JPH05336552A - Evaluation color selecting method - Google Patents

Abstract

PURPOSE:To select an optimum color for evaluation in a specific color chip by selecting a representative color for evaluation in each of areas divided by an area dividing means using a statistical method. CONSTITUTION:A color reproduction range measurement part 1 finds the range of colors that equipment to be evaluated can output and a candidate color measurement part 2 measures all pigments as candidates for the evaluation color. Further, an area division part 3 clips the data measured by the candidate color measurement part 2 within the color reproduction range measured by the color reproduction range measurement part 1 and divides the area into a specified number of areas, and a selection part 4 determines the best evaluation color for the equipment to be evaluated. Namely, the finally selected evaluation color is securely present in the range of the colors that the equipment to be evaluated can output, so no unnecessary adjustment is made and the evaluation color is selected according to the statistical properties of the range of the colors which can be outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of selecting an evaluation color for color adjustment and color correction of an image processing apparatus using color.

[0002]

2. Description of the Related Art A device that outputs a color, such as a color display or a color printer, cannot output any color. In fact, the range in which the color can be reproduced is individually limited by the performance of each device. Has been done. Although there is a limitation depending on the performance of the device itself, a general-purpose test chart that has not conventionally considered the individual performance of the device is used for evaluation, and the colors output from the device and the output The color was adjusted so that the colors would be the same.

[0003]

The color that can be output by a device that outputs a color depends on the output device used by the device, as described above. For example, a color printer depends on the spectral characteristics of ink, and a color display depends on the fluorescent substance of a cathode ray tube.

When color adjustment is performed on such a device in order to correctly output a specific color chart,
Some existing test charts are used as evaluation colors for adjustment.

However, this method has the following problems. The first problem is that such test charts often do not take into consideration the characteristics of the colors that individual devices can output, and there are colors that cannot actually be output by that device in the test charts. Therefore, it is meaningless to evaluate color reproducibility for colors that cannot be actually output by the device.

As a second problem, the number of colors used for actual adjustment is often very limited. However, it is difficult to adjust so that the color can be accurately output with a limited number of colors. On the other hand, if accuracy is required, it is better to measure and adjust all the color charts of the particular test chart, but this is not realistic because it requires a lot of work. In this way, the trade-off between time and accuracy required for adjustment is a big problem.

In order to solve the above-mentioned problems, it is necessary to select a set of colors from a specific color chart that can easily evaluate the colors output by each individual device. An object of the present invention is to provide a method for optimally selecting a color for evaluation from a specific color chart in consideration of the performance of a device to be adjusted.

[0008]

In order to achieve the above object, the evaluation color selection method of the present invention is a method for selecting an evaluation color for adjusting the output color of an apparatus for outputting a color, wherein a reference pattern of color is used. The reference pattern data generating means for generating data, the reference pattern data output means for outputting the reference pattern data generated by the reference pattern data generating means to the device for outputting the color, and the device for outputting the color A color measurement unit that measures the output result of the reference pattern data, a color reproduction range configuration unit that calculates a color reproduction range from the measurement result measured by the color measurement unit, and an existing color chip that is a candidate for an evaluation color Based on the color chart measuring means to be measured, the color chart data measured by the color chart measuring means, and the color reproduction range calculated by the color reproduction range configuring means. A color reproduction range specifying unit that selects color chip data that can be reproduced by the device that outputs the color, and the color chip data selected by the color reproduction range specifying unit are plotted in a coordinate space indicated by the color chip data, and An area dividing means for dividing the coordinate space and a statistical calculation means for selecting a representative color from each area divided by the area dividing means by using a statistical method are provided. ..

[0009]

The reference pattern generation means generates color reference pattern data, and the reference pattern data output means outputs the reference pattern data to a device for outputting a color, that is, a device that requires color evaluation and adjustment. The color measuring means measures the output result of the reference pattern data output from the device that outputs the color. The color reproduction range configuring means calculates the color reproduction range from the measurement result measured by the color measuring means. The color chart measuring means measures an existing color chart which is a candidate for an evaluation color. The color reproduction range specifying means is color chart data that can be reproduced by a device that outputs the color based on the color chart data measured by the color chart measuring means and the color reproduction range calculated by the color reproduction range configuring means. Select. The area dividing means plots the color chart data selected by the color reproduction range specifying means in a coordinate space indicated by the color chart data and divides the coordinate space. The statistical calculation means selects a representative color for evaluation from each area divided by the area division means by using a statistical method.

[0010]

1 is a block diagram of the present invention. Reference numeral 1 is a color reproduction range measuring unit that obtains a range of colors that can be output by the device to be evaluated. A candidate color measuring unit 2 measures all color patches that are candidates for evaluation colors. An area dividing unit 3 clips the data measured by the candidate color measuring unit 2 in the color reproduction range measured by the color reproduction range measuring unit 1 and divides the region into a specified number. A selection unit 4 determines an evaluation color most suitable for the device to be evaluated.

The detailed structure required for the above processing is shown in FIG. The configuration is CPU 5, color measuring device 6, full-color output device 7, RAM 8, ROM 9, input interface 1.
0, an output interface 11, and a bus 12.

The full-color output device 7 corresponds to the device to be evaluated and is a device such as a color display or a color printer capable of outputting colors.

The input interface 10 is a color measuring device 6
Used to pass data from the bus to the bus 12. The output interface 11 is used for data transfer from the bus 12 to the full-color output device 7.

Color measuring device 6, full color output device 7, R
The CPU 5 intervenes via the bus 12 to exchange data between the AM 8 and the ROM 9. The color measuring device 6 includes a scanner, a colorimeter, a video camera and the like.

The RAM 8 is a storage device and comprises a color reproduction range storage section 80, a candidate color storage section 81, an area storage section 82 and the like. Further, the ROM 9 is a color reproduction range configuring means 9
0, candidate color measuring means 91, area dividing means 92, statistical calculating means 93, data converting means 94, reference data generating means 9
5. The color reproduction range identifying unit 96 is provided, and specifically, programs and data for executing each process are stored.

The detailed processing flow is shown in FIG. The color reproduction range measuring unit 1 performs three processes. First, step S1
A reference pattern for color gamut measurement is created at 0. This is the processing of the CPU 5 to output the reference data by the reference data generating means 95 of the ROM 9 to the output interface 11
To the full-color output device 7, and the full-color output device 7 outputs the reference data.

As the reference data, for example, a method of dividing a cube made of RGB and a method of dividing a biconical body made of lightness, hue, and saturation can be considered. FIG. 4 shows an example in which each side of the RGB cube is evenly divided, and FIG. 5 shows an example in which the brightness of the biconical body is evenly divided and the hue is equally divided.

In either case, it is not always necessary to divide equally, and the state of division depends on the method of the color reproduction range forming means 90. 4 and 5 are examples in which the color at the intersection of the broken lines is extracted and used as the reference data. The back side portion is omitted in the drawing, but the back side portion is also used.

Next, in step S11, step S10
Then, the reference pattern output by the full-color output device 7 is measured. The data measured by the color measuring device 6 is stored in the color reproduction range storage unit 80.

In step 12, the color reproducible range of the device to be evaluated is constructed as a three-dimensional solid in the color coordinate space based on the data measured in step S11 and stored in the color reproduction range storage section 80. To do. Hereinafter, this solid will be referred to as a color reproduction solid. The color reproduction range configuring means 90 stores this configuration procedure.

The composed data is again stored in the color reproduction range storage unit 8
Save to 0. A method of constructing a color reproduction solid is, for example, plotting measured data in a three-dimensional space of color coordinate space, connecting the closest data with a straight line, and forming a patch of triangular patches. There are possible ways to get it. An example of this is shown in FIG.

Next, in step 20, the candidate color measuring section 2
However, the existing specific color patch that is a candidate is measured using the color measuring device 6. The candidate color measuring unit 91 stores this procedure. The measured data is stored in the candidate color storage unit 81. The color measuring device 6 used at this time has a step S11.
It is necessary to use the same device as the color measuring device used in 1) under the same conditions.

The area dividing section 3 executes four processing steps. First, in step S30, a color that can be reproduced by the device to be evaluated is selected from the data measured by the color reproduction range measurement unit 1 and the candidate color measurement unit 2 and stored in the color reproduction range storage unit 80 and the candidate color storage unit 81. The result is stored in the candidate color storage unit 81. The color gamut specifying means 96 stores this means.

The following method can be considered as this selection method. The data measured by the color reproduction range measuring unit 1 and the candidate color measuring unit 2 are plotted on the three-dimensional space coordinates of the color coordinate space. The spatial coordinate system may be any system that uses lightness and two other data to represent a color. For example, CIELAB and HSI can be considered.

It is now assumed that two data other than lightness are hue and saturation. Candidate colors plotted outside the color reproduction solid plotted in this space cannot be color-reproduced by the device to be evaluated, and are not candidates for evaluation colors. Only candidate colors included in the color reproduction solid are candidates for evaluation colors. Now, it is assumed that the number of candidates for this evaluation color is m.

Next, in step S31, the number of evaluation colors is determined. This number is empirically determined by a trade-off between the labor and accuracy of measurement, but the number is generally about 10 to 20% of the number of colors on the color chart. Here, n evaluation colors are selected.

Next, in step S32, step S30
Divide the area plotted in step 1. The divided result is stored in the area storage unit 82. The zone dividing means 920 of the area dividing means 92 stores this procedure.

The following method can be considered for zone division. The three-dimensional spatial coordinate system plotted in step S30 is projected onto two-dimensional plane coordinates represented by two data other than lightness to divide this plane. For example, a method of radially dividing the origin may be considered. FIG. 7 shows an example in which the origin is divided into eight. Each of the divided areas will be called a zone. Here, the zone is divided into z zones.

Next, in step S33, the zone is further divided using the data stored in the area storage section 82. The divided result is stored in the area storage unit 82. The subzone dividing unit 921 stores this procedure. The concrete dividing means is as follows. Among the z-divided zones, the number of color chip data existing in a certain zone i is Ti. Number Si for subdividing a zone i
Is

[0030]

[Equation 1]

It is determined by The area obtained by dividing the zone is called a subzone.

As an example of such a dividing method, as shown in FIG. 8, the first zone, the fourth zone, the fifth zone, and the eighth zone are divided only by the coordinate value of the horizontal axis of the data in the zone, There is a method of dividing the second zone, the third zone, the sixth zone, and the seventh zone similarly only by the coordinate value of the vertical axis. As other division methods, a division method based on the distance from the origin to the data or a division method based on the angle formed by the data and the coordinate axes can be considered.

The ordinate and abscissa of FIG. 8 differ depending on the selected color coordinate space. For example, in CIELAB, the vertical axis is b
*, The horizontal axis is a *. At this time, the sub-zones in the same zone are divided so that the number of data is the same. If it cannot be divided, try to fit within the error range of ± 1.

FIG. 9 shows an example of sub-zone division when the number of colors to be selected is 50, the number of colors that can be output is 522, and the number of zones is 8.

Finally, the selection unit 4 selects the evaluation color by a statistical method using the data stored in the area storage unit 82. The statistical calculation means 93 stores this procedure. The following methods can be considered as statistical calculation means. Average the data in each subzone. Then, the data closest to the average in each subzone is set as the representative color of the subzone. Since the number of sub-zones is n, by collecting the representative colors of each sub-zone, it is possible to select n representative colors having the statistical properties of a specific color chart of m colors and the characteristics peculiar to the device to be evaluated. it can.

[0036]

EFFECTS OF THE INVENTION Conventionally, when adjusting a device that outputs a color, a test chart that does not match the range of colors that can be reproduced by the device is used as it is, or an evaluation color is selected in advance from the test chart and used. Was there. In addition, even if this selection is made, it is not known whether the evaluation color is a color that can be reproduced by the device. Therefore, in such a method, colors that cannot be reproduced by the device to be evaluated are often mixed in the evaluation colors. Therefore, when a certain evaluation color is a color that cannot be reproduced by the device, the adjustment itself is meaningless.

Further, when it is desired to strictly evaluate and adjust the reproducibility, it is necessary to evaluate as many colors as possible, but this is an enormous amount of work. , There was also such a trade-off between effort and accuracy.

When the method of the present invention is used, the finally selected evaluation color surely exists within the range of colors that can be output by the device to be evaluated, so that the above meaningless adjustment does not occur. In addition, since the evaluation color is selected based on the statistical properties of the range of colors that can be output, it is possible to make accurate evaluations and adjustments of color reproducibility for each individual device that is evaluated, making an optimal evaluation. You can choose a set of colors.

[Brief description of drawings]

FIG. 1 is a block schematic diagram of the present invention.

FIG. 2 is a diagram illustrating details of the configuration of the present invention.

FIG. 3 is a flowchart illustrating a process of the present invention.

FIG. 4 is a diagram showing an example in which an RGB cube is divided for creating reference data.

FIG. 5 is a diagram showing an example in which a bicone is divided to create reference data.

FIG. 6 is a diagram showing an example of a color reproduction solid created by attaching triangular patches.

FIG. 7 is a diagram showing an example in which a region is divided into eight on a plane represented by hue and saturation.

FIG. 8 is a diagram showing an example of subzone division.

FIG. 9: 50 colors to be selected and 52 color chips that can be output
It is a figure which shows an example when it is two colors and there are eight zones.

[Explanation of symbols]

 1 Color Reproduction Range Measurement Unit 2 Candidate Color Measurement Unit 3 Area Division Unit 4 Selection Unit 5 CPU 6 Color Measurement Device 7 Full Color Output Device 8 RAM 9 ROM 10 Input Interface 11 Output Interface 80 Color Reproduction Range Storage Unit 81 Candidate Color Storage Unit 82 Area storage unit 90 Color reproduction range configuring means 91 Candidate color measuring means 92 Area dividing means 93 Statistical calculation means 94 Data converting means 95 Reference data generating means 96 Color reproduction range specifying means 920 Zone dividing means 921 Subzone dividing means

Claims (1)

[Claims] 1. A method of selecting an evaluation color for adjusting an output color of an apparatus for outputting a color, wherein a reference pattern data generating means for generating reference pattern data of color and a reference pattern data generating means for generating the reference pattern data are generated. Reference pattern data output means for outputting the reference pattern data to the device for outputting the color, color measuring means for measuring an output result of the reference pattern data output from the device for outputting the color, and the color measuring means. Color reproduction range forming means for calculating a color reproduction range from measured measurement results, color chart measuring means for measuring existing color charts that are candidates for evaluation colors, and color chart data measured by the color chart measuring means. And a color reproduction range that selects color chart data that can be reproduced by a device that outputs the color, based on the color reproduction range calculated by the color reproduction range configuration means. The area specifying means, the color chart data selected by the color reproduction range specifying means are plotted in the coordinate space indicated by the color chart data, the area dividing means divides the coordinate space, and the area dividing means divides the coordinate space. And a statistical calculation means for selecting a representative color from each area using a statistical method.