JPH11164162A - Color correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily perform color matching between a color image output device and a color image input device which have different color standards by finding and storing a color correction parameter of the color image input device from a standard value and a specific first measured value, and a color calibration parameter of the color image output device from the standard value and a specific second measured value. SOLUTION: A standard original 4, having arranged color patterns with known standard values, is read by a color image input device 1 to obtain a first measured value. Then a color correction parameter of the color image input device 1 is obtained from the standard values and the first measured value and is stored. Furthermore, image data of the standard original 4 which are corrected on the basis of the color calibration parameter of the color image input device 1 are printed on a color image output device 5, and the printed result is read by the color image input device 1 to obtain a second measured value. Then a color calibration parameter of the color image output device 5 is obtained from the standard original 4 and the second measured value and is stored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color proofing method for obtaining a color proofreading parameter for correcting a color reproduction characteristic of a color image processing apparatus.

[0002]

2. Description of the Related Art Generally, if a color scanner (color image input device) and a color printer (color image output device) of the same maker have the same color reference, the RGB signals from the color scanner are set. A color close to expectation can be reproduced by a color printer without particularly adjusting the color. However, since the color standards vary from manufacturer to manufacturer, in the case of color scanners and color printers from different manufacturers, it is necessary to perform color adjustment with a computer and check the printing state with a color printer. Met.

In order to calibrate changes in the environment and characteristics over time of a color printer, a correct calibration value cannot be obtained unless the reference of the RGB signal from the color scanner is the same as the reference of the RGB signal of the color printer. With color scanners and color printers having different color standards, such as products of other companies, appropriate color proofing could not be performed.

[0004] In recent years, network printers and scanners have appeared and a plurality of devices of various color standards have been mixed on a network, so that color adjustment and color matching of a color image handled by each device are more difficult. Has become. That is, when printing a color image captured by any of a plurality of color scanners on a network by any of a plurality of color printers on a network,
Since each color scanner has a different color criterion for each color printer, there is a problem that it is difficult to obtain a print in a color close to expectation.

Further, when a color image read by a color scanner located at a long distance is sent, there is a problem that color adjustment is difficult because the color standard of the color scanner is not known.

[0006]

As described above, when a color printer and a color scanner having different color references are used as a set, a certain degree of color matching cannot be obtained unless color adjustment is performed.

Further, with a color scanner and a color printer having different color standards, it is not possible to carry out proper color proofing with respect to changes in the environment and characteristics over time.

Accordingly, an object of the present invention is to provide a color proofing method capable of easily performing color matching between a color image output device and a color image input device having different color references.

Further, the present invention provides a color proofing method capable of easily performing appropriate color proofing for a change in characteristics over time and environment between a color image output device and a color image input device having mutually different color standards. The purpose is to provide.

[0010]

In order to solve this problem, a color proofing method according to the present invention uses a color image input device to read a standard document on which a color chart whose standard value is known in advance is read by a color image input device. A measurement value is obtained, a color calibration parameter of the color image input device is obtained from the standard value and the first measurement value, the color calibration parameter is stored, and the image data of the standard document corrected based on the color calibration parameter of the color image input device is obtained. Printing is performed by a color image output device, the printing result is read by a color image input device to obtain a second measurement value, and a color calibration parameter of the color image output device is calculated from a standard value and the second measurement value. It is intended to be saved.

Thus, the color image output device and the color image input device having different color references can calibrate the correction reference table for each color, and color matching between the two can be easily performed.

In addition, it is possible to easily perform appropriate color proofing with respect to environmental and temporal changes in characteristics between a color image output device and a color image input device having mutually different color references.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a standard image on which a color chart whose standard value is known in advance is read by a color image input device to obtain a first measured value, The color calibration parameters of the color image input device are obtained from the values and the first measured values and stored, and the image data of the standard document corrected based on the color calibration parameters of the color image input device is printed by the color image output device. Then, the printing result is read by a color image input device to obtain a second measurement value,
This is a color calibration method in which color calibration parameters of a color image output device are obtained from a standard value and a second measurement value and stored, and correction of each color is performed by a color image output device and a color image input device having different color standards. This has the effect that the reference table can be calibrated and color matching between the two can be easily performed. In addition, there is an effect that it is possible to easily perform appropriate color proofing with respect to an environment or a change in characteristics over time between a color image output device and a color image input device having different color references.

According to a second aspect of the present invention, in the first aspect, the color image input device and the color image output device are connected on a common network. By creating the color calibration parameters of the color image input device from the standard original read by the device, the color correction of the color image sent from the color image input device which is not close to the user can be performed.

According to a third aspect of the present invention, a plurality of color calibration parameters of a plurality of color image input apparatuses and a plurality of color calibration parameters of a plurality of color image output apparatuses are obtained by the color calibration method of the first aspect. Among the color proofing parameters, a color proofing parameter that matches the connected color image input device and color image output device is selected, and the color of the connected color image input device and color image output device is selected based on the color proofing parameters. This is a color proofing method for changing a proofreading parameter. Since color proofing is automatically performed using an existing color proofing parameter, it has an effect that color proofing can be performed without fail.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the date and time when the color proofing parameter is created is added to the color proofing parameter. This is a color calibration method that selects the latest color calibration parameters from among a plurality of color calibration parameters that exist for a color image input device and a color image output device. This has the effect of being able to select

According to a fifth aspect of the present invention, in the third or fourth aspect, a plurality of color image input devices and a plurality of color image output devices are connected on a common network, respectively. This is a color proofing method for selecting a color proofing parameter corresponding to each of the selected one color image input device and one color image output device when selecting a parameter, and color proofing on a network can be performed more easily. It has the action of:

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

(Embodiment 1) FIG. 1 is a schematic diagram showing an overall configuration of a color image processing apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a diagram showing a color correction process in the color image processing apparatus of FIG. FIG. 3 is a circuit diagram showing a circuit configuration for executing a three-dimensional lookup table interpolation method. FIG. 4 is a flowchart showing a calibration method of a color correction lookup table of a scanner. FIG. 5 is a flowchart showing a calibration method of a color correction lookup table of a printer. It is a flowchart shown.

As shown in FIG. 1, a color image processing apparatus according to the present embodiment includes a color scanner (color image input device) 1 for reading a predetermined color image and a color printer (color image) for printing the read color image. Image output device) 5. A computer 2 is connected between the color scanner 1 and the color printer 5, and
The RGB signal generated through the color filter in the color scanner 1 is taken in and is
Perform color proofing to match. Then, the color printer 5 converts the RGB signals after the color processing which has been color-calibrated by the computer 2 into the CMYK signals which are the four primary colors of printing, and prints a color image.

The computer 2 has a color display 3
Are connected, and a color image read by the color scanner 1 is displayed on the color display 3.

In the color image processing apparatus according to the first embodiment of the present invention, a standard document 4 composed of color patches in which several kinds of colors are uniformly arranged in the entire color space is prepared.
The color level of the standard original 4 is measured as a standard value ( _Rmi , _Gmi , _Bmi ) by a colorimeter.

FIG. 2 shows a color correction process in such a color image processing apparatus. As shown, a color image input to the color scanner 1 is converted into RGB signals, and scanner color correction is performed by a three-dimensional lookup table interpolation method described later. Next, similar to the scanner color correction, the printer color correction is performed by the three-dimensional lookup table interpolation method, and is displayed on the color display 3. Then, the signals are converted into CMYK signals and output to the color printer 5.

Here, the three-dimensional lookup table interpolation method is shown in FIG.
This will be described with reference to FIG. The three-dimensional lookup table interpolation method
In this method, three-dimensional linear interpolation is performed by using grid point data with respect to an input between grid points, in which conversion values of discrete grid points in the GB space are stored as a reference table.

According to the circuit diagram for executing the three-dimensional lookup table interpolation method shown in FIG. 3, one output value R signal (or G signal, B signal) is converted from three input values RGB signal.
Are output, and the RGB signal is 8-bit data. The interpolation method uses a tetrahedral interpolation method.

As shown, the RGB input signals are
Bits and lower 5 bits, and the tetrahedron discriminating section 12 discriminates the tetrahedron belonging to the unit cube by the lower 5 bits. Further, the address generation unit 11 uses the upper three bits and the tetrahedron number determined by the tetrahedron determination unit 12 to calculate all R bits.
A unit cube in the GB space is determined, and an address of data of each grid point corresponding to a vertex of the tetrahedron is generated. The generated grid point address is stored in the grid point reference table data 1
3 to obtain a grid point reference table value. Then, the interpolation unit 15 multiplies the grid point reference table value by the weight coefficient obtained from the lower 5 bits in the weight coefficient calculation unit 14 to obtain an output value.

Next, a method of calibrating the color correction reference table of the scanner according to the present embodiment will be described with reference to the flowchart of FIG.

First, the standard original 4 is read by the color scanner 1, and the first measured values (R _Si , G _Si ,
B _Si ) is obtained (step 1). Here, i is an integer of 0 to n, where n indicates the number of color patches. Note that the scanner color correction processing has not been performed on the first measurement value. Then, based on the first measurement values (R _Si , G _Si , B _Si ) of the standard document 4 and the corresponding known standard values (R _mi , G _mi , B _mi ), a color correction reference table (color calibration) of the scanner is used. (Step 2). Finally, the color correction reference table of the scanner is rewritten to the reference table obtained in step 2 and stored (step 3).

With the above three steps, the calibration processing of the color correction reference table of the color scanner 1 is completed, and the color matching of the color scanner 1 is realized.

Next, a method of calibrating the color correction reference table of the printer according to the present embodiment will be described with reference to the flowchart of FIG.

First, as in step 1 of FIG. 4, the standard document 4 shown in FIG. 1 is read by the color scanner 1 to obtain first measured values (R _Si , G _Si , B _Si ) (step 1). Subsequently, a scanner color correction process is performed using the calibrated scanner color correction reference table described above (step 2). Thereafter, the RGB signals are subjected to color correction to the CMYK signals using the existing printer color correction reference table (step 3), and the standard document 4 is printed by the color printer 5 (step 4).

Then, the standard original printed in step 4
Draft 4 is a color scanner with a corrected color correction reference table
1 (Step 5), calibrated scanner color complement
Scanner color correction processing is performed by using the
2 (R_pi, G_pi, B _piGet) (step
6). Next, the second measured value obtained in step 6
(R_pi, G_pi, B_pi) And standard value (R_mi, G_mi, B_mi)When
Is determined (step 7), and the amount of
The color correction reference table (color calibration parameters)
(Step 8). Finally, the color correction reference table of the printer
Into the reference table obtained in step 8,
This is stored (step 9).

Through the above steps, the color printer 5 and the color scanner 1 having different color references can calibrate the correction reference tables for each color, and can easily perform color matching between them.

In addition, it is possible to easily perform appropriate color proofing for environmental changes and aging characteristics between the color printer 5 and the color scanner 1 having different color references.

(Embodiment 2) FIG. 6 is a schematic view showing an arrangement of a color image processing apparatus according to Embodiment 2 of the present invention.
FIG. 7 is a flowchart showing a color proofing method in the color image processing apparatus of FIG.

As shown in FIG. 6, a plurality of color scanners 18, 19, 20 and a plurality of color printers 16, 17 are connected on one network, and a computer 22 is further connected. Therefore, in the present embodiment, it is assumed that the color scanners 18, 19, 20 and the color printers 16, 17 are arranged at a long distance from each other. In this point, the present embodiment is different from the first embodiment in which the color scanner and the color printer are arranged within the reach of the person performing the correction.

When printing from a color scanner on a network to a color printer, the color scanners 18, 1
A color image is read by one of 9 and 20 and is taken into the computer 22. Next, a color printer 16 (or 17) to be printed is selected. The color scanner 18 (or 19, 20) reading the color image captured by the computer 22 and the color printer 16
(Or 17) is adjusted in color and output by the color printer 16 (or 17).

Here, the color scanner 1 at a long distance
FIG. 7 shows color matching of color images sent from a computer network from 8, 19, and 20.
This will be described with reference to FIG.

First, a standard document 4 and a color image to be sent are read by the color scanners 18, 19, and 20 at a long distance on the network (step 1), and the read values of the standard document 4 and the color image are read by the computer 22 via the network. (Step 2). Next, according to the flowchart shown in FIG. 5 of the first embodiment, a color correction reference table for the color scanners 18, 19, and 20 is created from the read values of the standard document (step 3). Finally,
Color correction is performed using the reference table created in step 3 (step 4).

As described above, the color scanners 18, 19,
By creating a color correction reference table for the color scanners 18, 19, and 20 from the standard document 4 read by the device 20, color correction of a color image sent from a color image input device that is not close to the user becomes possible. .

(Embodiment 3) FIG. 8 is an explanatory view showing a color correction reference table of a color image processing apparatus according to Embodiment 3 of the present invention, and FIG. 9 is an example of a color correction method using the color correction reference table of FIG. FIG. 10 is a flowchart showing another example of the color correction method using the color correction reference table of FIG.

In the present embodiment, when a plurality of color scanners and a plurality of color printers have the color correction reference table obtained in the first embodiment, as shown in FIG. It is composed of a reference table update date and time, a corresponding device name, and a reference table data group.

When such a color correction reference table is provided, the color calibration is executed according to the flowchart shown in FIG.

First, a color image input / output device such as a color scanner or a color printer is connected (step 1).
Next, the device name of the connected color image input / output device is obtained (step 2). Then, based on the device name, a color correction reference table that matches the device name is selected from a plurality of color correction reference tables obtained by the color calibration method described in the first embodiment (step 3). Finally, a color correction process is performed using the selected color correction reference table (step 4).

As described above, according to the present embodiment, the color calibration is automatically performed using the existing color correction reference table, so that the color calibration can be performed without fail.

Here, since the update date and time are given to the color correction reference table, if a plurality of color correction reference tables exist for the same color image input / output device, the latest color correction reference table is selected. can do.

A color calibration method using the latest color correction reference table will be described with reference to FIG.

First, a color image input / output device is connected (step 1), and the device name of the connected color image input / output device is obtained (step 2). Next, from the device name, a color correction reference table that matches the device name is selected from among the plurality obtained by the color proofing method described in the first embodiment (step 3). When there are a plurality of selected color correction reference tables, information on the update date and time is obtained, and the latest color correction reference table is selected (step 4). Finally, a color correction process is performed using the selected color correction reference table (step 5).

In this manner, the latest color correction reference table can be reliably selected from a plurality of existing color correction reference tables.

When a plurality of color scanners and color printers according to the present embodiment are connected on a common network as shown in FIG. 6, each one selected by the computer is used. By selecting a color correction reference table that matches a color scanner and a color printer and performing color calibration, color calibration on a network can be performed more easily.

[0051]

As described above, according to the present invention, the correction reference table for each color can be calibrated between the color image output device and the color image input device having different color standards, and the color matching between the two can be easily performed. The effective effect that it becomes possible is obtained. As a result, an optimal color configuration can be realized.

Further, according to the present invention, it is possible to easily perform appropriate color proofing with respect to environmental and temporal changes in characteristics between a color image output device and a color image input device having different color references. That is, an effective effect is obtained.

If the color image input device and the color image output device are connected on a common network, it is possible to effectively correct the color of a color image sent from a color image input device which is not close to the user. Is obtained.

If color proofing is performed by selecting color proofing parameters that match the connected color image input device and color image output device, the color proofing is performed automatically, so that the color proofing is surely performed. An effective effect is obtained.

By giving the date and time to the color proofing parameters, an effective effect that the latest color proofing parameters can be reliably selected can be obtained.

A color calibration parameter corresponding to one color image input device and one color image output device selected from a color image input device and a color image output device, each of which is connected on a common network, is selected. As a result, an effective effect that color calibration on the network can be performed more easily is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an overall configuration of a color image processing apparatus according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a color correction process in the color image processing apparatus of FIG. 1;

FIG. 3 is a circuit diagram showing a circuit configuration for executing a three-dimensional lookup table interpolation method;

FIG. 4 is a flowchart showing a method of calibrating a color correction reference table of the scanner.

FIG. 5 is a flowchart illustrating a method of calibrating a color correction reference table of the printer.

FIG. 6 is a schematic diagram illustrating an arrangement of a color image processing apparatus according to a second embodiment of the present invention.

FIG. 7 is a flowchart illustrating a color proofing method in the color image processing apparatus of FIG. 6;

FIG. 8 is an explanatory diagram showing a color correction reference table of the color image processing device according to the third embodiment of the present invention.

FIG. 9 is a flowchart illustrating an example of a color correction method using the color correction reference table in FIG. 8;

FIG. 10 is a flowchart showing another example of the color correction method using the color correction reference table of FIG. 8;

[Explanation of symbols]

 Reference Signs List 1 color scanner (color image input device) 4 standard document 5 color printer (color image output device) 16 color printer (color image output device) 17 color printer (color image output device) 18 color scanner (color image input device) 19 color Scanner (Color Image Input Device) 20 Color Scanner (Color Image Input Device)

Claims (5)

[Claims] A color image input device reads a standard original on which a color chart whose standard value is known in advance is determined by a color image input device to obtain a first measured value, and the color image is obtained from the standard value and the first measured value. A color calibration parameter of the input device is obtained and stored, and the image data of the standard document corrected based on the color calibration parameter of the color image input device is printed by a color image output device. A color proofing method comprising: obtaining a second measured value by reading with an input device; obtaining a color proofing parameter of the color image output device from the standard value and the second measured value; and storing the color proofing parameter. 2. The color proofing method according to claim 1, wherein said color image input device and said color image output device are connected on a common network. 3. A color calibration method according to claim 1, wherein a color calibration parameter of a plurality of color image input devices and a color calibration parameter of a plurality of color image output devices are obtained. Selecting the color calibration parameters that match the color image input device and the color image output device; and changing the color calibration parameters of the connected color image input device and the color image output device based on the color calibration parameters. A color proofing method. 4. A date and time when the color proofing parameter is created is given to the color proofing parameter. In selecting the color proofing parameter, a plurality of color proofing parameters exist for the same color image input device and the same color image output device. 4. The method according to claim 3, wherein the latest color calibration parameter is selected from the color calibration parameters.
The color proofing method described. 5. A plurality of color image input devices and a plurality of color image output devices are respectively connected on a common network. In selecting the color proofing parameters, one color image input device and one color image input device are selected. 5. The color proofing method according to claim 3, wherein the color proofing parameter corresponding to the device and the color image output device is selected.