JP6041633B2 - Color image processing apparatus, control method therefor, and program for executing image processing method - Google Patents

Description

  The present invention relates to a color image processing apparatus for correcting the color of an image output from a printer, a control method therefor, and a program for creating image processing parameters.

  In recent years, machines that have achieved image quality equivalent to that of printing presses have appeared along with improvements in the performance of electrophotographic apparatuses. However, due to the instability unique to electrophotography, the problem remains that the amount of color variation is larger than that of a printing press. Therefore, various calibration techniques are installed in the conventional electrophotographic apparatus.

  Therefore, in a conventional electrophotographic apparatus, calibration for creating a one-dimensional tone correction LUT (Look Up Table) corresponding to each toner of cyan, magenta, yellow, and black in order to perform primary color correction. Technology. The LUT is a table indicating output data corresponding to input data divided at specific intervals, and can express non-linear characteristics that cannot be expressed by arithmetic expressions. When this “single color” calibration (hereinafter referred to as “single color calibration”) indicating colors expressed using single toners of C, M, Y, and K is executed, the reproduction characteristics of single colors such as maximum density and gradation are obtained. It is corrected.

  In recent years, Patent Document 1 has proposed a technique for performing “mixed color” calibration using a four-dimensional LUT. Here, “mixed color” refers to a color using a plurality of toners such as red, green, and blue using two of C, M, and Y, and gray using CMY. In particular, in electrophotography, even if the gradation characteristics of a single color are corrected with a one-dimensional LUT, if “mixed color” is expressed using a plurality of toners, nonlinear differences often occur. Here, when color mixture calibration is executed, the color reproduction characteristics of the color mixture expressed by a combination (such as superposition) of a plurality of color toners are corrected.

  A calibration flow including “mixed colors” will be described. First, a patch image is printed out on a recording medium such as paper using chart data composed of a single color in order to perform “single color” calibration. This patch image is a measurement image having a predetermined area with a single density. A plurality of patch images having different colors are generated, and the generated patch image printed on a recording medium is called a pattern image. A recording medium such as paper on which the pattern image is printed is read by a scanner or a sensor, and the patch image is read. Data obtained by reading the patch image is compared with a preset target value to create a one-dimensional LUT for correcting a difference from the target value. Next, a patch image is printed out on a recording medium using chart data composed of mixed colors reflecting the one-dimensional LUT created previously in order to perform “mixed color” calibration. Read the image. Data obtained by reading the patch image is compared with a preset target value to create a four-dimensional LUT that corrects the difference from the target value.

  In general, in consideration of the reproducibility of the color output from the electrophotographic apparatus, it is indispensable to take into account the influence due to the difference in the image processing method that is a method for expressing the pseudo gradation. The image processing method mainly has two types of patterns of error diffusion and dither for performing pseudo gradation processing. The gradation characteristics differ between error diffusion and dither as the image processing methods, and the color reproducibility also differs when the image processing methods are different. Therefore, a correction LUT is required for each image processing method. That is, it is necessary to perform calibration for all image processing methods. However, performing calibration for all image processing methods not only takes time and effort, but also consumes a lot of consumables such as paper and toner. Therefore, a method for performing simple color calibration as simply as possible has also been proposed. In Patent Document 2, single-color calibration is executed only for one type of image processing method, and a correction LUT for other image processing methods includes a conversion table between image processing methods created in advance by experiments. To make it. As a result, the LUT can be created without bothering the user.

JP 2011-254350 A JP 2000-101836 A

  However, in the prior art, the single color calibration that should be performed for each image processing method is simplified while maintaining the accuracy as much as possible. Therefore, in the method disclosed in the prior art, there is a problem that the color reproduction characteristics are not guaranteed at all.

  Generally, when color mixture calibration is performed following single color calibration, the number of sheets to be used and toner increase. In addition, when trying to perform color mixture calibration, in addition to consumables such as paper and toner, the time required for executing calibration and the time and effort of the user are greatly increased.

In order to solve the above problems, a color image processing apparatus of the present invention, an image forming means for forming a color image on a sheet using a record agent image to perform image processing for expressing pseudo Nikaicho A processing unit; a colorimetric unit that performs colorimetry on image data obtained by reading a color image formed on the sheet by the image forming unit ; and a pattern image that includes a plurality of single-color patch images formed on the sheet. The color measurement unit measures the color of the obtained image data, and uses the color measurement result to generate data for correcting the color of the monochrome image formed by the image forming unit to a target color. and Deployment means, and colorimetry by the colorimetric unit image data obtained by reading a pattern image including a plurality of patch images mixed color formed on the sheet, before using the results of surveying color And a multi-color calibration means for performing the multi-color calibration for generating data for correcting the color of the mixed color image by the image forming means forms the target of a color patch image used for the single-color calibration, different A patch image formed by executing image processing for representing different types of pseudo gradations and used for the color mixture calibration is performed using the data for correcting the color of the monochrome image to a target color. It is formed by executing one image processing among the image processing for expressing the different types of pseudo gradations used in the execution of the calibration .

  According to the present invention, it is possible to suppress the increase in the consumption of paper and toner and the trouble for the user, and to correct the color mixing reproduction characteristics efficiently.

It is a block diagram of a system. It is the figure which showed the flow of the image processing. It is the figure which showed the flow of the monochromatic calibration. FIG. 5 is a diagram illustrating a flow of color mixture calibration. It is the figure which showed the chart image used for single color calibration and mixed color calibration. 3 is a flowchart of a processing procedure in the first embodiment. 10 is a flowchart of a processing procedure in the second embodiment. 10 is a flowchart of a processing procedure in the second embodiment. It is a figure which shows an example of a dither matrix. It is the figure which showed the single color calibration and the mixed color calibration execution screen.

Example 1
First, mixed color calibration, which is a feature of the present embodiment, will be described in comparison with single color calibration. As described above, when the color mixture calibration is performed, it is assumed that the single color calibration is completed and the gradation of the single color is corrected. Since the reproduction characteristics of a single color are easily affected by the image processing method, it is necessary to perform the single color calibration for each type of image processing method. Furthermore, since the color reproducibility of the highlight is unstable, it is required to increase the patch image in the highlight area, for example.

  On the other hand, in the mixed color, since the C, M, Y, and K color plates are overlapped, the influence of transfer and fixing during printing greatly contributes to the color.

  That is, the mixed color patch image formed at the time of executing the mixed color calibration has overlapping color plates and a high halftone dot ratio (10 to 15% or more). Therefore, the color difference generated according to the difference in the image processing method is a single color patch. Less than during image formation.

  From the above, unlike the single color calibration that corrects the difference due to the image processing technique or corrects the gradation, the mixed color calibration can be said to be a process that corrects a deviation in reproduction characteristics caused by a change in the engine state.

  In contrast to using only a single color in the single color calibration, the mixed color calibration corrects using a color in which C, M, Y, and K are mixed.

  Therefore, it is easy for the amount of toner used when printing a chart image used when performing mixed color calibration to be larger than the amount of toner used when printing a chart image used when performing single color calibration. Conceivable.

  Further, if the single color calibration and the mixed color calibration are performed for each image processing method, it is easy to think that the number of sheets on which the output chart image is printed increases.

  In view of the above, this embodiment is characterized in that single color calibration is performed for all image processing methods, and color mixture calibration is performed using only one type of image processing method. This proposes an efficient calibration flow that maintains the accuracy of color mixture calibration and suppresses the consumption of paper and toner as much as possible.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration diagram of a system in this embodiment. An MFP (Multi Function Printer) 101 of a color image processing apparatus that uses cyan, magenta, yellow, and black (hereinafter, C, M, Y, and K) toners is connected to other network compatible devices via a network 123. Yes. The PC 124 is connected to the MFP 101 via the network 123. A printer driver 125 in the PC 124 transmits print data to the MFP 101.

  The MFP 101 will be described in detail. The network I / F 122 receives print data and the like. The controller 102 includes a CPU 103, a renderer 112, and an image processing unit 114. The interpreter 104 of the CPU 103 interprets the PDL (page description language) portion of the received print data and generates intermediate language data 105.

  The CMS 106 performs color conversion using the source profile 107 and the destination profile 108 to generate intermediate language data 111 (after CMS). Here, “CMS” is an abbreviation of “Color Management System”, and color conversion is performed using profile information described later. The source profile 107 is a device-independent color space such as L * a * b * (hereinafter referred to as Lab) or XYZ defined by the CIE (International Lighting Commission) as a device-dependent color space such as RGB or CMYK. This is a profile for conversion. XYZ is a device-independent color space like Lab, and expresses colors with three types of stimulus values. The destination profile 108 is a profile for converting the device-independent color space into a CMYK color space depending on the device (printer 115).

  On the other hand, the CMS 109 performs color conversion using the device link profile 110 to generate intermediate language data (after CMS) 111. Here, the device link profile 110 is a profile for directly converting a device-dependent color space such as RGB or CMYK into a CMYK color space depending on the device (printer 115). Which one of the CMS 106 and the CMS 109 is selected depends on the setting in the printer driver 125.

  In this embodiment, the CMSs (106 and 109) are divided according to the types of profiles (107, 108 and 110), but a plurality of types of profiles may be handled by one CMS. The type of profile is not limited to the example given in the present embodiment, and any type of profile may be used as long as the device-dependent CMYK color space of the printer 115 is used.

  The renderer 112 generates a raster image 113 from the generated intermediate language data (after CMS) 111. The image processing unit 114 performs image processing on the raster image 113 and the image read by the scanner 119. Details of the image processing unit 114 will be described later.

  A printer 115 connected to the controller 102 is a printer that forms color images using output data on paper using colored toners such as C, M, Y, and K. The printer 115 includes a paper feed unit 116 that feeds paper, a paper discharge unit 117 that discharges paper on which an image is formed, and a measurement unit 126.

  The measurement unit 126 includes a color measurement unit sensor 127 that can acquire spectral reflectance, a color space value independent of devices such as Lab and XYZ, and is controlled by the CPU 129 that controls the printer 115. The measuring unit 126 measures the patch image printed on the recording medium such as paper by the printer 115. This patch image is a measurement image having a predetermined area with a single density. A plurality of patch images having different colors are generated, and the generated patch image printed on a recording medium is called a pattern image. The pattern image is read by the sensor 127 included in the measurement unit 126, and the read numerical information is transmitted to the controller 102. The controller 102 performs a calculation using the numerical information, and uses the result of this calculation when executing a single color calibration or a mixed color calibration.

  A display device 118 is a UI (user interface) that displays instructions to the user and the state of the MFP 101. This is used when executing single color calibration or mixed color calibration described later.

  The scanner 119 is a scanner including an auto document feeder. The scanner 119 irradiates a bundle or one original image with a light source (not shown), and forms an image of an original reflection on a solid-state imaging device such as a CCD (Charge Coupled Device) sensor with a lens. Then, a raster-like image reading signal is obtained as image data from the solid-state imaging device.

  The input device 120 is an interface for receiving input from the user. Some input devices may be touch panels and integrated with the display device 118.

  The storage device 121 stores data processed by the controller 102, data received by the controller 102, and the like.

  The measuring device 128 is an external measuring device connected to the network or the PC 124, and can acquire a spectral reflectance, a color space value independent of devices such as Lab and XYZ, like the measuring unit 126.

  Next, the flow of the image processing unit 114 will be described with reference to FIG. FIG. 2 shows the flow of image processing performed on the raster image 113 and the image read by the scanner 119. The processing flow in FIG. 2 is realized by executing an ASIC (Application Specific Integrated Circuit) (not shown) in the image processing unit 114.

  In step S201, image data is received. In step S202, it is determined whether the received data is the scan data received from the scanner 119 or the raster image 113 sent from the printer driver 125.

  If it is not scan data, it is a raster image 113 that has been bitmap-developed by the renderer 112 and a CMYK image 211 that has been converted to CMYK depending on the printer device by the CMS.

  Since the scan data is an RGB image 203, color conversion processing is performed in step S204 to generate a common RGB image 205. Here, the common RGB image 205 is defined in a device-independent RGB color space, and can be converted into a device-independent color space such as Lab by calculation.

  On the other hand, character determination processing is performed in step S206 to generate character determination data 207. Here, the character determination data 207 is generated by detecting an edge or the like of the image.

  In step S208, the common RGB image 205 is filtered using the character determination data 207. Here, the character determination data 207 is used to perform different filter processing for the character portion and other portions.

  Next, a background removal process is performed in step S209, and a color conversion process is performed in step S210 to generate a CMYK image 211 with the background removed.

  In step S212, color mixture correction processing using the 4D-LUT 217 is performed. The 4D-LUT is a four-dimensional LUT (Look Up Table) that converts a combination of signal values when outputting each C, M, Y, and K toner into a combination of different C, M, Y, and K signal values. It is. The 4D-LUT 217 is generated by “mixed color calibration” to be described later. By using the 4D-LUT, it is possible to correct “mixed color” which is a color using a plurality of toners.

  Then, after correcting the color mixture in step S212, the image processing unit 114 corrects the gradation characteristics of each single color of C, M, Y, and K using the 1D-LUT 218 in step S213. The 1D-LUT is a one-dimensional LUT (Look Up Table) that corrects each color (single color) of C, M, Y, and K. This 1D-LUT is generated by “single color calibration” to be described later.

  Finally, in step S214, the image processing unit 114 performs halftone processing such as screen processing and error diffusion processing to create a CMYK image (binary) 215, and transmits the image data to the printer 115 in step S216.

  “Monocolor calibration” for correcting the monochromatic gradation characteristics output from the printer 115 will be described with reference to FIG. By executing the single color calibration, the single color reproduction characteristics such as the maximum density characteristic and the gradation characteristic are corrected. The color reproduction characteristics corresponding to the C, M, Y, and K toners used in the printer 115 are corrected together when the calibration is executed. That is, the processing of FIG. 3 is executed at a time according to each color of C, M, Y, and K.

  FIG. 3 shows the flow of processing for creating a 1D-LUT 218 that corrects the gradation characteristics of a single color. The processing flow in FIG. 3 is realized by the CPU 103 executing, and the created 1D-LUT 218 is stored in the storage device 121. In addition, the display device 118 displays an instruction to the user on the UI, and receives the user's instruction from the input device 120.

  In step S301, chart data (A) 302 stored in the storage device 121 is acquired. The chart data (A) 302 is for correcting the maximum density of each single color, and is composed of signal values (for example, 255) from which C, M, Y, and K “single color” maximum density data can be obtained.

  In step S303, the image processing unit 114 executes image processing on the chart data (A) 302, and the printer 115 prints out a chart image (A) 304 that is a pattern image. An example is shown in FIG. 501 in FIG. 5A shows an example when the chart data (A) 302 is printed out, and the patch images 502, 503, 504, and 505 are printed at the maximum densities of C, M, Y, and K colors, respectively. Is output. Thus, the chart image (A) 304 that is a pattern image includes a plurality of patch images. Here, the image processing unit 114 performs only halftone processing in step S214, and does not perform 1D-LUT correction processing in step S213 or 4D-LUT correction processing in step S212.

  In step S305, the density of the printed output of the chart image (A) 304 is measured using the scanner 119 and the sensor 127 in the measurement unit 126, and a measurement value (A) 306 is obtained. The measured value (A) 306 is a density value for each color of C, M, Y, and K. In step S307, correction of the maximum density of the measurement value (A) 306 for each color is executed using the measurement value (A) 306 and a preset target value (A) 308 of the maximum density value. Here, a device setting value of the printer 115, for example, a laser output and a developing bias is adjusted so that the maximum density approaches the target value 308 (A).

  Next, chart data (B) 310 stored in the storage device 121 is obtained in step S309. The chart data (B) 310 is composed of C, M, Y, and K “monochromatic” gradation data signal values. FIG. 5 shows an example of a chart image (B) 312 which is a pattern image having a patch image printed out on a recording medium using the chart data (B) 310. Reference numeral 506 in FIG. 5B shows an example of a printed output of a chart image (B) 312 having a patch image printed on a recording medium using the chart data (B) 310. The patch images 507, 508, 509, 510 shown in FIG. 5B and the gradation data following to the right are composed of gradation data of C, M, Y, and K colors. Thus, the chart image (B) 312 which is a pattern image includes a plurality of patch images.

  In step S <b> 311, the image processing unit 114 executes image processing on the chart data (B) 310 and prints out the chart image (B) 312 from the printer 115. Here, only the halftone process is performed in the image processing unit 114 and step S214, and the 1D-LUT correction process in step S213 and the 4D-LUT correction process in step S212 are not performed. Further, since the printer 115 performs the maximum density correction in step S307, the maximum density can be set to a value equivalent to the target value (A) 308.

  Next, in step S313, measurement is performed using the scanner 119 and the sensor 127, and a measurement value (B) 314 is obtained. The measured value (B) 314 is a density value obtained from the gradation of each color of C, M, Y, and K. Next, in step S315, a 1D-LUT 218 that corrects a monochrome gradation is created using the measured value (B) 314 and a preset target value (B) 316.

  Next, “mixed color calibration” for correcting the mixed color characteristics output from the printer 115 will be described with reference to FIG. By executing the color mixture calibration, the reproduction characteristics of the color mixture expressed by a combination of toners of a plurality of colors (superposition, etc.) are corrected. The following processing flow is realized by the CPU 103 in the controller 102 executing. The acquired 4D-LUT 217 is stored in the storage device 121. In addition, the display device 118 displays an instruction to the user on the UI, and receives the user's instruction from the input device 120.

  The color mixture calibration corrects the color mixture output from the printer 115 after the single color calibration is performed. Therefore, it is desirable to perform mixed color calibration immediately after performing single color calibration.

  In step S401, information of the chart data (C) 402 configured by “color mixing” stored in the storage device 121 is acquired. Chart data (C) 402 is data for correcting mixed colors, and is composed of “mixed color” signal values that are combinations of C, M, Y, and K. An example of a chart image (C) 404 that is a pattern image having a plurality of patch images printed out on a recording medium using the chart data (C) 402 is shown in FIG. 511 in FIG. 5C shows an example when the chart data (C) 402 is printed out, and all patch images printed on the patch images 512 and 511 are combinations of C, M, Y, and K. It is composed of mixed colors. Thus, the chart image (C) 404 that is a pattern image includes a plurality of patch images.

  In step S403, the image processing unit 114 performs image processing on the chart data (C) 402, and the printer 115 prints out the chart image (C) 404. Since the color mixture calibration corrects the color mixture characteristics of the device after the single color calibration, the image processing unit 114 uses the 1D-LUT 218 created when the single color calibration is executed.

  Next, in step S405, the mixed color of the printed output of the chart image (C) 404 is measured using the scanner 119 and the sensor 127 in the measurement unit 126, and the measurement value (C) 406 is acquired. A measured value (C) 406 indicates the color mixing characteristics of the printer 115 after the single color calibration is performed. The measured value (C) 406 is a value in a color space that does not depend on the device, and is Lab in this embodiment. When the scanner 119 is used, RGB values are converted into Lab values using a 3D-LUT (not shown) or the like.

  Next, in step S407, the Lab → CMY 3D-LUT 409 stored in the storage device 121 is acquired, and the difference between the measured value 406 (C) and the preset target value (C) 408 is reflected. → CMY 3D-LUT (after correction) 410 is created. Here, the Lab → CMY 3D-LUT is a three-dimensional LUT that outputs a CMY value corresponding to an input Lab value.

  The specific creation method is shown below. The difference between the measured value 406 (C) and the preset target value (C) 408 is added to the Lab value on the input side of the Lab → CMY 3D-LUT 409, and Lab is applied to the Lab value reflecting the difference. → Interpolation is executed using the 3D-LUT 409 of CMY. As a result, a Lab → CMY 3D-LUT (after correction) 410 is created.

  In step S 411, the CMY → Lab 3D-LUT 412 stored in the storage device 121 is acquired, and the calculation is performed using the Lab → CMY 3D-LUT (after correction) 410. As a result, a CMYK → CMYK 4D-LUT 217 is created. Here, the CMY → Lab 3D-LUT is a three-dimensional LUT that outputs a Lab value corresponding to an input CMY value.

  A specific method for creating the CMYK → CMYK 4D-LUT 217 will be described below. A CMY → CMY 3D-LUT is created from the CMY → Lab 3D-LUT 412 and the Lab → CMY 3D-LUT (after correction) 410. Next, a 4D-LUT 217 of CMYK → CMYK is created so that the input value and output value of K are the same. Here, the CMY → CMY 3D-LUT is a three-dimensional LUT that outputs a corrected CMY value corresponding to the input CMY value.

FIG. 10 shows an example of UI display when the single color calibration and the mixed color calibration are selectively executed. A UI screen 1001 in FIG. 10 is displayed on the display device 118. Reference numeral 1002 denotes a button for accepting the start of monochromatic calibration, and reference numeral 1003 is a button for accepting the start of color mixture calibration. Reference numeral 1004 denotes a button for accepting the start of calibration for executing the mixed color calibration after the single color calibration.

  When the button 1004 is selected, the single color calibration is started and executed, and then the mixed color calibration is started.

  Specifically, after completion of the single color calibration, the mixed color calibration is started by printing out the chart image (C) 404 for the mixed color calibration. Alternatively, the user may display a button for starting the color mixture calibration on the UI screen, and the color mixture calibration may be started after the user presses the button.

  On the other hand, when the button 1002 is selected, only single color calibration is executed. Similarly, when the button 1003 is selected, only the color mixture calibration is executed.

  The reason why the buttons are divided for single color calibration and mixed color calibration will be described. When the chart image (C) 404 used for executing the color mixture calibration is printed out, the 1D-LUT 218 created by the single color calibration is used. Therefore, it is desirable to correct the mixed color reproduction characteristic by performing the mixed color calibration immediately after the single color calibration and immediately after the single color reproduction characteristic is corrected. However, if both types of calibration are executed, it takes a long processing time for the user to calibrate.

  Therefore, in order to shorten the processing time, either single color calibration or mixed color calibration is executed according to the user's usage environment. Then, the situation where the execution frequency of both calibrations differs occurs. For example, a user who frequently performs monochrome printing has a low frequency of executing the color mixture calibration. In addition, a user who frequently performs mixed color printing such as a photograph has a higher frequency of executing mixed color calibration.

  Further, the timing at which this color correction menu can be selected may be controlled.

  Usually, image processing apparatuses are often turned off at night and turned on in the morning. Therefore, when the main power switch of the MFP 101 is turned on and the power is turned on, only the button 1004 can be selected. Alternatively, if both calibrations are not executed within a predetermined time, only the button 1004 may be selected. Alternatively, if both calibrations are not executed before printing is performed using a predetermined number of sheets, only the button 1004 may be selected.

  Alternatively, when a predetermined time has elapsed, printing is performed using a predetermined number of sheets, or power is turned on, the single color calibration and the mixed color calibration are automatically performed sequentially. May be.

  As described above, when the user performs calibration at a predetermined timing, only the button 1004 can be selected, and the user is prompted to perform the color mixture calibration immediately after the monochrome calibration is performed at predetermined time intervals. .

  Therefore, as described above, it is possible to select whether to execute both color calibrations by executing the color mixture calibration after executing the single color calibration, or to execute either the single color calibration or the color mixing calibration. This makes it possible to execute calibration suitable for the user's use.

  In addition, by controlling so that only both calibrations can be selected at regular time intervals, only one of the calibrations is executed, thereby suppressing a reduction in the correction accuracy of reproduction characteristics due to calibration. Is possible. In the present embodiment, when 1004 in FIG. 10 is selected and an instruction is given to execute the mixed color calibration after the single color calibration is executed, the operation shown in FIG. 6 is executed.

  FIG. 6 is a flow showing the processing flow of the present embodiment. A control program (not shown) that implements the present embodiment is stored in the storage device 121, loaded into a RAM (not shown), and executed by the CPU 103.

  This technique will be described along the flow of the flowchart of FIG. First, in S600, the single color calibration shown in FIG. 3 is executed. At this time, in the execution and output of the image processing in S311, the image processing unit 114 performs any kind of image processing technique, and the 1D-LUT 218 is created after S315. Next, it is determined whether or not the 1D-LUT 218 has been generated by all types of image processing methods applied in S601. If the 1D-LUT 218 of all types of image processing methods to be applied has not been updated, the process returns to S600 and the monochromatic calibration is continued. At that time, the maximum density correction (S301 to S307) is not performed, but the gradation correction of S309 is executed. This is because the correction result of the maximum density is the same no matter what image processing method is used to update the 1D-LUT using the chart image.

  At this time, in the execution and output of the image processing in S311, an image processing method that has not yet output a chart image for executing the monochromatic calibration in the image processing unit 114 is selected.

  Multiple image processing methods are available, such as those applied when processing scan data, those applied when processing raster data such as bitmaps in PDL jobs, and those applied when processing character parts. . Therefore, S600 is repeated a plurality of times in order to update the 1D-LUT 218 corresponding to each of a plurality of types of image processing methods prepared. Alternatively, when the use application is designated in advance and the calibration is started, the calibration may be repeated using only the chart image output by the image processing method of the designated use until the calibration is completed.

  A specific example of the image processing method will be described with reference to FIG. FIG. 9 shows an example of dither generated by pseudo gradation processing executed using dither matrices having different numbers of lines and different angles. The image processing method 1 with the lowest number of lines has high stability, and the image processing method 2 with a slightly higher number of lines is less likely to cause interference with the period of the input image than the image processing method 1. The image processing method 3 having the highest number of lines improves the smoothness of the character edge. As described above, each image processing method has unique characteristics, and an optimum one is used depending on the job type and object of the output image. Details of the image processing method for the color mixture chart will be described later.

  When it is determined in S601 that the 1D-LUT 218 of all image processing methods has been updated, the process proceeds to S602, and the image processing method of the chart image used for the color mixture calibration is determined. As described above, there are a plurality of image processing methods, but one of them may be selected, or an image processing method for color mixture correction may be set in advance. FIG. 9A shows a dither matrix used in the former case. That is, the image processing method 2 having an intermediate number of lines is selected from among the image processing methods used when creating the chart image used for the single color calibration, and the chart image used for the mixed color calibration is output. Used when. FIG. 9B shows a dither matrix used in the latter case. That is, an image processing method for outputting a chart image used for color mixture calibration is prepared separately from the image processing method used for creating a chart image used for single color calibration. In this case, out of a plurality of usable image processing methods, a method other than the first image processing method is used when outputting a chart image used for monochromatic calibration. The first image processing method is used when outputting a chart image used for color mixture calibration.

  Further, the image processing method selected when outputting the chart image used for the color mixture calibration is usually determined in advance, and the user may arbitrarily switch the selection. Note that dithers used in each image processing method are usually different for C, M, Y, and K, respectively. Although typical types are shown in FIG. 9 to show the characteristics of the image processing technique, in practice, a predetermined combination of C, M, Y, and K image processing techniques is selected as a set. . Hereinafter, the image processing technique refers to a set of C, M, Y, and K image processing techniques.

  When the image processing method is determined in S602, the process proceeds to S603, and color mixture calibration is executed. The details of the color mixture calibration executed in S603 are as shown in FIG. 4, but when the image processing is executed in S403, image processing using the color mixture image processing method determined in S602 is performed. The change in the color mixture largely reflects the change in the engine state rather than the difference between the image processing methods. Therefore, by correcting each color with only one type of image processing method, the effect of color mixture calibration can be obtained. In addition to the dither method shown in FIG. 9, there may be a plurality of image processing methods such as an error diffusion method and an FM screen method.

  As described above, in this embodiment, in the mixed color calibration, correction is not performed using a plurality of chart images output by all image processing methods, but a chart output by one selected image processing method. Correction is performed using only the image. Thereby, while obtaining the effect of correction, it is possible to suppress an increase in the amount of paper and toner to be used, and to correct the color mixture reproduction characteristics without increasing the user's trouble.

  Furthermore, in the present case, when performing the monochromatic calibration, the monochromatic reproduction characteristics are corrected using the results measured using the chart images created using all the image processing techniques.

  Therefore, since the reproduction characteristics of the single color can be corrected with high accuracy, it is possible to maintain the accuracy of the correction by the color mixture calibration that is premised on that the single color calibration is appropriately performed.

(Example 2)
Here, only a different part from Example 1 is demonstrated. In the present embodiment, the usage situation of the user is analyzed, and color mixture calibration is performed using the chart image output by the image processing method used most frequently. It can be said that the reproduction characteristics of the mixed colors are not easily influenced by the difference in the image processing method. However, as a matter of course, correction can be performed with the highest accuracy with respect to the image processing method used when the chart image for calibration is output. Therefore, by outputting a chart image for color mixture calibration using an image processing technique that is frequently used by the user, it is possible to perform color mixture calibration that is most effective for the user.

  FIG. 7 is a flow showing the processing flow of the present embodiment. The difference from the first embodiment is that the use situation of the user is analyzed in S701 before the color mixture calibration. User usage situation analysis S701 will be described in detail with reference to FIG.

  FIG. 8 is a data collection flow for performing the user usage analysis S701. The program for performing the user usage state analysis S701 is stored in the storage device 121, loaded into a RAM (not shown), and executed by the CPU 103. An example of printing a raster image 113 sent from the printer driver 125 will be described. First, in step S801, whether there are a plurality of image processing methods used when printing one page of image data, that is, whether there is switching of image processing methods when forming one page of image data to be printed. Determine. Since the switching of the image processing method is generally performed based on the image area data of the input image, it is determined by referring to the image area data whether or not the image processing method is switched. Alternatively, if it can be determined from other output settings whether or not there is a change in the image processing method, it may be used. If it is determined in S801 that there is no switching of the image processing method in the page, the process proceeds to S804. In step S804, only one type of image processing technique used during output is counted. The count result is stored in the storage device 121. On the other hand, if it is determined in S801 that the image processing method is switched in the page, the process proceeds to S802.

  In step S802, the usage rate (in-page usage rate) of various image processing methods in the page is acquired.

  The in-page usage rate indicates a rate at which each of the image processing methods is used when printing one page.

  If the in-page usage rate of each image processing method acquired in S802 is equal to or greater than the threshold value in any image processing method, the process proceeds to S803. In step S803, all image processing methods used are counted. On the other hand, when only the in-page usage rate of the specific image processing method is equal to or greater than the threshold among the in-page usage rates of the respective image processing methods acquired in S802, the process proceeds to S804. In step S804, only specific image processing methods with a high in-page usage rate are counted. A threshold for determining whether the in-page usage rate is high is determined in advance. For example, when 30% or the like is set, it is determined that an image processing method with an in-page usage rate of 30% or more is an image processing method with a high in-page usage rate, and an image processing method with an in-page usage rate of 30% or less is a page. It is determined that the image processing method has a low internal usage rate.

  Returning to the flow of FIG. 7, in S <b> 702, the image processing method that is most frequently used in the data collection period is determined from the data collected in S <b> 701.

  The overall usage rate of image processing methods is calculated by calculating the number of times each image processing method was used (count number) against the number of times all types of image processing methods were used (total number of counts). The usage rate of the method is obtained. The counting period (data collecting period) may be from the previous execution of the color mixture calibration until the user usage state is analyzed in S701, for example, every period predetermined as one month, for example. But you can. When the number of people sharing the electrophotographic apparatus is small, it is considered effective to employ the number of counts acquired in a short period.

  In step S703, color mixture calibration is performed. The details are as shown in FIG. 4, but the image processing method determined in S702 is applied when the image processing is executed in S403.

  In the description of the present embodiment, as shown in FIG. 8, the method of determining whether or not the image processing method is switched when printing one page and counting the image processing method is described. However, the image processing method is used. If there is another effective method that can extract the frequency, it may be used. For example, when the image processing method differs between a copy job and a PDL job, a method of counting the switching of the image processing method for each job type is also effective. As described above, by analyzing the user's usage status and performing color mixture calibration using the chart image created by the most frequently used image processing method, an image of features frequently seen by the user Therefore, it is possible to correct the reproduction characteristics of the color mixture most suitable for the color.

(Other examples)
The present invention is also realized by executing the following processing. That is, software (program) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

  Further, although the electrophotographic apparatus has been described as an example of the above embodiment, an ink jet printer, a thermal printer, or the like may be used, and the gist of the present invention is not limited to the type of printer. Further, the toner in electrophotographic printing has been described as an example of the recording agent. However, the recording agent used for printing is not limited to the toner, and may be other recording agents such as ink. The gist of the present invention is the kind of the recording agent. It is not limited to.

Claims (6)

Image forming means for forming a color image on a sheet using a record agent,
Image processing means for performing image processing for expressing pseudo Nikaicho,
Colorimetric means for measuring the color of image data obtained by reading a color image formed on the sheet by the image forming means;
A single-color image formed by the image forming unit using the colorimetric unit for color measurement of image data obtained by reading a pattern image including a plurality of single-color patch images formed on the sheet. Monochrome calibration means for generating data for correcting the color of the target to the target color;
A color mixture image formed by the image forming unit using the color measurement unit that performs color measurement on image data obtained by reading a pattern image including a plurality of color mixture patch images formed on the sheet. Color mixing calibration means for executing color mixing calibration for generating data for correcting the color of the target color to a target color ,
The patch image used for the monochrome calibration is formed by executing image processing for expressing different types of pseudo gradations, and the patch image used for the color mixture calibration targets the color of the monochrome image. It is formed by executing one image process among the image processes for expressing the different types of pseudo gradations used in the execution of the single color calibration using the data to be corrected to the color of A color image processing apparatus. The color image processing apparatus according to claim 1, wherein the one image processing is preset image processing. It further has an acquisition means for acquiring the usage rate of the image processing,
Determining means for determining the one image processing used when executing the color mixture calibration based on the usage rate acquired by the acquiring means;
2. The color image according to claim 1, wherein the color mixture calibration is executed using a pattern image including a plurality of color mixture patch images output by using one image processing determined by the determination unit. Processing equipment. The color image processing apparatus according to claim 1, wherein the different image processing includes image processing using a dither method or an error diffusion method. An image forming step of forming a color image on a sheet using a recording agent;
An image processing step of performing image processing for expressing pseudo Nikaicho,
A colorimetric step for measuring the color of image data obtained by reading the color image formed on the sheet by the image forming step;
A color image of a pattern image including a plurality of single color patch images formed on the sheet is measured in the color measurement step, and a color of the single color image formed in the image formation step is set as a target color using the result of the color measurement. A single color calibration step for generating data for correction, and a color image of a pattern image including a plurality of mixed color patch images formed on the sheet are measured in the color measurement step, and the image is obtained using the result of the color measurement. A color mixture calibration step for executing color mixture calibration for generating data for correcting the color of the color mixture image formed in the formation step to a target color ;
The patch image used for the monochrome calibration is formed by executing image processing for expressing different types of pseudo gradations, and the patch image used for the color mixture calibration targets the color of the monochrome image. It is formed by executing one image process among the image processes for expressing the different types of pseudo gradations used in the execution of the single color calibration using the data to be corrected to the color of A method for controlling a color image processing apparatus. An image forming step of forming a color image on a sheet using a record agent,
An image processing step of performing image processing for expressing pseudo Nikaicho, a colorimetry step of colorimetric image data obtained by reading a color image formed on the sheet by the image forming step,
The pattern image including a plurality of single-color patch images formed on the sheet is measured by the color measurement step, and the color of the single-color image formed by the image forming unit is corrected to a target color using the color measurement result. A single color calibration step to generate data for
Image data obtained by reading a pattern image including a plurality of mixed-color patch images formed on the sheet is measured in the color measurement step, and formed in the image formation step using the color measurement result. A program for causing a computer to execute a color mixture calibration step for executing color mixture calibration for generating data for correcting the color of the color mixture image to a target color , and the patch image used for the single color calibration is: The patch image is formed by executing image processing for expressing different types of pseudo gradations, and the patch image used for the color mixture calibration uses the data for correcting the color of the single-color image to a target color. Of the image processing for expressing the different types of pseudo gradations used in the single color calibration, A program characterized by being formed by executing One of image processing.

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