JP2013055427A - Image processing device, image processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing device which, even when a chart configuration changes depending on output device characteristics, can generate patch data which does not require building patch data detection rules for each output device.SOLUTION: In an image processing device, chart data for charts output by an output device are created. The image processing device includes: reproduction information acquisition means of acquiring color reproduction range information indicating a range of colors reproducible by the output device; candidate creation means of extracting colors in a device-independent color space from among the colors included in the range indicated by the color reproduction range information and then making them patch candidate data; acquisition means of acquiring patch data from among the patch candidate data created by the candidate creation means according to the number of patches included in previously specified chart data; chart generation means of generating chart data by using the patch data acquired by the acquisition means; and conversion means of converting the chart data generated by the generation means into data in a device-dependent color space.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program for creating chart data for correcting the color of a printer.

  In recent years, the performance of electrophotographic apparatuses has improved, and machines that have achieved image quality equivalent to that of printing machines have appeared. However, due to durability of the output device, changes with time, etc., the color tone peculiar to electrophotography becomes unstable, and the problem is that the amount of color variation is larger than that of a printing press. Therefore, a conventional electrophotographic apparatus creates a one-dimensional gradation correction LUT (Look Up Table) corresponding to each toner of cyan, magenta, yellow, and black (hereinafter referred to as C, M, Y, and K). It has a single color calibration 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. However, even if the gradation characteristics of a single color are combined using a one-dimensional LUT, “mixed color” using a plurality of toners such as red, green, blue (hereinafter, indicated by R, G, B), and gray using CMY. However, since a non-linear difference occurs depending on the printer, it is difficult to guarantee the color.

  To solve this problem, output a chart created with mixed colors within the reproducible range of the printer, measure it with a scanner or colorimeter, compare it with the target value, and calculate the difference between the target value and the measured value as device-independent color Calculation is performed in the space (L * a * b *), and a correction amount is calculated based on the difference. Then, there is a technique of correcting a mixed color by updating a three-dimensional LUT that converts a device-independent color space (L * a * b *) into a device-dependent color space (CMYK) based on the correction amount. .

  For example, a technique for correcting a color difference between mixed colors by paying attention to a destination profile of an ICC profile and correcting it has been proposed (for example, Patent Document 1). In general, when a profile is re-created, it takes an enormous amount of time to output and measure many patches. In order to solve this problem, Japanese Patent Application Laid-Open No. H10-228667 outputs a patch that is evenly distributed on the device-independent color space (L * a * b *) according to the characteristics of the output device, and measures the color. The profile is recreated with a small number of patch data, and the correction of the color mixture is realized. Here, the ICC profile is data used at the time of color conversion defined by the ICC (International Color Consortium), and the destination profile is generally composed of an LUT. L * a * b * is one of device-independent color spaces defined by the CIE (International Lighting Commission), L * represents luminance, and a * b * represents hue and saturation. . Further, not limited to Patent Document 1, it is possible to correct a mixed color by outputting C ′, M ′, Y ′, and K ′ using a four-dimensional LUT with CMYK as an input.

  On the other hand, in order to perform calibration with high accuracy, it is necessary to measure the calibration chart output by the target device with high accuracy. When reading a chart using a scanner or other chart reading device, the reading value may not be obtained accurately due to the scattered light from surrounding patches, so that it is not affected by these disturbances. Accurate detection accuracy of the size and position of the chart patch is important. Here, the patch is expressed as rectangular data having a certain size per piece of data on a sheet as shown in FIG. In order to accurately detect the size and position of the patch, there is a problem that the inclination when the chart is placed on the scanner platen must also be considered.

  In Patent Document 2, a determination rule for determining that the orientation of the chart is correctly placed is created based on the patch data of the chart, and the orientation of the read chart is determined using the created determination rule. To do. Accordingly, a technique for determining the direction of a chart without including patch data dedicated to direction detection in the chart is disclosed.

Japanese Patent No. 4393294 JP 2009-060221 A

  However, in Patent Document 1, correction patch data composed of mixed colors in consideration of the mixed color characteristics of the output device is generated. At this time, since the color reproduction range and color reproducibility differ depending on the output device, the number of patches and patch data change. Therefore, since it is difficult to make the rules for determining the direction of the chart and detecting the inclination common rules that do not depend on the device, it is necessary to reconstruct the system for reading the patch according to the characteristics of the output engine.

  In Patent Document 2, a rule for determining the direction can be created from the generated patch data, but a determination rule must be created for each generated patch. Therefore, a system for reading patches must be reconstructed according to the characteristics of the output engine as in Patent Document 1.

  In order to solve the above problems, the present invention has the following configuration. That is, an image processing apparatus that generates chart data of a chart that is output by an output device, the reproduction information acquiring unit that acquires color reproduction range information indicating a color range that can be reproduced by the output device, and the color reproduction From the colors included in the range indicated by the range information, the color in the device-independent color space is extracted and used as patch candidate data, and candidate creation means and the patch included in the pre-specified chart data According to the number, from the patch candidate data created by the candidate creation means, an acquisition means for acquiring patch data, and a chart generation means for generating chart data using the patch data acquired by the acquisition means And conversion means for converting the chart data generated by the generation means into data in a device-dependent color space.

  According to the present invention, it is possible to measure a patch with high accuracy without being influenced by an algorithm for determining the direction of a chart or detecting a tilt even in a patch arrangement that takes into account the color mixing characteristics of an output device. It becomes possible.

The figure which shows the example of the whole structure of an image processing system. The figure which shows the flow of an image process. The figure which shows the flow of the calibration process of a mixed color. The figure which shows the three-dimensional LUT correction process in the calibration process of mixed colors. The figure which shows the four-dimensional LUT correction process in the calibration process of mixed colors. The figure which shows the flow of the process which produces a chart. The figure which shows the flow of the process which produces patch data. The figure which shows the flow of the process which adds patch data to the chart which concerns on 1st embodiment. The figure which shows the flow of the process which arranges the patch in a chart. The figure which shows the example of the chart used for the calibration of mixed colors. The figure which represents the patch data which exists on L * a * b * color space two-dimensionally. The figure of the example which showed the rule for patch detection. The figure which shows the flow of the process which acquires the measured value of patch data. The figure explaining the edge detection method of a patch. The figure which shows the flow of the process which adds patch data to the chart which concerns on 2nd embodiment. The figure which shows the flow of the process which adds patch data to the chart which concerns on 3rd embodiment. The figure showing the grid point data which exist in L * a * b * color space, a reference value, and a colorimetric value. The figure explaining the patch data addition method which concerns on 1st embodiment. The figure explaining the example of a display of UI which inputs the specific color information which concerns on 3rd embodiment.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

<First embodiment>
[System configuration]
A first embodiment according to the present invention will be described. In the present embodiment, a chart that takes into account the color mixing characteristics of the output device is generated, and the colorimetric values of the chart printed by the output device are acquired using chart direction determination and tilt detection rules. A method of correcting the color mixture color of the output device using the colorimetric values will be described. The color mixture correction method according to this embodiment will be described using a color mixture correction method using a four-dimensional LUT.

  FIG. 1 is a configuration diagram of a system according to the present embodiment. A multifunction peripheral (MFP) 101 that uses C, M, Y, and K toners is connected via a network 123. The PC 124 is connected to the MFP 101 via the network 123. A driver 125 in the PC 124 is a device driver for transmitting print data to the MFP 101.

  The MFP 101 will be described in detail. The network I / F 122 receives print data and transmits raster images and control data described later. The controller 102 includes a CPU 103, a renderer 112, an image processing unit 114, and the like. The interpreter 104 processed using the CPU 103 interprets a page description language (PDL) portion of the received print data, and generates intermediate language data 105 converted into a language that the renderer 112 can interpret. The CMS 106 performs color conversion using the source profile 107 and the destination profile 108 to generate intermediate language data (after CMS) 111. Here, a color management system (CMS) performs color conversion using information of a profile described later.

  The source profile 107 is a profile for converting a device-dependent color space such as RGB or CMYK into a device-independent color space such as L * a * b * or XYZ. XYZ is one of the device-independent color spaces defined by the CIE (International Commission on Illumination) like L * a * b *, where L * is luminance, a * b * is hue and saturation. Represents. XYZ is a device-independent color space defined by the CIE (International Commission on Illumination), like L * a * b *, and expresses colors with three types of stimulus values. The destination profile 108 is a color profile for converting a device-independent color space into a CMYK color space depending on the output 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). In this embodiment, the user can select the CMS 106 and the CMS 109.

  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. A printer 115 connected to the controller 102 is a printer that forms output data on paper using colored toners such as cyan, magenta, yellow, and black. The printer 115 includes a paper feed unit 116 that feeds paper and a paper discharge unit 117 that discharges paper on which output data is formed.

  The display device 118 displays a user interface (UI) indicating an instruction to the user and the state of the MFP 101. 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 image sensor such as a CCD (Charge Coupled Device) sensor with a lens (not shown). A raster-like image reading signal is obtained as image data in the RGB color space from the solid-state imaging device. The input device 120 is an interface for receiving input from the user, and includes, for example, a keyboard. The storage device 121 stores data processed by the controller 102, data received by the controller 102, and the like.

  The colorimeter 126 is a machine that can read a chart and acquire a value of a color space that does not depend on a device such as L * a * b * or XYZ, and can transmit the measured color data to the PC 124 or the MFP 101.

[Processing flow]
Next, the processing flow of the image processing unit 114 will be described with reference to FIG. In FIG. 2, S (step) is given to the processing step with a reference number. In S201, the image processing unit 114 receives image data. In step S <b> 202, the image processing unit 114 determines whether the received data is the scan data received from the scanner 119 or the raster image 113 sent from the driver 125. These have a flag for determining the type of job in the controller 102, and the determination is made based on the flag. Here, if the job is a PDL job via the driver 125, it is a raster image 113, and a CMYK image 211 converted into CMYK depending on the printer device by the CMS.

  In the case of scan data (YES in S202), since the received image data is an RGB image 203, the image processing unit 114 performs color conversion processing in 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 L * a * b * by calculation. On the other hand, the image processing unit 114 performs character determination processing on the RGB image 203 that is the received image data in S <b> 206 to generate character determination data 207. Here, the character determination data 207 is generated by detecting an edge or the like of the image.

  After the generation of the common RGB image 205 and the character determination data 207, the image processing unit 114 performs filter processing on the common RGB image 205 generated in S204 in S208. Here, using the character determination data 207 generated in S206, different filter processing is performed for the character portion and other portions. Next, the image processing unit 114 performs background removal processing in S209 and color conversion processing in S210 to generate a CMYK image 211 with the background removed. When the image data received in S201 is a raster image (NO in S202), the received image is handled as the CMYK image 211.

  In step S212, the image processing unit 114 performs processing for correcting CMYK color mixture data (CMYK image 211) using a four-dimensional LUT (4D-LUT). A method of generating a four-dimensional LUT that corrects the color mixture will be described later. Then, after correcting the color mixture, the image processing unit 114 corrects the tone characteristics of each single color of cyan, magenta, yellow, and black using a one-dimensional LUT in S213. The method for creating the one-dimensional LUT is a process for creating a correction value so that the target value can be reproduced by comparing the target value and the measured value of each color, and detailed description thereof is omitted. In step S214, the image processing unit 114 performs image forming processing such as halftone processing to create a CMYK image (binary) 215. Thereafter, in S <b> 216, the image processing unit 114 transmits the image data to the printer 115.

<4D LUT generation procedure>
Next, the flow of processing for generating a four-dimensional LUT for correcting the color mixture of colors used in the 4D-LUT correction processing in S212 of FIG. 2 will be described with reference to FIGS. The following processing is performed according to an instruction from the CPU 103 of the controller 102, and data is stored using a nonvolatile memory not described in the storage device 121 or the controller 102. In each figure, an arrow indicated by a solid line indicates a flow of processing, and an arrow indicated by a broken line indicates a data flow such as reference and output of data used in the processing.

  FIG. 3 shows the flow of processing for creating a four-dimensional LUT. First, in step S <b> 301, the controller 102 reads the chart data A <b> 302, performs processing in the image processing unit 114, transmits it to the printer 115, and outputs the chart 303. The chart data A302 is a chart for correcting a four-dimensional LUT composed of a plurality of patches as shown in FIG. A method for generating the patch data of the chart data A302 will be described later.

  In step S <b> 304, the controller 102 acquires the image data of the chart 303 using the scanner 119 and measures the signal value of each patch from the image data, thereby obtaining the colorimetric value (L * a * b *) 305. obtain. The means for acquiring the colorimetric values from the image data of the chart in S304 will be described later with reference to FIG. Here, the reference value (L * a * b *) 307 is an L * a * b * value for correcting the color mixing characteristics of the output device to a target state, and is determined for each of chromatic and achromatic colors. It has been. In FIG. 17, which will be described later, a reference value and a colorimetric value in the L * a * b * color space are shown, and the difference between the reference value and the colorimetric value is used to correct the four-dimensional LUT.

  Next, the controller 102 reads the colorimetric value (L * a * b *) 305, the reference value (L * a * b *) 307, and the L * a * b * → CMY 3D-LUT 308 in S306. A dimension LUT correction process is performed. The controller 102 outputs L * a * b * → CMY 3D-LUT (after correction) 309, which is the result of the three-dimensional LUT correction processing. The three-dimensional LUT correction process in S306 will be described later. L * a * b * → CMY is a color conversion LUT for converting from L * a * b * to CMY, and what is denoted by “→” is an LUT for converting the color space. Is shown. The L * a * b * → CMY 3D-LUT 308 is an LUT created by using a known method, and L * a * b * values (FIG. 17) determined at regular intervals in a lattice shape as shown in FIG. Device-specific CMY values corresponding to (lattice point data). Interpolation is performed on an arbitrary L * a * b * value, and a CMY value is output.

  Finally, the controller 102 uses the CMY → L * a * b * 3D-LUT 311, L * a * b * → CMY 3D-LUT (after correction) 309, and device information 312 and device information 312 in S 310. A 4D-LUT 414 of C′M′Y′K ′ is created. The process of creating a four-dimensional LUT in S310 will be described later with reference to FIG. A 3D-LUT 311 of CMY → L * a * b * is a color conversion LUT created by using a known method, and an L * a * b * value corresponding to a CMY value determined at regular intervals in a lattice shape. Is the data describing. The controller 102 performs an interpolation operation on an arbitrary CMY value and outputs an L * a * b * value. In addition, the fixed space | interval of a lattice point shall be defined previously.

(3D LUT correction processing)
Next, details of the three-dimensional LUT correction processing shown in S306 of FIG. 3 will be described with reference to FIG. In FIG. 4, S (step) is given to the processing step with a reference number. First, in S401, the controller 102 uses the colorimetric value (L * a * b *) 305 and the reference value (L * a * b *) 307 from the storage device 121 to store chromatic color data and achromatic color data. Difference data 402 is calculated for each. The difference data 402 is calculated for the number of data of the chart data A302, and is classified into chromatic colors and achromatic colors.

  Next, in step S403, the controller 102 reads the L * a * b * → CMY 3D-LUT 308 from the storage device 121, extracts one of the grid point data (L * a * b *), and determines whether the color is chromatic or not. Determine if it is colored. An example of the determination method used in this embodiment will be described. Since the values of a * and b * are data indicating hue / saturation, a value in which both data are close to “0” is determined as an achromatic color. In this case, for example, a method of determining a threshold value for determination may be considered, but the determination method here is not particularly limited. This determined data is lattice point data (L * a * b * and chromatic / achromatic information) 404. Here, the data of L * a * b * is L * when L * is 0 to 100, a * and b * are each in the range of −128 to 128, and the number of grid points is 33 × 33 × 33. Is approximately 3 and a * and b * are equally increased by 8. That is, the lattice point data extracted here is (L *, a *, b *) = (0, −128, −128) to (L *, a *, b *) = (100, 128, 128). This is one of 33 × 33 × 33 = 35937 data configured in the range. Furthermore, it is assumed that information indicating whether the data is a chromatic color or an achromatic color is added to this data.

  In step S <b> 405, the controller 102 calculates the distance between the lattice point data (L * a * b * and chromatic / achromatic information) 404 and the reference value (L * a * b *) 307. In step S <b> 406, the controller 102 extracts difference data whose distance is within a certain threshold, and determines the correction amount of the grid point data (L * a * b * and chromatic / achromatic information) 404 from the difference data. At that time, referring to the chromatic / achromatic information of the grid point data, extraction processing is performed using the chromatic color difference data for chromatic colors and the achromatic color difference data for achromatic colors.

  In step S <b> 407, the controller 102 reflects the lattice point correction amount in the lattice point data (L * a * b * and chromatic / achromatic information) 404 and the corrected lattice point data (L * a * b *) 408. Is stored in the storage unit. In step S409, the controller 102 determines whether all grid point data have been processed. If processing has not been performed for all grid point data (NO in S409), controller 102 extracts new grid point data in S403 and repeats the process.

  If all grid point data has been processed (YES in S409), controller 102 performs an interpolation calculation process in S410. When all the grid point data are processed, corrected grid point data (L * a * b *) 408 is created for the number of grid points. In S410, the controller 102 performs an interpolation operation using the L * a * b * → CMY 3D-LUT 308 in S410 to calculate a new CMY value. The controller 102 stores this CMY value as an output value for the original lattice point data in the storage unit, and creates a 3D-LUT (after correction) 309 of L * a * b * → CMY.

  As described above, by referring to the difference data within a certain distance from the lattice point and determining the correction amount of the lattice point, it becomes possible to determine the correction amount of a large amount of lattice point data with a small number of data. . Note that the present invention is not limited to this example, and any method may be used as long as it corrects the 3D-LUT 309 of L * a * b * → CMY.

(4D LUT creation process)
Next, the process of creating the four-dimensional LUT in S310 of FIG. 3 will be described with reference to FIG. In FIG. 5, S (step) is given to the processing step with a reference number. First, in step S <b> 501, the controller 102 extracts CMY values from the CMYK uniform data 502. Here, the number of CMYK equal data is the same as the number of grid points of the 4D-LUT 313 of CMYK → C′M′Y′K ′, and the data interval is also the same. For example, when the number of grid points of the 4D-LUT 313 of CMYK → C′M′Y′K ′ is 8 × 8 × 8 × 8 = 4096, the number of CMYK uniform data 502 is 4096. When data is expressed by 8 bits (0 to 255), the data interval is about 36.

  In step S <b> 503, the controller 102 performs an interpolation operation using the CMY → L * a * b * 3D-LUT 311 and the L * a * b * → CMY 3D-LUT (after correction) 411 to obtain a CMY value. To decide. First, the controller 102 performs an interpolation operation using the 3D-LUT 311 of CMY → L * a * b * from the extracted CMY values to obtain an L * a * b * value. Next, the controller 102 performs an interpolation calculation using the L * a * b * → CMY 3D-LUT (after correction) 411 from the previously calculated L * a * b * value to calculate a CMY value.

  Next, in S504, the controller 102 extracts the value of K from the CMYK uniform data 502, and creates the CMYK value 505 by combining the previously determined CMY values. The K value extracted here corresponds to the CMY value extracted in S501.

  In step S <b> 506, the controller 102 performs a loading amount limiting process using the device information 312. Here, the device information 312 represents the toner amount applicable to the printer 115 as a numerical value, and is defined as “loading amount” in this specification. For example, in the case of CMYK, assuming that the maximum value of a single color is 100%, a maximum signal value of 400% can be set for each color. However, when the total amount of applicable toner is limited to 300%, the upper limit of the applied amount is 300%.

  Depending on the combination, the CMYK value 505 may exceed the prescribed loading amount, and thus the loading amount limiting process is performed by performing a known undercolor removal (UCR) process or the like. The UCR process is a process for replacing CMY toner with K toner. In general, when expressing black, there are a method of expressing CMY using equal amounts and a method of expressing K alone. When expressed by K alone, the density is lower than when expressed by CMY, but there is an advantage that the loading amount can be reduced.

  In step S507, the controller 102 performs pure color processing to create a CMYK value (after correction) 508. When correction is performed with the 4D-LUT 313 of CMYK → C′M′Y′K ′, data input in a single color may be output in a mixed color of secondary colors or more as a result of performing an interpolation calculation. Actually, it is desirable that C single color data is output in C single color. In order to realize this, referring to the original CMYK uniform data 502, if it is pure color data, the CMYK value is corrected to pure color data. For example, when the CMYK uniform data 502 is C single color but the CMYK value (after correction) 508 includes an M value, the M value is set to “0”.

  In step S <b> 509, the controller 102 stores the CMYK value (after correction) 508 in the 4D-LUT 313 of CMYK → C′M′Y′K ′. Finally, in S510, the controller 102 determines whether all the CMYK uniform data 502 has been processed. If all data has not been processed (NO in S510), controller 102 extracts CMY values from remaining CMYK uniform data 502, and repeats the processing. When all the data has been processed (YES in S510), the controller 102 ends the process, and the 4D-LUT 313 of CMYK → C′M′Y′K ′ is completed.

  Here, the number of grid points of the LUT is not limited to the example of the present embodiment, and any number may be used. Further, the number of grid points may be a LUT having a special configuration, for example, the number of grid points of C and M is different in the CMYK → C′M′Y′K ′ 4D-LUT 414.

<Patch data generation procedure>
A flow for generating patch data of the chart data A used in the four-dimensional LUT creation processing will be described with reference to FIGS. The following processing is performed according to an instruction from the CPU 103 of the controller 102, and data is stored using a nonvolatile memory not described in the storage device 121 or the controller 102. In each figure, S (step) is given to a processing step with a reference number. In each figure, arrows indicated by solid lines indicate the flow of processing, and arrows indicated by broken lines indicate the flow of data such as reference and output of data used in the processing.

(Chart data generation process)
FIG. 6 shows the flow of creating the chart data A302. First, in step S <b> 601, the controller 102 reads chart data B <b> 602 that can determine the color reproduction range of the output device, performs processing by the image processing unit 114, transmits the chart data B <b> 602 to the printer 115, and outputs a chart 603. For example, the chart data B 602 is R, G, B, C, M, Y, K patch data of which the signal value is 100%, and the K patch data is C, M, Y respectively. This is data expressed with a signal value of 100%.

  In step S <b> 604, the user acquires color reproduction range data (L * a * b *) 605 that is a colorimetric value of the chart using the colorimeter 126, and transmits the colorimetric value to the controller 102. Here, not limited to the configuration of the present embodiment, any processing method may be used as long as there is a means for measuring patch data and converting the data into L * a * b * values. Further, the color reproduction range data is color reproduction range information indicating a color reproducible range on the color space in the output device. Thereby, a reproduction information acquisition means is realized.

  Next, in S606, the controller 102 performs patch data generation processing using the color reproduction range data (L * a * b *) 605 and the patch detection rule 607, and is selected so that it can be used for the detection rule. The pre-selection patch data 608 that is the state before the registration is created. The patch data creation processing in S606 will be described later with reference to FIG.

  The patch detection rule 607 used in the present embodiment is that the chart data A302 is output by an output device, and then a chart image is obtained using a scanner, and direction determination based on the chart configuration and patch center position detection are performed. Rules for use are defined. For example, in order to determine the direction of the chart, there is a rule that the patch in the first row and the first column in FIG. 10 is “achromatic and high density color”. The patch in the M-th row and the N-th column is “the color in which the absolute value of the difference between a * and b * is the largest in the L * a * b * color space” as indicated by 1102 in FIG. Rules are stored. In addition, in order to acquire the center position of the patch from the entire image, the threshold value for each patch data and the maximum number of patch data to be determined when using edge extraction are also stored.

  In step S <b> 609, the controller 102 performs data selection processing using the patch detection rule 607 and pre-selection patch data, and generates post-selection patch data 610 and chart information 611. The data selection process in S609 will be described later with reference to FIG. The chart information 611 used in the present embodiment stores information constituting the entire chart. For example, the number of patches in the chart data A302, the number of patches in the main scanning direction, and the size of each patch are stored. In addition, information on chromatic and achromatic colors of patches is also stored.

  Next, in S612, the controller 102 performs an interpolation operation using the selected patch data 610 and the L * a * b * → CMY 3D-LUT 308, and creates chart data A302. Then, this processing flow ends.

(Patch data creation process)
FIG. 7 shows the flow of patch data creation processing in S606. The outline of the patch data creation process is as follows. The color difference equal data (L * a * b *) 703 is calculated from (L *, a *, b *) = (0, −128, −128) to (L *, a *, b *) = (100, 128). , 128), P × P × P data is held. At this time, the color difference in the device-independent color space is configured to be uniform. The range of the variable P indicates the number of grid points from 1 to Pmax. The color difference equal data is not limited to those in which the color differences in the device-independent color space are strictly equal, and may be data corresponding to positions obtained by dividing the device-independent color space substantially equally. Needless to say. Then, data within the color reproduction range of the output device is extracted from the color difference uniform data (L * a * b *) 703, and the number of pieces of patch data within the color reproduction range is held by the number of grid points. Then, lattice point data having the largest number of patches within the range not exceeding the maximum number of patches that can be used in the chart is extracted and stored as pre-selection patch data 608. Then, when the pre-sorting patch data 608 is arranged on the chart, if the chart does not become rectangular, patch data is added from other patch candidate data so that it becomes rectangular.

  When a chart is created using the pre-selection patch data 608 generated in the patch data creation process of S606, the chart may not be rectangular. If the patch data does not become rectangular, the patch data that exceeds a certain color difference is searched from the patch candidate data 707 from each patch data of the pre-selection patch data 608 until it becomes rectangular, and the extracted patch data is used as the pre-selection patch. Append to data 608. Data that can be added is searched from all the patch candidate data 707. If the data does not have a rectangular shape, dummy patch data is added until it becomes a rectangular shape, and if it has a rectangular shape, patch data is not added. The above is the outline of the patch data creation processing in S606.

  First, in S701, the controller 102 sets the initial value of the variable P to “1”. Next, in S <b> 702, the controller 102 acquires one piece of grid point data when the grid point is P from the color difference equal data (L * a * b *) 703. Thereby, a data acquisition means is realized. Next, in S <b> 702, the controller 102 uses the color reproduction range data (L * a * b *) 605 to make a color reproduction area inside / outside determination of the grid point data acquired in S <b> 702.

  For example, as a color reproduction range inside / outside determination method, a method such as Japanese Patent No. 3563350 can be used. Here, in Japanese Patent No. 3563350, when the color reproduction range of the output device is defined by 8 points of R, G, B, C, M, Y, K, and W, 8 points are expressed as L * a * b * values. Convert to Then, the color reproduction range of the output device is approximated by a dodecahedron formed from six points of R, G, B, C, M, and Y and K and W. A point existing within the color reproduction range of the output device with respect to the formed dodecahedron is a method for determining that the color is within the color reproduction range. When the data of the chart data B (CMY) 602 is a patch expressing R, G, B, C, M, Y, K, and W, the color reproduction range data (L * a * b *) 605 is a dodecahedron. The device color reproduction range can be approximated. As a result, the grid point data can be determined whether the output device has a color reproduction range.

  If the result of the color reproduction range determination is outside the color reproduction range of the output device in S705 (NO in S705), the controller 102 determines whether all L * a * b * data has been processed in S709. I do. If the result of the color reproduction range determination is within the color reproduction range in S705 (YES in S705), the controller 102 stores the grid point data acquired in S702 in S706 in the patch candidate data 707. Thereby, candidate creation means is realized. In step S <b> 708, the controller 102 increases the number of patches within the color reproduction range by the number of P grid points by one.

  In step S709, the controller 102 determines whether all the grid point data in the color difference uniform data when the grid point is P have been processed. If all the grid point data has not been processed (NO in S709), the controller 102 acquires the next grid point data in S702 and repeats the process. If all the grid point data have been processed in S709 (YES in S709), the controller 102 determines whether or not the maximum grid point number (Pmax) generated in S710 has been exceeded.

  If Pmax is smaller than variable P (YES in S710), controller 102 increases variable P by one in S711. In step S702, the controller 102 acquires grid point data when the grid point is P, and repeats the process. If Pmax is greater than or equal to variable P (NO in S710), controller 102 performs the process of S712. Here, the maximum number of grid points Pmax may be specified by the user, but it is desirable that the maximum number of grid points is L * a * b * → CMY 3D-LUT 308.

  In step S <b> 712, the controller 102 reads the maximum number of patch data defined in the patch detection rule 607. Then, the controller 102 determines the number of grid points used as a patch within a range not exceeding the maximum number of read patch data.

  Next, in S713, the controller 102 extracts patch data of the number of grid points determined in S712 from the patch candidate data 707 and stores it in the pre-selection patch data 608. Next, in S714, the controller 102 arranges the pre-selection patch data 608 on the chart and determines whether the chart is rectangular. Here, the rectangular shape means that patch data is arranged on the chart and a patch exists in the Mth row and the Nth column in FIG.

  If the chart is rectangular (YES in S714), controller 102 ends the process. If the chart is not rectangular (NO in S714), the controller 102 adds patch data using the patch detection rule 607, the pre-selection patch data 608, and the patch candidate data 707 in S715. The patch data addition processing in S715 will be described later with reference to FIG.

  However, when there is no data in a patch that is not used for detection or the like in the patch detection rule 607 when arranged on the chart, it is not necessary to have a rectangular shape. In this case, the controller 102 ends the process. For example, even if rule 1 for M row and N column is not required, the patch for M row and N column can be any patch data as long as there is a method for determining the direction of the chart and tilting, so it is not necessarily rectangular. There is no need.

(Additional processing of patch data)
FIG. 8 shows the flow of the patch data addition process in S715 of FIG. The outline of the patch data addition process is as follows. When a chart is created using the pre-selection patch data 608 generated in the patch data creation process of S606, the chart may not be rectangular. If it is not rectangular, patch data exceeding a certain color difference is extracted from the patch candidate data 707 from each patch data of the pre-selection patch data 608 until it becomes rectangular.

  Patch candidate data for which pre-selection patch data is not found within the color difference, such as patch candidate data 1801 in FIG. 18, is added to pre-selection patch data 608. Patch candidate data for which pre-selection patch data is found within the color difference, such as patch candidate data 1802 in FIG. 18, is not added to the pre-selection patch data 608. If patches that meet the conditions are added one by one from the patch candidate data 707, and if all the patch candidate data 707 are not rectangular before searching, all the patch candidate data 707 is processed into an error. If it is rectangular, the process ends normally and a chart is created using the pre-selection patch data 608.

  First, in step S <b> 801, the controller 102 acquires one piece of patch data of the patch candidate data 707. In this embodiment, the patch candidate data 707 to be acquired is randomly acquired in order to eliminate the bias in the color of the patch data to be added. The acquisition method is not limited to this. In step S <b> 802, the controller 102 acquires one pre-selection patch data of the pre-selection patch data 608.

  In step S802, the controller 102 calculates a color difference between the candidate patch data acquired in step S801 and the pre-selection patch data acquired in step S802. In step S804, it is determined whether the color difference calculated in step S803 exceeds a threshold value. The threshold value is for avoiding bias in the correction accuracy between the lattice points, and the lattice point interval in the case of the maximum number of lattice points Pmax may be used as the threshold value.

  If the color difference does not exceed the threshold value in S804 (NO in S804), in S806, the controller 102 determines whether all pre-sorting data has been processed. If the color difference exceeds the threshold value in S804 (YES in S804), the controller 102 stores the patch candidate data in the pre-selection patch data 608 in S805. In step S <b> 807, the controller 102 determines whether the chart is rectangular using the patch detection rule 607. This determination method is the same as S714.

  If the chart is rectangular in S807 (YES in S807), the process ends. If the chart is not rectangular in S807 (NO in S807), the controller 102 determines in S808 whether all patch candidate data has been processed.

  If all the pre-sorting data has not been processed in S806 (NO in S806), the controller 102 acquires the pre-sorting patch data 608 in S802 and repeats until all the pre-sorting patch data is processed. If all pre-sorting data has been processed (YES in S806), the controller 102 determines whether all patch candidate data has been processed in S808.

  If all the patch candidate data is not processed in S808 (NO in S808), the controller 102 reads the patch candidate data in S801 and repeats until all the patch candidate data is processed. If all the patch candidate data has been processed (YES in S808), the chart cannot be detected because the chart has not become rectangular. Therefore, the controller 102 stores dummy data in the pre-selection patch data 608 as patch data that is insufficient until it becomes rectangular in S809, and ends the process. For example, as the dummy data data, the white L * a * b * value (L *, a *, b *) = (100, 0, 0) may be used.

(Data selection process)
FIG. 9 explains the data selection processing in S609 of FIG. The outline of the data selection process is as follows. It is selected whether each patch of the pre-selection patch data 608 can be used for patch detection, and the data is temporarily stored for each rule. Then, the patch data sorted according to the rule based on the detection rule is rearranged to create post-sort patch data 610 that enables patch detection from the chart.

  First, in step S <b> 901, the controller 102 acquires one piece of patch data of the pre-selection patch data 608. In step S <b> 902, the controller 102 reads the detection rule of the patch detection rule 607.

  Here, the detection rules in the example of this embodiment are “achromatic color”, “rule 1”, and “rule 2”, and will be described with reference to FIGS. 11 and 12, respectively. FIG. 11 shows an example when the pre-selection patch data 608 and the lattice point data of L * a * b * → CMY 3D-LUT 308 are projected in two dimensions on the a * -b * plane. In FIG. 11, L * a * b * grid points of the pre-selection patch data 608 (marked with ▲ in FIG. 11), L * a * b * → L * a * b * grid points of the CMY 3D-LUT 308 (in FIG. 11). ) And the color reproduction range of the output device (solid line in FIG. 11).

  The achromatic color is a color that is determined as an achromatic color in S403, and means patch data such as the patch data 1101 in FIG. In rule 1, patch data such as patch data 1102 and 1103 in FIG. 11 is used, and when the absolute value of the difference between a * and b * is calculated, the data having the largest absolute value is used in rule 1. Use as possible data. Rule 2 is patch data not shown in FIG. 11, and data whose L * value is more than a predetermined value compared with L * of the background of the medium is usable as data in Rule 2. Use. Here, the threshold is a value used when detecting an edge of the chart.

  FIG. 12 shows an example when a chart to which the detection rule is applied is arranged. Patch data that has high density in achromatic color, that is, patch data in which L * is low in achromatic color is arranged in the first row and first column, which is the position of patch data 1201 in FIG. The patch data of rule 1 is arranged in the Mth row and Nth column, which is the position of the patch data 1202 in FIG. The patch data of rule 2 is arranged in the Mth row and the first column, which is the position of the patch data 1203 in FIG. 12, and the first row and the Nth column, which is the position of the patch data 1204.

  Of course, data corresponding to achromatic patch data may be arranged at other patch positions. The detection rule is not limited to the example shown in this embodiment, and when it is another rule, it goes without saying that if the patch position used for patch detection changes, the patch position used for patch detection changes accordingly. Yes. Further, in this embodiment, the patches are prioritized and applied in the order of achromatic color, rule 1, rule 2, and others (S903 to S909), but if the rule contents are changed, the priority is naturally given. The order will also be changed.

  In step S903, the controller 102 determines whether the patch data acquired in step S901 is an achromatic color. If it is determined that the color data is achromatic data in S903 (YES in S903), the controller 102 sets information that the patch data is achromatic data in S904. If it is determined in S903 that the data is not achromatic data (NO in S903), the controller 102 determines in S905 whether the patch data is patch data that can be used for rule 1.

  If it is determined in S905 that it can be used for rule 1 (YES in S905), the controller 102 sets information that the patch data is rule 1 data in S906. If it is determined in S905 that it cannot be used for rule 1 (NO in S905), it is determined in S907 whether the patch data is patch data that can be used for rule 2. If it is determined in S907 that the rule 2 can be used (YES in S907), the controller 102 sets information that the patch data is rule 2 data in S908. If it is determined in S907 that the rule 2 cannot be used (NO in S907), the controller 102 sets information that the patch data is other patch data in S909.

  Next, in S910, the controller 102 stores the patch data for each rule in the patch data 911 for each rule based on the set information. Next, in S912, the controller 102 determines whether all the pre-sorting patch data 608 has been processed. When all the processing has been performed (YES in S912), in S913, the controller 102 arranges the patch data based on the detection rules using the patch detection rules 607 and the rule-specific patch data 911, and selects the patch data 610 after selection. Create

  The patch data arrangement method is to preferentially arrange patch data corresponding to patch positions determined by each rule as shown in FIG. For example, in other patch arrangement methods, achromatic color patch data may be preferentially arranged for colors other than the Nth column of the first row so that the user can easily understand the orientation of the chart. Next, in S <b> 914, the controller 102 stores information regarding the patches arranged in S <b> 913 in the chart information 611. For example, the total number of patches arranged in S913, the number of patches in each of the main scanning direction and the sub scanning direction, and the chromatic / achromatic information of the patches are also stored. Thereby, a chart generating means is realized.

  According to the patch data generation method of the present embodiment, even when the characteristics of the output device change due to changes over time or the environment in use, it is possible to create an appropriate patch that matches the characteristics of the current output device. As a result, it is possible to create a four-dimensional LUT for correcting color mixing with an appropriate number of patches with high accuracy. For example, immediately after the patch data is created, the patch data is output using the output device, the colorimetric value of the patch output using the colorimeter 126 is acquired, and the data is obtained as the colorimetric value (L * a * b *) You may register as 305.

  Note that the rules are not limited to those shown in the present embodiment, and any rules may be used as long as patches can be detected. Since the number of rules only needs to be a number that enables patch detection, it goes without saying that if the number of rules changes, the number of branches determined for each rule changes accordingly.

<Patch data acquisition procedure>
A flow of processing for obtaining the colorimetric values of each patch from the image data of the chart 303 acquired by the scanner in S304 will be described with reference to FIG. The following processing is performed according to an instruction from the CPU 103 of the controller 102, and data is stored using a nonvolatile memory in the storage device 121 or the controller 102.

  First, in step S <b> 1301, the scanner 119 reads the chart 303 and obtains image data 1302 of the chart 303. Here, the chart 303 is obtained by printing the chart data A302 with an output device. In step S <b> 1303, the controller 102 performs an interpolation operation using the acquired image data 1302 and RGB → L * a * b * 3D-LUT 1304 to convert the image data 1302 to the L * a * b * color space. . An RGB → L * a * b * 3D-LUT 1304 is a color conversion LUT created by using a known method, and an L * a * b * value corresponding to an RGB value determined at regular intervals in a grid pattern. Is the data describing.

  In step S <b> 1305, the controller 102 detects the edge of the chart of the image data 1302 using the chart information 611 and the patch detection rule 607. The edge detection method of the chart in the main scanning direction will be described with reference to FIG. Here, the main scanning direction is the x direction in FIG. 14, and the sub scanning direction is the y direction in FIG. Step shown in FIG. 14 is a width for edge detection in the sub-scanning direction, and is an integer value of 1 or more.

  First, a difference in luminance L * between the target pixel and the previous pixel is calculated in the sub-scanning direction, and an edge is determined when the difference value exceeds a threshold value. However, since there is a possibility that there is dust attached to the glass surface of the scanner, if a certain number of pixels are detected in the sub-scanning direction and there is no edge in the sub-scanning direction again, the previous edge Is determined to be the edge of the chart. If no edge is detected in the sub-scanning direction, some pixels are moved in the main scanning direction, the same processing is performed to detect the edge, and the first edge portion found is defined as x1. Then, (N-1) patch pixels are moved from the chart information in the main scanning direction from x1, and x2 is detected by performing edge detection.

  When the edge is not detected, the search is performed again from x1. By performing the above processing, it is possible to detect the position of the upper side of the chart. Then, similar processing is performed in the sub-scanning direction to detect y1 and y2 on the left side of the chart. In the present embodiment, the patch data 1201, 1202, 1204 shown in FIG. 12 has a difference from the paper white in L *, so that the edge can be detected, but the same is true even if the rule for edge detection is different. Anything can be used as long as the effect is obtained.

  Next, in S1306, the controller 102 determines that the inclination of the chart is equal to or less than a threshold value. The determination method of the inclination is performed when dy, which is the absolute value of the difference between the y-coordinates of x1 and x2 detected in S1305, and dx, which is the absolute value of the difference between the x-coordinates of y1 and y2, are equal to or less than a threshold value. Judge that there is no. For example, as a method for determining the threshold, the values of dx and dy when tilted by 5 degrees may be calculated and used as the threshold. If it is determined in S1306 that the chart is tilted (NO in S1306), in S1308, the display device 118 displays the content that the chart is tilted and prompts the user to replace the chart again. Read the chart again.

  If it is determined in S1306 that the chart is not tilted (YES in S1306), the controller 102 calculates the tip of the chart in S1307. As a calculation method of the leading end of the chart, for example, it is assumed that the intersection of a straight line passing through x1 and x2 and a straight line passing through y1 and y2 is the leading end of the chart.

  In step S1309, the controller 102 calculates the center position of each patch using the patch size stored in the chart information 611, the leading end of the chart calculated in step S1307, and dx and dy calculated in step S1306. At this time, since the inclination per patch can be calculated from dx and dy, the center position of each patch in consideration of the inclination can be determined with high accuracy.

  Next, in S1310, the controller 102 acquires the signal value (pixel value) of each patch from the center position of each patch obtained in S1309. When obtaining the signal value, the signal value may be obtained by calculating the average value using the signal values of the peripheral pixels as well as the pixel at the center position.

  Next, in step S <b> 1311, the controller 102 performs direction determination using the signal value of each patch obtained in step S <b> 1310 and the patch detection rule 607. For example, as a direction determination method, there are the achromatic and high-density patch data 1201 in the first row and first column of FIG. 10 and the patch data 1202 of the rule 1 in FIG. In this case, there is a determination method using the difference in absolute value of the difference between a * and b * of the patch data.

  In addition, when the chart is created, the L * a * b * value of each patch data of the chart information 611 is held, and compared with the signal value of each patch obtained in S1310, You may use the method of determining with an error when a difference result is large. In that case, there is no need to set rule 1 and the chart need not be rectangular. Even if the patch rule is set as in the above example, the chart direction can be determined, and the same effect can be obtained.

  Next, in S1312, the controller 102 determines whether or not the orientation of the chart obtained in S1311 is set correctly. If the orientation of the chart is wrong (NO in S1312), in S1314, the display device 118 displays the content that the orientation of the chart is incorrect, prompts the user to reposition the chart, and rereads the chart again. . If the chart orientation is correct in S1312 (YES in S1312), in S1313, the controller 102 classifies the signal value obtained in S1310 into a chromatic color and an achromatic color, and the result is a colorimetric value (L * a * B *) 305 is stored in the storage unit and the process is terminated.

  Although the method for acquiring patch data in the present embodiment has been described, the present invention is not limited to this, and any method may be used as long as it can determine the orientation and inclination from a scanned image patch and acquire the value of patch data.

  According to the present invention, it is possible to generate a chart in consideration of the color mixing characteristics of the output device, and to create a four-dimensional LUT for correcting color mixing with high accuracy with an appropriate number of patches. Also, the patch data generation method of the present embodiment makes it possible to create an appropriate patch that matches the current output device characteristics even when the characteristics of the output device change due to changes over time or the environment in use.

  Further, even if the patch arrangement of the chart depends on the output device, the chart patch data can be measured with high accuracy since rules such as chart direction determination and inclination detection do not depend on the output device. In addition, by performing tilt detection using edge detection of the chart, the center position of each patch can be obtained accurately, and highly accurate patch data can be measured.

  Further, the chart direction determination is made by giving characteristics to the two patches, so that a determination with a small amount of calculation is possible.

<Second embodiment>
Next, an additional processing method of patch data in consideration of density unevenness of the chart in the output device will be described. In the first embodiment, it is configured to generate a chart in consideration of the color mixing characteristics of the output device and to create a four-dimensional LUT for correcting color mixing with a high number of patches with high accuracy.

  However, in the patch data addition process of FIG. 7, since patch data in which the color difference between patches is equal to or greater than a certain interval is added until the chart becomes rectangular, calculation time may be required. In addition, the toner transfer process and fixing process in the output device are easily affected by the temperature, humidity, or aging around the output device, and the amount of fixing toner on the paper may change, resulting in density unevenness. is there. In contrast, in the present embodiment, in addition to adding patch data in which the color difference between patches is equal to or greater than a certain interval in the patch data addition processing of the chart, a processing method that takes into account the density unevenness of the chart in the output device explain. Here, only the difference from the first embodiment is described, and the same processing as that of the first embodiment is performed for overlapping portions. In FIG. 4, S (step) is given to the processing step with a reference number. In each figure, arrows indicated by solid lines indicate the flow of processing, and arrows indicated by broken lines indicate the flow of data such as reference and output of data used in the processing.

(Additional processing of patch data)
FIG. 15 explains the flow of the patch data addition process of S715 of FIG. 7 in the first embodiment, and corresponds to FIG. 8 of the first embodiment. Rather than selecting patch data having a color difference equal to or greater than a certain interval from the other patch candidate data performed in FIG. 7, a dummy flag is added.

  In this embodiment, a dummy flag can be added for each patch to the pre-selection patch data 608 and the rule-specific patch data 911. Similarly, information regarding the dummy flag is described in the chart information 611. The following processing is performed according to an instruction from the CPU 103 of the controller 102, and data is stored using a nonvolatile memory in the storage device 121 or the controller 102.

  First, in S1501, the controller 102 determines whether the chart is rectangular like S714 in FIG. 7 using the patch detection rule. If it is determined in S1501 that the shape is rectangular (YES in S1501), the process ends. If it is determined in S1501 that the shape is not rectangular (NO in S1501), the controller 102 adds a dummy flag to the patch data in S1502. The data representing the color of the patch data added at this time may be any color such as white.

  Next, in S1503, the controller 102 stores the patch data to which the dummy flag is added in S1502 in the pre-selection patch data 608, and repeats the same processing until it becomes a rectangular shape. When the rectangular shape is used, a dummy flag is added to the patch data that is blank, so that the calculation is performed in comparison with the method of searching for usable patch data from the patch candidate data 707 as shown in FIG. The amount can be reduced.

  In the process of arranging data based on the detection rule of S913 described in the first embodiment, the data is arranged using the rule-specific patch data 911, but the data with the dummy flag added is separated from the patch data. The process of replacing with the data of the existing patch is performed. For example, when a dummy flag is added to a patch of M rows and 4 columns, replacement is performed with patch data of 1 row (N-4) columns. Then, the patch to which the dummy flag is added is not arranged at the patch position used in the patch detection rule.

  After the process of classifying the data of S1313 described in the first embodiment into a chromatic color and an achromatic color, the patch data to which the dummy flag is added is averaged with the patch data to be replaced. Thereby, it is possible to take into account density unevenness in the chart of the chart by the output device, and it is possible to obtain patch data that does not affect the density unevenness.

  Although the patch data addition processing method in the present embodiment has been described, the present invention is not limited to this, and a method of suppressing the influence of density unevenness on the chart surface by the output device by adding dummy patch data to the patch data. Any method may be used.

  According to the present invention, not only the color difference between patches is considered to be equal to or greater than a certain interval, but also the created chart takes into account density unevenness in the chart printed by the output device. As a result, patch data that does not affect density unevenness can be obtained, and patch data can be created with a smaller amount of calculation compared to the first embodiment.

<Third embodiment>
Next, a method for adding patch data when a specific color is considered will be described. In the previous embodiment, the processing for adding patch data in which the color difference between patches is equal to or greater than a certain interval in consideration of the color mixing characteristics of the output device has been described. However, in the method described above, it is not possible to designate a color for which correction accuracy is particularly desired to be improved. On the other hand, in the present embodiment, a patch data adding process method using specific color information in the chart patch data adding process will be described. Here, only the difference from the first embodiment is described, and the same processing as that of the first embodiment is performed for overlapping portions.

  First, a method for creating the specific color information 1603 will be described. The display device 118 displays a specific color input screen for inputting a specific color. An example of the specific color input screen which is a reception unit will be described with reference to FIG.

  The display device 118 displays forms 1902, 1903, 1904, and 1905 for inputting C, M, Y, and K for specifying a specific color in the UI 1901. Each form can be input numerical values using the input device 120. The range of input values is 0 to 100 in the case of CMYK values. The form 1902 is for inputting a numerical value of C. Similarly, the form 1903 is M, the form 1904 is Y, and the form 1905 is K.

  When a “measurement by colorimeter” button 1906 is pressed, a measurement value using the colorimeter can be designated as an input value. For example, the colorimeter 126 performs colorimetry of a color patch to be designated as a specific color and acquires a colorimetric value. Next, for the colorimetric values, the controller 102 may receive data using the network I / F 122 via the network 123 and acquire the measurement values of a specific color. When the measured color space is an L * a * b * value, it may be input as an L * a * b * value or may be a value converted into a CMYK value.

  When the “L * a * b * switch” button 1907 is pressed, the input screen is switched from the CMYK input screen to the L * a * b * input screen. As an example of the input range of L * a * b * values, L * may be 0 to 100, a * may be −128 to 128, and b * may be −128 to 128. Of course, the number of input forms in the case of L * a * b * is three. When the “next” button 1908 is pressed, a screen for inputting the next specific color is displayed, and the number of specific colors can be added. When an “end” button 1909 is pressed, the input of the specific color is ended, and the values input so far are retained using a nonvolatile memory in the storage device 121 or the controller 102.

  The specific color information 1603 is created by performing the above operation.

(Additional processing of patch data)
FIG. 16 describes the flow of the patch data addition process of S715 of FIG. 7 in the first embodiment, and corresponds to FIG. 8 of the first embodiment. In addition to selecting patch data having a certain color difference from other patch candidate data performed in FIG. 7, patch data that can be used as a specific color in the specific color information 1603 is added. The following processing is performed according to an instruction from the CPU 103 of the controller 102, and data is stored using a nonvolatile memory in the storage device 121 or the controller 102. In FIG. 16, S (step) is given to the processing step with a reference number. In each figure, arrows indicated by solid lines indicate the flow of processing, and arrows indicated by broken lines indicate the flow of data such as reference and output of data used in the processing.

  First, in step S <b> 1601, the controller 102 acquires one piece of patch data of the patch candidate data 707. In the present embodiment, the patch candidate data 707 to be acquired is acquired at random in order to eliminate bias in the color of the patch data to be added. The acquisition method is not limited to this. In step S1602, the controller 102 acquires specific color information 1603, and determines whether the patch data acquired in step S1601 is patch data of a specific color. Here, when it is determined that the patch data can be used as the specific color patch data, the determination is performed based on whether the color difference between the L * a * b * value in the specific color information 1603 and the patch data is smaller than the threshold for specific color determination.

  Next, in step S1604, the controller 102 performs determination using the result of determining whether the patch can be used in the specific color in step S1602. If it is determined in S1604 that the patch can be used as a specific color (YES in S1604), the controller 102 acquires one piece of patch data from the pre-selection patch data 608 in S1605. In step S1605, the controller 102 calculates the color difference between the patch candidate data acquired in step S1601 and the pre-selection patch data acquired in step S1605.

  In step S1607, it is determined whether the color difference calculated in step S1606 exceeds a threshold value. Since the threshold is for adding patch data of a specific color or for avoiding bias in correction accuracy between grid points, the grid point interval in the case of the maximum grid point number Pmax may be used as the threshold.

  If the color difference does not exceed the threshold (NO in S1607), in S1610, the controller 102 determines whether all pre-sorting data has been processed. If the color difference exceeds the threshold value in S1607 (YES in S1607), the controller 102 stores the patch candidate data in the pre-selection patch data 608 in S1608. In step S <b> 1609, the controller 102 determines whether the chart is rectangular using the patch detection rule 607. This determination method is the same as the method of S714 described in the first embodiment.

  If the chart is rectangular in S1609 (YES in S1609), the process ends. If the chart is not rectangular in S1609 (NO in S1609), the controller 102 determines in S1611 whether all patch candidate data has been processed.

  If all the pre-sorting data has not been processed (NO in S1610), the controller 102 acquires the pre-sorting patch data 608 in S1605 and repeats until all the data is processed. If all pre-sort data has been processed (YES in S1610), the controller 102 determines whether all patch candidate data has been processed in S1611. If all the patch candidate data has not been processed (NO in S1611), the controller 102 reads the patch candidate data in S1601. If all pre-sorting data has been processed (YES in S1611), the chart cannot be detected because the chart has not become rectangular. Therefore, the controller 102 stores dummy data in the pre-selection patch data 608 for the patch data that is sufficient until it becomes rectangular in S1612, and ends the process. For example, as the dummy data data, white L * a * b * value (L *, a *, b *) = (100, 0, 0) may be used, or as described in the second embodiment. The method may be performed.

  The number of pieces of data into which patch data for a specific color is previously determined is determined, and the number of grid points is determined in consideration of the number of data for the specific color patch data when determining the number of grid points to be used for the chart in S712. You may decide. In that case, the addition process of the patch data is always performed, and the number of data for the specific color patch data to be added can be added. As a result, it is possible to create a four-dimensional LUT that corrects the color mixture of the specific color with high accuracy, and to perform correction around the color to be corrected.

  Although the patch data addition processing method in the present embodiment has been described, the present invention is not limited to this, and any method may be used as long as the patch data can be added to the chart using specific color information.

  According to the present invention, not only the color difference between patches is considered to be equal to or greater than a certain interval, but patch data of a color close to the color for which correction accuracy is particularly desired to be added can be added. As a result, it is possible to create a four-dimensional LUT that corrects mixed colors in consideration of specific color information, and to perform correction around the color to be corrected.

<Other embodiments>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes 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, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (10)

An image processing apparatus that generates chart data of a chart output by an output device,
Reproduction information acquisition means for acquiring color reproduction range information indicating a color range that can be reproduced by the output device;
Candidate creation means for extracting colors in a device-independent color space from among the colors included in the range indicated by the color reproduction range information, and using them as patch candidate data;
According to the number of patches included in the chart data specified in advance, an acquisition unit that acquires patch data from patch candidate data created by the candidate creation unit;
Chart generating means for generating chart data using the patch data acquired by the acquiring means;
An image processing apparatus comprising: conversion means for converting the chart data generated by the generation means into data in a device-dependent color space. The candidate creation means includes
Data acquisition means for acquiring color difference equal data indicating each lattice point having an equal color difference in a device-independent color space;
Determination means for determining a lattice point within the color reproduction range indicated by the color reproduction range information among the lattice points indicated by the color difference equal data;
The image processing apparatus according to claim 1, further comprising a holding unit that holds, as patch candidate data, values of grid points determined by the determination unit as being within the color reproduction range. The acquisition means includes
Determination means for determining whether or not chart data composed of the number of patches included in the pre-designated chart data can be generated using the acquired patch data;
The image processing apparatus according to claim 2, further comprising an adding unit that adds patch data when it is determined by the determination unit that the chart data cannot be generated.   The image processing apparatus according to claim 3, wherein the adding unit adds, as patch data, data having a color difference equal to or greater than a predetermined value for each piece of acquired patch data.   The image processing apparatus according to claim 3, wherein the adding unit adds data having a predefined value as patch data. Further comprising a receiving means for receiving a designation of a specific color to be included in the chart data from a user;
The adding means has a color difference with the specific color that is less than or equal to a predetermined value in the held patch candidate data, and a color difference with the patch data acquired by the acquisition means is greater than or equal to a predetermined value. The image processing apparatus according to claim 3, wherein patch candidate data is added as patch data. The chart generating means includes
Classifying the patch data acquired by the acquisition means according to a predefined rule, and arranging means for arranging according to the classification;
The image processing apparatus according to claim 1, further comprising means for creating chart data from the arranged patch data. It further comprises measuring means for measuring the chart output by the output device,
The measuring means includes
Means for obtaining image data from the output chart using a scanner;
Means for converting the acquired image data from a device-dependent color space to a device-independent color space;
Means for detecting an edge of the chart from the image data and determining the inclination of the chart from the edge;
Means for calculating an edge of the chart from the detected edge of the chart when it is determined that the slope is equal to or less than a threshold;
Means for identifying the center position of each patch included in the image data using the calculated chart end and the chart configuration information, and obtaining a signal value from the center position of the patch;
Means for determining whether or not the scanner is correctly arranged as a direction in which the chart is measured from the signal value of the acquired patch and the configuration information of the chart;
The image processing apparatus according to claim 1, further comprising: a unit configured to use a signal value of the acquired patch as a colorimetric value when it is determined that the chart is correctly arranged. An image processing method for generating chart data of a chart output by an output device,
A reproduction information acquisition step for acquiring color reproduction range information indicating a color range that can be reproduced by the output device;
Candidate creating means extracts a color in a device-independent color space from the colors included in the range indicated by the color reproduction range information, and creates a candidate patch as candidate data,
An acquisition step of acquiring patch data from patch candidate data created by the candidate creation unit according to the number of patches included in the chart data designated in advance,
A chart generation unit that generates chart data using the patch data acquired in the acquisition step, and a conversion unit converts the chart data generated in the generation step into data in a device-dependent color space. An image processing method. Computer
Reproduction information acquisition means for acquiring color reproduction range information indicating a color range that can be reproduced by the output device,
Candidate creation means for extracting colors in a device-independent color space from among the colors included in the range indicated by the color reproduction range information, and using them as patch candidate data;
Obtaining means for obtaining patch data from patch candidate data created by the candidate creating means in accordance with the number of patches included in the chart data designated in advance;
Chart generating means for generating chart data using the patch data acquired by the acquiring means;
A program for causing the chart data generated by the generating means to function as conversion means for converting data into device-dependent color space.

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