JP2002094817A - Image-processing method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To periodically calibrate a colorimetry error due to the characteristic change in a light source and a light receiving element caused by the change in environment (temperature and humidity) and aging in a colorimeter to inhibit the error. SOLUTION: A counter N is initialized to 1 (S202), and a colorimetry head is moved onto a reference white board for calibration (S203-S204). Then, the colorimetry head is moved onto a color patch at the left side of the Nth column to perform the colorimetry of the color patch (S205-S207). Then, it is judged whether the colorimetry head has reached the right side of a colorimetry range or not, or the lower side of the colorimetry range or not (S208 and S210). If they have not reached, the counter N is incremented (S211), thus repeating steps S203-S210.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image processing apparatus and a method thereof, for example, to a color reproduction process of a printer.

[0002]

2. Description of the Related Art In a color reproduction process of a printer or a printing press, as a method of performing color correction for improving a color reproduction effect, a color masking that performs a matrix operation on data of an input color space to obtain data of an output color space. A method of converting input color space data into output color space data using a look-up table (LUT) called a profile or a profile is often used.

However, output characteristics of color printers and printing presses exhibit strong nonlinearity. Therefore, a global method such as a color masking method, that is, a color correction method in which changing the elements of a matrix affects the entire output color space, sufficiently approximates the characteristics of a color printer or printing machine in all color gamuts. I can't. Even if a profile is provided, a table is often required by a color masking method, and the difficulty in color reproduction remains unchanged.

Therefore, the applicant has proposed a method of accurately approximating the strong non-linear output characteristics of a color printer or a printing machine, and providing a profile that enables highly accurate color reproduction.

[0005]

When a profile is created, the color of a color patch of a sample image printed by a color printer or a printing machine is measured by a colorimeter. At the time of this color measurement, calibration is periodically performed to suppress a color measurement error.

An object of the present invention is to perform efficient calibration in colorimetry for providing a profile.

[0007]

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

An image processing method according to the present invention is an image processing method for sending color patch data to an output device to output a color patch, causing the color patch to read the color patch, and inputting the read result. When reading the color patches, the colorimeter is caused to perform calibration using a white plate arranged at a predetermined position according to the arrangement of the color patches.

An image processing apparatus according to the present invention is an image processing apparatus that sends color patch data to an output device to output a color patch, causes the color patch to read the color patch, and inputs the read result. Having control means for controlling the operation of the colorimeter, wherein the control means comprises:
According to the present invention, the colorimeter performs calibration using a white plate arranged at a predetermined position according to the arrangement of the color patches.

[0010]

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.

[0011]

First Embodiment [Configuration] FIG. 1 is a block diagram showing a configuration example of an image processing apparatus according to an embodiment.

A signal input to the image processing apparatus shown in FIG. 1 is an image signal of a color space depending on some device,
For example, an RGB signal indicating an image read from a document by a scanner, or a C signal to be output to a printer.
It may be a MYK signal. When the present embodiment is applied to a copying machine, the input signal is an RGB signal indicating an image read by a scanner. In the case of proofing (test printing or proof printing), it is a CMYK signal output to the target printing machine.

Such an input signal is input to an input color → Lab conversion unit 101, and is output to a Lab which is a device-independent color space.
It is converted to a color space signal. This conversion is performed by input color → Lab
This is realized by LUT conversion using the conversion LUT.

In the table of the input color → Lab conversion LUT 102,
It is necessary to set a table corresponding to the color space of the input signal. For example, when an image signal dependent on the RGB color space of the scanner A is input, a three-dimensional input representing a correspondence between an RGB value and a Lab value depending on the RGB color space of the scanner A-a three-dimensional output RGB → Lab The conversion table is set as a table of the input color → Lab conversion LUT102. Similarly, printer B CMYK
When an image signal dependent on the color space is input, the CMYK → Lab conversion table of the four-dimensional input-three-dimensional output representing the correspondence between the CMYK value dependent on the color space of the printer B and the Lab value is input color → Lab Set as a table of conversion LUT102.

FIG. 2 is a diagram showing an example of an RGB → Lab conversion table, showing the correspondence between 8-bit RGB values and Lab values. Since the actual table stores Lab values with typical RGB values as addresses, the input color → Lab conversion unit
101 extracts Lab values near the input RGB value from the table, and interpolates the extracted Lab value to obtain a Lab value corresponding to the input RGB value.

Lab output from input color → Lab conversion unit 101
The signal is converted to the device R by the Lab → device RGB converter 104.
It is converted into a signal in the device RGB color space based on the GB → Lab conversion LUT 105. Details of this conversion processing will be described later.

When the color space of the input signal is the RGB color space, the color gamut is often wider than the color gamut of the printer. Therefore, the Lab signal output from the input color → Lab conversion unit 101 is converted by the color space compression conversion unit 103 into a printer.
Mapping to 107 color reproduction ranges (Gamut mapping)
After that, the data is input to the Lab → device RGB conversion unit 104. The specific method of gamut mapping is disclosed in
A method of performing a color space compression process in a uniform color space disclosed in Japanese Patent Publication No. 130655 may be used.

The signal in the device RGB color space output from the Lab → device RGB conversion unit 104 is converted into a signal in the CMYK color space dependent on the printer 107 by the device RGB → CMYK conversion unit 106, and is then sent to the printer 107. Sent. There are various methods for RGB → CMYK conversion, and any method may be used. For example, the following conversion formula is used. C = (1.0-R)-KM = (1.0-G)-KY = (1.0-B)-KK = min {(1.0-R), (1.0-G), (1.0-B)}

[Lab → Device RGB Conversion] Next, the Lab → device RGB conversion unit 104 will be described in detail.

The Lab → device RGB converter 104 converts the signal based on the correspondence between the device RGB values and the Lab colorimetric values obtained in advance. FIG. 3 is a flowchart showing a procedure for performing Lab → device RGB conversion by obtaining a correspondence relationship of device RGB value⇔Lab colorimetric value. Of course, if the relationship of RGB value / Lab colorimetric value has already been obtained, steps S1 and
S2 is omitted.

Step S1 The color patch generator 108 generates a sample image composed of a plurality of color patches as shown in FIG. Then, the RGB signal of the generated sample image is converted to the device RGB →
The image is output to the printer 107 through the CMYK conversion unit 106, and a sample image 109 is obtained.

The sample image generated by the color patch generation unit 108 is generated so as to equally divide the device RGB color space. In the example of FIG. 4, 729 patches are obtained by equally dividing the RGB color space of 8 bits each into 9 × 9 × 9. Originally, the color space dependent on the printer 107 is a CMYK color space, but the RGB color space is a color space dependent on the printer 107 in the sense that it can be converted to the CMYK color space by a conversion rule from the RGB color space. Think.

Step S2 Each color patch of the obtained sample image 109 is measured by the color patch colorimeter 110 to obtain a Lab colorimetric value of each color patch. The obtained Lab colorimetric values are as shown in FIG.
Distributed in Lab color space. By this operation, the RGB values generated by the color patch generation unit 108 and the Lab colorimetric values measured by the color patch colorimeter 110 are obtained, and the device RG
A table of the B → Lab conversion LUT 105 can be obtained. Lab → Device RGB using this device RGB → Lab conversion LUT105
Perform the conversion.

When the LUT is used, an interpolation operation such as cubic interpolation or tetrahedral interpolation, which is a known method, is used. In these interpolation calculations, grids corresponding to the input side of the LUT need to be equally spaced. Although the device RGB values in the table of the device RGB → Lab conversion LUT 105 are evenly arranged, the Lab colorimetric values are not evenly arranged. For this reason, when inputting Lab values, device RGB → Lab conversion L
The table of UT105 does not constitute an LUT with a grid at equal intervals. Therefore, it is not possible to simply perform the interpolation operation for inputting the Lab value. Therefore, Lab →
Perform device RGB conversion.

[Step S3] Lab included in the table of the device RGB → Lab conversion LUT105
The distance d between the value and the input Lab value (equivalent to the color difference by the Lab color difference formula) is calculated and stored in the memory.

Step S4 As shown in FIG. 6, N entries (●) are selected in ascending order of the distance d with respect to the input Lab value (◎). At this time, the distance d is described as follows in ascending order. Where d ₁ <d ₂ <d ₃ <… <d _N

Step S5 The conversion value (RGB value) for the input Lab value is calculated by the following equation. RGB = (1 / N) × Σ _{i = 1} ^N RGBi × f (di) where f (x) = 1 / (1 + x ⁴ )

Since the function f (x) has characteristics as shown in FIG. 7, the calculation using the above equation gives a larger weight to the RGB values corresponding to the Lab colorimetric values that are closer in the Lab color space. Means that the interpolation calculation is performed.

The number N of sample points used in the interpolation operation is represented by Lab
It can be a constant (for example, 8) over the entire color space. However, depending on the conversion method in the device RGB → CMYK conversion unit 106, as shown in FIG. 5, since the colorimetric values are concentrated in an area where the lightness L * is low, inconvenience may occur when N is a constant. In other words, in a region where colorimetric values are concentrated, the distance d is extremely small, and when N is small, a small number of sample points are weighted with a large weight and interpolation calculation is performed. As a result, a gradation jump in the device RGB color space is performed. In addition, problems such as collapse of white balance in a low brightness area are likely to occur.

Therefore, as shown in FIG. 8, the input Lab value L *
If the number of sample points is changed according to the value and the interpolation calculation is performed, the above problem can be effectively solved. Of course, even in a region having a high lightness, the number of samples used for the interpolation calculation is limited, and color turbidity and the like hardly occur. Note that an example of the function N (L *) shown in FIG.
8, a 1/4 power function that becomes 4 when L * = 100.

By repeating the processing of steps S3 to S5 for all input Lab values, the Lab signal can be converted to a device RGB signal.

[0032]

Second Embodiment Hereinafter, an image processing apparatus according to a second embodiment of the present invention will be described. Note that, in the present embodiment,
Components that are substantially the same as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

FIG. 9 is a block diagram showing a configuration example of the image processing apparatus according to the second embodiment. The image processing apparatus according to the second embodiment converts the device-independent color space signal to the printer 107 color space signal in the same manner as when converting an input signal into a device-independent color space signal. First in terms of doing with LUT
This is different from the image processing apparatus of the embodiment.

The Lab → CMYK conversion unit 803 is a Lab → CMYK conversion LUT
Using 804, the Lab signal is converted into a signal in the CMYK color space dependent on the printer 107. The CMYK signal output from the Lab → CMYK conversion unit 803 is sent to the printer 107. Lab → CMYK conversion LU
T804 is created as follows.

The RGB signal of the sample image generated by the color patch generation unit 108 is converted into a CMYK signal dependent on the printer 107 by the device RGB → CMYK conversion unit 106, and is output to the printer 107. can get.

Each color patch of the obtained sample image 109 is measured by the color patch colorimeter 110 to obtain a Lab colorimetric value of each color patch. Based on the obtained Lab colorimetric values and the RGB values generated by the color patch generation unit 108, Lab → C
The MYK conversion LUT creation unit 810 creates a table of Lab → CMYK conversion LUT 804.

The processing of the Lab → CMYK conversion LUT creation section 810 is performed in the first
CMYK obtained by performing the device RGB → CMYK conversion processing described in the embodiment on the RGB values generated by the color patch generation unit 108
A table of Lab → CMYK conversion LUT804 is created from the values and Lab colorimetric values. For example, if the Lab value is an 8-bit signal, L *
Values range from 0 to 255, a * and b * values range from -128 to 127. If the Lab grid is constructed by carving each range of Lab in 16 steps, Lab → CMYK conversion LUT by 17 ³ = 4913 calculations
804 tables are completed.

In the first embodiment, after converting from the Lab color space to the device RGB color space by the LUT, the device RGB color space is converted to the CMYK color space by arithmetic processing.
In the second embodiment, these conversion processes can be performed by one LUT, and the conversion process can be made more efficient.

[0039]

Third Embodiment Hereinafter, an image processing apparatus according to a third embodiment of the present invention will be described. Note that, in the present embodiment,
Components that are substantially the same as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

FIG. 10 is a block diagram showing an example of the configuration of an image processing apparatus according to the third embodiment, which has a configuration for inputting an input signal in the sRGB color space, which has recently become a standard color space on the Internet. The sRGB color space defines the correspondence with the XYZ color space, and can be considered as a device-independent color space. Therefore, if the sRGB values are converted to XYZ values or Lab values, and the above-described conversion from the Lab color space to the printer color space is performed, the image represented by the signals in the sRGB color space is reproduced by the printer 107. It becomes possible to do.

In FIG. 10, the sRGB → CMYK conversion unit 901
The input signal in the sRGB color space is converted into a signal in the CMYK color space dependent on the printer 107 by using the RGB → CMYK conversion LUT 902. s
The CMYK signal output from the RGB → CMYK conversion unit 901 is
Sent to 107. The sRGB → CMYK conversion LUT 902 is created as follows.

The RGB signal of the sample image generated by the color patch generation unit 108 is converted into a CMYK signal dependent on the printer 107 by the device RGB → CMYK conversion unit 106, and is output to the printer 107. can get.

Each color patch of the obtained sample image 109 is measured by the color patch colorimeter 110 to obtain a Lab colorimetric value of each color patch. Based on the obtained Lab colorimetric values and the RGB values generated by the color patch generator 108, sRGB →
The CMYK conversion LUT creation unit 908 creates a table of the sRGB → CMYK conversion LUT 902.

The processing of the sRGB → CMYK conversion LUT creation unit 908
CMYK obtained by performing the device RGB → CMYK conversion processing described in the first embodiment on the RGB values generated by the color patch generation unit 108
Lab → XYZ and XYZ → sR according to the formula and the defined formula for Lab colorimetric values
SRGB to CMYK conversion LUT902 from sRGB value obtained by performing GB conversion
Create a table. For example, assuming that the sRGB signal is an 8-bit signal, each sRGB range is divided into 16 steps at 17 × 17
If a sRGB grid of × 17 is configured, a table of sRGB → CMYK conversion LUT902 is completed by 17 ³ = 4913 calculations.

According to each of the embodiments described above, it is possible to provide a color conversion method capable of accurately approximating the strong non-linear output characteristics of a color printer or a printing machine and enabling high-precision color reproduction. Therefore, in a device-independent color space, a color space conversion that favorably reflects the characteristics of a printer or a printing press is performed.
High-precision color reproduction is possible with printers and printing presses.

In the above embodiment, the color space independent of the device is described as the Lab color space. However, the same effect can be obtained by using another uniform color space, for example, a Luv color space. .

[0047]

[Fourth Embodiment] For the purpose of proofing (test printing, proof printing), there is a case where a color-converted image is printed by a copying machine or a printer in accordance with the output characteristics of a printing machine as a target. In order to perform such proofing, according to the method described in each of the above-described embodiments, sample image data is supplied to an output device used for proofing and printed. You need to create a profile. Then, an image that has been subjected to color conversion using the created profile is printed by the output device.

Hereinafter, a process of creating a profile of an output device used for proof and a colorimetric process at that time will be described as a fourth embodiment. The creation of the profile described in the fourth embodiment is not limited to the proof,
Needless to say, it can be used for normal output (printing).

[Configuration of Color Conversion Module] First, an outline of a configuration for performing color conversion will be described. FIG. 11 is a block diagram illustrating a configuration example of the color conversion module.

A colorimeter (spectrophotometer) 1001 and a colorimetric module 1002 measure the color of each color patch of a sample image (for example, a standard IT8 or 4320 CMYK image) printed by an output device. The colorimetric results are supplied to the profile generation module 1003 online or offline, and the ICC (Inte
Profile 1101D (Lab → CMYK), which is an output device profile according to the definition of the rnational Color Consortium)
A conversion LUT: BtoA0) and a profile 1101S (device value → Lab conversion LUT: AtoB0) are created.

The preview module 1005 converts the image 1006 to be proofed, the profile (target device value → Lab conversion LUT) 1102 corresponding to the target device, the profiles 1101D and 1101S of the output device, and the monitor profile 1103 into the color management module (CMM). ) 1007 to supply (or instruct) the image 1006 to undergo color conversion.

[Creation of Profile] Next, creation of a profile of an output device will be described in detail. FIG.
FIG. 9 is a diagram for explaining a procedure for creating a profile of an output device, and is a diagram for more simply explaining the processing described in the second embodiment.

An output device 1010 outputs the device CMYK data of the sample image selected by the user from the memory 1012.
To print the sample image 1011. As the sample image, for example, a standard IT8 or 4320 CMYK image is used.

Each color patch of the sample image 1011 printed by the output device 1010 is measured by the colorimeter 1001 and the colorimetric module 1002, and the Lab colorimetric value is stored in the memory 1012. Profile generation module 10
03 is the device corresponding to the AtoB0 tag of the ICC profile
A CMYK → Lab conversion table 1013 is generated and stored in the memory 1012.

Considering the preview function, a BtoA0 tag is required in addition to the AtoB0 tag. Therefore, the profile generation module 1003 uses the device CMYK → Lab conversion table 1
A Lab → device CMYK conversion table 1014 is created from 013. Note that these conversion tables are finally stored in the memory 1012 as ICC profiles of the output device 1010.

By the way, although the device CMYK values in the device CMYK → Lab conversion table 1013 are evenly arranged,
Lab colorimetric values are not evenly aligned. Input Lab value
When creating Lab → Device CMYK conversion table 1014, L
Ab values must be evenly spaced. Therefore, using the method described in the first embodiment, from the device CMYK → Lab conversion table 1013, Lab → device CMYK in which Lab values are evenly arranged
A conversion table 1014 is created and stored in the memory 1012.

FIG. 13 shows a Lab → device CMYK conversion table 101.
FIG. 4 is a diagram for explaining the creation of No. 4. Table input values in Lab → Device CMYK conversion table 1014 (Lab ₁ ', Lab ₂ ', Lab
₃ ',…) and device CMYK → Lab conversion table 1013
Are input at equal intervals (CMYK ₁ , CMYK ₂ , CMYK ₃ ,...). However, device CMYK → Lab
Lab measurement values in the conversion table 1013 (Lab ₁ , Lab ₂ , La
b ₃ ,…) are not arranged at equal intervals.

Therefore, the table input value Lab _i ′ is interpolated from the previous and next Lab measurement values. For example, Lab ₁ ′ in FIG. 13 is interpolated by the following equation. Lab ₁ '= a / (a + b) × (CMYK ₂ -CMYK ₁ ) + CMYK ₁ = b / (a + b) × CMYK ₁ + a / (a + b) × CMYK ₂ where a = Lab ₁ '-Lab ₁ b = Lab ₂ -Lab ₁ '

[Calibration of Colorimeter] Colorimeter 10
In 01, a colorimetric error occurs due to a change in the characteristics of the light source and the light receiving element due to environmental (temperature, humidity) fluctuations, temporal changes, and the like. In order to suppress this error, it is necessary to perform calibration periodically.

FIG. 14 is a diagram showing an overview of the colorimeter 1001.
The colorimetric head 2003 is controlled by the beam 2002 and the arm 2003.
It is movable in X and Y directions. Colorimetric surface 2004 (for example, A4
Sample image is placed on the
Thereby, the colors of the respective color patches of the sample image are sequentially read. For the above calibration, the reference white plate 2005 is read before the start of color measurement, and the reference white plate 2005 is read periodically during color measurement.

The calibration can be performed at various intervals such as a predetermined time and a predetermined number of color measurements. However, considering that a plurality of color patches arranged on the sample image are measured in order, it is not efficient to perform the measurement at intervals such as a predetermined time and a predetermined number of times of color measurement. Therefore, in the fourth embodiment, calibration is performed in consideration of the movement of the arm 2003.

[Colorimetric Procedure] FIG. 15 is a flowchart showing an example of a colorimetric procedure by the colorimeter 1001.
This is the process performed by U.

The colorimetric control data including the colorimetric parameters such as the colorimetric range is received from the colorimetric module 1002 (S201).
After the counter N is initialized to 1 (S202), the colorimetric head 20
03 on the reference white plate 2005 (S203),
Is measured and calibration is performed (S204).

Next, the first matrix arranged on the sample image
Move the colorimetric head 2003 over the leftmost color patch of N rows
(S205), the color patch is measured (S206), and the color measurement data is transmitted to the color measurement module 1002 (S207).

Next, it is determined whether or not the colorimetric head 2003 has reached the right end of the colorimetric range (S208), and if not, the colorimetric head 2003 is moved onto the color patch on the right (S209). Steps S206 to S208 are repeated. Further, when the colorimetric head 2003 has reached the right end of the colorimetric range, it is determined whether the colorimetric head 2003 has reached the lower end of the colorimetric range (S210) .If not, the counter N is incremented. (S211), Step S
Repeat steps S203 to S210. When the colorimetric head 2003 reaches the lower end of the colorimetric range, the colorimetric operation ends.

According to the color measurement procedure shown in FIG. 15, the calibration involving the color measurement of the reference white plate 2005 is performed every time the color measurement of one row of color patches arranged in a matrix is completed. . Therefore, the colorimetric head 2003 is
Efficient calibration can be performed by using a part of the operation of moving to 2005 to the operation of moving the colorimetric head 2003 to the first color patch of the row.

FIG. 16 is a flowchart showing another example of the colorimetry procedure by the colorimeter 1001, which is a process executed by the CPU in the colorimeter 1001. Note that steps that perform the same processing as the steps in FIG. 15 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In step S212, the counter N is initialized to 1, and a flag indicating the moving direction of the colorimetric head 2003 is set.
Initialize F to '1' (move right).

After transmitting the colorimetric data in step S207,
The flag F is determined (S213), and if F = '1', the colorimetric head
It is determined whether or not 2003 has reached the right end of the color measurement range (S208),
If it has not reached, the colorimetric head 2003 is moved onto the color patch on the right (S209), and steps S206 to S208 are repeated.
If the colorimetric head 2003 has reached the right end of the colorimetric range, it is determined whether the colorimetric head 2003 has reached the lower end of the colorimetric range (S210). If not, the flag F is inverted (F210). =
'0'; move to the left) and increment counter N (S
214), move the colorimetric head 2003 over the lower color patch
(S215), the process returns to step S206.

If the flag F = '0' in step S213, it is determined whether or not the colorimetric head 2003 has reached the left end of the colorimetric range (S216). Move to the color patch on the left (S217), and from step S206
Repeat S216. If the colorimetric head 2003 has reached the left end of the colorimetric range, it is determined whether the colorimetric head 2003 has reached the lower end of the colorimetric range (S218).
Is inverted (F = '1') and the counter N is incremented
(S219), the process returns to step S203.

When the lower end of the measurement range has been reached in step S210 or S218, the colorimetry ends.

According to the colorimetry procedure shown in FIG. 16, the calibration involving the colorimetry of the reference white plate 2005 is performed every time the colorimetry of two rows of color patches arranged in a matrix is completed, that is, the colorimetric head. Each time 2003 returns to the left end of the line. Therefore, efficient calibration can be performed by utilizing the operation of the colorimetric head 2003 reciprocating in the color patch rows arranged in a matrix as part of the operation of moving to the reference white plate 2005. Further, compared to the color measurement procedure shown in FIG. 12, the frequency of calibration is halved, so that the color measurement time is reduced. On the other hand, the effect of suppressing the colorimetric error is slightly reduced.

In the above description, the horizontal direction and the vertical direction are described as the X direction and the Y direction shown in FIG. 16. However, the horizontal direction may be the Y direction, and the vertical direction may be the X direction.

[0074]

[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 (or a recording medium) in which program codes of software for realizing the functions of the above-described embodiments are recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. It is needless to say that the present invention can also be achieved by a CPU or an MPU) 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. Also,
When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the operating system (OS) running on the computer based on the instructions of the program code.
It goes without saying that a case where the functions of the above-described embodiments are implemented by performing some or all of the actual processing, and the processing performs the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. Needless to say, 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.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the above-described flowcharts (shown in FIG. X and / or FIG. Y).

[0078]

As described above, according to the present invention,
In colorimetry for providing a profile, efficient calibration can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an image processing apparatus according to a first embodiment;

FIG. 2 is a diagram showing an example of an RGB → Lab conversion table.

FIG. 3 is a diagram showing a correspondence relationship between device RGB values and Lab colorimetric values.
Flowchart showing the procedure for performing device RGB → Lab conversion,

FIG. 4 is a diagram showing an example of a sample image.

FIG. 5 is a diagram illustrating an example of a color measurement result by a color patch color measurement unit.

FIG. 6 is a diagram for explaining selection of sample points;

FIG. 7 is a diagram illustrating a weighting function according to a distance d,

FIG. 8 is a view for explaining a function for changing the number of sample points;

FIG. 9 is a block diagram illustrating a configuration example of an image processing apparatus according to a second embodiment;

FIG. 10 is a block diagram illustrating a configuration example of an image processing apparatus according to a third embodiment;

FIG. 11 is a block diagram illustrating a configuration example of a color conversion module according to a fourth embodiment;

FIG. 12 is a diagram illustrating a procedure for creating a profile of an output device.

FIG. 13 is a diagram for explaining creation of a Lab → device CMYK conversion table;

FIG. 14 is a diagram showing an overview of a colorimeter.

FIG. 15 is a flowchart illustrating an example of a colorimetry procedure using a colorimeter;

FIG. 16 is a flowchart illustrating another example of a color measurement procedure using a colorimeter.

Continued on the front page (72) Inventor Kenichi Naito 3-11-28 Mita, Minato-ku, Tokyo Canon Sales Inc. (72) Inventor Hayato 3-11-28 Mita, Minato-ku, Tokyo Canon Sales Inc. F-term (reference) 5B057 AA11 BA02 BA19 BA23 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE17 CE18 CH07 DA16 DA17 5C077 MM27 MP01 MP08 PP32 PP33 PP36 PP37 PQ12 PQ17 PQ23 RR18 RR19 SS01 SS02 TT02 5B03 HB03B02 H02B03 H02B03 H02 NA13 NA29 PA03

Claims (9)

[Claims] 1. An image processing method comprising: sending color patch data to an output device to output a color patch; causing the color patch to read the color patch; and inputting the read result. And causing the colorimeter to perform calibration using a white plate arranged at a predetermined position in accordance with the arrangement of the color patches. 2. The image processing method according to claim 1, wherein the calibration is performed each time the color patches arranged in a matrix are measured for one row or one column. 3. The image processing method according to claim 1, wherein the calibration is performed every time two rows or two columns of the color patches arranged in a matrix are measured. 4. The image processing method according to claim 1, wherein said calibration involves colorimetry of a reference white plate arranged at a predetermined position. 5. An image processing apparatus for sending color patch data to an output device to output a color patch, reading the color patch by a colorimeter, and inputting the read result, wherein the operation of the colorimeter is performed. Image processing characterized by causing the colorimeter to perform calibration using a white plate arranged at a predetermined position according to the arrangement of the color patches. apparatus. 6. The image processing apparatus according to claim 5, wherein the control unit causes the calibration to be performed each time the color patches arranged in a matrix are measured for one row or one column. 7. The image processing apparatus according to claim 5, wherein the control unit causes the calibration to be performed each time the color patches arranged in a matrix are measured in two rows or two columns. apparatus. 8. The image processing apparatus according to claim 5, wherein the calibration involves color measurement of a reference white plate arranged at a predetermined position. 9. A recording medium storing an image processing program code for sending color patch data to an output device to output a color patch, causing the color patch to read the color patch, and inputting the read result. The program code has at least a code of a step of causing the colorimeter to perform calibration using a white plate arranged at a predetermined position according to the arrangement of the color patches when reading the color patches. A recording medium characterized by the above-mentioned.