Image forming device, information processing method and program

Abstract

To enable color variation to be grasped in printing in a singular part.SOLUTION: An image forming device comprises: a master image generating part that generates a master image having theoretical color information in a case where a plurality of images to be printed in order are printed, for each of the images; a color difference calculating part that calculates a color difference between the master image and a scan image read out from a paper having the image printed thereon, for each of one or more partial regions in the master image corresponding to the image, for each image; and a color difference classifying part that calculates a difference between an average value of each master image and an average value of the whole of an aggregation of the color difference relating to the partial regions classified into the same color system, with respect to the aggregation.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, an information processing method, and a program. [Background technology]

[0002] Digital printing devices using electrophotography or inkjet printing, which are designed for high-volume printing, require stable output colors over continuous printing of hundreds or thousands of sheets. Stable management of reproduced colors is particularly important in use cases where the same document is repeatedly printed with only minor changes to the content every few pages, such as flyers or catalogs.

[0003] However, unlike full-scale commercial printing, the operating environment (e.g., temperature, humidity, etc.) in which these digital printing devices are used is not necessarily strictly controlled. Furthermore, printing a wide variety of documents involves many unavoidable instabilities, such as constantly changing toner and ink supply rates and machine conditions. This makes it difficult to stabilize the color of areas requiring strict color control, such as photographic areas on images of continuously printed documents, design drawings, and corporate logos. Even if the color of the printing device is adjusted in advance using calibration or other methods to achieve the desired color tone, leaving the printing device alone for even a few hours (by not printing or leaving the power off) can cause the adjusted color tone to change due to changes in machine conditions. If a job is printed after being left alone, the color tone of the initial printed material may not be the desired color tone when the continuous printing begins, and color fluctuations that occur during printing further alter the color tone. Completing printing while the color tone is still poorly balanced results in unusable printed material (waste paper) that is either unnecessary or discarded.

[0004] When a certain degree of stable control of output colors is required, it is necessary to frequently stop the machine and perform calibration operations. However, performing such calibration operations frequently can cause problems such as paper waste when printing a calibration chart, stopping print jobs at the user's request, and increasing the number of work hours required for calibration operations.

[0005] Therefore, a technology has been considered in the past that calculates the color difference in the same area between pages of the same number of pages per copy of a print job involving multiple copies, and determines whether to continue printing based on the calculated color difference (for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional technology, it is necessary to compare color differences in the same area between pages of the same number of pages per copy in multiple copies, making it difficult to apply this to a print job with a single copy setting.

[0007] The present invention has been made in view of the above points, and has as its object to make it possible to grasp color variations in printing a single copy. [Means for solving the problem]

[0008] To solve the above problem, the image forming apparatus has a master image generation unit that generates, for each of a plurality of images that are printed in sequence, a master image having theoretical color information when the image is printed; a color difference calculation unit that calculates, for each of one or more partial areas in the master image corresponding to the image, the color difference between the image and a scanned image read from paper on which the image is printed; and a color difference classification unit that calculates, for a set of color differences related to the partial areas that are classified into the same color family, the difference between the average value for each master image and the overall average value for the set. [Effects of the Invention]

[0009] It is possible to grasp color variations in single-copy printing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of the overall configuration of an image forming system according to an embodiment of the present invention; [Figure 2] 1 is a diagram illustrating an example of a hardware configuration of an image forming apparatus 100 according to an embodiment of the present invention. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of an image forming mechanism 4. [Figure 4] 1 is a diagram illustrating an example of a functional configuration of an image forming apparatus 100 according to an embodiment of the present invention. [Figure 5] FIG. 10 is a diagram for explaining extraction of a color measurement area. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure executed by the image forming apparatus 100. [Figure 7] FIG. 10 is a diagram illustrating an example of an output report. [Figure 8] FIG. 10 is a diagram showing an example of display of detailed information. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an example of the overall configuration of an image forming system according to an embodiment of the present invention. Image forming system 1 includes image forming device 100, user terminal 200, and server 201. Image forming device 100, user terminal 200, and server 201 are communicably connected via communication network 500.

[0012] Image forming apparatus 100 is an apparatus for forming an image, such as a color production printer, laser printer, or inkjet printer. Image forming apparatus 100 receives a plurality of image data (hereinafter referred to as "original data") to be printed in order from user terminal 200 or server 201, and prints an image on paper based on the received original data. Note that paper is an example of a transport medium on which an image is formed.

[0013] User terminal 200 is a terminal that receives an operation from a user and instructs printing of an image. Specifically, user terminal 200 transmits print job data including manuscript data to image forming apparatus 100 or server 201. That is, the print job data may be transmitted directly from user terminal 200 to image forming apparatus 100, or may be transmitted to image forming apparatus 100 via server 201.

[0014] When the server 201 receives print job data from the user terminal 200, the server 201 adds the print job data to a queue in a storage unit that stores print job data waiting to be printed. The server 201 extracts the print job data from the queue in the order in which the data was added to the queue or according to an appropriately set priority, and transmits the extracted print job data to the image forming apparatus 100.

[0015] The communication network 500 is a LAN (Local Area Network) or the Internet, etc., and is a network that realizes data communication.

[0016] Fig. 2 is a diagram showing an example of the hardware configuration of image forming apparatus 100 according to the embodiment of the present invention. As shown in Fig. 2, image forming apparatus 100 includes a CPU (Central Processing Unit) 101, memory 102, auxiliary storage device 103, network I / F 104, printer engine I / F 106, image forming mechanism 4, and scanner 27. Of these, CPU 101, memory 102, auxiliary storage device 103, network I / F 104, printer engine I / F 106, and scanner I / F 108 are connected to one another by bus 109 so as to enable data communication therebetween.

[0017] The CPU 101 is a processing unit that controls the overall operation of the image forming apparatus 100 .

[0018] The memory 102 is composed of a ROM (Read Only Memory) that stores programs such as firmware, and a RAM (Random Access Memory) that is used as a work area when the CPU 101 performs arithmetic processing.

[0019] The auxiliary storage device 103 is a storage device such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, and stores an operating system (OS), various programs, document data, color profiles, and the like.

[0020] The network I / F 104 is an interface for connecting to an external network (such as a LAN or the Internet). The network I / F 104 is compatible with, for example, Ethernet (registered trademark) and the TCP (Transmission Control Protocol) / IP (Internet Protocol) communication standard. The image forming apparatus 100 can perform data communication with external devices (such as a PC 200 and a server 201) via the network I / F 104.

[0021] The printer engine I / F 106 is an interface for communicably connecting to the image forming mechanism 4 that forms an image by electrophotography and prints the document data. The image forming mechanism 4 forms an image on a sheet P, which is a recording medium, based on the document data.

[0022] The scanner I / F 108 is an interface for communicatively connecting to the scanner 27 having the measurement sensor 45. The scanner 27 is a device that reads an image on the paper P using the function of the measurement sensor 45.

[0023] The hardware configuration of image forming apparatus 100 shown in FIG. 2 is an example, and other components may be included.

[0024] Fig. 3 is a diagram showing an example of the configuration of the image forming mechanism 4. As shown in Fig. 3, the image forming mechanism 4 includes a paper feed unit 2 that transports paper P, which is a recording medium, a transfer unit 5 that transfers a toner image formed on a transfer belt 47 based on input document data (input image) onto the paper P, a fixing unit 6 that fixes the image onto the paper P transferred by the transfer unit 5, a measurement sensor 45 that measures the reflection characteristics of the image fixed onto the paper P, and a paper discharge unit 7 that discharges the paper P to the outside.

[0025] The paper feed section 2 has a paper feed port 20 , a paper feed roller 21 , and a pair of registration rollers 22 .

[0026] The paper feed port 20 is an opening for feeding paper P into the image forming mechanism 4. The paper feed roller 21 is a roller that transports the paper P fed from the paper feed port 20 to the transfer unit 5. The registration roller pair 22 is a roller pair that sends the paper P transported from the paper feed roller 21 to the transfer unit 5 at a predetermined timing.

[0027] Image forming apparatus 100 has four process units 4Y, 4M, 4C, and 4K corresponding to the multiple basic colors of yellow (Y), magenta (M), cyan (C), and black (K) for transferring toner images onto transfer belt 47. Process units 4Y, 4M, 4C, and 4K have drum-shaped photoreceptors 40Y, 40M, 40C, and 40K, respectively, which serve as image carriers. Since process units 4Y, 4M, 4C, and 4K all have the same configuration, and explanation would be redundant, only the configuration of process unit 4Y, which corresponds to yellow (Y), will be described here.

[0028] The process unit 4Y includes a photosensitive member 40Y, a charging device 42Y, a laser unit 53Y, a developing device 43Y, a primary transfer roller 475Y, and a cleaning device 44Y.

[0029] The photoreceptor 40Y is a drum-shaped member that serves as an image carrier and rotates in direction A, which is counterclockwise as shown in FIG. 3. A photosensitive layer is formed on the photoreceptor 40Y, serving as the surface to be scanned by the scanning light emitted by the laser unit 53Y. The charging device 42Y charges the photoreceptor 40Y. The laser unit 53Y forms a latent image on the photoreceptor 40Y by scanning with the scanning light. The developing device 43Y develops the latent image on the photoreceptor 40Y formed by the laser unit 53Y with yellow (Y) toner to form a toner image. The primary transfer roller 475Y transfers the toner image formed on the photoreceptor 40Y to the transfer belt 47 around which it is wound. The cleaning device 44Y removes excess toner remaining on the photoreceptor 40Y after the toner image has been transferred to the transfer belt 47.

[0030] By using these process units 4Y, 4M, 4C, and 4K, a toner image, which is a mixed color image, is formed on the transfer belt 47 by mixing the basic colors.

[0031] The transfer unit 5 includes a transfer belt 47, a drive roller 471 driven by a drive source to rotate in direction B in FIG. 3, a driven roller 472 that rotates in direction B in the same manner as the drive roller 471, and a secondary transfer roller 473.

[0032] Transfer belt 47 is made of low-stretch polyimide resin with dispersed carbon powder to adjust electrical resistance. Transfer belt 47 is wound around drive roller 471, driven roller 472, secondary transfer roller 473, and primary transfer rollers 475Y, 475M, 475C, and 475K.

[0033] The secondary transfer roller 473 is a roller that contacts the transfer belt 47 together with an opposing roller at the secondary transfer position N to form a nip portion. At the secondary transfer position N, the secondary transfer roller 473 sandwiches the transfer belt 47 together with the paper P between it and the opposing roller, and applies a secondary transfer bias to transfer the toner image on the surface of the transfer belt 47 to the paper P. The secondary transfer bias applies a charge of the opposite polarity to the electrostatic charge on the surface of the transfer belt 47. The paper P onto which the toner image has been transferred at the secondary transfer position N is transported to the fixing unit 6.

[0034] The measurement sensor 45 is an in-line chromaticity measuring device that combines multiple monochrome line sensors, each equipped with a bandpass filter corresponding to the three target colors of R (red), G (green), and B (blue) in the front stage so that it is sensitive to each of these three target colors. The measurement sensor 45 has measurement channels with three spectral characteristics corresponding to the three colors of R (red), G (green), and B (blue). The number of measurement channels that the measurement sensor 45 has is referred to as the number of measurement channels. The measurement sensor 45 is installed downstream of the fixing position N2 in the transport direction of the paper P, and measures the reflection characteristics of all or part of the image (color image) formed on the paper P.

[0035] The measurement sensor 45 may be a so-called color scanner, provided that it has a measurement channel with at least one spectral characteristic, i.e., a measurement channel sensitive to one or more primary colors, or it may be a monochrome line sensor with a single spectral characteristic.

[0036] When the paper P passes through the fixing nip N2 formed between the heating roller 61 and the fixing roller 62, the fixing unit 6 fixes the toner image carried on the paper P by the action of heat and pressure, forming a good color image on the paper P. The paper P with the fixed image that has passed through the fixing unit 6 is discharged from the paper discharge unit 7 to the outside of the image forming mechanism 4. Note that the paper discharge unit 7 may be provided with a switching claw and a duplex unit, and the paper P may be fed into the duplex unit according to the state of the switching claw to prepare for double-sided image formation.

[0037] Fig. 4 is a diagram showing an example of the functional configuration of image forming apparatus 100 according to an embodiment of the present invention. As shown in Fig. 4, image forming apparatus 100 has image processing unit 30 and image forming unit 50. These units are implemented by a program installed in image forming apparatus 100 and loaded into memory 102, which is executed by CPU 101. However, image processing unit 30 and image forming unit 50 may be implemented using hardware (CPU) different from that of image forming apparatus 100. For example, image processing unit 30 may be implemented by a terminal separate from image forming apparatus 100, or may be implemented by user terminal 200 or server 201, as long as it is capable of communicating with the hardware that implements image forming unit 50.

[0038] The image processing unit 30 performs image processing to convert the manuscript data Q received from the user terminal 200 or the server 201 via the communication network 500 into a format printable by the image forming mechanism 4. The manuscript data Q is expressed in a data format including bitmap data with RGB or CMYK color specifications, text data, or graphic drawing instructions. The image processing unit 30 also converts the image-processed manuscript data Q into a pixel array consisting of the basic colors cyan (C), magenta (M), yellow (Y), and black (K) of the image forming mechanism 4, for example, bitmap data in which the color information for each pixel is arranged in a grid, or image data in an equivalent compressed format. In this embodiment, the manuscript data Q includes multiple pages (multiple images printed in sequence), and the print job including the manuscript data Q includes an instruction to print a single copy (one copy) of the manuscript data Q. A single copy refers to printing one copy of the same page at a time.

[0039] 4, the image processing unit 30 includes a first conversion unit 310, a second conversion unit 311, a tone correction unit 312, and an image storage unit 302.

[0040] The first conversion unit 310 converts each of the multiple pages included in the document data Q into image data docLab in the device-independent Lab format.

[0041] The second conversion unit 311 converts the Lab format image data docLab into CMYK format image data prnCMYK, in which pixel values ​​are sets of 8-bit integer gradation values ​​for each of the basic colors of the image forming mechanism 4: cyan C, magenta M, yellow Y, and black K.

[0042] The gradation correction unit 312 corrects the gradation of the CMYK format image data prnCMYK based on the selected color profile. The CMYK format image data with corrected gradation is called "image data R." The image data R is bitmap data for the four basic colors C, M, Y, and K, which are obtained by quantizing the color information of the original data Q. The image data R is generated for each of the multiple pages included in the original data Q.

[0043] The image storage unit 302 temporarily stores various data including the image data R or continuously stores the data while the image is being formed. The image storage unit 302 can be realized using, for example, the auxiliary storage device 103.

[0044] The image forming unit 50 includes a gradation conversion unit 51, an image formation control unit 52, a master image generation unit 53, a scanned image generation unit 54, a colorimetric area extraction unit 55, a color difference calculation unit 56, a color difference classification unit 57, an output control unit 58, and a color difference information storage unit 59. The color difference information storage unit 59 can be realized using, for example, the auxiliary storage device 103.

[0045] The gradation conversion unit 51 converts the color values ​​(gradation values) of each pixel of the image data R stored in the image memory unit 302, which are expressed in, for example, 8 bits for each basic color, using area gradation or error diffusion so that the color values ​​match the number of gradations that can be expressed by the image forming mechanism 4.

[0046] The image formation control unit 52 controls the image formation mechanism 4 to print on paper P the image data in which the number of gradations of the image data R has been converted by the gradation conversion unit 51. Specifically, the image formation control unit 52 controls the image formation mechanism 4 based on the image data to form a toner image, and causes the transfer unit 5 to transfer the formed toner image onto paper P.

[0047] For each image data R, the master image generator 53 generates an image (hereinafter referred to as a "master image") having theoretical color information in RGB format that will be obtained when the image data R is printed. Here, the theoretical color information refers to the color information that is expected (or predicted) to be obtained when the image forming apparatus 100 prints the image data R under predetermined machine conditions. The master image can be generated, for example, using an LUT conversion table that contains correspondence information between the CMYK values ​​of the original print and the RGB values ​​of the print result, taking into account the scanning characteristics of the measurement sensor 45. If the print result is ideal for the user when a dedicated chart (color chart) is printed using the image forming apparatus 100 under predetermined machine conditions, the LUT conversion table can be generated by acquiring the correspondence between the characteristics (CMYK values) of the image data R at that time and the characteristics (RGB values) of the image read by the measurement sensor 45 from the print result. However, because this correspondence varies depending on the type of printing paper (background color), LUT tables are created for each paper type. The master image generation unit 53 generates a master image by converting the CMYK values ​​of each pixel of the image data R into RGB pixel values ​​(hereinafter referred to as "masterCol") using an LUT conversion table corresponding to each type of paper. Therefore, a master image is generated for each type of paper. However, the master image generation unit 53 may generate only a master image corresponding to the type of paper P being used in the current print job.

[0048] The scanned image generation unit 54 detects (reads) an image inline from the paper P printed out by the image forming mechanism 4 using the scanner 27. Specifically, the scanned image generation unit 54 generates an image printed on the paper P (hereinafter referred to as a "scanned image") by controlling the measurement sensor 45 included in the scanner 27. The measurement sensor 45 irradiates light onto the image formed on the paper P by the image forming mechanism 4 and receives the reflected light, thereby measuring the reflectance of the image in a two-dimensional plane and detecting the measured value (hereinafter referred to as "mesCol") as a pixel value of the scanned image. Detecting an image means measuring the colors (RGB values) that make up the image (hereinafter referred to as "colorimetry"). In other words, the mesCol of each pixel of the scanned image is an RGB value.

[0049] The colorimetry area extraction unit 55 extracts one or more colorimetry areas from an area such as a photograph or drawing in each image data R. A colorimetry area is a partial area that is the target of calculation of the color difference between the master image and the scanned image.

[0050] FIG. 5 is a diagram illustrating the extraction of colorimetric regions. In FIG. 5, image data R of a certain page shows regions 1 to 13, each of which is a collection of pixels of the same color system. Each black rectangle in each of these regions represents a colorimetric region. Hereinafter, each colorimetric region of a certain page p will be referred to as colorimetric region (p)(xi, yi) (i = 1, . . . , N). Here, N is the total number of colorimetric regions in page p (all colorimetric regions included in regions 1 to 13 in the example of FIG. 5), and (xi, yi) represent the x- and y-coordinates of the center of the ith colorimetric region among the N colorimetric regions. Each colorimetric region is approximately several square millimeters, and a region of a predetermined size within a region with minimal color gradation change is extracted as the colorimetric region. Note that regions 1 to 13 are illustrated for convenience in order to distinguish regions with minimal color gradation change (regions belonging to the same color system).

[0051] The size of one colorimetric area may be a predetermined pixel area, such as a 5 mm square, or 41 x 41 pixels at 400 dpi. However, if the area suitable for colorimetric measurement is smaller than the predetermined pixel area, the colorimetric area extraction unit 55 may select a smaller pixel area for one colorimetric area. For example, if the colorimetric area extraction unit 55 determines that the area suitable for colorimetric measurement is smaller than the 5 mm square, it may extract a single colorimetric area with a size of, for example, 21 x 21 pixels. This allows for the acquisition of an appropriate color variation amount that is less affected by color changes due to differences in color gradation in the image.

[0052] In Figure 5, the paper feed direction in which the paper P on which the image data R is printed is transported in the image forming apparatus 100, that is, the sub-scanning direction, is represented by coordinate y, and the direction perpendicular to the sub-scanning direction (main scanning direction) is represented by coordinate x.

[0053] For example, the colorimetry region extraction unit 55 analyzes the gradation change of the image data R and extracts a partial region with little gradation change (a region of the same color system with little change in shading (less than a threshold)) as one colorimetry region. The reason for treating a region with little change in shading as one colorimetry region is to treat regions with as similar colors as possible as one colorimetry region. In this embodiment, a color system refers to a color system (classification) classified based on a color wheel, such as a light-density range, a dark-density range, or an intermediate range of blues, reds, greens, or grays (such as color systems A to H in Figure P). How the color wheel is divided (i.e., how many color systems to include) may be set in advance.

[0054] The colorimetry region extraction unit 55 extracts, for each page p of the document data Q, N colorimetry regions (p)(xi, yi) (i=1, . . . , N) from the image data R corresponding to p.

[0055] The color difference calculation unit 56 calculates color difference information (color difference) in the color measurement area between the master image corresponding to each page of the entire print job (one copy) and the scanned image. The master image used for color difference calculation is the master image corresponding to the paper P used in the print job, among the master images for each paper type.

[0056] More specifically, the color difference calculation unit 56 converts the RGB values ​​of masterCol for each pixel of the master image and mesCol for each pixel of the scanned image into Lab (CIELab) format, which is suitable for calculating color differences. Hereinafter, the value of masterCol converted to Lab format will be referred to as "masterLab," and the value of mesCol converted to Lab format will be referred to as "mesLab." For each colorimetric region (p)(xi,yi), the color difference calculation unit 56 calculates the average value of masterLab included in the colorimetric region (p)(xi,yi) in the master image, masterLab(p)(xi,yi), and the average value of mesLab included in the colorimetric region in the scanned image, mesLab(p)(xi,yi), and calculates the color difference ΔLab(p)(xi,yi) between the master image and the scanned image in the colorimetric region (p)(xi,yi) based on the following equation (1):

[0057]

number

[0058] Therefore, ΔLab(p)(xi,yi) is obtained for each colorimetric region (p)(xi,yi).

[0059] The color difference classifier 57 calculates a value by subtracting the overall average value of a set of color differences for colorimetry areas (p)(xi,yi) classified into the same color system in the master image from the average value of the subset for each page (each master image). Specifically, the color difference classifier 57 classifies the color differences ΔLab(p)(xi,yi) calculated for each colorimetry area (p)(xi,yi) by the color system n to which the colorimetry area (p)(xi,yi) related to the color difference belongs, and calculates the average color difference difLab[n][p] for each color system n for each page p and the average color difference Ref_difLab[n] for each color system n across all pages. The color system to which a certain colorimetry area (p)(xi,yi) belongs is the color system to which the color (masterLab(p)(xi,yi)) of the colorimetry area (p)(xi,yi) belongs in the master image. Both difLab[n][p] and Ref_difLab[n] are calculated by weighting each color difference by the number of colorimetric regions (samples) corresponding to that color difference. For example, Ref_difLab[n] is calculated based on the following formula (2):

[0060]

number

[0061] Here, sample[n][p] is the number of colorimetric regions of color system n on page p.

[0062] The color difference classification unit 57 calculates the difference (absolute value) between Ref_difLab[n] and difLab[n][p] of the page p for each page p and each color system n. This difference is expressed as ΔdifLab[n][p]. A page and color system with a relatively large ΔdifLab[n][p] has a large color variation.

[0063] The color difference classification unit 57 saves the calculated ΔdifLab[n][p] and color difference information including information related to the print job in the color difference information storage unit 59. Therefore, the color difference information is stored in the color difference information storage unit 59 for each print job.

[0064] The output control unit 58 controls the output of a report based on the color difference information stored in the color difference information storage unit 59 in response to a predetermined operation by the user of the image forming apparatus 100. The report is displayed on, for example, an operation panel of the image forming apparatus 100.

[0065] Note that an example is shown in which the format handled by the color difference calculation unit 56 (i.e., the color difference format) is Lab (CIELab) format, and the image processing unit 30 converts the original data Q, which is color data in CMYK format, into Lab format, but the format handled by the color difference calculation unit 56 is not limited to Lab format, and any color expression format can be used as long as it can clearly indicate the amount of color change.

[0066] Furthermore, the first conversion unit 310, the second conversion unit 311, and the color difference calculation unit 56 require basic data called a color profile for their respective color space conversions. Of these color profiles, the color profile required for converting the document colors to Lab values ​​is one that is attached to the document data Q or that is prepared in advance. Because the color reproduction characteristics of the color profile required for the second conversion unit 311 are affected by the type of paper P, it is desirable to select and set an appropriate color profile that matches the type of paper P from multiple color profiles stored in advance in the server 201. Furthermore, the color profile required for the color difference calculation unit 56 is set in advance in the color difference calculation unit 56.

[0067] The image processing unit 30 may change the color profile depending on the type of paper P in accordance with a user's selection, or may change the color profile in accordance with a selection of paper P that matches the input document data Q. The image processing unit 30 may use, for example, an ICC profile defined by the ICC (International Color Consortium) as such a color profile.

[0068] The following describes the processing procedure executed by the image forming apparatus 100. Fig. 6 is a flowchart for explaining an example of the processing procedure executed by the image forming apparatus 100. In Fig. 6, the processing starts when the image forming apparatus 100 receives a print job with a single copy setting, the image processing unit 30 generates image data R for each page of the document data Q of the print job, and the image data is stored in the image storage unit 302.

[0069] Steps S101 to S105 are loop processes for each page that are executed in parallel with the printing of each page. Image data R corresponding to the page to be processed (hereinafter referred to as "target page p") will be referred to as "image data R(p)".

[0070] In step S101, the colorimetric region extraction unit 55 extracts N colorimetric regions (p)(xi, yi) from the image data R(p). Note that the value of N may differ for each page.

[0071] Next, the master image generating unit 53 generates a master image for each paper type based on the image data R(p) (S102). However, the master image generating unit 53 may generate only a master image corresponding to the type of paper P used in the current print job.

[0072] Next, the scanned image generating unit 54 generates a scanned image of the target page p in association with printing of the target page p, which is performed based on processing of the image data R(p) by the gradation conversion unit 51 and the image formation control unit 52 (S103).

[0073] Next, for each colorimetric area (p)(xi, yi) of the target page p, the color difference calculation unit 56 converts the RGB value masterCol of each pixel of the master image corresponding to the type of paper P used in the current print job into the Lab value masterLab, and converts the RGB value mesCol of each pixel of the scanned image into the Lab value mesLab (S104).

[0074] Next, for each colorimetric region (p)(xi,yi), the color difference calculation unit 56 calculates the average value masterLab(p)(xi,yi) of masterLab included in that colorimetric region (p)(xi,yi) and the average value mesLab(p)(xi,yi) of mesLab included in that colorimetric region, and calculates the color difference ΔLab(p)(xi,yi) between the master image and the scanned image in that colorimetric region (p)(xi,yi) based on the above formula (1) (S105). Therefore, N ΔLab(p)(xi,yi) are calculated.

[0075] The color difference calculation unit 56 may calculate the color difference ΔE value from the color difference ΔLab(p)(xi, yi) based on a formula defined by the International Commission on Illumination (CIE). In this case, ΔLab(p)(xi, yi) in the following description may be replaced with ΔE.

[0076] When steps S101 to S105 are executed for all pages and the print job is completed (Yes in S106), the color difference classification unit 57 classifies each colorimetric area (p)(xi, yi) of each page p into a predetermined number of color systems n based on the color (masterLab(p)(xi, yi)) of the master image corresponding to the colorimetric area (p)(xi, yi) (S107).

[0077] Next, the color difference classifying unit 57 calculates the weighted average value Ref_difLab[n] of the color differences for each color system n across all pages based on the above formula (2) (S108).

[0078] Next, the color difference classifying unit 57 calculates the weighted average value difLab[n][p] of the color differences for each color system n for each page p (S109).

[0079] Next, the color difference classification unit 57 calculates, for each page p and each color system n, the difference (absolute value) ΔdifLab[n][p] between difLab[n][p] of the page p and Ref_difLab[n] (S110).

[0080] Next, the color difference classification unit 57 stores color difference information including the calculation result ΔdifLab[n][p] and information about the print job (hereinafter referred to as "job information") in the color difference information storage unit 59 (S111). The job information includes, for example, identification information of the print job (hereinafter referred to as "job number"), the execution date and time of the print job (hereinafter referred to as "print date and time"), the pages constituting the job, and the total number of pages. The pages constituting the job are the number of pages constituting the print job. The total number of pages is the total number of printed pages, and is calculated by multiplying the pages constituting the job by the number of copies. In this embodiment, since it is assumed that one copy will be printed, the pages constituting the job and the total number of pages are the same value.

[0081] Thereafter, when the user inputs an instruction to output a report via the operation panel of the image forming device 100 or the like at any timing asynchronous to the print job (Yes in S112), the output control unit 58 outputs a report based on the color difference information stored in the color difference information storage unit 59 (S113).

[0082] FIG. 7 is a diagram showing an example of a report output. FIG. 7 shows an example of a screen 910 displayed on the operation panel. The screen 910 includes, for each print job, job information, color difference average, maximum color difference, maximum color difference page number, data protection button 911, delete button 912, and data check button 913. The color difference average of a certain print job is the average value of ΔdifLab[n][p] for that print job. The maximum color difference of a certain print job is the maximum value of ΔdifLab[n][p] for that print job. The maximum color difference page number of a certain print job is the page number of the maximum value ΔdifLab[n][p] for that print job (i.e., the value of p).

[0083] The data protection button 911 is a button for receiving an instruction to protect color difference information. When the data protection button 911 is set to ON (protection enabled), the color difference information of the print job is protected and cannot be deleted.

[0084] The delete button 912 is a button for accepting an instruction to delete the color difference information. The output control unit 58 deletes the color difference information of the print job for which the delete button 912 is pressed from the color difference information storage unit 59.

[0085] The data check button 913 is a button for receiving an instruction to display detailed information about color difference information. The output control unit 58 displays detailed information about color difference information about the print job for which the data check button 913 was pressed (hereinafter referred to as the "target job").

[0086] Fig. 8 is a diagram showing an example of how detailed information is displayed. Fig. 8 shows an example in which ΔdifLab[n][p] is displayed for each color system and for each page regarding color difference information for the target job. Fig. 8 shows an example in which the information is displayed for each color system, but it is also possible to display the results for all color systems together.

[0087] This allows the user to check color difference information for each color system for each page of a single copy print job at a glance, thereby improving the accuracy of inspection of color variations in print jobs.

[0088] Furthermore, by taking appropriate measures based on these results and smoothing out color variations within the same color family, it is possible to reduce bias errors in variations due to, for example, uneven density within a page that occurs during the image formation process, thereby enabling more accurate confirmation of color differences.

[0089] 7 and 8 may be output by printing, which allows the color difference fluctuation information of a single copy print job to be retained and managed.

[0090] As described above, according to this embodiment, for each image in a print job (multiple images printed in sequence), a master image is generated that contains theoretical color information for that image when it is printed. For each of the multiple images printed in sequence, the color difference between one or more partial regions in the master image corresponding to that image and a scanned image read from the paper on which that image is printed is calculated. For a set of color differences for the partial regions classified into the same color family, the difference between the average value for each master image and the overall average value for the set is calculated. The difference thus obtained makes it possible to grasp color variations for each page when printing a single copy.

[0091] Furthermore, even if the image configuration of each page of a print job differs, by classifying the color difference by color system, it is possible to determine the color difference of the entire page and also the color difference of each page. Therefore, even if the image configuration of each page of a print job differs, color variations within the job can be detected with high accuracy.

[0092] The colorimetry area extraction unit 55 may also extract an area of ​​the image to be printed that has little change in gradation as the colorimetry area, thereby obtaining an appropriate amount of color variation that is less affected by color changes due to differences in color gradation on the image.

[0093] Each function of the above-described embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to execute each function by software, such as a processor implemented by an electronic circuit, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and conventional circuit modules designed to execute each of the above-described functions.

[0094] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims.

[0095] For example, aspects of the present invention are as follows. <1>

[0096] a master image generating unit that generates a master image having theoretical color information when each of a plurality of images to be printed in order is printed;

[0097] a color difference calculation unit that calculates, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed;

[0098] a color difference classification unit that calculates a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions that are classified into the same color system; An image forming apparatus comprising: <2>

[0099] each of the images being an image of a respective page of a print job including multiple pages; Characterized by <1> The image forming apparatus described above. <3>

[0100] the content of each of the plurality of images is different; Characterized by <1> or <2> The image forming apparatus described above. <4>

[0101] the master image generating unit generates the master image from an image based on information indicating a correspondence relationship between color information of the image and color information when the image is printed. Characterized by <1> ~ <3> The image forming apparatus according to any one of the preceding claims. <5>

[0102] an output control unit that controls output of information based on the difference; characterized in that it has <1> ~ <4> The image forming apparatus according to any one of the preceding claims. <6>

[0103] the output control unit controls output of the difference for each image. Characterized by <5> The image forming apparatus described above. <7>

[0104] a master image generation step for generating a master image having theoretical color information when each of the plurality of images to be printed in order is printed;

[0105] a color difference calculation step of calculating, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed;

[0106] a color difference classification step of calculating a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions classified into the same color system; An information processing method characterized by being executed by a computer. <8>

[0107] a master image generation step for generating a master image having theoretical color information when each of the plurality of images to be printed in order is printed;

[0108] a color difference calculation step of calculating, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed;

[0109] a color difference classification step of calculating a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions classified into the same color system; A program characterized by causing a computer to execute the above. [Explanation of symbols]

[0110] 1. Image forming system 4. Image formation mechanism 27 Scanner 45 Measurement Sensor 30 Image processing section 50 Image forming unit 51 Gradation conversion section 52 Image formation control unit 53 Master image generation unit 54 Scan image generation unit 55 Colorimetric area extraction section 56 Color difference calculation section 57 Color difference classification section 58 Output control section 59 Color difference information storage unit 100 Image forming device 101 CPU 102 memory 103 Auxiliary storage device 104 Network I / F 106 Printer engine I / F 200 user terminals 201 Server 302 Image storage unit 310 First Conversion Unit 311 Second Conversion Unit 312 Gradation Correction Section [Prior art documents] [Patent documents]

[0111] [Patent Document 1] Japanese Patent Publication No. 2023-067715

Claims

1. a master image generating unit that generates a master image having theoretical color information when each of a plurality of images to be printed in order is printed; a color difference calculation unit that calculates, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed; a color difference classification unit that calculates a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions that are classified into the same color system; An image forming apparatus comprising:

2. each of the images being an image of a respective page of a print job including multiple pages; 2. The image forming apparatus according to claim 1, wherein:

3. the content of each of the plurality of images is different; 2. The image forming apparatus according to claim 1, wherein:

4. the master image generating unit generates the master image from an image based on information indicating a correspondence relationship between color information of the image and color information when the image is printed.

2. The image forming apparatus according to claim 1, wherein:

5. an output control unit that controls output of information based on the difference; 2. The image forming apparatus according to claim 1, further comprising:

6. the output control unit controls output of the difference for each image.

6. The image forming apparatus according to claim 5.

7. a master image generation step for generating a master image having theoretical color information when each of a plurality of images to be printed in order is printed; a color difference calculation step of calculating, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed; a color difference classification step of calculating a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions classified into the same color system; An information processing method characterized by being executed by a computer.

8. a master image generation step for generating a master image having theoretical color information when each of the plurality of images to be printed in order is printed; a color difference calculation step of calculating, for each of the images, a color difference between one or more partial regions in the master image corresponding to the image and a scanned image read from paper on which the image is printed; a color difference classification step of calculating a difference between an average value for each of the master images and an overall average value for the color difference sets related to the partial regions classified into the same color system; A program characterized by causing a computer to execute the above.

Images