JP2008301351A - Method of correcting spot color - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce troubles of a user by performing job output and correction simultaneously without performing spot color correction as a preprocess of the job output in an image outputting device, such as a printer, and by applying the result for output. <P>SOLUTION: After a print instruction, a job is held and a spot color correction table is created. The hold of the job is canceled before the spot color correction table is applied for output. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a calibration or printer profile adjustment technique performed to obtain a stable output for a specific color when outputting to a color printer.

  As a technique for faithfully reproducing a target color using a color printer, there is a spot color matching technique. This technique is based on the premise that the printer profile is properly adjusted in the initial state. If the printer state is affected by environmental fluctuations, stable output may not be obtained. A possible solution is to recreate the printer profile. This is a profile that generates an optimized profile for the entire color reproduction space of the printer. Become.

Therefore, the part that affects the conversion of the target color in the correspondence relationship from the device-independent color space to the printer color reproduction space in the initial profile is changed, and the estimated printer color corresponds to the target color. A method of making adjustments was proposed. Japanese Patent Laid-Open No. 2006-157294 has proposed a method in which a spot color correction table is created separately without rewriting the printer profile itself, and correction is performed by applying the table.
JP 2006-157294 A JP 2001-324846 A

  However, the above proposal has a problem in that it takes time and effort for the user because correction processing must be performed before image output.

In order to achieve such an object, the present invention provides:
In a system that outputs a color image to a printer by color matching using a printer profile,
Means for providing job color data with spot color correction setting information;
Means for temporarily holding the job and analyzing the spot color correction setting information in the job ticket data;
Means for performing a spot color correction process to realize the target value described in the spot color setting information;
Means for creating a spot color correction table from the result of the spot color correction process;
And means for canceling the held job and applying and outputting the spot color correction table to the job.

  According to the present invention, there is no work to perform correction processing before job output, and spot color correction processing, job application processing, and output work can be performed simultaneously according to the job.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a network system according to an embodiment of the present invention.

  As shown in FIG. 1, the network system according to the present embodiment includes a front-end server 1 serving as a printer controller, a printer engine 2 (connected to the network by the front-end server), a client A (PC and monitor) at a site A such as a LAN. Are connected and configured. The client A is connected to a UI for displaying information and accepting data input to the user, and has a CPU / VRAM and the like necessary for image processing and a communication function necessary for communication on the network.

  FIG. 2 is a diagram showing the configuration of the front end server 1 and the printer engine 2 described above.

  As shown in FIG. 2, the front-end server 1 analyzes a network I / F (interface) unit 10 for connecting to a network, a job control unit 11 for controlling job data, and a PDL (page description language) to obtain intermediate data. A PDL interpreter unit 12 to be generated, an intermediate data storage unit 13 that stores intermediate data generated by the PDL interpreter unit, a rendering unit 14 that converts the intermediate data stored in the intermediate data storage unit into bitmap image data, and a printer engine A communication interface unit 15 for exchanging data with 2, a target color storage unit 16 that stores a target color that is a color value of a device-independent color space set by the user, and a plurality of generated for the target color A color patch generator 17 for generating a color patch chart composed of colors; A color patch data storage unit 17A for storing patches, a color management processing unit 18 for performing color matching and calibration processing specified for a job, a profile storage unit 18A for storing profiles used for color matching, and calibration Among the data, a calibration one-dimensional LUT (Look Up Table) storage unit 18B for storing a one-dimensional LUT, a device color patch which is a storage location of device color patch data obtained by converting device-independent color patch data into a printer color A data storage unit 19, a device color estimation unit 20 for estimating the color that the printer outputs in the current state based on the color measurement result of the color sensor, and a device color storage unit 20A for storing the device color , Make the initial printer profile current A spot correction table adjustment unit 21 for generating / updating a spot correction value table for adjustment, a spot correction table storage unit 21A for storing the spot correction table, and a colorimetric value for storing data obtained by reading a target color by a color sensor The storage unit 22 is configured.

  The job control unit 11 includes a job management unit 11A that performs management such as holding a job, and a job analysis unit 11B that analyzes a job ticket in the job.

  The printer engine 2 is read by the communication I / F unit 23 that exchanges data with the front-end server 1, the output unit 24, the color sensor control unit 25 that controls the color sensor, the color sensor 26 that reads the patch output, and the color sensor. The colorimetric value storage unit 27 stores data.

  FIG. 3 is a diagram showing a flow of processing of image data. When RGB data or CMYK data is input in a normal color management process, color matching is performed through a source profile and a printer profile, and then passed through a calibration one-dimensional LUT to be output as corrected CMYK data. When applying the result of spot color correction, the image data is output with reference to both the target color correction data and the printer profile in the spot color correction table.

  FIG. 4 is an example of a spot color correction table used in the present invention. A table is divided for each color chart, and each table holds a color number, a corresponding chromaticity, and a difference value (device color correction value) from the initial printer profile when the color chart color is output.

  FIG. 5 is a schematic diagram of a Lab color space for explaining an embodiment of the present invention. An eight-point grid surrounding the target color of the printer profile lookup table (Lab → CMYK) is shown for the target color (L1, a1, b1). Before the change, the target color (L1, a1, b1) could be reproduced with the matching result (C1, M1, Y1, K1) based on the initial profile. In order to reproduce the target color (L1, a1, b1) due to printer fluctuations, the spot color correction table is adjusted so that the matching result is (C2, M2, Y2, K2).

  FIG. 6 is an example of a color sensor used in the present proposal. You may use the color sensor as shown in FIG. 8 of Unexamined-Japanese-Patent No. 2001-324846. The color sensor 28 is built in a light emitting element 28A such as an LED and a light receiving element 28B such as a photodiode or CdS in a holder 28C. The color sensor 28 measures the chromaticity of the patch T by irradiating the patch T on the transfer belt 29 with light from the light emitting element 28A and receiving the reflected light from the patch T with the light receiving element 28B.

  FIG. 7 shows that job data is composed of job ticket data in which contents for instructing processing to a job are described, and job data files that are actual data such as PDF, PS, TIFF, JPEG, and the like. Is shown.

  FIG. 8 shows an example of job ticket data. Here, the layout information includes paper size setting information, paper type information, page orientation information, and the like. The color management information includes RGB and CMYK source profiles, printer profiles, calibration settings, and the like.

  FIG. 9 shows an example of the calibration setting display in the job ticket data. This includes a spot color correction flag for selecting whether or not to perform spot color correction, a color number or chromaticity to be corrected, and the like.

  FIG. 10 is a flowchart for explaining the spot color correction table generation process of the present invention using the configuration of FIG.

  In step 100, a print command is issued from the UI of client A to the front-end server 1, job data is transmitted through the network, and the process proceeds to step 101.

  In step 101, the job control unit 11 controls, the job data is temporarily held in the job management unit 11A, the job file data processing is set in a standby state, and the process proceeds to step 102.

  In step 102, only the job ticket data in the job data is extracted and analyzed by the job analysis unit 11B. Here, the color number of the target color is extracted, and the process proceeds to step 103.

  In step 103, the color patch generation unit 17 generates device-independent color color patch data using the target color and the initial printer profile stored in the profile storage unit 18A. The color patch data is stored in the color patch data storage unit 17A.

  In step 104, the color management processing unit 18 converts the device-independent color patch data stored in the color patch storage unit 17A into device color patch data using the initial printer profile. For example, for the target color (L1, a1, b1), the result (C1, M1, K1, Y1) is obtained. This is stored in the device color patch data storage unit 19.

  In step 105, the previous device color patch data is transferred to the printer engine 2, and the output unit 24 outputs a color chart output using the device color patch data.

  In step 106, the color sensor control unit 25 performs color measurement of the color chart output using the color sensor 26, obtains a color chart color measurement value, and stores it in the color measurement value storage unit 27.

  In step 107, the color chart colorimetric values stored in the colorimetric value storage unit 27 are transferred to the front-end server 1, and the device color estimation unit 20 reproduces the target color from the device color patch data and the color chart colorimetric values. Estimate the device color. For example, interpolation calculation may be performed in a device-independent color space. The calculation example here will be described in detail after the description of FIG. The estimated device color value obtained here is (C2, M2, K2, Y2), and is stored in the device color storage unit 20A.

  In step 108, the spot correction table adjustment unit 21 sets the initial printer in the spot correction table so that the matching result for the target color (L1, a1, b1) is the device color (C2, M2, K2, Y2). Write the difference value (C2-C1, M2-M1, Y2-Y1, K2-K1) from the profile. The updated table is stored in the spot correction table storage unit 21A, and the process proceeds to step 109.

  In step 109, the held job is canceled, the updated spot color correction table and the initial printer profile are applied to the job, printing is performed, and the process is terminated.

  FIG. 11 is a flowchart for explaining the job ticket analysis process in step 102 in detail.

  In step 110, only the job ticket data in the job data is extracted, and the process proceeds to step 111.

  In step 111, the job ticket data is analyzed by the job analysis unit 11B, and the value of the spot color correction flag in the calibration setting is confirmed. If the flag is ON, the correction color number is extracted, the spot color source profile in the profile storage unit 18A is referred to obtain the corresponding device-independent color value, and the process proceeds to step 112.

  In step 112, the device-independent color value corresponding to the color number to be corrected is held in the target color storage unit 16, and the process is terminated.

  FIG. 12 is a flowchart for explaining in detail the color patch data creation processing in step 103.

In step 120, the target color stored in the target color storage unit 16 is set to (L1, a1, b1), and is extracted. However,
0≤L1≤100, -128≤a1≤128, -128≤b1≤128
And Then, it progresses to step 121.

  In step 121, a value obtained by subtracting 1 from the number of grids in the profile lookup table is n. For example, if the number of grids is 33, n = 32.

i = L1 / 100 * n
j = (a1 + 128) / 256 * n
k = (b1 + 128) / 256 * n
(Rounded down)
The index i, j, k of the Lab color space grid is obtained by the above formula. 0 ≦ i, j, k ≦ n
In step 122, from the BToA1Tag 3D lookup table of the initial printer profile
(i, j, k) (i, j, k + 1) (i, j + 1, k) (i, j + 1, k + 1)
(i + 1, j, k) (i + 1, j, k + 1) (i + 1, j + 1, k) (i + 1, j + 1, k + 1)
The data of the 8-point grid indicated by the above index is color patch data, and is sequentially set as P11, P12, P13, P14, P15, P16, P17, and P18. This ends the process.

Here, an example of device color estimation processing in step 107 will be described in detail.
The device color patch data of the eight color patches P11 to P18 are (C11, M11, Y11, K11) to (C18, M18, Y18, K18), respectively, and the color chart colorimetric values are (L11, a11, b11), respectively. ) To (L18, a18, b18). P21 to P27 are intermediate data for obtaining the device color estimated value P2.

(Calculate P21 from P11, P12)
L21 = (L12-L11) * (b1-b11) / (b12-b11) + L11
a21 = (a12-a11) * (b1-b11) / (b12-b11) + a11
C21 = (C12-C11) * (b1-b11) / (b12-b11) + C11
M21 = (M12-M11) * (b1-b11) / (b12-b11) + M11
Y21 = (Y12-Y11) * (b1-b11) / (b12-b11) + Y11
K21 = (K12-K11) * (b1-b11) / (b12-b11) + K11
(Calculate P22 from P13, P14)
L22 = (L14-L13) * (b1-b13) / (b14-b13) + L13
a22 = (a14-a13) * (b1-b13) / (b14-b13) + a13
C22 = (C14-C13) * (b1-b13) / (b14-b13) + C13
M22 = (M14-M13) * (b1-b13) / (b14-b13) + M13
Y22 = (Y14-Y13) * (b1-b13) / (b14-b13) + Y13
K22 = (K14-K13) * (b1-b13) / (b14-b13) + K13
(Calculate P23 from P21, P22)
L23 = (L22-L21) * (a1-a21) / (a22-a21) + L21
C23 = (C22-C21) * (a1-a21) / (a22-a21) + C21
M23 = (M22-M21) * (a1-a21) / (a22-a21) + M21
Y23 = (Y22-Y21) * (a1-a21) / (a22-a21) + Y21
K23 = (K22-K21) * (a1-a21) / (a22-a21) + K21
(Calculate P24 from P15, P16)
L24 = (L16-L15) * (b1-b15) / (b16-b15) + L15
a24 = (a16-a15) * (b1-b15) / (b16-b15) + a15
C24 = (C16-C15) * (b1-b15) / (b16-b15) + C15
M24 = (M16-M15) * (b1-b15) / (b16-b15) + M15
Y24 = (Y16-Y15) * (b1-b15) / (b16-b15) + Y15
K24 = (K16-K15) * (b1-b15) / (b16-b15) + K15
(Calculate P25 from P17, P18)
L25 = (L18-L17) * (b1-b17) / (b18-b17) + L17
a25 = (a18-a17) * (b1-b17) / (b18-b17) + a17
C25 = (C18-C17) * (b1-b17) / (b18-b17) + C17
M25 = (M18-M17) * (b1-b17) / (b18-b17) + M17
Y25 = (Y18-Y17) * (b1-b17) / (b18-b17) + Y17
K25 = (K18-K17) * (b1-b17) / (b18-b17) + K17
(Calculate P26 from P24, P25)
L26 = (L25-L24) * (a1-a24) / (a25-a24) + L24
C26 = (C25-C24) * (a1-a24) / (a25-a24) + C24
M26 = (M25-M24) * (a1-a24) / (a25-a24) + M24
Y26 = (Y25-Y24) * (a1-a24) / (a25-a24) + Y24
K26 = (K25-K24) * (a1-a24) / (a25-a24) + K24
(Calculate P27 from P23, P26)
C27 = (C26-C23) * (L1-L23) / (L26-L23) + C23
M27 = (M26-M23) * (L1-L23) / (L26-L23) + M23
Y27 = (Y26-Y23) * (L1-L23) / (L26-L23) + Y23
K27 = (K26-K23) * (L1-L23) / (L26-L23) + K23
(C27, M27, Y27, K27) is the estimated device color (C2, M2, Y2, K2).

  FIG. 13 is a flowchart for explaining the details of the job print restart process in step 109.

  In step 130, the processing of the job file held in the job management unit 11A is resumed.

  In step 131, the PDL interpreter unit 12 analyzes the job file data to generate intermediate data, and the process proceeds to step 132.

  In step 132, the intermediate data generated in step 131 is stored in the intermediate data storage unit 13, and the process proceeds to step 133.

  In step 133, the color management processing unit 18 uses the spot color correction table for the intermediate data stored in the intermediate data storage unit 13 to perform color matching and calibration processing on the input data. Apply and go to step 134.

  In step 134, the intermediate data in step 133 is developed into bitmap image data by the rendering unit 14, and the process proceeds to step 135.

  In step 135, the developed bitmap image data is transferred to the printer engine 2, and the process proceeds to step 136.

  In step 136, a paper is selected based on the Info_media information, and the process proceeds to step 137.

  In step 137, printing is performed on the selected paper, and the process ends.

  FIG. 14 is a flowchart showing details of the correction processing using the spot color correction table in step 133.

  In step 140, the color number of the target color is retrieved from the target storage unit 16.

  In step 141, the target color (L1, a1, b1) corresponding to the input color number is obtained from the spot color source profile, and the process proceeds to step 142.

  In step 142, a device-dependent device color corresponding to the target color (L1, a1, b1) is obtained from the initial printer profile in the profile storage unit 18A. The result is (C1, M1, K1, Y1). Further, from the spot color correction table in the spot color correction table storage unit 21A, the difference value between the device color at the time of initial printer profile creation and the device color in the current state (C2-C1, M2-M1, Y2-Y1, K2-K1) is obtained.

  In step 143, for the eight points P11 to P18 that surround the target color (L1, a1, b1) in the Lab color space by the grid of the three-dimensional lookup table of the initial profile, (C2-C1, M2- M1, Y2-Y1, K2-K1) are added, and the process proceeds to step 144.

  In step 144, color matching is performed by the color management processing unit 18, and the process is terminated.

(Other examples)
In the present embodiment, a color sensor (RGB) is exemplified as the output patch reading means, but a colorimeter capable of measuring chromaticity can be used instead.
Further, in this embodiment, processing by one site is cited, but by using a colorimeter that automatically measures color, such as a color sensor, a plurality of sites connected by a large-scale network such as a WAN. It is also possible to perform remote processing on a network constituted by

  In this embodiment, the target color is specified by the color number of the color chart. However, the target color can be extended to a spot color correction table using device-independent color values as indexes.

It is a figure which shows the structure of the network system by one Example of this invention. 2 is a diagram illustrating a configuration of a front-end server 1 and a printer engine 2. FIG. It is a flowchart of a color management process. It is an example of a spot correction table. It is a schematic diagram of Lab color space explaining one Example of this invention. It is an example of the color sensor used in this invention. It is a figure which shows the internal structure of job data. It is a figure which shows the internal structure of job ticket data. It is a figure which shows the setting regarding the spot color correction in job ticket data. It is a flowchart of the main process of this invention. 10 is a flowchart showing details of processing for analyzing a job ticket in step 102. 10 is a flowchart showing details of color patch data creation processing in step 103; 10 is a flowchart showing details of a process for releasing a job hold in step 109; 12 is a flowchart showing details of CMS processing by a spot color correction table in step 133.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Network I / F part 11 Job control part 11A Job management part 11B Job analysis part 12 PDL interpreter part 13 Intermediate data storage part 14 Rendering part 15 (Front end server 1) Communication I / F part 16 Target value storage part 17 Color patch Generation unit 17A Color patch data storage unit 18 Color management processing unit 18A Profile storage unit 18B Calibration one-dimensional LUT
DESCRIPTION OF SYMBOLS 19 Device color patch data storage part 20 Device color estimation part 20A Device color storage part 21 Spot color correction table adjustment part 21A Spot color correction table storage part 22 Colorimetric value storage part 23 (Printer engine 2) Communication I / F part 24 Output Section 25 Color sensor control section 26 Color sensor 27 (Printer engine 2) Colorimetric value storage section 28 Color sensor 28A Light emitting element 28B Light receiving element 28C Holder 29 Transfer belt

Claims (7)

In a system that outputs a color image to a printer by color matching using a printer profile,
Means for providing job color data with spot color correction setting information;
Means for temporarily holding the job and analyzing the spot color correction setting information in the job ticket data;
Means for performing a spot color correction process to realize the target value described in the spot color setting information;
Means for creating a spot color correction table from the result of the spot color correction process;
And a means for releasing the held job and applying the spot color correction table to the job and outputting the job.   The spot color correction method according to claim 1, wherein the spot color correction setting information includes spot color correction flag information and an identifier of a color to be corrected. The spot color correction process includes
Means for generating device-independent color space color patch data corresponding to the target color described in the job ticket data;
Means for converting the color patch data into device color patch data which is a chart of a printer device-dependent color space;
Means for outputting the device color patch data from a printer and generating a device color patch chart;
Color measuring means for measuring the device color patch chart automatically or manually;
The spot color correction method according to claim 1, further comprising means for estimating a device color for realizing a target value based on the color measurement result.   2. The spot color correction method according to claim 1, wherein the spot color correction table holds a difference value from the printer profile corresponding to the target color.   4. The spot color correction process according to claim 3, wherein the device color patch chart is an 8-point C, M, Y, and K multi-order color patch chart.   4. The spot color correction process according to claim 3, wherein the color measurement means is an RGB output color sensor, colorimeter, or densitometer.   After releasing the held job, in the output operation, the difference value with the printer profile corresponding to the target color is referred to from the spot color correction table, and the lookup that includes the target color in the device-independent color space 2. The spot color correction method according to claim 1, wherein correction is performed by adding the difference value to eight grid points of the table, and the correction is applied to a job.

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