JPH09178561A - Simulation system for coloration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To represent an actual color under different illumination lights. SOLUTION: A spectral reflectance estimation means estimates the spectral reflectance of an object from a main component extracted by main component analysis from a spectral reflectance data of standard color chart and three stimulus values of object. A three stimulus value calculation means determines the three stimulus values of object under an arbitrary illumination conditions, based on the estimates spectral reflectance and arbitrary illumination conditions. A corresponding color predicting means predicts a corresponding color under standard light which appears similarly to the color under arbitrary illumination conditions from three stimulus values according to a color adaptation predictive formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color appearance simulation system for predicting and simulating a change in color appearance caused by a change in illumination light.

[0002]

2. Description of the Related Art In color design using a color display by computer graphics, it is used for visual color examination in various fields such as various designs.

Conventionally, in the case of color display on a color display, the tristimulus values of the visual target are input to convert the tristimulus values into RGB values of the color display, and the color display of the visual target is performed.

Further, even in the color display calculation of the visual object illuminated by different illumination light, the RGB values of the color display are obtained from the tristimulus values and the color display is performed. But,
In practice, the illumination light and the RGB of the visual target are obtained in advance, and color display is performed from the product of the illumination light and the RGB of the visual target. This is because the calculation processing time may be shortened, but the spectral reflectance of the visual target may be unknown and only the tristimulus values may be given.

[0005]

By the way, in terms of the actual appearance of colors, when an object to be viewed is illuminated with illumination light having the same relative spectral radiance distribution, it is more vivid when the illuminance is high. Are known. It is also known that the appearance of a visual object illuminated by illumination light that changes with time and weather, such as daylight, does not change to the extent that the relative spectral radiance distribution of the illumination light changes. There is.

However, in the prior art, when color display of a visual target illuminated with different illumination light is performed, and the spectral reflectance of the visual target is unknown, the R of the illumination light and the visual target are R.
Since the color display is performed from the product of GB, it is not possible to sufficiently display the color appearance as described above. That is, when a visual target is illuminated with illumination light having the same relative spectral radiance distribution, it does not look colorful even though the illuminance is high, or with illumination light that changes with time or weather, such as daylight. There is a problem in that the appearance of the illuminated visual target does not change as much as the degree of change in the relative spectral radiance distribution of the illumination light, but changes significantly.

The present invention has been made in view of such a point, and a color appearance capable of sufficiently expressing a color appearance under different illumination lights as well as an actual appearance. The purpose is to provide one of the simulation systems.

[0008]

According to another aspect of the present invention, there is provided a simulation system for appearance of colors, comprising: a principal component extracted from spectral reflectance data of a standard color chart by a principal component analysis method; and a tristimulus value of a visual target. Spectral reflectance estimating means for estimating the spectral reflectance of the visual target from the tristimulus value calculating means for obtaining the tristimulus value of the visual target under the arbitrary lighting condition from the estimated spectral reflectance and the arbitrary lighting condition And a corresponding color predicting unit that predicts a corresponding color under standard light that gives the same appearance as a color under arbitrary lighting conditions from the obtained tristimulus values by a color adaptation prediction formula. Is characterized by. In this way, the spectral reflectance of the visual target is estimated, the tristimulus value of the visual target under the arbitrary lighting conditions is obtained, and the color adaptation prediction formula is used to calculate the color under the arbitrary lighting conditions from the obtained tristimulus values. By predicting the corresponding color under the standard light that gives the same appearance as that of, the appearance of the color under different arbitrary illumination light can be sufficiently expressed as the actual appearance.

A color appearance simulation system according to a second aspect of the present invention is the color appearance simulation system according to the first aspect, in which the corresponding color predicted by the corresponding color predicting means is corrected according to the illuminance of the visual target. It is characterized by comprising corresponding color correction means. In this way, by correcting the corresponding color predicted by the corresponding color predicting means according to the illuminance of the visual target, for example, the appearance of the color can be seen in accordance with changes in the illuminance such as the sun and shade. As well as, it becomes possible to express sufficiently.

According to a third aspect of the present invention, there is provided a simulation system for observing colors, wherein in the simulation system for observing colors according to the first or second aspect, illumination condition data of a plurality of illuminating lights capable of selecting arbitrary illumination conditions. It is characterized in that it comprises a database means for accumulating.
This allows any lighting condition to be selected from the database and set.

A color appearance simulation system according to a fourth aspect is the same as the color appearance simulation system according to any one of the first to third aspects, in which the RGB conversion means converts the tristimulus values of the corresponding color into RGB values. It is characterized by having. This makes it possible to display the appearance of colors on the color display.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color appearance simulation system of the present invention will be described below with reference to the drawings.

FIG. 2 shows a block diagram of the entire system. Reference numeral 11 is a computer device to which a color display 12, a color printer 13 and an input unit 14 are connected. The color display 12 is R (R
ED), G (GREEN), and B (BLUE) are controlled in 256 stages, respectively, and 16 by the combination thereof.
A full-color type CRT with the expression power of 770,000 colors is used. The input unit 14 includes a keyboard, a mouse, a digitizer, and the like.

The computer device 11 has the following functions as software. The function of the spectral reflectance estimation means for estimating the spectral reflectance of the visual target from the principal component extracted by the principal component analysis method from the spectral reflectance data of the standard color chart and the tristimulus values of the visual target. A function of a tristimulus value calculation means for obtaining a tristimulus value of a visual object under an arbitrary illumination condition from the estimated spectral reflectance and the arbitrary illumination condition. A function of a corresponding color predicting unit that predicts a corresponding color under standard light that gives the same appearance as the color under arbitrary lighting conditions from the obtained tristimulus values by a color adaptation prediction formula. A function of a corresponding color correction unit that corrects the corresponding color predicted by the function of the corresponding color prediction unit according to the illuminance of the visual target. A function of RGB conversion means for converting tristimulus values of corresponding colors into RGB values. A function of a database means that accumulates illumination condition data of a plurality of illumination lights that enables selection of arbitrary illumination conditions.

The database means preliminarily creates a database relating to the following illumination light. CIE daylight,
Nagaoka daylight, Amagasaki daylight, New Delhi daylight, fluorescent lamps (F1 to F12), mercury lamps, arbitrary light sources.

Next, a simulation of the appearance of the color of the visual target (object) to be displayed on the color display 12 will be described with reference to the flowchart of FIG.

First, the tristimulus values XYZ of the color of the visual target are input from the input unit 14 (step 1).

The Mansen value HV is used as the input method.
/ C (Hue / Brightness / Saturation) (display method of JIS Z8721 color-determined by HV / C and Y, xy specified in the display by three attributes by graphic interpolation conversion), and its input Is a hue number (for example, 5), a hue symbol (for example, R), a lightness (for example, 5.2), and a saturation (for example, 1).
4.5) is used. In this case, the computer device 11
Has a function of a conversion unit that obtains the reflectance Y and the chromaticity xy from the input HV / C and obtains the tristimulus value XYZ from the reflectance Y and the chromaticity xy.

Next, the spectral reflectance of the visual target is estimated (step 2).

The purpose of estimating the spectral reflectance of the visual target is that the tristimulus value XYZ and the Mansen value HV / C of the visual target to be input are values obtained by the standard light C (or D ₆₅ ). Spectral reflectance of a visual target is estimated in order to obtain tristimulus values when the visual target is illuminated with different illumination light.

A principal component analysis is performed on a data group of a color chart (for example, a JIS standard color chart) to which a spectral reflectance is given to extract main principal components. When the extracted principal components are used, the spectral reflectance of the color chart is defined by the following equation (1) as a linear combination of the principal components.

[0022]

[Equation 1] From equation (1), the tristimulus value of the color chart is defined by the following equation (2).

[0023]

[Equation 2] X ₀ , Y ₀ , Z ₀ and X _i (i = 1 to 3), Y _i (i
= 1 to 3) and Z _i (i = 1 to 3) are the average spectral reflectance R ₀ (λ) and the eigenvector R _i obtained from the principal component analysis.
Since it can be calculated from (λ), the weighting factor k _i (i = 1 to 3) is calculated by the following equation (3).

[0024]

(Equation 3) Therefore, even if the spectral reflectance of the visual target is unknown, the spectral reflectance ρ ′ (λ) of the color to which the tristimulus value XYZ or HV / C of the visual target is given can be estimated by the equation (1).

An example of using a JIS-compliant standard color chart is "Analysis of Spectral reflectance distribution of Munsell color chart" (Journal of Japan Color Society, Vol.7 No.4 1983 pp167-174).

Next, the illumination condition of the visual target is input (step 3).

In this system, a database regarding the following illumination light is created in advance. CIE daylight, Nagaoka daylight, Amagasaki daylight, New Delhi daylight, fluorescent lamps (F1 to F12), mercury lamps, arbitrary light sources.

For the daylights of to, the relative spectral distribution S _r (λ) of the illumination light is set by selecting the type of daylight data and inputting the chromaticity coordinates or the correlated color temperature. For the fluorescent lamp, a known relative spectral distribution S _r (λ) is set by selecting from 12 types of fluorescent lamps. The known relative spectral distribution S _r (λ) is set by selecting the mercury lamp.
For illumination lights other than the above, the relative spectral distribution S _r (λ) is set by creating data as an arbitrary light source and directly inputting the relative spectral distribution S _r (λ) of the illumination light.

Next, the appearance of the color of the visual object under different illumination is predicted. In this prediction, first, a tristimulus value under arbitrary illumination (designated illumination) is calculated (step 4), and then a corresponding color is predicted by a color adaptation prediction formula based on the obtained tristimulus value. Perform (step 5). Note that corresponding color is the value under the standard light C (or D _65), corresponding in under the same appearance as the appearance of color in the specified lighting conditions standard light C (or D ₆₅₎ Predict colors. This processing is performed in order to compare with the appearance under the standard light C (or D ₆₅ ).

The tristimulus value under the designated illumination (test illumination in the chromatic adaptation prediction formula) is obtained by searching the database for the illumination light corresponding to the illumination condition of the designated visual target, and combining the relative spectral distribution with the spectral reflectance. Calculate from and. That is, from the spectral reflectance ρ ′ (λ) estimated by the equation (1) and the relative spectral distribution S _r (λ) of the input illumination light,
The tristimulus value X _R Y _R Z _R under the designated illumination is _calculated by the following equation (4).

[0031]

(Equation 4) The corresponding color is predicted by the color adaptation prediction formula by using the tristimulus value X _R Y _R Z _R and the illuminance value under the specified illumination as the parameters of the color adaptation formula, and the corresponding color at the standard light C and the standard illuminance 1000 lx is CIE chromatic adaptation. Estimate by formula.

For example, the tristimulus value X of the visual target is X = 72.7.
6, Y = 73.37, Z = 71.11, chromaticity of test illumination x = 0.3588, y = 0.3397, color temperature = 4
At 415K and an illuminance of 50000 lx, the tristimulus values under the test illumination are X _R = 79.40 and Y _R =
73.91, Z _R = 53.40, and the prediction of the corresponding color under standard illumination (standard light C, illuminance 1000 lx) is X ′ = 148.44, Y according to the CIE chromatic adaptation formula.
It is determined that ′ = 146.01 and Z ′ = 130.37.

Next, the corresponding color is corrected in consideration of incomplete adaptation (step 6).

This is because in everyday scenes where the sun and shade are often observed at the same time, the shade is evaluated to be darker because it is influenced by the white of the sun even if it is adapted to enter the shade. Will be done (reverse if you are accustomed to Hinata). From this, the corresponding colors of white in the sun and shade are predicted, and the shade value is corrected in the case of the sun, and the sun value is corrected as white under adaptation in the case of the shade.

That is, in order to match the corresponding color in the situation where the sun and shade are observed at the same time with the actually observed perceptual color, the corresponding sun colors (X ', Y', Z
When converting from ') to the CIELAB color system, correction is performed by using the corresponding color of the shaded perfect diffusion surface as white.

Here, Example 1 for correction of corresponding colors will be described.

Tristimulus values of visual object X = 72.76, Y = 7
3.37, Z = 71.11, chromaticity of test illumination (sunlight) x = 0.3588, y = 0.3397, color temperature = 44
15K, illuminance 50000lx, chromaticity of test illumination (shade) x = 0.3266, y = 0.3205, color temperature = 57
97K, illuminance 8500lx.

Predicting the corresponding color of the test illumination (sunlight) of the visual object, X '= 148.44, Y' = 146.01, Z
′ = 130.37.

When the corresponding color of the test illumination (shade) on the perfect diffusion surface is predicted (however, the chromaticity is treated as the same as the test illumination (sunlight)), Xn '= 148.44, Yn' = 146.
01 and Zn '= 130.37.

When the corresponding color of the visual object is converted into the CIELAB color system by correcting with the illuminance of the test illumination (shade), L ^* '
= 94.83, a ^* '= 5.76, b ^* ' = 17.07
Becomes

Table 1 below shows a comparison with the actually perceived color of the visual target. The visual observation is a conversion of the subjective evaluation result based on the NCS color system into a CIELAB value by graphic conversion.

[0042]

[Table 1] Therefore, the value when the corresponding color is corrected with respect to the actually observed perceived color of the visual target becomes a value closer to that when the corresponding color is not corrected.

A second example of correction of corresponding colors will be described.

Tristimulus values of visual object X = 62.10, Y = 6
1.37, Z = 75.00, chromaticity of test illumination (sunlight) x = 0.3588, y = 0.3397, color temperature = 44
15K, illuminance 50000lx, chromaticity of test illumination (shade) x = 0.3266, y = 0.3205, color temperature = 57
97K, illuminance 8500lx.

Predicting the corresponding color of the test illumination (sunlight) of the visual target, X '= 119.33, Y' = 112.64, Z
′ = 143.13.

When the corresponding color of the test illumination (shade) on the perfect diffusion surface is predicted (however, the chromaticity is treated as the same as the test illumination (sunlight)), Xn '= 164.19, Yn' = 167.
42 and Zn '= 197.93.

When the corresponding color of the visual target is converted into the CIELAB color system by correcting the illuminance of the test illumination (shade), L ^* '
= 85.65, a ^* '= 11.42, b ^* ' =-4.2
It becomes 7.

The following Table 2 shows a comparison with the actually perceived color of the visual target. The visual observation is a conversion of the subjective evaluation result based on the NCS color system into a CIELAB value by graphic conversion.

[0049]

[Table 2] Therefore, the value when the corresponding color is corrected with respect to the actually observed perceived color of the visual target becomes a value closer to that when the corresponding color is not corrected.

Next, the tristimulus values of the visual target based on the appearance of colors are converted into RGB (step 7).

X _R Y _R Z _R , X _G Y _G Z of the three primary color phosphors of the color display 12 when the white balance is adjusted to match the chromaticity of standard light C (or D ₆₅ ).
_G , X _B Y _B Z _B are measured with a spectroradiometer. Measured Y
Normalization is performed so that the sum of _R , Y _G and Y _B becomes 100.

The emission luminances γ _R , γ _G and γ _B corresponding to the emission control signal of the color display 12 are measured with a spectroradiometer to obtain the emission control signal-luminance luminance characteristic (γ characteristic).

Γ _R , γ _G and γ _B corresponding to the given tristimulus values are calculated by the following equation (5).

[0054]

(Equation 5) Γ _R γ _G γ _B and color display obtained by equation (5)
The light emission control signal RGB of the color display 12 is obtained from the 12 γ characteristic.

As described above, the spectral reflectance of the visual target is estimated, the tristimulus value of the visual target under an arbitrary illumination condition is obtained, and an arbitrary illumination is calculated from the obtained tristimulus value by the chromatic adaptation prediction formula. By predicting the corresponding color under standard light that will be the same as the color appearance under the conditions, and correcting the predicted corresponding color according to the illuminance of the visual target, for example,
When a visual target is illuminated with illumination light having the same relative spectral radiance distribution, it can be displayed more vividly when the illuminance is high, and it changes depending on time and weather like daylight. When illuminated with illuminating light,
It can be displayed so that it does not change so much as the degree of change in the relative spectral radiance distribution of the illumination light, and therefore, the appearance of colors under different illumination light is sufficiently expressed as well as the actual appearance. be able to.

[0056]

According to the color appearance simulation system of the first aspect, the spectral reflectance of the visual target is estimated, and the tristimulus values of the visual target under an arbitrary illumination condition are obtained and obtained. By predicting the corresponding color under standard light that gives the same appearance as the color appearance under any lighting condition from the tristimulus values by the color adaptation prediction formula, the color The appearance can be expressed sufficiently as the actual appearance.

According to the color appearance simulation system of the second aspect, in addition to the effect of the color appearance simulation system of the first aspect, the corresponding color predicted by the corresponding color predicting means is viewed. By correcting in accordance with the illuminance, the color appearance can be sufficiently expressed in the same manner as the actual appearance in response to changes in the illuminance such as the sun and shade.

According to the color appearance simulation system of claim 3, in addition to the effect of the color appearance simulation system of claim 1 or 2, a plurality of arbitrary illumination conditions can be selected. By including the database means for accumulating the illumination condition data of the illumination light, it is possible to easily select and set any illumination condition from the database.

According to the color appearance simulation system of claim 4, in addition to the effect of the color appearance simulation system of any one of claims 1 to 3, in addition to the tristimulus values of the corresponding color to the RGB value. By including the RGB conversion means for converting to, the appearance of colors can be displayed on the color display.

[Brief description of the drawings]

FIG. 1 is a flow chart showing an embodiment of a color appearance simulation system of the present invention and explaining a simulation procedure.

FIG. 2 is a configuration diagram illustrating a system configuration of the above embodiment.

[Explanation of symbols]

11 Spectral reflectance estimating means, tristimulus value calculating means, corresponding color predicting means, corresponding color correcting means, database means, RGB
Computer device having function of converting means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Sachiyo Tsukahara 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Yutaka Masuda 4-1-1, Higashi-Hachiman, Hiratsuka, Kanagawa Nishi Paint Co., Ltd. (72) Inventor Keiji Hasegawa 4-17-1, Higashi-Hachiman, Hiratsuka City, Kanagawa Kansai Paint Co., Ltd.

Claims (4)

[Claims] 1. Spectral reflectance estimating means for estimating the spectral reflectance of a visual target from the principal component extracted from the spectral reflectance data of a standard color chart by a principal component analysis method and the tristimulus values of the visual target, Tristimulus value calculation means for obtaining the tristimulus value of the visual target under the arbitrary illumination condition from the calculated spectral reflectance and the arbitrary illumination condition, and the arbitrary illumination condition by the chromatic adaptation prediction formula from the obtained tristimulus value A color appearance simulation system, comprising: a corresponding color predicting unit that predicts a corresponding color under standard light having the same appearance as a color below. 2. The color appearance simulation according to claim 1, further comprising: a corresponding color correcting unit that corrects the corresponding color predicted by the corresponding color predicting unit according to the illuminance of the visual target. system. 3. The color appearance simulation according to claim 1 or 2, further comprising a database means for accumulating illumination condition data of a plurality of illumination lights that enables selection of arbitrary illumination conditions. system. 4. The color appearance simulation system according to claim 1, further comprising RGB conversion means for converting tristimulus values of corresponding colors into RGB values.