083] <Step S141> The first acquisition unit 121 of the calibration processing unit 12 acquires, via the network I / F 509, colorimetric values obtained by measuring the color of the calibration chart CC using the colorimetric device 40. Furthermore, the second acquisition unit 122 of the calibration processing unit 12 acquires, via the network I / F 509, the maximum gradation value of each color transmitted from the host computer 20. Then, the process proceeds to step S142.

[0084] <Step S142> The conversion unit 123 of the calibration processing unit 12 converts the colorimetric values acquired by the first acquisition unit 121, the maximum gradation values acquired by the second acquisition unit 122, and the color specification values of the existing targets into relative Lab values based on paper white in order to use them in the calibration process, and further converts the relative Lab values into Lab distances in order to treat them as one-dimensional indexes for the gradation values. Then, the process proceeds to step S143.

[0085] <Step S143> The first target generation unit 124 of the calibration processing unit 12 determines the initial value of the connection point moving on the existing target E(x). In the example shown in FIG. 10(a), the first target generation unit 124 sets the initial value of the connection point on the existing target E(x) to a gradation value C=100[%]. Note that the initial value of the connection point is not limited to a gradation value C=100[%], and other points may be set as the initial value. Also, in the example shown in FIG. 10(a), the Lab distance of the maximum gradation value is set below the Lab distance at a gradation value C=100[%] of the existing target E(x), but this is not limiting and the Lab distance may be set above the existing target E(x). Even in this case, the same processing as the subsequent processing can be performed. Then, the process proceeds to step S144.

[0086] <Step S144> Next, the first target generation unit 124 generates a tentative target F'(x) using the above-mentioned formulas (4) and (5), and then proceeds to step S145.

[0087] <Step S145> The determination unit 125 of the calibration processing unit 12 determines whether the temporary target F'(x) generated by the first target generation unit 124 satisfies both (Condition 1) and (Condition 2). For example, in step S149, when the connection point is moved toward the gradation value x=0 side to the position shown in FIG. 10(b), the graph of the x>C portion (dotted line portion) of the temporary target F'(x) lacks gradation because the Lab distance decreases as the gradation value x increases, and therefore does not satisfy (Condition 2). In addition, in determining whether (Condition 2) is satisfied, the determination unit 125 may, for example, calculate the slope S(x)=dF'(x) / dx (e.g., dx≈0.01) for the graph of the x>C portion, and if the slope S(x) with respect to the gradation value x in the graph of that portion is non-negative and equal to or greater than a threshold value (e.g., 0.1), determine that gradation is maintained and that (Condition 2) is satisfied. For example, in step S149, when the connection point is moved toward the gradation value x=0 side, resulting in the position shown in Figure 10(c), the graph of the x>C portion (dotted line portion) of the temporary target F'(x) will satisfy (Condition 2) because the Lab distance increases as the gradation value x increases, resulting in a monotonous increase and gradation. If the temporary target F'(x) satisfies both (Condition 1) and (Condition 2) (Step S145: Yes), the process proceeds to step S146, and if at least one of (Condition 1) and (Condition 2) is not satisfied (Step S145: No), the process proceeds to step S147.

[0088] <Step S146> If the determination unit 125 determines that the temporary target F'(x) satisfies both (Condition 1) and (Condition 2), the target determination unit 127 of the calibration processing unit 12 determines the temporary target F'(x) as a new target F(x), and then proceeds to step S150.

[0089] <Step S147> The determination unit 125 determines whether the gradation value C of the connection point in the existing target E(x) is near x=0. That is, if the determination unit 125 determines that the gradation value C of the connection point is near x=0, it determines that the connection point cannot be moved any further toward x=0. If the gradation value C of the connection point is near x=0 (step S147: Yes), the process proceeds to step S148, and if the gradation value C of the connection point is not near x=0 (that is, the connection point can still be moved toward x=0) (step S147: No), the process proceeds to step S149.

[0090] <Step S148> If the determining unit 125 determines that the gradation value C of the connection point is near x=0, the second target generating unit 126 of the calibration processing unit 12 determines that a new target cannot be generated from the provisional target F'(x), and generates the target G(x) using the above-mentioned equation (6). Then, the target determining unit 127 of the calibration processing unit 12 determines the target G(x) generated by the second target generating unit 126 as the new target.

[0091] FIG. 11(a) shows the position of the connection point when a new target F(x) is determined when the maximum gradation value is set so that the Lab distance is equal to or greater than the predetermined Lab distance y1. In this state, it is indicated that there is still room to move the connection point toward x=0. FIG. 11(b) shows the position of the connection point when a new target F(x) is determined when the maximum gradation value is set so that the Lab distance is the same as the predetermined Lab distance y1. In this state, the connection point is located near x=0, indicating that it cannot be moved any further, and the predetermined Lab distance y1 indicates the limit of the Lab distance at which the provisional target F'(x) can be determined as the new target F(x). FIG. 11(c) shows the case where a new target cannot be determined using the provisional target F'(x) when the maximum gradation value is set so that the Lab distance is less than the predetermined Lab distance y1, and the new target is determined using the target G(x) generated based on the ratio of the target F"(x) using the above-mentioned equation (6).

[0092] Then, the process proceeds to step S150.

[0093] <Step S149> If the determination unit 125 determines that the gradation value C of the connection point is not near x=0, the first target generation unit 124 moves the connection point on the existing target E(x) by a predetermined amount toward x=0, and then returns to step S144.

[0094] <Step S150> The table creation unit 128 of the calibration processing unit 12 creates a γ table, which is a TRC for correcting gradation values, using a graph (a graph of interpolated gradation characteristics before calibration) obtained by interpolating the Lab distances for the colorimetric values of the calibration chart CC converted by the conversion unit 123, and a new target (shown as F(x) in FIG. 12(a)) determined by the target determination unit 127. That is, the table creation unit 128 sets the gradation values corresponding to the colorimetric values of the calibration chart CC as input gradation values (in) (first gradation values), and creates a γ table (an example of correction information) by determining the output gradation values (out) (second gradation values) for the input gradation values. Specifically, as shown in FIG. 12(a), the table creation unit 128 finds point P3 on the graph of the interpolated gradation characteristics that has the same Lab distance as point P2 on F(x), because the Lab distance of point P1 on the graph of the interpolated gradation characteristics corresponds to the input gradation value (in) corresponding to the colorimetric value of the calibration chart CC is different from the Lab distance of point P2 on F(x) as the new target. Then, the table creation unit 128 sets the gradation value of point P3 as the output gradation value (out) for the input gradation value (in) and performs this correspondence over the entire gradation value range from 0 to 100% to create a graph that associates input gradation values with output gradation values, as shown in FIG. 12(b), i.e., a γ table as a TRC for correcting gradation values. The table creation unit 128 then sends the created γ table to the image processing unit 11.

[0095] If this is the first calibration process by the calibration processing unit 12, the colorimetric values and new target can be stored in the auxiliary storage device 505 or the like, and can be referenced when the user subsequently outputs an image with the same color tone.

[0096] Furthermore, since the above-described calibration process is a calibration that uses Lab values and not density, it can also be applied to colors other than process colors such as orange and green, which do not have density specifications other than the conventional CMYK process colors.

[0097] As described above, in the information processing device 10 according to this embodiment, the first acquisition unit 121 acquires the colorimetric values of multiple single-color patches of the calibration chart CC read by the colorimetric device 40 and printed out by the image forming device 30, the second acquisition unit 122 acquires the maximum gradation value preset according to the paper, the conversion unit 123 converts the colorimetric values, the maximum gradation value, and the colorimetric values of existing targets, which are characteristics of ideal color values for the gradation values, into Lab distances, respectively, and the target determination unit 127 determines, as a new target, a target (F(x) or G(x)) that is generated based on the existing targets converted into Lab distances and passes through a point determined by the Lab distance corresponding to the maximum gradation value. This allows the new target to be generated using the maximum gradation value determined according to the paper, thereby improving adaptability to various papers with different printing characteristics while ensuring gradation reproducibility (gradation).

[0098] Furthermore, in the information processing device 10, the first target generation unit 124 generates a temporary target that passes through a point determined by the Lab value corresponding to the maximum gradation value based on the existing target converted to Lab distance, the determination unit 125 determines whether or not the following conditions are met: that there is a portion of the temporary target that follows the existing target (Condition 1), and that the portion of the temporary target other than the portion that follows has gradation (Condition 2).If the determination unit 125 determines that the temporary target satisfies both (Condition 1) and (Condition 2), the target determination unit 127 determines the temporary target as a new target.As a result, the target is generated in a way that follows the existing target as much as possible, and gradation in highlight areas can be ensured by using an appropriate existing target.

[0099] Each function of the above-described embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, and devices such as an ASIC, a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or a conventional circuit module designed to execute each function described above.

[0100] Furthermore, the programs executed by the information processing device 10 and the host computer 20 of the above-described embodiment may be configured to be provided in a state that they are pre-installed in a ROM or the like.

[0101] In addition, the programs executed by the information processing device 10 and host computer 20 of the above-described embodiments may be configured to be provided as a computer program product by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory), a flexible disk (FD), a CD-R (Compact Disk-Recordable), or a DVD (Digital Versatile Disk).

[0102] The programs executed by the information processing device 10 and the host computer 20 of the above-described embodiments may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. The programs executed by the information processing device 10 and the host computer 20 of the above-described embodiments may be provided or distributed via a network such as the Internet.

[0103] Furthermore, the programs executed by the information processing device 10 and the host computer 20 of the above-described embodiments have a modular structure including each of the functional units described above, and in actual hardware, the CPU (processor) reads the program from the ROM and executes it, thereby loading each of the functional units described above onto the main memory device, and each functional unit is generated on the main memory device. [Explanation of symbols]

[0104] 1. Information Processing Systems 10. Information processing equipment 11 Image processing section 12 Calibration processing section 20 Host Computer 30 Image forming device 40 Colorimetric device 111 Rasterization processing unit 112 Color rendering processing unit 113 Color separation processing section 114 Halftone Processing Unit 121 First acquisition part 122 Second Acquisition Department 123 Conversion Unit 124 First target generation unit 125 Judgment section 126 Second Target Generation Unit 127 Target Determination Unit 128 Table Creation Department 501 CPU 502 ROM 503 RAM 505 Auxiliary storage 506 Recording Media 507 Media Drive 508 Display 509 Network I / F 510 Bus Line 511 keyboard 512 Mouse 513 DVD 514 DVD drive 1000 Maximum gradation value setting screen 1001 Setting method selection section 1002 Maximum value input section 1003 Enter button CC calibration chart VC visual chart [Prior art documents] [Patent documents]

[0105] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-263345 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-116721

Claims

1. a first acquisition unit that acquires colorimetric values of a plurality of single-color patches of a first chart that is read by a colorimetric device and printed out by an image forming apparatus; a second acquisition unit that acquires a maximum gradation value that is preset according to the paper; a conversion unit that converts the color measurement value, the maximum gradation value, and the color specification value in a first target, which is a characteristic of an ideal color specification value for the gradation value, into predetermined color values, respectively; a determination unit that determines, as a second target, a characteristic that passes through a point determined by a color value corresponding to the maximum gradation value, generated based on the first target converted into the predetermined color value; An image processing device comprising:

2. 2. The image processing device according to claim 1, further comprising a creation unit that creates correction information for correcting a first gradation value of image data to be printed by the image forming device to a second gradation value using a color value corresponding to the colorimetric value and the second target.

3. a first generation unit that generates a third target, which is a provisional target that passes through a point determined by a color value corresponding to the maximum gradation value, based on the first target converted into the predetermined color value; a determination unit that determines whether or not a first condition that a portion of the third target that follows the first target exists and a second condition that a portion of the third target other than the portion that follows the first target has gradation are satisfied; Furthermore, The image processing device according to claim 1 , wherein the determination unit determines the third target as the second target when the determination unit determines that the third target satisfies both the first condition and the second condition.

4. a second generation unit configured to, when the determination unit has not found a third target that satisfies both the first and second conditions, generate a fourth target that is expressed as a ratio of a color value for each gradation value of a shape of a portion of the third target whose gradation value is near 0 to a color value for a maximum gradation value of the shape, The image processing device described in claim 3, wherein the determination unit determines the fourth target generated by the second generation unit as the second target when the judgment unit does not find a third target that is determined to satisfy both the first condition and the second condition.

5. The image processing apparatus according to claim 2 , wherein the second acquisition unit acquires the maximum gradation value input from an input device based on a second chart printed out by the image forming apparatus.

6. 6. The image processing device according to claim 1, wherein the single color is at least one of a process color and a color other than a process color.

7. 3. The image processing device according to claim 2, wherein the creation unit creates the correction information by setting a gradation value for the colorimetric value as the first gradation value, and setting a gradation value corresponding to a color value in a gradation characteristic that associates a color value corresponding to the colorimetric value with a gradation value corresponding to the colorimetric value, the color value being the same as the color value corresponding to the first gradation value in the second target, as the second gradation value.

8. 8. The image processing device according to claim 1, wherein the predetermined color value is a distance from the Lab value of paper white for the Lab values corresponding to the color measurement value, the maximum gradation value, and the color specification value in the first target.

9. the color measurement device that reads the first chart; the image forming apparatus applying correction information using the second target; An image processing device according to any one of claims 1 to 8; An image processing system having:

10. a first acquisition step of acquiring colorimetric values of a plurality of single-color patches of a first chart read by a colorimetric device; a second acquisition step of acquiring a maximum gradation value that is preset according to the paper; a conversion step of converting the color measurement value, the maximum gradation value, and the color specification value in a first target, which is a characteristic of an ideal color specification value for the gradation value, into predetermined color values, respectively; a determining step of determining, as a second target, a characteristic that passes through a point determined by a color value corresponding to the maximum gradation value, generated based on the first target converted into the predetermined color value; An image processing method comprising:

11. On the computer, a first acquisition step of acquiring colorimetric values of a plurality of single-color patches of a first chart read by a colorimetric device; a second acquisition step of acquiring a maximum gradation value that is preset according to the paper; a conversion step of converting the color measurement value, the maximum gradation value, and the color specification value in a first target, which is a characteristic of an ideal color specification value for the gradation value, into predetermined color values, respectively; a determining step of determining, as a second target, a characteristic that passes through a point determined by a color value corresponding to the maximum gradation value, generated based on the first target converted into the predetermined color value; A program to execute.

Images