Printing systems, printing methods, and programs

Abstract

To provide a printing system, a printing method and program configured to estimate and visualize a color difference from a color reference in a printing process of a print job with high accuracy, and allow an operator to accurately confirm color reproduction quality of a printed matter.SOLUTION: In an image forming apparatus 4, an image processing unit is configured to: calculate an initial color difference between a reference color and a device-independent measured color value of a first output image which is output based on print job data in a pre-print process of a print job; calculate a color variation during printing, based on a pre-print color value which is a color value of a color variation monitoring region of an image obtained by reading the first output image through a reading unit which reads a device-dependent image and a device-dependent color value obtained by reading a second output image output based on the print job data in an actual print process through the reading unit; calculate an in-printing color difference which is a color difference between the reference color and the device-dependent color value in the actual print process, based on the initial color difference and the color variation during printing; and display the initial color difference and the in-printing color difference on a display unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a printing system, a printing method, and a program. [Background technology]

[0002] For printing color standards, international standards such as ISO 12647-7 and Japan Color for sheet-fed printing (examples of color standards) are defined. Certification systems that guarantee a certain tolerance range for these color standards have also been implemented, and color management methods that comply with color standards are becoming commonplace.

[0003] On the other hand, a technology has been developed that allows users to understand color variations in the output image by reading the output image (printed material) that is produced based on image data during the execution of a print job using a reading unit (such as a general line sensor) installed in the image forming apparatus, and displaying the changes in the color value data on the user interface. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, since color standards are defined based on measurements taken with a spectrophotometer, methods that estimate color differences from RGB values, which depend on the reading device (reading unit), such as color variation monitoring devices, cannot convert to accurate Lab values. As a result, errors in the estimation model have a significant impact, making it impossible to accurately verify the color reproduction of printed materials.

[0005] The present invention has been made in view of the above, and aims to provide a printing system, printing method, and program that can accurately estimate and visualize the color difference with respect to a color standard in the printing process of a print job, and enable an operator to accurately confirm the color reproduction quality of the printed material. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, the present invention provides: a monitoring area setting unit that sets a color variation monitoring area of ​​a first output image output based on print job data in the pre-printing process of a print job; a color measurement unit that reads device-independent color measurement values ​​from the first output image; a pre-print color difference calculation unit that calculates the initial color difference between the device-independent color measurement values ​​and a reference color; a reading unit that reads a device-dependent image from the first output image and a second output image output based on print job data in the main printing process of the print job; and the reading unit The device includes: a storage control unit that reads an image from a first output image and obtains the color value of the color variation monitoring area and records it as a pre-print color value; a color variation amount calculation unit that calculates the amount of color variation based on the device-dependent color value read from the second output image by the reading unit and the pre-print color value; a color difference calculation unit that calculates the color difference during printing, which is the color difference between the device-dependent color value and the reference color in the main printing process, based on the initial color difference and the amount of color variation during printing; and a color difference display control unit that displays the initial color difference and the color difference during printing on a display unit. [Effects of the Invention]

[0007] According to the present invention, the color difference from the color standard in the printing process of a print job can be estimated and visualized with high accuracy, and the color reproduction quality of the printed material can be accurately confirmed by the operator. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the configuration of an image forming system to which the printing system according to this embodiment is applied. [Figure 2] Figure 2 is a block diagram showing an example of the configuration of the image processing unit in the image forming apparatus according to this embodiment. [Figure 3] Figure 3 is a sequence diagram showing an example of the printing operation flow in the image forming apparatus according to this embodiment. [Figure 4] Figure 4 is a flowchart showing an example of the pre-printing process flow in the image forming apparatus according to this embodiment. [Figure 5] FIG. 5 is a diagram for explaining an example of a color monitoring area setting screen displayed in the printing system according to the present embodiment. [Figure 6] FIG. 6 is a diagram showing an example of data stored in a data storage unit included in the image forming apparatus according to the present embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of the printing process in the image forming apparatus according to the present embodiment. [Figure 8] FIG. 8 is a diagram showing an example of data stored in a data storage unit included in the image forming apparatus according to the present embodiment. [Figure 9] FIG. 9 is a diagram for explaining an example of a color difference display screen displayed in the printing system according to the present embodiment. Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of a printing system, a printing method, and a program will be described in detail with reference to the accompanying drawings.

[0010] FIG. 1 is a diagram showing an example of the configuration of an image forming system to which the printing system according to the present embodiment is applied. As shown in FIG. 1, the image forming system according to the present embodiment includes a user PC 1, a spectrocolorimeter 3, a display device 6, a DFE (Digital Front End) controller 5, an image forming apparatus 4, and the like.

[0011] The user PC 1 is used when an operator operates this image forming system. The spectrocolorimeter 3 spectrocolorimetrically measures a printed matter. The display device 6 inputs and displays various types of information. The DFE controller 5 controls print data via a network. The image forming apparatus 4 receives print data from the DFE controller 5 and forms an image on a sheet (an example of a recording medium) 7.

[0012] The image forming apparatus 4 comprises a grayscale processing unit 8, a printer engine 9, a reading sensor 10, an image processing unit 11, a printer control unit 12, and a data storage unit 13. The grayscale processing unit 8 converts the print data into a number of grayscale levels that can be output by the printer engine 9. The printer engine 9 forms a print image on the paper 7. That is, the printer engine 9 is an example of a printing unit that prints an output image onto a recording medium such as the paper 7 based on print data (an example of print job data). The printer control unit 12 controls the printer engine 9. The reading sensor 10 reads the print image formed by the printer engine 9 inline. The reading sensor 10 is an example of a reading unit that reads device-dependent color values ​​from the output image printed on the paper 7.

[0013] The image processing unit 11 refers to the image read by the reading sensor 10 and detects the amount of color variation (density variation, hue variation, etc.) in the printed image. In other words, the image processing unit 11 is an example of an image processing unit that processes device-dependent color values ​​read by the reading sensor 10. The data storage unit 13 stores various data, such as data related to the amount of color variation detected by the image processing unit 11.

[0014] The printer engine 9 is a device that prints an image onto a recording medium such as paper 7 based on print data output from the image processing unit 11, using, for example, four colorants (toner, ink, etc.) such as cyan (C), magenta (M), yellow (Y), and black (K). The printer engine 9 can use an image forming engine such as an electrophotographic or inkjet type.

[0015] The reading sensor 10 is an image input device such as a line sensor or camera that can quickly read the colors of the output image printed on the paper 7, and generally reads device-dependent RGB values. The data storage unit 13 has an HDD (Hard Disk Drive) or SSD (Solid State Drive), etc., and stores programs, operation history information, monitoring information, etc.

[0016] User PC1 runs various software, such as software for creating color profiles or control software for the DFE controller 5. User PC1 can be a laptop computer, tablet, smartphone, or the like.

[0017] The spectrophotometer 3 is generally a spot-measurement type, but a line-measurement spectrophotometer equipped with multiple spectroscopic sensors in a line can also be used. The spectrophotometer 3 is an example of a colorimeter that reads device-independent color values ​​from an output image printed on paper 7. Alternatively, the spectrophotometer 3 may measure device-independent color values ​​from a color variation monitoring area of ​​the output image that is output based on print data in the pre-printing process of a print job.

[0018] The DFE controller 5 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), etc., and performs input and output of print jobs. In this embodiment, the DFE controller 5 is described as a device independent of the image forming apparatus 4, but it may also be built into the image forming apparatus 4.

[0019] The display device 6 is a display device used to operate the image forming apparatus 4 and to display its operating status. The display device 6 is, for example, a touch panel display, and has a configuration in which a touch panel is superimposed on the front of a display such as a liquid crystal display.

[0020] Figure 2 is a block diagram showing an example of the configuration of the image processing unit of the image forming apparatus according to this embodiment. In this embodiment, the image processing unit 11 includes a monitoring area setting unit 111, a pre-print color difference calculation unit 112, a color variation amount calculation unit 113, a color difference calculation unit 114 during printing, a color difference display control unit 115, a storage control unit 116, and a print stop unit 117, as shown in Figure 2.

[0021] The monitoring area setting unit 111 sets the color variation monitoring area of ​​the output image (an example of a first output image) that is printed (output) on the paper 7 based on the print data in the pre-printing process of a print job. The pre-print color difference calculation unit 112 calculates the color difference (initial color difference) between the device-independent color measurement value by the spectrophotometer 3 and the reference color. The memory control unit 116 functions as an example of a reference color difference recording unit that records the initial color difference in a storage unit such as the data storage unit 13. The memory control unit 116 also functions as an example of a color information storage control unit that obtains the color value of the color variation monitoring area from the image read from the first output image by the reading sensor 10 and records (saves) the obtained color value as a pre-print color value in a storage unit such as the data storage unit 13.

[0022] The color variation amount calculation unit 113 calculates the color variation amount based on the device-dependent color value read by the reading sensor 10 from the output image (an example of a second output image) printed (output) on the paper 7 based on the print data during the main printing process of the print job, and the pre-print color value stored in the data storage unit 13. The in-print color difference calculation unit 114 calculates the in-print color difference, which is the color difference between the device-dependent color value and the reference color during the main printing process, based on the initial color difference and the color variation amount during printing. In this embodiment, the in-print color difference calculation unit 114 calculates the in-print color difference based on the initial color difference between the measured color value in the color standard set by the user and the reference color.

[0023] The color difference display control unit 115 displays the initial color difference (pre-print color difference) and the color difference during printing on a display unit such as the display device 6. This allows for highly accurate estimation and visualization of the color difference relative to the color standard during the printing process of a print job, enabling the operator to accurately confirm the color reproduction quality of the printed material.

[0024] The print stop unit 117 stops the printing process if the amount of color variation in the main printing process exceeds a predetermined threshold. Specifically, the print stop unit 117 determines whether the amount of color variation, based on device-independent colorimetric values ​​in a color standard set by the user, exceeds a predetermined threshold. Then, the print stop unit 117 stops the printing process if the amount of color variation exceeds the predetermined threshold.

[0025] Figure 3 is a sequence diagram showing an example of the printing operation flow in the image forming apparatus according to this embodiment. The user operates the user PC 1 to send job data (print data) to the DFE controller 5 (step S301), and then instructs the DFE controller 5 to print (step S302). Here, the job data may be PDL data described in a page description language (PDL) such as PDF (Portable Document Format).

[0026] The DFE controller 5 performs image processing such as color conversion and rasterization on the received job data to generate print image data in bitmap format, and transmits the generated print image data, job ID, page ID, and part ID to the image forming apparatus 4 (step S303). Here, the color conversion process is a process of converting PDL data expressed in the CMYK color space to another CMYK color space using a 4D LUT (Look Up Table) or the like in order to obtain the target output value. Here, the rasterization process is a process of converting PDL data into bitmap image data. Here, the bitmap image data is image data of rectangles in which colored dots are arranged regularly. The DFE controller 5 may perform the color conversion process after the rasterization process.

[0027] The gradation processing unit 8 adds the print image data, job ID, page ID, and part ID received from the DFE controller 5 and sends them to the image processing unit 11 (step S304). Next, the gradation processing unit 8 performs gradation processing on the print image data, converting each pixel of the bitmap image data into a number of gradations that can be represented by the printer engine 9 (step S305), and controls printing by the printer engine 9 (step S306). The printer engine 9 prints the output image on the paper 7 based on the print image data with the converted gradation (step S307).

[0028] The reading sensor 10 optically reads the output image formed on the paper 7 by the printer engine 9 (step S307), generates a scan image (read data) in bitmap format, and transmits it to the image processing unit 11 (step S308).

[0029] The image processing unit 11 aligns the print image data with the scanned image (step S309) and acquires color monitoring area information indicating the color variation monitoring area within the print image data (step S310). Furthermore, the image processing unit 11 estimates the amount of color variation in the color variation monitoring area based on the print image data and the scanned image (step S311) and stores the estimated amount of color variation in the data storage unit 13 (step S312). The color difference from the standard color reference (color difference during printing) is calculated page by page during actual printing by referring to the pre-print color difference information (initial color difference) measured in the pre-printing process.

[0030] Figure 4 is a flowchart showing an example of the pre-printing process in the image forming apparatus according to this embodiment. First, the image processing unit 11 performs color adjustment of the output device (printer engine 9) (step S401). Specifically, the image processing unit 11 performs calibration processing of the CMYK gradation characteristics of the printer engine 9, updates the output profile for color conversion, etc. Here, the calibration process involves, for example, instructing the calibration function on the screen of the display device 6 to output a predetermined chart from the image forming apparatus 4, and using the data read by the reading sensor 10 from the predetermined chart to control the TRC (Tone Reduction Curve) provided in the gradation processing unit 8 so that the gradation characteristics of the CMYK monochromatic colors match the target gradation characteristics. When creating a profile, a dedicated chart is output and measured with the spectrophotometer 3 to create an ICC profile including a LUT (Look Up Table) that associates CMYK and Lab. The created ICC profile is registered with the DFE controller 5 and used when setting up a job.

[0031] Next, the monitoring area setting unit 111 sets the color variation monitoring area of the print job based on the input from the color monitoring area setting screen 301 (see FIG. 5) (step S402). Here, the color variation monitoring area is a rectangular area specified by the coordinate positions in the X and Y directions and the size. When the color variation monitoring area is set, the pre-print color difference calculation unit 112 calculates and registers the colorimetric values (L std , a std , b std ) for each color variation monitoring area.

[0032] When the setting of the color variation monitoring area is completed, the printer engine 9 performs a test print of the print job according to the operator's instruction (step S403). If the image quality of the test printed image is unacceptable as a result of the test print (step S404: No), the image processing unit 11 returns to step S401 to readjust the image quality.

[0033] On the other hand, if the image quality is acceptable (step S404: Yes), the reading sensor 10 acquires the color values of the color variation monitoring area in the output image printed in step S403 (step S405). In the case of a test print, the storage control unit 116 records the color values (color values) of all the color variation monitoring areas for the print job ID as pre-print color information (pre-print color values) in the data storage unit 13.

[0034] Next, the user operates the user PC1 to measure the color of the color variation monitoring area with the spectrocolorimeter 3 (step S406). When using a line measurement type spectro sensor as the spectrocolorimeter 3, spectral data as a surface is measured, and the colorimetric values corresponding to the coordinates of the color variation monitoring area are calculated and obtained.

[0035] Next, the pre-print color difference calculation unit 112 compares the colorimetric values (L i , a i , b i ) measured in step S406 with the colorimetric values of the reference color (L std , a std , b stdThe color difference ΔE (initial color difference) is calculated (step S407), and the color difference (initial color difference) is linked to the color variation monitoring area and stored in the data storage unit 13 as the pre-print color difference (initial color difference). Here, the color difference ΔE is generally calculated using CIEDE2000, but the conventional CIE76 color difference, which is defined as the Euclidean distance in Lab space, may also be used.

[0036] The image processing unit 11 determines whether the color difference ΔE obtained in step S407 is within a predetermined tolerance color difference (step S408). If the color difference ΔE is greater than the tolerance color difference (step S408: No), the color adjustment is repeated (step S401). Here, the tolerance color difference is a preset value, but it may be changed for each print job. On the other hand, if the color difference ΔE is within the tolerance color difference (step S408: Yes), the image processing unit 11 terminates the pre-print processing.

[0037] Figure 5 is a diagram illustrating an example of a color monitoring area setting screen displayed in the printing system according to this embodiment. In this embodiment, as shown in Figure 5, the monitoring area setting unit 111 displays a color monitoring area setting screen 301 on the operation screen of the user PC 1 and accepts the setting of the color fluctuation monitoring area on the color monitoring area setting screen 301.

[0038] The color monitoring area setting screen 301 includes a preview image 302 of the print data, a specification screen 303 for specifying (setting) the color variation monitoring area, and a list 304 of the set color variation monitoring areas. The preview image 302 can be enlarged or reduced using the button 306. Also, since the image usually differs depending on the page of the print job, the page for which the color variation monitoring area is set is specified in the page input field 307.

[0039] Print data typically includes CMYK data, which cannot be directly displayed on a screen. Therefore, the print data preview image 302 is simulated and displayed on the screen after rasterizing the print data and performing color conversion. For color conversion, a standard profile such as JapanColor is set as the source profile 308 for the CMYK data, and a display profile such as sRGB is specified as the output profile, and the result of the profile conversion process is displayed.

[0040] The color variation monitoring area is a rectangular area defined by its coordinate position in the X and Y directions and its size. It can be directly entered on the specification screen 303, or the area shown by reference numeral 310 can be directly specified as the color variation monitoring area by operating the mouse on the preview image 302. One or more color variation monitoring areas are set for each page, and each page is assigned a monitoring area ID to identify the color variation monitoring area.

[0041] Once the color variation monitoring area settings for all pages are complete, when the "Save" button is pressed, the monitoring area setting unit 111 saves the color monitoring area information indicating the color variation monitoring area to the data storage unit 13. At this time, the measured color value (L) of the reference color is saved. std ,a std ,b std The colorimetric value of the reference color is calculated and stored in the data storage unit 13 along with the color monitoring area information. The colorimetric value of the reference color is obtained by rasterizing the print data to generate a bitmap format CMYK image, then averaging the CMYK values ​​of the color variation monitoring area to obtain the average CMYK value, which is the average CMYK value of the color variation monitoring area. Then, the average CMYK value is converted to obtain the colorimetric value of the reference color (L std ,a std ,b std The color conversion process can be calculated by performing interpolation operations using a color conversion table that associates CMYK values ​​and Lab values ​​included in the set source profile 308.

[0042] Additionally, when the "Measure Color" button is pressed, an application for measuring color using the spectrophotometer 3 is launched to measure the color variation monitoring area. Once the color measurement of the color variation monitoring area is complete, the memory control unit 116 stores the color difference between the measured color value and the measured color value of the reference color as the pre-print color difference in the data storage unit 13.

[0043] Figure 6 shows an example of data stored in the data storage unit of the image forming apparatus according to this embodiment. In this embodiment, as shown in Figure 6, the data storage unit 13 stores color monitoring area information, the average CMYK value of the color variation monitoring area, the measured color value of the reference color, the pre-print color difference, the pre-print color information, and the color difference. The color monitoring area information includes the area No. of the color variation monitoring area, the part number (part ID) and page number (page ID) of the part containing the color variation monitoring area. In the pre-print process, the part ID is set to 0. The color monitoring area information may also include coordinate information of the color variation monitoring area.

[0044] The color information for the color variation monitoring area includes the average CMYK value of the color variation monitoring area, the measured color value of the reference color, the pre-print color difference, the pre-print color value (pre-print color value), and the color difference.

[0045] Figure 7 is a flowchart showing an example of the flow of the printing process in the image forming apparatus according to this embodiment. When the printing process is started and printing is performed according to the printing operation in Figure 3, the reading sensor 10 reads the output image printed on the paper 7 and inputs the image data of the read output image (read image data) to the image processing unit 11 (step S701). The image processing unit 11 determines the reading value of the color variation monitoring area included in the input read image data.

[0046] The image processing unit 11 performs alignment processing between the print data and the input read image data (step S702). Here, the alignment processing corrects positional misalignment, skew, scaling, local distortion, etc., between the image data read by the reading sensor 10 from the output image (read image data) and the print data (raster image). More specifically, the alignment processing detects the paper edge of the read image data, corrects the position and skew of the read image data to match the paper edge of the print data, and deforms the feature points of the read image data using template matching to match the print data and aligns their positions.

[0047] Next, the color variation amount calculation unit 113 calculates the average color value of the color variation monitoring area by averaging the color values ​​of the pixels included in the coordinates of the color variation monitoring area in the read image data that has undergone alignment processing (step S703).

[0048] Next, the color variation amount calculation unit 113 calculates the color variation amount of the color variation monitoring area (step S704). Here, the color variation amount is, for example, L * a * b * ΔL of brightness difference in color space * , chromaticity difference Δa * , chromaticity difference Δb * The following can be used. ΔL * Δa * Δb * These are L * a * b * L in color space * Ingredients, a * ingredient, b * This represents the difference in components. Next, ΔL * Δa * Δb *The calculation method will be explained below. The color variation amount calculation unit 113 accesses the data storage unit 13 and obtains the pre-print color value associated with the job ID contained in the color monitoring area information in the data storage unit 13. Then, the color variation amount calculation unit 113 uses matrix conversion or a 3D LUT (Look Up Table) to convert the RGB data representing the pre-print color value, thereby calculating a device-independent L * a * b * Convert to a value. Similarly, the color variation amount calculation unit 113 also converts the RGB value (color value) obtained in step S703 to an L * a * b * Convert to a value. Then, the color variation amount calculation unit 113 calculates the two L * a * b * The difference between the values ​​ΔL(diff), Δa(diff), and Δb(diff) is calculated as the amount of color variation.

[0049] Next, the printing color difference calculation unit 114 calculates the color difference ΔE from the standard color reference during the printing process (step S705). Specifically, the printing color difference calculation unit 114 takes the color difference (initial color difference) obtained using the spectrophotometer 3 in the pre-printing process as (ΔL(pre), Δa(pre), Δb(pre)) and the amount of color variation during printing as (ΔL(diff), Δa(diff), Δb(diff)), and uses the following equations (1) to (3) to calculate the color difference ΔE (ΔL(job), Δa(job), Δb(job)) from the standard color reference.

number

[0050] The color difference ΔE is calculated from the above ΔL(job), Δa(job), and Δb(job). Generally, CIEDE2000 is used for the color difference ΔE, but the conventional CIE76 color difference, defined as the Euclidean distance in Lab space, may also be used. Once the color difference calculation unit 114 calculates the color difference ΔE for all color variation monitoring areas within the page (read image data), it transmits the result to the data storage unit 13 for recording (step S706). Next, the image processing unit 11 determines whether the print job is complete or not (step S707). If the print job is not complete (step S707: No), the process returns to step S701. On the other hand, if the print job is complete (step S707: Yes), the image processing unit 11 terminates this printing process.

[0051] Figure 8 shows an example of data stored in the data storage unit of the image forming apparatus according to this embodiment. In this embodiment, as shown in Figure 8, the data storage unit 13 stores color monitoring area information, average CMYK value of color variation monitoring area, color measurement value of reference color, pre-print color difference, pre-print color information, and color difference.

[0052] Figure 9 is a diagram illustrating an example of a color difference display screen displayed in the printing system according to this embodiment. In this embodiment, the color difference display control unit 115 displays the color difference display screen 501 on the display device 6, as shown in Figure 9. The color difference display screen 501 includes, as shown in Figure 9, a pull-down menu 502 for specifying the color standard, a pull-down menu 503 for specifying the color difference display method, a color difference display screen 504 that displays the color difference of all color variation monitoring areas in a graph, an area 505 that displays a preview image of the specified page, a color difference display screen 506 that displays the color difference of the specified color variation monitoring area, and the like.

[0053] The color difference display screens 504 and 506 show a graph where the horizontal axis represents the number of printed pages and the vertical axis represents the color difference, as well as a dotted line 520 indicating the acceptable color difference, and color differences 510, 511, etc., for each print job. In addition, the color difference display screen 504 aggregates and displays the color difference (color variation information) of all print jobs printed over a certain period. The color difference 510 indicates the pre-print color difference (initial color difference) measured by color measurement in the pre-printing process.

[0054] The pre-print color difference shows the result of aggregating all color variation monitoring areas using the method specified in 503. For example, if "Show maximum color difference" is selected, the color difference display screens 504 and 506 will plot the largest color difference among all color variation monitoring areas. Other color difference display methods that can be selected include "Show average value" and "Show 95% cumulative color difference".

[0055] The color difference plot 511 on the color difference display screen 504 represents the color difference ΔE during printing. The color difference ΔE during printing corresponds to the color difference obtained by adding the amount of color variation during printing to the color difference measured before printing, as explained in step S704 of Figure 7, and plots the maximum value of the color difference ΔE in all color variation monitoring areas. The color difference ΔE is updated as needed during printing, and if the color difference ΔE in the color variation monitoring area exceeds the allowable value, the color difference display control unit 115 pauses printing and displays a warning screen to allow the user to choose whether to continue or cancel printing.

[0056] Furthermore, the pull-down menu 502 allows you to specify (set) the color standard when calculating the color difference ΔE. For example, the pull-down menu 502 allows you to select a color standard defined as a standard, such as "JapanColor," "Euroscale," or "GRACol." Also, if "Proof Printing" is selected as the color standard, the output from the pre-printing process will be used as the color standard, and the pre-print color difference will be set to 0. The color difference display screen 506 displays only the color variation (color difference ΔE) of a specific color variation monitoring area for a specific job.

[0057] Thus, according to this embodiment of the printing system, the color difference from the color standard in the printing process of a print job can be estimated and visualized with high accuracy, allowing the operator to accurately confirm the color reproduction quality of the printed material.

[0058] The program executed in the image forming apparatus 4 of this embodiment is provided pre-installed in ROM (Read Only Memory) or the like. The program executed in the image forming apparatus 4 of this embodiment may also be provided as an installable or executable file recorded on a computer-readable recording medium such as a CD-ROM, flexible disk (FD), CD-R, or DVD (Digital Versatile Disk).

[0059] Furthermore, the program executed by the image forming apparatus 4 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. Alternatively, the program executed by the image forming apparatus 4 of this embodiment may be provided or distributed via a network such as the Internet.

[0060] The program executed in the image forming apparatus 4 of this embodiment is configured as a module including the above-mentioned parts (monitoring area setting unit 111, pre-print color difference calculation unit 112, color variation amount calculation unit 113, in-print color difference calculation unit 114, color difference display control unit 115, memory control unit 116, and print stop unit 117). In actual hardware, a processor such as a CPU (Central Processing Unit) reads the program from the ROM and executes it, loading the above-mentioned parts onto the main memory, and generating the monitoring area setting unit 111, pre-print color difference calculation unit 112, color variation amount calculation unit 113, in-print color difference calculation unit 114, color difference display control unit 115, memory control unit 116, and print stop unit 117 on the main memory.

[0061] In the above embodiment, the image forming apparatus 4 of the present invention is described as being applied to a multifunction device having at least two functions from among a copy function, a printer function, a scanner function, and a facsimile function. However, it can be applied to any image forming apparatus such as a copier, printer, scanner, or facsimile device. [Explanation of symbols]

[0062] 1 User PC 3 Spectrophotometer 4. Image forming apparatus 5 DFE Controller 6 Display device 8-level grayscale processing unit 9 Printer engine 10 Reading Sensors 11 Image Processing Unit 12 Printer Control Unit 13 Data Storage Unit 111 Monitoring area setting section 112 Pre-print color difference calculation unit 113 Color variation amount calculation unit 114 Color difference calculation unit during printing 115 Color difference display control unit 116 Memory Control Unit 117 Print stop section [Prior art documents] [Patent Documents]

[0063] [Patent Document 1] Japanese Patent Publication No. 2016-019143

Claims

1. A monitoring area setting unit sets a color variation monitoring area for the first output image that is output based on the print job data in the pre-printing process of a print job, A colorimeter that reads device-independent colorimetric values ​​from the first output image, A pre-print color difference calculation unit calculates the initial color difference between the device-independent color measurement value and a reference color. A reading unit reads a device-dependent image from the first output image and a second output image output based on the print job data in the main printing process of the print job. A storage control unit that obtains the color value of the color variation monitoring region from the image read from the first output image by the reading unit and records it as the color value before printing, A color variation amount calculation unit calculates the amount of color variation based on the device-dependent color value read from the second output image by the reading unit and the pre-print color value. A printing color difference calculation unit calculates the printing color difference, which is the color difference between the device-dependent color value and the reference color in the main printing process, based on the initial color difference and the amount of color variation during printing. A color difference display control unit that displays the initial color difference and the color difference during printing on a display unit, A printing system having

2. The printing system according to claim 1, wherein the printing color difference calculation unit calculates the printing color difference based on the initial color difference between the measured color value in a color standard set by the user and the reference color.

3. The printing system according to claim 1 or 2, wherein the colorimetric unit measures the device-independent colorimetric value from the color variation monitoring region of the first output image.

4. The system further includes a printing stop unit that stops the printing process when the amount of color variation in the aforementioned printing process exceeds a predetermined threshold. The printing system according to claim 2, wherein the printing stop unit determines whether the amount of color variation, based on the device-independent colorimetric value in the color standard set by the user, exceeds a predetermined threshold.

5. A printing unit that prints output images onto a recording medium based on print job data, A colorimeter unit reads device-independent color values ​​from the output image printed on the recording medium, A reading unit reads device-dependent color values ​​from the output image printed on the recording medium, The system includes an image processing unit that processes the device-dependent color values ​​read by the reading unit, The aforementioned image processing unit, A reference color difference recording unit records the initial color difference between the device-independent color measurement value read by the colorimeter unit and a reference color in the pre-printing process of a print job, where the first output image is output based on the print job data, A color information storage control unit records the device-dependent color values ​​read by the reading unit from the first output image as pre-print color values, A color variation amount calculation unit calculates the amount of color variation during printing based on the device-dependent color value read by the reading unit and the pre-print color value in the main printing process of a print job, A printing color difference calculation unit calculates the printing color difference by adding the color variation amount to the initial color difference, A color difference display control unit that displays the initial color difference and the in-print color difference on a display unit during the print job, A printing system having

6. A printing method performed by a printing device, A step in the pre-printing process of a print job to set a color variation monitoring area for the first output image that is output based on the print job data, A step of reading device-independent colorimetric values ​​from the first output image, A step of calculating the initial color difference between the device-independent colorimetric value and a reference color, A step of reading a device-dependent image from the first output image and the second output image output based on the print job data in the main printing process of the print job, A step of obtaining the color value of the color variation monitoring region from the image read from the first output image and recording it as the color value before printing, A step of calculating the amount of color variation based on the device-dependent color value read from the second output image and the pre-print color value, A step of calculating the in-print color difference, which is the color difference between the device-dependent color value and the reference color in the main printing process, based on the initial color difference and the amount of color variation during printing. A step of displaying the initial color difference and the color difference during printing on a display unit, Printing methods including [specific printing methods].

7. Computers, A monitoring area setting unit sets a color variation monitoring area for the first output image that is output based on the print job data in the pre-printing process of a print job, A pre-print color difference calculation unit calculates the initial color difference between a device-independent color measurement value read from the first output image by a color measurement unit and a reference color. A storage control unit that reads the first output image from the reading unit, obtains the color value of the color variation monitoring area from the image, and records it as the color value before printing, A color variation amount calculation unit calculates the amount of color variation based on the device-dependent color values ​​read by the reading unit from the second output image output based on the print job data in the main printing process of the print job, and the pre-print color values. A printing color difference calculation unit calculates the printing color difference, which is the color difference between the device-dependent color value and the reference color in the main printing process, based on the initial color difference and the amount of color variation during printing. A color difference display control unit that displays the initial color difference and the color difference during printing on a display unit, A program to make it work.

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