JP3311295B2 - Image processing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to image processing for obtaining color matching conversion data according to viewing conditions.

[0002]

2. Description of the Related Art FIG. 1 is a conceptual diagram of general color matching.

[0003] Input data that is RGB data is converted into XYZ data in a device-independent color space by an input profile. Since colors outside the color gamut of the output device cannot be represented by the output device, all colors fall within the color gamut of the output device.
Color space compression is performed on input data converted into data in a device-independent color space. After the color space compression is performed, the input data is converted from a device-independent color space to CMYK data in an output device-dependent color space.

In color matching, a reference white point and ambient light are fixed. For example, International Co
In the profile specified by the lor Consortium (ICC), the Profile Connection S
pace (PCS) is the XYZ value and Lab value based on D50. For this reason, when an input document or print output is observed under a light source with D50 characteristics, correct color reproduction is guaranteed, and under a light source with other characteristics, correct color reproduction is not guaranteed.

[0005]

When observing the same sample (for example, an image) under different light sources, the XYZ values for the observed sample naturally differ. To predict XYZ values under different light sources, (1) ratio conversion, (2) Von Kries
There are conversion methods such as conversion and (3) a prediction expression using a color perception model.

The ratio conversion is a method of performing a ratio conversion of W2 / W1 in order to convert an XYZ value below the reference white point W1 into an XYZ value below the reference white point W2. When this method is applied to the Lab uniform color space, the Lab value under W1 matches the Lab value under W2. For example, sample XYZ under W1 (Xw1, Yw1, Zw1)
XYZ of the sample under values (X1, Y1, Z1) and W2 (Xw2, Yw2, Zw2)
When the value is (X2, Y2, Z2), the following relationship is obtained according to the ratio conversion. X2 = (Xw2 / Xw1) · X1 Y2 = (Yw2 / Yw1) · Y1 ... (1) Z2 = (Zw2 / Zw1) · Z1

[0007] The Von Kries transform converts the XYZ value under W1 under W2.
In order to convert to XYZ values, W2 '/
This is a method of performing ratio conversion of W1 '. When this method is applied to the uniform color space of Lab, the Lab value under W1 and L under W2
Ab values do not match. For example, the XYZ value of the sample under W1 (Xw1, Yw1, Zw1) is (X1, Y1, Z1), and the XYZ value of the sample under W2 (Xw2, Yw2, Zw2) is (X2, Y2, Z2). Then, according to the Von Kries transform, the following relationship is obtained.

The prediction formula based on the color perception model is based on the viewing condition VC
XYZ values under 1 (including W1) are observed under the viewing condition VC2 (including W2)
In order to convert to the following XYZ values, a conversion method is used using a human color perception space QMH (or JCH) such as CIE CAM97s. Where Q in QMH is brightness and M is colou
rfulness, H stands for huequadrature or hueangle, JC
H is lightness, C is chroma, H is huequadrature or
Represents a hueangle. When this conversion method is applied to Lab's uniform color space, the Lab value under W1 and W2
The Lab values below do not match. For example, the XYZ value of the sample under W1 (Xw1, Yw1, Zw1) is (X1, Y1, Z1), and the XYZ value of the sample under W2 (Xw2, Yw2, Zw2) is (X2, Y2, Z2). Von Kri
According to the es conversion, the following conversion is performed. (X1, Y1, Z1) → [CIE CAM97s forward conversion] → (Q, M, H) or (J, C,
H) → [CIE CAM97s reverse conversion] → (X2, Y2, Z2)

That is, if it is assumed that the XYZ values under different reference white points can be converted by the ratio conversion, the isohue lines in the Lab color space under different reference white points are always constant, but the Von Kreis conversion and the color When human color perception is taken into consideration as in a prediction formula using a perceptual model, the isohue line in the Lab color space under different reference white points changes depending on the reference white point.

[0010] For the above reasons, when the color space compression (hue preservation) defined in the same Lab color space is applied to the color matching under different reference white points, the hue is not uniform to human eyes. May be

In the current ICC profile, PCS is
Since it is limited to XYZ values and Lab values based on D50, color matching corresponding to ambient light cannot be performed.

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to realize highly accurate color matching regardless of viewing conditions.

[0013]

The present invention has the following arrangement as one means for achieving the above object.

According to the image processing method of the present invention, an observation condition is acquired, and colorimetric data dependent on a light source close to the acquired observation condition is converted into a plurality of measurement data dependent on a plurality of light sources held in a profile. Select from color data, perform a conversion process using a color perception model on the selected colorimetric data, estimate colorimetric data corresponding to the observation condition, and from the estimated colorimetric data to the observation condition A step of obtaining corresponding color matching conversion data, wherein the colorimetric data corresponds to device-dependent color space data.
Tagged, characterized in that the data is a device-independent color space.

An image processing apparatus according to the present invention relies on acquisition means for acquiring an observation condition and colorimetric data dependent on a light source close to the acquired observation condition on a plurality of light sources held in a profile. Selecting means for selecting from a plurality of colorimetric data, and estimating means for performing a conversion process on the selected colorimetric data using a color perception model and estimating colorimetric data corresponding to the observation condition; Creating means for creating color matching conversion data corresponding to the viewing condition from the colorimetric data, wherein the colorimetric data comprises:
Associated with device-dependent color space data ,
It is characterized in that it is data in a device-independent color space.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

First, a color perception model used in the embodiment described below will be described with reference to FIG.

The color perceived by the human visual system is
It is known that even if the same light enters the eyes, they look different depending on conditions such as the difference in illumination light and the background on which the stimulus is applied.

For example, white illuminated by an incandescent light bulb is not perceived as red as the characteristics of light entering the eyes, but is perceived as white. Also, white on a black background feels brighter between white on a black background and white on a light background. The former phenomenon is known as chromatic adaptation, and the latter as contrast. For this purpose, it is necessary to display colors in an amount corresponding to the physiological activity of photoreceptors distributed in the retina instead of XYZ, but a color perception model has been developed for such purpose . CIE recommends using CIE CAM97s. This color perception model uses physiological three primary colors of color perception. For example, H (hue), J (brightness) and C (chroma), which are correlation amounts of color perception calculated by CIE CAM97s, or H (hue) ), Q (brightness) and
The value of M (colorfulness) is considered to be a color display method that does not depend on viewing conditions. By performing color reproduction so that the values of H, J, C or H, Q, M match between devices, it is possible to resolve differences in viewing conditions of input and output images.

The processing contents in the forward conversion of the color perception model CIE CAM97s for performing the correction processing (processing for converting XYZ into HJC or HQM) according to the observation conditions when observing the input image are as follows:
This will be described with reference to FIG.

First, in step S160, as the observation condition information of the input image, the luminance of the adaptive visual field (cd / m 2,
20% of the white brightness in the adaptive field of view is selected) L
A, XYZ which is the relative tristimulus value of the sample under the light source condition, XωYωZ which is the relative tristimulus value of the white light under the light source condition
ω and Yb which is the relative luminance of the background under the light source condition
Is set. In addition, based on the type of viewing condition specified in step S180, as viewing condition information of the input image,
In step S170, a constant c of surrounding influence, a color induction coefficient Nc, a lightness contrast coefficient FLL, and a coefficient F of adaptation are set.

Based on the input image observation condition information set in steps S160 and S170, the following processing is performed on XYZ indicating the input image.

First, based on Bradford's three primary colors, which are considered as the physiological three primary colors of humans, XYZ is converted and Bra
A dford cone response RGB is obtained (S100). Since human vision does not always perfectly adapt to the viewing illuminant, a variable D that indicates the degree of adaptation based on the luminance level and the ambient conditions (LA and F)
Is calculated based on the variable D and XωYωZω, and the RGB is converted to RcGcBc (S110).

Next, based on the three primary colors of Hunt-Pointer-Estevez, which are considered as three primary colors of human physiology, RcGc
By converting Bc, a Hunt-Pointer-Estevez cone response R'G'B 'is obtained (S120). The adaptation degree based on the stimulus intensity level is estimated for this R'G'B ', and a post-adaptive cone response R'aG'aB'a corresponding to both the sample and white is obtained (S130). In step S130, nonlinear response compression is performed using the variable FL obtained based on the luminance LA of the adaptive visual field.

Subsequently, the following processing is performed to determine the correlation with the appearance.

The red-green and yellow-blue opponent responses ab are R'a
The hue H is calculated from G'aB'a (S140), and the hue H is calculated from the opponent color response ab and the eccentricity coefficient (S150).

Further, a background induction coefficient n obtained from Yω and the relative luminance Yb of the background is obtained.
The achromatic responses A and Aω for both the sample and white are determined using (S190), the coefficient z determined from the background induction coefficient n and the brightness contrast coefficient FLL, and A, Aω
And the lightness J is determined based on c and c (S151), and the color induction coefficient Nc
, A saturation C is determined from the saturation S and the brightness J (S152), and a luminance Q is determined from the brightness J and the white achromatic response Aω (S154).

The colorfulness M is obtained from the variable FL and the constant c of the influence of the surroundings (S155).

[0029]

[First Embodiment] A first embodiment in which a profile is dynamically changed according to observation conditions will be described.

In FIG. 2 for explaining the concept of the present invention, 11
Is a conversion matrix or conversion look-up table (LUT) for converting input device-dependent data to device-independent color space data based on the input-side ambient light white point reference, and 12 is obtained from the conversion LUT 11. A forward conversion unit (CAM) of a color appearance model for converting data into a human color appearance color space JCh or QMh, 13 is a color appearance space JCh (or JCH) which is a color appearance space relative to a reference white of ambient light, 14 QMh (or QMH) is an absolute color perception space whose size changes according to the illuminance level, and 15 is the human color perception space JCh or Q
The inverse conversion unit of the color perception model for converting from Mh to device-independent color space data based on the white point reference of the ambient light on the output side, and the color conversion unit 16 converts the data obtained from the inverse conversion unit 15 into colors dependent on the output device Conversion to convert to spatial data
LUT.

In general, the white point of the ambient light under the viewing conditions is different from the white point of the standard light source when measuring a color chart such as a color target or a color patch. For example, the standard light source used for color measurement is D50 or D65, but the ambient light for actually observing the image is not limited to D50 or D65 in the light booth, and lighting such as incandescent lamps and fluorescent lamps Light,
In many cases, the light is a mixture of illumination light and sunlight. In the following description, for the sake of simplicity, the light source characteristics of environmental light under observation conditions are D50, D65, and D93, but the XYZ values of the white point on the medium are actually set as the white point.

FIG. 3 is a block diagram showing a functional configuration example of the present embodiment. In FIG. 3, 41 is an input profile 42
A data creation unit for creating data dependent on the input-side viewing condition 1 from the input-side viewing condition 1;
A color space compression mode selection unit 44 and 45 for selecting whether to perform on the JCH color space or on the QMH color space, and a color to be subjected to color space compression on the data on the JCH or QMH color perception space based on the output profile 46, respectively. A spatial compression unit 47 is a data creation unit that creates data depending on the output-side observation condition 2 from the output profile 46 and the output-side observation condition 2, and 48 is an observation condition 1.
Is a color matching unit that performs color matching using data dependent on color space, color space compressed data, data dependent on viewing condition 2, and a color perception model.

FIG. 18 is a block diagram showing a configuration example of an apparatus for realizing the functional configuration shown in FIG. 3. The apparatus shown in FIG. 18 is, for example, a general-purpose computer apparatus such as a personal computer. Needless to say, this can be achieved by supplying software that realizes the functions shown in FIG. In that case, the software for realizing the functions of the present embodiment may be included in the OS (basic system) of the computer device, or may be included in the driver software of the input / output device separately from the OS, for example. .

In FIG. 1, a CPU 100 controls the operation of the entire apparatus by using a RAM 102 as a work memory in accordance with a program stored in a ROM 101, a hard disk (HD) 106, and the like. Various processes including related processes are executed. The input interface 103 is for connecting an input device 104,
The hard disk interface 105 is an interface for connecting an HD 106, the video interface 107 is an interface for connecting a monitor 108, and the output interface 109 is an interface for connecting an output device 110.

The input devices to which the present embodiment is applied include photographing devices such as digital still cameras and digital video cameras, and various image input devices such as image readers such as image scanners and film scanners. It is. Output devices include color monitors such as CRTs and LCDs, and image output devices such as color printers and film recorders.

A general-purpose interface can be used as the interface. Depending on the application, for example, RS
Serial interfaces such as 232C, RS422 and IEEE1394, and parallel interfaces such as SCSI, GPIB and Centronics are available.

Although an input / output profile for performing color matching is stored in the HD 106, the input / output profile is not limited to a hard disk, and an optical disk such as an MO can be used.

An example in which color matching is performed using an input / output profile will be described below.

[Creation of Data Dependent on Observation Condition 1] The conversion LUT 11 is created using the data creation unit 41,
To create T11, the XYZ values (or Lab values) of the color target and the RG of the input device are shown in FIG.
From the relationship of the B value, a method of reconstructing the conversion LUT 11 corresponding to the ambient light, and an input profile 4 shown as an example in FIG.
There is a method of updating the conversion LUT for converting the device RGB space into the XYZ space in 2 into the conversion LUT 11 corresponding to the ambient light.

FIG. 4 is a flowchart showing an example of processing for reconstructing the conversion LUT 11 corresponding to the ambient light.

In step S51, a profile designated by the user is read from the input profile 42 in order to reconstruct the conversion LUT 11 corresponding to the ambient light. The XYZ values of the color target (or Lab
XYZ → RGB data which associates the color target with a device RGB value when the color target is read by a certain input device. The XYZ → RGB related data is extracted from the profile in step S52. Since the viewing condition 1 is also stored in the profile, step S53
Then, the observation condition 1 is taken out from the profile.

Since the XYZ values of the XYZ → RGB relation data extracted in step S52 are data based on D50 or D65 which is the reference light when the color target is measured, the XYZ values based on the colorimetric light source are used. Needs to be corrected to the ambient light standard XYZ value. In step S54, the XYZ value of the colorimetric light source reference is determined by the color perception model, and the white point of the D50 light source (in the case of the D50 reference), which is the colorimetric condition, the illuminance level, the state of the ambient light, etc. Color perception space JCH
Is converted to a viewing condition 1 different from the colorimetric condition, for example, D
An XYZ value based on the ambient light is obtained by performing an inverse conversion to an XYZ value again using a color appearance model based on the white point of the 65 light sources, the illuminance level, the state of the ambient light, and the like. As a result, a relationship between the XYZ values of the ambient light reference and the device RGB values was obtained, and in step S55, RGB → XY based on the RGB → XYZ relationship data.
If a Z-transform matrix is created and optimized by an iterative method or the like, a transform LUT 11 corresponding to the environmental condition 1 can be obtained.

FIG. 5 is a flowchart showing an example of processing for updating the conversion LUT 11 corresponding to the ambient light. Steps in which the same processing as in FIG. 4 is executed are denoted by the same reference numerals, and detailed description thereof will be omitted.

Generally, a conversion matrix (col) for performing RGB → XYZ conversion is included in an ICC profile for an input device.
orant Tag) or the conversion LUT (AtoB0 Tag) is stored, so that RGB → XYZ relation data is extracted from the profile in step S62.

After the relationship between the XYZ values of the ambient light reference and the device RGB values is obtained in step S54, the conversion matrix (colorant Tag) or conversion LUT (AtoB0 Tag) in the profile is updated in step S66. Thus, the conversion LUT 11 corresponding to the environmental condition 1 can be obtained.

In general, a conversion matrix (colorant tag) or a conversion LUT (AtoB0 Tag) for performing RGB → XYZ conversion is stored in an ICC profile for an input device. 4 and FIG. 5, an example in which RGB → XYZ relation data is used has been described.
Other device-independent color data such as ab-related data may be used.

[Selection of Color Space Compression Mode and Color Space Compression] The color space compression mode is selected by the user via the user interface or automatically selected by Rendering Intent in the header of the source profile. The case of automatic selection based on the profile is as follows. Perceptual Color space compression mode on JCH color space Relative Colorimetric Color space compression mode on JCH color space Saturation Color space compression mode on JCH color space Absolute Colorimetric Color space compression mode on QMH color space

That is, in the case of relative color matching, the JCH space 13 is selected, and in the case of absolute color matching, the QMH space 14 is selected.

FIG. 6 is a flowchart showing an example of processing for performing color space compression on JCH 13 or QMH 14.

In order to perform color space compression on the color perception space,
In step S81, a profile designated by the user is read from the output profile.

In general, an output device ICC profile includes a judgment LUT for inputting an XYZ value or a Lab value in order to judge whether the color reproduction area is inside or outside (hereinafter, referred to as “color reproduction area inside / outside judgment”). (gamut Tag) is stored. However, since the XYZ values are based on D50 or D65, which is a characteristic of the colorimetric light source, they cannot be directly used for determining whether the color reproduction area is inside or outside according to the ambient light. Therefore, instead of using the LUT (gamut Tag) for determining the inside / outside of the color reproduction area, the CMYK → XYZ related data is converted from the conversion LUT (AtoB0 Tag etc.) for performing the CMYK → XYZ conversion stored in the profile. It is taken out and used in step S82. Since the viewing condition 2 is also stored in the output profile, the viewing condition 2 is extracted from the output profile in step S83.

Since the XYZ values of the CMYK → XYZ relation data extracted in step S82 are data based on D50 or D65 which is the colorimetric light, it is necessary to correct the XYZ values based on the ambient light. In step S84, the XYZ value of the colorimetric light reference by the color perception model, using the color perception model based on the white point of the D50 light source that is the colorimetric condition `` in the case of the D50 reference '', the illuminance level and the state of the ambient light, Human color perception space JC
Converted to H, it is an observation condition 2 different from the colorimetric condition For example
XYZ values are again converted back to XYZ values based on the white point of the D65 light source, the illuminance level, the state of ambient light, and the like, to obtain the XYZ values based on the ambient light. As described above, in step S84, the relationship between the CMYK values of the device and the XYZ values based on the ambient light is determined. In step S85, a color reproduction area of the output device in the JCH or QMH color space is obtained based on the CMYK → ambient light XYZ relation data obtained in step S84.

The color reproduction area of the output device in the JCH or QMH color space is, for example, Red (C: 0%, M: 100%, Y: 100%, K: 0%) Yellow (C: 0%, M : 0%, Y: 100%, K: 0%) Green (C: 100%, M: 0%, Y: 100%, K: 0%) Cyan (C: 100%, M: 0%, Y: 0%, K: 0%) Blue (C: 100%, M: 100%, Y: 0%, K: 0%) Magenta (C: 0%, M: 100%, Y: 0%, K: 0 %) White (C: 0%, M: 0%, Y: 0%, K: 0%) Black (C: 0%, M: 0%, Y: 0%, K: 100%)

The XYZ values of the ambient light reference for the eight points are obtained by using the CMYK → ambient light XYZ relation data obtained in step S84, and furthermore, the color perception model JCH based on the observation condition 2 by the color perception model. Alternatively, it can be approximated by a dodecahedron as shown in FIG. 7 by converting it into QMH coordinate values.

In a color reproduction area approximated by a dodecahedron,
Whit on a point inside the color reproduction area, for example, on the achromatic axis
If the midpoint between e and Black and the point (JCH value or QMH value) of the input color signal to be judged inside / outside are on the same side, it is judged to be within the color gamut. Judge that it is outside.

Color space compression is performed in step S86 based on the result of the inside / outside determination based on the color reproduction area obtained in step S85. FIG. 8 is a diagram illustrating the concept of color space compression in the JCH color perception space, and FIG. 9 is a diagram illustrating the concept of color space compression in the QMH color perception space. The input color signal determined to be out of the color reproduction range of the output device by the above inside / outside determination is a hue angle in the JCH color perception space or the QMH color perception space.
It is mapped into the color gamut so that h (or H) is preserved. Then, this mapping result is converted to an LUT using the JCH color perception space as an input / output color space in the case of relative color matching, and Q in the case of absolute color matching.
It is stored in the LUT that uses the MH color perception space as the input / output color space.

FIG. 10 is a diagram showing the concept of color space compression between different devices. The broken line indicates the color reproduction area of the input device, and the solid line indicates the color reproduction area of the output device. In the JCH color perception space, the magnitude of J (lightness) is determined by the light source white point under observation conditions 1 and 2 (hereinafter, “white point”).
1), which may be abbreviated as "white point 2"), so J is the illuminance level for environmental conditions 1 and 2 (hereinafter sometimes abbreviated as "illumination level 1" and "illumination level 2") Does not depend on On the other hand, in the QMH color perception space, the magnitude of Q (brightness) changes depending on the illuminance levels 1 and 2. Therefore, in relative color matching, white point 1 becomes white point 2 as it is. On the other hand, in the absolute color matching, when illuminance level 1> illuminance level 2, white point 1 is mapped to white point 2. Also, the illumination level
If 1 <illuminance level 2, the white point 1 is lower than the white point 2 and is output as gray.

[Creation of Data Dependent on Observation Condition 2] Next, the conversion LUT 16 is created using the data creation unit 47.

FIG. 11 is a flowchart showing an example of processing for reconstructing the conversion LUT 16 corresponding to the ambient light.

In general, an ICC profile for an output device includes a CMYK or RGB value of a device based on XYZ or Lab values.
An LUT (BtoA0 Tag, etc.) for converting to a value is stored in a format that includes color space compression. However, since the XYZ values to be input to the LUT are data based on D50 or D65, they cannot be directly used as a conversion LUT according to ambient light.

Therefore, similarly to the color space compression processing, in step S71, the CMYK → X stored in the output profile 46 is output.
A conversion LUT (AtoB0 Tag or the like) for performing YZ conversion is read, and in step S72, CMYK → XYZ relation data is extracted from the conversion LUT. The CMYK value of the CMYK → XYZ relation data is RGB
Other device-dependent colors such as values may be used, and XYZ
The value may be a color independent of other devices, such as a Lab value. Next, in step S73, the output profile 46
The observation condition 2 stored in advance is taken out.

Since the XYZ values of the extracted CMYK → XYZ relation data are data based on D50 or D65, the XYZ values based on the colorimetric light source are corrected to the XYZ values based on the ambient light in step S74. In other words, the color perception model uses
Based on the colorimetric conditions (white point of D50 light source “D50 reference”, illuminance level, ambient light condition, etc.)
It is converted to human color perception space JCH, and converted back to XYZ values again based on observation conditions 2 (white point of D65 light source, illuminance level, ambient light condition, etc.) different from the colorimetric conditions, The XYZ values based on the color light source can be converted into the XYZ values based on the ambient light. As a result, the relationship from the device CMYK value to the XYZ value of the ambient light reference is obtained,
Then, using CMYK → ambient light XYZ related data, ambient light XYZ →
If the CMYK-related data is optimized using an iterative method or the like, a conversion LUT 16 corresponding to a desired ambient light can be obtained.

[Execution of Color Matching] FIG. 12 is a diagram showing the concept of color matching processing. 11 is a conversion LUT created by the data creation unit 41 based on the observation condition 1, 132
Is the LUT created on the JCH color space by the color space compression unit 44,
133 is an LU created on the QMH color space by the color space compression unit 45
T and 16 are conversion LUTs created by the data creation unit 47 based on the viewing condition 2.

The input color signal of RGB or CMYK is converted into a conversion LUT 1
1 converts the color signal of the input device into an XYZ signal which is a device-independent color signal under the viewing condition 1. Next, the XYZ signals are output to the color perception model forward conversion unit 134 and
Observation condition 1 (white point of D50 light source, illuminance level,
Is converted to a human perceptual signal JCH or QMH based on ambient light conditions. J for relative color matching
When the CH space is an absolute color matching, a QMH space is selected.

The color perception signals JCH and QMH are
33 compresses the data into the color reproduction range of the output device. The color perception signals JCH and QMH compressed in the color space are converted by the color perception model inverse transform units 136 and 137 into devices under the observation condition 2 based on the observation condition 2 (white point of the D65 light source, illuminance level, ambient light state, etc.). Is converted to an XYZ signal which is a color signal which does not depend on. Then, the XYZ signals are converted by the conversion LUT 134 into color signals depending on the output device under the viewing condition 2.

The RGB or CMY obtained by the above processing
The K signal is sent to the output device, and the image indicated by the color signal is printed out. When the printout is observed under the viewing condition 2, it looks the same color as the original document viewed under the viewing condition 1.

[0067]

Second Embodiment Hereinafter, as a second embodiment, an example in which color matching is performed using an input profile and a monitor profile shown in FIG. 13 will be described. The detailed description of the same configuration and processing as in the first embodiment is omitted.

[Creation of Data Dependent on Observation Condition 1] First, the conversion LUT shown in FIG. Create 21.

[Selection of Color Space Compression Mode and Color Space Compression] The selection of the color space compression mode is the same as that of the first embodiment, so that the detailed description is omitted.

FIG. 14 is a flowchart showing an example of processing for performing color space compression on the JCH 23 or QMH 24 shown in FIG.

To perform color space compression on the color perception space,
In step S141, a profile designated by the user is read from the monitor profile 142.

In general, a monitor device ICC profile may store a judgment LUT (gamut tag) for inputting an XYZ value or a Lab value in order to determine whether the color reproduction area is inside or outside. The value is a characteristic of the colorimetric light source D
Since it is based on 50 or D65, it cannot be used directly to determine whether the color reproduction area is inside or outside according to the ambient light. Therefore, instead of using the LUT (gamut Tag) that determines the inside / outside of the color reproduction area, the RGB → X stored in the profile
In step S142, RGB → XYZ related data is extracted from a conversion matrix (colorant tag) or a conversion LUT (AtoB0 Tag or the like) for performing YZ conversion and used. Since the monitor condition 4 is also stored in the monitor profile,
In step S143, the observation condition 4 is extracted from the monitor profile. Note that the XYZ values of the RGB → XYZ relation data may be colors that do not depend on other devices, such as Lab values.

Since the XYZ values of the RGB → XYZ relation data extracted in step S142 are data based on the colorimetric light D50 or the white point of the monitor, it is necessary to correct the XYZ values based on the ambient light. . In step S144, the XYZ values based on the colorimetric light source are calculated by the color perception model using the colorimetric condition D50.
Based on the white point of the light source `` in the case of D50 reference '', the luminance level and the state of the ambient light, etc., it is converted into the human color perception space JCH, and the white point of the D93 light source, which is an observation condition 4 different from the colorimetric condition , Based on the luminance level, the state of the ambient light, and the like, the XYZ values are again converted back to the XYZ values to obtain the XYZ values based on the ambient light. As a result, the relationship from the RGB values of the device to the XYZ values of the ambient light standard was obtained, and therefore, step S145
The color reproduction area of the monitor device in the JCH or QMH color space can be obtained by the following.

The color reproduction area of the monitor device is, for example, Red (R: 255, G: 0, B: 0) Yellow (R: 255, G: 255, B: 0) Green (R: 0, G: 255) , B: 0) Cyan (R: 0, G: 255, B: 255) Blue (R: 0, G: 0, B: 255) Magenta (R: 255, G: 0, B: 255) White (R : 255, G: 255, B: 255) Black (R: 0, G: 0, B: 0)

The XYZ values of the ambient light reference for the eight points are obtained by the conversion processing of the XYZ reference conditions in step S144, and further converted to the coordinate values of the human color perception space JCH or QMH based on the observation condition 4 by the color perception model By converting, the figure
It can be approximated by a dodecahedron as shown in FIG. In the color reproduction area approximated by a dodecahedron, points inside the color reproduction area, for example, White and Black on the achromatic axis
Is determined to be within the color gamut if the midpoint of the input color signal and the point (JCH value or QMH value) of the input color signal to be determined for inside / outside are on the same side, and is outside the color gamut if it is on the opposite side. Judge.

Based on the result of the inside / outside determination based on the color reproduction area obtained in step S145, color space compression is performed in step S146. FIG. 8 is a diagram illustrating the concept of color space compression in the JCH color perception space, and FIG. 9 is a diagram illustrating the concept of color space compression in the QMH color perception space. The input color signal determined to be out of the color reproduction range of the output device by the above inside / outside determination is a hue angle in the JCH color perception space or the QMH color perception space.
It is mapped into the color gamut so that h (or H) is preserved. Then, the color reproduction area obtained in step S146 is input / output to / from the LUT using the JCH color perception space as the input / output color space in the case of relative color matching, and to the QMH color perception space in the case of absolute color matching. LUT for color space
Is stored in

FIG. 10 is a diagram showing the concept of color space compression between different devices. A broken line indicates the color reproduction area of the input device, and a solid line indicates the color reproduction area of the output device. In the JCH color perception space, the magnitude of J (lightness) is determined by the light source white point under the viewing conditions 1 and 4 (hereinafter, “white point”).
1), which may be abbreviated as "white point 4", respectively, so J is the illuminance level of environmental condition 1 and the luminance level of environmental condition 4 (hereinafter "illuminance level 1" and "luminance level 4" (May be abbreviated). On the other hand, in the QMH color perception space, the magnitude of Q (brightness) changes depending on the illuminance level 1 and the luminance level 4. Therefore, in relative color matching, white point 1 becomes white point 4 as it is. On the other hand, in absolute color matching, the illuminance level
In the case of 1> luminance level 4, white point 1 is mapped to white point 4. When illuminance level 1 <luminance level 4, white point 1 is lower than white point 4, so that gray level is output.

[Creation of Data Dependent on Observation Condition 4] Next, the conversion LUT 26 shown in FIG.

FIG. 15 is a flowchart showing an example of processing for reconstructing the conversion LUT 26 corresponding to the ambient light.

The ICC profile for the monitor device includes an LU for converting the XYZ values to the RGB values of the device.
T (such as BtoA0 Tag) may be stored in a format that includes color space compression. However, the XYZ values to be input to the LUT are
Since the data is based on D50 or D65, it cannot be directly used as a conversion LUT according to ambient light.

Therefore, similarly to the color space compression processing, in step S151, the RGB stored in the monitor profile 142
→ Conversion matrix (colorant tag) for XYZ conversion
Or read the conversion LUT (AtoB0 Tag etc.) and step
In S152, RGB → XYZ related data is extracted from the conversion LUT.
Note that the XYZ values of the RGB → XYZ relation data may be colors that do not depend on other devices, such as Lab values. Next, in step S153, the observation condition 4 stored in the monitor profile 142 in advance is extracted.

Since the XYZ values of the extracted RGB → XYZ relation data are data based on D50 or the white point of the monitor, the XYZ values based on the colorimetric light source are corrected to the XYZ values based on the ambient light in step S154. I do. That is, based on the color perception model, the XYZ value of the colorimetric light source reference is used to calculate the human color perception space based on the colorimetric conditions (white point of D50 light source “D50 reference”, luminance level, ambient light condition, etc.). It is converted to JCH and converted back to XYZ values based on the viewing condition 4 (D93 light source white point, luminance level, ambient light condition, etc.) different from the colorimetric conditions, to obtain the XYZ The values can be converted to ambient light based XYZ values. As a result, the relationship from the device RGB values to the XYZ values of the ambient light standard was obtained.Therefore, in step S155, the RGB → XYZ conversion was modeled using a conversion matrix or the like and optimized using an iterative method or the like. The conversion LUT 26 corresponding to the ambient light can be obtained.

[Execution of Color Matching] FIG. 12 is a diagram showing the concept of color matching. 21 is the data creation unit 41
The conversion LUT 132 created on the basis of the viewing condition 1 by the LUT 133 created on the JCH color space by the color space compression unit 44
Is the LUT created on the QMH color space by the color space compression unit 45,
Reference numeral 26 denotes a conversion LUT created by the data creation unit 47 based on the viewing condition 4.

The input color signal of RGB is converted by the conversion LUT 21 from the color signal of the input device into an XYZ signal which is a device-independent color signal under the viewing condition 1. Then X
The YZ signal is converted into a human perception signal JCH or QMH by the color perception model forward conversion units 134 and 135 based on the viewing condition 1 (white point of D50 light source, illuminance level, ambient light state, etc.). In the case of relative color matching, the JCH space is selected, and in the case of absolute color matching, the QMH space is selected.

The color perception signals JCH and QMH are
33 compresses the data into the color reproduction range of the monitor device.
The color space compressed color perception signals JCH and QMH are converted by the color perception model inverse transform units 136 and 137 into the device under the observation condition 4 based on the observation condition 4 (white point of the D93 light source, luminance level, ambient light condition, etc.). XYZ, which is a color signal independent of color
Converted to a signal. Then, the XYZ signals are converted by the conversion LUT 26 into color signals depending on the monitor device under the viewing condition 4.

The RGB signal obtained by the above processing is sent to a monitor device, and an image indicated by the color signal is displayed. If the display is observed under observation condition 4, the original manuscript observed under observation condition 1 and
Looks the same color.

[0087]

Third Embodiment Hereinafter, as a third embodiment, an example in which color matching is performed using a monitor profile and an output profile shown in FIG. 16 will be described. The detailed description of the same configuration and processing as those of the first and second embodiments will be omitted.

[Creation of Data Dependent on Observation Condition 4] First, the conversion LUT 31 shown in FIG.

FIG. 17 shows a conversion LUT for adapting to ambient light.
31 is a flowchart illustrating an example of a process for updating 31.

In order to update the conversion LUT 31 corresponding to the ambient light, the profile designated by the user is read from the monitor profile 142 in step S161.

The ICC profile for the monitor has RGB → XYZ
Since a conversion matrix (colorant Tag) or conversion LUT (AtoB0 Tag) for conversion is stored, step S1
At step 62, RGB → XYZ related data is extracted. Since the observation condition 4 is also stored in the profile, the observation condition 4 is extracted from the profile in step S163. Where RGB → XY
The XYZ values of the Z-related data may be colors that do not depend on other devices, such as Lab values.

Since the extracted XYZ values of the RGB → XYZ relation data are data based on D50 or the white point of the monitor, the XYZ values based on the colorimetric light source are corrected to the XYZ values based on the ambient light in step S164. I do. That is, based on the color perception model, the XYZ value of the colorimetric light source reference is used to calculate the human color perception space based on the colorimetric conditions (white point of D50 light source “D50 reference”, luminance level, ambient light condition, etc.). It is converted to JCH and converted back to XYZ values based on the viewing condition 4 (D93 light source white point, luminance level, ambient light condition, etc.) different from the colorimetric conditions, to obtain the XYZ The values can be converted to ambient light based XYZ values. As a result, the relationship from the device RGB values to the XYZ values of the ambient light reference was obtained.In step S165, if the conversion matrix (colorantTag) or the conversion LUT (AtoB0 Tag) in the monitor profile 142 was updated, the desired A conversion LUT 31 corresponding to ambient light can be obtained.

[Selection of Color Space Compression Mode and Color Space Compression] The selection of the color space compression mode is the same as that of the first embodiment, and a detailed description thereof will be omitted. Also, the color space compression is the same as the processing shown in FIG. 6 of the first embodiment, and therefore the detailed description is omitted.

[Creation of Data Dependent on Observation Condition 2] Next, the conversion LUT 36 is created using the data creation unit 47.
This processing is also the same as the processing shown in FIG. 11 of the first embodiment, and thus the detailed description thereof will be omitted.

[Execution of Color Matching] FIG. 12 is a diagram showing the concept of color matching. 31 is the data creation unit 41
The conversion LUT 132 created based on the viewing condition 4 by the LUT 133 created on the JCH color space by the color space compression unit 44
Is the LUT created on the QMH color space by the color space compression unit 45,
Reference numeral 36 denotes a conversion LUT created by the data creation unit 47 based on the observation condition 2.

The RGB input color signal is converted by the conversion LUT 31 from the color signal of the monitor device into an XYZ signal which is a device-independent color signal under the viewing condition 4. Next, the XYZ signals are converted into human perception signals JCH or QMH by the color perception model forward converters 134 and 135 based on the viewing condition 4 (white point of the D93 light source, luminance level, state of ambient light, etc.). . In the case of relative color matching, the JCH space is selected, and in the case of absolute color matching, the QMH space is selected.

The color perception signals JCH and QMH are
33 compresses the data into the color reproduction range of the output device. The color perception signals JCH and QMH compressed in the color space are converted by the color perception model inverse transform units 136 and 137 into devices under the observation condition 2 based on the observation condition 2 (white point of the D65 light source, illuminance level, ambient light state, etc.). Is converted to an XYZ signal which is a color signal which does not depend on. Then, the XYZ signals are converted by the conversion LUT 36 into color signals depending on the output device under the viewing condition 2.

The CMYK signal obtained by the above processing is sent to the output device, and the image indicated by the color signal is printed out. When the printout is observed under observation condition 2, the image looks the same color as the image observed under observation condition 4.

[0099]

Fourth Embodiment In each of the above-described embodiments, a processing example in which the color matching module CMM dynamically converts a profile created from colorimetric values based on D50 or D65 into a profile depending on viewing conditions. However, by previously creating a profile that depends on static observation conditions, color matching corresponding to ambient light can also be performed.

In the following, a method of creating a profile depending on the observation condition for selecting a corresponding profile from a plurality of static profiles according to the observation condition will be described as a fourth embodiment.

[Creation of Profile Dependent on Source-Side Observation Conditions] D50 or D65 is set as a reference by the same processing as that of the data creation unit 41 for creating data dependent on the source-side observation conditions shown in FIG. Based on the profile created from the colorimetric values, the conversion LUT data 11 depending on the viewing conditions on the source side is created. Since the data 11 is already a conversion matrix or a conversion LUT for converting device RGB (or CMYK) values to XYZ (or Lab) values based on viewing conditions on the source side, the data 11 is stored in a profile as it is. For example, a profile that depends on the observation conditions on the source side can be created.

[Creation of Profile Dependent on Destination-side Observation Conditions] Color space compression unit 4 shown in FIG.
4, by the same processing as the processing of the color space compression unit 45 and the data creation unit 47, based on the profile created from the colorimetric values based on D50 or D65, JCH and Data 132 and 133 for performing a compression process in the QMH color space and data 16 for a conversion LUT depending on viewing conditions on the destination side are created.

Since the input / output color space of the data 132 is the JCH color space, it is necessary to set the input color space to XYZ (or Lab) values based on viewing conditions on the destination side. In order to create a conversion LUT for converting the XYZ values based on the viewing conditions on the destination side to the CMYK (or RGB) values of the device, the XYZ values for the input What is necessary is just to obtain the CMYK value of the device. In other words, the XYZ values based on the viewing conditions on the destination side are converted to the color perception based on the viewing conditions on the destination side using the human color perception model forward transform.
After converting to a JCH value and compressing it in the JCH color space with the data 132, the color perception JCH value is returned to the XYZ value based on the viewing conditions on the destination side again using the inverse conversion of the human color perception model, and finally the data By performing the conversion based on 134, the CMYK value of the desired device is obtained. LUT grid points
If required, a conversion LUT can be created.

Similarly, data 133 has an input / output color space of QMH
Since the color space is used, it is necessary to set the input color space to XYZ values based on viewing conditions on the destination side. To create a conversion LUT for converting the XYZ values based on the viewing conditions on the destination side into the CMYK values of the device, the CMYK values of the device with respect to the XYZ values based on the viewing conditions on the destination side to be input Should be obtained.
In other words, XY based on the observation conditions on the destination side
The Z value is converted to a color perception QMH value based on the viewing conditions on the destination side using the human color perception model forward conversion, compressed in the QMH color space by the data 133, and then converted back to the human color perception model Is used, the color perception QMH plant is returned to the XYZ values based on the observation conditions on the destination side again, and finally the conversion based on the data 134 is performed.
MYK value is determined. If the grid points of the LUT are sequentially obtained, a conversion LUT can be created.

An LUT including data 132 is an LUT used for relative color matching, and an LUT including data 133 is an LUT used for absolute color matching. If these are stored in one profile, a profile depending on viewing conditions on the destination side can be created. Here, the LUT used for relative color matching is based on a color space compression method (lightn compression) on the JCH color space.
esss storage, chroma storage, etc.). Similarly, a plurality of LUTs used for absolute color matching can be created and stored by using a color space compression method (brlightnesss storage, colorfulness storage, etc.) on the QMH color space.

[Execution of Color Matching] In color matching using a pro-profile depending on viewing conditions, color space compression is included in the profile on the destination side. There is no need to perform color space compression in space or QMH color space.

The color matching when a profile depending on the viewing condition is used will be described with reference to FIGS. 2, 13 and 16.

The input color signal is converted to a device RGB (or CMYK) by a profile depending on the viewing conditions on the source side.
XYZ (or Lab) based on source-side viewing conditions from values
Convert to a value.

Next, by the human color perception model forward conversion,
XYZ values based on viewing conditions on the source side can be converted to JCH color space or
Convert to QMH color space and convert to XYZ values based on viewing conditions on the destination side by inverse color perception model conversion. Here, the selection of the JCH or QMH color space is determined by the selection of the color space compression mode. The JCH color space is selected for relative color matching, and the QMH color space is selected for absolute color matching. In addition, the conversion from the XYZ values to the JCH or QMH color space uses source-side viewing conditions (white point of light source, illuminance or luminance level, state of ambient light, etc.) stored in the source-side profile, For the inverse transformation, the viewing conditions on the destination side (white point of light source, illuminance or luminance level, state of ambient light, etc.) stored in the profile on the destination side are used. XYZ (or La) based on the converted viewing conditions on the destination side
b) The values are converted to device CMYK (or RGB) values by a profile that depends on viewing conditions on the destination side.

As described above, the color matching processing using the profile depending on the viewing condition in the fourth embodiment is equivalent to the first to third embodiments.

[0111]

Fifth Embodiment In each of the above embodiments, a profile depending on the viewing condition is created from one type of colorimetric value stored in advance in the profile. The colorimetric data under a plurality of light sources is stored in the memory, and the colorimetric data closest to the actual observation condition is selected from the data, converted into the colorimetric data based on the observation condition, and depends on the observation condition. It is better to create a profile.

FIG. 20 is a conceptual diagram when the XYZ values of the white point of different light sources, the RGB values depending on the device of the color chart, and the XYZ values for the color chart under each light source are stored in the profile 191.

In the case of an input device, for example, an IT device
8 color targets, and in the case of an output device, for example, a 9 × 9 × 9 RGB color patch. For example, 192
Is the RGB value of the color chart and XYZ under A light source (109.85, 100.0, 35.58)
Value, 193 is the RGB value of the color chart and D65 light source (95.05, 100.0, 108.8
8) The lower XYZ value, 194 is the RGB value of the color chart and D50 (96.42, 100.0, 8
2.49) XYZ value under light source, 195 is RGB value of color chart and F2 (99.20, 10
0.0, 67.40) XYZ values under the light source. The XYZ values of the color patches under these different light sources can be obtained from the spectral distribution of each light source and the spectral reflectance of each color patch. Therefore,
Instead of the XYZ values, the spectral distribution of each light source and the spectral reflectance of each color chip can be stored in the profile 191. Here, if the color chart used in each profile is fixed, the RGB value and the spectral reflectance data of the color chart are common to each light source. Can be.

FIG. 21 shows the spectral distribution of the standard light source.
1 is the spectral distribution for the A light source, and 202 is the spectral distribution for the D65 light source. If the spectral distribution of the light source under the actual observation condition can be measured, a profile that depends on the observation condition with higher accuracy can be created.

As shown in FIG. 20, A, D65, D50 and F2
When the XYZ values under a plurality of standard light sources such as are stored in the profile, the XYZ values for the standard light source closest to the actual viewing condition are converted into the XYZ values for the viewing condition. In order to select an XYZ value under the light source closer to the viewing condition, the XYZ value of the white point of the light source stored in the profile is used for the search. For example, assuming that the white point of each light source is XwYwZw, its chromaticity (xw, yw) can be obtained by Expression (7). xw = Xw / (Xw + Yw + Zw) yw = Yw / (Xw + Yw + Zw)… (7)

Similarly, the chromaticity of the white point under observation conditions
When (x, y) is obtained from Expression (8), the distance dw between the white point of each light source and the white point under the viewing condition can be evaluated by, for example, Expression (9). x = X / (X + Y + Z) y = Y / (X + Y + Z)… (8) dw = √ {(x-xw) (x-xw) + (y-yw) (y-yw )}… (9)

From these results, if the colorimetric data closest to the actual viewing condition is selected, it is possible to obtain more accurate XYZ values for the viewing condition. Here, the method of converting the XYZ values stored in the profile into the XYZ values based on the viewing conditions is the same as in the above-described embodiment. A method is used in which the image data is converted into a human color perception space JCH on the basis of the image data and then converted back into XYZ values again based on an observation condition different from the colorimetric condition. When the distance dw between the white point of each light source and the white point under the viewing condition is zero, the colorimetric data can be used as XYZ values for the viewing condition. Others
The distance may be evaluated based on the difference between the color temperature Tw of the white point of each light source and the color temperature T of the white point under the viewing conditions.

FIG. 22 is a flowchart showing a process for estimating a colorimetric value from colorimetric data under a plurality of light sources. Here, Step S211 1, the step S 5 4 shown in FIG. 4, FIG. 5
Step S54, Step S 8 4 shown in FIG. 6 shown in FIG. 11
Step S74 shown in FIG. 14, step S144 shown in FIG. 14, FIG.
Step S1 5 shown in step S154 and FIG. 17 shown in 6
Equivalent to 4.

[Caching of Profile Data According to Observation Conditions] As described above, since the process of creating a profile depending on observation conditions is relatively complicated, it must be recalculated every time matching is attempted. It takes time. In normal use, once the viewing conditions on the source side and the viewing conditions on the destination side are set once, they are often used as they are, so it depends on the device-dependent color space and device based on the viewing conditions. The processing efficiency can be increased by caching LUTs and the like that convert color spaces to be converted to each other.

Since the viewing conditions can be set independently on the source side and the destination side, an LUT or the like that converts between a device-independent color space and a device-dependent color space based on viewing conditions can be cached for each profile. Is done. The cache destination is each profile or another cache file. The LUT to be cached may be only the LUT based on the currently used viewing condition, or the LUT based on a plurality of viewing conditions may be cached for each viewing condition.

For example, when ICC profiles are used, AtoBx Tag, BtoAx Tag, or ga
An LUT based on observation conditions corresponding to a mut Tag or the like is stored as a private tag.

FIG. 23 shows an example in which an LUT for mutually converting between a device-dependent color space based on viewing conditions and a device-dependent color space is stored in an ICC profile. Profile 221 with cached LUT
Are AtoB0 Tag 222, AtoB1 Tag223, AtoB2 Tag 224, Bt
oA0 Tag 225, BtoA1 Tag 226, BtoA2 Tag 227 and gam
ut Tag 228 is stored as a public tag. Here, the LUT stored as a public tag is for converting between a device-independent color space based on D50 and a device-dependent color space. Further, the profile 228 includes a public tag 2 as a private tag.
It includes LUTs 229 to 2215 for converting between a device-independent color space based on viewing conditions and a device-dependent color space corresponding to 22 to 227, respectively. The observation condition 2216 at the time of caching is stored in the private tag separately from the cached LUT.

FIG. 24 is a diagram showing an example of a processing flow of caching. The processing described below is independent processing on the source side and the destination side.

First, the observation condition VC is obtained from the user settings and the like. Next, the observation condition VC0 of the cached LUT is acquired from the profile 232. In the viewing condition VC and the viewing condition VC0, the viewing conditions are compared, for example, by comparing the white point of the light source. If the observation conditions match,
Since the same observation condition as when the LUT is cached can be considered, the cached LUT is used for color matching or the like. On the other hand, if the viewing conditions do not match, an LUT necessary for color matching or the like is created based on the viewing conditions.

The method of creating an LUT based on observation conditions is shown in FIG.
This is the same as the method described with reference to FIGS. 6, 7, 12, and 13. If the LUT to be cached is the source,
LUT 11 as shown in FIG. 12, and L on the destination side obtained by combining LUT 132 and conversion LUT 16 shown in FIG.
UT (that is, equivalent to the conversion LUTs 21 and 26 in FIG. 13). The viewing conditions at the time of creating the LUT and the LUT based on the viewing conditions are stored in a profile as private tags after being used for color matching or the like.

According to each embodiment described above, the following effects can be obtained.

(1) Different observation conditions (white point of ambient light, illumination level, etc.) can be set on the source side and the destination side of image data. For example, color reproduction in a remote environment connected to a network Can be simulated.

(2) Using a human color perception model, the XYZ values based on the ambient light on the source side are converted into the JCH color space and the Converted to QMH color space, and based on the viewing conditions on the destination side (ambient light white point, illuminance level, etc.), XYZ based on the ambient light on the destination side
By performing the inverse conversion to the value, the color matching can be performed by independently setting the viewing conditions on the source side and the destination side.

(3) QMH (or a human color perception space)
JCH) By performing color space compression on the color space, human color perception characteristics such as iso-hue lines can be reflected in the color space compression, and optimal color matching according to ambient light can be performed. .

(4) Color space compression can be selected from two modes, an absolute color matching performed in a QMH color space and a relative color matching performed in a JCH color space. Try the absoluteest possible color matching in the color reproduction area,
By performing relative color matching that maximizes the dynamic range of the color reproduction area on the output side, optimal color matching for the color reproduction area on the output side can be performed.

(5) Using a human color perception model, the colorimetric values (XYZ or Lab
Value) is converted to a value in the JCH color space based on colorimetric conditions (such as the white point of the colorimetric light source and the illuminance level), and further, based on the viewing conditions (such as the ambient light white point and the illuminance level).
By performing the inverse conversion to the XYZ (or Lab) value again, the XYZ value based on the colorimetric light source can be converted into the XYZ value based on the ambient light.

(6) The relational data between the data independent of the device of the color target measured under the standard light source and the data dependent on the device to which the data of the color target is input is stored in the input profile, and Depending on the observation conditions (such as ambient light white point and illuminance level)
By dynamically creating a conversion matrix or conversion LUT from device-dependent data to device-independent data, it is possible to perform color matching according to ambient light on the input side. In addition, a conversion matrix or conversion LUT for converting device-dependent data stored in the input profile into device-independent data (standard light source standard) is used for input-side viewing conditions (ambient light white point, illuminance level, etc.). , Etc.), color matching can be performed according to the ambient light on the input side.

(7) A conversion matrix or a conversion LUT for converting device-dependent data stored in the monitor profile into device-independent data (monitor white point reference or standard light source reference) is used as a monitor viewing condition. By dynamically updating according to the (environmental light white point, luminance level, etc.), color matching can be performed according to the monitor's ambient light.

(8) The relationship between the device-dependent data of the color patch and the device-independent data obtained by measuring the print output when the color patch is output under a standard light source is stored in an output profile and output. By dynamically creating a conversion LUT for converting device-independent data to device-dependent data according to the viewing conditions on the side (environmental light white point, illuminance level, etc.)
Color matching according to the ambient light on the output side can be performed.

[0135]

Sixth Embodiment In the sixth embodiment, the observation conditions (for example, Viewing Condition in FIG.
An example of a graphical user interface (GUI) for manually setting 1 and 2) will be described.

FIG. 25 shows a GUI 191 for setting the parameters of the viewing condition in this embodiment.

192 is a text box for inputting the luminance of the input-side visual target, 193 is a drop-down combo box for selecting the type of white point in the input-side visual target, and 194 is the input-side ambient condition. A drop-down combo box for selection, 195 is a text box for inputting the degree of color adaptation on the input side, 196 is a text box for inputting the luminance of the output-side visual target, and 197 is a text box for the output-side visual target. A drop-down combo box for selecting a white point, 198 is a drop-down combo box for selecting an ambient condition on the output side, and 199 is a text box for inputting a color adaptation degree on the output side.

The luminance is related to LA in the CIE CAM97S shown in FIG. 19, the light source is related to XwYwZw, and the ambient light is c, N
It is related to c, FLL and F, and the degree of adaptation is related to D. Figure
In the CIE CAM97S shown in FIG. 19, D is obtained based on LA and F. In this embodiment, D can be controlled manually.

[0139] The luminance of the visual target is usually 20% of the white point.
Enter about%. The type of white point in the viewing target originally requires the XYZ values of the white point in the viewing target, but here, for simplicity, it is assumed that there is a 100% reflectance white point in the media used. Use the white point of the light source. Further, it is better to use the white point of the light source under actual viewing conditions, but here, the type of the standard light source is selected. The types of standard light sources include A light source, C light source, D65 light source, D50 light source, D93 light source, F2 light source, F8 light source, and F11 light source. Since the image is targeted for the relative luminance of the background, it is assumed that the relative luminance is about 20%. As the surrounding condition, when the relative brightness of the surroundings is equal to or more than 20% as assumed as the relative brightness of the background, the average brightness is set as “
If it is less than that, it is “dim”, and if it is almost 0%, it is “dark”. The value is adjusted so that the chromatic adaptation degree is 1.0 for perfect adaptation and 0.0 for no adaptation.

[0140]

Seventh Embodiment Setting parameters for viewing conditions in the sixth embodiment is very difficult for ordinary users who are not color specialists, because it is necessary to input values directly. Therefore, in the seventh embodiment, the GUI 191 of the sixth embodiment is used.
To improve usability.

The characteristic structure of this embodiment is as follows. (1) Switch the display of parameter settings according to the level of the user. (2) The user adjusts the degree of color adaptation by designating the interval between the source side viewing target and the destination side viewing target. (3) The user adjusts the balance of the degree of color adaptation between the source side viewing target and the destination side viewing target. (4) The user adjusts the absolute degree of chromatic adaptation while maintaining the balance of the degree of chromatic adaptation between the source side target and the destination side target.

FIG. 26 shows a GUI 201 in which a user level can be set.
In the figure, “general user” is selected as the user level. In the GUI 201, the user does not need to input parameters directly, and all environmental conditions can be set by selection and a slide bar. further,
Each selection is also expressed in a manner that is easy for general users to understand.

In FIG. 26, reference numeral 202 denotes a drop-down combo box for selecting a user level, reference numeral 203 denotes a drop-down combo box for selecting an input-side visual target, and reference numeral 204 denotes a luminance level of the input-side visual target. Drop-down combo box for selecting the type of white point in the visual object on the input side, 205 is a drop-down combo box for selecting the ambient conditions on the input side, and 207 is the output Drop-down combo box for selecting the visual object on the side, 208 is a drop-down combo box for selecting the luminance level in the visual object on the output side, and 209 is for selecting the type of white point in the visual object on the output side Drop-down combo box, 2010 is a drop-down combo box for selecting ambient conditions on the output side Bobokkusu, 20
Reference numeral 11 denotes an icon indicating the input side viewing target in the observation interval setting, and reference numeral 2012 denotes an icon indicating the output side viewing target in the observation interval setting.

By specifying a drop-down combo box 202 for selecting a user level, the displayed user level is switched, for example, as shown in FIG. The items to be viewed can be selected from items such as "monitor", "document", "print", and the like, and the items of the selection menu and the actual values set according to the items differ depending on the selected item. . The selection of the brightness level in the viewing target is for general users, and is a perceptual selection item such as “bright”, “slightly bright”, “average”, and “slightly dark”. For the selection of white point in the viewing target, "white", "white", "orange white" for monitors and "white fluorescent lamp" and "white fluorescent" for originals and prints do not use expressions such as D93 and F2 for general users. The expressions are daylight white fluorescent light, incandescent light, outdoor fine weather, and outdoor cloudy weather.

The observation interval setting is to adjust the interval of the viewing target by, for example, a case where the monitor and the print are directly arranged side by side and a case where the comparison is made at a distant position using a slide bar. I do. In order to make it easy for the user to perceive sensibly, the visual target is iconized, and the distance between the icons is adjusted with a slide bar.

In CIE CAM97s, the degree of chromatic adaptation is defined by the following equation. Perfect adaptation: D = 1.0 No adaptation: D = 0.0 Incomplete adaptation: D = F-F / {1 + 2 · La∧ (1/4) + (La∧2) / 3
00}

Here, D is the degree of chromatic adaptation. F is a constant that varies depending on the ambient conditions, and is 1.0 for average brightness and 0.9 for dim or dark. La is the luminance of the viewing target. The degree of color adaptation D can be set independently on the input side and the output side. Note that a∧b represents a raised to the power of b.

In the present embodiment, the degree of chromatic adaptation on the input side and the output side is defined such that the degree of chromatic adaptation changes depending on the distance (observation distance) between the input side visual target and the output side visual target. Assuming that the observation distance is close to perfect adaptation when the observation distance is infinite, it can be defined as follows, for example. Ds0 = Fs-Fs / {1 + 2 ・ Las∧ (1/4) + (Las∧2) / 300} Dd0 = Fd-Fd / {1 + 2 ・ Lad∧ (1/4) + (Lad∧2 ) / 300} Ds = Ds0 ・ VD + Ds0 ・ VD0 ・ (1.0-VD) Dd = Dd0 ・ VD + Dd0 ・ VD0 ・ (1.0-VD)

Here, Ds0 is the degree of chromatic adaptation on the input side determined by the luminance level and the surrounding conditions. Fs is a constant that changes depending on the ambient conditions on the input side. Las is the luminance of the viewing object on the input side. Dd0 is the degree of chromatic adaptation on the output side determined by the luminance level and the surrounding conditions. Fd is a constant that changes depending on the ambient conditions on the output side. Lad is the luminance of the output side viewing target. Ds is the degree of color adaptation on the input side determined by the viewing distance, luminance level, and ambient conditions. Dd is the degree of chromatic adaptation on the output side determined by the viewing distance, luminance level, and ambient conditions. VD is the position of the slide bar indicating the observation distance. When the observation distance is zero, the minimum value is 0.0, and when the observation distance is infinite, the maximum value is 1.0. VD0 is a constant that determines the degree of chromatic adaptation when the viewing distance is zero.

FIG. 27 shows an example of the GUI 211 when the user level is designated as “professional”.
Since the subject is an expert, the parameter can be directly input and the expression is also specialized.

Here, 2111 is a static text for displaying the chromatic adaptation value of the input-side viewing condition, 2112 is a static text for displaying the chromatic adaptation value of the output-side viewing condition, and 2113 is the input side viewing target. A slide bar for adjusting the balance of the degree of chromatic adaptation between the target and the output side, 2114 is for adjusting the absolute degree of chromatic adaptation while maintaining the balance of the degree of chromatic adaptation between the input side and the output side Slide bar.

In order to adjust the degree of chromatic adaptation by the balance and the absolute intensity, the degree of chromatic adaptation on the input side and the output side is defined as follows. Ds0 = 1.0-BL Dd0 = BL Ds = Ds0 / MAX (Ds0, Dd0) × VL Dd = Dd0 / MAX (Ds0, Dd0) × VL

Here, Ds0 is the degree of color adaptation on the input side determined by the balance adjustment of the degree of color adaptation. Dd0 is the degree of color adaptation on the output side determined by the balance adjustment of the degree of color adaptation. BL is the position of the slide bar indicating balance. The minimum value is 0.0 when the input side is 100%, the maximum value is 1.0 when the output side is 100%, and the center is 0.5. Ds is the degree of color adaptation on the input side determined by the balance of the degree of color adaptation and the absolute intensity adjustment. Dd is the degree of color adaptation on the output side determined by the balance of the degree of color adaptation and the absolute intensity adjustment. VL is the position of the slide bar indicating the absolute intensity. When the intensity is zero, the minimum value is 0.0, and when the intensity is the maximum, the maximum value is 1.0. Note that the function MAX () is
Is the function that takes the maximum value of

The balance adjustment is adjusted so that the greater the balance strength, the more perfect the adjustment, and the absolute strength is adjusted as a whole while maintaining the balance. In other words, if the balance is at the center and the absolute intensity is the maximum, the chromatic adaptation degrees on the input side and the output side are both perfect adaptation.

[0155]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to supply a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU or MPU) of the system or apparatus.
Needless to say, this can also be achieved by the PU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the OS running on the computer based on the instructions of the program code.
It goes without saying that an (operating system) performs a part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0158]

As described above, according to the present invention,
Regardless concerning the viewing conditions, achieve high color matching precision
It can be.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of general color matching,

FIG. 2 is a diagram for explaining the concept of the present invention;

FIG. 3 is a block diagram showing a functional configuration example of the first embodiment;

FIG. 4 is a flowchart illustrating a processing example of reconstructing a conversion LUT corresponding to ambient light;

FIG. 5 is a flowchart showing an example of processing for updating to a conversion LUT corresponding to ambient light;

FIG. 6 is a flowchart illustrating a processing example of performing color space compression on a JCH or QMH color space;

FIG. 7 is a diagram showing a dodecahedron approximating a color reproduction area;

FIG. 8 is a diagram showing the concept of color space compression in the JCH color perception space;

FIG. 9 is a diagram showing the concept of color space compression in the QMH color perception space;

FIG. 10 is a diagram showing the concept of color space compression between different devices;

FIG. 11 is a flowchart illustrating a processing example of reconstructing a conversion LUT corresponding to ambient light;

FIG. 12 is a diagram showing the concept of color matching processing;

FIG. 13 is a diagram showing color matching in the second embodiment;

FIG. 14 is a flowchart illustrating a processing example of performing color space compression on a JCH or QMH color space according to the second embodiment;

FIG. 15 shows conversion L corresponding to ambient light in the second embodiment.
Flowchart showing a processing example of reconstructing the UT,

FIG. 16 is a diagram showing color matching in the third embodiment;

FIG. 17 is a flowchart illustrating a processing example of updating a conversion LUT to correspond to ambient light in the second embodiment;

FIG. 18 is a block diagram showing a configuration example of an apparatus for realizing the functional configuration shown in FIG. 3;

FIG. 19 is a diagram illustrating a color perception model used in the embodiment according to the present invention;

FIG. 20 is a conceptual diagram in which the XYZ values of the white point of different light sources, the RGB values depending on the device of the color chart, and the XYZ values for the color chart under each light source are stored in a profile.

FIG. 21 is a diagram showing a spectral distribution of a standard light source;

FIG. 22 is a flowchart showing processing for estimating a colorimetric value from colorimetric data under a plurality of light sources;

FIG. 23 is an LU for mutually converting between a device-independent color space based on viewing conditions and a device-dependent color space.
The figure showing an example when T is stored in the ICC profile,

FIG. 24 is a diagram showing an example of a processing flow of caching;

FIG. 25 is a view showing a GUI for setting parameters of observation conditions in the sixth embodiment;

FIG. 26 is a diagram showing an example of a GUI in which a user level can be set;

FIG. 27 is a diagram illustrating an example of a case where a user level is designated as “professional” in the GUI illustrated in FIG. 26;

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Claims (5)

(57) [Claims] 1. Obtaining an observation condition, selecting colorimetric data dependent on a light source close to the obtained observation condition from a plurality of colorimetric data dependent on a plurality of light sources held in a profile, and selecting A conversion process using a color perception model is performed on the colorimetric data obtained, colorimetric data corresponding to the viewing condition is estimated, and color matching conversion data corresponding to the viewing condition is estimated from the estimated colorimetric data. An image processing method, comprising the steps of: obtaining colorimetric data, wherein the colorimetric data is data in a device-independent color space associated with data in a device-dependent color space. 2. The colorimetric data according to the viewing condition is selected based on a comparison between the chromaticity of the light source under the viewing condition and the chromaticity of the light source in the colorimetric data. The image processing method described in 1. 3. The color temperature of a light source under the viewing condition,
2. The image processing method according to claim 1, wherein colorimetric data according to the viewing condition is selected based on a comparison between the colorimetric data and a color temperature of a light source. 4. An acquisition unit for acquiring an observation condition, and colorimetric data dependent on a light source close to the acquired observation condition are selected from a plurality of colorimetric data dependent on a plurality of light sources held in a profile. Selecting means for performing a conversion process using a color appearance model on the selected colorimetric data, and estimating means for estimating colorimetric data corresponding to the observation conditions; and performing the observation from the estimated colorimetric data. Creating means for creating color matching conversion data corresponding to a condition, wherein the colorimetric data is data in a device-independent color space associated with device-dependent color space data. Characteristic image processing device. 5. A recording medium in which a program code for image processing is recorded, wherein the program code includes at least a code for a step of acquiring an observation condition, and colorimetric data dependent on a light source close to the acquired observation condition. A code of a step of selecting from a plurality of colorimetric data dependent on a plurality of light sources held in a profile, and performing a conversion process using a color perception model on the selected colorimetric data, and performing the observation A code of a step of estimating colorimetric data corresponding to the condition, and a code of a step of obtaining color matching conversion data corresponding to the observation condition from the estimated colorimetric data, wherein the colorimetric data is transmitted to a device. A recording medium, which is data in a device-independent color space associated with data in a dependent color space.