JP2020055141A - Image processing device and program - Google Patents

Abstract

To provide an image processing device and program which can perform the proper density correction even when a lamination order of color materials at the time of performing the image formation is different from an estimated lamination order of color materials at the time of creating a color profile.SOLUTION: An image processing device includes: a color conversion unit which performs the color conversion of the first image data that has been input into the second image data by using a color profile set in accordance with the lamination order of color materials; and a density correction unit which generates the third image data by correcting the density of the density target being the value of the target of the density of the image formed on a recording medium based on the second image data in accordance with the difference between the first information indicating the lamination order of the color materials at the time of the image formation and the second information indicating the lamination order of the color materials at the time of the creation of the profile set in the color profile.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image processing device and a program.

  Conventionally, the stacking order of the coloring materials in the image forming is controlled according to the stacking order of the coloring materials set in advance for each output device that outputs image data to the image forming apparatus, or A technique for correcting image data (Patent Document 1) is disclosed.

  There is also known an image forming apparatus in which a user can change the stacking order of CMYK process colors and special color materials. According to such an image forming apparatus, for example, by changing the stacking order so that a clear color material, which is a special color material, is stacked on the uppermost layer, a three-dimensional appearance or glossiness is obtained, or a white color material is obtained. By changing the stacking order so as to be stacked on the lowermost layer, it is possible to cope with various uses such that the formed image is hardly affected by the recording medium.

  It is known that a color conversion table (color profile) is used in an image processing apparatus in order to maintain the accuracy of color reproduction of an image formed on a recording medium by an image forming apparatus.

  However, the color profile is not generated on the assumption that the stacking order of the color materials is changed. Therefore, when the stacking order of the color materials in the image forming apparatus is different from the stacking order of the color materials assumed when the color profile is generated, the density correction is performed using the density correction target associated with the color profile. If so, there is a problem that the accuracy of color reproduction cannot be maintained.

  Further, in the related art, there is a problem that when the user changes the stacking order of the coloring materials of the image forming apparatus, it is not possible to perform appropriate density correction in the stacking order of the coloring materials intended by the user. Further, in the related art, there is a problem that a decrease in color reproduction accuracy caused by a difference between the stacking order of the color materials of the image forming apparatus and the stacking order of the color materials assumed when creating the color profile cannot be prevented. .

  Furthermore, it is very troublesome for the user to create a color profile every time the stacking order of the color materials is changed. Further, a user who does not have a tool for creating a color profile cannot cope with the above problem.

  The present invention has been made in view of the above, and is a case where the lamination order of the color materials when performing image formation and the lamination order of the color materials assumed when the color profile is created are different. It is another object of the present invention to provide an image processing apparatus and a program capable of performing appropriate density correction.

  In order to solve the above-described problem and achieve the object, the present invention provides a method of converting input first image data into second image data using a color profile set in accordance with the color material stacking order. A color conversion unit for performing conversion, first information indicating a stacking order of color materials at the time of image formation, and second information indicating a stacking order of color materials at the time of creating a profile set in the color profile. A density correction unit that corrects a density target that is a target value of the density of an image formed on a recording medium based on the second image data based on the difference to generate third image data; It is characterized by having.

  According to the present invention, even when the stacking order of the color materials when forming an image and the stacking order of the color materials assumed when the color profile is created are different, the user can create a new color profile. There is an effect that an appropriate density correction can be performed without creating.

FIG. 1 is a diagram illustrating an example of the image processing system according to the first embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of the DFE. FIG. 3 is a block diagram showing functions of the CPU of the DFE. FIG. 4 is a diagram illustrating an example of a table for managing a color profile. FIG. 5A is a diagram for explaining the relationship between the toner stacking order at the time of creating a profile and the order of stacking on a recording medium. FIG. FIG. FIG. 6 is a diagram illustrating an example of the calibration sheet. FIG. 7 is a diagram illustrating an example of the UI screen when the calibration is performed. FIG. 8 is a diagram for explaining a density target. FIG. 9 is a diagram illustrating an example of a functional block of the density target correction unit. FIG. 10 is a diagram illustrating an example of information on a difference in the stacking order of the color materials calculated by the color material stacking order comparison unit. FIG. 11 is a diagram illustrating an example of a table in which the difference in the toner stacking order of the color materials and the correction coefficient for correcting the density target are associated with each other. FIG. 12 is a flowchart illustrating a flow of a process performed by the density target correction unit. FIG. 13 is a diagram illustrating an example of a density correction table generated by the density correction table generation unit. FIG. 14 is a flowchart showing the flow of the density correction table generation processing. FIG. 15 is a diagram illustrating an example of the calibration sheet according to the second embodiment. FIG. 16 is a diagram for explaining a brightness target. FIG. 17 is a diagram illustrating an example of information on a lightness colorimetric value calculated by the correction coefficient calculating unit. FIG. 18 is a diagram illustrating an example of a table of density targets corrected using the information on the lightness colorimetric values. FIG. 19 is a diagram illustrating an example of the UI screen when the calibration is performed. FIG. 20 is a flowchart showing the flow of the density correction table generation processing.

  Hereinafter, an image processing apparatus and a program will be described in detail with reference to the accompanying drawings. Hereinafter, an electrophotographic image forming apparatus will be described as an example of an image forming apparatus, but the present invention is not limited to this, and an inkjet image forming apparatus may be used.

(First Embodiment)
[Description of Configuration of Image Processing System]
FIG. 1 is a diagram illustrating an example of the image processing system 100 according to the first embodiment. As shown in FIG. 1, the image processing system 100 includes a computer 200, a DFE (Digital Front End) 300, an image forming apparatus 400, and a spectrophotometer 500.

  The computer 200 is a device that creates a print job including image data to be executed by the user on the image forming apparatus 400, and transmits the created print job to the DFE 300.

  The DFE 300 is an example of an image processing apparatus according to the present invention. Based on a print job received from the computer 200, the DFE 300 generates drawing data (raster data) used when the image forming apparatus 400 forms an image. Image Processer) engine. DFE 300 transmits the generated drawing data to image forming apparatus 400.

  The image forming apparatus 400 forms an image on a recording medium based on the drawing data received from the DFE 300. In addition, the image forming apparatus 400 includes a fluorescent material such as C (cyan) color, M (magenta) color, Y (yellow) color, and K (black) color corresponding to the process colors of CMYK, A special color material such as clear or metallic is mounted, and an image is formed on a recording medium. In addition, the image forming apparatus 400 can change the stacking order of CMYK process colors and special color materials.

  The spectral colorimeter 500 reads an image formed on a recording medium by the image forming apparatus 400, acquires spectral reflectance information indicating a spectral reflectance, and transmits the spectral reflectance information to the DFE 300. In the present embodiment, the spectrocolorimeter 500 is connected to the DFE 300, but is not limited to this, and may be connected to the computer 200 or the image forming apparatus 400.

  Schematically, the image forming apparatus 400 prints the calibration sheet 600 (see FIG. 6), and the DFE 300 measures the printed calibration sheet 600 (see FIG. 6). Received from colorimeter 500.

  Although the DFE 300 and the image forming apparatus 400 are shown as different apparatuses in the present embodiment, the present invention is not limited to this, and the image forming apparatus 400 may have the function of the DFE 300, or the computer 200 It may have a function. For example, when the computer 200 has the function of the DFE 300, a configuration corresponding to the function of the DFE 300 can be interpreted as an image processing apparatus. Further, the functions of the DFE 300 may be shared between the computer 200 and the image forming apparatus 400.

  Next, the hardware configuration of the DFE 300 will be described.

  FIG. 2 is a diagram illustrating an example of a hardware configuration of the DFE 300. As shown in FIG. 2, the DFE 300 includes a CPU (Central Processing Unit) 301 serving as a control main body. The DFE 300 is a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, an engine interface 304, a panel interface 305, a panel device 306, a host interface 307, a HDD (Hard Disk Drive) or an SSD (Solid State Drive). A storage unit 308 is provided, and each unit is connected to the CPU 301 via the bus 309.

  The CPU 301 implements control of the image forming apparatus 400 and image processing by using the RAM 303 as a work area and executing programs stored in the ROM 302 and the storage unit 308.

  The engine interface 304 connects the CPU 301 and the storage unit 308 to the image forming apparatus 400 so as to be able to communicate.

  The panel interface 305 connects a panel device 306, which is an example of an operation unit included in the DFE 300, to be communicable with the CPU 301 and the storage unit 308.

  The host interface 307 communicably connects the computer 200 with the CPU 301, the storage unit 308, and the like.

  The storage unit 308 stores information such as a print job and a color profile sent from the computer 200. Further, a program executed by the CPU 301 may be stored.

[Explanation of DFE functional configuration]
Next, a function realized by the CPU 301 of the DFE 300 executing a program stored in the ROM 302 or the storage unit 308 will be described.

  FIG. 3 is a block diagram illustrating functions of the CPU 301 of the DFE 300. The DFE 300 has functions of a color conversion unit 401, a total amount control unit 402, a density correction unit 403, and a halftone processing unit 404.

  The color conversion unit 401 performs a predetermined color conversion process on the RGB values (or CMYK values or L * a * b * values) of the input image data (first image data), and outputs a new CMYK value. Image data (second image data) is generated. The color conversion unit 401 transmits the second image data after the color conversion processing to the total amount control unit 402. Note that the color conversion unit 401 may transmit the second image data to the density correction unit 403 without passing through the total amount control unit 402. In that case, the total amount of toner may be regulated by a color profile.

  Next, a color profile used for a color conversion process performed by the color conversion unit 401 will be described with reference to FIG.

  FIG. 4 is a diagram illustrating an example of a table T1 for managing a color profile. The table T1 is stored in the storage unit 308 in advance, and stores the file name, display name, and toner stacking order of a color profile for converting device-independent data such as RGB into device-dependent data such as CMYK. , Profile ID.

  The file name indicates the name of a color profile file.

  The display name is an item displayed on the display of the panel device 306 or the computer 200.

  The toner stacking order at the time of profile creation is the toner stacking order used at the time of color profile creation. Here, FIG. 5A is a diagram for explaining the relationship between the toner stacking order at the time of profile creation and the toner stacking order on the recording medium. FIG. 5B is a diagram showing the toner stacking order when the profile is created and the toner stacking order on the recording medium. As shown in FIG. 5A, the toner stacking order “1” at the time of profile creation is closest to the recording medium side, and the toner stacking order “2”, “3”, “4” at the time of profile creation is recorded in this order. Move away from media. When the user creates a color profile, the user sets the toner stacking order when creating the profile.

  The profile ID is index data assigned to the color profile, and is numbered sequentially from the built-in one. When the user additionally reads a color profile, a number is sequentially assigned.

  The total amount regulating unit 402 has a function of suppressing the total amount of toner stacked on the recording medium to be equal to or less than an upper limit value so that a fixing failure does not occur during execution of an image forming process. The total amount regulating unit 402 generates second image data in which the total amount of toner is regulated, from the second image data received from the color conversion unit 401. The total amount regulating unit 402 transmits the second image data after the regulation of the total amount of toner to the density correcting unit 403.

  The density correction unit 403 performs gradation correction (calibration) of the image on the second image data according to the state of the image forming apparatus 400, and generates third image data after the calibration. The density correction unit 403 has functions of a density target determination unit 601, a density target correction unit 602, a density correction table generation unit 603, and a colorimetric value acquisition unit 604. Each function of the density correction unit 403 will be described later.

  The density correction unit 403 prints, using the image forming apparatus 400, a calibration sheet 600 (see FIG. 6) in which a plurality of preset C, M, Y, and K single color patches are arranged. The spectral reflectance information, which is the result measured at 500, is acquired. The density correction unit 403 generates information for performing calibration based on the spectral reflectance information acquired as described above, and uses the information generated when performing calibration.

  The calibration sheet 600 will be described with reference to FIG.

  FIG. 6 is a diagram illustrating an example of the calibration sheet 600. FIG. 6A shows a calibration sheet 600a in which a plurality of patches of each of CMYK are arranged, and FIG. 6B shows a calibration sheet in which a plurality of patches of each of CMYK with a special color material as a base are arranged. 6 shows an application sheet 600b. FIG. 6C shows an example of a table T2 in which the patch numbers assigned to the respective patches are associated with the tone values.

  The user prints the calibration sheet 600a shown in FIG. 6A or the calibration sheet 600b shown in FIG. 6B to generate information to be used when performing the calibration, and performs spectrometry. The calibration sheet 600a or 600b is measured by the color meter 500.

  The density correction unit 403 executes calibration, which will be described later, using spectral reflectance information that is a measurement result of the calibration sheet 600 measured by the user.

  Here, FIG. 7 is a diagram illustrating an example of the UI screen UI1 when the calibration is performed. In the present embodiment, when the user desires to execute the calibration, the density correction unit 403 displays the UI screen UI1 on the panel device 306 of the DFE 300 or the display of the computer 200. The user makes various settings from the UI screen UI1, and presses a calibration execution button B1. Accordingly, the density correction unit 403 executes a calibration process described later.

  Hereinafter, for the sake of explanation, on the UI screen UI1, the user selects “plain paper” for the density target, “OFF” for the first white printing, “plain paper F005” for the paper selection, and “Plain_F” for the color profile selection. It is assumed that

  Next, details of each function of the density target determination unit 601, the density target correction unit 602, the density correction table generation unit 603, and the colorimetric value acquisition unit 604 included in the density correction unit 403 will be described.

  The density target determination unit 601 reads from the storage unit 308 a density target table T3 (see FIG. 8) that is a characteristic of a target density for each gradation value. Here, FIG. 8 is a diagram for explaining the density target. FIG. 8A shows an example of a table T3 of density targets for each storage medium. As shown in FIG. 8A, each storage medium (plain paper, gloss paper, matte paper, etc.) is represented by a set of a tone value and a density target value for each of CMYK. Note that storage media (plain paper, gloss paper, mat paper, etc.) are indexed by a calibration ID described later. FIG. 8B is a graph showing the relationship between the area ratio, which is the toner loading amount per unit area, and the density target value for the K (black) color of the density target table T3 in FIG. 8A. is there.

  The density target determination unit 601 determines a density target based on the density target table T3 (FIG. 8A).

  FIG. 8C shows an example of a table T4 indicating information associated with the density target. Information associated with the density target shown in FIG. 8C is displayed on the UI screen UI1. In the example illustrated in FIG. 8C, the density target name selected by the user, whether the white toner stacking order is “1” (white first printing), and the calibration ID are associated with the density target. When the white first printing is “0”, the white stacking order is not “1”, and when the white first printing is “1”, the white stacking order is “1”. The calibration ID is index data sequentially assigned to each density target, and is data for linking a density correction table T6 (see FIG. 13) described later with the density target. When a new density target is created, a calibration ID is sequentially assigned.

  For example, when the user selects the density target name “plain paper” on the UI screen UI1, the density target determination unit 601 reads the density target corresponding to the calibration ID “1” from the storage unit 308 (FIG. 8A). Is read. Then, the density target determination unit 601 transmits the read density target and the calibration ID to the density target correction unit 602.

  The density target correction unit 602 includes a calibration ID and a density target received from the density target determination unit 601, a toner stacking order during image formation that is the toner stacking order when the image forming apparatus 400 performs image formation, and profile creation. A density correction table is generated by correcting the density target based on the toner stacking order at the time.

  FIG. 9 is a diagram illustrating an example of a functional block of the density target correction unit 602.

  The density correction determination unit 901 is an example of a determination unit, acquires a calibration ID from the density target determination unit 601, and determines whether the density target selected by the user as a correction target is a density target capable of performing density correction. Determine whether or not. If there is a density target that is intentionally adjusted for using a specific paper and profile in a specific toner stacking order, unintended correction may occur if correction is performed in consideration of the toner stacking order. Could be done. Therefore, such a calibration ID of the density target is stored in the storage unit 308 in advance, and the density correction determination unit 901 compares the calibration ID of the density target to be corrected by comparing the calibration ID with the calibration ID of the density target to be corrected. To determine if it is possible. The density correction determination unit 901 transmits the determination result to the color material stacking order acquisition unit 902.

  The color material stacking order obtaining unit 902 is an example of an obtaining unit, and when the determination result received from the density correction determining unit 901 indicates that density correction is possible, information on the toner stacking order at the time of image formation from the image forming apparatus 400 is obtained. (First information) is obtained. The color material stacking order obtaining unit 902 obtains the profile ID of the color profile set by the user, and obtains the toner stacking order information (second information) at the time of creating the profile corresponding to the profile ID. The color material stacking order acquisition unit 902 transmits the acquired toner stacking order information at the time of image formation and the toner stacking order information at the time of profile creation to the color material stacking order comparison unit 903. Each time the toner stacking order at the time of image formation in image formation by the image forming apparatus 400 is changed, the storage unit 308 stores the toner stacking order information at the time of image formation, and the color material stacking order acquisition unit 902 reads from the storage unit 308 The toner stack information at the time of image formation may be read.

  The color material stacking order comparison unit 903 is an example of a comparison unit, and information on the color material stacking order received from the color material stacking order acquisition unit 902 (toner stacking order when creating a profile and toner stacking order when forming an image). Are compared to determine whether the stacking order matches. In this embodiment, the color material stacking order comparison unit 903 subtracts the toner stacking order at the time of image formation from the toner stacking order at the time of profile creation, and when the difference becomes 0 for each color, the stacking order matches. Judge that

  FIG. 10 is a diagram illustrating an example of information on the difference in the stacking order of the color materials calculated by the color material stacking order comparison unit 903. As shown in FIG. 10, △ Oc, △ Om, △ Oy, and △ Ok indicate differences in the CMYK toner stacking order (the toner stacking order when creating a profile and the toner stacking order when forming an image). The color material stacking order comparison unit 903 transmits the calculated difference in the toner stacking order of each color to the correction coefficient calculation unit 904.

  The correction coefficient calculation unit 904 is an example of a calculation unit, and corresponds to a difference in the toner stacking order (the toner stacking order when creating a profile and the toner stacking order when forming an image) of each color calculated by the color material stacking order comparison unit 903. The table T5 (see FIG. 11) of the attached correction coefficient is read from the storage unit 308. The correction coefficient calculation unit 904 acquires a correction coefficient from the read correction coefficient table T5 and transmits the correction coefficient to the target correction unit 905.

  FIG. 11 is a diagram illustrating an example of a table T5 in which the difference in the toner stacking order of the color materials and the correction coefficient for correcting the density target are associated. The correction coefficients a, b, c, and d shown in FIG. 11 are values that function to lower the density when the difference in the toner stacking order is negative, and when the difference in the toner stacking order is positive, It is a value that works to increase the density. The correction coefficient is 1 for a color having a difference of zero because no correction is required. The correction coefficient calculation unit 904 is not limited to the correction coefficient, and may calculate the correction amount corresponding to the difference in the toner stacking order and the gradation value for each color, or the difference in the toner stacking order and the gradation value for each color. May be read from the storage unit 308 to determine the correction amount.

  The target correction unit 905 corrects each value of the density target based on the correction coefficient received from the correction coefficient calculation unit 904 and the density target.

  Next, a flow of processing executed by the density target correction unit 602 will be described with reference to FIG.

  FIG. 12 is a flowchart illustrating a flow of a process performed by the density target correction unit 602. As shown in FIG. 12, in S1201, the density correction determination unit 901 determines whether or not the density target is a density target for performing density correction. If the calibration ID of the density target to be corrected is a calibration ID that does not perform correction (Yes in S1201), the density correction determination unit 901 proceeds to S1206. On the other hand, when the calibration ID of the density target to be corrected is the calibration ID for performing the correction (No in S1201), the density correction determination unit 901 proceeds to S1202.

  In step S1202, the color material stacking order obtaining unit 902 obtains image stacking order information from the image forming apparatus 400, and obtains toner stacking order information at the time of profile creation from the profile ID. The color material stacking order acquisition unit 902 transmits the acquired information of the toner stacking order at the time of creating the profile to the color material stacking order comparison unit 903.

  In step S <b> 1203, the color material stacking order comparison unit 903 compares the toner stacking order when creating the profile acquired by the color material stacking order acquisition unit 902 in step S <b> 1202 with the toner stacking order when forming an image. If the stacking order is the same (Yes in S1203), the color material stacking order comparison unit 903 proceeds to S1206. On the other hand, the coloring material stacking order comparison unit 903 proceeds to S1204 when the stacking order does not match (No in S1203).

  In step S1204, the correction coefficient calculation unit 904 calculates a correction coefficient corresponding to the difference in the stacking order of each color.

  In step S1205, the target correction unit 905 corrects the density target by multiplying each value of the density target by the correction coefficient calculated in step S1204 by the correction coefficient calculation unit 904.

  In step S1206, the target correction unit 905 stores the density target corrected in step S1205 in the storage unit 308, and ends the process.

  Next, the colorimetric value acquisition unit 604 will be described.

  The colorimetric value acquisition unit 604 acquires spectral reflectance information, which is a measurement result of the calibration sheet 600, from the spectral colorimeter 500. The colorimetric value acquisition unit 604 transmits the acquired spectral reflectance information to the density correction table generation unit 603.

  Next, the density correction table generation unit 603 will be described.

  The density correction table generation unit 603 is an example of a table generation unit, and the spectral reflection which is a measurement result of the calibration sheet acquired from the spectral colorimeter 500 by the colorimetric value acquisition unit 604 and transmitted to the density correction table generation unit 603. A density correction table T6 (see FIG. 13) is generated based on the rate information and the density target corrected by the density target correction unit 602. The density correction table generation unit 603 causes the storage unit 308 to store the generated density correction table T6 in association with the calibration ID corresponding to the density target information.

  FIG. 13 is a diagram illustrating an example of the density correction table T6 generated by the density correction table generation unit 603. FIG. 13A illustrates a current density value (colorimetric value) obtained from spectral reflectance information for an input tone value (input tone value) and a density target corrected by the density target correction unit 602. Is shown. The density correction table T6 shown in FIG. 13B realizes a density target based on the current density value (colorimetric value) obtained from the spectral reflectance information for the input tone value (input tone value). 4 is a look-up table for converting an input grayscale value into a grayscale value as shown in FIG.

  Specifically, the density correction table generation unit 603 outputs the density target “0.076” at the tone value “10”, and based on the density value calculated from the current spectral reflectance information, sets the input tone value. The gradation value to be converted is calculated by linear interpolation. Since the density target “0.076” in the colorimetric value corresponds to a value between the tone values “10” and “15”, a tone value “14” is obtained by calculation by linear interpolation. In other words, in the current state of the image forming apparatus 400, when the gradation value “10” is input, if the gradation value is converted to the gradation value “14”, the target density value can be realized. The density correction table generation unit 603 calculates output tone values for realizing each density target value, and creates a density correction table T6 for converting a tone as shown in FIG.

  Next, the halftone processing unit 404 will be described.

  The halftone processing unit 404 performs screen processing on the third image data generated by the density correction unit 403 to generate drawing data. The halftone processing unit 404 transmits the generated drawing data to the image forming apparatus 400.

  Next, a flow of a characteristic process among the processes performed by the DFE 300 which is the image processing apparatus according to the present embodiment will be described.

  FIG. 14 is a flowchart showing the flow of the density correction table generation processing. In the density correction table generation processing shown in FIG. 14, the user selects a density target, determines whether or not white printing has been performed, and records on the UI screen UI1 (see FIG. 7) displayed on the display of the panel device 306 or the computer 200. This is executed by selecting a paper type and a color profile, respectively, and pressing a calibration execution button B1.

  As shown in FIG. 14, in step S1401, the density target determination unit 601 acquires special color preprint information indicating whether white preprint, which is a special color set by the user, is present. In the present embodiment, as shown in the example of the UI screen of FIG. 7, the special color first printing information is “OFF”.

  In step S1402, the density target determination unit 601 acquires recording medium information indicating the type of paper set by the user. In the present embodiment, the recording medium information is “plain paper F005” as shown on the UI screen UI1 in FIG.

  In step S1403, the density target determination unit 601 acquires density target information indicating a density target set by the user. In the present embodiment, the density target information is “plain paper” as shown on the UI screen UI1 in FIG. The density target determination unit 601 acquires a density target from the calibration ID corresponding to the density target information.

  In step S1404, the density target determination unit 601 acquires color profile information indicating a color profile set by the user. In the present embodiment, the color profile information is “Plain_F” as shown on the UI screen UI1 in FIG. The density target determination unit 601 acquires the toner stacking order information at the time of profile creation from the profile ID corresponding to the density target information, and transmits the information to the density target correction unit 602.

  In step S1405, the density correction unit 403 reads the image data of the calibration sheet 600 from the storage unit 308, causes the halftone processing unit 404 to execute halftone processing, and causes the image forming apparatus 400 to transmit the image data after the halftone processing. . Then, the image forming apparatus 400 prints the calibration sheet 600. In the case of the present embodiment, since the spot color preprint information is “OFF”, the spot color is not printed on the base of each CMYK patch, and the calibration sheet 600a on which the CMYK patch is formed on the recording medium is printed. .

  In step S <b> 1406, the colorimetric value acquisition unit 604 acquires spectral reflectance information, which is a result of measuring the printed calibration sheet 600 a with the spectral colorimeter 500, and transmits the information to the density correction table generation unit 603.

  In step S <b> 1407, the density target correction unit 602 acquires the toner stacking order information during image formation from the image forming apparatus 400. The density target is corrected based on the density target acquired by the density target determination unit 601 in step S1403, the toner stacking order information when forming an image, and the toner stacking order information when creating a profile.

  In S1408, the density correction table generation unit 603 generates a density correction table T6 (see FIG. 13) based on the spectral reflectance information acquired in S1406 and the density target corrected in S1407. The density correction table generation unit 603 stores the generated density correction table T6 in the storage unit 308 in association with the calibration ID acquired in S1403, and ends the process.

  As described above, according to the present embodiment, the order of stacking the toner of the color material when forming the image by the image forming apparatus 400 is different from the order of stacking the toner of the color material assumed when creating the color profile. In this case, it is possible to generate information for executing the calibration in consideration of the difference in the stacking order, so that appropriate density correction can be performed without creating a new color profile.

(Second embodiment)
Next, a second embodiment will be described.

  The DFE 300 according to the second embodiment acquires information on brightness using a mixed-color calibration sheet in which colors used for image formation are added to each patch of CMYK, and information used when performing density calibration. Is different from the first embodiment. Hereinafter, in the description of the second embodiment, the description of the same parts as those of the first embodiment will be omitted, and the points different from the first embodiment will be described.

  FIG. 15 is a diagram illustrating an example of the calibration sheet 600 according to the second embodiment. FIG. 15A shows a mixed color calibration sheet 600c in which a plurality of patches in which colors used for image formation are added to a plurality of patches of CMYK are arranged, and FIG. 15B shows a special color material. This shows a mixed-color calibration sheet 600d in which a plurality of patches in which colors used for image formation are added to a plurality of patches of CMYK as bases are added. FIG. 15C shows an example of a table T7 in which the patch numbers assigned to the respective patches are associated with the CMYK gradation values excluding the added colors.

  The user prints the calibration sheet 600c shown in FIG. 15A or the calibration sheet 600d shown in FIG. 15B to generate information used when executing the calibration, and performs spectrometry. The calibration sheet 600c or 600d is measured by the color meter 500.

  In the example of the mixed-color calibration sheet 600c illustrated in FIG. 15A, a K having a tone value of 40 is added to each of the C, M, and Y patches, and a Y having a tone value of “40” is added to each of the K patches. ing. The brightness target value is stored in the storage unit 308 in association with the calibration ID of the density target.

  In the storage unit 308 of the DFE 300, a table T8 (see FIG. 16) indicating a target lightness (lightness target) when the image forming apparatus 400 in which the toner stacking order has not been changed prints the mixed color calibration sheet on plain paper. Is stored.

  The density target determining unit 601 reads out from the storage unit 308 a table T8 (see FIG. 16) of a target brightness target for each gradation value. Here, FIG. 16 is a diagram for explaining a brightness target. FIG. 16A shows an example of a brightness target table T8 of each patch obtained by adding Y to K for each storage medium. As shown in FIG. 16A, each storage medium (plain paper, gloss paper, matte paper, etc.) is represented by a set of a tone value of each KY and a lightness target value. Note that storage media (plain paper, gloss paper, mat paper, etc.) are indexed by the calibration ID. FIG. 16B is a graph showing the relationship between the area ratio, which is the toner loading amount per unit area, and the brightness target value for the KY color mixture in the brightness target table T8 in FIG. 16A.

  Next, a method of calculating a correction coefficient used when the density target correction unit 602 corrects a density target will be described. Hereinafter, for the sake of explanation, on the UI screen UI2 (see FIG. 19), the density target is “plain paper”, white printing is “OFF”, the paper is “plain paper F005”, and the color profile is “ It is assumed that “Plain_F” has been selected.

  It is assumed that the difference between the toner stacking order at the time of image formation and the toner stacking order at the time of profile creation is the value shown in FIG. 10 by the color material stacking order comparison unit 903.

  The correction coefficient calculation unit 904 calculates the lightness targets Lc, Lm, Ly, and Lk of the CMYK colors and the lightness (lightness colorimetric value) Lc ′ of each color of CMYK calculated from the spectral reflectance information acquired from the colorimetric value acquisition unit 604. Using Lm ', Ly', and Lk ', Xc, Xm, Xy, and Xk, which are correction coefficients for correcting the respective density targets of CMYK, are calculated. Hereinafter, only the case where the correction coefficient Xk for correcting the density target of K color will be described, but the correction coefficient is similarly calculated for other colors.

  Xk is calculated by the following equation (3) using the lightness target value Lk and the lightness colorimetric value Lk ′ in each patch of the K color shown in FIG.

  FIG. 17 is a diagram illustrating an example of information on the lightness colorimetric values calculated by the correction coefficient calculating unit 904. FIG. 17 shows the brightness target Lk corresponding to each patch number, the brightness colorimetric value Lk ′ of the brightness target corresponding to each patch number, and the ratio of the brightness target Lk to the brightness colorimetric value Lk ′ for the K color patch. An example of the calculated information is shown.

  As described above, in the present embodiment, the correction coefficient used for the density calibration is calculated by using the mixed color calibration sheet. In the case of the present embodiment, Xk is 0.78.

  The target correction unit 905 corrects the density target by multiplying each value of the density target of the corresponding color by the correction coefficients Xc, Xm, Xy, and Xk calculated by the correction coefficient calculation unit 904.

  FIG. 18 is a diagram illustrating an example of a density target table T9 corrected using the information on the lightness colorimetric values. FIG. 18A shows a table T9 in which the density target value is corrected for the K color using the calculated Xk.

  A table T9 in FIG. 18A is a table in which K color tone values, target density values, and corrected density values are associated with each other in a mixed-color patch in which the color used for image formation is added to the K color. It is. FIG. 18B is a graph in which the horizontal axis plots the area ratio indicating the amount of toner loaded per unit area corresponding to the gradation value, and the vertical axis plots the density target and the corrected density target.

  Next, details of the processing performed by the density target correction unit 602 in the present embodiment will be described.

  Here, FIG. 19 is a diagram illustrating an example of the UI screen UI2 when the calibration is performed. In the present embodiment, when the user desires to execute the calibration, the density correction unit 403 displays the UI screen UI2 displayed on the panel device 306 of the DFE 300 or the display of the computer 200. The user performs various settings from the UI screen UI2 and presses a calibration execution button B2, so that the density correction unit 403 executes a calibration process described later.

  Hereinafter, for the sake of explanation, on the UI screen UI2, the density target is “plain paper”, the white printing is “OFF”, the paper is selected as “plain paper F005”, the color profile is “Plain_F”, and the calibration sheet is selected. It is assumed that “mixed color calibration sheet” is selected.

  FIG. 20 is a flowchart showing the flow of the density correction table generation processing. In the density correction table generation processing shown in FIG. 20, the user selects a density target, determines whether or not white preprinting has been performed, and records on the UI screen UI2 (see FIG. 19) displayed on the display of the panel device 306 or the computer 200. This is executed by selecting the type of paper, the color profile, and the type of calibration sheet, and pressing the calibration execution button B2. The description of the processing common to the first embodiment will be omitted.

  As illustrated in FIG. 20, in S2004, the density target correction unit 602 acquires the calibration ID of the density target “plain paper” set by the user, and acquires the density target corresponding to the calibration ID acquired from the storage unit 308. Read the brightness target.

  In step S2005, the density correction unit 403 reads the image data of the mixed-color calibration sheet 600 from the storage unit 308, causes the halftone processing unit 404 to execute halftone processing, and transmits the image data after the halftone processing to the image forming apparatus 400. Let it. Then, the image forming apparatus 400 prints the calibration sheet 600. In the case of the present embodiment, since the spot color preprint information is “OFF”, the spot color is not printed on the base of each patch, and the mixed color calibration sheet 600c in which each patch is formed on the recording medium is printed.

  In step S2006, the colorimetric value acquisition unit 604 acquires spectral reflectance information as a result of measuring the printed mixed color calibration sheet 600c with the spectral colorimeter 500, and transmits the information to the correction coefficient calculation unit 904.

  In step S2007, the correction coefficient calculation unit 904 corrects the density target based on the brightness target, the spectral reflectance information, the toner stacking order information when forming an image, and the toner stacking order information when creating a profile. Calculate the coefficient.

  In S2008, the target correction unit 905 multiplies the density target values by the correction coefficients Xc, Xm, Xy, and Xk of each color calculated by the correction coefficient calculation unit 904 in S2007, and corrects the brightness target value.

  In step S2009, the target correction unit 905 stores the density target corrected in step S2008 in the storage unit 308 in association with the calibration ID, and ends the process.

  As described above, according to the present embodiment, a calibration sheet composed of mixed color patches obtained by adding a certain color to each of the CMYK patches is used instead of a calibration sheet composed of CMYK single color patches. Calibration can also be performed using information regarding brightness, and the user can perform more effective calibration.

  In the description of each embodiment, the spectral reflectance information is acquired using the calibration sheet and the mixed-color calibration sheet. However, the present invention is not limited to this. The data may be input from the panel device 306 of the DFE 200 or 200.

  The functions of each embodiment of the present invention can be realized by a computer-executable program described in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark), or an object-oriented programming language. A program for executing the function of each embodiment can be distributed through a telecommunication line.

  Further, programs for executing the functions of the embodiments of the present invention include ROM, EEPROM (Electrically Erasable Programmable Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), flash memory, flexible disk, CD ( Compact Disc)-stored on a device-readable recording medium such as ROM, CD-RW (Re-Writable), DVD-ROM, DVD-RAM, DVD-RW, Blu-ray Disc, SD card, MO (Magneto-Optical disc), etc. Can also be distributed.

  Furthermore, some or all of the functions of each embodiment of the present invention can be implemented on a programmable device (PD) such as an FPGA (Field Programmable Gate Array), or can be implemented as an ASIC. Circuit configuration data (bit stream data) to be downloaded to the PD in order to realize the functions of the embodiments on the PD, HDL (Hardware Description Language) for generating the circuit configuration data, and VHDL (Very High Speed Integrated Circuits) Hardware description language), Verilog-HDL, and the like can be distributed on a recording medium as data.

  The embodiment according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment as it is. it can. Various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described embodiments. For example, some components may be deleted from all the components described in the embodiments.

300 Image processing device 401 Color conversion unit 403 Density correction unit 903 Comparison unit 904 Calculation unit 905 Target correction unit

JP-A-02-164565

Claims (7)

A color conversion unit that performs color conversion of the input first image data into second image data using a color profile set in accordance with the color material stacking order;
The second information based on a difference between first information indicating a color material stacking order at the time of image formation and second information indicating a color material stacking order at the time of profile creation set in the color profile. A density correction unit that corrects a density target, which is a target value of the density of an image formed on a recording medium, based on the image data, and generates third image data;
An image processing apparatus comprising: The density correction unit,
A comparing unit configured to compare, based on the first information and the second information, a stacking order of the coloring materials at the time of forming an image and a stacking order of the coloring materials at the time of creating a profile;
A calculation unit that calculates a correction coefficient for correcting the density target based on a comparison result of the comparison unit,
A target correction unit that corrects the density target based on the correction coefficient calculated by the calculation unit,
The image processing apparatus according to claim 1, further comprising: The comparing unit calculates a difference between a stacking order of the coloring materials specified from the first information and a stacking order of the coloring materials specified from the second information,
The calculation unit calculates the correction coefficient based on the difference,
The image processing apparatus according to claim 2, wherein: The comparison unit is configured to determine, for each type of color material used for image formation, a difference between a stacking order of the color material specified from the first information and a stacking order of the color material specified from the second information. Is calculated,
The calculation unit calculates the correction coefficient for each type of color material based on the difference,
The image processing apparatus according to claim 2, wherein: The calculation unit calculates the correction coefficient based on spectral reflectance information indicating a spectral reflectance for each color material used for image formation, a comparison result of the comparison unit, and a brightness target.
The image processing apparatus according to claim 2, wherein: The spectral reflectance information is information on spectral reflectance obtained by measuring a sheet in which a plurality of mixed-color patches in which one patch is formed using a plurality of color materials are arranged.
The image processing apparatus according to claim 5, wherein: The computer that controls the image processing device
A color conversion function of performing color conversion of the input first image data into second image data using a color profile set in accordance with the color material stacking order;
The second information based on a difference between first information indicating a color material stacking order at the time of image formation and second information indicating a color material stacking order at the time of profile creation set in the color profile. A density correction function of correcting a density target which is a target value of the density of an image formed on a recording medium based on the image data of (a) and generating third image data;
The program that realizes.

Images