Image analysis – Color image processing – Color correction
Reexamination Certificate
1996-10-01
2001-11-20
Grant, II, Jerome (Department: 2624)
Image analysis
Color image processing
Color correction
C358S518000
Reexamination Certificate
active
06320980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method and a recording medium storing a program for such the method, which perform a color process for visually matching a body color and a light source color with each other.
2. Related Background Art
In recent years, color image products are widely popularized, so that a color image can easily be managed not only in a specific field of, e.g., producing a design by using computer graphics (CG) but also in general office environment. In such a state, in a case where the image formed on a monitor is output by an image printer, there is a problem that a color of the image on the monitor does not match or coincide with a color of the printed image. In order to solve such the problem, a color management system is being remarked. The color management system is to eliminate differences of colors in respective devices by using a common color space. At present, the differences of colors in the respective devices are intended to be corrected by using XYZ tristimulus values. Basically, if the two colors have the same value in the common color space, there colors should be viewed or observed as the same color. However, there is a problem that, even if they have the same value, these two colors cannot actually be viewed as the same color because of a difference in spectral waveform or the like due to a difference in modes between a light source color and a body color.
In this case, the light source color is a color of a light generated from a light source, and the body color is a color of a body (or substance, object) on which the light is reflected or to which the light penetrates.
As a method for solving the above problem, it can be supposed that a color matching experiment is performed in each color to determine a conversion coefficient in each color.
However, in case of actually outputting the image formed on a CRT or the like, a very large number of colors are used, as can be understood from a natural image. Therefore, a long period of time is necessary to determine the conversion coefficient for each color by performing the color matching experiment for each color, because of following reasons:
1) the color matching experiments are necessary for a large number of colors;
2) the color matching experiments are necessary to be performed by a large number of persons; and
3) a long period of time is necessary for performing the color matching experiment for a single color.
Another problem will be explained with reference to FIG.
12
.
FIG. 12
shows a conventional example. In the drawing, each axis is proposed by graphing a relationship of the conversion coefficients each obtained by performing the color matching experiment for each color. Each of reference numerals k
1
, k
2
and k
3
denotes the conversion coefficient for each color. As can be understood from the drawing, it can be seen a dispersion (or incoincidence) among the conversion coefficients calculated for the respective colors. Further, such the dispersion is also generated due to the color which is subjected to the color matching experiment, a size of a sample which is subjected to the color matching experiment, a difference in background color and the like.
In case of actually managing the image, changing of the conversion coefficient for each color by using such the method is corresponding to changing of the conversion coefficient for each pixel, so that it is very difficult to do so.
Further, in order to solve the above problem which is due to the difference in the modes between the light source color and the body color, it is conventionally used a method shown in FIG.
13
.
That is, conventionally, there has been provided a sensor for sensing or detecting an ambient light or the like, and thus a color conversion has been performed by using ambient light information obtained from the sensor.
In such a conventional example, since a correction is performed by using the ambient light information obtained from the sensor which detects an environment light in case of observing the image, if there is no sensor for detecting the environment light in input and output devices such as a monitor, a printer and the like, the above method shown in
FIG. 13
cannot be applied.
SUMMARY OF THE INVENTION
The present invention is being made in consideration of the above problems, and thus an object of the present invention is to be able to match color sight between a body color and a light source color with each other, with simple structure.
Concretely, the object of the present invention is to easily obtain conversion parameters which are used in a signal process, so as to match the color sight between the body color and the light source color with each other.
Another object of the present invention is to provide a signal conversion method between the body color and the light source color which method is applicable even in case of observing an image by using an input/output device which does not have any sensor for sensing or detecting an environment light.
In order to achieve the above objects, the present invention provides an image processing method for obtaining the conversion parameter to be used for a signal conversion process between body color image data and light source color image data, the method comprising the steps of:
calculating the conversion parameter to match the color sight between the body color and the light source color with each other, for each of a plurality of representative colors; and
calculating the conversion parameter to be used for the signal conversion process, on the basis of the plurality of the conversion parameters for each of the plurality of representative colors.
In order to achieve the above objects, the present invention further provides an image processing method, wherein, in order to obtain a color signal which is sensed by performing a visual observation and a color matching of the light source color and the body color,
a color matching experiment is performed for each of n colors to determine n correction coefficients (k
r
, k
g
, k
b
) for the respective n colors which are used for converting tristimulus values (X
1i
, Y
1i
, Z
1i
) of the light source color and tristimulus values (X
2i
, Y
2i
, Z
2i
) of the body color in a following equation 1-(2), and the tristimulus values of the light source color and the body color are converted by using an average value of the n correction coefficients.
(
X
1
i
Y
1
i
Z
1
i
)
=
(
X
r
X
g
X
b
Y
r
Y
g
Y
b
Z
r
Z
g
Z
b
)
(
f
(
R
)
f
(
G
)
f
(
B
)
)
equation 1-(1)
(
X
2
i
Y
2
i
Z
2
i
)
=
(
k
a
0
0
0
k
b
0
0
0
k
c
)
(
X
1
i
Y
1
i
Z
1
i
)
equation 1-(2)
In order to achieve the above objects, the present invention further provides an image processing apparatus for obtaining the conversion parameter to be used for the signal conversion process between the body color image data and the light source color image data, the apparatus comprising:
color matching mean for performing a visual color matching of the body color corresponding to white and the light source color; and
calculation means for calculating the conversion parameter on the basis of corresponding between the body color and the light source color obtained by the color matching means.
The above and other objects of the present invention will be apparatus from the following detailed description in conjunction with the attached drawings.
REFERENCES:
patent: 5444544 (1995-08-01), Oka et al.
patent: 5532848 (1996-07-01), Beretta
patent: 5814932 (1998-09-01), Matsuda
patent: 03163334A (1991-07-01), None
patent: 409093451A (1997-04-01), None
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Grant II Jerome
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