JP2005229521A - Color image processor, color image forming device, color image processing method, computer program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve non-compatibility/corruption in gradation for a color due to difference of image formation medium, and to prevent deterioration in image quality. <P>SOLUTION: A plurality of color patches established beforehand are outputted to an arbitrary form for creating a printer profile (S1). A color of the plurality of color patches is measured by a colorimetry device 5 (S2). Data used as a reference for determination of characteristics are extracted from a data portion, and it is determined (S3). On this occasion, the data as the reference for the determination of characteristics are taken out from the data portion, and a Lab distance in a same CMYK density value is computed (S4). After Lab distance computation, comparison, for example, between a plain paper and a glossy paper is conducted at the data portion, and characteristics is determined for a medium. After characteristics determination, a lattice point value in the printer profile used as a reference is computed (step S5), and a reference lattice point value in the profile serving as a reference for various media is determined based on the medium reference lattice point value (step S9). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color image processing apparatus for generating a printer profile, an image forming apparatus including the color processing apparatus, a color image processing method for generating a printer profile, a computer program for realizing the generation of the printer profile by a computer, And a recording medium on which the program is recorded.

  In general, when outputting an image displayed on a monitor from a printer, it is difficult to make the two colors correspond to each other because the display spaces of the two are different. Therefore, color conversion and color correction image processing is performed so that the display image on the monitor and the appearance of the print image on the printer are close to each other. 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, when the same image processing is performed, unnatural color correction occurs.

Therefore, in the invention described in Patent Document 1, after obtaining a color reproduction range for each image forming medium during image processing, color correction processing for calculating a gray axis and creating a color look-up table (CLUT) is performed. ing. In particular, during color correction, the color reproduction range of the image forming medium is reduced by reducing the difference between the image forming media in the low density area to the medium density area and increasing the difference between the image forming media in the medium density area to the high density area. The process which uses effectively is performed. As related techniques, the inventions described in Patent Documents 2 and 3 below are also known.
JP 2002-118762 A JP 2001-157066 A JP 2000-004369 A

  However, since the invention described in Patent Document 1 is based on only one gray axis, there is a possibility that color compatibility / gradation may be lost depending on various image forming media.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to improve color incompatibility and gradation deterioration due to differences in image forming media, and to prevent image quality deterioration.

  In order to achieve the above object, the first means is an image processing apparatus for creating a printer profile, which uses the measured values of the color chart and determines the image of any image forming medium based on information of two reference image forming media. Means for determining the type, means for calculating a grid point value of a printer profile serving as a reference of the arbitrary image forming medium from grid point values constituting two printer profiles serving as a reference, and the arbitrary image forming medium Means for calculating a grid point value of a printer profile suitable for the printing conditions.

  The second means is that in the first means, the information of the two reference image forming media is information on an image forming medium having a narrow color reproduction range and information on an image forming medium having a wide color reproduction range. It is characterized by that.

  The third means is characterized in that, in the first or second means, the determination by the determination means is performed based on a distance based on a Lab value ΔE76 and a distance based on ΔE94.

  According to a fourth means, in the first means, the lattice point values of the image forming medium having a narrow color gamut and the image having the wide color gamut as the lattice point values constituting the two printer profiles serving as the reference. The grid point value of the forming medium is used.

  According to a fifth means, in the first means, the means for calculating the lattice point value of the printer profile adapted to the printing condition of the arbitrary image forming medium is a grid of the printer profile which is a reference of the arbitrary image forming medium. It is calculated using a point value.

  The sixth means calculates the grid point value according to the low density part, the middle density part, and the high density part when calculating the grid point value in any of the first, fourth, or fifth means. It is characterized by performing.

  The seventh means is a color image processing apparatus according to any one of the first to sixth means, and an image for visualizing and outputting an image on an image forming medium in accordance with a printer profile created by the color image processing apparatus. A color image forming apparatus is constituted by the output means.

  According to an eighth means, in a color image processing method for creating a printer profile, a first step of outputting a preset color patch for an arbitrary image forming medium for creating a printer profile, and a first step The Lab distance at the same CMYK density value based on the second step of measuring the color of the output color patch, the measured value of the color patch measured in the second step, and the data used as a criterion for characteristic determination A third step of calculating the image, a fourth step of determining the characteristics of an arbitrary image forming medium based on the Lab distance calculated in the third step, and an arbitrary of the characteristics determined in the fourth step A fifth step of calculating a printer profile grid point value for the image forming medium, and a sixth step of creating a printer profile based on the grid point calculated in the fifth step; Including wherein the are at.

  A ninth means is characterized in that, in the eighth means, when calculating the Lab distance in the third step, the ΔE76 distance based on the CIE1976 Lab color difference formula and the ΔE94 distance based on the CIE1994 color difference formula are used. .

  A tenth means is the eighth means, characterized in that the calculation of the lattice points in the fifth step is performed separately for the low density part, the medium density part and the high density part.

An eleventh means is a computer program for creating a printer profile by an image processing apparatus, wherein a first procedure for outputting a preset color patch for an arbitrary image forming medium for creating a printer profile; The Lab procedure calculates the Lab distance at the same CMYK density value based on the second procedure for measuring the color of the color patch, the measurement result of the color patch measured in the second procedure, and the data used as the criterion for characteristic determination. 3 steps,
A fourth procedure for determining the characteristics of an arbitrary image forming medium based on the Lab distance calculated in the third procedure, and a grid point of the printer profile for the arbitrary image forming medium whose characteristics are determined in the fourth procedure It includes a fifth procedure for calculating a value and a sixth procedure for creating a printer profile based on the lattice points calculated in the fifth procedure.

  A twelfth means is characterized in that the computer program according to the eleventh means is read by a computer and recorded on a recording medium so as to be executable.

  In the following embodiment, the means for determining the type of any image forming medium based on the information of the two reference image forming media configures the two printer profiles serving as the reference in the CPU 7 of the server 2. A means for calculating a grid point value of a printer profile serving as a reference for the arbitrary image forming medium from a grid point value and a means for calculating a grid point value of a printer profile suitable for the printing conditions of the arbitrary image forming medium are servers. Correspond to the two arithmetic units 8 respectively.

  According to the present invention, 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 due to the difference in the image forming medium Can be improved.

  Further, according to the present invention, it is possible to prevent deterioration in quality by calculating lattice point values suitable for various printing conditions from lattice point values serving as a reference for an arbitrary image forming medium.

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

  FIG. 1 is a block diagram showing 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 the colors of patches on a color chart, and a client that interfaces with a printer 6 ( PC) 2. The server 2 includes a CPU 7, a calculation 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 is interpreted by the printer 6 based on the printer profile generated by the image processing apparatus 1. Data is converted into a possible format and sent to the printer 6. The CPUs of the server 2 and the client 3 each have 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. 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 are not characteristic, a detailed description thereof will be omitted.

  2 and 3 are flowcharts showing the processing procedure of the image processing apparatus according to the present embodiment. The flowchart of FIG. 2 shows the procedure for calculating the grid point value of the printer profile as a reference for an arbitrary medium, and the flowchart of FIG. 3 shows the procedure for calculating the grid point value of the printer profile suitable for the printing conditions of the arbitrary medium Show.

  In the process shown in FIG. 2, a color chart in which a plurality of color patches set in advance for an arbitrary image forming medium for creating a printer profile from the printer 6 is formed on the image forming medium (paper) is output ( Step S1). The color data constituting the color patch is obtained by dividing 0% to 100% of the CMYK density value by an arbitrary step size, and uses single color data of CMYK and mixed color data by a combination of CMYK. The output color patch is measured by the measuring instrument 5 (step S2). Measurement data measured by the colorimeter 5 is transmitted to the server 2. Note that the measuring instrument 5 itself for measuring the color patch is generally used and well-known, and a description thereof will be omitted.

  The server 2 uses the measurement data to determine the characteristics of the image forming medium by extracting data from the data section 9 as a criterion for determining characteristics (step S3). At this time, the calculation unit 8 extracts data serving as a characteristic determination reference from the data unit 9 and calculates the Lab distance at the same CMYK density value (step S4). When calculating the Lab distance, the ΔE76 distance based on the CIE1976 Lab color difference formula and the ΔE94 distance based on the CIE1994 color difference formula are used. Since the calculation of these distances is also generally performed, details are omitted. After calculating the Lab distance, the data of the reference medium 1 in the data section 9 (for example, plain paper) is compared with the data of the reference medium 2 (for example, glossy paper) to determine the characteristics of the medium.

After the medium determination, the grid point value of the reference 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 calculation of the grid point value is
R ′ = α1 × n × (X11 × R1 + X12 × G1 + X13 × B1) + α2 × (1-n) × (Y11 × R2 + Y12 × G2 + Y13 × B2)
G ′ = β1 × n × (X21 × R1 + X22 × G1 + X23 × B1) + β2 × (1-n) × (Y21 × R2 + Y22 × G2 + Y23 × B2)
B ′ = γ1 × n × (X31 × R1 + X32 × G1 + X33 × B1) + γ2 × (1-n) × (Y31 × R2 + Y32 × G2 + Y33 × B2)
Is required. However,
R *, G *, B *: Lattice point values of the reference media 1 and 2 Coefficients X **, Y **: Conversion coefficients for the reference media 1 and 2 taken out from the data section 9 at the time of characteristic determination α * (coefficient related to R ′ ), Β * (coefficient relating to G ′), γ * (coefficient relating to B ′): coefficients for the reference media 1 and 2 that change in accordance with highlight, middle, and shadow n: coefficients obtained when determining the medium characteristics (arbitrary (The ratio of the distance between the medium and the reference medium 1, the arbitrary medium and the reference medium 2, and 0 ≦ n ≦ 1)
Coefficients α *, β *, γ *: Coefficients obtained by determining the characteristics of the media, ΔE76 distance only, ΔE94 distance only, or a combination of ΔE76 and ΔE94 After determining the coefficients, for each of the low density part, medium density part, and high density part The lattice point value is calculated, and the lattice point value of the printer profile serving as a reference for various media is determined (step S9).

  It should be noted that only the ΔE76 distance in a portion where the color change of the appearance is small (for example, highlight) depending on the medium, and the ΔE94 distance is easily affected by the change (for example, the middle) in a portion where the color change of the appearance is large (eg, shadow). ), The ΔE76 distance and the ΔE94 distance are used to calculate the coefficients α *, β *, and γ *.

  In the process shown in FIG. 3, the printing condition (for example, toner / ink amount restrained printing) is adapted from the data portion 9 based on the grid point values of the printer profile serving as a reference for various media obtained in step S9. A coefficient is extracted (step S10). After extracting the coefficients, the grid point values are calculated separately for the low density part, medium density part, and high density part.

The calculation of the grid point value is
R ″ = n × (W11 × R ′ + W12 × G ′ + W13 × B ′) + (1-n) × (Z11 × R ′ + Z12 × G ′ + Z13 × B ′)
G ″ = n × (W21 × R ′ + W22 × G ′ + W23 × B ′) + (1-n) × (Z21 × R ′ + Z22 × G ′ + Z23 × B ′)
B ″ = n × (W31 × R ′ + W32 × G ′ + W33 × B ′) + (1-n) × (Z31 × R ′ + Z32 × G ′ + Z33 × B ′)
Is required. However,
R ′, G ′, B ′: Reference lattice point values of various media calculated in FIG. 2 Coefficients W **, Z **: For the reference media 1 and 2 extracted from the data section 9 according to the printing conditions Conversion coefficient. Specifically, when the printing condition is toner / ink amount suppression printing, positive decimal values of 1 or less are applied to the coefficients W ** and Z ** in order to consider the load on the medium during printing. Is done.

  After the coefficients are determined, lattice point values are calculated for each of the low density portion, medium density portion, and high density portion (steps S11, 12, and 13), and the printer profile lattice point values that match the printing conditions of various media are determined. (Step S14). After calculating the lattice point value, a printer profile for the printer 6 is created in the server 2 (step S15), and the printer profile is transmitted to the printer driver 12 in the client 3.

  As described above, according to the present embodiment, the following effects can be obtained.

  The server 2 uses the color chart measurement values to determine the type of any image forming medium based on the information of the two reference image forming media, and from the lattice point values constituting the two reference printer profiles. Since the grid point value of the printer profile serving as the reference for an arbitrary medium is calculated and the grid point value of the printer profile of an arbitrary image forming medium medium that matches the printing conditions of the arbitrary image forming medium is calculated, the difference between the media And color incompatibility and gradation deterioration due to differences in printing conditions can be improved.

  In addition, information on a medium (for example, plain paper) having a narrow color gamut (gamut) and a medium (for example, a medium having a wide color gamut) (Glossy paper) information is used, so fine medium determination can be performed.

  Since the distance based on the Lab value ΔE76 and the distance based on ΔE94 are used to determine the type of an arbitrary image forming medium, it is possible to capture physical characteristics and characteristics based on human perception during the determination process.

  A medium (for example, plain paper) having a narrow color reproduction area (gamut) on a medium having a lattice point value of a printer profile as a reference when calculating a lattice point value of a printer profile serving as a reference of an arbitrary image forming medium Since the lattice point value and the lattice point value of a medium (for example, glossy paper) having a wide color gamut are used, fine lattice point value calculation processing can be performed.

  When calculating the grid point value of the printer profile that is the reference for any image forming medium, the grid point value is calculated according to the low density part (highlight), medium density part (middle), and high density part (shadow part). Therefore, it is possible to improve the gradation deterioration.

  When calculating the grid point value of a printer profile that matches the printing conditions of an arbitrary image forming medium (for example, toner / ink amount suppression printing), the grid point value of the printer profile that serves as a reference for the arbitrary image forming medium is used. Further, it is possible to calculate the lattice point value suitable for the printing conditions while maintaining the characteristics of the image forming medium.

  When calculating the grid point values of the printer profile according to the printing conditions of any image forming medium, the grid point values are calculated according to the low density part, medium density part, and high density part. The grid point value of the adapted printer profile can be calculated.

1 is a block diagram illustrating a schematic configuration of an image processing apparatus according to an embodiment of the present invention. 5 is a flowchart showing a processing procedure of the image processing apparatus according to the present embodiment, and shows a procedure for calculating a lattice point value of a printer profile serving as a reference for an arbitrary image forming medium. 5 is a flowchart showing a processing procedure of the image processing apparatus according to the present embodiment, and shows a procedure for calculating lattice point values of a printer profile suitable for printing conditions of an arbitrary image forming medium.

Explanation of symbols

1 Image processing device 2 Server 3 Client (PC)
4 Monitor 5 Measuring instrument 6 Printer 7, 11 CPU
8 Calculation section 9 Data section 10 Data processing section 12 Printer driver

Claims (12)

In an image processing apparatus for creating a printer profile,
Means for determining the type of an arbitrary image forming medium based on information of two reference image forming media using the measurement values of the color chart;
Means for calculating a lattice point value of a printer profile serving as a reference of the arbitrary image forming medium from lattice point values constituting two reference printer profiles;
Means for calculating a grid point value of a printer profile adapted to the printing conditions of the arbitrary image forming medium;
A color image processing apparatus comprising:   2. The color image according to claim 1, wherein the information on the two reference image forming media is information on an image forming medium having a narrow color gamut and information on an image forming medium having a wide color gamut. Processing equipment.   The color image processing apparatus according to claim 1, wherein the determination by the determination unit is performed based on a distance based on a Lab value ΔE76 and a distance based on ΔE94.   The grid point values of the image forming medium having a narrow color reproduction range and the grid point values of the image forming medium having a wide color reproduction range are used as the grid point values constituting the two printer profiles serving as the reference. The color image processing apparatus according to claim 1.   The means for calculating the lattice point value of the printer profile that matches the printing condition of the arbitrary image forming medium is calculated using the lattice point value of the printer profile that is a reference of the arbitrary image forming medium. The color image processing apparatus according to claim 1.   The grid point value is calculated according to the low density part, the medium density part, and the high density part when calculating the grid point value. Color image processing device. A color image processing apparatus according to any one of claims 1 to 6;
Image output means for visualizing and outputting an image on an image forming medium in accordance with a printer profile created by the color image processing apparatus;
A color image forming apparatus comprising: In a color image processing method for creating a printer profile,
A first step of outputting a preset color patch for 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 the Lab distance at the same CMYK density value based on the measurement value of the color patch measured in the second step and the data used as a reference for the characteristic determination;
A fourth step of determining characteristics 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 the printer profile for any image forming medium whose characteristics are determined in the fourth step;
A sixth step of creating a printer profile based on the lattice points calculated in the fifth step;
A color image processing method comprising: 9. The color image processing method according to claim 8, wherein when calculating the Lab distance in the third step, a ΔE76 distance based on the CIE1976 Lab color difference formula and a ΔE94 distance based on the CIE1994 color difference formula are used. 9. The color 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 apparatus,
A first procedure for outputting a preset color patch for 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 the Lab distance at the same CMYK density value based on the measurement result of the color patch measured in the second procedure and the data used as the reference for the 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 the printer profile for an arbitrary image forming medium whose characteristics are determined in the fourth procedure;
A sixth procedure for creating a printer profile based on the grid points calculated in the fifth procedure;
The computer program characterized by including. 12. A recording medium on which the computer program according to claim 11 is recorded by being read and executable by a computer.

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