JP2008139920A - Colorimetric value acquisition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colorimetric value acquisition method for avoiding an increase in workload and output cost by suppressing repeated outputs of color charts until color non-uniformity does not newly occur on a face when the color non-uniformity occurs on the face of a color patch in a color chart to be output from a printer. <P>SOLUTION: In creating a device profile showing output characteristics of a printer when the color non-uniformity occurs on the face by the reason why a color material is not painted uniformly at the color patch in the color chart to be output from the printer, the method avoids an increase in workload in which the color charts are repeatedly output until the color non-uniformity occur does not occur, and avoids an increase in output cost in the repeated outputs by substituting a colorimetric value of a color chart outputted previously to obtain the colorimetric value of the patch in the color chart in which the color non-uniformity has occurred on the face by taking temporal variation in the printer into account. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a colorimetric value acquisition method for acquiring a colorimetric value at a location of a color patch where in-plane color unevenness occurs in a color chart, and more specifically, the output characteristics of an output machine (hereinafter referred to as a printer). When creating a device profile to represent, when measuring color patches in the color chart, color unevenness occurs due to the color material not being applied evenly within the surface of the color chart output from the printer Do not repeatedly output a color chart until color unevenness no longer occurs in the surface, and the current printer output reproducibility from the color chart color measurement values output when creating a device profile in the past. Select the colorimetric value of the color chart that was output in the closest state, substitute the selected colorimetric value, and color that has in-plane color unevenness in the color chart It relates colorimetric value acquisition method for acquiring a colorimetric value of the location of the pitch.

  In recent years, when performing color matching of printed matter output between different printers, a color management system (hereinafter referred to as CMS) using a device profile that represents the output characteristics of a printer, the specifications of which are specified in Non-Patent Document 1. Is being operated.

  In this CMS, when creating a device profile for an ICC-compliant printer, each individual printout in a color chart print consisting of an array of color patches made up of hundreds to thousands of CMYK or RGB output from the printer. The color patches are measured with a measuring device, and the spectral reflectance of each color patch and the colorimetric values such as CIEXYZ and CIE L * a * b * are obtained. Then, the acquired colorimetric values represent printer output characteristics in which the correspondence between the printer device values such as CMYK and RGB and the colorimetric values such as CIEXYZ and CIE L * a * b * are described internally. A device profile is created using a profile creation application program.

Then, color matching is performed using a device profile representing the output characteristics of the color sample side printer and a device profile representing the output characteristics of the color calibration side printer created by the profile creation application program.
ICC Specification ICC.1: 2004-10 (Profile version 4.2.0.0)

However, when creating an ICC-defined device profile representing the output characteristics of the printer, the output reproducibility of the printer as the output machine is stable, that is, device values (CMYK, RGB) input to the printer. And the colorimetric values (CIEXYZ, CIE L * a * b *) of the color output from the printer are always required to be kept constant. However, in practice, the output reproducibility of the printer constantly varies with time, and the variation range varies depending on the printer model. For this reason, it is necessary to perform calibration for correcting the printer to a normal original state or to re-create a device profile for each change. (For example, see Patent Document 1)
JP 2005-203855 A

  However, when re-creating a device profile, as described above, a color chart composed of an array of color patches consisting of hundreds to thousands of CMYK or RGB is output from the printer. In addition, there may be color patches in the color chart that cause in-plane color unevenness where the color material is not uniformly applied.

  Even if measurement is performed on a color patch in which color unevenness in the surface of the color chart exists, the color of the color patch from the printer with respect to the input device values (CMYK, RGB). It is conceivable that the original colorimetric value of the output color patch cannot be acquired.

  Therefore, when there are many color patches in which in-plane color unevenness occurs, when a device profile is created using the measured colorimetric values as they are, the printer device values such as CMYK and RGB, Since the correspondence between the colorimetric values such as CIEXYZ and CIE L * a * b * is not correctly described in the profile, the accuracy of the device profile may be deteriorated.

  Therefore, if there are many color patches with in-plane color unevenness in the color chart, the profile creation color chart is output again and repeated until in-plane color unevenness does not occur in the color patch. Therefore, problems such as an increase in workload and output cost at the time of output occur.

  Therefore, according to the present invention, when creating a device profile representing the output characteristics of the printer, color unevenness occurs due to the fact that the color material is not uniformly applied within the surface of the color patch in the color chart output from the printer. In this case, an object of the present invention is to provide a colorimetric value acquisition method capable of avoiding an increase in work load and output cost by not repeatedly outputting a color chart until color unevenness does not newly occur in the surface.

  In order to achieve the above-described object, a colorimetric value acquisition method according to the present invention is a method for acquiring a colorimetric value at a location where color unevenness occurs in a surface of a printed material output from an output device, the printed material Determining the position where color unevenness occurs in the surface by means of color unevenness determining means within the surface, and from the colorimetric value group of the printed matter output in the past from the output device, the color of the current output device A step of selecting a colorimetric value of a printed matter output in a state closest to reproducibility, and a place where it is determined that color unevenness has occurred by the color unevenness determining unit, using the selected colorimetric value instead And a step of acquiring the colorimetric value as a colorimetric value.

  According to such a colorimetric value acquisition method of the present invention, when creating a device profile representing the output characteristics of a printer, the color material is not uniformly applied to the color patches in the color chart output from the printer. In the case of uneven color in the surface due to the color, the color variation of the color patch in the color chart that was output in the past will be substituted in consideration of the change over time of the printer. By obtaining colorimetric values at the locations of the color patches in the color chart, it is possible to avoid increasing the workload and output cost by eliminating the repeated output of the color chart until no in-plane color unevenness occurs. There is an effect that a color value acquisition method can be provided.

Example 1
Embodiments of the present invention will be described below with reference to the drawings.
In this embodiment, when creating a device profile representing the output characteristics of a printer, color unevenness occurs due to the fact that the color material is not uniformly applied within the surface of the color patch in the color chart output from the printer. In this case, the color chart is not repeatedly output until the new in-plane color unevenness does not occur. Select the color chart that is output in the state closest to the output reproducibility of the printer, substitute the colorimetric value of the color patch in the color chart, and the color patch location in the chart where color unevenness occurs Therefore, it is possible to provide a colorimetric value acquisition method capable of avoiding an increase in work load and output cost.

FIG. 2 is a flowchart showing the configuration of the colorimetric value acquisition method according to the first embodiment of the present invention, and includes the following steps.
(1) A step of outputting a predetermined device profile creation color chart from the printer in order to create a device profile representing the output characteristics of the printer (step S201).
(2) A step of measuring a plurality of in-plane locations in each color patch with a measuring instrument in order to determine in-plane color unevenness existing in the color patches in the color chart output in the step (1) ( Step S202).
(3) Similarly, a step of capturing the color chart output in step (1) as an image with a scanner (step S203).
(4) From the in-plane difference of the colorimetric values in each color patch measured in the above step (2), a color patch having in-plane color unevenness in the color chart is determined. Alternatively, the color chart image captured by the scanner in the above step (3) is compared with the reference color chart image that is output when the device (output machine) is previously stabilized and captured by the scanner. A step of discriminating a color patch in which color unevenness is present (step S204, color unevenness discrimination means).
(5) Considering the output reproducibility of the current printer, the past printer output reproducibility was compared with the current printer output reproducibility, and output was performed in the past printer state closest to the current printer output reproducibility. A step of selecting a color chart (step S205).
(6) A step of obtaining colorimetric values of the color patch having in-plane color unevenness from the color chart selected in the step (5) (step S206).

  First, each color patch in the color chart output by the printer is measured by a measuring instrument. At that time, in order to obtain information for discriminating in-plane color unevenness in the color patch caused by the color material not being applied uniformly, as shown in FIG. To do. FIG. 1 is a schematic diagram for explaining measurement points of in-plane color unevenness in one color patch. In this embodiment, the case where five points in the plane are measured is shown.

  Next, a difference between the colorimetric values measured at a plurality of locations, for example, a color difference (ΔE * ab) based on one location measured at 5 locations, is calculated, and a threshold value (for example, ΔE *) is calculated as ΔE * ab. ab ≦ 1), and if the threshold value is exceeded, it is determined that the color patch has in-plane color unevenness, and a color patch of a color combination consisting of hundreds to thousands of CMYK or RGB multiplications is determined. From among them, a color patch having in-plane color unevenness is determined.

  Alternatively, the output color chart is captured as an RGB image by the scanner, and compared with the RGB image of the reference color chart that is output when the device (output machine) is stable and captured by the scanner in advance. A color patch having color unevenness is determined. As a comparison method, there is a method of calculating an absolute value of a difference between device values of each RGB channel between the RGB image of the color chart captured by the scanner and the RGB image of the reference color chart. The device value of each RGB channel indicates the gradation (0-255) of each RGB channel. For example, if the “absolute value of difference” of the calculation function of Photoshop (registered trademark) is used, it is possible to visually discriminate a color patch in which in-plane color unevenness occurs.

  In addition, the colorimetric values of the color patches that are determined to have in-plane color unevenness are obtained from the data group of the colorimetric values of the color chart measured in the past. Selects the color chart output in the state closest to the output reproducibility of the current printer, and obtains it from the color patches therein.

  As a method of obtaining the colorimetric values of the color patches in the past color chart that were output in the state closest to the output reproducibility of the current printer, the remaining colors excluding the color patches determined to be in-plane color unevenness Calculates the color difference between the color measurement value of the color patch in the color chart output by the current printer, which is a combination of patches, and the color measurement value of the corresponding color patch in the past color chart group, and the average color difference is the smallest The past color chart is judged to be the closest to the output reproducibility of the current printer, and the past color chart output in the state closest to the output reproducibility of the current printer is selected from the past color chart group. .

  A colorimetric value corresponding to the color patch in the current color chart determined to have in-plane color unevenness is obtained instead of the color patches in the past color chart selected above.

  As a result, when in-plane color unevenness occurs in the color patch in the color chart, the colorimetric value of the corresponding color patch in the past color chart output in the state closest to the current output condition is substituted. As a result, it is possible to obtain the colorimetric values of the color patches determined to have in-plane color unevenness without outputting the color chart again.

As described above, according to the present embodiment, when a device profile representing the output characteristics of the output device is created, the color material is not uniformly applied in the plane of the color chart output from the printer. If unevenness occurs, the color chart is not output until the unevenness in the surface no longer occurs. Use the color chart to obtain the colorimetric values of the color patches in the color chart where the in-plane color unevenness has occurred to eliminate the state in which the color chart is repeatedly output until the in-plane color unevenness does not occur. There is an effect that it is possible to provide a colorimetric value acquisition method capable of avoiding an increase in workload and output cost due to repeated output.
In addition, since the colorimetric values of the color chart output in the past are substituted and the colorimetric values of the color patches in the color chart in which in-plane color unevenness occurs are obtained, there is also an effect that the implementation is easy.

It is a schematic diagram for demonstrating the measurement location of the color nonuniformity in the surface in one color patch. It is a flowchart which shows the example of the process by embodiment of this invention.

Explanation of symbols

  1 …… Color patch location where color material is printed uniformly 2 …… Color patch location where in-plane color unevenness occurs 3 …… Measurement location

Claims (5)

A method for obtaining a colorimetric value of a location where color unevenness occurs in the surface of a printed matter output from an output machine,
A step of discriminating an in-plane color non-uniformity discriminating portion where a color non-uniformity occurs in the surface of the printed matter;
Selecting a colorimetric value of a printed matter output in a state closest to the color reproducibility of the current output device from a group of colorimetric values of the printed matter output in the past from the output device;
Substituting the selected colorimetric value, and obtaining as a colorimetric value of the location where it is determined that color unevenness has occurred by the color unevenness determining means;
A colorimetric value acquisition method characterized by comprising:   The step of selecting the colorimetric value includes selecting a colorimetric value when the color difference between the colorimetric value of the printed matter currently output and the color difference is minimized from the group of colorimetric values of the printed matter output in the past. The colorimetric value acquisition method according to claim 1, wherein:   The printed matter is a color chart including a plurality of color patches, and the color unevenness determination means in the surface measures one location in the colorimetric values measured at a plurality of locations within the color patch surface to be measured by a measuring instrument. Calculate the color difference (ΔE * ab) based on the color value, set a threshold value for ΔE * ab, and if the threshold value is exceeded, in-plane color unevenness exists, and in-plane color unevenness exists The colorimetric value acquisition method according to claim 1, wherein the printed matter to be determined is discriminated.   The printed matter is a color chart having a plurality of color patches, and the in-plane color unevenness determination means is an RGB image of the printed matter taken in by the scanner, and is output when the output machine is stabilized in advance and taken into the scanner. 2. The colorimetric value acquisition method according to claim 1, wherein an RGB image of the reference color chart is calculated by a calculation function so that a color patch in which in-plane color unevenness occurs can be visually identified.   The calculation function is the absolute value of the difference in device values of each RGB channel between the RGB image of the printed material captured by the scanner and the RGB image of the reference color chart that is output when the output machine is previously stabilized and captured by the scanner. 2. The color unevenness determination unit, which calculates a value, makes it possible to visually determine a color patch in which in-plane color unevenness occurs based on the calculation result. Colorimetric value acquisition method.

Images