JPH10173943A - Color correcting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and precisely correct a color match between a hard copy image and a soft copy image by visually comparing the patch of the hard copy image and the soft copy image which has colorimetric values from the observation position of an observer, and repeating the correction until the same color is seen. SOLUTION: The color patch of an image 12 of a hard copy image 14 on an observation table 16 and the color patch of a display soft copy image 20 on a CRT of the observation table 26 are viewed with the eye 28 of the observer. When the color tone of the color patches of the image 12 and display soft copy image 20 are not seen equally, a adjusting means is adjusted repeatedly by the hand 29 of the observer until they are seen equally. Environmental light for this observation includes reflected light 19b projected by the patch of the hard copy image 12, diffused light from an observation light source 18, and external diffused light. Further, even when the software copy image 20 is viewed, the light includes light 23a projected by the display screen 21 of the CRT 22, reflected light 23b which is projected by the observation light source 18 and reflected, and other external diffused light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard copy image such as a photograph or a printed matter and a soft copy image displayed on a self-luminous recording medium such as a CRT display device or a liquid crystal display device. The present invention relates to a color correction method for correcting an error generated when color matching (color matching) is performed by colorimetric matching.

[0002]

2. Description of the Related Art Conventionally, in the printing field, prior to main printing, which produces a large amount of printed matter on a printing press, the expected finish of the printed product is required for color proofing of the printed product obtained in the main printing. The image is displayed as a pre-proof on a display device such as a CRT, and is exposed and developed on various photosensitive materials such as a diazo photosensitive material, a photosensitive resin (photopolymer) material, a silver halide photographic photosensitive material and an electrophotographic photosensitive material. Alternatively, the image is reproduced as a pre-proof (color proof) by a photographic method in which transfer is performed, or proof printing is performed using a proofing machine.

A hard copy image such as a proof print or a photo proof color proof used for color proofing is finally used as a sample of a printed product for obtaining the printing permission of an orderer. Attempts are made to get as close as possible to press printing. For this reason, especially for proofs that are the most similar in quality to be performed by the printing method like printed products,
Although printing is performed in the same way using the same halftone dot as this machine printing, using the same ink and the same paper, since various phenomena such as trapping and dot gain are different, basically perfect color matching (Color matching) cannot be obtained.

[0004] The same applies to a photographic method for obtaining a color proof by a photosensitive method, in which a printing image is reproduced using the same ink and the same paper with the same halftone type color printer as the printing machine. However, since this is an image reproducing method different from the printing method, there is a problem that perfect color matching is more difficult. For this reason, conventionally, the color proof by the photosensitive system is often used as a pre-proof for internal production management, rather than as a sample of a printed product for the orderer. On the other hand, a soft copy image displayed on a display device such as a CRT is displayed in an image reproduction method completely different from a printing method, and thus is used not as a sample of a printed product but as a pre-proof for internal production management. .

However, in recent years, in the printing field by the introduction of a color management system, color matching is not attempted by using a print product sample as close as possible to a print product as in proof printing. Attempts have been made to match the color appearance (Color Appearance) with eyes. This approach is not only for color matching between printed products and hard copy images of different materials such as color proofing by photographic methods, but also between printed products and hard copy images such as display images on CRTs and soft copy images. But it has been done. On the other hand, in recent years, personal computers and the like have been able to easily generate color images or capture images from printed materials and photographs to easily perform desired image processing and color processing. The color of the soft copy image displayed on the display device does not match the color of the hard copy image output by the color printer. It has been done.

Here, a number of color matches between printed matter and hard copy images such as color photographs and color copies have been proposed.
As for color matching with a soft copy image displayed on a liquid crystal display or a liquid crystal display, a simple and sufficient color matching method has not been established.

When a color image is recorded in an image output device such as a color printer or a printing machine, R (red), G (green), B (blue), C (cyan), M
(Magenta), Y (yellow), C, M, Y, K (black)
By controlling the color image data according to the above, a color image having a desired color can be obtained as a hard copy image.
However, since such color image data depends on the output characteristics of the hard copy image of the image output device, when outputting to an image output device having different characteristics, the color conversion process of the color image data is performed in consideration of the characteristics. Need to do. This is more remarkable in an image display device such as a CRT.

For this reason, the color image data consisting of C, M, and Y is independent of the image output device, for example, the tristimulus values (X, Y, Z) of the CIEXYZ color system specified by the International Commission on Illumination (CIE). And image data such as CIEL ^* a ^* b ^* color system lightness index L ^* (brightness) and perceived chromaticity index a ^* , b ^* (hue and saturation), and convert the colors of these color systems. If there is the same image data in space, there is a method in which color matching can be achieved at the colorimetric value level, regardless of the image output device that outputs an image corresponding to this image data. However, the appearance can be matched by matching at the colorimetric value level in the case of hard copy images, and basically, except for special cases, the hard copy image and the soft copy image are used. However, it was not possible to obtain a safe appearance match even when matching at the colorimetric value level.

By the way, color matching (color matching) between a hard copy image and a soft copy image can be achieved when the colorimetric values of both images match under a specific environment. This specific environment is, for example, a display image displayed on a CRT as a soft copy image as a representative example, in a completely dark room, the observation light is applied only to the hard copy image, and the soft copy image and the human eyes do not. It is an environment that does not enter directly. To match both colorimetric values means, for example, chromaticity x, y and tristimulus values X,
Y, Z, here the luminance Y, ie (x, y,
Y).

[0010]

However, even when the two colorimetric values are matched in a specific environment as described above, color matching cannot be obtained due to the following points. There was a problem that there is. 1) If a fluorescent material is included in a support such as a photosensitive material or paper for recording a hard copy image, the reflectance of light changes, which affects the colorimetric value, and the observation light source For example, if there is an influence of a fluorescent excitation component of a fluorescent lamp, the colorimetric value is also affected. 2) Fluctuations, especially long-term fluctuations and fading, are inevitable for CRTs that output soft copy images, and even if calibration is performed for printing machines and color printers that output hard copy images, Long-term fluctuations and fading are inevitable.

Further, even if color matching (color matching) is obtained in the specific environment described above, when brought into a general environment and observed, the colors may not match visually due to the following points. There was a problem. 3) For the observation light source assumed to calculate the colorimetric value,
The illumination light of the actual observation light source is slightly shifted due to, for example, manufacturing variations even for the same kind of light source, and there is a difference between the two, especially including the difference in the fluorescence excitation component of the observation light source. 4) When external light is incident on the surface of the emitting CRT, the light emitted from the surface of the CRT, particularly the black portion, becomes brighter due to its reflection, the color changes, and the gradation changes. . 5) The color temperature of an observation light source of a hard copy image, for example, a general fluorescent lamp is 3000K to 6000K, and the color temperature of a CRT for displaying a soft copy image is about 9300K, while the color temperature of an extremely high color is about 7000K. There is a so-called color adaptation, in which, depending on the color temperature at which the human eye adapts, the way in which colors are perceived differs depending on the difference in color temperature between the two.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a conventional colorimetric matching between a hard copy image such as a printed matter or a color photograph and a soft copy displayed on a display device such as a CRT or a liquid crystal. It is an object of the present invention to provide a color correction method capable of correcting an error generated when color matching is performed and a mismatch between color appearance (color appearance) by human eyes.

[0013]

In order to achieve the above object, the present invention relates to a method for converting a soft copy image output on a self-luminous recording medium into a hard copy image output on a non-self-luminous recording medium. At the time of performing color correction for matching the colors of the above, at least one patch is output as the hard copy image, and a colorimetric value matching the color of the patch of the hard copy image in the colorimetric reference color space is output. Outputting color patches in the same manner as the soft copy image,
The output hard copy image patch and the soft copy image patch are visually compared from the observer's observation position, and when the colors of the output hard copy image patch and the soft copy image patch look different, For at least one of the images, output a patch having a colorimetric value slightly shifted from the coincident colorimetric value, and visually compare the output color of the patch of the hard copy image and the color of the patch of the soft copy image. Is repeated until the image looks the same, and color correction of at least one of the hard copy image and the soft copy image is performed based on the colorimetric values of the patches of the hard copy image and the patches of the soft copy image that look the same. The present invention provides a color correction method characterized by the above.

The at least one patch is one patch of white, two patches of white and black, or at least three patches of white, black and at least one intermediate gray, Alternatively, it is preferable that the patch further includes at least one chromatic color patch.

Preferably, the self-luminous recording medium has a movable hood for suppressing softening of the soft copy image due to reflection of external light. Further, in the color correction, in order to suppress softening of the soft copy image due to reflection of external light of the self-luminous recording medium, gradation is performed by Y expansion and contraction in the XYZ color system that is the colorimetric reference color space. Preferably, the adjustment is performed.

The present invention is also directed to performing color correction for matching colors between a soft copy image output on a self-luminous recording medium and a hard copy image output on a non-self-luminous recording medium. A color correction method, characterized in that the self-luminous recording medium has a movable hood for suppressing softening of the soft copy image due to reflection of external light. It is.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color correction method according to the present invention will be described in detail below based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a schematic view showing an embodiment of an apparatus for implementing the color correction method of the present invention. As shown in the figure,
The color correction apparatus 10 that implements the color correction method of the present invention includes a hard copy 14 in which a color patch used in the color correction method of the present invention is recorded as a hard copy image 12 and an image 12 of the hard copy 14 at an observation position. , A viewing light source 18 illuminating the hard copy image 12, and a color patch having a colorimetric value that matches the color of the color patch of the hard copy image 12 in the colorimetric reference color space. Display device (hereinafter referred to as CR) having a display screen 21 for displaying
T) 22 and soft copy image 2 on CRT 22
And a computer 24 for controlling the display of the C.O. and performing calculations necessary for implementing the color correction method of the present invention.
The apparatus includes a soft copy image observation stand 26 for arranging the soft copy image 20 displayed at T22 as a set with the computer 24 at an observation position, and a printer 30 for outputting the hard copy 14 on which the hard copy image 12 is recorded.

In the color correction method of the present invention, the observation table 1
The color patch 12a of the image 12 of the hard copy 14 arranged on the monitor 6 and the color patch 20a of the display soft copy image 20 of the CRT arranged on the observation table 26 are visually observed by the observer's eyes 28 in the presence of ambient light. If the colors of the color patch 12a and the color patch 20a do not look the same, for example, the color of the color patch 20a displayed as the soft copy image 20 on the display screen 21 of the CRT 22; As shown in FIG. 2B, the color adjustment means (GUI; displayed together with the patch 20a)
The graphic user interface (also referred to as a slider bar or button) 32 is manipulated with the observer's hand 29 using a keyboard or a mouse (not shown) to change little by little, A patch 20a of a color having a colorimetric value slightly shifted from the corresponding colorimetric value in the colorimetric reference color space is output, and the color of the patch 20a of the newly displayed soft copy image 20 and the patch 12a of the hard copy image 12 are output. Are repeatedly observed with the observer's eyes 28 in the presence of ambient light until the color of the patch 20a looks the same as the color of the patch 12a.

In the color correction method of the present invention, FIG.
A hard copy image 12 is added to a hard copy 14 shown in FIG.
The patch (color patch) 12a recorded as a patch and the patch 20a displayed as the soft copy image 20 on the display screen 21 of the CRT 22 shown in FIG. 2B are corrected so that they look the same color. 12 and 2
When one patch 12a and 20a is used for each of the 0, the colors of these patches 12a and 20a are achromatic,
Preferably, the color is white.

In the present invention, one hard copy image 12 and one soft copy image 20 are assigned to each.
The number of patches 12a and 20a is not limited to two, and two patches 12a, 12b and 20
a, 20b, patches 12a and 20a are white,
The patches 12b and 20b may be black or, although not shown, at least three patches of at least one kind of intermediate gray (gray) in addition to these white and black. Further, the patch used in the present invention may be a patch including a color.

In general, depending on which of the hard copy image 12 and the soft copy image 20 is observed for a longer time, the same color may appear different due to chromatic adaptation. However, in the present invention, since the color appearance of the patches 12a and 20a of the two images 12 and 20 is determined by the observer's eyes 28, the correction including the color adaptation can be made. Therefore, in the present invention, the background color and the tint adjusting means 32 of the image described above are not necessarily adjusted to a color that is unlikely to cause chromatic adaptation, that is, a chromatic color that is significantly different in chroma (chroma) from black or achromatic color (gray). For example, it is not necessary that the background is black and the tint adjusting means 32 is a black tone, and characters and symbols need not be chromatic colors with high saturation as much as possible. It goes without saying that the colorimetric matching and the visible color matching may be achieved by eliminating the above.

The hard copy image 12 is not particularly limited as long as it is an image recorded on the non-self-luminous recording medium of the present invention, that is, an image that requires an observation light source for observation. , A photograph, a color copy by a color copying machine, and the like. Examples of the non-self-luminous recording medium include printing paper, photographic printing paper, and copy paper. The printer 30 that outputs the hard copy 14 on which the hard copy image 12 is recorded is not particularly limited, and examples thereof include conventionally known printers such as a printing machine, a copying machine, and a photographic printer. On the other hand, the soft copy image 20 may be any image displayed on the self-luminous recording medium of the present invention.
The present invention is not limited thereto, and is not particularly limited as long as a separate observation light source is not required for observing a display image by self-emission, and a liquid crystal display (LCD), a plasma display, or the like may be used.

A contact type sensor for measuring the chromaticity and absolute luminance of a white point of a self-luminous CRT monitor and a white color of a print paper for printing a hard copy image as disclosed in Japanese Patent Application Laid-Open No. 7-222196. A contact-type sensor or the like that measures the chromaticity of a point cannot be used in the present invention because it cannot simultaneously measure ambient light and the like.
In the method disclosed in the publication, in addition to the above-described contact type sensor, a visual environment parameter as a numerical value corresponding to a visual environment of a CRT monitor (an environment for observing a soft copy image displayed on the CRT monitor) is output. A sensor such as a radiance colorimeter that measures the chromaticity of the ambient light (fluorescent light) in the environment where the CRT monitor is installed and the chromaticity of the white point of the ambient light in the environment where the hard copy image is viewed However, this method does not correct for differences between colorimeters in measuring the chromaticity and luminance of the hard copy image and the soft copy image itself and the chromaticity of ambient light in the visual environment, In a strict sense, particularly at the level of color matching required in the printing field, there are problems such as the need to match at least the difference between the colorimeter for hard copy images and the colorimeter for soft copy images. . Further, the present invention corrects the colorimetric value of a hard copy image and the colorimetric value of a soft copy image, including differences in colorimeters and fluctuations in an output image. The invention combines the colorimetric values of both images using the adaptation model proposed there,
It is not a technique for correcting both colorimetric values, and it can be said that the technique is based on a technique (approach) completely different from the present invention. There is also a problem that the proposed adaptation model cannot be applied to all proposals.

On the other hand, in the present invention, the patch 2
The observer's eyes 2
As shown in FIG. 1, when the patch 12a of the hard copy image 12 is visually observed, the illumination light 19a from the observation light source 18 is reflected light reflected by the patch 12a of the hard copy image 12, as shown in FIG. Not only 19b but also environmental light (not shown) such as diffused light in the observation system from the observation light source 18, diffused light from the display screen 21 of the CRT 22 and diffused light from outside the system. The observation environment should be such that it can be visually observed with the eyes 28. Also, when viewing the patch 20a of the soft copy image 20, the CRT 2
Light 23 emitted from the patch 20a of the second display screen 21
a, reflected light 23 b emitted from the environment light, for example, the observation light source 18 and reflected on the display screen 21 of the CRT 22.
And an observation environment in which diffused light from the inside and outside of the observation system and the like simultaneously enter the eyes 28 of the observer.

Computer 2 used in the present invention
Numeral 4 is for controlling not only the display of the soft copy image 20 on the CRT 22 but also for performing the calculations necessary for performing the color correction of the present invention. As shown in FIG. CMY (K) data, which is data (DDD; Device dependent data) dependent on a color system device (input / output device), is converted into a colorimetric reference color space, CIEX.
A color space conversion unit 3 for converting a color space into stimulus value data X ₁ Y ₁ Z ₁ which is data (DID; Device Independent Data) independent of a device (input / output device) of the YZ color system.
4 and the stimulus value data X ₂ Y ₂ Z ₂ for displaying the same white patch 20 a as the patch 12 a of the hard copy image 12 as the soft copy image 20 on the CRT 22 from the stimulus value data X ₁ Y ₁ Z ₁ Color correction calculator 3
6, a color conversion unit 38 for converting the stimulus value data X ₂ Y ₂ Z ₂ into RGB data of RGB color system,
A CRT control unit 40 for controlling the display of the CRT 22 based on the data.

The CRT control unit 40 is provided on the display screen 21
The color adjustment means 32 is displayed together with the patch 20a.
The observer operates the color adjustment means 32 of the
The color (color) of 20a can be changed little by little and displayed.
Patch 20a that is displayed in different colors
Color of RGB data R_SG_SB_STo the color converter 38
Can be output. In addition, the color conversion unit 38
R of the change display patch 20a output from the control unit 40
GB data R_SG_SB_SStimulus value (colorimetric value) data X_S
Y_SZ_SIt also has the function of inverting to. In addition, the present invention
The hard copy image obtained by the color space conversion unit 34
Stimulus value data (X ₁, Y₁,
Z₁) To the colorimetric value (X_H, Y_H, Z_H) And it is sufficient. Book
The color correction apparatus 10 that implements the color correction method of the present invention is basically
The configuration is as described above.

In the color correction method of the present invention, the colors of the patches 12a and 20a that are to be made the same color for color correction in both the hard copy image 12 and the soft copy image 20 are white, and the color of the soft copy image 20 is Will be described below with reference to the flowchart shown in FIG. 4 as a typical example of matching the color of the hard copy image 12 with the color of the hard copy image 12. First, as shown in FIG. 4, CMY data of a predetermined color, for example, (C, M, Y) =
A hard copy 14 having a white patch 12a (0, 0, 0) as a hard copy image 12 is output. Note that a desired white patch 12a is used as a hard copy image.
When the hard copy 14 having the following is prepared in advance, the output by the printer 30 and therefore the printer 30 is unnecessary.

Next, the color space conversion unit 3 of the computer 24
4, the patch 12a of the hard copy image 12
CMY data which is data (DDD) depending on the device
Data (DID) independent of data
Stimulus value data XYZ in colorimetric reference color space (CIEXYZ)
Is set in advance in the hard copy image 12, for example.
Specific color space conversion look-up table LUT_HRAnd strange
Color space conversion is performed using a substitution formula. At this time, the hard copy image
Stimulus value data XYZ = (X₁, Y₁, Z₁)so
Suppose there was. This stimulus value data (X₁, Y₁, Z₁)
Is the colorimetric value (X _H, Y_H, Z_H).

On the other hand, the soft copy image 20
The stimulus value data XYZ of the patch 20a displayed as
₂ , Y ₂ , and Z ₂ , the color correction calculation unit 36
(X ₂ , Y ₂ , Z ₂ ) = (X ₁ , Y ₁ ,
Z ₁ ). The color correction calculation unit 36 calculates (X _H , Y
_H, Z _H) is maintained. The computer 24 uses the color converter 38 to display the CR to be displayed based on the stimulus value data XYZ = (X ₂ , Y ₂ , Z ₂ ) obtained by the color correction calculator 36.
T22 in a unique DDD data, for example, RGB data, color conversion, for example using a specific color set in advance in the soft copy image 20 conversion lookup table LUT _SN or conversion formula. Assume that the RGB data thus obtained is normalized to, for example, 8-bit data and (R, G, B) = (255, 252, 249). Therefore, the CRT 22 is connected to the C
The RGB data is received from the RT control unit 40 and is displayed on the display screen 21 as a soft copy image 20 (R, G,
B) Display a white patch 20a with = (255, 252, 249). Although the effect of the chromatic adaptation is not corrected here, the color matching between the two images 12 and 20 is determined by visual observation by the observer's eyes 28, so that the correction is performed including the chromatic adaptation.

The patch 12a of the hard copy image 12 and the patch 20a of the soft copy image 20, which have the same stimulus value data output as described above and have the same white color, are observed by the observer at the observation position in the presence of ambient light. Observed by eye 28 and compared. At this time, both patches 12a and 20a often do not appear to be the same color to the human eye for various reasons described in the prior art. That is, there is often no appearance color match between the two. Here, while observing the patch 20a displayed on the display screen 21 with his eyes 28, the observer slightly operates the tint adjusting means 32 displayed on the display screen 21 with his hand 29 (for example,
The color of the patch 20 a displayed on the display screen 21 by the CRT control unit 40 of the computer 24 is gradually changed by changing the RGB data to (R _S , G _S , B _S ). At this time, since the observer visually compares the color of the patch 20a whose color is changed and the color of the patch 12a of the hard copy image 12, this operation is performed so that the colors of the patches 20a and 12a match. Repeat until.

When the colors of the patches 20a and 12a look the same, the RGB data of the patch 20a of the soft copy image 20 is converted into (R _S , G _S , B _S ) by the CRT control unit 40.
Assume that Thereafter, the color conversion unit 38 of the computer 24 receives the RGB data (R _S , G _S , B _S ) of the patch 20 a from the CRT control unit 40 and, for example, receives the CRT 2
2 color space conversion lookup table LUT _SR
Is inversely converted into the stimulus value data XYZ using a conversion formula.
At this time, the stimulus value data XYZ = patches 20a softcopy image _{20 (X S, Y S,} Z S) and was converted to. The stimulus value data (X _S , Y _S , Z _S ) is input from the color converter 38 to the color correction calculator 36. as a result,
In the color correction calculation unit 36, for example, the hard copy image 12
The colorimetric values of the patches 12a X _H, Y _H, a Z _H, colorimetric values of patches 20a softcopy image 20 is X _S, Y
_S, can be regarded as a Z _S.

The two colorimetric values (X_H, Y_H,
Z_H) And (X_S, Y_S, Z_S) Using softco
Color correction can be performed on the p-image 20. For example,
Color of the patch 20a of the soft copy image 20, for example, white
Is the color of the patch 12a of the hard copy image 12, for example,
To match the white color, the color correction of the computer 24 is performed.
In the calculation unit 36, the patch 1 of the hard copy image 12
2a colorimetric value (X_H, Y _H, Z_HThe sting used to obtain
Extreme value data (X₁, Y₁, Z₁) Against soft copy
ー Package to be displayed on the CRT display screen 21 as the image 20
Stimulus value data (X_Two, Y_Two,
Z_Two) Is the colorimetric value at which color matching by the eyes 28
(X_H, Y_H, Z_H) And (X_S, Y_S, Z_S)use
Therefore, the stimulus value data (X₁, Y₁,
Z₁) To stimulus value data (X_S・ X₁/ X_H, Y_S・ Y
₁/ Y_H, Z_S・ Z₁/ Z_H). X_Two= (X_S/ X_H) ・ X₁ Y_Two= (Y_S/ Y_H) ・ Y₁ Z_Two= (Z_S/ Z_H) ・ Z₁ ... (1)

The soft copy image 2 thus corrected
0 color patches 20a of, if Mirere in colorimetric value level before correction colorimetric values _{(X H, Y H, Z} H) colorimetric values after the correction from the (X, Y, Z) is (X _S , Y _S , Z _S ), and the color observed by the observer under the observation environment matches the color of the patch 12a of the hard copy image 12. That is, color matching of the appearance by the human eyes is obtained. The relational expression (1) for obtaining a color match in this manner is stored in the color correction calculation unit 36 of the computer 24, and the image data (C, M, Y, and therefore X ₁ , Y
₁ , Z ₁ ) and image data (R,
By correcting G, B, and therefore X ₂ , Y ₂ , Z ₂ ) using the above-mentioned relational expression (1), it is possible to achieve color matching between the two images 12 and 20. The procedure of the color correction may be similarly performed by using the image data of the hard copy image 12 instead of the patch 12a and using the image data of the soft copy image 20 instead of the patch 20a in the above-described color correction method.

It should be noted that the stimulus value data (colorimetric values) (X _H , Y _H , and X _H ) of the patches 12 a and 20 a of the white hard copy image 12 and the soft copy image 20 that look the same.
Z _H ) and (X _S , Y _S , Z _S ), the color correction method for realizing the color matching of the appearance uses the input stimulus value data (X ₁ , Y ₁ , Z ₁ ) as X _S / X _{The method} is not limited to the example of multiplying by _H, but a method of recreating the color conversion look-up table LUT _SN and the conversion formula, and Japanese Patent Application Laid-Open No.
Reference white (X _S , Y
_S, Z _S CIEL from the color space based on) ^* a ^* b ^* reference white (X _H through the color space, Y _S, such a method may be used to convert a color space based on Z _S), known Method can be adopted. In the present invention, the colorimetric values (X _S , Y _S , Z _S ) and (X _H ,
Y _H, as long as to obtain the same effect by using a Z _H),
The color conversion look-up table LUT _SN and the conversion formula are not particularly limited, and are not particularly limited.
The color conversion method disclosed in Japanese Patent No. 56555 may be used, or a conventionally known method may be used.

In the above-described example, the color of the soft copy image 20 is corrected so as to match the color of the hard copy image 12 so as to realize the match between the appearance colors of the two. The present invention is not limited to this, and conversely, color correction may be performed so that the color of the hard copy image matches the color of the soft copy image 12, and color matching between the two may be performed. In this case, the patch 2 displayed on the display screen 21 of the CRT 22
0a is converted into stimulus value data XYZ using, for example, a color space conversion look-up table LUT _SR or a conversion formula specific to the CRT 22, and a color conversion look-up table specific to the printer 30 is obtained from the data XYZ.
The color conversion into the CMY (K) data is performed using the LUT _HN or the conversion formula, and the white patch 12 to be the same white as the patch 20a is output from the printer 30 using the CMY (K) data.
The hard copy image 12 having a may be output. Thereafter, the colorimetric values (X _H , Y _H , Z _H ) of the patch 12a and the colorimetric values (X _S , Y _S , Z _S ) of the patch 20a that have been recognized as the same white color by the observer's eyes 28. And the stimulus value data (X ₁ , Y ₁ , Z ₁ ) of the hard copy image 12 using
May be subjected to color correction.

Further, the patch 1 of the hard copy image 12
When the white stimulus value data XYZ to be recorded or displayed on the patch 2a of the soft copy image 20 and the patch 20a of the soft copy image 20 are obtained in advance, the stimulus value data XYZ is converted to CMY using a color conversion lookup table or a conversion formula. (K) The data may be converted into data or RGB data, and the hard copy image 12 may be output from the printer 30 using the data and the soft copy image 20 may be displayed on the CRT display screen 21. Also, CMY (K) data and RG
The method of converting the B data into the stimulus value data XYZ and its inverse conversion is not limited to the above-described lookup table or the conversion formula, and uses a 3 × 3 matrix or three one-dimensional lookup tables. Known color conversion methods including a method and a method using a combination thereof can be adopted.

Next, in the above example, the hard copy image 1
2 and soft copy image 20 as patches
Using the same white patches 12a and 20a.
However, the present invention is not limited to this.
Switches 12a and 20a plus the same black patch 12
b and 20b may be used. in this case
Are identified as the same white color by the observer's eyes 28
The colorimetric values (X_H, Y_H,
Z_H) And (X_S, Y_S, Z_S) Besides the observer's eyes 2
Patches 12b and 12 that have been certified to be the same black by 8
And 20b (X_HD, Y_HD, Z_HD)and
(X_SD, Y_SD, Z_SD) Can be obtained,
Match the reference white of the image 12 with the soft copy image 20
Not only can the die from standard white to black
You can also match the natural range. in this case,
For example, the stimulus value data of the corrected soft copy image 20
(X_Two, Y _Two, Z_Two) Shows the stimulus value data X in FIG.
As is clear from the graphs given above,
It is. X_Two= (X_S-X_SD) (X₁-X_HD) / (X_H-X_HD) + X_SD Y_Two= (Y_S-Y_SD) (Y₁-Y_HD) / (Y_H-Y_HD) + Y_SD Z_Two= (Z_S-Z_SD) (Z₁-Z_HD) / (Z_H-Z_HD) + Z_SD ... (2)

In the present invention, a hard copy image
As a patch for the image 12 and the soft copy image 20, white
Color (12a, 20a) and black (12b, 20b)
In addition, at least one intermediate gray may be used.
No. In this case, for example, a patch of intermediate gray
Corresponds to two cases (X_HG1, Y_HG1, Z
_HG1) And (X_SG1, Y_SG1, Z_SG1),and
(X_HG2, Y_HG2, Z_HG2) And (X_SG2, Y_SG2, Z
_SG2), So that the reference white, black and its die
In addition to the natural range, it is possible to match the gradation
You. Stimulation of the corrected softcopy image 20 in this case
Value data (X_Two, Y_Two, Z_Two) Indicates only stimulus value data X
It is clear from the relationship schematically shown by the dotted line in FIG.
Like, white and the first (close to white) intermediate gray
Between the first and second (near black) intermediate gray,
The above equation between the second intermediate gray and black respectively
It is given by a relational expression similar to (2). For example, white
The following expression is used between the color and the first intermediate gray.
Is done. The other parts are the same, and will not be described. X_Two= (X_S-X_SG1) (X₁-X_H) / (X_H-X_HG1) + X_S Y_Two= (Y_S-Y_SG1) (Y₁-Y_H) / (Y_H-Y_HG1) + Y_S Z_Two= (Y_S-Y_SG1) (Y₁-Y_H) / (Y_H-Y_HG1) + Y_S ... (3)

Further, in the present invention, the patches of the hard copy image 12 and the soft copy image 20 are used as patches.
Although not shown, a color patch, that is, a chromatic color patch may be used. By the way, when color patches are used, the linear relationship unlike the case of using white, black, and intermediate gray patches is not maintained, so that the observer can use a 3 × 3 matrix, a three-dimensional lookup table, three-dimensional interpolation, or the like. The colorimetric values (X, Y, Z) of the patches of the images 12 and 20 whose colors have been matched by the eyes 28 are matched to the corrected stimulus value data (X ₂ , Y ₂ , Z ₂ ) may be obtained. The color patch is preferably used together with the above-described white, black, and at least one kind of intermediate gray, but the present invention is not limited to this, and the color patch may be used alone or with at least one of these achromatic colors. It is also possible.

By the way, the color of the patch used in the method of the present invention,
Therefore, as the number increases, items that can be matched, for example, reference white, black (dynamic range), gradation, chromaticity, etc. increase, and the accuracy of color matching of the appearance of the hard copy image and the soft copy image also increases. The output of at least one of a hard copy image and a soft copy image in which the color of the patch is slightly changed until the color of the patch is matched by the observer's eyes 28 and the observation and calculation processing are increased, resulting in increased labor. As a result, simplicity is lost. Therefore, the number of patch colors in applying the method of the present invention may be appropriately selected according to the application.

In the above-described example, as shown in FIG.
Stimulus value data (X ₁ , Y ₁ , Y ₁ ) obtained by converting the color data (C, M, Y) of the patch
Z ₁ ) and the stimulus value data (X ₂ , Y ₂ , Z ₂ ) of the patch 20 a of the soft copy image 20 by the color correction calculation unit 36 are equalized, and the obtained stimulus value data (X ₂ , Y ₂ , Z) ₂ ) is converted into RGB color data (R, G, B) by a color conversion section 38, and a patch 20a is displayed as a soft copy image 20 on a CRT display screen 21 by a CRT control section 40, and the color of the displayed patch 20a Is changed little by little to determine the color of the patch 20a of the displayed soft copy image 20 and the color of the patch 12a of the hard copy image 12 with the eyes 28 of the observer. The color data (R _S , G _S , B _S ) of the patch 20 a is returned from the CRT control unit 40 to the color conversion unit 38 and color-converted to obtain stimulus value data (X _S , Y _S , Z _S ). Return the color correction to the calculation unit 36 as the colorimetric value It allows color correction relational expression between the two images 12 and 20, for example, the relational expression (1) is intended to obtain such. However, the present invention is not limited to this.

The structure of the computer 24 used in the present invention
The configuration shown in FIG. 6 is used instead of the configuration shown in FIG.
Is also good. The configuration of the computer 24 shown in FIG.
Color conversion unit 38 and CRT control unit 4 of the computer 24 shown in FIG.
Conversion of RGB data to RGB data between 0
A color correction unit 46 is provided.
Except that a color correction unit 46 is provided.
Therefore, since the configuration is the same as that shown in FIG.
Have the same reference numerals and their description is omitted. As shown in FIG.
The color correction calculation unit 36 of the computer 24
-Stimulus value data of image 20 (X_Two, Y_Two, Z_Two)
Stimulus value data (X ₁, Y₁, Z₁)
Any color that has the function of making it equal to
The conversion unit 38 outputs the stimulus value data (X
₁, Y₁, Z₁) If it can be converted using
Good.

The color correction section 46 uses the stimulus value data (X, Y, Z) (= (X ₂ , Y ₂ , Z ₂ ) = (X ₁ ) corresponding to the image data of the hard copy image 12 in the color conversion section 38. , Y
_1, Z ₁₎ RGB data converted from) (R _1, G _1,
B ₁ ) is converted to RGB data (R ₂ ,
G ₂ , B ₂ ), and each of R, G, B is 1
And a total of three one-dimensional lookup tables. Of course, the color correction unit 46
The color data (R ₂ , G ₂ , B ₂ ) and the color data (R ₁ , G ₁ , B) are not limited to three one-dimensional lookup tables.
Anything can be used as long as the linear relational expression between ₁ ) can be held. In this embodiment, since color correction is performed in the RGB color system, it is not necessary to return to the XYZ color system as in the example shown in FIG. R ₂ , G ₂ , B ₂ ) are converted to a color conversion unit 38.
It is not necessary to return to (X ₂ , Y ₂ , Z ₂ ).
Here, the color data (R ₂ , G ₂ , B ₂ ) and the color data (R
₁ , G ₁ , B ₁ ) will be described. Here, the patch 12 of the hard copy image 12
a, RGB, and color data (R ₁ , G ₁ ,
B ₁ ), the colorimetric value (R) of the patch 12a is obtained.
_H, G _H, B _H) and color data _{(R 1, G 1, B} 1) to.

The color correction section 46 first converts the color data (R ₂ , G ₂ , B ₂ ) into the color data (R ₁ , G ₁ , B ₁ ).
Take equal to. Obtained color data (R ₂ , G ₂ , B ₂ )
Is input to the CRT control unit 40, and the patch 20a is displayed on the CRT display screen 21 as the soft copy image 20. Then, the CRT control unit 40 changes the color data (R ₂ , G ₂ , B ₂ ) little by little until the color matching of the hard copy image 12 with the patch 12a is seen by the observer's eyes 28, and displays it. . The soft copy image 20 thus matched
Color data (R ₂ , G ₂ , B ₂ ) of the patch 20a of (R)
_S , G _S , B _S ), the patch 20
Let it be the colorimetric value of a.

The colorimetric values (R _s , G _s , B _s ) of the patch 20 a thus obtained are returned to the color corrector 46, whereby the color data (R ₂ , G ₂ , B) of the soft copy image 20 are obtained.
₂ ) and a color correction relational expression between the equivalent color data (R ₁ , G ₁ , B ₁ ) obtained from the hard copy image 12 can be expressed as follows. R ₂ = (R _S / R _H ) · R ₁ G ₂ = (G _S / G _H ) · G ₁ B ₂ = (B _S / B _H ) · B ₁ Using the color correction relational equation thus obtained. XY described above
Without returning to the Z color system, color correction in the XYZ color system can be achieved at the same time as color matching including chromatic adaptation.

By the way, in a soft copy image,
As described in 5) of the related art, there is a phenomenon in which external light is softened due to reflection on the display screen 21 of the CRT 22, that is, there is a phenomenon in which black becomes brighter and gradation is reduced, and particularly, a shadow portion is slept. In addition, since the black colorimetric value in the soft copy image 20 of the CRT 22 is affected by the above-described ambient light,
The dynamic range of the white and black colorimetric values XYZ fluctuates, and may not be consistent with the dynamic range of the white and black colorimetric values XYZ in the hard copy image 12. That is, matching the colors of the hard copy image 12 and the soft copy image 20 is performed by, for example, determining the chromaticity x, y or L ^* a ^* b ^* from the colorimetric values X, Y, Z.
It is possible by calculating and adjusting the chromaticity a ^* b ^* in the space, but when the colors are adjusted, factors related to the brightness, for example, the lightness L ^* and the luminance Y may not match.

Therefore, in order to make the colorimetric value match between the hard copy image 12 and the soft copy image 20 match the apparent color match, it is necessary to adjust the dynamic range in brightness and correct the gradation. There is. Therefore, in the present invention, as shown in FIG.
In addition, a variable hood 44 that can be moved according to external light or environmental light
May be provided so as to cover the display screen 21 of the CRT 22, and by moving the variable hood 44, the amount of ambient light incident on the display screen 21 of the CRT 22 may be adjusted to adjust the gradation. By adjusting the length of the variable hood 44, the effect of ambient light is adjusted according to the observation environment of the hard copy image 12, and the gradation of the soft copy image 20 is hardened or softened. This makes it possible to achieve color matching of the appearance including the gradation and the dynamic range of the hard copy image 12 and the soft copy image 20.

In the present invention, the CRT 2
When the correction of the gradation softening due to the reflection on the display screen 21 is performed, in addition to the adjustment by the tint adjusting means 32,
Perceptual uniform space L ^* obtained by color conversion from stimulus value XYZ
Chromaticity x (= X / (Y + Y +) obtained from stimulus value XYZ instead of L ^* (lightness) expansion (compression) at a ^* b ^*
Z)) and y (= Y / (X + Y + Z)), and the gradation is preferably adjusted by so-called Y expansion / contraction (expansion compression) that adjusts brightness by luminance Y. By the way, the relationship between the CIEXYZ color system and the CIEL ^* a ^* b ^* color system is as follows, where L ^* is lightness, a ^* and b
^* Represents chromaticity. L ^* = 116 (Y / Y ₀ ) ^1/3 −16 a ^* = 500 ｛(X / X ₀ ) ^1/3 − (Y / Y ₀ ) ^1/3 ｝ b ^* = 200 ｛(Y / Y ₀ ) ^1/3 − (Z / Z ₀ ) ^1/3 ｝

[0050] Here, as shown in FIG. 8 represents the lightness L2 lightness L ^* is compressed lightness L1 (or lightness L1 is stretched to brightness L2) is, the straight line LL ^* is L ^* compress (extension) . When this L ^* compression (expansion) is converted by the above equation, it can be represented by a curve LY, and a curve LY
Represents Y compression (expansion). As is clear from FIG. 8, since the Y compression (expansion) sets the tone of the shadow portion that falls due to the influence of external light, the tone of the shadow portion that is more noticeable than the highlight portion when observed by human eyes. Can be adjusted appropriately.

The color appearance of the hard copy image and the soft copy image (color appearance: Color Apearanc)
e) When color correction for matching is performed, not only the color correction method for appearance color matching of the present invention but also a known color correction method for the above-described gradation correction. A Y-stretching method and a background blackening method or a high-saturation chromatic coloring method for preventing color adaptation can be applied, and the effect on gradation correction and chromatic adaptation prevention is great as in the method of the present invention.

Although the color correction method of the present invention has been described in detail, the present invention is not limited to this.
Of course, various changes and improvements may be made without departing from the spirit of the present invention.

[0053]

As described in detail above, according to the present invention,
According to the conventional method, color matching between a hard copy image and a soft copy image, which may not actually match colors for various reasons, can be easily and accurately corrected. Further, according to the present invention, when performing color correction for color matching between a hard copy image and a soft copy image, the color correction can be performed including the effect of color adaptation of the human eye, and the accuracy of color matching can be improved. Can be raised. Furthermore, according to the present invention,
When performing the color correction for the color matching of the two images, the gradation correction can be performed properly. In particular, the shadow part does not stand unnaturally or fall asleep, Or not.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of one embodiment of a configuration of a color correction device that performs a color correction method according to the present invention.

FIGS. 2A and 2B are schematic explanatory diagrams of one embodiment of a hard copy image and a soft copy image used in the color correction apparatus shown in FIG.

FIG. 3 is a block diagram of one embodiment of a computer of the color correction apparatus shown in FIG.

FIG. 4 is a flowchart for explaining an example of the color correction method of the present invention in the color correction device shown in FIG. 1;

FIG. 5 is a graph illustrating an example of a color correction method according to the present invention.

FIG. 6 is a flowchart for explaining another example of the color correction method of the present invention in the color correction apparatus shown in FIG. 1;

FIG. 7 is a schematic diagram of an embodiment of a CRT display device of the color correction device according to the present invention.

FIG. 8 is a graph illustrating another example of the color correction method according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 color correction device 12 hard copy image 12a patch 14 hard copy 16 hard copy image observation stand 18 observation light source 20 soft copy image 20a patch 21 display screen 22 CRT display device 24 computer 26 soft copy image observation stand 28 observer's eyes 29 observation Hand 30 printer 32 color adjustment means (GUI) 34 color space conversion unit 36 color correction calculation unit 38 color conversion unit 40 CRT control unit 42 colorimetric value calculation unit 44 variable hood

Claims (8)

[Claims] When performing color correction to match colors between a soft copy image output to a self-luminous recording medium and a hard copy image output to a non-self-luminous recording medium, the hard copy is used. At least one patch is output as an image, and a patch having a colorimetric value that matches the color of the patch of the hard copy image in the colorimetric reference color space is similarly output as the soft copy image. The hard copy image patch and the soft copy image patch are compared visually from the observer's observation position, and if the colors of the output hard copy image patch and the soft copy image patch appear to be different, Outputting a patch having a colorimetric value slightly deviated from the coincident colorimetric value for at least one image, and visually comparing the patch with the output hardware The color of the patch of the soft copy image and the color of the patch of the soft copy image are repeated until the color of the patch of the soft copy image looks the same as the color of the patch of the soft copy image. And a color correction method for correcting at least one of the soft copy images. 2. The method of claim 1, wherein the at least one patch is a white one.
The color correction method according to claim 1, wherein the number of patches is one. 3. The color correction method according to claim 1, wherein said at least one patch is two patches of white and black. 4. The at least one patch comprises at least three patches of white, black and at least one intermediate gray.
The color correction method according to claim 1, wherein the number of patches is one. 5. The color correction method according to claim 1, wherein said at least one patch further includes at least one chromatic color patch. 6. The color correction method according to claim 1, wherein said self-luminous recording medium has a movable hood for suppressing softening of said soft copy image due to reflection of external light. 7. The color correction according to claim 1, wherein the color correction is performed by Y expansion and contraction in the XYZ color system, which is the colorimetric reference color space, in order to suppress softening of the soft copy image due to reflection of external light from the self-luminous recording medium. The color correction method according to any one of claims 1 to 6, wherein gradation adjustment is performed by: 8. A self-luminous device for performing color correction for matching colors between a soft copy image output to a self-luminous recording medium and a hard copy image output to a non-self-luminous recording medium. A color correction method, wherein the mold recording medium has a movable hood for suppressing softening of the soft copy image due to reflection of external light.