JP7141021B2 - Color chart generation method, color chart generation device and program - Google Patents

Description

The present invention relates to a color chart generating method, a color chart generating apparatus, and a program for generating print data of a color chart in which a plurality of patches to be compared with a sample are arranged.

In recent years, on-demand machines have improved their ability to handle package printing, such as the use of special toners such as white and clear, and the ability to use thick paper and transparent media. It is also widely used for printing packages. Packaging is often printed using spot colors designed for offset printing presses. If the on-demand machine does not have the special color material itself when printing a document containing a spot color on the on-demand machine, C (cyan), M (magenta), Y (yellow), and K that the on-demand machine has (Black) and other basic color materials must be mixed to simulate a color close to the particular color. Generally, this is done by having the printer controller convert the spot color name described on the manuscript data in PDF (portable document format) into device values such as CMYK. Therefore, the printer controller internally has a conversion table for converting "spot color name" to "device value". Furthermore, in order to enable adjustment of the output color, the user can arbitrarily change the device values registered in the conversion table.

When fine-tuning the output color corresponding to the special color (spot color) on the on-demand machine, print a color chart with multiple color patches and compare the color of each printed patch with the color of the sample. There is a way to select the most preferred patch among the patches.

However, this selection method requires skill to select the preferred patches. One factor is that color values are expressed in three dimensions in color spaces such as L ^* a ^* b ^* and in four dimensions in CMYK device values, whereas patches are expressed on a two-dimensional (flat) chart. Since they are arranged, it is necessary to provide a plurality of patch groups arranged two-dimensionally in order to correspond to three-dimensional or four-dimensional, and it is necessary to search for a color close to a sample from many patch groups. . FIG. 17 shows 9 patches × 9 groups (one group is 3 × 3 patches in which C and M are changed ±2 with respect to the central patch, and Y and K are changed ±2 with respect to the central group. An example of a color chart printed with 9 groups of 3×3) is shown. Patches with different Y and K values are scattered in different groups, making comparison difficult and time-consuming.

Also, if the spot color of the sample is within the reproducible color gamut of the printing device, it is sufficient to select a patch of a color that matches the spot color from the color chart. However, if the spot color of the sample is outside the reproducible color gamut of the printing device, it is necessary to select the "most preferred" patch from a color chart in which there cannot be a patch that matches the spot color. Determining whether a color is optimal requires skill. In other words, it is not just a matter of the color difference being small, but rather the characteristics of the original special color (whether there are features such as fluorescence or metallic in addition to the color tone), and depending on the case, how it is used in the printed material ( Is it a title that is expected to stand out in a single color, or is it an illustration that requires harmony with other colors? Since there is no clear standard for color selection, skill is required to determine which color is optimal.

Japanese Patent Application Laid-Open No. 2002-200000 discloses a technique for determining the number of color patches or color intervals depending on whether or not a specified color (sample color) is within the printable color gamut of a printing device (gamut type). According to this technique, when the specified color is outside the printable color gamut, the number of color patches is increased or the color interval is widened compared to the case where the specified color is inside the printable color gamut. Makes color patches selectable.

JP 2011-114717 A

As previously mentioned, patch selection criteria differ depending on whether the specified spot color is within or outside the printable color gamut of the printing device. However, conventionally, the axes in which the colors of a plurality of patches arranged on a color chart change are always C, M, Y, and K of device values, or three-dimensional axes such as L ^* a ^* b ^*. It was the axis of the color space itself. Therefore, the direction in which the user wants to change the color of the patch in comparison with the swatch does not coincide with the direction of the above axis, and the user frequently goes back and forth between different groups when selecting the patch with the optimum color. There were also problems such as not knowing well which group to move to.

Furthermore, if the color of the patch to be placed is set outside the printable color gamut, it will be converted to the printable color gamut at the time of printing, and the color difference of each patch will not be as expected. A large number of patches are generated, and even if the color interval between patches is set wide as in Patent Document 1, the effect of "change in color interval" cannot be obtained.

An object of the present invention is to solve the above-mentioned problems. A color chart that makes it easy to find a patch of a color suitable for printing a specified color depending on whether the specified color is inside or outside the printable color gamut. It is an object of the present invention to provide a color chart generation method, a color chart generation device, and a program for generating print data.

The gist of the present invention for achieving this object lies in the following inventions.

[1] a determination step of determining whether the designated color is within or outside the printable color gamut of a predetermined printing device;
an axis setting step of setting the axis within a predetermined color space by switching the method of taking the axis that is the color change direction of the plurality of patches arranged on the color chart according to the determination result of the determination step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the color selected in the color selection step are arranged in order on the set axis;
has
In the axis setting step,
When the specified color is within the printable color gamut, the specified color is set as the central color, and a half line passing through the central color starting from the achromatic color having the maximum lightness within the printable color gamut is defined as the first set it to the axis,
When the specified color is outside the printable color gamut, a color obtained by mapping the specified color to the surface of the printable color gamut is used as a center color, and from the center color along the surface of the printable color gamut Set the trajectory when changing the brightness to the first axis
A color chart generation method characterized by:

In the above invention, depending on whether the specified color is inside or outside the printable color gamut, the direction of change in the color of the patches arranged on the color chart is changed. can print a color chart in which suitable patches are selected and listed as candidates.

In the above invention, when the specified color is within the printable color gamut, the first axis is set to have the same hue as the specified color and to decrease the lightness while increasing the saturation at the same time. When the specified color is outside the printable color gamut, the first axis is set to the trajectory when the brightness is changed on the surface of the printable color gamut from the central color of the specified color mapped onto the surface of the printable color gamut. be done.

[ 2 ] In the axis setting step,
The method for generating a color chart according to [ 1 ], wherein a second axis is set in a hue angle direction orthogonal to the first axis at the center color.

In the above invention, the second axis is set in the hue angle direction.

[ 3 ] In the color selection step,
If the designated color is outside the printable color gamut and the peak of saturation is within the range of color variation along the first axis when selecting colors for the plurality of patches, The method of generating a color chart according to [ 1 ] or [ 2 ], wherein the color that is the peak of saturation is included in the colors to be selected.

In the above invention, when the peak of saturation exists within the range of color variation along the first axis of the patches arranged on the color chart, the color at the peak of saturation is included in one of the patches. To prevent a color with the highest saturation from deviating from the colors of patches arranged on a color chart.

[ 4 ] In the color selection step,
When the specified color is outside the printable color gamut, the colors of the plurality of patches are adjusted so that the distances on the surface of the printable color gamut of patches adjacent to each other in the direction of the set axis are equal. The method for generating a color chart according to any one of [ 1 ] to [ 3 ], characterized in that:

In the above invention, the colors of the patches are selected so that the distances between the patches on the surface of the printable color gamut (path distances) are equal.

[ 5 ] In the color selection step,
If the specified color is outside the printable color gamut, the colors of the plurality of patches are selected such that the brightness or saturation intervals of adjacent patches in the direction of the first axis are equal. A method for generating a color chart according to any one of [ 1 ] to [ 3 ].

[ 6 ] In the axis setting step,
When the specified color is within the printable color gamut and the inclination of the half line set as the first axis in the lightness direction exceeds a predetermined upper limit, the inclination exceeds the upper limit. The method for generating a color chart according to any one of [ 1 ] to [ 5 ], wherein the brightness of the starting point of the half line is changed so as not to

[ 7 ] In the color selection step,
changing the color difference between adjacent patches along the first axis according to the distance from the patch to the surface of the printable color gamut when the specified color is within the printable color gamut. A color chart generating method according to any one of [ 1 ] to [ 6 ].

[ 8 ] In the print data generation step,
The color chart generation method according to any one of [1] to [ 7 ], wherein print data of a color chart having only one patch group in which a plurality of patches are arranged two-dimensionally is generated.

[ 9 ] In the color selection step,
Any one of [1] to [ 8 ], wherein when the designated color is within the printable color gamut, the colors of the plurality of patches are selected within the printable color gamut. The color chart generation method described in 1.

[ 10 ] In the print data generation step,
The color chart generation method according to any one of [1] to [ 9 ], wherein print data of a color chart including display of the determination result of the determination step is generated.

[11] The color chart generation method according to any one of [1] to [ 10 ], wherein the specified color is a spot color or a substitute color for the spot color.

[ 12 ] Color correction data is created based on the result of comparison between the central color and the color obtained by measuring the color of the output obtained by printing the central color with the printing device with a colorimeter, and the color The method for generating a color chart according to any one of [1] to [11] , wherein each of the steps is performed by performing color correction based on correction data.

[13] a determination step of determining whether the specified color is within or outside the printable color gamut of a predetermined printing device;
an axis setting step of setting the axis within a predetermined color space by switching the method of taking the axis that is the color change direction of the plurality of patches arranged on the color chart according to the determination result of the determination step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the color selected in the color selection step are arranged in order on the set axis;
has
The specified color is a spot color or a substitute color for the spot color
A color chart generation method characterized by:
[14] a determination step of determining whether the designated color is within or outside the printable color gamut of a predetermined printing device;
Axis setting for setting the axes within a predetermined color space by switching the method of taking two axes, which are the directions of color change of the plurality of patches arranged in a matrix on the color chart, according to the determination result of the determination step. a step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the colors selected in the color selection step are arranged in a matrix in the order of alignment on the set axis;
has
In the axis setting step,
When the specified color is within the printable color gamut, a straight line passing through the specified color and in the direction in which the saturation increases as the lightness is lowered is taken as the first axis, and the hue angle direction is taken as the second axis.
A color chart generation method characterized by:
[15] The printing device is an electrophotographic printing device, an inkjet printing device, or an inkjet printing device using active energy ray-curable ink [1] to [14] ] The color chart generation method according to any one of .

[16] A color chart generation device for generating print data of a color chart in which a plurality of patches to be compared with a designated color are arranged,
A color chart generating apparatus comprising a processing unit that executes the color chart generating method according to any one of [1] to [15].

[17] A program executed by an information processing device,
A program comprising the steps of the color chart generation method according to any one of [1] to [15].

According to the color chart generation method, the color chart generation device and the program according to the present invention, a patch of a color suitable for printing the designated color is searched according to whether the designated color is inside or outside the printable color gamut. An easy-to-use color chart can be generated.

1 is a diagram showing a schematic mechanical configuration of a printing apparatus including a color chart generating device according to an embodiment of the invention; FIG. 2 is a block diagram showing the electrical configuration of the printing device; FIG. FIG. 11 is a flow chart showing an outline of processing for fine-tuning the device value of a spot color; FIG. FIG. 11 is a diagram showing an example of a spot color designation screen; FIG. 10 is a diagram showing an example of axes to be set when a designated color is within the printable color gamut; It is a diagram showing a second axis set in a hue angle direction orthogonal to the first axis at the center color. FIG. 10 is a diagram showing an example of axes to be set when a specified color is outside the printable color gamut; FIG. 4 is a diagram showing an example of the shape of the surface of the printable gamut represented by a succession of squares; FIG. 10 illustrates an example of selecting patch colors along an axis such that the color difference ΔE between adjacent patches is equal; FIG. 4 illustrates an example of selecting patch colors along an axis such that the distances on the surface of the printable gamut between adjacent patches (linear distances) are equal; FIG. 10 is a diagram showing an example in which a patch is added to the vertex of saturation; FIG. 10 is a diagram showing an example of adding a patch at the vertex of saturation and omitting the patch furthest from the center patch; FIG. 10 is a diagram showing an example in which a patch is added to the vertex of saturation, added so that the distance from the added patch is equal to the distance between other patches, and the position of the patch following the patch is shifted. It is a figure which shows an example of the printed color chart. FIG. 10 is a diagram showing an example of an input screen for user selection results; FIG. 10 is a diagram showing an example in which the inclination of a half line (first axis) passing through the center color is restricted; 1 is a diagram showing an example of a conventional color chart in which a plurality of patch groups are arranged; FIG.

Various embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing a schematic mechanical configuration of a printing device 3 including a color chart generating device according to an embodiment of the invention. The printing device 3 has a function of receiving print data from an external information processing terminal or server, forming (printing) an image on paper based on the print data, and outputting the image. It has a function to print a color chart in which patches for adjustment are arranged.

The printing device 3 is an electrophotographic image forming device, and includes an intermediate transfer belt that is looped endlessly, and C, M, Y, and K images that are arranged along the intermediate transfer belt. A full-color toner image is formed by superimposing C, M, Y, and K toner images on an intermediate transfer belt by an image forming unit. Then, the toner image formed on the intermediate transfer belt is transferred to the paper conveyed from the paper feed tray, and after being heat-fixed on the paper by the fixing device, the paper is output to the subsequent device or the paper discharge tray. It is designed to An in-line colorimeter 23 for measuring the color of the image formed on the paper is provided on the conveying path downstream of the fixing device.

Note that the image forming method is not limited to the above, and may be any method. For example, an inkjet method or an inkjet method printing apparatus using ink that is cured by receiving active energy rays such as ultraviolet rays may be used.

FIG. 2 is a block diagram showing the electrical configuration of the printing device 3. As shown in FIG. The printing device 3 includes a printer controller 10 and a printer body 20 . Although the printer controller 10 is built in the printing device 3 in the example of FIG. 2, the printer controller 10 may be separate from the printing device 3 .

The printer controller 10 includes a network IF (interface) 11 , a printer IF 12 , a storage section 13 , a RIP processing section 14 , an input section 15 and a display section 16 . The printer main unit 20 includes a controller IF 21, a print processing unit 22, an in-line colorimeter 23, and the like.

The network IF 11 functions to transmit and receive various types of information to and from an external device through a network such as a LAN (Local Area Network). For example, it receives print data and print instructions.

The printer IF 12 serves as an interface with the printer body 20 and outputs image data and print instructions to the printer IF 12 . The storage unit 13 includes a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, and the like. The storage unit 13 stores a spot color LUT, an ICC profile used for color conversion, and the like. The spot color LUT is a lookup table that stores the color values, device values, etc. of the spot colors in association with the color names of various spot colors.

The RIP processing unit 14 includes a CPU, and the CPU executes programs stored in the storage unit 13 to execute each step shown in the flow chart of FIG. 3 and realize various functions. The RIP processing unit 14 has a function of performing color conversion for matching the output material to a desired color using, for example, an ICC profile, a function of converting special colors in the input image data into device values (here, CMYK values), It performs a function of automatically correcting colors based on signals from the in-line colorimeter 23 and other colorimetry units, and a RIP function of rasterizing print data and developing it into image data.

Furthermore, the RIP processing unit 14 has a color chart generating unit 14a function of generating print data of a color chart for the user to finely adjust the spot color and instructing the printer main unit 20 to print a color chart based on this print data. fulfill the function of The RIP processing unit 14 uses the device value of the color of the patch that the user has judged to be the color closest to the sample of the particular color from the color chart printed for fine adjustment of the particular color, and uses the device value for the particular color in the particular color LUT. Update the device value and then use this device value for printing the spot color.

The input unit 15 has hardware keys and software keys, and receives various operations from the user. For example, it accepts a specification of a spot color, an instruction to print a color chart for fine adjustment of the specified spot color, and an input operation of the identification symbol of a patch judged by the user to be closest to the color of the sample from the color chart. The display unit 16 is composed of a liquid crystal display or the like, and displays an input operation screen and various kinds of information.

The input unit 15 and the display unit 16 may not be in the printer controller 10, and may be configured to operate in cooperation with the printer controller 10 in another PC that can be connected to a network, for example.

A controller IF 21 included in the printer body 20 serves as an interface with the printer controller 10 . The print processing section 22 includes the intermediate transfer belt, the image forming unit, the fixing device, the conveying section, and the control section for controlling these operations shown in FIG. to print.

Next, processing for finely adjusting the device values of the spot colors registered in the spot color LUT will be described.

FIG. 3 is a flowchart showing an overview of the process of fine-tuning the device values of spot colors.
In the process of fine-tuning the device value of a spot color, print a color chart in which multiple patches corresponding to the specified spot color (designated color) are arranged, and compare the patches arranged in this color chart with the spot color sample. accepts input of identification information of a patch judged by the user to have a color closest to the sample of the spot color, and changes the device value of the spot color registered in the spot color LUT based on the device value of the patch. do things Each step in FIG. 3 will be described below. When rasterizing the print data, the RIP processing unit 14 of the printer controller 10 uses the device value of the spot color read from the spot color LUT for the image data of the spot color pixel in the print data.

<Spot color (sample color) acceptance; FIG. 3, step S101>
First, a specification of a spot color (sample color) to be fine-tuned is accepted from the user. FIG. 4 shows an example of a spot color designation screen 31 displayed on the display unit 16 when a user specifies a spot color to be finely adjusted. The specified color is used as the specified color. The user selects, for example, a spot color series prepared in advance by an ink manufacturer, and further selects a spot color name to be adjusted from the spot color name list 32 therein. Note that the specification method may be direct input of the spot color name, or any other method.

After selecting the spot color name, the user inputs an instruction to start the adjustment. In the case of the spot color designation screen 31 shown in FIG. 4, after selecting one spot color name from the list 32, the adjustment chart print button 33 is pressed.

<Automatic Correction Printing and Colorimetry; FIG. 3, Step S102>
The printer controller 10 that has received the press operation of the adjustment chart print button 33 performs printing for automatic color correction and colorimetry. Specifically, the spot color LUT in the storage unit 13 is referred to using the color name of the specified color that is the spot color selected in step S101, and the specified color is converted into a device value. In the spot color LUT, at least (a) the color value of the spot color and (b) the device value of the spot color are registered using the spot color name as a key. Furthermore, information such as (c) color values of print target colors corresponding to device values, (d) flags indicating whether or not corrections and corrections have been made, and (e) memo data that can be freely written by the user is provided. It may be registered in the spot color LUT.

For the above conversion, the device values stored in the spot color LUT may be directly referenced, or the device values may be calculated from the color values registered in the spot color LUT and a predetermined printer profile.

Next, a patch is printed with the obtained device value of the specified color, and the in-line colorimeter 23 measures the color of the printed patch. Note that the patches to be printed may include, in addition to the patches of the specified color, a plurality of patches of other colors to be used for correction in the next step.

<Automatic Correction Processing; FIG. 3, Step S103>
The colorimetric values of the in-line colorimeter 23 and the color values of the print target colors corresponding to the device values described in the spot color LUT (refer to (c) described above in the spot color LUT, or (calculated using the printer profile of ), and correct (change the device value) so that the color value at the time of printing approaches the color value of the print target color. Colorimetric values of patches of other colors printed at the same time may also be used for correction, and any known technique may be used. Here, the automatically corrected device value is set to the device value of the central patch (referred to as the center patch) in the group of patches arranged on the color chart.

<Determine inside/outside color gamut of designated color; FIG. 3, step S104>
It is determined whether the color value of the designated color is within or outside the printable color gamut of the printer main unit 20. - 特許庁It is preferable to use an automatic correction reflected printer profile in which information at the time of automatic correction is reflected in a predetermined printer profile. Any known technique may be used to correct the profile based on the patch colorimetry results.

In addition, the color difference between the color value of the center patch that has been automatically corrected and the color value of the specified color (hereinafter referred to as the "theoretical color difference") can be easily determined (for example, if the color difference ΔE is less than 1, it is determined to be within the printable color gamut). do, etc.). If the determination result is out of the printable color gamut, it is preferable to further obtain the "theoretical color difference".

<Determine how to take the axis; Fig. 3, step S105>
Depending on the determination result of inside/outside of the printable color gamut, "how to take the axis" when arranging the patches on the color chart is determined. The axis corresponds to the color change direction of a plurality of patches arranged on the color chart. For example, when patches are arranged vertically and horizontally, the axis here represents the direction in which the colors of the patches arranged in the vertical direction are to be changed within the color space.

When the specified color is within the printable color gamut, the starting point is paper white (the achromatic color with the maximum lightness within the printable color gamut, or the background white of the paper when printing on white paper), and the color of the central patch. Set the half line through the first axis. When the specified color is within the printable color gamut, the specified color and the center patch color (center color) match or substantially match.

FIG. 5 shows an example of the first axis set when the designated color is within the printable color gamut. The coordinates of the cross section of the color space shown in the left part of FIG. 5 are three-dimensional, with the vertical axis representing the direction of change in brightness, the horizontal axis representing the direction of change in saturation, and the circumferential direction of a circle with the vertical axis as the direction of change in hue. It is a two-dimensional coordinate corresponding to a cross section obtained by cutting a color space (for example, L ^* a ^* b ^* space) with a plane including the vertical axis and the center color, where the vertical axis is brightness and the horizontal axis is saturation.

In the example of FIG. 5, the direction of the first axis set in the three-dimensional color space corresponds to the vertical axis direction on the color chart in which the patches are arranged two-dimensionally. That is, the color change along the first axis in the three-dimensional color space corresponds to the color change of the patches arranged along the vertical axis of the color chart.

Here, as shown in FIG. 6, the second axis is set in the hue angle direction orthogonal to the first axis at the center color. FIG. 6 is a diagram in which the L ^* a ^* b ^* three-dimensional color space is mapped to two dimensions except for lightness. The hue angle direction, which is the direction of the second axis, is the direction orthogonal to the line connecting the achromatic color axis (point) and the mapped central color when the three-dimensional color space is mapped to two dimensions excluding lightness. . The so-called hue angle direction is in the form of an arc indicated by the dashed line in FIG. There is no problem in treating them as equivalent. Although the calculation becomes complicated, the arc indicated by the dashed line may be used as the second axis.

When the designated color is outside the printable color gamut, the first axis is set to the locus when the lightness is changed along the surface of the printable color gamut from the center patch color (central color). That is, let the lightness direction along the surface of the printable color gamut passing through the color of the center patch (central color) be the direction of the first axis. When the specified color is outside the printable color gamut, the color of the center patch (preferably the color automatically corrected in steps S102 and S103) obtained by mapping the specified color onto the surface of the printable color gamut is the color of the center patch (center color). becomes.

FIG. 7 shows an example of the first axis set when the specified color is outside the printable color gamut. The color space cross section shown in FIG. 7 is the same cross section as in FIG. In the example of FIG. 7, the first axis set in the three-dimensional color space is a polygonal line, but this is likened to a straight line and is the vertical axis direction on the color chart. That is, the color change along the first axis set on the surface of the printable color gamut within the three-dimensional color space is the color change of the patches arranged in the vertical direction of the color chart.

The second axis is the same as when the specified color is within the printable color gamut, and as shown in FIG. 6, is set in the hue angle direction perpendicular to the first axis at the center color.

The shape of the surface of the printable color gamut is a continuous plane (that is, a triangle or a square) consisting of color values of 3 or 4 adjacent grids around the perimeter of the printable color gamut described in the printer profile that has been automatically corrected and reflected. , but any other known technique may be used.

FIG. 8(a) shows an example of the shape of the surface of the printable gamut represented by a succession of squares made up of four grids. The first axis when the specified color is outside the printable color gamut can be obtained from the description of the printer profile in the following procedure. First, a quadrangle containing a central patch (central color) is specified, and the lightness direction (the direction of the first axis within the quadrangle) is obtained from the color value of each vertex of this quadrangle. Next, the quadrangles adjacent to each other in the direction of brightness are sequentially specified, and the direction of the axis is obtained for each quadrangle in the same manner. FIG. 8B shows an example of the first axis obtained in this way.

A more detailed description of how the first axis is determined will now be provided. First, a straight line segment generated at the intersection of a quadrangle containing the center patch and a plane containing the brightness axis and the center patch is obtained as a line segment corresponding to the first axis in this quadrangle. Similarly, for each quadrangle adjacent in the brightness direction, a straight line segment generated at the intersection of this quadrangle and the above plane is obtained as a line segment corresponding to the first axis in the quadrangle. A first axis is defined by connecting the line segments obtained for each quadrangle.

<Determination of Color Value of Each Patch; FIG. 3, Step S106>
The color value of each patch to be arranged on the color chart is selected and determined according to the axes (first axis, second axis) determined in step S105. Here, patch colors are selected only within the printable color gamut, without selecting colors outside the printable color gamut.

For example, if the color of the center patch (central color) is within the printable gamut, the colors of the multiple patches along the first axis are equalized so that the color differences ΔE between adjacent patches are equal, as shown in FIG. to select. A plurality of patches are then selected such that the color difference ΔE between adjacent patches along a second axis in the hue angle direction through the color of the patch selected along the first axis is equal.

When the color of the center patch (central color) is outside the printable color gamut, as shown in FIG. Select the patch color along the 1 axis. Then, multiple patches such that the distances on the printable gamut surface between adjacent patches along a second axis in the hue angle direction through the color of the selected patch along the first axis are equal. to select.

Also, if the color of the center patch (center color) is outside the printable color gamut, it is determined whether or not the peak of saturation at the hue angle of that patch is sandwiched between the colors of the selected adjacent patches. , select the apex of saturation as one of the colors of the patch, if the vertices of saturation are bounded. For example, in the example of FIG. 10, there is a apex of saturation between patch P2 and patch P3, which are equally spaced. In this case, as shown in FIG. 11, a patch P8 is added to the apex of saturation, or in order to keep the total number of patches constant, a patch P8 is added to the apex of saturation and at the same time the central patch Omit the patch furthest from . In the example of FIG. 12, the patch P4 shown in FIG. 10 is omitted. When the adjacent patches are equally spaced, the patches before and after the patch arranged at the peak of saturation are an exception to the equal spacing.

Note that adding the patch P8 in FIG. 12 shortens the distance between the patch P8 and the patch P3, so as shown in FIG. The position of P3 may be shifted.

In addition, when the color of the center patch (central color) is outside the printable color gamut, the brightness interval on the printable color gamut surface between adjacent patches is equal, or the printable color between adjacent patches The patch colors may be chosen such that the saturation intervals on the surface of the gamut are equal. Even in this case, the patches before and after the patch added to the vertex of saturation are exceptions to the equal spacing.

Also, if the color of the center patch (central color) is outside the printable color gamut, the larger the theoretical color difference described above, the larger the color interval (distance) between patches or the larger the number of patches. is preferred. A wider range of patches are arranged in a color chart.

When the color of the center patch (central color) is within the printable color gamut, the greater the distance from the selected patch color to the printable color gamut, the greater the color spacing between adjacent patches in the direction of the first axis. You can make it bigger.

<Device value calculation for each patch; FIG. 3, step S107>
The device value of each patch is calculated from the color value of each patch selected in step S106. It is preferable to calculate using the printer profile that has undergone automatic correction, but any known technique may be used for calculation. The printer controller 10 stores the calculated device value of each patch in association with the patch identification symbol (such as an address, which will be described later).

<Color chart printing; FIG. 3, step S108>
Generate print data of a color chart in which patches having the calculated device values are arranged. Here, the order of patches on the first axis in the color space is the order of arrangement in the vertical direction on the color chart, and the order of arrangement of patches on the second axis in the color space is the order in the horizontal direction on the color chart. , the patches are arranged in a vertical and horizontal matrix. The print data of the color chart is preferably in EPS, PS or PDF format, for example.

FIG. 14 shows an example of a printed color chart 40. As shown in FIG. Only one patch group arranged two-dimensionally is printed on the color chart 40 as a patch group. The identification code (ID) of each patch is attached to the color chart 40 . Here, the addresses are indicated as A, B, C, D, and E in order from the left in the horizontal direction and 1, 2, 3, 4, 5, 6, and 7 in order from the top in the vertical direction as patch identification symbols. For example, the identification symbol (address) of the upper right corner patch is "E1".

In addition, the color chart 40 includes an identification symbol of the color chart itself (spot color name, date and time, etc.), information indicating whether the spot color is inside or outside the printable color gamut, and other arbitrary objects. may

<Acceptance of Input of Identification Symbol of Patch Selected by User; FIG. 3, Step S109>
The user compares the printed color chart 40 with an actual sample, selects one patch from the color chart 40 that is most suitable for printing of the designated color, and inputs the selection result to the printer controller 10 . Selection results can be entered, for example, by selecting from a pull-down list of patch identification symbols (addresses), by directly entering patch identification symbols, or by touching a touch device displaying a color chart shape. Any other input method may be used. FIG. 15 is an example of a selection result input screen 50 . On the selection result input screen 50, after selecting the appropriate patch symbol and number from the pull-down menu 51, the selection result of the patch can be input by pressing the decision button 52. FIG.

<Update spot color LUT; FIG. 3, step S110>
The printer controller 10 acquires the device value corresponding to the patch identification symbol of the selection result input in step S109 from among the device values stored in association with the patch identification symbol in step S107, and stores the device value in the spot color LUT. The device value corresponding to the spot color (specified color) accepted in step S101 in the above is updated with the acquired device value.

As described above, depending on whether the color value of the specified color is within or outside the printable color gamut of the printing device 3, the axis that is the direction in which the colors of the patches arranged on the color chart change. Since the picking method is changed, appropriate candidate color patches corresponding to the specified color can be arranged on the color chart.

Furthermore, since the colors of the patches arranged in the color chart are selected within the printable color gamut, multiple patches selected from outside the printable color gamut are converted to the same color within the printable color gamut and printed. ensuring that the color chart always reflects the color of each patch selected.

In addition, instead of arranging and presenting the three-dimensional color space in a plurality of groups as it is (see FIG. 17) as in the conventional art, it is possible to arrange and present the leading candidates in one group. Comparison can be easily performed, and even an unskilled person can quickly select the optimum patch.

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to those shown in the embodiments, and modifications and additions may be made without departing from the scope of the present invention. is also included in the present invention.

For example, when the specified spot color is within the printable color gamut, if the slope in the lightness direction of the half line (first axis) set with paper white as the starting point exceeds a predetermined upper limit, the slope is changed so as to lower the brightness of the starting point of the half line so that does not exceed the upper limit. In the example of FIG. 16, the slope of the half line is lowered below the upper limit by changing the starting point of the half line passing through the center color from paper white to an achromatic color with lower lightness. As a result, it is possible to prevent the chroma saturation from appearing too little between adjacent patches.

In the embodiment, an example in which the specified color is a spot color is shown, but the specified color is not limited to this, and may be any color. For example, it may be a substitute color for a spot color. The alternative color is a method of specifying colors in which CMYK or the like is specified instead of spot colors and associated with some device value. Spot colors and substitute colors are often outside the printable color gamut and are suitable for application of the present invention.

In the embodiment, the inline colorimeter 23 is used to measure the color of the chart for automatic correction in step S102, but the colorimetry may be performed by another colorimeter not built in the printing apparatus 3. FIG. In addition, in the automatic correction in steps S102 and S103, the correction is made so as to cancel out the color fluctuation due to the difference in the paper and the difference in the state of the printing apparatus. In practice, it is preferable to perform the automatic correction, but the automatic correction may be omitted in the implementation of the present invention.

3... Printing device 5... In-line colorimeter 10... Printer controller 11... Network IF
12 Printer IF
DESCRIPTION OF SYMBOLS 13... Storage part 14... RIP process part 14a... Color chart generation part 15... Input part 16... Display part 20... Printer main-body part 21... Controller IF
22... Print processing unit 23... In-line colorimeter 31... Special color designation screen 32... List 33... Adjustment chart print button 40... Color chart 50... Selection result input screen 51... Pull-down 52... Enter button

Claims (17)

a determining step of determining whether the specified color is within or outside the printable color gamut of a given printing device;
an axis setting step of setting the axis within a predetermined color space by switching the method of taking the axis that is the color change direction of the plurality of patches arranged on the color chart according to the determination result of the determination step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the color selected in the color selection step are arranged in order on the set axis;
has
In the axis setting step,
When the specified color is within the printable color gamut, the specified color is set as the central color, and a half line passing through the central color starting from the achromatic color having the maximum lightness within the printable color gamut is defined as the first set it to the axis,
When the specified color is outside the printable color gamut, a color obtained by mapping the specified color to the surface of the printable color gamut is used as a center color, and from the center color along the surface of the printable color gamut Set the trajectory when changing the brightness to the first axis
A color chart generation method characterized by: In the axis setting step,
2. The method of generating a color chart according to claim 1 , wherein a second axis is set in a hue angle direction perpendicular to the first axis at the center color. In the color selection step,
If the designated color is outside the printable color gamut and the peak of saturation is within the range of color variation along the first axis when selecting colors for the plurality of patches, 3. The method of generating a color chart according to claim 1 , wherein the color to be the peak of saturation is included in the colors to be selected. In the color selection step,
When the specified color is outside the printable color gamut, the colors of the plurality of patches are adjusted so that the distances on the surface of the printable color gamut of patches adjacent to each other in the direction of the set axis are equal. 4. The method of generating a color chart according to claim 1 , further comprising: selecting. In the color selection step,
If the specified color is outside the printable color gamut, the colors of the plurality of patches are selected such that the brightness or saturation intervals of adjacent patches in the direction of the first axis are equal. 4. The color chart generation method according to claim 1 . In the axis setting step,
When the specified color is within the printable color gamut and the inclination of the half line set as the first axis in the lightness direction exceeds a predetermined upper limit, the inclination exceeds the upper limit. 6. The color chart generation method according to any one of claims 1 to 5 , wherein the brightness of the starting point of the half line is changed so as not to In the color selection step,
changing the color difference between adjacent patches along the first axis according to the distance from the patch to the surface of the printable color gamut when the specified color is within the printable color gamut. 7. The color chart generating method according to claim 1 . In the print data generation step,
8. The color chart generation method according to claim 1 , wherein print data of a color chart having only one patch group in which a plurality of patches are two-dimensionally arranged is generated. In the color selection step,
9. The color of the plurality of patches is selected within the printable color gamut when the designated color is within the printable color gamut. The described color chart generation method. In the print data generation step,
10. The method of generating a color chart according to claim 1 , further comprising generating color chart print data including a display of the determination result of the determining step. The color chart generation method according to any one of claims 1 to 10 , wherein the specified color is a spot color or a substitute color for the spot color. creating color correction data based on a comparison result between the central color and a color obtained by measuring the color of an output obtained by printing the central color with the printing apparatus, and applying the color correction data to the color correction data; 12. The method of generating a color chart according to claim 1 , wherein each of the steps is performed by applying color correction based on the color chart. a determining step of determining whether the specified color is within or outside the printable color gamut of a given printing device;
an axis setting step of setting the axis within a predetermined color space by switching the method of taking the axis that is the color change direction of the plurality of patches arranged on the color chart according to the determination result of the determination step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the color selected in the color selection step are arranged in order on the set axis;
has
The specified color is a spot color or a substitute color for the spot color
A color chart generation method characterized by: a determining step of determining whether the specified color is within or outside the printable color gamut of a given printing device;
Axis setting for setting the axes within a predetermined color space by switching the method of taking two axes, which are the directions of color change of the plurality of patches arranged in a matrix on the color chart, according to the determination result of the determination step. a step;
a color selection step of selecting the colors of the plurality of patches arranged in the color chart by changing the colors along the set axis;
a print data generation step of generating print data of a color chart in which the patches of the colors selected in the color selection step are arranged in a matrix in the order of alignment on the set axis;
has
In the axis setting step,
When the specified color is within the printable color gamut, a straight line passing through the specified color and in the direction in which the saturation increases as the lightness is lowered is taken as the first axis, and the hue angle direction is taken as the second axis.
A color chart generation method characterized by: 15. The printing apparatus according to any one of claims 1 to 14, wherein the printing apparatus is an electrophotographic printing apparatus, an inkjet printing apparatus, or an inkjet printing apparatus using active energy ray-curable ink. The color chart generation method described in 1. A color chart generation device for generating print data of a color chart in which a plurality of patches to be compared with a designated color are arranged,
A color chart generation apparatus comprising a processing unit that executes the color chart generation method according to any one of claims 1 to 15. A program executed by an information processing device,
A program comprising each step of the color chart generation method according to any one of claims 1 to 15.

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