JP2003087590A - Method and device for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is difficult to independently adjust a black plate while maintaining color reproduction with high accuracy in a color printer for forming an image with CMYK color materials. SOLUTION: In preparing a conversion condition for converting a signal on a uniform color space into CMYK signals subordinate to a printer, the signal on the uniform color space corresponding to a colorimetric value is once converted into RGB signals, the RGB signals are converted into CMYK signals, and a black quantity adjusting part 2104 adjusts a K value with black quantity adjustment function based on a user instruction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and an image processing apparatus, for example, color reproduction processing of a printer.

[0002]

2. Description of the Related Art In a color reproduction process of a printer or a printing machine, as a method for performing color correction for improving a color reproduction effect, color masking for obtaining a data in an output color space by performing a matrix operation on data in an input color space The method of converting the data of the input color space into the data of the output color space by the method is often used.

[0003]

However, the output characteristics of color printers and printing machines generally exhibit strong non-linearity. Therefore, in 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, the characteristics of a color printer or printing machine are sufficiently approximated in all color gamuts. I couldn't.

In general, color printers are CMYK 4
In many cases, an image is formed with color materials. Images formed by these four color materials often differ in appearance depending on how black (K) is inserted, even if they show the same colorimetric value. Various methods are known for inserting black, but most of the methods require changing conditions depending on the type of image and the gradation characteristics of the printer, and it is not easy to adjust how to insert black. It was difficult.

The present invention has been made to solve the above problems, and provides a profile that accurately approximates the strong non-linear output characteristics of a color printer or printing machine and enables highly accurate color reproduction. The purpose is to

Another object of the present invention is to realize a flexible adjustment of a black plate while maintaining highly accurate color reproduction in a color printer that forms an image with CMYK color materials.

[0007]

As one method for achieving the above object, the image processing method of the present invention has the following steps.

That is, a colorimetric step of inputting a colorimetric value of a color patch output from an output device, and based on the colorimetric value, a signal on a first color space dependent on a target device is independent of the device. A first creating step of creating a first conversion condition for converting into a signal in a second color space, and substituting the signal in the second color space into the output device based on the colorimetric value. And a second creating step of creating a second conversion condition for converting to a signal on the third color space, the second creating step including the signal on the second color space. To a signal on the RGB color space, a second step to convert a signal on the RGB color space to a signal on the third color space, and a second step on the third color space. And a black amount adjusting step of adjusting a black value in the signal. Characterized in that it created the conditions.

An image for creating conversion conditions of a signal on a uniform color space independent of a device and a signal on a CMY color space dependent on the device based on the colorimetric values of color patches output from the device. A processing method, in which a signal in the uniform color space corresponding to the colorimetric value is once converted into a signal in the RGB color space, and the signal in the RGB color space is converted into a CMYK signal in the CMY color space. It is characterized in that the conversion condition is created so that the K value is adjusted.

Further, the colorimetric value of the patch created by the target device is input based on the device-dependent color data represented by a plurality of color component data including the black component,
A first look-up table for converting device-dependent color data represented by a plurality of color component data not containing a black component into device-independent color data is created from the colorimetric value, and the first look-up table is created. An image processing method for creating a second lookup table for converting the device-independent color data into device-dependent color data represented by a plurality of color component data including the black component by referring to a table. The recording material total amount condition for controlling the total amount of recording material and the black amount adjustment condition regarding the method of creating the black component data are input, and the conversion condition is obtained from the recording material total amount condition and the black amount adjustment condition. Device-dependent color data represented by a plurality of color component data not containing a black component is converted to device-dependent color data represented by a plurality of color component data containing the black component. Using a conversion condition for converting to, characterized by creating said first and said second look-up table.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

[0012]

First Embodiment FIG. 1 is a block diagram showing an example of the arrangement of an image processing apparatus according to the embodiment.

The 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, it may be an RGB signal indicating an image read from a document by a scanner, or C that should be output to a printer.
It may be a MYK signal. When this embodiment is applied to a copying machine, the input signal is an RGB signal indicating an image read by a scanner. When the purpose is proof (test printing, proof printing), it is a CMYK signal output to the target printing machine.

Such an input signal is input to the input color → Lab conversion unit 101 and is a device independent color space Lab.
Converted to color space signals. This conversion is input color → Lab
It is realized by LUT conversion using the conversion LUT 102.

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 that depends on the RGB color space of scanner A is input, the three-dimensional input representing the correspondence between the RGB value and the Lab value that are dependent on the RGB color space of scanner A-the three-dimensional output RGB → Lab The conversion table is set as the input color → Lab conversion LUT 102 table. Similarly, printer B CMYK
When an image signal dependent on the color space is input, the four-dimensional input representing the correspondence between the CMYK value and the Lab value dependent on the color space of printer B is input into the CMYK → Lab conversion table of the three-dimensional output Color → Lab It is set as a table of the conversion LUT 102.

FIG. 2 is a diagram showing an example of the RGB → Lab conversion table, showing the correspondence between 8-bit RGB values and Lab values. Lab values with typical RGB values as addresses are stored in the actual table, so input color → Lab conversion unit
101 obtains a Lab value corresponding to the input RGB value by taking out the Lab value in the vicinity of the input RGB value from the table and interpolating the obtained Lab value.

Lab output from the input color → Lab converter 101
The signal is sent to the device R by the Lab → device RGB conversion unit 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, its color gamut is often wider than the color reproduction area of the printer. Therefore, the Lab signal output from the input color → Lab conversion unit 101 is output to the printer in the color space compression conversion unit 103.
Mapping to 107 color gamut (gamut mapping)
After that, the data is input to the Lab → device RGB conversion unit 104. As a specific method of gamut mapping, for example, a method of performing color space compression processing in a uniform color space disclosed in Japanese Patent Laid-Open No. 8-130655 may be used, but other known color space compression methods May be used.

The device RGB color space signal output from the Lab → device RGB conversion unit 104 is converted into a CMYK color space signal dependent on the printer 107 by the device RGB → CMYK conversion unit 106, and then the printer 107 outputs the signal. Sent. There are various methods for RGB → CMYK conversion, and any method may be used. For example, the following conversion formula (1) is used. C = (1.0-R)-KM = (1.0-G)-K ... (1) Y = (1.0-B)-KK = min {(1.0-R), (1.0-G), (1.0- B)} [Lab → Device RGB Conversion] Next, details of the Lab → device RGB conversion unit 104 will be described.

The Lab → device RGB conversion unit 104 converts a signal based on the previously obtained correspondence between the device RGB value and the Lab colorimetric value. FIG. 3 is a flowchart showing a procedure for performing Lab → device RGB conversion by obtaining a correspondence relationship between device RGB value and Lab colorimetric value. Of course, if the correspondence between RGB values and Lab colorimetric values has already been obtained, step 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, convert the generated RGB signal of the sample image to device RGB →
The sample image 109 is obtained by outputting to the printer 107 through the CMYK conversion unit 106.

The sample image generated by the color patch generator 108 is created so as to equally divide the device RGB color space. In the example of FIG. 4, an RGB color space of 8 bits for each RGB is equally divided into 9 × 9 × 9 to obtain 729 patches. Originally, the color space dependent on the printer 107 is the CMYK color space, but the RGB color space is a color space dependent on the printer 107 in the sense that the color space can be converted to the CMYK color space by the conversion rule from the RGB color space. I think.

Step S2 Each color patch of the obtained sample image 109 is color-measured by the color patch colorimetric unit 110, and Lab colorimetric value of each color patch is obtained. The obtained Lab colorimetric value is as shown in Figure 5.
Distributed in Lab color space. By this operation, the RGB values generated by the color patch generation unit 108 and the Lab color measurement values measured by the color patch color measurement unit 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
Do the conversion.

By the way, when the LUT is used, a well-known interpolation operation such as cubic interpolation or tetrahedral interpolation is used. These interpolation calculations require that the grids corresponding to the input side of the LUT be equidistant. The device RGB values in the device RGB → Lab conversion LUT 105 table are evenly arranged, but the Lab colorimetric values are not evenly arranged. Therefore, when inputting Lab value, device RGB → Lab conversion L
The UT105's table does not form a LUT with evenly spaced grids. Therefore, it is not possible to simply perform the interpolation calculation to input the Lab value. Therefore, by following the procedure below, Lab →
Perform device RGB conversion.

Step S3 Lab included in table of 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 order of increasing distance d with respect to the input Lab value (⊚). At this time, the distances are described as follows in ascending order. Here, 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 formula. RGB = (1 / N) × Σ _{i = 1} ^N RGBi × f (di) where f (x) = 1 / (1 + x ⁴ ) The function f (x) has the characteristics shown in Fig. 7. Therefore, in the calculation by the above equation, the RGB value corresponding to the Lab colorimetric value that is closer to the Lab color space is weighted with a larger weight to perform the interpolation operation.

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

Therefore, as shown in FIG. 8, L * of the input Lab value
The above problem can be effectively solved by changing the number of sample points according to the value and performing the interpolation calculation. Of course, even in a region having high brightness, the number of samples used for the interpolation calculation is limited, and color turbidity is less likely to occur. An example of the function N (L *) shown in FIG. 8 is 12 when L * = 0.
8 shows a 1/4 power function that becomes 4 when L * = 100.

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

[0030]

[Second Embodiment] An image processing apparatus according to a second embodiment of the present invention will be described below. In the present embodiment,
About the same configuration as that of the first embodiment, the same reference numerals are given and the detailed description thereof is omitted.

FIG. 9 is a block diagram showing an example of the arrangement of the image processing apparatus according to the second embodiment. The image processing apparatus according to the second embodiment converts the signal of the color space independent of the device into the signal of the color space of the printer 107, as in the case of converting the input signal into the signal of the color space independent of the device. First in terms of LUT
It 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 CMYK signal of the sample image generated by the color patch generator 808 is output to the printer 107, and the sample image 109 is obtained.

Each color patch of the obtained sample image 109 is color-measured by the color patch colorimetry unit 110 to obtain Lab colorimetric value of each color patch. Based on the obtained Lab colorimetric value and the CMYK value generated by the color patch generation unit 808, Lab →
The CMYK conversion LUT creation unit 810 creates a CMYK → Lab conversion LUT. Then, based on the created CMYK → Lab conversion LUT,
Lab → CMYK conversion LUT804 using the same method as in the first embodiment.
To create.

For example, if the Lab value is an 8-bit signal, L *
Values range from 0 to 255 and a * and b * values range from -128 to 127. If each Lab range is divided into 16 steps to form a Lab grid, the Lab → CMYK conversion LUT can be calculated by 17 ³ = 4913 times.
804 tables are completed.

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

[0037]

Third Embodiment An image processing apparatus according to the third embodiment of the present invention will be described below. In the present embodiment,
About the same configuration as that of the first embodiment, the same reference numerals are given and the detailed description thereof is omitted.

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

In FIG. 10, the sRGB → CMYK conversion unit 901
The RGB → CMYK conversion LUT 902 is used to convert an input signal in the sRGB color space into a signal in the CMYK color space dependent on the printer 107. s
The CMYK signal output from the RGB → CMYK converter 901 is the printer
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 then output to the printer 107 so that the sample image 109 is obtained. can get.

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

The processing of the sRGB → CMYK conversion LUT creation unit 908 is
CMYK obtained by applying the device RGB → CMYK conversion processing described in the first embodiment to the RGB values generated by the color patch generation unit 108.
Value and Lab → XYZ → XYZ → sR according to the definition formula for Lab colorimetric value
SRGB → CMYK conversion LUT902 from sRGB value obtained by applying GB conversion
Create a table of. For example, if the sRGB signal is an 8-bit signal, each sRGB range is divided into 16 steps and 17 × 17
If a × 17 sRGB grid is constructed, a table of sRGB → CMYK conversion LUT902 is created by calculating 17 ³ = 4913 times.

According to each of the first to third embodiments described above, there is provided a color conversion method capable of accurately approximating the strong non-linear output characteristics of a color printer or a printing machine to enable highly accurate color reproduction. Can be provided. Therefore, in a device-independent color space, the color space conversion that reflects the characteristics of the printer or printing machine is performed well, so that the printer or printing machine can achieve highly accurate color reproduction for any input color space. It will be possible.

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

[0045]

[Fourth Embodiment] An image processing apparatus according to a fourth embodiment of the present invention will be described below. Since the configuration example of the image processing apparatus in this embodiment is substantially the same as that in the first embodiment,
The same reference numerals are given to the respective components, and detailed description thereof will be omitted.
In the fourth embodiment, the device RGB → CMYK converter 106
An example will be shown in which the conversion method in is replaced with a method different from the first embodiment.

FIG. 11 shows the device RGB → CMYK of the fourth embodiment.
FIG. 6 is a diagram showing a flow of processing in a conversion unit 106. The device RGB values that are input and normalized to [0: 1] are calculated in step S1.
It is inverted in 001 and converted to a CMY signal. After that, in step S1002, gamma conversion is performed using the parameter γ as shown in the following equation. C = ^CγM = ^MγY = ^{Yγ In} the fourth embodiment, the parameter γ in the above equation is set to γ = 1.6.

The gamma-converted CMY signal is processed in step S10.
In 03, an interpolation operation using a grid (lattice point) as described below is performed to convert the CMYK signal.

In the grid 1004 used in the interpolation calculation processing S1003, each CMY has a range of [0: 1].
Located at the top of the cube in CMY space, each grid corresponds to the CMYK value as follows.

[0049] With respect to the input CMY value 1005, a distance from each of the above CMY grid values is calculated, a linear weighting operation is performed on the corresponding CMYK value with a weight corresponding to the distance, and the CMYK value is output.

In general, in the case of an electrophotographic printer, the ideal toner (ink) amount may not be applied due to the transferability and fixing property of the toner, and in the ink jet printer due to the ink permeability. This gives 2
The next color (RGB) may not be output with the toner amount for two colors, or Bk may not be output with the toner amount for three or four colors.

In the fourth embodiment, it is assumed that the printer 107, which is an output target, carries only 1.8 color toners for secondary colors and 2.2 color toners for blacks, and therefore is shown in the above table. CMY values indicating each color of red, green and blue (0,1,1), (1,0,1),
For (1,1,0), the corresponding CMYK values are (0.0,0.
It was set as 9,0.9,0.0), (0.9,0.0,0.9,0.0), (0.9,0.9,0.0,0.0). Also, the corresponding CMYK value of black is (0.4, 0.4, 0.
4, 1.0).

More generally, assuming that the secondary color toner amount is col2 and the Bk toner amount is col4, the corresponding CMYK values of red, green, blue and black are set as follows.

Red = (0, col2 / 2, c
ol2 / 2, 0) Green = (col2 / 2, 0, col2 / 2,
0) Blue = (col2 / 2, col2 / 2, 0,
0) Black = ((col4-1) / 3, (col4-1) / 3, (col4-1) / 3,
1) That is, in the fourth embodiment, col2 = 1.8, col4 =
It was 2.2.

Of course, the above-mentioned corresponding CMYK values and definitions are not limited to this example, and can be arbitrarily set according to the device characteristics or the output purpose. For example, if the corresponding CMYK value for black is (0, 0, 0, 1), then RG
Pure black represented by B = (0,0,0) can be printed with a black toner single color, and 100% UCR can be realized.

Also in the fourth embodiment, similar to step S1 in the first embodiment, the device RGB → CMYK conversion based on the color patch output from the color patch generator 108 is performed, so that the sample image 109 from the printer 107 is obtained. Is output. Then, as in step S2, each color patch of the obtained sample image 109 is color-measured by the color patch colorimetric unit 110, and the Lab colorimetric value of each color patch is obtained. Lab colorimetric values obtained in the fourth embodiment are Lab color values as shown in FIG.
It is distributed in the color space. According to FIG. 12, in the first embodiment shown in FIG. 5, compared with the Lab colorimetric value distribution of the output patch using the device RGB → CMYK conversion according to formula (1), in the region where L * is low, It can be seen that the density of the distribution is thin, and the density is high in the region where L * is high.

Therefore, the device RGB in the fourth embodiment
→ If the color patch output based on CMYK conversion is used, the problem described in the first embodiment, that is, the gradation jump in the device RGB color space due to the sample congestion in the low lightness area, the low lightness area The problem of the white balance collapse and the like can be easily solved without changing the number of sample points as shown in FIG. 8 of the first embodiment.

In order to make the density of the colorimetric value distribution of the color patch independent of the lightness as much as possible, as shown in the fourth embodiment, the gamma conversion parameter (γ value) is set according to the gradation characteristic of the output printer. ) Should be changed appropriately,
It is also effective to use another calculation method such as a polynomial function instead of gamma conversion.

[0058]

[Fifth Embodiment] An image processing apparatus according to a fifth embodiment of the present invention will be described below. In the fifth embodiment, the first
About the same composition as an embodiment, the same numerals are attached and the detailed explanation is omitted.

FIG. 13 is a block diagram showing an example of the arrangement of the image processing apparatus of the fifth embodiment. Also in the fifth embodiment, the second
Similar to the embodiment, the conversion from the device-independent color space signal to the printer 107 color space signal is performed by the LUT. Further, a method of creating the LUT will also be described in detail.

In each of the embodiments described above, the method of creating the profile of the output device has been described. That is,
The device value (for example, CMYK) → Lab conversion LUT and the Lab → device value (for example, CMYK) conversion LUT correspond to the destination profile and the source profile of the output device, respectively.

For the purpose of proof (test printing, proof printing), an image color-converted in accordance with the output characteristics of the target printing machine may be printed by a copying machine or a printer. In order to perform such a proof, the sample image data is supplied to the output device used for the proof and printed by the method described in each of the above-described embodiments, and the colorimetric value of each color patch of the obtained sample image is calculated. You need to create a profile. Then, the image that has been color-converted using the created profile is printed by the output device.

In the fifth embodiment, a profile creating process of an output device used for proof will be described. Needless to say, the profile created in the fifth embodiment is not limited to the proof, but can be used for normal output (printing).

CMYK → Lab converter 1201 shown in FIG. 13, Lab →
CMYK converter 1202, printer 107, CMYK → Lab conversion LUT120
4 and the configuration of Lab → CMYK conversion LUT1205 is a configuration of a general proof system.

The CMYK signal input to the CMYK → Lab converter 1201 is a CMYK signal that depends on the characteristics of the target printing machine, and the CMYK color space and the device independent color space (Lab) that are dependent on the printing machine device. CMYK that holds the correspondence with
→ Lab conversion By CMYK → Lab conversion using LUT1204, it is converted to a signal in Lab color space which is a device independent color space.

The converted Lab signal is processed by the Lab → CMYK converter 12
With 02, the signal is converted into a signal in the CMYK color space using the Lab → CMYK conversion LUT 1205 that holds the correspondence relationship between the CMYK color space subordinate to the printer 107 and the Lab color space, and is output from the printer 107.

As described above, CMYK → L in the fifth embodiment
For both ab conversion and Lab → CMYK conversion, the LUT is read and the LU
It is executed by addressing T with an input signal and performing an interpolation operation.

Such a color matching method is performed at the time of color matching using CRD in PostScript or color matching using an ICC profile. In particular, the ICC profile enables CMYK → Lab conversion LUTs, and
Equipped with Lab → CMYK conversion LUT.

The Lab → CMYK conversion LUT 1205 and the CMYK → Lab conversion LUT 1204 are C output from the color patch generation unit 1206.
The MYK color patch is output from the printer 107, and the obtained sample image 109 is based on the colorimetric values measured by the color patch colorimetry unit 110, and the Lab → CMYK conversion LUT creation unit 1211 and CMYK → Lab
It is created in the conversion LUT creation unit 1212.

Here, in the Lab → CMYK conversion LUT creation unit 1211, similar to the processing in the Lab → device RGB conversion unit 104 and device RGB → CMYK conversion unit 106 of the first embodiment, Lab colorimetric values of sample images To CMYK to create Lab → CMYK conversion LUT1205. However, since the Lab → CMYK conversion in the first embodiment is calculated based on the colorimetric values of the RGB color patches,
The colorimetric values of the CMYK color patches in the fifth embodiment cannot be applied as they are. Therefore, in the fifth embodiment, a device RGB → Lab conversion LUT creation unit 1209 is provided in order to artificially create a colorimetric value table of RGB color patches.

On the other hand, in the CMYK → Lab conversion LUT creating unit 1212, the CMYK → Lab conversion LUT 1204 is created by the interpolation calculation using the colorimetric value table of the CMYK color patch.

The created LUT is stored in the storage unit 1213, and L
Lab → CMYK conversion LUT 1205 referenced by ab → CMYK conversion unit 1202
CMYK to be set as or referenced in the CMYK → Lab converter 1201 for the proof system for other printing machines.
→ Set and used as Lab conversion LUT 1204. Figure 13
Details of the operation in each processing unit shown in will be described later.

FIG. 14 is a diagram showing a configuration example when the image processing apparatus of the fifth embodiment is realized on a computer system.
It has a very general computer system configuration. Each processing unit (1201, 1202, 1206, 1209, 1211, 1212) shown in FIG.
It is realized as a module of a program arranged in AM1303 or ROM1304, and is read and executed by CPU1302. In addition, each LUT (1204, 1205) shown in FIG.
It is realized as an area reserved on M1303. The printer 1312 functions as the printer 107 of FIG. 13 by being controlled by the printer driver executed by the CPU 1302 via the printer I / F 1311. As the printer 107, another printer existing on the network 1306 via the network I / F 1305 may be used.

The color patch colorimetry unit 110 shown in FIG.
This is realized by a color colorimeter 1310 controlled via / F1309, and the HDD 1308 is used as the storage unit 1213. Monitor 1
The 314 is controlled via the video I / F 1313, and is used for a GUI for controlling each module, a color patch display, and the like. The keyboard 1301 and mouse 1307 are used for user input and the like via the GUI.

The operation of each processing unit shown in FIG. 13 will be described in detail below with reference to FIGS. 15A and 15B.

FIG. 15A is a diagram for explaining the detailed operation of the patch generation / colorimetry system and CMYK → Lab conversion LUT creation unit 1212 in the fifth embodiment.

In the figure, the sample image 109 obtained by outputting the CMYK image generated by the color patch generation unit 1206 to the printer 107 is color-measured by the color patch color measurement unit 110, and the CMYK → Lab color measurement value is obtained. The correspondence table 1401 is obtained.

The color patch generator 1206 generates a color patch image having the following CMYK values, for example.

[0078] Here, it is assumed that each of C, M, and Y has a value of 32 and K has a value of 51, and a color patch having 9x9x9x5 color values is generated. Of course, CMYK values are not limited to this. A combination of these CMYK values and the colorimetric values (total 9x9x9x5) of the patches corresponding to the CMYK values becomes a CMYK → Lab colorimetric value correspondence table 1401.

Next, the operation of the CMYK → Lab conversion LUT generator 1212 will be described in detail. The CMYK → Lab conversion LUT creation unit 1212 includes a CMYK grid generation unit 1402 and a CMYK → Lab conversion unit 1
The CMYK → Lab conversion LUT 1204, which is composed of 403 and refers to the CMYK → Lab colorimetric value correspondence table 1401 created as described above.
To create.

In the CMYK grid generation section 1402, the combination of CMYK values generated in the color patch generation section 1206 is
Generate the number of grids specified by the user. For example, 9x9x9x9 CMYK with C, M, Y, K in 32 steps.
Generate a value. The CMYK value generated in this way is CMYK →
The Lab value is converted into a Lab value by an interpolation calculation using the CMYK → Lab colorimetric value correspondence table 1401 which is input to the Lab conversion unit 1403 and obtained by patch generation / colorimetry. The converted Lab value is
It is stored as a CMYK → Lab conversion LUT 1204 along with information on the CMYK values generated by the CMYK grid generation unit 1402.

FIG. 15B shows the device RG in the fifth embodiment.
B → Lab conversion LUT creation unit 1209 and Lab → CMYK conversion LUT creation unit 1
It is a figure for demonstrating the detailed operation of 211.

In the figure, device RGB → Lab conversion LUT
The creation unit 1209 converts the RGB values generated by the device RGB grid generation unit 1410 into CMYK values by the device RGB → CMYK conversion unit 1411, and then, by the CMYK → Lab conversion unit 1412, the patch generation / measurement illustrated in FIG. 15A. The device RGB → Lab conversion LUT 1413 is obtained by referring to the CMYK → Lab colorimetric value correspondence table 1401 obtained by the color and converting to the Lab value. CMYK
→ As the Lab conversion unit 1412, the CMYK → Lab conversion LUT creation unit 121
The module used in 2 may share the CMYK → Lab conversion unit 1403.

For example, the device RGB grid generator 1410
RGB grid value Then, the Lab value for these grid values can be calculated. In other words, Lab values equivalent to those obtained when RGB color patches are generated and colorimetric measurements are obtained.

Next, the operation of the Lab → CMYK conversion LUT creation unit 1211 will be described in detail. The Lab → CMYK conversion LUT creation unit 1211 includes a Lab grid generation unit 1420 and a color space compression conversion unit 1.
421, Lab → device RGB converter 1422, and device RGB
→ consists of CMYK converter 1423, device RGB → Lab conversion LUT
Device RGB → Lab conversion LU created by the creation unit 1209
Create Lab → CMYK conversion LUT1205 by referring to T1413.
As the device RGB → CMYK conversion unit 1423, the device RGB → CMYK conversion unit 1411 that is a module used in the device RGB → Lab conversion LUT creation unit 1209 may be shared.

The Lab grid generator 1420 generates Lab grid values with the number of grids designated by the user.
For example, if the Lab value is treated as an 8-bit signal, the user
If you specify a grid number of 17x17x17, you can use L * from 0 to 2
Up to 55, -128 to 127 of a * and b * are taken in 16-step increments, and 4913 (= 17x17x17) Lab grid values are generated. The Lab value generated in this way is a color space compression conversion unit 1421 that can share the color space compression conversion unit 103 of the first embodiment, Lab → device RGB conversion unit 1422, device RGB → CMYK conversion unit 106 of the first embodiment. Device RGB that can share
→ Converted into CMYK values by the CMYK converter 1411. The converted CMYK value is the Lab generated by the Lab grid generator 1420.
It is stored as a Lab → CMYK conversion LUT 1205 together with grid information.

FIG. 16 is a diagram showing an example of a user interface (UI) for controlling the processing of the fifth embodiment,
On the computer system shown in FIG. 14, the video I / F1313
Displayed on the monitor 1314 via.

The GUI 1500 shown in the figure has a view 1501 for displaying the patch image output by the color patch generator 1206. The view 1501 is used to confirm whether or not the patch generation in the color patch generation unit 1206 is normal. Buttons 1502-1505 are for patch output,
Color measurement, CMYK → Lab conversion LUT creation, and Lab → CMYK conversion LUT
This is a creation instruction button, and gives an instruction to start each process.

When creating the LUT, the number of grids of the CMYK → Lab conversion LUT can be set in the grid number setting box 1507 in the CMYK → Lab conversion LUT setting field 1506. This is, for example, 9x9x9x9 or 17x17x1 as a pull-down menu
You should be able to select the number of grids such as 7x17.

In the Lab → CMYK conversion LUT setting field 1508, the number of grids can be set in the number of grids setting box 1509, and in addition, the device characteristics of the output printer can be set. Device characteristic individual settings field 1510
In, the secondary color toner amount, the black toner amount, and the gradation correction gamma can be set numerically, and these numerical values are set as the parameters col2, col4, and γ described in the fourth embodiment, and the device RGB → CMYK conversion is performed. It is used as a parameter at the time of conversion in the part 1411 (1423). These individual setting values can be saved with the device characteristic save button 1513, and the saved setting values can be saved with the device characteristic read button 1514.
By pressing, it can be read and used again.

To obtain the recommended value of the device characteristic, the device type may be designated in the device recommended value setting field 1511. In other words, for multiple selectable devices, the device name and 2
Next color toner amount, black toner amount, gradation correction gamma are stored in advance, and if the user specifies the device name,
Corresponding appropriate secondary color toner amount, black toner amount, gradation correction gamma are automatically set. The set value may be displayed in each setting field of the individual setting field 1510.

The individual setting and device recommended value setting are
It can be specified exclusively by the check button. For example, when one is designated, the other is grayed out so that the selection state can be easily grasped.

17A to 17E, each operation is instructed by pressing the patch output button 1502, the color measurement button 1503, the CMYK → Lab conversion LUT creation button 1504, and the Lab → CMYK conversion LUT creation button 1505 on the GUI 1500. It is a flowchart which shows the process in case of.

FIG. 17A is a flowchart of the patch output process shown in FIG. 15A, which is started by pressing the patch output button 1502. That is, the processing is executed by the color patch generation unit 1206 and the printer 107. First, in step S1601, a memory area for storing the CMYK → Lab colorimetric value correspondence table 1401 is secured, and then in step S1602.
Generate a CMYK value that indicates a color patch in step S1603
Then, the CMYK value is stored in the CMYK → Lab colorimetric value correspondence table 1401. Next, in step S1604, the printer 107 to be output is selected in the device recommended value setting field 1511, and the CMYK value of the color patch is output to the selected printer 107 in step S1605. The image 109 is output.

When the sample image 109 is obtained, the colorimetric button 1503 is then pressed to start the colorimetric processing of the sample image 109 shown in FIG. 15A. FIG. 17B is a flowchart showing the colorimetric processing, which is executed by the color patch colorimetric unit 110. The sample image 109 output from the printer 107 is set in the color patch color measuring unit 110 (color color measuring device 1310), and then the color measuring button 1503 is pressed. Then, in step S1611, the colorimeter 1
A command for instructing the start of color measurement to 310 is sent via the serial I / F 1309, and the color measurement value is received from the color colorimeter 1310 in step S1612. Then, in step S1613, the CMYK → Lab colorimetric value correspondence table 1401 is completed by storing the colorimetric values in the CMYK → Lab colorimetric value correspondence table 1401.

Next, the process of creating each LUT will be described.

FIG. 17C shows a CMYK → Lab conversion LUT creation button 150.
CMYK → Lab shown in Figure 15A, initiated by pressing 4
It is a flowchart of a conversion LUT creation process. That process is executed by the CMYK → Lab conversion LUT creation unit 1212.

First, in step S1621, the number of grids set in the grid number setting box 1507 is checked, and in step S1622, a memory area for storing the CMYK → Lab conversion LUT 1204 is secured according to the number of grids.
Then, in step S1623, CMYK grid values corresponding to the number of grids are generated, and in step S1624, the CMYK grid values are
Convert to a value, and convert the Lab value from CMYK to Lab in step S1625 L
The LUT is completed by storing in the UT1204.

17D and 17E are L shown in FIG. 15B, which is started by pressing the Lab → CMYK conversion LUT creation button 1505.
It is a flow chart of ab-> CMYK conversion LUT creation processing. The processing is performed by the device RGB → Lab conversion LUT creation unit 120.
9 and Lab → CMYK conversion LUT creation unit 1211.

First, in step S1701, Lab → CMYK conversion LUT
Each setting value in the setting field 1508 (number of grids,
Acquire and store the secondary color toner amount, Black toner amount, gradation correction gamma value). Next, in step S1702, the process of creating the device RGB → Lab conversion LUT 1413 is started.

Details of the device RGB → Lab conversion LUT creation will be described with reference to FIG. 17E. First, step S1710
Then, a memory area for storing the device RGB → Lab conversion LUT 1413 is secured. Then, in step S1711, the device R
Generate a grid value of GB and convert device RGB to Lab LUT 141
3 in addition to the device RGB in step S1712 → C
The Lab value obtained by the MYK conversion and the CMYK → Lab conversion in step S1713 is stored in the device RGB → Lab conversion LUT 1413 in step S1714, thereby completing the LUT.

Device RGB → Lab conversion LUT in step S1702
When 1413 is obtained, in step S1703, a memory area for storing the Lab → CMYK conversion LUT 1205 is secured according to the number of grids set in the grid number setting box 1509. Then, in step S1704, a Lab grid value corresponding to the number of grids is generated. The Lab grid value is
Color space compression in step S1705, Lab → device RGB conversion in step S1706, device RGB → CMYK conversion processing in step S1707 is converted to CMYK values, and in step S1708 Lab →
The LUT is completed by being stored in the CMYK conversion LUT 1205.

As described above, according to the fifth embodiment, it is possible to appropriately create the profile of the output device, and thus it is possible to perform an appropriate proof process.

[0103]

[Sixth Embodiment] An image processing apparatus according to a sixth embodiment of the present invention will be described below.

As described in the first embodiment, L
In ab → device RGB conversion, it is desirable that the density of the colorimetric value distribution of the RGB patch be as uniform as possible regardless of the brightness. Therefore, in the first embodiment, the number of samples of Lab values used for calculation is increased in the low lightness region where the colorimetric value distribution is dense, and the number of samples is reduced in the high lightness region where the colorimetric value distribution is sparse. An example was given.

In order to achieve the same purpose, the parameter γ in the device RGB → CMYK conversion described in the fourth and fifth embodiments may be adjusted to an appropriate value.
As described above, as a result of the adjustment, the colorimetric value distribution in which the distribution is concentrated in the low lightness region as shown in FIG. 5 is obtained as the distribution not depending on the lightness as shown in FIG.

In the above-described fifth embodiment, the example in which the user sets the parameter γ via the GUI has been described.
The embodiment is characterized in that the parameter γ is automatically set.

FIG. 18 is a block diagram showing the arrangement of an image processing apparatus according to the sixth embodiment. In addition to the arrangement of the fifth embodiment shown in FIG. 13, Lab colorimetric values for CMYK color patches are analyzed. A colorimetric value distribution analysis unit 1901 for automatically setting the parameter γ is provided. Since the other configurations are the same as those in the fifth embodiment, the same reference numerals are given and detailed description will be omitted.

FIG. 19 is a block diagram showing the detailed arrangement of the colorimetric value distribution analysis unit 1901. In the figure, a gray value generation unit 1910 generates a plurality of R = G = B gray values and passes them to the device RGB → CMYK conversion unit 1911. The CMYK values converted here are converted into Lab values based on the CMYK → Lab colorimetric value correspondence table 1401 (FIG. 15A) generated by the color patch colorimetry unit 110 in the CMYK → Lab conversion unit 1912. Gray value → L * table 1913 is constructed. The γ value calculation unit 1914 calculates an appropriate γ value as described later based on the Gray value → L * table 1913. The obtained γ value is given to the device RGB → Lab conversion LUT creation unit 1209 and Lab → CMYK conversion LUT creation unit 1211, and the device RGB → CMYK conversion units 1411 and 14
Set as 23 parameters.

As the device RGB → CMYK conversion unit 1911, the device RGB → CMYK conversion unit 1411 shown in FIG. 15B as a module in the device RGB → Lab conversion LUT creation unit 1209 in the fifth embodiment is shared. Is also good. Similarly, as the CMYK → Lab converter 1912, the CMYK shown in FIG. 15A is used.
→ Lab conversion LUT creation unit 1212 module CMYK → La
The b converter 1403 may be shared.

Lab → CMYK conversion in the sixth embodiment.
The LUT creation process (FIG. 15B) will be described. The processing is performed by the device RGB → Lab conversion LUT creation unit 1209 and Lab → CM.
It is executed in the YK conversion LUT creation unit 1211 and its outline is
It is similar to FIG. 17D described in the embodiment. In the sixth embodiment, the device RGB → L shown in step S1702 of FIG. 17D.
The ab conversion LUT creation process is different from that of the fifth embodiment, and details thereof are shown in the flowchart of FIG.

As shown in FIG. 20, in the sixth embodiment, step S1 is performed immediately after the Lab → CMYK conversion LUT creation process is started.
The colorimetric value is analyzed in 801 to determine the γ value, and the subsequent processing is the same as in FIG. 17E.

Hereinafter, a method of calculating the γ value in the colorimetric value distribution analysis unit 1901 will be specifically described with reference to the flowchart of FIG.

Step S21 The gray value generation section 1910 generates a gray signal and obtains the L * value for the gray signal.

For example, first, in the gray value generation unit 1910, R = G = B =
A plurality of gray signals such as 0, 16, 32, ..., 255 are generated, and the device RGB → CMYK converter 1911 converts the gray signals into CMYK values. At this time, γ = 1.0 is set as the parameter in the device RGB → CMYK conversion unit 1911, and col2 and col4 are the first
5 The value is specified by the GUI of the embodiment.

Next, the converted CMYK value is converted into a Lab value by the CMYK → Lab conversion unit 1912. This gives the Lab value for the gray signal. 22 is a graph in which the gray signal is normalized to [0: 1] and the corresponding L * values are plotted,
This is the gray value → L * table 1913.

Step S22 Correspondence between the gray signal and the L * value shown in FIG. 22 (gray value →
L * Table 1913) is approximated by an exponential function.

First, let L * be L * '= (L * -L * min) / (L * max-L * min)
And normalize to [0: 1]. And normalized gray-
The γ value is obtained by approximating the L * ′ curve by an exponential function by a known function fitting method.

By setting the γ value obtained as described above as a parameter of the device RGB → CMYK conversion units 1411 and 1423, the device RGB → Lab conversion LUT creation unit 1
Device RGB → Lab conversion LUT 1412 obtained by 209, and
Lab → CMYK conversion Lab → CMYK obtained by LUT creation unit 1211
In the conversion LUT 1205, the distribution of the Lab value becomes uniform with respect to the L * value.

Also, when the gradation characteristic is corrected by a polynomial instead of the γ conversion, the same effect can be obtained by performing an operation so that the obtained gray signal-L * curve is fitted to the polynomial.

As described above, according to the sixth embodiment, it is possible to automatically set the parameter γ used in device RGB → CMYK conversion to an appropriate value.

[0121]

[Seventh Embodiment] An image processing apparatus according to a seventh embodiment of the present invention will be described below.

Generally, when forming an image by CMYK,
It is important to control the Bk color ratio, that is, the amount of black ink. As a typical method of controlling the amount of black ink, the amount of black (Bk) ink (or toner) is decreased in the low density region, and the amount of Bk is increased toward the high density region. As a result, it is possible to maintain the vividness of the color in the low-density area and obtain a tighter image in the high-density area.

On the other hand, the control parameters for the device RGB → CMYK conversion described in each of the above-described embodiments are 8 points of R, G, B, C, M, Y, W and Bk which are interpolation grid points in the CMY space. Toner amount and C that is input to CMY space for interpolation calculation,
It was only the γ parameter in the γ transformation of M, Y values.
At this time, since the output CMYK value is calculated by the linear interpolation calculation in the CMY space, the output CMYK value for the input CMY value is calculated.
As a value, each color component changed linearly all at once, and it was impossible to control only the Bk color component independently.

Therefore, in the seventh embodiment, as a modified example of each of the above-described embodiments, the device RGB → CMYK conversion processing shown in each of the above-described embodiments (for example, RGB → C in FIG. 15B is performed).
In the case of the MYK conversion units 1411, 1423), the Bk color component can be independently controlled.

Except for the processing described below, the same processing as that of each of the above-described embodiments is performed.

FIG. 23 shows the device RGB in the seventh embodiment.
→ It is a block diagram which shows the detailed structure of a CMYK conversion part. In the figure, the input RGB values are first inverted and converted by the CMY conversion unit 2101, such as C = 1.0-RM = 1.0-G Y = 1.0-B. Then, in the γ conversion unit 2102, gamma conversion as shown in the following equation is performed using an arbitrary γ value or a γ value 2111 automatically set in the sixth embodiment. C '= C ^γ M' = M ^γ Y '= Y ^γ, and for the C'M'Y' signal in the interpolation calculation unit 2103, as in the fourth embodiment described above, eight grid points in the CMY space. The CMYK value is calculated by performing an interpolation calculation using the value 2112 set from the toner amount limit that defines

Next, the black amount adjusting unit 2104, which is a feature of the seventh embodiment, performs black amount adjustment using the black amount adjusting function 2113 on the calculated CMYK values. Hereinafter, the black amount adjustment processing in the seventh embodiment will be described in detail.

FIG. 24 shows an example of the black amount adjusting function 2113.
In the figure, the horizontal axis is the Bk value before conversion, and the vertical axis is the B value after conversion.
k'value. The black amount adjustment function 2113 shown in the figure is, in other words, a cubed power function with Bk ′ = Bk ³ .

If the conversion by this function is performed on Bk,
In the low concentration region where the Bk amount is small, the Bk entry amount is controlled to be smaller, and the Bk entry amount is steeply increased toward the high concentration region. Further, in order to more flexibly control the way of entering Bk, by holding a plurality of black amount adjustment functions 2113 in the LUT format, in addition to the above power function, a non-analytical function or a free-form curve can be selected. It is also effective to set it as possible.

The black amount adjusting process in the black amount adjusting unit 2104 will be specifically described below with reference to the flowchart of FIG.

Step S31 First, the black amount adjustment function 2113 is used to perform Bk adjustment for converting the Bk value of CMYK calculated by the interpolation calculation into Bk ′. That is, assuming that the black amount adjustment function 2113 is F (x), the following calculation is performed. Bk_new = F (Bk) -Step S32 Next, the Bk amount reduced in the upper step S31 is distributed to other CMY values and added to maintain the total toner amount obtained by the interpolation calculation. The addition method is shown below. C_new = C + (Bk_new-Bk) × C / (C + M + Y) M_new = M + (Bk_new-Bk) × M / (C + M + Y) Y_new = Y + (Bk_new-Bk) × Y / (C + M + Y) The distribution of the reduced Bk amount to C, M, Y is not limited to the distribution according to the amount of C, M, Y as in the above formula, but in some cases As shown in, it is also effective to perform addition divided equally for each color. C_new = C + (Bk_new-Bk) / 3 M_new = M + (Bk_new-Bk) / 3 Y_new = Y + (Bk_new-Bk) / 3 ● Step S33 C_new, M_new, Y_ne obtained in steps S31 and S32
Output w and Bk_new as CMYK 'after black amount adjustment.

As described above, in the seventh embodiment, from the gradation gamma, the total toner amount (recording material total amount condition), and the black amount adjustment condition, the device-dependent color indicated by a plurality of color component data that does not include the black component. Create a conversion condition (RGB → CMYK conversion process) that converts data (device-dependent RGB) to device-dependent color data (CMYK) indicated by multiple color component data including black components, and then convert the device RGB → Lab conversion LUT. And Lab →
Create a CMYK conversion LUT.

Therefore, not only the gradation gamma and the total toner amount but also the black amount can be arbitrarily adjusted.

The black amount adjustment is performed by the steps described above. Each of these modules is realized as a program operating on a computer system as shown in FIG. 14 as in the fifth embodiment, and is shown in FIG. 13, for example. It operates in cooperation with each module corresponding to each processing unit.

FIG. 26 is a diagram showing an example of a user interface (UI) according to the program of the seventh embodiment.
In the fifth embodiment, UI components for controlling the black amount adjustment processing are added to the GUI screen shown in FIG.
The UI shown in FIG. 26 will be described below.

In FIG. 26, the same items as those in FIG. 16 are designated by the same reference numerals and the description thereof will be omitted. 26 is characterized in that a black plate characteristic setting field 2301 is added to the GUI example of FIG. Based on the setting from this field 2301, the function form of the black amount adjustment function 2113 for adjusting the way of entering Bk in the seventh embodiment is set.

In the black plate characteristic setting field 2301,
The “gamma setting” button 2302 is for setting the γ value in the function of Bk ′ = Bk ^γ , and the numerical value set in the numerical field is set as the γ value, and the black amount adjusting unit 2104 sets the black amount. Used as adjustment function 2113.

In addition, in this GUI example, "freely set" is added.
A button 2303 is provided, and when this is selected, a black amount adjustment curve panel 2304 is displayed. In this panel 2304, the function form of the black amount adjusting function 2113 can be arbitrarily set as a free curve 2305. For example, as shown in the same figure, the user drags two predetermined marks on the graph showing the function to arbitrary positions, and connects the origin and the upper right point of the graph with the marks by a predetermined method (spline function etc.), The free curve 2305 is set.

After the user arbitrarily sets the curve 2305 and presses the OK button on the panel 2304, the set curve is set as the black amount adjustment function 2113. In this way, when an arbitrary curve is set as the black amount adjustment function 2113, the black amount adjustment calculation in step S31 is performed by the LUT.

The “gamma setting” 2302 and the “free setting” 2303 can be exclusively specified by the check button. For example, when one is designated, the other is grayed out so that the selection state can be easily grasped.

The device recommended value setting field 1511
Depending on the device type set in, the black amount adjustment function 21
The recommended value of 13 may be set.

As described above, according to the seventh embodiment, black amount adjustment can be performed while maintaining the set total toner amount. Therefore, more flexible color separation can be performed, and the profile of the output device can be created more appropriately.

[0143]

[Other Embodiments] Although the above embodiment has been described using a CMYK printer, other recording materials (for example, CMYK ink, light
6 color inks having C and light M) may be used.

Further, in each of the above embodiments, the RGB → CMYK conversion process is used for explanation, but CMY instead of device RGB is used.
It is also possible to use three color components that do not include a black component such as.
This is RGB and CM in the processing performed by the CMY conversion unit 2101.
From the relational expression of Y, it is clear that CMY can be used instead of RGB.

The device-independent color data is not limited to Lab and may be other color data such as Luv and XYZ.

Even if the present invention is applied to a system composed of a plurality of devices (eg, host computer, interface device, reader, printer, etc.), a device composed of one device (eg, copier, facsimile). Device).

Further, an object of the present invention is to supply a storage medium (or recording medium) recording a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and to supply a computer of the system or apparatus ( Needless to say, this can also be achieved by the CPU or MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Also,
By executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instructions of the program code.
Needless to say, this also includes the case where the above-mentioned processes perform part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written in the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, based on the instruction of the program code. Needless to say, this also includes a case where a CPU or the like included in the function expansion card or the function expansion unit performs a part or all of the actual processing and the processing realizes the functions of the above-described embodiments.

[0149]

As described above, according to the present invention, it is possible to provide a profile that accurately approximates the strong non-linear output characteristics of a color printer or printing machine and enables highly accurate color reproduction. .

Further, in the color printer which forms an image using the K color material, the black plate can be flexibly adjusted while maintaining highly accurate color reproduction.

Therefore, since the color space conversion that well reflects the printer characteristics can be performed in the device independent color space, the printer color can be reproduced with high precision in any input color space. Further, since color separation suitable for the characteristics of the output device can be easily performed, it is possible to further improve the accuracy of color space conversion in the device independent color space.

[Brief description of drawings]

FIG. 1 is a block diagram showing 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,

[Figure 3] Obtaining the correspondence between device RGB values and Lab colorimetric values,
Flow chart showing the procedure to perform device RGB → Lab conversion,

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

FIG. 5 is a diagram showing 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 diagram illustrating a function that changes the number of sample points;

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

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

FIG. 11 is a diagram showing a processing flow of device RGB → CMYK conversion of the fourth embodiment;

FIG. 12 is a diagram showing an example of a color patch color measurement result in the fourth embodiment;

FIG. 13 is a block diagram showing a configuration example of an image processing apparatus according to a fifth embodiment,

FIG. 14 is a diagram showing a configuration example when realizing the fifth embodiment on a computer system;

FIG. 15A is a diagram illustrating a patch generation / colorimetry system and CMY according to the fifth embodiment.
Diagram showing the detailed operation of K → Lab conversion LUT creation,

FIG. 15B is a diagram showing a detailed operation of device RGB → Lab conversion LUT creation and Lab → CMYK conversion LUT creation according to the fifth embodiment;

FIG. 16 is a diagram showing an example of a GUI of the fifth embodiment,

FIG. 17A is a flowchart showing patch output processing of the fifth embodiment,

FIG. 17B is a flowchart showing color measurement processing of the fifth embodiment,

FIG. 17C is a flowchart showing a CMYK → Lab conversion LUT creation process of the fifth embodiment,

FIG. 17D is a flowchart showing Lab → CMYK conversion LUT creation processing of the fifth embodiment;

FIG. 17E is a flowchart showing device RGB → Lab conversion LUT creation processing of the fifth embodiment,

FIG. 18 is a block diagram showing the arrangement of an image processing apparatus according to the sixth embodiment.

FIG. 19 is a block diagram showing the detailed arrangement of a colorimetric value distribution analysis unit according to the sixth embodiment;

FIG. 20 is a flowchart showing device RGB → Lab conversion LUT creation processing in the Lab → CMYK conversion LUT creation processing of the sixth embodiment;

FIG. 21 is a flowchart showing a gamma value calculation method by colorimetric value distribution analysis according to the sixth embodiment;

FIG. 22 is a graph showing the relationship between the gray signal and the L * value,

FIG. 23 is a block diagram showing a detailed configuration of a device RGB → CMYK conversion unit in a seventh embodiment.

FIG. 24 is a diagram showing an example of a black amount adjustment function in the seventh embodiment;

FIG. 25 is a flowchart showing black amount adjustment processing in the seventh embodiment.

FIG. 26 is a diagram showing an example of a GUI of the seventh embodiment.

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Claims (25)

[Claims] 1. An input step of inputting colorimetric values of a color patch output from an output device, and a device-independent first color space-dependent signal based on the colorimetric values in the first color space. First to create a first conversion condition for converting to a signal on the second color space
And a second conversion condition for converting a signal on the second color space into a signal on a third color space dependent on the output device based on the colorimetric value. 2 creation process,
The second creating step includes a first step of converting a signal on the second color space into a signal on an RGB color space, and a signal on the RGB color space by the third color. Creating the second conversion condition by including a second step of converting into a signal on space and a black amount adjusting step of adjusting a black value in the signal on the third color space. An image processing method characterized by: 2. The third color space is a CMY color space, and in the black amount adjusting step, the CMY color space is the CMY color space.
The image processing method according to claim 1, wherein the characteristic of the K value of the K signal is adjusted independently. 3. In the black amount adjusting step, the K value is adjusted based on a predetermined black amount adjusting function, and the K value before and after the adjustment is adjusted.
The image processing method according to claim 2, wherein the difference between the values is distributed to each CMY color value. 4. The image processing method according to claim 3, wherein the black amount adjusting function is a power function of a K value. 5. The image processing method according to claim 4, wherein in the black amount adjusting step, the K value is adjusted using a LUT based on the black amount adjusting function. 6. The image processing method according to claim 3, further comprising a setting step of setting the black amount adjustment function. 7. The second step converts the signal in the RGB color space into a signal in the CMY color space by inverting the signal, performs gamma conversion on the signal in the CMY color space, and performs the gamma conversion. 3. The image processing method according to claim 2, wherein an interpolation calculation is performed on the signal of. 8. The image processing method according to claim 7, wherein the interpolation calculation is a calculation based on a CMYK signal value corresponding to a predetermined grid in the CMY color space. 9. The predetermined grid is an eight-point grid corresponding to each color of R, G, B, C, M, Y, W, and Bk on a CMY color space. The described image processing method. 10. The image processing method according to claim 8, wherein the CMYK signal value corresponding to the predetermined grid is set in consideration of a toner amount according to the characteristics of the output device. . 11. The image processing method according to claim 10, further comprising setting a gamma value in the gamma conversion and the toner amount in the setting step. 12. The method according to claim 7, further comprising an analysis step of analyzing a distribution of the colorimetric values on the second color space and determining a gamma value in the gamma conversion based on the analysis result. The described image processing method. 13. The image processing method according to claim 1, wherein the first and second conversion conditions are lookup tables for color conversion. 14. An image for creating conversion conditions between a signal on a uniform color space independent of a device and a signal on a CMY color space dependent on the device based on colorimetric values of color patches output from the device. A processing method, wherein a signal in the uniform color space corresponding to the colorimetric value is once converted into a signal in the RGB color space, and the signal in the RGB color space is converted into a CMYK signal in the CMY color space. An image processing method, characterized in that the conversion condition is created so as to adjust the K value. 15. The image processing method according to claim 14, wherein the adjustment of the K value is performed by a black amount adjustment function set based on a user instruction. 16. A colorimetric value of a patch created by a target device is input based on device-dependent color data represented by a plurality of color component data including a black component, and a black component is included from the colorimetric value. Creating a first lookup table for converting device-dependent color data represented by a plurality of color component data into device-independent color data, and referring to the first lookup table, the device-independent Is an image processing method for creating a second look-up table for converting the color data of the above into the device-dependent color data indicated by the plurality of color component data including the black component, and controlling the total amount of recording material. The total amount of recording material and the black amount adjustment condition relating to the method of creating the black component data are input, and the change amount obtained from the total amount of recording material condition and the black amount adjustment condition is input. A conversion condition for converting device-dependent color data represented by a plurality of color component data not including the black component into device-dependent color data represented by a plurality of color component data including the black component. An image processing method, characterized in that the first and second lookup tables are created. 17. The image processing method according to claim 16, wherein the total recording material amount condition includes a total amount for each of the black recording material amount and the secondary color recording material amount. 18. The image processing method according to claim 16, wherein the black level adjusting condition allows a user to arbitrarily set a conversion curve. 19. The image processing method according to claim 16, further comprising inputting a gradation correction gamma condition and obtaining the conversion condition using the gradation correction gamma condition. 20. A third lookup table for converting device-dependent color data represented by a plurality of color component data including the black component into the device-independent color data from the colorimetric value. 2. Creating and storing the third look-up table and the second look-up table.
6. The image processing method according to item 6. 21. A program which, when executed by a computer, causes the computer to operate so as to realize the image processing method according to any one of claims 1 to 15. 22. A recording medium on which the program according to claim 21 is recorded. 23. A means for inputting a colorimetric value of a patch created by a target device based on device-dependent color data represented by a plurality of color component data including a black component, and a black component from the colorimetric value. Means for creating a first look-up table for converting device-dependent color data represented by a plurality of color component data that does not include device-independent color data, and referring to the first look-up table, Means for creating a second look-up table for converting the device-independent color data into device-dependent color data represented by a plurality of color component data including the black component, and controlling the total amount of recording material. A recording medium total amount condition and a means for inputting a black amount adjustment condition relating to a method of creating black component data, the recording material total amount condition and the black amount adjustment condition. A conversion condition that is obtained from the device-dependent color data represented by a plurality of color component data that does not include the black component into device-dependent color data represented by a plurality of color component data that includes the black component. An image processing apparatus, characterized in that the first and second lookup tables are created using conditions. 24. A program which, when executed by a computer, causes the computer to operate so as to realize the image processing method according to any one of claims 16 to 20. 25. A recording medium on which the program according to claim 24 is recorded.