JP2004229116A - Image processing apparatus, image forming apparatus, image processing method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the corruption of non-compatibility / gradation of colors due to differences in image forming media, by computing lattice point values of a printer profile of any image forming medium, based on lattice point values of a printer profile of a base image forming medium. <P>SOLUTION: A color patch established beforehand is outputted to an arbitrary image forming medium for generating a printer profile (S1). The color of the color patch is measured (S2). Based on reference data for characteristics determination, a Lab distance in an identical CMYK density value is computed (S3). The characteristics of the image forming medium are determined based on the measurement result of the measured color patch (S4). Lattice point values of the printer profile are computed for the image forming medium determined by S4 (S5), Moreover, the printer profile is generated based on the computed lattice points (S9). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color image processing method for generating a printer profile, a color image processing apparatus for performing the color image processing method, an image forming apparatus including the color processing apparatus, and a color image processing method for generating the printer profile. And a program for implementing the program on a computer.
[0002]
[Prior art]
Generally, when an image displayed on a monitor is output from a printer, it is difficult to make the expression colors of the two correspond one-to-one because the display spaces of the two are different. Therefore, image processing of color conversion and color correction is performed so that the display image on the monitor and the print image on the printer look closer. At this time, even if the image signal of the monitor and the color material (toner, ink) of the printer are the same, if the image forming medium (paper type) used for the printer output is different, the color reproduction range (gamut) for each image forming medium Therefore, if the same image processing is performed, unnatural color correction occurs.
[0003]
Therefore, according to the invention described in Japanese Patent Application Laid-Open No. H11-163, after acquiring a color reproduction range for each image forming medium at the time of image processing, color correction processing for calculating a gray axis and creating a color look-up table (CLUT: Color Look Up Table) is performed. ing. In particular, at the time of color correction, the difference between the image forming media is small in the low density portion to the medium density portion, and the difference between the image forming media is large in the medium density portion to the high density portion, so that the color reproduction range of the image forming medium is improved. Is performed effectively. As related techniques, the inventions described in Patent Documents 2 and 3 below are also known.
[0004]
[Patent Document 1]
JP-A-2002-118762
[Patent Document 2]
JP 2001-157066 A
[Patent Document 3]
JP 2000-004369 A
[Problems to be solved by the invention]
However, in the invention described in Patent Document 1, since only one gray axis is used as a reference, color compatibility and gradation may be lost depending on various image forming media.
[0008]
Accordingly, an object of the present invention is to calculate a grid point value of a printer profile of an arbitrary image forming medium based on a grid point value of a printer profile of a reference image forming medium, thereby obtaining a color based on a difference between image forming media. Incompatibility and collapse of gradation.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a first means is that, in an image processing apparatus for creating a printer profile, an arbitrary image forming medium based on information of one image forming medium serving as a reference using a measured value of a color chart. It is characterized by comprising means for determining characteristics and means for calculating grid point values of a printer profile of an arbitrary image forming medium from grid point values forming one reference printer profile.
[0010]
According to a second aspect, in the first aspect, the reference one image forming medium is an image forming medium having a narrow color reproduction range.
[0011]
According to a third aspect, in the second aspect, the determination of the characteristic of the arbitrary image forming medium is performed based on a distance based on the Lab value ΔE76 and a distance based on the ΔE94.
[0012]
According to a fourth aspect, in the first aspect, the image forming medium used as a reference when calculating the grid point value is an image forming medium having a narrow color reproduction range.
[0013]
A fifth means is that, in the fourth means, when calculating the grid point value, the grid point value is calculated for each of the low density part, the medium density part, and the high density part.
[0014]
A sixth means is the fifth means, wherein an input value and an output value of the grid point value are in an RGB color system.
[0015]
The seventh means comprises an image forming apparatus comprising the image processing apparatus according to the first to sixth means, and an image output means for visualizing and outputting an image according to a printer profile created by the image processing apparatus. It is characterized by the following.
[0016]
Eighth means includes, in an image processing method for creating a printer profile, a first step of outputting a preset color patch to an arbitrary image forming medium for which a printer profile is created, and an output in the first step. A second step of measuring the color of the color patch, and a Lab distance at the same CMYK density value based on the measured value of the color patch measured in the second step and data serving as a criterion for determining characteristics. A third step of calculating, a fourth step of determining a characteristic of an arbitrary image forming medium based on the Lab distance calculated in the third step, and an arbitrary image forming medium determined in the fourth step A fifth step of calculating a grid point value of the printer profile for the second step, and a sixth step of creating a printer profile based on the grid points calculated in the fifth step. And wherein the door.
[0017]
The ninth means is characterized in that, in the eighth means, when calculating the Lab distance in the fourth step, the ΔE76 distance based on the CIE1976 Lab color difference equation and the ΔE94 distance based on the CIE1994 color difference equation are used.
[0018]
According to a tenth aspect, in the eighth aspect, the calculation of the grid points in the fifth step is performed separately for a low density portion, a medium density portion, and a high density portion.
[0019]
An eleventh means, in a computer program for creating a printer profile by an image processing apparatus, a first procedure of outputting a preset color patch to an arbitrary image forming medium for creating a printer profile; A second procedure for measuring the color of the color patch, a third procedure for calculating a Lab distance at the same CMYK density value based on the measured result of the color patch and data serving as a criterion for characteristic determination; A fourth procedure for determining a characteristic of an arbitrary image forming medium based on the calculated Lab distance, and a fifth procedure for calculating a grid point value of a printer profile for the image forming medium whose characteristic has been determined in the fourth procedure. It is characterized by including a procedure and a sixth procedure for creating a printer profile based on the calculated grid points.
[0020]
According to the first and eighth means, it is possible to improve incompatibility of colors and collapse of gradation due to differences in image forming media.
[0021]
According to the second means, the information of an image forming medium having a narrow color reproduction range (gamut), for example, information of plain paper is used as the reference image forming medium for determining the characteristics of an arbitrary image forming medium. Therefore, it is possible to limit the processing to only the expansion processing for a wide color reproduction range.
[0022]
According to the third and ninth means, the distance based on the Lab value ΔE76 and the distance based on ΔE94 are used as means for determining the characteristics of an arbitrary image forming medium. It is possible to capture characteristics based on human perception.
[0023]
According to the fourth means, an image having a narrow color reproduction range (gamut) is used as an image forming medium having a grid point value of a printer profile as a reference when calculating a grid point value of the printer profile of an arbitrary image forming medium. By using the grid point values of the forming medium, for example, plain paper, it is possible to limit the processing to only the expansion processing to a wide color gamut.
[0024]
According to the fifth and tenth means, when calculating a grid point value of a printer profile of an arbitrary image forming medium, a low density part (highlight), a medium density part (middle), and a high density part (shadow part) , The grid point value is calculated in accordance with, so that it is possible to improve the collapse of the gradation.
[0025]
According to the sixth means, the input values and the output values are set to the RGB color system as the grid point values of the printer profile of an arbitrary image forming medium or a reference image forming medium. It can be the same between different image forming media.
[0026]
According to the seventh means, the image is visualized and output according to the printer profile created by the image processing apparatus, so that it is possible to generate an image suitable for the image forming medium.
[0027]
According to the eleventh means, it is possible to create a printer profile according to the image forming medium only by downloading the image to a computer, thereby improving the color incompatibility and the collapse of gradation due to the difference in the image forming medium. can do.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
FIG. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to an embodiment of the present invention. In FIG. 1, an image processing apparatus 1 includes a server 2 that performs arithmetic processing, a monitor 4 that performs various displays, a measuring device 5 that colors a patch color on a color chart, and a client that interfaces with a printer 6. PC) 2. The server 2 includes a CPU 7, an arithmetic unit 8, a data unit 9, and a data processing unit 10, and the client 3 includes a CPU 11 and a printer driver 12. The printer driver 12 receives input color data (for example, data expressed in the RGB color system) from an application on the image processing apparatus 1, and interprets the printer 6 based on a printer profile generated by the image processing apparatus 1. The data is converted into a possible format and transmitted to the printer 6. The CPUs of the server 2 and the client 3 each include a ROM and a RAM, and perform necessary control by executing a program stored in the ROM while using the RAM as a work area. Note that an image forming apparatus is formed by the image processing apparatus 1 and the printer 6. The printer 6 itself may be any printer having a known image forming function such as an electrophotographic system, an ink jet system, or a thermal transfer system. Since these printers themselves do not have characteristics, detailed description thereof will be omitted.
[0030]
FIG. 2 is a flowchart illustrating a processing procedure of the image processing apparatus according to the present embodiment. In this process, the printer 6 outputs a color chart in which a plurality of preset color patches are formed on an image forming medium (paper) for an arbitrary image forming medium for creating a printer profile (step S1). The color data constituting the color patch is obtained by dividing the CMYK density value from 0% to 100% by an arbitrary step width, and uses single color data of each of CMYK and data of mixed colors by a combination of CMYK. Next, the color of the color patch output from the printer 6 is measured by the measuring device 5 (step S2). The measurement data measured by the measuring device 5 is transmitted to the server 2. Since the measuring device 5 itself for measuring the color patch is generally used and publicly known, the description is omitted.
[0031]
The server 2 uses the measured data to determine the characteristics of the image forming medium by extracting data serving as a reference for determining the characteristics from the data unit 9. At this time, the calculation unit 8 extracts data serving as a criterion for characteristic determination from the data unit 9 and calculates a Lab distance at the same CMYK density value (step S3). When calculating the Lab distance, a ΔE76 distance based on the CIE1976 Lab color difference equation and a ΔE94 distance based on the CIE1994 color difference equation are used. Note that the calculation of these distances is also generally performed, and thus the details are omitted.
[0032]
After calculating the Lab distance, a comparison is made between a threshold value of an arbitrary image forming medium in the data section 9 and a threshold value with respect to a reference medium (for example, plain paper) to determine the characteristics of the image forming medium (step S4). Next, a grid point value of the printer profile is calculated (step S5). The calculation of the grid point value is performed by dividing the processing into a low density part (highlight-step S6), a medium density part (middle-step S7), and a high density part (shadow-step S8). The grid point value is
R ′ = α (A11 × R + A12 × G + A13 × B)
G ′ = β (A21 × R + A22 × G + A23 × B)
B ′ = γ (A31 × R + A32 × G + A33 × B)
Required by However,
R, G, B: grid point value coefficients of the reference medium A **: conversion coefficients α (coefficients related to R ′), β (coefficients related to G ′), γ (coefficients related to B ′) extracted from the data 9 at the time of characteristic determination: This coefficient changes according to highlight, middle, and shadow.
[0033]
The coefficients α, β, and γ are coefficients obtained by combining ΔE76 and ΔE94 only for the ΔE76 distance and only for the ΔE94 distance after determining the characteristics of the medium. Specifically, only the ΔE76 distance is affected by the variation in the portion where the apparent color change is small (eg, highlight) depending on the image forming medium, and the ΔE94 distance is affected by the variation in the portion where the apparent color change is large (eg, shadow). In the easy part (for example, middle), the ΔE76 distance and the ΔE94 distance are used for calculating the coefficient.
[0034]
After calculating the grid point values, a printer profile for the printer 6 is created in the server 2 (step S9), and the printer profile is transmitted to the printer driver 12 in the client 3.
[0035]
In this way, by determining the characteristics of an arbitrary image forming medium from the reference image forming medium and calculating the grid point value of the printer profile of the arbitrary image forming medium, the non- It is possible to improve compatibility and gradation.
[0036]
As a reference image forming medium, information of an image forming medium having a narrow color reproduction range (gamut), for example, information of plain paper is used. By using an image forming medium having a narrow color gamut as a reference medium in this way, it is possible to limit the processing to only an expansion process to a wide color gamut. Examples of the image forming medium having a wide color reproduction area include glossy paper and coated paper, and these image forming media are generally selected or recommended according to the type of image.
[0037]
These processes are performed by the server 2 of the image processing apparatus 1.
[0038]
【The invention's effect】
As described above, according to the present invention, the difference between the image forming media is calculated by calculating the grid point value of the printer profile of an arbitrary image forming medium based on the grid point value of the printer profile of the reference image forming medium. , Color incompatibility / gradation loss.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a processing procedure of the image processing apparatus according to the embodiment of the present invention.
[Explanation of symbols]
1 image processing apparatus 2 server 3 client 4 monitor 5 measuring instrument 6 printer 7, 11 CPU
8 arithmetic unit 9 data unit 10 data processing unit 12 printer driver

Claims (11)

In an image processing apparatus for creating a printer profile,
Means for determining a characteristic of an arbitrary image forming medium based on information of one reference image forming medium using a measured value of a color chart;
Means for calculating a grid point value of a printer profile of an arbitrary image forming medium from grid point values forming one reference printer profile;
An image processing apparatus comprising: 2. The image processing apparatus according to claim 1, wherein the reference one image forming medium is an image forming medium having a narrow color reproduction range. 3. The image processing apparatus according to claim 2, wherein the determination of the characteristic of the arbitrary image forming medium is performed based on a distance based on a Lab value ΔE76 and a distance based on a ΔE94. 2. The image processing apparatus according to claim 1, wherein the image forming medium used as a reference when calculating the grid point value is an image forming medium having a narrow color gamut. The image processing apparatus according to claim 4, wherein when calculating the grid point value, the grid point value is calculated for each of a low density part, a medium density part, and a high density part. The image processing apparatus according to claim 5, wherein the input value and the output value of the grid point value are in an RGB color system. An image processing apparatus according to claim 1, and an image output unit configured to visualize and output an image according to a printer profile created by the image processing apparatus.
An image forming apparatus comprising: In an image processing method for creating a printer profile,
A first step of outputting a preset color patch to an arbitrary image forming medium for creating a printer profile;
A second step of measuring the color of the color patch output in the first step;
A third step of calculating a Lab distance at the same CMYK density value based on the measured value of the color patch measured in the second step and data serving as a criterion for determining characteristics;
A fourth step of determining a characteristic of an arbitrary image forming medium based on the Lab distance calculated in the third step;
A fifth step of calculating a grid point value of a printer profile for any image forming medium whose characteristics have been determined in the fourth step;
A sixth step of creating a printer profile based on the grid points calculated in the fifth step;
An image processing method comprising: 9. The image processing method according to claim 8, wherein in calculating the Lab distance in the third step, a ΔE76 distance based on a CIE1976 Lab color difference equation and a ΔE94 distance based on a CIE1994 color difference equation are used. 9. The image processing method according to claim 8, wherein the calculation of the grid points in the fifth step is performed separately for a low density part, a medium density part, and a high density part. In a computer program for creating a printer profile with an image processing device,
A first procedure of outputting a preset color patch to an arbitrary image forming medium for creating a printer profile;
A second procedure for measuring the color of the color patch;
A third procedure of calculating a Lab distance at the same CMYK density value based on the measurement result of the color patch measured in the second procedure and data serving as a criterion for characteristic determination;
A fourth procedure for determining characteristics of an arbitrary image forming medium based on the Lab distance calculated in the third procedure;
A fifth procedure for calculating a grid point value of a printer profile for an arbitrary image forming medium whose characteristics have been determined in the fourth procedure;
A sixth procedure for creating a printer profile based on the grid points calculated in the fifth procedure,
A computer program characterized by comprising:

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