JP2014099830A - Color image processing apparatus and image processing method, and program for performing image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: executing color mixture calibration in an electrophotographic device increases consumption of paper and toner.SOLUTION: A color image processing apparatus of the present invention includes: image forming means for forming a color image by using a plurality of colors of recording agents; image processing means for achieving a plurality of image processing techniques representing a plurality of types of pseudo gradations; color measurement means for measuring the color image; and control means for controlling execution of color mixture calibration to correct reproduction characteristics of a mixed color formed by the image forming means, by using a result of color measurement of a pattern image including a plurality of mixed-color patch images formed by the image forming means by using the plurality of colors of recording agents. The color mixture calibration is executed by using a result of measurement of a pattern image that is configured such that the number of patch images constituting a mixed-color pattern image formed by using an image processing technique that has been used at a lower rate when an image is formed by the image forming means, is smaller than the number of patch images constituting a mixed-color pattern image formed by using an image processing technique that has been used at a higher rate.

Description

  The present invention relates to a color image processing apparatus and image processing method for correcting the color of an image output from a printer, 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. The data obtained by reading the patch image is compared with a preset target value to create a one-dimensional LUT that corrects the 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 for one type of image processing method, and a correction table for other image processing methods uses a conversion table between image processing methods that has been created in advance by experiments. Is disclosed. As a result, the LUT can be created without bothering the user.

  In addition, when printing a chart image used for single color calibration, the pattern of the patch image printed on the chart image is changed from the preset one, and the chart image is reconstructed with the patch image of the color selected by the user. Printing is disclosed in Patent Document 3. When single color calibration is executed using the reconstructed chart image, it is possible to output the color selected by the user with high accuracy.

JP 2011-254350 A JP 2000-101836 A JP2011-242684A

  However, in the prior art described above, monochromatic calibration that should be originally 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-mentioned problems, the color image processing apparatus of the present invention realizes an image forming means for forming a color image using a plurality of color recording agents and a plurality of image processing techniques for expressing a plurality of types of pseudo gradations. A pattern including a plurality of color patch images formed by using the recording agent of a plurality of colors by the image forming unit, and a colorimetric unit for measuring the color image formed by the image forming unit. Control means for controlling the execution of color mixture calibration for measuring the color of the image by the color measurement means and correcting the reproduction characteristics of the color mixture formed by the image forming means using the result of the color measurement; and the image processing means. Among the generated image processing methods, an acquisition unit that acquires a usage rate of the image processing method used when an image is formed by the image forming unit, and an acquisition unit that acquires the usage rate of the image processing method. The number of patch images constituting the mixed color pattern image formed using the image processing method determined to have a low usage rate is the same as the image processing method determined to have a high usage rate acquired by the acquisition unit. A configuration means for configuring the pattern image so as to be smaller than the number of patches forming the mixed-color pattern image formed using
The control unit performs the color mixture calibration using a result of measuring a pattern image formed by the configuration unit.

  According to the present invention, it is possible to efficiently perform correction of mixed color reproduction characteristics suitable for the characteristics of the types of images that the user frequently sees, while suppressing the consumption of paper and toner and the effort required for the user. Become.

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. 3 is a flowchart of a processing procedure in the first embodiment. 6 is an example of a chart image reconstruction in the first 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 chart images to be output increases.

  In view of the above, in this embodiment, single color calibration is performed for all image processing methods, and mixed color calibration is performed by reconstructing a patch image in each image processing method, and performing charts more than when performing single color calibration. It is characterized by reducing the number of printed images.

  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, the correction can be most accurately performed with respect to the image processing method used when the calibration chart image is output. Therefore, the user's usage situation is analyzed to reconstruct the color mixture chart image. When this method is used, even when there are multiple image processing methods that are used frequently, it is possible to efficiently correct by reducing the amount of paper and toner used, and this is the most effective color mixing calibration for the user. Can be implemented.

  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 to be 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. 6 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 uses an arbitrary type 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.

  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 it is determined in S601 that the 1D-LUT 218 of all the image processing methods has been updated, the color mixture calibration is executed, but before the color mixture calibration, the usage situation analysis is performed for each image output method in S602. Do. Usage analysis S602 will be described in detail with reference to FIG.

(Obtain usage rate)
FIG. 7 is a flow of data collection for performing user usage analysis S602. 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 S701, whether there is 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 S701 that there is no switching of the image processing method in the page, the process proceeds to S704. In step S704, 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 S701 that the image processing method is switched in the page, the process proceeds to S702.

  In step S702, usage rates (in-page usage rates) of various image processing methods in the page are 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 S702 is equal to or greater than the threshold value in any image processing method, the process proceeds to S703. In step S703, all image processing methods used are counted. On the other hand, if only the in-page usage rate of the specific image processing method is equal to or higher than the formula among the in-page usage rates of the image processing methods acquired in S702, the process proceeds to S704. In step S704, 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. 6, in step S602, the usage rate of the image processing technique used in the data collection period is determined from the data collected in the flow of FIG.

  This usage rate is defined as the number of times that various image processing techniques are used (the number of counts) compared to the number of times when all types of usable image processing techniques are used (image count) when image formation is performed in a certain period of time ( The usage rate can be obtained by calculating the count). In addition, the counting period (data collecting period) may be from the time of the previous color mixture calibration execution to the time when the user's usage situation is analyzed in S602, for example, every period predetermined as one month or the like. 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 the description of the present embodiment, as illustrated in FIG. 7, the method of determining whether or not there is a switching of the image processing method when printing one page and counting the image processing method has been described. If there is another effective method that can extract the frequency of using, 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.

(Reconstruction of chart image)
When the acquisition of the usage rate of the image processing method is completed in S602, the process proceeds to S603, and the chart image used for the color mixture calibration is reconstructed.

  The determination method of the image processing method of the chart image used for the color mixture calibration is performed as follows. That is, according to the usage rate of each image processing method, the patch images constituting the chart image used for the color mixture calibration are rearranged to reconstruct the chart image. First, from the usage rate acquired in S602, the ratio of the number of times of use of various image processing techniques is acquired. In S603, the color mixture chart image is reconstructed based on the usage rate of the image processing method performed in S602. By reconstructing, a chart image output by a plurality of image processing techniques is realized with a smaller number of sheets than before reconstruction. A specific example will be described with reference to FIG. In this case, the printer 115 can use three types of image processing methods of image formation A, image formation B, and image formation C. Further, consider a case where there is one chart image used for color mixture calibration executed for each image processing method before reconstruction, and the number of patches formed on the chart image is 200 patches. Therefore, since three types of image processing methods can be used, a total of three charts are printed for color mixture calibration before the chart image is reconstructed. Here, a case will be described in which when a chart image is reconstructed, the goal is to reduce the number of chart images used for color mixture calibration to two. The number of chart images after reduction is not limited to two as long as the number of chart images can be reduced as compared with that before reconstruction. As a first example, the ratio of the number of times of use of image formation A, image formation B, and image formation C acquired in S602 is image formation A: image formation B: image formation C = 6: 1: 3. Will be described. In this case, since the frequency of use of the image forming B is low, a chart image used at the time of executing the color mixture calibration is not output using this image processing method. Therefore, the chart image formed by this image processing method is omitted from the chart image used when executing the color mixture calibration. In this way, the number of chart images used for the color mixture calibration can be set to two without reconfiguring the arrangement of patch images. As a second example, the ratio of the number of times of use of image formation A, image formation B, and image formation C acquired in S602 is acquired as image formation A: image formation B: image formation C = 3: 3: 4. The case will be described. In this case, it can be said that any image processing method is frequently used. Therefore, the number of patches printed when using the most frequently used image processing method C is given priority to 200 patches, and the number of patches printed when using the image processing methods A and B is set to 100 patches each. cut back. In this way, the patch image to be arranged on the chart image printed for the color mixture calibration is reconstructed. As a result, the charts used at the time of executing the color mixture calibration can be stored in two sheets. When reconfiguring the number of patches, the number of patches printed per sheet may be reduced to 100 patches by evenly thinning out from 200 patches. Alternatively, patch data in the case where the number of patches printed per chart image is 100 patches may be stored in advance in the storage device 121 and read out. When the chart image is reconstructed, it is necessary that the minimum number of patches necessary for maintaining the calibration accuracy is not reduced. For example, when 200 patches are formed and the calibration accuracy is kept good, the minimum number of patches necessary to maintain the calibration accuracy is about 80 to 100 patches.

  With this technique, an image processing technique that is used frequently, that is, has a high priority, performs correction using a chart image on which a relatively large number of patch images are printed. On the other hand, an image processing method with low usage frequency, that is, low priority, can be corrected using a chart image reconstructed by reducing the number of patches. As a result, an increase in paper and toner consumption is suppressed, and efficient correction can be performed without increasing the time and effort for the user.

  The details of the color mixture calibration in S604 when this method is used are as shown in FIG. 4, but when the chart image used for the color mixture calibration is output in S403, the color mixture chart image reconstructed in S603 is displayed. use.

  In this embodiment, the 4D-LUT 217 is created by one or more types of image processing techniques. However, depending on the acquisition result in S602, there is an image processing technique in which no patch image is configured and the 4D-LUT 217 is not created. In some cases. Accordingly, when correcting an output using an image processing method that was not used when the 4D-LUT 217 was created, the 4D-LUT 217 created using another image processing method is used instead. At this time, the 4D-LUT 217 of the image processing method corrected with the largest number of patches may be substituted, or the 4D-LUT 217 may be substituted although the features of the image processing method are similar.

  As described above, in the present embodiment, a chart image used at the time of executing the color mixture calibration is reconstructed based on the result of analyzing the usage situation of the user. Thus, even in an electrophotographic apparatus shared by users having different usage situations, it is possible to correct the color mixing reproduction characteristics most suitable for the characteristics of an image frequently seen by a plurality of users.

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.

(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 (17)

An image forming means for forming a color image using a recording agent of a plurality of colors;
Image processing means for realizing a plurality of image processing methods expressing a plurality of types of pseudo gradations;
Colorimetric means for measuring the color image formed by the image forming means;
The image forming unit measures a pattern image including a plurality of mixed-color patch images formed using a plurality of color recording agents by the color measuring unit, and forms the image forming unit using the result of the color measurement. Control means for controlling the execution of the color mixture calibration for correcting the reproduction characteristics of the color mixture to be performed;
An obtaining unit for obtaining a usage rate of the image processing method used when an image is formed by the image forming unit among the image processing methods generated by the image processing unit;
The number of patch images constituting the mixed color pattern image formed by using the image processing method determined to be low in the usage rate acquired by the acquisition unit is determined to be high in the usage rate acquired by the acquisition unit. And a configuration unit that configures the pattern image so that the number of patches is less than the number of patches that configure the mixed-color pattern image formed by using the image processing method performed,
The color image processing apparatus, wherein the control unit performs the color mixture calibration using a result of measuring a pattern image formed by the configuration unit.   2. The apparatus according to claim 1, wherein the configuration unit determines the number of patches constituting the mixed-color image formed by the image forming unit in accordance with the usage rate of the acquired image processing method. Color image processing device.   The color image processing according to claim 1, wherein the configuration unit determines not to print a mixed color image formed by the image forming unit according to a usage rate of the acquired image processing method. apparatus.   The acquisition of the usage rate by the acquisition unit uses a result obtained by counting the number of times each image processing method is used when an image is formed by the image forming unit in a predetermined period. Item 2. A color image processing apparatus according to Item 1.   2. The usage rate acquisition by the acquisition unit uses a result obtained by counting the number of times one type of image processing method is used when an image of one page is formed by the image forming unit. A color image processing apparatus according to 1. The acquisition of the usage rate by the acquisition unit is performed when there are a plurality of image processing methods used when an image of one page is formed by the image forming unit.
The color image processing apparatus according to claim 1, wherein a result obtained by counting the number of times of using the plurality of image processing methods is used. The acquisition of the usage rate by the acquisition unit is performed when there are a plurality of image processing methods used when an image of one page is formed by the image forming unit.
2. The method according to claim 1, wherein a result obtained by counting the number of times of using only an image processing method in which an in-page usage rate indicating a usage rate used when the image of one page is formed is equal to or greater than a threshold value is used. The color image processing apparatus described. In addition to executing the color mixture calibration, the control means
The image forming unit measures a pattern image including a plurality of single color patch images formed using a single color recording agent by the color measuring unit, and the image forming unit forms using the color measurement result. It also controls the execution of single color calibration that corrects the reproduction characteristics of single color,
The color image processing apparatus according to claim 1, wherein a pattern image is formed by using each of the plurality of types of image processing methods when performing the single color calibration. An image forming step of forming a color image using a recording agent of a plurality of colors;
An image processing step for realizing a plurality of image processing methods for expressing a plurality of types of pseudo gradations;
A colorimetric step for measuring the color image formed by the image forming step;
In the image forming step, a color image of a pattern image including a plurality of mixed color patch images formed using a plurality of colors of the recording agent is measured in the color measuring step, and the image forming step is performed using the result of the color measurement. A control step for controlling the execution of the color mixture calibration for correcting the reproduction characteristics of the color mixture to be formed,
An acquisition step of acquiring a usage rate of the image processing technique used when an image is formed in the image forming step;
The number of patch images constituting the mixed color pattern image formed by using the image processing method determined to be low in the usage rate acquired in the acquisition step is high in the usage rate acquired in the acquisition step. A configuration step of configuring the pattern image so as to be less than the number of patches that configure the mixed-color pattern image formed using the image processing method determined as
The method of controlling a color image processing apparatus, wherein the control step executes the color mixture calibration using a result of measuring the pattern image formed in the configuration step.   10. The composition step according to claim 9, wherein the number of patches constituting the mixed color image formed by the image forming step is determined in accordance with a usage rate of the acquired image processing method. A control method of a color image processing apparatus.   The color image processing according to claim 9, wherein the configuration step determines not to print a mixed-color image formed by the image forming step in accordance with a usage rate of the acquired image processing method. Control method of the device.   The acquisition of the usage rate in the acquisition step uses a result obtained by counting the number of times each image processing method is used when forming an image in the image forming step in a predetermined period. A method for controlling a color image processing apparatus according to claim 9.   The usage rate acquisition in the acquisition step uses a result obtained by counting the number of times one type of image processing method is used when an image of one page is formed in the image forming step. Item 10. A method for controlling a color image processing apparatus according to Item 9. The acquisition of the usage rate in the acquisition step is performed when there are a plurality of image processing techniques used when an image of one page is formed in the image formation step.
The color image processing apparatus control method according to claim 9, wherein a result obtained by counting the number of times the plurality of image processing methods are used is used. The acquisition of the usage rate in the acquisition step is performed when there are a plurality of image processing techniques used when an image of one page is formed in the image formation step.
10. The method according to claim 9, wherein a result obtained by counting the number of times of using only an image processing method in which an in-page usage rate indicating a usage rate used when the image of one page is formed is equal to or greater than a threshold value is used. A control method of the color image processing apparatus described. In the control step, in addition to executing the mixed color calibration,
In the image forming step, a color image of a pattern image including a plurality of single color patch images formed using a single color recording agent is measured in the color measuring step, and the color forming result is used in the image forming step. Also controls the execution of single color calibration to correct the reproduction characteristics of the single color to be formed,
The method for controlling a color image processing apparatus according to claim 9, wherein when performing the monochromatic calibration, a pattern image is formed using each of the plurality of types of image processing techniques. On the computer,
An image forming step of forming a color image using a recording agent of a plurality of colors;
An image processing step for realizing a plurality of image processing methods for expressing a plurality of types of pseudo gradations;
A colorimetric step for measuring the color image formed by the image forming step;
In the image forming step, a pattern image including a plurality of mixed-color patch images formed using a plurality of color recording agents is measured in the color measuring step, and the image forming step is formed using the result of the color measurement. A control step for controlling the execution of the color mixture calibration for correcting the reproduction characteristics of the color mixture to be performed;
An acquisition step of acquiring a usage rate of the image processing technique used when an image is formed by the image forming step;
The number of patch images constituting the mixed-color pattern image formed using the image processing method determined to be low in the usage rate acquired in the acquisition step is determined to be high in the usage rate acquired in the acquisition step. A configuration step of configuring the pattern image so as to be less than the number of patches that configure the mixed-color pattern image formed using the image processing method performed,
The control step is a program for executing the color mixture calibration using a result of measuring the pattern image formed in the configuration step.

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