JPH09107484A - Color correction device and method and device for color management - Google Patents

Abstract

PROBLEM TO BE SOLVED: To convert a picture signal so that an input/output picture observed in various circumstances precisely has the same appearance. SOLUTION: A standard color conversion part 2 converts TGB signals of a scanner 1 to XYZ (D50) signals for the standard observation condition (D50 illumination). A physical correction part 3 converts XYZ (D50) signals to XYZ (X) signals for designated light source 6 and document type 5. A subjective correction part 4 converts XYZ (X) signals to XYZ (D50) signals having the same appearance under the D50 light source in accordance with a color conformity prediction formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color correction device, a color management method and a device for realizing accurate color reproduction under various observation conditions.

[0002]

2. Description of the Related Art In order to construct a device-independent color management system, a method using a standard color signal as an intermediary is known. In such a system, for example, when a scanner RGB signal obtained by reading an image with a scanner is converted into a standard signal (for example, colorimetric values XYZ at a D50 light source) and output from a printer, the standard signal (X
(YZ value) is converted into a printer CMY signal and sent to the printer.

Here, there is no problem if all the systems from the scanner to the printer are under the illumination condition of the D50 light source. For example, when the condition for observing the document to be scanned is the C light source, the color of the document seen by the observer is , The standard signal D
The 50-XYZ values represent different colors and the printer output will have a different color than the original viewed with the C light source. This is also a problem in the environment where the printer output is observed.

In order to cope with such a change in illumination, a color correction method considering the observation conditions has been proposed.
For example, there is a method of correcting the color correction parameter according to the chromatic adaptation prediction formula based on the chromaticity of the illumination light source when observing the input original and the output (see Japanese Patent Laid-Open No. 6-28437). Further, as another method, a method of correcting a color correction parameter by predicting a physical change in reflected light due to a change in illumination light has been proposed.

[0005]

There are two factors in the change of color due to the change of illumination. It is a physical phenomenon, a subjective phenomenon.

Consider, for example, the case of observing color-printed paper in an illumination environment. The nature of the reflected light (spectral brightness) entering the eyes from the printed paper is the nature of the illumination light (spectral brightness).
And the properties of the paper (spectral reflectance). Therefore,
When observing the same paper under different lighting environments, the light entering the eyes has different physical properties.

Further, the "visual appearance of color" as a human sense is determined by the physical properties of light and the subjective visual characteristics of the human being to observe.

Although human visual characteristics have not been completely clarified, a phenomenon called chromatic adaptation in which the characteristics change depending on the lighting environment is known, and a chromatic adaptation prediction formula for predicting the characteristic changes has been proposed. ing.

As described above, when the observation condition such as illumination light changes, the property of the reflected light from the paper physically changes, and further the subjective visual characteristics change in accordance with the observation environment.
Eventually, the "color appearance" changes.

However, in the conventionally proposed method, a chromatic adaptation prediction formula that originally corresponds only to a subjective change is applied to a color change including a physical factor to correct the physical change. However, there is a problem in that sufficient color correction accuracy cannot be realized because, for example, the chromatic adaptation is not taken into consideration.

A first object of the present invention is to provide a color correction device for converting an image signal so that input and output images observed in different environments have exactly the same appearance.

The color management system that mediates the standard color signal has means for converting the device-dependent color signal obtained by the image input device into a standard color signal independent of the image input device.

Here, the standard color signal is a signal representing "a color under the standard observation condition that has the same" color appearance "as the color observed under the condition observed by the user", thereby inputting an image. The color signal is independent of not only the device characteristics of the device but also the observation condition of the input image. Therefore, it is a second object of the present invention to provide a color correction apparatus that realizes color conversion processing for an image input apparatus corresponding to such color signals. A third object of the present invention is to provide a color correction device for converting a standard color signal having the same meaning as described above into a color signal that depends on the image output device and realizing a color conversion process for the image output device. To provide.

There are various types of originals handled by the image input device (for example, printed matter using ink and silver halide photographs). Since these use color materials having different spectral reflectances, the way the reflected light changes when the chromaticity of the illumination light source changes also differs. Therefore, a fourth object of the present invention is to provide a color correction device that accurately corrects the physical characteristics of each document type.

In order to use the prediction formula adapted to the manuscript, a method in which the user specifies the manuscript type can be considered. However, there are cases in which it is difficult for the user to make judgments, such as high-frequency halftone dot printing and photographic paper photographs, and there is a possibility that the user may make a mistake in the designation. For example,
When a halftone dot original is processed as a photographic paper photograph, the error in color correction becomes large. Therefore, a fifth object of the present invention is to provide a color correction apparatus that prevents the accuracy from being impaired by the designation of an incorrect document type even when it is difficult for the user to determine the document type.

In an image display device such as a CRT, black is represented by not emitting light. However, even if it does not emit light, if the illumination light hits the surface of the CRT, it reflects the light,
Has a color other than true black. Then, the black color changes depending on the illumination light, the observation direction, the CRT installation direction, and the like.

A sixth object of the present invention is such a CRT.
An object of the present invention is to provide a color correction device that accurately corrects physical characteristics for color conversion for image display devices such as.

In the color management system which uses the colorimetric value under the standard observation condition as the standard color signal, the input image is observed only by the image signal, unlike the systems described in the above second and third objects. The output side cannot know the appearance of colors under the specified conditions. Therefore, the seventh object of the present invention is to
Even in such a system, it is an object of the present invention to provide a color management method that enables the output side to estimate the color appearance of the input side when the observation conditions of the input and output images are different.

An eighth object of the present invention is, in the color management system described in the seventh object, an image signal which is a colorimetric value under standard observation conditions, an observation condition for observing an input image, and an input image. An output side that receives physical characteristics of a medium estimates a color appearance of an image on an input side, and provides a color management method for accurately converting a color having the same appearance into a signal to be output by an image output device. Especially.

A ninth object of the present invention is to provide a color management method capable of coping with changes in the conditions for observing an output image.

[0021]

In order to achieve the above object, in the invention according to claim 1, the image signal obtained by the image input device is converted so that the original image and the reproduced image have the same color. In a color correction device to be sent to an image output device, a standard color conversion means for converting a signal depending on the image input device into a signal under standard observation conditions, and the converted signal is observed according to a physical characteristic of an input image medium. A first correction means for correcting the color according to the change of the condition; and a second correction means for correcting the corrected signal to a color according to the change of the observation condition according to the color adaptation characteristic. Is characterized by.

According to a second aspect of the present invention, when the image input device and the output device are light emitting image display devices including a CRT, the first correction is performed according to black color under an observation condition. It is characterized by that.

According to a third aspect of the invention, in a color correction device for converting a device-dependent color image signal obtained from an image input device into a device-independent color image signal, the device-dependent color image signal is converted into a device-dependent color image signal. A first means for converting a device-independent color image signal indicating a color under standard viewing conditions, and a device-independent color image signal converted by the first means, according to a physical characteristic of an input image medium. , First
Second, the color image signal indicating the color under the observation condition
And the color image signal converted by the second means into a color image signal showing a color under the standard observation condition, which is equivalent to a color under the first observation condition, according to the chromatic adaptation characteristic. And a third means for doing so.

According to a fourth aspect of the present invention, in a color correction device for converting a color image signal independent of a device into a color image signal dependent on an image output device, the color image signal independent of the device is provided with a color adaptation characteristic. And a fourth means for converting into a color image signal showing a color under the first observation condition, which is equivalent to the color under the standard observation condition, and the color image signal converted by the fourth means, According to the physical characteristics of the medium,
Fifth means for converting into a color image signal showing a color under the standard observation condition, and a sixth means for converting the color image signal converted by the fifth means into a color image signal depending on an image output device. And means are provided.

According to a fifth aspect of the invention, the characteristic of the second means is changed according to the type of the input image medium.

According to a sixth aspect of the present invention, the characteristics of the second means are characteristics corresponding to each type of input image medium and characteristics corresponding to an average of a plurality of types of medium. There is.

According to a seventh aspect of the present invention, in the color management method using the image signal representing the colorimetric value under the standard observation condition as an intermediary, the observation condition and the image medium characteristic on the input side are output at the same time as the standard color signal. It is characterized by transferring to the side.

According to the eighth aspect of the invention, in the color management device for converting the image signal representing the colorimetric value under the standard observation condition into the image signal depending on the image output device, the observation condition and the medium characteristic of the input image A means for storing the observation condition of the output image, and an image signal representing the colorimetric value under the standard observation condition converted into a color image signal indicating the color under the observation condition of the input image according to the medium characteristics of the input image And a color image signal converted by the first conversion unit, showing a color under the observation condition of the output image, which is equivalent to a color under the observation condition of the input image, according to the color adaptation characteristic. It is characterized by comprising: second means for converting into a color image; and third means for converting the color image signal converted by the second converting means into a color image signal depending on an image output device. There is.

According to a ninth aspect of the present invention, in the color management device for converting the image signal representing the colorimetric value under the standard observation condition into the image signal depending on the image output device, the observation condition of the input image and the medium characteristic A means for storing the observation conditions and medium characteristics of the output image, and a color image showing the color of the input image under the observation conditions according to the medium characteristics of the input image, the image signal representing the colorimetric value under the standard observation conditions A first means for converting the signal into a signal and a color image signal converted by the first converting means according to a chromatic adaptation characteristic under an observation condition of an output image equivalent to a color under an observation condition of the input image. Second means for converting into a color image showing a color, and the color image signal converted by the second converting means into a color image signal showing a color under standard observation conditions according to the physical characteristics of the output image medium. A third means of doing A color image signal converted by the third converting means is characterized by comprising a fourth means for converting the color image signal depending on the image output device.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. Two factors must be considered in color conversion corresponding to the viewing conditions. Here, a color conversion method used in a color management system that mediates a standard color signal will be considered.

Consider the spectral brightness of illumination light as an observation condition. Illumination light is a light source (A,
B, C, D50, D55, D65, D75, F1, F
2, F3, F4, F5, F6, F7, F8, F9, F1
0, F11, F12). The standard light source is D50.

When considering a color management system that mediates standard color signals corresponding to different viewing conditions, it is necessary to pay attention to the meaning of standard color signals. There are two possible meanings of the standard color signal. That is, 1. The color of the object observed under observation conditions that are not always standard,
Represents a color that has the same "look" in the standard environment. 2. A colorimetric value obtained by measuring an object under standard observation conditions is shown.

In the system using the standard color signal having the meaning of 1 above, the standard signal represents the "color to be expressed" including the observation condition. Therefore, the standard signal is not only independent of the image input / output device but also independent of the observation condition of the image. In other words, by exchanging only the standard signal, it is possible to express the color that the observer under any condition desires to express.
Instead, color conversion between device-dependent signals and standard signals becomes complicated, including chromatic adaptation prediction.

On the other hand, in the system using the standard color signal having the meaning of 2, the standard signal has no relation to the observation condition, and the information such as the standard observation condition must be exchanged at the same time. However, the conversion from the device-dependent signal to the standard signal does not need to take human subjective visual characteristics into consideration, and thus can be simple. In the following, the method of the present invention will be described in each of these two cases.

(In the case of a standard signal representing a color observed under non-standard observation conditions and a color having the same "look" under the standard conditions) Image input device; on the image input device side, depending on the input device It is necessary to convert the generated color signal into a standard signal. This can be realized by the following procedure. here,
The observation condition of the input image is C light source.

1. Standard color conversion A color signal depending on the input device is converted into a colorimetric value XYZ (D50) under standard observation conditions. Here, a constant conversion is performed regardless of the document observation conditions.

2. Physical Correction Colorimetric values under standard observation conditions are converted into signals XYZ (C) that represent the physical reflected light when the original is observed with the C light source.
This conversion requires information about the physical characteristics of the document (photographic paper / printing, etc.). This is expressed by checking characteristics of a typical document in advance, preparing a conversion formula, and selecting by the user.

3. Subjective correction XYZ (C), which represents the color of the original at the C light source, is converted into a color XY having the same color under the D50 light source according to the color adaptation prediction formula.
Convert to Z (D50).

By such a procedure, it is possible to convert the original into the standard signal XYZ (D50) representing the color under the D light source, which has the same appearance as when the document is observed by the C light source illumination.

Image output device: On the image output device side, it is necessary to convert a standard signal into a color signal depending on the output device. This can be realized by the following procedure, which is the reverse of the input device side. The observation condition of the output image is C light source.

1. Subjective correction The standard signal XYZ (D50) is calculated according to the chromatic adaptation prediction formula.
Convert to a color XYZ (C) having the same color appearance under the C light source.

2. Physical Correction XYZ (C) is converted into a colorimetric value XYZ (D50) under standard observation conditions according to the physical characteristics (spectral reflectance) of the output image medium (print paper, ink, etc.).

3. Standard color conversion XYZ (D50) is converted into a signal depending on the output device such as reproduced by the output device.

With such a procedure, it is possible to obtain an output that shows the same appearance in the C light source environment as "the color represented by the standard signal in the D50 light source environment".

(In the case of a standard signal representing a colorimetric value obtained by measuring an object under standard viewing conditions) In order to represent the color appearance in the viewing environment on the input side, the input image is viewed as additional information in addition to the standard color signal. Send the light source and the type of input image medium (photographic paper / printing, etc.). In order to restore and output the color appearance of the input image on the output side using this information, the image signal may be converted in the following procedure. Here, the observation condition of the input image is C
The light source and the observation condition of the output image are D50 light source.

1. Physical correction 1 A signal XYZ representing a standard signal, which represents the physical reflected light when the input image is observed with a C light source according to the type of the input image medium.
Convert to (C).

2. Subjective correction: According to the color adaptation prediction formula, “a color appearance of XYZ (C) in the C light source” and a color XYZ having the same appearance in the D65 light source
(D65).

3. Physical correction 2 XY with D65 light source according to the physical characteristics of the output image medium
The output medium to be Z (D65) is converted into the color XYZ (D50) when observed with the D50 light source.

4. Standard color conversion XYZ (D50) is converted into a signal depending on the output device such as reproduced by the output device.

With this procedure, it is possible to obtain the same output as that of the D65 light source when the original is observed with the C light source.

(Individual Conversion Method) The color conversion methods described above are all combinations of three conversion methods. Here, each of the three conversion methods will be described in detail.

Standard color conversion: Color conversion between a device-dependent image signal and a device-independent image signal under standard observation conditions,
That is, the scanner RGB signal → CIE-XYZ (D50) CIE-XYZ (D50) → printer CMY signal and the like can be realized by a known method such as table lookup.

Physical correction: In the case of a scanner For example, when the observation condition of the input image is C light source illumination,
It is necessary to convert the color of a document under the D50 light source (CIE-XYZ) to the color of reflected light (XYZ) when the document is illuminated by another light source, for example, the C light source. This conversion formula can be obtained as follows.

1. The spectral reflectance of multiple color patches is measured.

2. Each spectral reflectance is multiplied by the spectral brightness and color matching function of the D50 light source and the C light source, and the XYZ value of each patch when illuminated by that light source is calculated.

3. XYZ (D50) to XY of each patch
The mapping to Z (C) is linearly approximated using the least squares method.

At this time, if a color patch made of silver salt photographic paper is used, physical property correction parameters for silver salt photographic paper are obtained, and if printed matter is used, printed matter parameters are obtained. Further, if the data obtained by mixing the silver halide printing paper and the printed matter is subjected to the first-order approximation, the parameters that are averagely adapted to both are obtained.

In the case of a printer, which is similar to a scanner, the paper and color materials (ink, toner, etc.) handled by the printer may be prepared.

In the case of CRT monitor In a device such as a CRT that displays color by light emission, "black" is represented by not emitting light. However, in the lighting environment, the light hits the display screen and is reflected, so that it does not become true black. Since it always occurs in colors other than black, the actually observed light is (emitted light) + (reflected light when black is displayed).

Therefore, as a standard environment for monitor observation, a standard color conversion parameter is prepared assuming an environment such as a dark room in which illumination does not hit the screen and only emitted light is observed. By subtracting "reflected light when black is displayed" as a correction according to, it is possible to perform accurate color reproduction according to the actual observation environment. The “reflected light when black is displayed” can be obtained by measuring under actual observation conditions using a radiance meter or the like.

Subjective correction: von as a chromatic adaptation prediction formula
The Kries prediction formula is known. This is from the light "XYZ1" observed under "illumination light 1" to "illumination light 2"
It predicts the light "XYZ2" that looks like it underneath.

(Conversion of 3 stages of conversion into 1 stage of conversion) Up to now, it has been explained that conversion of multiple stages is connected in series to perform conversion. However, by using a lookup table, these conversions can be performed. The steps can be converted at once. Performing multi-stage conversion with a single-stage table
The hardware implementation has the effect of reducing the circuit scale, and the software implementation has the effect of improving the processing speed.

Here, a case where the scanner RGB signals are converted into standard signals will be described as an example. In this case, a process equivalent to the continuous three-stage conversion of standard color conversion → physical correction → subjective correction is realized by using a one-stage lookup table.

A three-dimensional table is used here. That is, if the scanner RGB signal has a value in the range of 0 to 255 for R, G, and B, the value is 255 ³ = 1.
There are 6581357 types, but if a table in which all output values corresponding to these input values are recorded is prepared, any conversion can be realized by referring to the table once. Also, in order to save the capacity of the table, without recording the output value for all input values,
For example, only 0, 64, 128, 255 are recorded,
For input values for which output values are not recorded, the output value can be calculated by interpolation calculation.

A method of creating table data will be described below in order to execute multi-step conversion with one table reference. FIG. 8 is a diagram illustrating table setting. Here, in order to simplify the explanation, it is assumed that the signal is a one-dimensional signal. In the figure, the upper right part of the graph (that is, the first quadrant) represents the standard color conversion, and the upper left part (the second quadrant, from the vertical axis to the horizontal axis).
Represents physical correction, lower left (third quadrant, horizontal axis to vertical axis)
Represents subjective correction, and the lower right (fourth quadrant) represents the table set here.

In the table, output values corresponding to the respective input values may be recorded. Therefore, output values are calculated and recorded as follows for all terms (input values) existing in the table. 1. The standard color conversion result corresponding to the input value is obtained. 2. Then, the result of physically correcting the result is calculated based on the formula. 3. Further, the result of subjectivity correction of the result of physical correction is calculated based on the formula. 4. Then, this subjective correction result is recorded in the table as an output value corresponding to the input value used first.

If the look-up table is set as described above, the table performs the same conversion as in the case of performing the three-stage processing of standard color conversion, physical conversion, and subjective conversion. Similarly, the input side conversion and the output side conversion are combined into 1
It can also be one table.

<Embodiment> The following Embodiments 1 to 5 relate to a system using "a standard color representing an object color observed under observation conditions that are not always standard and a color having the same appearance under standard conditions". A color conversion device for a scanner, a printer, and a CRT monitor. The CRT monitor serves as an image input device when the color is adjusted and edited on the screen and sent to another device, and an image output device when an image signal sent from another device is displayed. explain. In addition, Examples 6 and 7 are color conversion devices for a printer and a monitor in a system that uses a "standard signal representing a colorimetric value in a standard environment".

Example 1 Example 1 is an example of scanner color conversion. FIG. 1 shows the configuration of the first embodiment. The scanner 1 that inputs an image reads a document and generates RGB signals. The standard color conversion unit 2 that performs color conversion under standard viewing conditions converts the RGB signals into XYZ signals obtained by measuring the document under standard viewing conditions. This conversion is based on the preset 3
It is realized by a dimension lookup table.

The physical correction unit 3 for correcting the physical characteristics is
The XYZ signals measured under the standard observation conditions are converted into the XYZ signals measured for the specified type of original document under the specified observation conditions. Here, it is realized by a preset approximate linear equation.

The subjective correction unit 4 for predicting chromatic adaptation converts an XYZ signal under the specified viewing condition into an XYZ signal under which the human feels the same color under the standard viewing condition. The correction here is calculated according to the von Kries chromatic adaptation prediction formula.

The document type designating unit 5 designates the type of document to be scanned, and the light source designating unit 6 designates a light source for actually observing the document.

The light sources for observing the original are (A, B, C, D5
0, D55, D65, D75, F1, F2, F3, F
4, F5, F6, F7, F8, F9, F10, F11,
The user selects one from F12). The user selects one of the manuscript types from among photographic paper, printing, and both. Alternatively, the observation light source and the type of the original may be stored together with the scanner RGB signals when the scanner is operated, and may be taken out when the color conversion is executed.

<Embodiment 2> Embodiment 2 is an embodiment of scanner color conversion (one-stage conversion). FIG. 2 shows the configuration of the second embodiment. An image is input by the scanner 21, and the converter 22 converts the RGB signal of the scanner 21 into the standard signal XYZ.
(D50). Here, the signal is converted using a one-dimensional three-dimensional lookup table.

The parameter storage unit 23 stores the scanner RGB → XYZ (D50) in the standard observation environment (D50 illumination).
Parameters for conversion are stored. That is, the parameter storage unit 23 stores the same table data as that used in the standard color conversion unit 2 described in the first embodiment. The physical correction conversion type storage unit 24 stores the XYZ (D5
0) designated light source and original type color signal XYZ
The conversion formula to (X) is stored, and the coefficient of the same physical correction linear equation as that of the physical correction unit 3 of the first embodiment is stored.

The prediction formula parameter storage unit 25 stores the parameters of the prediction formula for predicting the chromatic adaptation from the designated light source environment to the D50 environment, and the same von Kries chromatic adaptation as the subjective correction unit 4 of the first embodiment. The parameters of the prediction formula are stored.

The parameter calculation unit 26 uses the standard color parameters in the parameter storage unit 23, the conversion formula parameters in the storage unit 24, and the prediction formula parameters in the storage unit 25 for the designated light source and document type. The color conversion parameter (3D color conversion table data) of is calculated. The light source designating unit 27 designates the observation light source of the document, and the document type designating unit 28
Specifies the type of document.

In the second embodiment, one converter 22 performs the same conversion as the three-stage conversion in the standard color conversion unit 2, the physical correction unit 3, and the subjective correction unit 4 described in the first embodiment.

Similar to the first embodiment, the light source for observing the original is
(A, B, C, D50, D55, D65, D75, F
1, F2, F3, F4, F5, F6, F7, F8, F
The user selects one from among 9, F10, F11, and F12). The types of manuscripts are (photographic paper, printing, both)
The user selects one from among. Alternatively, the observation light source and the type of the original may be stored together with the scanner RGB signals when the scanner is operated, and may be taken out when the color conversion is executed.

Similarly, the following embodiments include a method using a multi-stage converter and a method using a single-stage converter, but only the method using a single-stage converter will be described.

<Embodiment 3> Embodiment 3 is an embodiment of printer color conversion (one-step conversion), and FIG. 3 shows the configuration of Embodiment 3. The converter 31 converts the standard signal XYZ (D50) into the CMY signal of the printer 32. The prediction formula parameter storage unit 33 stores the parameters of the prediction formula for predicting the chromatic adaptation from the D50 environment to the designated light source environment. The physical correction conversion formula storage unit 34 stores a conversion formula from the color signal XYZ (X) at the designated light source to XYZ (D50). The parameter storage unit 35 stores XYZ (D50) in the standard observation environment (D50 illumination) → printer CMY.
The signal conversion parameters are stored. Parameter calculator 3
Reference numeral 6 calculates the color conversion parameter of the designated light source using the prediction formula in the storage unit 33, the conversion formula in the storage unit 34, and the standard color conversion parameter in the storage unit 35. The light source designating section 37 designates the observation light source of the user.

<Embodiment 4> Embodiment 4 is an embodiment of color conversion (one-step conversion) for a monitor (image input device).
Shows the configuration of the fourth embodiment. The monitor signal storage unit 41 stores monitor RGB signals. The converter 42 is a monitor R
The GB signal is converted into the standard signal XYZ (D50). The parameter storage unit 43 stores parameters for monitor RGB → XYZ (D50) conversion in the standard observation environment (D50 illumination). The physical correction conversion type storage unit 44 stores the XYZ (D5
0) Light source specified from 0), color signal X in black on monitor display
The conversion formula to YZ (X) is stored. The prediction formula parameter storage unit 45 stores the parameters of the prediction formula for predicting the chromatic adaptation from the designated light source environment to the D50 environment. The parameter calculation unit 46 uses the standard color conversion parameters in the storage unit 43, the conversion formula in the storage unit 44, and the prediction formula in the storage unit 45 to calculate the color conversion parameters for the specified light source and monitor display black. calculate. The light source designating unit 47 designates the observation light source of the user, and the black designating unit 48 designates the monitor display black. The black display on the monitor is measured and input by the user in advance by the measuring device.

<Embodiment 5> Embodiment 5 is an embodiment of color conversion (single-stage conversion) for a monitor (image output device).
Shows the configuration of the fifth embodiment. The converter 51 uses the standard signal X
YZ (D50) is converted into a monitor RGB signal. 52 is a CRT monitor. The parameter storage unit 53 stores XYZ (D50) → monitor R in a standard observation environment (D50 illumination).
The parameters for GB signal conversion are stored. The physical correction conversion type storage unit 54 stores the designated monitor display black and color signal X.
The conversion formula from YZ (X) to XYZ (D50) is stored. The predictive parameter storage unit 55 stores, from the D50 environment,
The parameter of the prediction formula for predicting the chromatic adaptation to the specified light source environment is stored. The parameter calculation unit 56 includes a storage unit 5
The standard color conversion parameter in 3, the conversion formula in the storage unit 54, and the prediction formula in the storage unit 55 are used to calculate the color conversion parameter of the designated light source. The light source designating unit 57 designates the observation light source of the user, and the black designating unit 58 designates the monitor display black.

<Embodiment 6> Embodiment 6 is an embodiment of printer color conversion (one-step conversion), and FIG. 6 shows the configuration of Embodiment 6. The converter 61 converts the standard signal XYZ (D50) into the CMY signal of the printer 62. The first physical correction conversion type storage unit 63 receives the input image observing light source received from XYZ (D50) and the color signal X of the input image original document type.
The conversion formula to YZ (X) is stored. The prediction formula parameter storage unit 64 stores parameters of a prediction formula for predicting chromatic adaptation from the input image observation light source environment to the output image observation light source environment. The second physical correction conversion type storage unit 65 stores the designated output image observation light source and the color signal XY of the output image original document type.
The conversion formula from Z (X) to XYZ (D50) is stored.
The parameter storage unit 66 stores the standard observation environment (D50 illumination).
XYZ (D50) → printer CMY signal conversion parameters are stored. The parameter calculation unit 67 includes a storage unit 6
3, the conversion formula in 3, the prediction formula in the storage unit 64, and the storage unit 65.
The color conversion parameters for the specified environment are calculated using the conversion formula in the above and the standard color conversion parameters in the storage unit 66. The light source designating unit 68 designates an output image observation light source.

<Embodiment 7> Embodiment 7 is an embodiment of monitor color conversion (one-stage conversion), and FIG. 7 shows the configuration of Embodiment 7. The converter 71 converts the standard signal XYZ (D50) into the RGB signal of the monitor 72. The first physical correction conversion type storage unit 73 stores the color signal XYZ of the designated input image observation light source and the input image original type from XYZ (D50).
The conversion formula for (X) is stored. The prediction formula parameter storage unit 74 stores parameters of a prediction formula for predicting chromatic adaptation from the input image observation light source environment to the output image observation light source environment. The second physical correction conversion type storage unit 75 stores the designated output image observation light source and the monitor display black color signal XYZ.
The conversion formula from (X) to XYZ (D50) is stored. The parameter storage unit 76 stores parameters for XYZ (D50) → monitor RGB signal conversion in a standard observation environment (D50 illumination). The parameter calculation unit 77 uses the conversion formula in the storage unit 73, the prediction formula in the storage unit 74, the conversion formula in the storage unit 75, and the standard color conversion parameter in the storage unit 76 for the specified environment. Calculate the color conversion parameters of.
The black color designation unit 78 designates the output image observation light source and the monitor display black color.

[0086]

As described above, according to the first aspect of the present invention, color conversion can be performed so that the same color can be obtained accurately even under different observation conditions.

According to the second aspect of the invention, it is possible to accurately predict and correct the physical color property under the actual observation condition.

According to the invention described in claim 3, in the color management system using the standard signal representing the color of the object observed under the specific observation condition and the color having the same "look" under the standard observation condition, the image input device It is possible to accurately convert the color signal depending on the standard signal into the standard signal.

According to the fourth aspect of the invention, in the color management system using the standard signal representing the color of the object observed under the specific observation condition and the color having the same "look" under the standard observation condition, the standard signal is , Can be accurately converted into a color signal depending on the image output device.

According to the fifth aspect of the invention, it is possible to perform accurate color conversion on various types of originals.

According to the invention described in claim 6, color conversion can be performed without a large error even when the type of the original cannot be determined.

According to the seventh aspect of the invention, in the color management system that mediates the image signal representing the colorimetric value under the standard observation condition, the colors of the input and the output can be accurately matched.

According to the eighth aspect of the invention, in the color management system which mediates the image signal representing the colorimetric value under the standard observation condition, the standard color signal is accurately converted into the color signal depending on the image output device. Can be converted.

According to the ninth aspect of the invention, in the color management system which mediates the image signal representing the colorimetric value under the standard observation condition, the standard color signal is changed even if the condition for observing the output image changes. , Can be accurately converted into a color signal depending on the image output device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a first embodiment.

FIG. 2 is a diagram showing a configuration of a second embodiment.

FIG. 3 is a diagram showing a configuration of a third embodiment.

FIG. 4 is a diagram showing a configuration of a fourth exemplary embodiment.

FIG. 5 is a diagram showing a configuration of a fifth exemplary embodiment.

FIG. 6 is a diagram showing a configuration of a sixth embodiment.

FIG. 7 is a diagram showing a configuration of a seventh embodiment.

FIG. 8 is a diagram illustrating a method of creating a table for performing three-step conversion by one-step conversion.

[Explanation of symbols]

 1 Scanner 2 Standard Color Conversion Section 3 Physical Correction Section 4 Subjective Correction Section 5 Original Type Designation Section 6 Light Source Designation Section

Claims (9)

[Claims] 1. A color correction device that converts an image signal obtained by an image input device and sends the image signal to an image output device so that an original image and a reproduced image have the same color, and a signal depending on the image input device is standardized. Standard color conversion means for converting into a signal under the viewing condition, a first correction means for correcting the converted signal into a color according to a change in the viewing condition according to the physical characteristics of the input image medium, and the corrected color correction means. And a second correction unit that corrects the obtained signal into a color according to the change of the observation condition according to the color adaptation characteristic. 2. When the image input device and the output device are light-emitting image display devices including a CRT, the first correction is performed according to a black color under an observation condition. Item 1. The color correction device according to item 1. 3. A color correction device for converting a device-dependent color image signal obtained from an image input device into a device-independent color image signal, wherein the device-dependent color image signal is converted under standard observation conditions. First means for converting a device-independent color image signal into a device-independent color image signal, and the device-independent color image signal converted by the first device according to a physical characteristic of an input image medium, and a first observation condition. The second means for converting into a color image signal indicating the color in the above, and the color image signal converted by the second means according to the chromatic adaptation characteristic, which is equivalent to the color under the first observation condition, And a third means for converting into a color image signal showing a color under standard observation conditions. 4. A color correction device for converting a device-independent color image signal into a color image signal dependent on an image output device, wherein the device-independent color image signal is subjected to standard adaptation conditions according to color adaptation characteristics. According to the physical characteristics of the output image medium, the fourth means for converting into a color image signal showing a color under the first observation condition, which is equivalent to the above color, and the color image signal converted by the fourth means, Fifth means for converting into a color image signal showing a color under the standard observation condition, and a sixth means for converting the color image signal converted by the fifth means into a color image signal depending on an image output device. A color correction device comprising: 5. The characteristic of the second means is changed according to the type of the input image medium.
The described color correction device. 6. The characteristic of the second means is a characteristic corresponding to a type of each input image medium and a characteristic corresponding to an average of a plurality of types of medium. Color correction device. 7. A color management method using an image signal representing a colorimetric value under standard viewing conditions as an intermediary, wherein the viewing conditions and image medium characteristics at the input side are transferred to the output side at the same time as the standard color signal. Characteristic color management method. 8. A color management device for converting an image signal representing a colorimetric value under a standard viewing condition into an image signal dependent on the image output device, wherein the viewing condition of the input image and the medium characteristic, and the viewing condition of the output image. A means for storing, and an image signal representing a colorimetric value under standard observation conditions, according to the medium characteristics of the input image,
First means for converting into a color image signal indicating a color under the observation condition of the input image, and the color image signal converted by the first conversion means are observed under the observation condition of the input image according to the color adaptation characteristic. Second means for converting into a color image showing a color under the viewing condition of the output image, which is equivalent to the color of the above, and the color image signal converted by the second converting means, the color image depending on the image output device. A color management device comprising: a third means for converting into a signal. 9. A color management device for converting an image signal representing a colorimetric value under standard viewing conditions into an image signal dependent on the image output device, wherein the viewing condition and the medium characteristic of the input image and the viewing condition of the output image. A means for storing medium characteristics, and an image signal representing a colorimetric value under standard observation conditions, converted into a color image signal showing a color under the observation conditions of the input image according to the medium characteristics of the input image. And the color image signal converted by the first conversion means according to the chromatic adaptation characteristic,
Second means for converting into a color image showing a color under the observation condition of the output image, which is equivalent to a color under the observation condition of the input image;
A third means for converting the color image signal converted by the second converting means into a color image signal showing a color under a standard observation condition according to the physical characteristics of the output image medium, and the third converting means. And a fourth means for converting the converted color image signal into a color image signal depending on an image output device.