Image analysis – Color image processing – Color correction
Reexamination Certificate
1997-09-30
2003-05-20
Johnson, Timothy M. (Department: 2625)
Image analysis
Color image processing
Color correction
C382S274000, C358S001900, C358S518000
Reexamination Certificate
active
06567543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus and method for performing color correcting according to environment light, a storage medium for storing the image processing method, and an environment light measurement apparatus for measuring the environment light.
2. Related Background Art
In recent years, since color image products are widely used, a color image can be easily managed not only in a specific field such as a design production field or the like using CG (computer graphics), but also in general office. In a any case, in a case where the image formed on a monitor is outputted by a printer, since a color of the monitor image does not coincide with that of the printed image, it is difficult to perform color checking of the printed image on the monitor. Therefore, as a method to solve such a problem, a color management system has been created and remarked.
The color management system is a system for eliminating a difference in color of each device by using a common color space. This system is based on an idea that, if the colors are represented by the same coordinates in the same color space, their manifestation (or appearance) is identical. That is, in this system, all the colors are represented in the same color space and their corresponding coordinates are coincided with others to obtain coincidence in the manifestation of color. At present, as one of such systems generally used, there is a method in which the difference in color of each device is corrected by using a CIE-XYZ color space as the color space, and by using XYZ tristimulus values which are internal description coordinate values of the CIE-XYZ color space.
Hereinafter, the environment for observing the image will be explained with reference to FIG.
28
.
FIG. 28
shows a case where an image which is the same as printed matter
201
is displayed on a monitor
203
. In this case, ambient light
204
when the image is being observed is detected by an ambient light sensor
206
mounted on the monitor or the printer.
For example, the printed image or the image displayed on a CRT is not always observed in the fixed ambient light, but the ambient light
204
in
FIG. 28
varies according to an environmental situation. Further, even if color coincidence can be obtained in one ambient light, when such ambient light varies, color-coincided images come to be seen as the images completely different from others. As shown in
FIG. 27
, in order to eliminate this, by using the above color management system, it is predicted on the basis of ambient light-information
108
previously obtained by a sensor
109
what value (e.g., XYZ values) the respective images have when these images are observed in one environment. Then, these predicted values are reproduced as faithfully as possible by using profiles
103
and
104
for respective devices, whereby it intends to coincide the manifested color with others.
Such a conventional example will be explained hereinafter with reference to FIG.
27
. Initially, an input image (i.e., printed matter) is read by a scanner
101
. Then, in a scanner RGB to XYZ conversion unit
102
, R
1
, G
1
and B
1
signals obtained from the scanner
101
are converted into color signals X
1
, Y
1
and Z
1
not depending on any device, by using the scanner profile
103
in which previously provided scanner characteristic data has been stored. Further, in a signal conversion unit
104
, on the basis of the ambient light information
108
obtained from the sensor
109
for sensing the ambient light, the signals X
1, Y
1
and Z
1
are converted into color signals X
2
, Y
2
and Z
2
of each color in case of observing in such ambient light. Then, in an XYZ to monitor RGB conversion unit
105
, monitor input values, i.e., R
2
, G
2
and B
2
signals, are calculated by using the monitor profile
106
and inputted to the monitor
107
.
In the above conventional method, if the two colors have the same value in the common color space, they should be seen as the same. However, in a case where the color displayed on the monitor is compared with the color obtained by illumination (e.g., color on printed matter), it has been conventionally known that, even if these two colors have the same value, they can not be seen as the same by an observer. For this reason, in order to perceive or observe these two colors as the same by the naked eye in the above environment, further correcting is necessary.
In case of the printer, the profile can be obtained by adding various image data to the target device, measuring the color of the output image from the target device, and forming a table in which the various image data respectively correspond to the color-measured values. However, since it is assumed that environment illumination light in case of forming the profile has a value of standard illumination light which is determined by CIE and has spectral intensity as shown in
FIG. 16
, color change ratio of the CRT becomes different from that of the printed matter if the environment illumination light varies, whereby the colors on the CRT and the printed matter are observed as being different from each other. Therefore, in case of performing strict color matching, it is necessary to make the standard illumination light and the environment illumination light substantially the same when the profile is formed, and to measure a kind of the environment illumination light to further add a color correction process.
SUMMARY OF THE INVENTION
In case of observing colors, it is thought that a human being considers white as a standard color and thus recognizes all colors by comparing them with white. In this connection, it will be thought an example that a displayed image on a monitor and an image on printed matter both placed in one ambient light (i.e., environment light) are observed.
In such environment, there are many colors which are considered (or can be perceived) as white, e.g., white on the monitor, white in illumination light, white in an image (or paper) illuminated by the illumination light, and the like.
In a case where there are many colors which can be perceived as white in observation environment, an observer in such environment obtains the white acting as the standard when observing the color, by collecting perception as to the above-described whites in the many environments (i.e., white on the monitor, white in illumination light, white in an image (or paper) illuminated by the illumination light, and the like). At this time, the white perceived on the printed matter (i.e., white of the image (or paper) illuminated by the illumination light) and the white on the monitor highly affect the case of obtaining the standard white by collecting the perception, as compared with another white. For this reason, even if the identical illumination light is used, if the white (i.e., chromaticity value) of the paper used when obtaining the printed matter (i.e., hard copy) differs, also the standard white when observing the color highly differs.
Therefore, an object of a first invention is to realize highly accurate matching by performing color signal converting on the basis of the white of a recording medium and the white of the environment light.
In order to achieve the above object, the first invention provides an image processing method for performing the color signal converting on image data to make identical of color sight on a displayed image and color sight on an image formed on the recording medium, comprising the steps of:
obtaining information as to the white which is perceived on the formed image illuminated by the environment light, on the basis of information as to the recording medium and information as to the image processing environment light; and
performing the color signal converting by using the information as to the white obtained in the obtaining step and the information as to the white on a display device.
Further, the paper or ink which is the base material of the output printed matter tends to use a fluorescent whitening agent to improve
Hidaka Yumiko
Mizuno Toshiyuki
Shiraiwa Yoshinobu
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