JPH11155076A - Color converting method, color converting table preparing device, color converting device and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color converting table preparing device with which a user can be satisfied when outputting an image on a color display through a color printer. SOLUTION: Basic primary colors are displayed on a color display 100. A color chart output means 7 outputs a color chart 102 expressing the color reproduction area of a color printer 101, and a color patch number input means 2 makes correspondent a color patch which the user feels closest to each basic primary color in the color chart 102. A color classifying means 8 classifies colors into three kinds of basic primary color signal C1, gray signal C3 and other color signal C4. A Gamut (color reproduction area) transformation preparing means 4 prepares Gamut transformation from the combination of basic primary colors and color patches made correspondent by the user. A Gamut transforming means 5 performs the Gamut transformation to the color signal C4. Concerning the Gamut transformed color, the quantity of correspondent ink is calculated by a correspondent ink quantity determining means 6 and described in a color conversion look-up table(LOT) 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color printer for converting a color image containing a large amount of highly saturated colors such as computer graphics (CG) displayed on a color display between a color display and a color printer. A color conversion method for outputting, a color conversion table creating device for creating a color conversion table used at this time,
The present invention relates to a color conversion device and a recording medium storing a program for causing a computer to function each unit of the device.

[0002]

2. Description of the Related Art As a color conversion method of a printer, there has been previously a method of color conversion.
Although color conversion from RGB values to color ink amounts using color masking has been performed, recently, inexpensive memories are generally used as LUTs (Look Up Tables, Look Up Tables) ( References: Joji Tajima:
"Color Image Replication Theory", Maruzen Co., Ltd., 1996. ). In the color conversion method using the LUT, a color ink amount corresponding to each RGB value of the display is calculated in advance and written in the LUT. In the actual color conversion using the LUT, the color conversion is completed by using the input RGB values as addresses and reading out the corresponding ink amount. However, when creating the LUT, when to describing the color ink amounts for RGB full-color (2 ²⁴ colors), large memory is required. Therefore, the color ink amount is described only for the representative color RGB values in the LUT, and the ink amounts of the remaining colors are calculated using the interpolation method.

[0003] LU for color conversion between display and printer
When creating T, there is a problem that the color gamut (referred to as Gamut) of each device is different. Generally, when the display Gamut is compared with the printer Gamut, the display Gamut is large. In other words, in order for all colors on the display to be able to be represented by the printer, colors outside the printer Gamut must be
The process of pushing into t or sticking to the surface, ie,
Gamut conversion is required.

Various methods have been proposed for Gamut conversion.

FIG. 1 illustrates a general Gamut conversion method. The squares in the figure represent the color gamut of a standard display in a certain color space, and the shaded area inside thereof represents the color gamut of the printer in the same color space. The Gamut conversion processing performed by the arrows with the numbers in parentheses in FIG. 1 is as follows.

[Gamut Conversion] (1) The display Gamut is rotated so that the gray axis direction vector of the display Gamut matches the gray axis direction vector of the printer Gamut.

(2) Linearly compress the display Gamut.

(3) The display Gamut is translated so that the black point of the display coincides with the black point of the printer.

(4) The remaining color outside the printer Gamut is pasted on the surface of the printer Gamut.

When the processes from (1) to (3) in FIG. 1 are performed in the XYZ color system, the expression is as follows.

[0011]

(Equation 1) Here, (X, Y, Z) is XYZ before Gamut conversion.
Value, (X ', Y', Z ') is XYZ after Gamut conversion
Value, R is a 3 × 3 rotation matrix for performing the rotation of (1), s
f is the compression coefficient of (2). Also, (X _bk , Y _bk , Z
_bk ) is the XYZ value of printer black.

In the Gamut conversion process, the processes (1) and (3) for matching achromatic components are conversions uniquely determined when a printer Gamut and a display Gamut are given. On the other hand, in (2),
Determining how much the display Gamut should be compressed improves the color reproducibility for each input image, but calculating the optimal Gamut transform for each input image is not realistic in view of the processing time. Therefore, it can be dealt with by previously calculating the sum of color differences before and after Gamut conversion for a plurality of colors uniformly distributed in the uniform color space from the display Gamut, and setting the compression rate that minimizes the sum to the optimum compression coefficient.

Regarding the pasting process (4), there is no optimal solution, and at present it depends on know-how in color conversion. FIG. 2 shows a typical pasting process in the L ^* a ^* b ^* space.

[Paste processing] For the color X1, the hue and the brightness are fixed, and the color is pasted in the direction of low saturation. However, pasting beyond the L axis is not performed.

2. When the pasting process of 1 above fails as in the case of the colors X2 and X3, the hue is kept constant and the brightness is set to ± 1.
Shake up and down by 0 and paste in the direction of low saturation. However, pasting beyond the L axis is not performed.

3. If the pasting process of the above-mentioned 2 also fails as in the case of the color X4, the pasting is performed on the surface of the printer Gamut where the color difference is minimum irrespective of maintaining hue, saturation, and brightness.

The LUT contains the above G including the pasting process.
C corresponding to the X′Y′Z ′ value obtained by performing the amut transform
The MY (K) ink amount is calculated from the measured data value of the printer and described in the LUT.

Further, in order to obtain an optimal Gamut conversion algorithm, evaluation is not performed using a simple color difference.
A method has been proposed in which an evaluation index in which lightness, saturation, and hue are assigned different weights is used. (References: Masahiko Ito, Naoya Kato: "Color gamut compression in CG images (I
I) ”, Color Forum JAPAN '96 Transactions, 1
996). When this algorithm is used, for the CG image, when the display Gamut is compressed, a good reproduction can be obtained by increasing the compression coefficient in the saturation direction or the compression coefficient in the saturation direction and the hue direction. It has been obtained that it is better not to set the compression coefficient large.

[0019]

A problem in color reproduction between a display and a printer is that the printer Gam has a problem.
ut is much smaller than the display Gamut. In the case of a display in which color reproduction is performed by additive color mixing of three primary colors, a pure color with high luminance and high chroma can be reproduced. On the other hand, color reproduction is performed by subtractive color mixing of color inks. Many printers cannot physically reproduce highly saturated pure colors like a display. In other words, the highly saturated pure colors on the display are
It has an external color.

The frequency of appearance of high-saturation pure colors is extremely low in natural images, and relatively low-saturation colors, which are relatively close to achromatic, are included. Therefore, a color reproduction result that can be obtained by using the conventional Gamut conversion is obtained. can get. On the other hand, a CG image artificially generated by a computer tends to capture more vivid colors and create a more impactful image. That is, in the case of a CG image, the image often has a hue that makes full use of a large color gamut called a display.

When all the colors in the display Gamut are output by a color printer, as described with reference to FIG. 1, only the compression of the display Gamut results in many colors remaining outside the printer Gamut. As described above, it is necessary to perform the paste process of FIG. In the case of a natural image, since there are originally few high-saturation colors, there are few colors that require paste processing in the Gamut transform, and even if the color changes continuously, the paste is performed. Relatively good color reproduction can be obtained by the conventional method without the influence of color discontinuity due to processing. However, in the case of a CG image, since many high-saturation colors are included, problems such as color collapse due to the paste process and discontinuous colors appearing in an area where the color changes continuously occur. .

In addition, it is assumed that a gamut that enables a printer to continuously display highly saturated colors on a display.
When a conversion is newly developed and printed out using that technology, if a person who is familiar with the device color using a color printer or printing machine such as a designer or a printing technician, the printer can be used. Since it is possible to roughly predict what kind of color gamut the color gamut has, it is recognized that good color reproduction can be realized by such a method. However, it is rare that general users such as personal computers that are rapidly spreading at present recognize and understand that the printer Gamut is considerably smaller than the display Gamut. When the CG image displayed on the display is compared with the output result by the printer, the general user is not always satisfied with the color reproduction result.

Therefore, an object of the present invention is to provide a color printer for outputting a CG image displayed on a color display, and ask the user how much the color gamut of the printer to be output is. An object of the present invention is to realize a color conversion method for a CG image that can be visually understood and satisfy the user, a color conversion table creation device that creates a color conversion table used in this case, and a color conversion device.

[0024]

According to the present invention, there is provided a color conversion method for performing color conversion between a color display and a color printer, the method comprising the steps of: Outputting a color chart composed of patches on a color printer, displaying a plurality of basic colors on a color display, and selecting a color patch preferred by the user from the color chart for each of the plurality of basic colors. And obtaining a combination of the corresponding colors between the color display and the color printer; and constructing a color conversion from the color display to the color printer based on the combination of the corresponding colors. Is obtained.

According to the present invention, for the achromatic color in the color display, the color conversion method for obtaining the color in the color printer from the colorimetric data of the color chart is obtained.

According to the present invention, there is further provided a color conversion table creating apparatus for creating a color conversion table for use in performing color conversion between a color display and a color printer, and which has a sufficient color reproduction range of the color printer. Means for outputting a color chart composed of color patches of a plurality of colors to be expressed by a color printer, basic primary color selection / display means for selecting a plurality of basic primary colors and displaying them on a color display, Color patch number input means for creating a combination of corresponding colors between a color display and a color printer by allowing a user to specify a corresponding color patch in the color chart; A color classification means for performing two classifications of colors other than primary colors, and a color Color gamut conversion creating means for creating a color gamut conversion between a display and a color printer; color gamut conversion means for applying the color gamut conversion to colors other than the basic primary colors; and A color conversion table creating device is provided, comprising a corresponding color ink amount determining means for determining a corresponding color ink amount in a color printer for the applied color.

According to the present invention, there is also provided a color conversion table creating apparatus for creating a color conversion table for use in performing color conversion between a color display and a color printer, wherein the color reproduction range of the color printer is sufficiently increased. Means for outputting a color chart composed of color patches of a plurality of colors to be expressed by a color printer, basic primary color selection / display means for selecting a plurality of basic primary colors and displaying them on a color display, Color patch number input means for creating a combination of corresponding colors between a color display and a color printer by allowing a user to specify a corresponding color patch in the color chart; and changing the colors in the color display to the basic primary colors and achromatic colors. And color classification means for classifying the colors into colors other than the basic primary colors and the achromatic colors, Color gamut conversion creating means for creating a color gamut conversion between a color display and a color printer from a combination of colors, and color gamut conversion means for performing the color gamut conversion on the colors other than the basic primary colors and achromatic colors And a corresponding color ink amount determining means for determining a corresponding color ink amount in a color printer for the color subjected to the color gamut conversion.

According to the present invention, there is further provided a color conversion table creating apparatus, a color conversion table, and a color signal conversion means for converting a color signal of a color display into a color signal for a color printer using the color conversion table. Is obtained.

According to the present invention, there is also provided a recording medium on which a program for causing a computer to function as the color conversion table creating device is recorded.

According to the present invention, there is further provided a recording medium on which a program for causing a computer to function as the color conversion device is recorded.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color conversion method according to an embodiment of the present invention will be described with reference to the drawings.

In order to realize color reproduction between a color display and a color printer, it is necessary to grasp in advance the color characteristics and the color reproduction range (Gamut) of the display and the printer. In order to obtain Gamut for a display and a printer, it is necessary to measure the color samples of a plurality of colors generated by each device, and to obtain tristimulus values quantitatively representing the colors. The XYZ color system defined by the International Commission on Illumination (CIE) can be used for the tristimulus values of this color.

Display is RGB system, printer is CM
Color reproduction is performed in the YK system, and the color system is completely different. However, by performing color measurement and using the above XYZ color system as a medium, two Gamuts can be converted into one three-dimensional color space. It becomes possible to compare.

The three primary color phosphors of the display device include R
(Red), G (green), and B (blue) are used,
Color reproduction is performed by the additive color mixture. Therefore, the relationship between S = (XYZ) ^t and R = (RGB) ^t is expressed as the following Expressions 2 and 3.

[0035]

(Equation 2)

[0036]

(Equation 3) Here, T is a 3 × 3 transformation matrix. This device R
The conversion matrix T representing the relationship between GB and XYZ is obtained by measuring the chromaticity of each of the RGB phosphors and the reference white set on the display. However, even displays of the same model have variations due to individual differences. Therefore, it is necessary to perform luminance calibration for each display in advance in order to improve the accuracy of color reproduction. Further, even with a calibrated display device, it is inevitable that color unevenness and the luminance of the phosphor at the corner of the screen are reduced by about 70% from that at the center of the screen. It is also necessary to display an image on the screen.

Next, a method of measuring the color gamut of the printer will be described. In a printer, color reproduction is performed by a complex color mixture method including subtractive color mixture, juxtaposition color mixture, additive color mixture, and the like. Therefore, the Gamut cannot be completely obtained by a simple measurement method such as a display.
A general method for accurately obtaining the printer Gamut is to select a plurality of representative colors for each color ink used in the printer, output a color patch created by a combination thereof, and measure the colors.

First, a representative ink amount is selected for each color ink, a color patch composed of a combination of the representative ink amounts of the respective color inks is output and measured, and the surface reflectance of the color patch is obtained. Then, an XYZ value is calculated from the surface reflectance of each color patch. The calculation method is as in the following Expression 4.

[0039]

(Equation 4) Here, S (λ) is the spectral distribution characteristic of illumination, R (λ) is the surface reflectance of the color patch, and x bar (λ), y bar (λ), and z bar (λ) are color matching functions. Is also known data. α is Y = R (λ) is absolute white.
It is a normalization constant such as 100. If the surface reflectance of the color patch is stored in this way, the changed XYZ values can be easily obtained by Expression 4 when the reference illumination is changed, without performing a colorimetric operation. By performing the above measurement and the XYZ calculation for all combinations of the representative ink amounts, the printer Gam
ut can be obtained.

Display is RGB system, printer is CM
The color reproduction is performed in the YK system, and the color system is completely different.
Through the YZ color system, two Gamuts are converted into one
The comparison can be performed in the dimensional color space. However, when the reference white of the display and the illumination (reference white) of the printer are the same, it is possible to make a comparison. FIG.
Is a comparison of the color gamut of a CRT display and the color gamut of a sublimation printer in the RGB space of the display. The cube is the display Gamut, and the plot points in it are the printer Gamut.

Next, the color conversion method of the present invention will be described with reference to the flowchart shown in FIG. First, in the present invention, a color printer is output in advance by a color printer, which is composed of a sufficient number of color patches capable of expressing the color gamut (Step 1). Here, as the color chart output by the printer, a color chart that simultaneously outputs S7, S8, S9, and S10 included in the ISO / JIS-SCID image can be used. (Reference: "High-definition color digital standard image data", supervised by the Image Processing Technology Standardization Committee, published by the Japan Standards Association, 1995). S7-S
The image No. 10 is an image specified by ISO / DIS 12642, and the cyan (C), magenta (M), yellow (Y), and black (K) ink amounts of each color patch are defined. The color chart output by the printer is based on ISO / JI as long as the color patches and the accurate CMYK ink amounts constituting the color patches can be obtained.
Images other than the S-SCID images S7 to S10 can also be used. By showing the color chart to the user, the user can visually grasp the color gamut of the printer.

As shown in FIG. 3, the display often used for CG images is blue (Blue) or cyan (Cya).
It can be seen that a highly saturated color such as n) is a color considerably outside the printer Gamut. For such colors,
It is difficult to realize the Gamut conversion that the user can understand using the conventional method. The user is allowed to specify which of the colors that can be displayed by the printer corresponds to a specific color displayed on the display. The specification method is as follows.
As shown in (2), a plurality of basic primary colors existing in the display Gamut are selected and displayed on the display screen (Step 2). For example, red (R), green (G), blue (B), cyan (C), magenta (M), and yellow (Y), which are vertices of an RGB cube, are used as basic primary colors, and many CG images are targeted. The used primary colors can be used as the basic primary colors. Then, the color patch images of the selected basic primary colors are displayed one by one on the display. At this time, when the RGB digital values on the display can be represented by 8 bits, the (R, G, B) values when the above RGBCMY colors are the basic primary colors are (255, 0, 0) and (0, respectively). , 255,0), (0,
0,255), (0,255,255), (255,
0, 255) and (255, 255, 0).

Then, as shown in FIG. 6, the user compares the color patch image displayed on the display with the color chart output by the printer, and finds the closest color to the color output in Step 1. A selection is made from the color patches in the chart (Step 3). Here, when the user specifies a color patch in the color chart output by the printer, by setting the position number in the color chart as shown in FIG. 7, it is possible to know exactly which color patch is specified. . The hatched color patch in the color chart shown in FIG. 7 is "B3".

Next, the basic primary color R specified by the user
A method for realizing color conversion from a display to a printer based on the relationship between GB and the amount of ink will be described. In the present invention, as a color conversion from a display to a printer, a conversion method using a look-up table (LUT) which is generally widely used is used. A case will be described in which the device color of the display is RGB, the device color of the printer is CMYK, and an LUT that realizes color conversion from RGB to CMYK is created.
Instead of RGB on the input side like XYZ and CMY, L ^* a ^* b ^* and CMYK, data of another color system may be used, and even if the output side becomes three-dimensional like CMY good.

FIG. 8 shows an example of the color conversion LUT. In the color conversion LUT, RGB values and CMYK ink amounts corresponding to the RGB values can be described. Display black (R, G, B) = (0, 0, 0) and display white (R, G, B) = (255, 255, 255)
Are set to black and white (paper) in the printer, respectively. Next, the ink amount corresponding to the basic primary color displayed on the display is set to the ink amount of the color patch specified by the user. In FIG. 8, as the ink amount corresponding to blue (0, 0, 255) displayed as the basic primary color,
CMYK ink amount (C
B, M B, Y B, K B) is set.

Next, of the remaining RGB values for which the color ink amount is not specified, for the color existing on the gray axis,
From the display RGB values, XY using Equation 2
The Z value is calculated, a search process is performed from the measured data of the printer Gamut using a color conversion method that respects the colorimetric data of the printer, and a corresponding ink amount is determined (St.
ep4). This color conversion method obtains an ink amount corresponding to an input XYZ value by dividing colorimetric data of a printer Gamut into triangular pyramids having adjacent data points as vertices and searching for all triangular pyramids. Can be. For example, this method is disclosed in Japanese Patent Application No. 4-172 for CMY three colors.
246 can be used. In the case of four colors of CMYK, the method of Japanese Patent No. 2621789 can be used, but other methods can also be used. However, in order to perform this processing, it is necessary to measure the colors of all the color patches in the color chart output in Step 1 in advance (Step 8). If a color chart composed of color patches based on a combination of color ink amounts whose colorimetric values are already known is output in Step 1, the colorimetry in Step 8 is not necessary.

Next, a method of determining the ink amounts of the remaining RGB values other than the basic primary color and gray will be described.
The color patch of the printer output corresponding to the basic primary color has already been specified by the user. That is, clues of RGB → CMYK conversion have been obtained by the user, and the color ink amounts corresponding to the remaining display colors are calculated based on the clues of the color conversion by the user.
First, the XYZ values of the basic primaries displayed on the display can be calculated from Equation 2, and X'Y 'is obtained from the colorimetric data of the output color patch of the printer corresponding to the basic primaries.
The Z 'value is obtained. That is, the Gamut conversion by the user allows the X ′ after the Gamut conversion to be converted from the original XYZ value.
This means that the combinations of Y'Z 'values are obtained for the number of basic primary colors.

XYZ-X 'obtained by the user
From the combination of Y′Z ′, a Gamut transform is calculated (S
step5). From the above-mentioned general Gamut conversion formula (Equation 1), the Gamut conversion XYZ designated by the user →
It is assumed that X′Y′Z ′ can be represented by a 3 × 3 matrix. At this time, the Gamut conversion equation specified by the user is as shown in Equation 5 below.

[0049]

(Equation 5) Each element a _ij (i, j = 1 to 3 × 3 matrix on the right side of Expression 5)
3) can be solved using the relationship between the already obtained basic primary colors and the corresponding XYZ-X'Y'Z 'of the printer output color patches.

First, when six basic colors are used, three equations can be formed for each color, so that a total of 18 equations can be obtained. Expressing the 18 equations in the form of a matrix, the unknown a
_The equation relating to _ij can be expressed as Equation 6 below.

[0051]

(Equation 6) It can be solved unknowns a _ij of the equation (Equation 6) by utilizing the method of least squares. From the above, the relationship between the basic primary colors and the color patches designated by the user indicates that Ga
Mut transformation can be created.

Next, for the remaining RGB values (basic primary colors and colors other than those on the gray axis), the corresponding ink amounts are calculated. In this processing, the XYZ values of the RGB values are substituted into the right side of the Gamut conversion formula (Equation 5) specified by the user,
Calculate X′Y′Z ′ value after Gamut conversion (Step
p6). Then, an ink amount corresponding to the X'Y'Z 'value after the Gamut conversion is obtained (Step 7). This Ste
In p7, as in the method of calculating the ink amount corresponding to the gray in Step 4, in the case of three colors of CMY, Japanese Patent Application No.
-172246 can be used, and CM
In the case of four colors of YK, the method of Japanese Patent No. 2621789 can be used. Other techniques are available.

As described above, all the RGB values described in the color conversion LUT and the corresponding CMYK ink amounts can be described. Actually, when color image data such as a CG image is converted into the CMYK ink amount using the color conversion LUT, the RGB values use the ink amount described in the color conversion LUT as they are, and the other colors are not used. Calculate the ink amount by interpolation.

In the above-described color conversion method, first, a color chart is output by a color printer (Step 1).
Next, a plurality of basic primary colors are displayed on the display (St
ep2) Then, the user determines the amount of ink corresponding to the basic primary color of the display by using the color chart (Step 3), and determines the amount of gray ink (S3).
Step 4), calculate the Gamut transform (Step 5),
Gamut conversion is applied to the remaining display colors (St
ep6) Finally, the amount of ink corresponding to the color after Gamut conversion was determined (Step 7). However, the execution order of each step is not limited to this. S
Step1 and Step2 are executed before Step3,
Step3 is executed before Step5, Step5 is executed before Step6, and Step7 is executed before Step7.
6 is executed, and Step4 is performed before Step4 and Step7.
8 can be performed in any order.

Further, when calculating the Gamut conversion from the relationship between the basic primary colors displayed on the display of Step 5 and the color patches specified by the user, the above color conversion method uses a linear conversion using a 3 × 3 matrix. The Gamut transform described above is taken as an example, but the matrix transform incorporating a higher-order term or the Gammut transform using a non-linear transform is described.
The ut transform can be used as well. In this case, instead of a simple least squares method, an optimal conversion coefficient is obtained by using an algorithm such as Powcl's quadratic convergence method or hill-climbing method in the minimization problem.

[0056]

[Embodiment 1] FIG. 9 is a block diagram of a color conversion table creating apparatus according to Embodiment 1 of the present invention.

The color conversion table creating apparatus 200 is connected to a color display 100 and a color printer 101 whose color characteristics are known. Color display 10
0 performs color reproduction using RGB three-color light, and the color printer 101 performs color reproduction using a plurality of color inks such as CMY or CMYK. The color conversion table creation device 200 creates a color conversion LUT 104 for outputting image data 105 including many high-saturation colors such as CG images displayed on the color display 100 to the color printer 101.

The color conversion table creation device 200 includes a basic primary color selection / display unit 1 and a color patch number input unit 2
, Color classification means 3, Gamut conversion creating means 4, G
An amut conversion unit 5, a corresponding ink amount determination unit 6, and a color chart output unit 7 are provided.

Next, the operation of the present apparatus will be described.

The basic primary color selection / display means 1 selects, as basic primary colors, highly saturated colors in the color reproduction range of the color display 100 or colors frequently used in the image data 105 to be output by the color printer 101. It is displayed on the color display 100. The color chart output means 7 causes the color printer 101 to output a color chart 102 representing the color reproduction range of the color printer 101 and specifying the position of each color patch, as shown in FIG. 7, for example. The color patch number input unit 2 causes the color conversion table creation device 200 to input a color patch in the color chart 102 that the user feels closest to each basic primary color displayed by the basic primary color selection / display unit 1.

It is assumed that the color chart 102 has been measured in advance and a color measurement data file 103 has been obtained.

The color classification means 3 includes a color display 10
The colors on 0 are classified into a basic primary color signal C1 and a color signal C2 other than the basic color.

For the basic primary color signal C 1, the color ink amount corresponding to the color patch number specified by the user is described as it is in the corresponding portion of the color conversion LUT 104. still,
In the color conversion LUT 104, it is assumed that the format can describe RGB values and corresponding color ink amounts, for example, as shown in FIG.

The Gamut conversion creating means 4 converts the combination of the basic primary colors and the color patches designated by the user into G
Create an amut transform. In the Gamut conversion creating means 4, for example, assuming a conversion formula such as Expression 5 as the Gamut conversion, the correspondence relationship between XYZ-X'Y'Z 'obtained from the combination of the basic primary colors and the color patches designated by the user is determined. The unknown _aij (i, i,
j = 1 to 3), an equation (Formula 6) for obtaining a matrix composed of unknowns a _{ij is} obtained by using the least squares method.
Is calculated. Through the above processing, the Gamut conversion creating means 4 can create the Gamut conversion. Here, Gamut conversion other than Equation 5 may be used.

The Gamut conversion means 5 applies a G signal to the color signals C 2 other than the basic primary colors classified by the color classification means 3.
The Gamut transform created by the amut transform creating means 4 is performed. Then, the color after the Gamut conversion becomes an input signal to the corresponding ink amount determining means 6, the corresponding ink amount determining means 6 determines the color ink amount in the color printer 101, and is described in a corresponding portion of the color conversion LUT 104,
The color conversion LUT 104 is completed.

The corresponding ink amount determining means 6 receives the measurement data file 103 and determines the color reproduction range of the color printer 101 in order to determine the color ink amount of the color printer 101 corresponding to the input color. The color ink amount corresponding to the input color is determined while respecting the measurement data.
The corresponding ink amount determining means 6 can use the method proposed in Japanese Patent Application No. 4-172246 in the case of CMY three-color ink, and Japanese Patent No. 2621789 in the case of MYK four-color.
However, other methods are also available, such as a number method.

[Embodiment 2] FIG. 10 shows Embodiment 2 of the present invention.
FIG. 1 is a block diagram of a color conversion table creation device according to the first embodiment.

The color conversion table creation device 201 includes a basic primary color selection / display unit 1 and a color patch number designation unit 2
, Color classifying means 8, Gamut conversion creating means 4, G
An amut conversion unit 5, a corresponding ink amount determination unit 6, and a color chart output unit 7 are provided.

The color conversion table creating apparatus 201 converts the gray on the color display 100 into the color printer 10.
In this embodiment, the color classification means 3 of the color conversion table creating apparatus 200 shown in FIG. 9 is replaced with a color classification means 8 capable of classifying the gray signal C3 so that the color signal 1 can be reproduced in the same gray. The basic primary color signal C
1, a gray signal C3, a basic primary color, and a color signal C4 other than gray.

For the basic primary color signal C 1, the color ink amount corresponding to the color patch number specified by the user is described as it is in the corresponding portion of the color conversion LUT 104.

The gray signal C3 is used as an input color signal to the corresponding ink amount determination means 6 without being subjected to Gamut conversion, and the colorimetric data file 103 is used so that the gray is reproduced by the color printer 101. Then, the ink amount is calculated and described in the corresponding portion of the color conversion LUT 104.

The color signals C4 other than the basic primary colors and gray are the same as the color signals C2 in the color conversion table creation device 200.

[Embodiment 3] FIG. 11 shows Embodiment 3 of the present invention.
1 is a block diagram of a color conversion device according to the present invention.

The color conversion apparatus 202 is connected to the color display 100 and the color printer 101, and receives the image data 105. The color conversion device 202 includes a color conversion table creation device 201, a color conversion LUT 104 created by the color conversion table creation device 201, and a color signal conversion unit 9.

The color conversion device 202 is a device for outputting, to the color printer 101, image data 105 containing many high-saturation colors such as CG images displayed on the color display 100.

In the color conversion table creating apparatus 201,
Color conversion L from the color display 100 to the color printer 101 using a simple user interface
Create the UT 104. Then, this color conversion LUT 10
4, each pixel value of the image data 105 is converted into a color ink amount in the color printer 101 and output to the color printer 101.

The details of the color conversion table creation device 201 are as follows.
This is as described in the second embodiment. The color signal conversion unit 6 calculates the color ink amount corresponding to each pixel value of the image data 105 by using the color conversion LUT 104 created by the color conversion table creation device 201 and by using interpolation calculation or the like. And outputs it to the color printer 101.

The color conversion table creating device and the color conversion device described above can be realized by a computer such as a personal computer, and each means of the device can be realized by a program for causing a computer to function as a device.
Also, this program can be recorded on a recording medium that can be read at an opportunity.

[0079]

By presenting a user with a plurality of color patches actually output by a color printer, the user can visually grasp the color gamut of the printer which the user intends to use. Then, by fusing the RGB-ink amount relationship obtained by allowing the user to select a basic primary color on a display from which color reproduction is difficult from the color patches and the RGB-ink amount obtained by colorimetry, By creating an optimal color conversion LUT,
It is possible to realize color reproduction that the user can understand.

[Brief description of the drawings]

FIG. 1 shows a general Gamu relating to the present invention and a conventional example.
It is a figure for explaining t conversion.

FIG. 2 is a diagram for explaining a pasting process in Gamut conversion.

FIG. 3 is a diagram for explaining the embodiment of the present invention, and is a diagram comparing a display Gamut and a printer Gamut.

FIG. 4 is a diagram for describing an embodiment of the present invention, and is a flowchart illustrating an example of a conversion procedure of a color conversion method.

FIG. 5 is a diagram for explaining the embodiment of the present invention, and is a diagram showing a state where a color patch image is displayed on a display.

FIG. 6 is a diagram for explaining the embodiment of the present invention, and is a diagram illustrating a state in which a display and a color chart are compared.

FIG. 7 is a diagram for describing an embodiment of the present invention, and is a diagram illustrating an example of a color chart output by a printer.

FIG. 8 is a diagram for describing an embodiment of the present invention, and is a diagram illustrating an example of a color conversion LUT.

FIG. 9 is a block diagram of a color conversion table creating device according to the first embodiment of the present invention.

FIG. 10 is a block diagram of a color conversion table creation device according to a second embodiment of the present invention.

FIG. 11 is a block diagram of a color conversion apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Basic primary color selection / display means 2 Color patch number input means 3 Color classification means 4 Gamut conversion creation means 5 Gamut conversion means 6 Corresponding ink amount determination means 7 Color chart output means 8 Color classification means 9 Color signal conversion means 100 Color display 101 Color printer 102 Color chart 103 Colorimetric data file 104 Color conversion LUT 105 Image data 200 Color conversion table creation device 201 Color conversion table creation device 202 Color conversion device

Claims (7)

[Claims] 1. A color conversion method for performing color conversion between a color display and a color printer, wherein a color chart composed of a plurality of color patches that sufficiently express the color reproduction range of the color printer is provided. Output, the step of displaying a plurality of basic primaries on a color display, the step of selecting a user-preferred color patch from the color chart for each of the plurality of basic primaries, a color display and a color printer And a step of constructing a color conversion from a color display to a color printer based on the combination of the corresponding colors. 2. The color conversion method according to claim 1, wherein, for achromatic colors in a color display, colors in a color printer are obtained from colorimetric data of the color chart. 3. A color conversion table creating apparatus for creating a color conversion table used when performing color conversion between a color display and a color printer, the apparatus comprising a plurality of colors for sufficiently expressing a color reproduction range of the color printer. Means for outputting a color chart composed of color patches by a color printer, basic primary color selection / display means for selecting a plurality of basic primary colors and displaying them on a color display, and the color chart corresponding to the plurality of basic colors Color patch number input means for creating a combination of corresponding colors between the color display and the color printer by allowing the user to specify the color patches in the color patches, and changing the colors in the color display to the basic primaries and colors other than the basic primaries. A color display and a color display based on a color classification means for performing two classifications and a combination of the corresponding colors; A color gamut conversion creating unit that creates a color gamut conversion between the printer and the color gamut conversion unit that performs the color gamut conversion on colors other than the basic primary colors; and the color gamut conversion is performed. A color conversion table creating device, comprising: a corresponding color ink amount determining means for determining a corresponding color ink amount in a color printer for a color. 4. A color conversion table creating apparatus for creating a color conversion table used when performing color conversion between a color display and a color printer, the apparatus comprising a plurality of colors for sufficiently expressing a color reproduction range of the color printer. Means for outputting a color chart composed of color patches by a color printer, basic primary color selection / display means for selecting a plurality of basic primary colors and displaying them on a color display, and the color chart corresponding to the plurality of basic colors Color patch number input means for creating a combination of corresponding colors between a color display and a color printer by allowing a user to specify a color patch in the color patches; and inputting the colors in the color display to the basic primaries, achromatic colors, and the basic primaries. And color classification means for classifying the colors into colors other than the achromatic color, and Color gamut conversion creating means for creating a color gamut conversion between a display and a color printer; color gamut conversion means for performing the color gamut conversion on the colors other than the basic primary colors and achromatic colors; and A color conversion table creating apparatus, comprising: a corresponding color ink amount determining unit that determines a corresponding color ink amount in a color printer for a color that has undergone reproduction range conversion. 5. A color conversion table creating apparatus according to claim 3 or 4, a color conversion table, and a color signal for converting a color signal of a color display into a color signal to a color printer using the color conversion table. A color conversion device having a conversion unit. 6. A recording medium on which a program for causing a computer to function as the color conversion table creating device according to claim 3 is recorded. 7. A recording medium on which a program for causing a computer to function as the color conversion device according to claim 5 is recorded.