JP2002152529A - Image processing method, device thereof and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately calibrate color reproduction of a secondary color and a tertiary color of a coloring material color used in a color output device. SOLUTION: When a table for converting an input color component signal into a color component signal corresponding to a coloring material color used in a color output device is calibrated, patches corresponding to the primary, secondary and tertiary colors of the coloring material color are outputted by the color output device. According to patch measurement data obtained by measuring the outputted patches, a hierarchy correction table corresponding to the primary, secondary and tertiary colors of the coloring material color is calibrated. According to the hierarchy correction table, a plurality of first lines from white to the primary color and the secondary color in a three-dimensional color structure expressed by a plurality of color components comprising the input color component signal are specified. According to the hierarchy correction table, a plurality of second lines from the primary color and the secondary color to black in the three-dimensional color structure are specified. According to the hierarchy correction table, a third line from white to black in the tree-dimensional color structure is specified. The table for the conversion is produced according to the first, second and third lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention An image processing method, apparatus, and recording medium for calibrating a table for converting an input color component signal into a color component signal corresponding to a color material color used in a color output device.

[0002]

2. Description of the Related Art Conventionally, a color printer calibration technique is configured as shown in a block diagram of FIG. In FIG. 26, 2601 is an ink color separation processing unit, and 2602 is CMYK one-dimensional L for calibration.
A UT unit, 2603 is a halftone processing unit, 2604 is a color printer engine unit, 2605 is a CMYK one-dimensional LUT creation unit, and 2606 is a sensor unit. 2601
Performs an ink color separation process on input multi-valued RGB image data into cyan C, magenta M, yellow Y, and black K, which are color material colors (hereinafter, referred to as ink colors) of a color printer. The multi-valued CMYK data output from the ink color separation processing unit 2601 is corrected in 2602 by using a CMYK one-dimensional LUT corresponding to the color reproduction characteristics of the printer to correct the gradation characteristics, and the multi-valued C′M 'Y'K' is output. This processing realizes calibration according to the characteristics of the color printer. Halftone processing unit 2
In step 603, halftone processing for binarizing the corrected multi-valued C'M'Y'K 'data with the number of gradations printable by a color printer, for example, in the case of a binary printer, is performed. M "Y" K "binary data is output. The color printer engine unit 2604 performs printing based on the input C "M" Y "K" binary data.
Here, the sensor unit 2606 is a sensor unit for examining the color reproduction characteristics of the color printer engine unit.
The CMYK one-dimensional LUT creation unit 2605 uses the sensor unit 2
Based on the color reproduction characteristics of each color of CMYK from 605, a one-dimensional LUT of CMYK is created so that the target color reproduction characteristics are obtained for each color.
Writing to the UT unit 2602 is performed.

[0003]

However, in the above-mentioned conventional example, since the calibration is performed independently for each CMYK color, a high-precision calibration can be realized for the primary color. However, the secondary color such as Red, Green, and Blue can be realized. For colors other than the primary color, such as the tertiary color and the quaternary color constituting the color and the gray line, there is a problem that high-accuracy calibration cannot be realized.

Accordingly, an object of the present invention is to enable high-accuracy calibration to be realized for a secondary color or a tertiary color constituting a gray line.

[0005]

In order to achieve the above object, the present invention has the following arrangement.

An image processing method according to the present invention is an image processing method for calibrating a table for converting an input color component signal into a color component signal corresponding to a color material color used in a color output device. The patches corresponding to the secondary and tertiary colors are output by the color output device, and the patch measurement data obtained by measuring the output patches are used to determine the levels corresponding to the primary, secondary and tertiary colors of the color material colors. Calibrating a tone correction table, and forming a plurality of first lines from white to a primary color and a secondary color in a color solid indicated by a plurality of color components indicating the input color component signal based on the tone correction table. Defining, based on the gradation correction table, a plurality of second lines from the primary color and the secondary color to black in the color solid, and defining the color based on the gradation correction table. Defining a third line from white to black in the body, the first, characterized in that to create the table from the second and third lines.

[0007]

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of this embodiment. FIG. 2 illustrates a system configuration including a color printer. In FIG. 2, reference numeral 201 denotes a computer holding image data, and 202 denotes a monitor for displaying image data held by the computer 201. , 203 are color printers for printing image data. FIG.
This embodiment is mounted inside the color printer 203 shown in FIG.

In FIG. 1, reference numeral 101 denotes a color matching processing unit for matching the reproduction characteristics of the input image data RGB with the color of the printer, and 102 denotes an R'G'B '8-bit signal from the color matching processing unit 101. Based on the data based on the ink color separation table 105, the color material colors (ink colors) C '(cyan), M' (magenta),
An ink color processing section for converting into Y '(yellow) and K' (black) is represented by a printer 103. The C'M'Y'K '8-bit data from the ink color separation processor 102 is expressed by a printer. A halftone processing unit for converting the number of possible gradations. Reference numeral 104 denotes a color printer engine unit, which receives C “M” from the halftone processing unit 103.
The development print processing is performed based on Y "K".

In the present embodiment, the calibration of the color printer is realized by changing the contents of the ink color separation table section 105. The calibration controller unit 106 changes the contents of the ink separation table unit 105 and controls a series of controls for executing the calibration of the color printer 203. When a calibration command is issued from a controller that controls the entire color printer 203 (not shown) to the calibration controller unit 106, the calibration controller unit 106 checks a color for checking the characteristics of the color printer engine 104. Patch halftone section 10
Output to 3. The halftone unit 103 performs halftone processing on the input color patch data and transfers the halftone processing to the color printer engine unit 104. The color printer engine unit 104 performs a development process based on the color patch data from the halftone processing unit 103. As the development processing, there are cases where printing is performed on printing paper, development processing at an intermediate stage before printing on printing paper, and the like. The sensor unit 107 measures a color patch of a development processing result in the color printer engine 104,
The result is transferred to the calibration controller 106.

The calibration controller 106
Then, based on the results from the reference table unit 110 in which the target characteristics of the color printer engine unit 104 are stored and the sensor unit 107, the values of 1, 2, and
A correction table up to the tertiary color is created, and the result is transferred to the seven-line table unit 109. 7-line table unit 1
In step 09, W-Bk, W-C-Bk, W-M-Bk, and W-Y-Bk are based on the correction tables for the primary, secondary, and tertiary colors.
A seven-line table of k, WR-Bk, WG-Bk, and WB-Bk is created. Next, the interpolation processing unit 108
An interpolation process for obtaining the internal table data is executed using the seven-line table unit 109, and the result is stored in the ink color separation table unit 105.

With the above, the calibration command is completed, and thereafter, the color printer 203 executes the ink separation processing by using the corrected ink color separation table unit 105 and performs printing.

FIG. 3 is a diagram for explaining a processing flow for creating correction tables 1, 2, and 3 from White. The processing contents will be described with reference to FIGS.

In FIG. 3, step S3-0 is a start step, and step S3-1 is a primary color patch pattern generation step for checking the CMYK primary color gradation characteristics of the color printer engine unit 104. Then, a patch pattern as shown in FIG. 4 is generated. FIG.
FIG. 6 is a diagram showing a patch pattern for examining MYK primary color gradation characteristics. The patch pattern is determined by setting five sample points for each CMYK color based on the values of the primary color initial table in FIG. Step S3-2 is a primary color patch development processing step, in which the primary color patch data shown in FIG. 4 is subjected to halftone processing by the halftone processing unit 103 in FIG.
4 is developed. Step S3-3 is a primary color patch measurement processing step in which the sensor unit 107 measures the development processing result.

FIG. 6 is a diagram showing a graph of the measurement results and primary color target characteristics stored in the reference table unit 110. In the same drawing, the primary color actual characteristic of the measurement result shows that the output density is higher than the primary color target characteristic. Step S3-4 is a step of determining whether or not the primary color error is within an allowable range. In step S3-4, five representative points (α1, α2, α3, α4, α5) measured as shown in FIG.
From 5), the values between them are interpolated to generate the gradation characteristics of each of the CMYK colors, the error between the primary color actual characteristics and the primary color target characteristics is calculated, and the maximum value of the error is an allowable value (for example, ε1). It is determined whether it is within.

If the result of the determination in step S3-4 is No, the operation proceeds to step S3-5. Step S3-5 is
This is a primary color correction table creation step. As shown in FIG. 6, when the output density of the output signal α3 is β2, the target characteristic of the output signal α3 is β1, so that the output density of β1 is realized. Let α3 ′ be a primary color correction table for α3. Similarly, the values that would achieve the primary color target characteristics are calculated for α1, α2, α3, α4, and α5, and the values in the meantime are interpolated to correct the primary color as shown in FIG. A table is generated.

Next, in step S3-1, step S3-1
A new patch pattern is generated based on the primary color correction table generated in 3-5. Thereafter, the processes in steps S3-2 and S3-3 are performed in the same manner as the previous time, and in step S3-4, it is determined whether the primary color error is within the allowable value ε1. Proceeding to S3-5, the processes from step S3-1 to step S3-5 are repeated, and in the case of Yes, the process proceeds to step S3-6.
The processing from the above steps to S3-5 is C, M, Y,
This process is performed for each of the K colors to generate a CMYK primary color correction table as shown in FIG.

Next, the generation of the secondary and tertiary color correction tables is performed by the processing from steps S3-6 to S3-11. Step S3-6 is a step of creating an initial secondary and tertiary color correction table. Based on the primary color correction table created in steps S3-1 to S3-5, an initial secondary and tertiary color correction table is created. Create a correction table.

FIG. 8 is a diagram showing a state where the secondary color line M, Y ink table between White and Red is modified. In FIG. 8, the M and Y ink initial table is a diagram showing a table of M and Y inks constituting a Red secondary color in an initial state before correction. If the printer is in the ideal state, the target secondary color line can be configured as it is in the initial state, but the printer may fluctuate from the ideal state depending on the number of prints and the usage environment of the printer. This is corrected using the primary color correction table. The initial correction table for the M and Y inks in FIG. 8 is a table in which the correction table for the secondary red color is created using the primary color correction table shown in FIG. The output signal of the table is given as an input signal of the primary color correction table in FIG. 7, and the output signal value is used as the initial correction table for the M and Y inks.

Next, step S3-7 is a step of generating a secondary or tertiary color patch pattern, and using the secondary and tertiary color initial correction tables, Red and Green shown in FIG.
A secondary color of n, Blue and a tertiary color patch pattern of Gray are generated. For example, the value of the patch of Red is M, for the input signal values α1, α2, α3, α4, α5 in FIG.
It is configured using the output signal value of the Y ink initial correction table. Step S3-8 is a secondary and tertiary color patch development processing step, in which halftone processing is performed on the secondary and tertiary color patch data shown in FIG. 9 by the halftone processing unit 103 in FIG. Development processing is performed at 104. Step S3-9 is a secondary and tertiary color patch measurement processing step in which the sensor unit 107 measures the development processing result. Step S3-10 is:
In this step, it is determined whether or not the secondary and tertiary color errors are within an allowable value (for example, ε2). Is determined by the color difference of

FIG. 10 is a diagram for explaining steps S3-10 and S11. P0 to P7 indicate the target colors of the secondary and tertiary colors stored in the reference table section 110 and the peripheral colors thereof as CIE. P8 is plotted from the measured values (L8, a8, b8) in the second and third order color patch measurement processing step S3-9. For each point, L * a * indicating the color of that point
The value of b * and the amount of ink constituting that point are shown.
For example, P0 is such that L * of CIE is L0, a * of CIE is a0, b * of CIE is b0, and the amount of cyan ink is C0,
It shows that the magenta ink amount is M0, the yellow ink amount is Y0, and the black ink amount is K0. However, the element (C8, M8, Y8, K8) of P8 is (L
8, a8, b8) are obtained by interpolation from the surrounding ink amounts of P0 to P7. Here, if the measurement result of the patch (0, Mr, Yr, 0) for the Red input signal α3 shown in FIG. 8 is P8 and the target color is P0, the error ΔE is ΔE = sqrt (L
0−L8) ＾ 2 + (a0−a8) ＾ 2 + (b0−b8)
＾ 2), and in step S3-10, the error ΔE is
It is determined whether it is within 2 or not, and in the case of No, the process proceeds to step S3-11. Step S3-11 is a step of creating a secondary and tertiary color correction table, in which the ink amount is corrected using the difference between the ink amount of the target color and the ink amount based on the measured value. For example, if the correction value of the magenta ink at the point of the red input signal α3 is Mr1, and the correction value of the yellow ink is Yr1, Mr1 and Mr2 are as follows: Mr1 = Mr + (M0−M8) Yr1 = Yr + (Y0−Y8) Becomes Other values α1, α2, α4, and α5 of the secondary color line from White to Red are obtained in the same manner, and FIG.
The M, Y ink correction table 1 is created. G
A correction table is created in the same manner for the five points of the secondary color of green and blue and the tertiary color line of gray, and the processing of the secondary color correction table creation step S3-11 is completed.
Proceed to step S3-7.

In step S3-7, based on the result of step S3-11 for creating a secondary and tertiary color correction table, the
Using the next color correction table 1, Red,
A green, blue secondary color and a gray tertiary color patch pattern are generated. For example, the value of the Red patch is configured using the output signal values of the M, Y ink correction table 1 for the input signals α1, α2, α3, α4, and α5 in FIG. Thereafter, the processing in steps S3-8 and S3-9 is performed in the same manner as the previous time, and in step S3-10, it is determined whether or not the secondary and tertiary color errors are within the allowable value ε2. Then, the process proceeds to step S3-11 to repeat the processes from step S3-7 to step S3-11. If the determination result in step S3-10 is Yes, the process proceeds to step S3-12, and the creation of the correction table for the primary, secondary, and tertiary colors ends.

Hereinafter, a method of creating an ink separation table based on the correction tables of the primary, secondary, and tertiary colors obtained in the processing of steps S3-0 to S3-12 will be described.

FIG. 11A shows an ink color separation table section 1.
FIG.
Corresponding to the input data R'G'B ', data corresponding to grid points distributed in a grid in a cube on an RGB dimensional space is stored as a table. In the case where the input R'G'B 'data is not on the grid of the ink color separation table unit 105, the ink color separation processing unit 102 performs interpolation processing using nearby grid point data. There are many interpolation methods such as tetrahedral interpolation and cubic interpolation. However, since the ink separation table creation method and image processing do not depend on a specific interpolation method, any interpolation method may be used. .

FIG. 11B is a diagram for explaining a concrete table creation method after FIG. 12; the eight vertices of the cube shown in FIG. 11A are respectively represented by W, C, M, and Y. ,
R, G, B, Bk, WC, M, YR, G, BB
The line connecting k and W-Bk is shown by a solid line or a dotted line. Here, when the number of bits of the input data of the ink color separation processing unit 102 is 8, W, C, M,
The coordinates of Y, R, G, B, Bk and each vertex are W = (255, 255, 255), and White,
That is, it indicates the color of the print paper. C = (0, 255, 255), indicating Cyan primary colors. M = (255, 0, 255), indicating the primary color of Magenta. Y = (255, 255, 0), indicating the Yellow primary color. R = (255, 0, 0), indicating the Red primary color. G = (0, 255, 0), indicating a Green primary color. B = (0,0,255), indicating a Blue primary color. Bk = (0,0,0), indicating Black, the darkest point of the printer.

The method of creating an ink color separation table according to the present embodiment is based on the WC, M, Y, R, G, B-Bk,
Then, an ink separation table of a line connecting W-Bk is created, and then all table data is created for the ink colors corresponding to the internal grid points by an internal interpolation process.

FIG. 11C is a diagram for explaining the inking points. W-Bk, C, M, Y, R, G, B-
It is a figure for explaining that an inking point can be controlled three-dimensionally continuously by seven points on seven lines of Bk.

FIG. 12 shows an ink color separation table section 105.
6 is a flowchart for creating a. In the figure, step S12-0 is a start step,
The creation of a table for downloading to the ink color separation table unit 105 is started. Step S12-1 is to
This is a step of creating an ink color separation table for the Bk line, and creates an ink color separation table for the gray line from White to Black based on the final result of the tertiary color correction table and the K ink correction table. Step S12-2 is a step of creating an ink color separation table for the WC, M, Y, R, G, and B lines, and based on the final result of the primary and secondary color correction tables, White-Cya.
n, W-Magenta, W-Yellow, W-Re
d, W-Green and W-Blue line ink color separation tables are created. Step S12-3 is:
This is a step of creating an ink color separation table for the C, M, Y, R, G, B-Bk lines, and based on the final result of the primary and secondary color correction tables, Cyan-Black, Magen.
ta-Black, Yellow-Black, Red
-Black, Green-Black, Blue-B
Create an ink color separation table for the luck line. Step S12-4 is a step of executing internal interpolation processing, and creates an ink color separation table corresponding to each grid point in the internal space of the line created in steps S12-1 to S12-3. Step.

In the table creation in step S12-3, by creating a table in which the optimal UCR amount and BG amount are set for each hue, the influence of the granularity due to black is maximized while maximizing the color reproduction range of the printer. It is possible to set a table that is suppressed as much as possible.

The contents of the internal interpolation processing in step S12-4 will be described below with reference to FIG. Step S12-
In the four internal interpolation processing, one surface as shown in FIG. 13 is divided into six tetrahedrons each formed of a triangle, and the interpolation processing is executed for each tetrahedron. FIG. 13A illustrates a vertex W,
FIG. 13B shows a tetrahedron composed of R, M, and Bk.
Is a tetrahedron composed of vertices W, M, B, and Bk,
FIG. 13C is a tetrahedron composed of vertices W, C, B, and Bk. FIG. 13D is a tetrahedron composed of vertices W, Y, R, and Bk. Are the vertices W, Y, G,
FIG. 13B shows a tetrahedron composed of vertices W, C, G, and Bk.

FIG. 14 is a flowchart for explaining the specific processing of the internal interpolation processing in step S12-4. In FIG. 14, step S14-1 is an ink color selection step. In order to determine an ink amount corresponding to each grid in subsequent steps, cyan, magenta, yellow, and black ink colors are sequentially selected. . Step S14-2 is a step of selecting a tetrahedron and dividing it into a plurality of triangles.
Four tetrahedrons are sequentially selected and divided into a plurality of triangles. As a method of dividing into a plurality of triangles, for example, FIG.
In the case of, first, the triangle is divided into four triangles, that is, a triangle WMR, a triangle WMBk, a triangle WRBk, and a triangle MRBk, which form a tetrahedron. To divide it into multiple triangles. Next, step S14-3 is an execution step of performing a two-dimensional interpolation process on the target triangle.
The contents of the two-dimensional interpolation processing for each triangle are shown in FIG.
This will be described in detail below.

Step S14-4 is a step of calculating the distance between the ink contours of the interpolation processing result and each grid.
Execution step S1 of two-dimensional interpolation processing for each triangle
The distance between the contour line of FIG. 15 created by 4-3 and the grid corresponding to the ink color separation table unit 105 is calculated. Step S14-5 is a step of determining the ink amount of the target grid, and calculating the distance between the ink contour line and each grid as a result of the interpolation processing, the smallest distance calculated as a result of step S14-4 is determined as the ink amount of the target grid. To be determined. Step S14-6 is a step of determining whether or not an undetermined grid exists. If there is an undetermined grid, go to step S14-4,
Steps S14-4 and S14-5 for the next grid
Perform If the ink amounts of all the grids have been determined for the target triangle in step S14-3, the process proceeds to step S14-7.

Step S14-7 is a step for determining whether or not there is an unprocessed triangle.
It is determined whether or not the processing has been completed for the plurality of triangles divided in 4-2. If there is an unprocessed triangle, the process proceeds to step S14-3, and the process proceeds to steps S14-3 to S14-3.
The processing up to S14-6 is repeated. Step S14-2
If the processing has been completed for all the triangles of the tetrahedron selected in, the process proceeds to step S14-8.

Step S14-8 is a step of determining whether or not an unprocessed tetrahedron exists. If an unprocessed tetrahedron exists, the process proceeds to step S14-2,
Steps S14-2 to S14-7 are repeated.

If the processing has been completed for all tetrahedrons, the flow advances to step S14-9. Step S14-9
Is a step of determining whether or not an unprocessed ink color exists. If an unprocessed ink color exists,
Proceed to step S14-1 and proceed to steps S14-1 to S1.
Repeat steps 4-8. When the processing is completed for all the ink colors, the process returns to 12-2.

Next, the contents of the specific processing in the execution step S14-3 of the two-dimensional interpolation processing for the target triangle will be described with reference to FIG. FIG. 15 is a diagram illustrating ink amount contours as a result of the internal interpolation when the ink amounts on three sides of a certain triangle are shown as curves as illustrated. In the figure, the change of the ink amount at the side 0A is shown in the right side graph of the side, and the peak ink amount is 90%.
%. The change in the ink amount on the side 0B is shown in the upper left graph of the side, and the ink amount at the peak is 30.
%. Then, the change in the ink amount on the side AB is
In the graph below that side, the peak is 60
%.

FIGS. 16, 17, and 18 are flow charts for explaining in detail the execution of the two-dimensional interpolation processing on the target triangle. Hereinafter, the description of FIGS. 16, 17, and 18 will be described using the case of FIG. 15 as an example. In FIG. 16, step S16-1 is a step of detecting the point of the maximum value of the ink amount on the three sides of the target triangle. Step S16-2 is a step of deriving a magnitude relationship between the three maximum values on the three sides. Step S16-3 is an interpolation step between the maximum value points on the three sides.
The two maximum values are connected by a straight line, and an interpolation operation is performed between the two maximum values. Step S <b> 16-4 is a step of generating ink amount contour lines by connecting points of equal ink amount levels on a total of six straight lines including three straight lines formed by three sides of the target triangle and three maximum value points. Then, step S16
Step -5 is a step of performing a non-linear approximation of the ink amount contours. Of the ink amount contours generated in step S16-4, a portion that changes in a rectangular shape in a region inside a triangle is approximated to a non-linear shape. This is a step for smoothly generating ink amount contour lines.

Step S16-4 will be described in detail with reference to FIG. In the figure, a step S17-1 is based on the results of the steps S16-1 and S16-2, and among the three maximum value points, the largest point is a point D, its magnitude is d, and a point of an intermediate magnitude is d. Is a point H, its size is h, the smallest point is a point J,
The size is set as j. In the example of FIG. 15, d = 9
0, h = 60 and j = 30. Step S17-2
A is the vertex of the side including the point D and the side including the point H, B is the vertex of the side including the point H and the side including the point J, and 0 is the vertex of the side including the point J and the side including the point D. This is the setting step. In step S17-3, an interval s between contour lines to be generated and an initial value i = d
This is a step for setting -s.

Hereinafter, steps S17-4 to S17-1
Contour lines are sequentially created in loop 2 until the ink amount becomes zero. Step S17-4 is a step of determining whether or not d> i ≧ h. If Yes, step S1
At 7-6, between the straight line DA and the straight line DH, the straight line DH and the straight line D
The points of value i between J and between the straight line DJ and the straight line D0 are connected. In the example of FIG. 15, since the contour line interval s = 15, i
A contour line of = 15 is generated as G0-G1-G2-G3, and a contour line of i = 60 is generated as H0-H-H1-H2.

If No in step S17-4, the process proceeds to step S17-5. Step S17-5
Is a step of determining whether or not h> i ≧ j.
In the case of es, in step S17-7, between the straight line DA and the straight line AH, between the straight line HB and the straight line HJ, and between the straight line HJ and the straight line DJ.
And the point of the value i between the straight line DJ and the straight line D0. In the example of FIG. 15, the contour line at i = 45 is I0-I
1, I2-I3-I4-I5 are generated, and the contour line at i = 30 is generated as J0-J1, J2-JJ-3.

In the case of No at step S17-5,
Proceed to step S17-8. Step S17-8 is performed between the straight line DA and the straight line AH, between the straight line HB and the straight line BJ, and between the straight line JD and the straight line JD.
And the step of connecting the points of the value i between the straight line D0. In the example of FIG. 15, the contour line at i = 15 is K0−K
1, K2-K3 and K4-K5.

Step S17-9 is a step for judging whether i = 0 or not. If Yes, the generation of contour lines of all target triangles ends, and the process returns to 7-2. N
In the case of o, the process proceeds to step S17-10. Step S
In step 17-10, the operation of i = is is performed, and step S
In 17-11, it is determined whether or not i> 0.
In the case of, go to step S17-4, in the case of No,
In step S17-12, the calculation of i = 0 is performed, and the process proceeds to step S17-4. As described above, steps S17-4 to S17-1 are performed until the contour line value i becomes zero.
Repeat the loop up to 2.

FIG. 15 shows an example in which s = 15 is set for easy understanding. However, in order to make the grid value more accurate, s = 1 is set and contour lines are set every step. Needless to say, it should be generated.

Next, step S16-5 will be described in detail with reference to FIG. In the figure, step S18-1
Is a setting step of the approximation degree parameter a, and is a step for setting the non-linearity when a curve is generated for the non-linear approximation. The approximation degree parameter a is a = 1, 2, 2,
Can be set as 3, 4,..., And when a = 1, the degree of approximation is large by linear approximation, and the degree of approximation decreases as the value of a = 2, 3, 4,. Thus, the smoothness of the ink amount contour line increases.

FIG. 19 shows that when the value of the approximation degree parameter a is set to 1, 2, 3, and 4 with respect to the contour line G0-G1-G2-G3 at i = 75 in FIG. Curves curve1, curve2, curve
3, curve4 are shown. As is clear from FIG. 19, as the value of the approximate parameter a increases, the smoothness of the ink amount contour line increases. The user can set the value of the approximation parameter a according to the characteristics of the printer. There are various methods for generating a nonlinear approximation curve. For example, when a spline curve is used, a primary spline curve when a = 1, a secondary spline curve when a = 2, and a = 3
Can be realized by setting a cubic spline curve at the time of, and a quaternary spline curve at the time of a = 4.

In step S18-2, an initial value i = ds
Is a parameter for setting an initial value of an ink contour line for performing nonlinear approximation. Step S18-3 is a step of determining d>i> j, and in the case of No, the process returns to 14-2 to end the non-linear approximation process of the ink amount contour. In the case of Yes, the process proceeds to step S18-4. Step S18-4 is a step of setting the vertices. In the example of FIG. 15, the vertices G0, G1, G2, and G3 forming the contour of i = 75 are set. Step S18-5 is a step of generating a non-linear approximation curve, in which a non-linear curve is generated based on the set value of the approximation degree parameter a and the set vertex. In the example of FIG. 15, an approximate curve represented by a thick line is generated for G0, G1, G2, and G3 connected by a thin line. Step S
18-6 is an i = is step, and the operation of i = is is executed. In the example of FIG. 15, i = 60 is set, and thereafter, the loop is repeated from step S18-3 to S18-6.

When i = 60, H, H1, and H2 are selected in step S18-4. Non-linear approximation is performed in step S18-5, and when i = 45, step S18-4.
, 12, 13, 14, and 15 are selected, and step S
A non-linear approximation is generated at 18-5. If i = 30, No is selected in step S18-3 and 14-2.
Return to

The operation of the case where the ink curves on the three sides are different from the example of FIG. 15 will be described with reference to the examples of FIGS. FIG. 20 shows an example in which the maximum values of the three sides are the same. In this case, although not explicitly shown in FIG. 17, only the contour generation step of step S17-8 is executed, and the contours shown in FIG. Is generated. FIG. 21 shows a case where the ink amounts on one side are all 0 and the maximum values on the other two sides are the same. In this case, between the straight line DA and the straight line AH, and between the straight line HB and the straight line D0. The points of the value i are connected to each other as shown in FIG. FIG.
Is the case where the maximum values of the two sides are the same and overlap the point A. In this case, in FIG. 17, in step S17-6, D, A, and H are not subjected to the contour generation processing because they are the same point, and in step S17-7, D, A, and H are set between the straight line DA and the straight line AH. Does not exist because of the same point, and between the straight line HJ and the straight line DJ, D and H are not executed because of the same point, and the points of the value i only between the straight line HB and the straight line HJ and only between the straight line DJ and the straight line D0 are respectively defined. A tying process is performed. Also, S
17-8 is a process in which the straight line DA and the straight line AH do not exist because D, A, and H are the same point, and connect the points of the value i only between the straight line HB and the straight line BJ and only between the straight line J0 and the straight line D0. Done. Then, the non-linear approximation processing of the ink contours in step S16-5 is performed, and the contours as shown in FIG. 22 are obtained.

FIG. 23 shows the vertex WCB in FIG.
FIG. 9 is a diagram for explaining an example of interpolation within a triangle by k, and shows examples of curves of ink color tables of C, M, Y, and K on each side. FIG. 24 shows contour lines for each ink color in FIG. 23, and FIG. 24-1 shows contour lines for the C ink amount. In this case, the case of FIG. 22 is shown. FIG. 24-2 shows M ink amount contour lines,
This case is the case of FIG. FIG.
Ink volume contours are shown, again in the case of FIG. FIG. 24D shows a contour line of the K ink amount. In this case, the case of FIG. 21 is used. However, since the K ink is inserted from the middle, the region of the ink amount 0 widely exists. A contour line of the K ink amount is generated halfway.

As described above, when the output number of the printer increases or the usage environment changes extremely,
There was a problem that the color reproduction characteristics of the printer fluctuated, but in the conventional method, only the CMYK primary colors could be calibrated with high accuracy. In the present embodiment, Red (MY) and Green (YC) , Blue
Calibration can be performed with high accuracy even for colors other than primary colors, such as secondary colors of (CM) and tertiary colors of CMY.

(Modification) In the first embodiment, the expression “ink color” is used as the color material color of the printer. However, this is not limited to ink as the color material color. Any color material color used for a color printer, such as a toner, may be used. In the creation of the primary color correction table, the density was used as the measured value and reference data of the primary color. However, the unit of this data is not limited to the density, but can be used to check the primary color reproduction state such as brightness and luminance. Good. Also, when creating the secondary and tertiary color correction tables, the measurement values and reference data of the secondary and tertiary colors are
Although CIE-L * a * b * is used, the unit of this data is not limited to this, and any data may be used as long as it can express color in three dimensions, such as luminance such as RGB and XYZ, and CMY filter density.

Further, in the first embodiment, an example in which four colors of CMYK are used as the ink colors of the printer has been described.
A six-color printer using light and dark inks for cyan and magenta can be easily realized only by increasing the number of ink colors by two.

In the case of other color inks such as red and green other than CMYK, the primary colors are C, M, Y,
Six colors of R, G, K, and secondary colors are RM, B, CG, GY, Y
Five colors of R and CM that constitutes part of the gray line
For the fifth color of YRG, a correction table of the first, second and fifth colors is created. Then, as shown in FIG. 25, RM is located between R and M, RY is located between R and Y, GY, G is located between G and Y.
GC is newly set in the middle between C and C, and the tetrahedrons W, C, B,
Bk and tetrahedrons W, B, M, Bk, and a new tetrahedron W,
M, RM, Bk and tetrahedron W, RM, R, Bk and tetrahedron W, R, RY, Bk and tetrahedron W, RY, Y, Bk and tetrahedron W, Y, GY, Bk and tetrahedron W, By defining a total of 10 tetrahedrons of GY, G, Bk and tetrahedrons W, G, GC, Bk and tetrahedrons W, GC, C, Bk, even if the ink color increases, six colors can be easily obtained. An optimal ink color separation for the printer can be provided.

In the first embodiment, the present invention is implemented by the controller in the printer. However, the present invention is not limited to this, and the software in the computer shown in FIG. It can also be realized by creating an ink color separation table by software processing and downloading the result to the ink color separation table unit 105 mounted inside the printer.

In this case, the program code of the software implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer, for example, the program code The storage medium storing the information constitutes the present invention.

As a storage medium for storing such program codes, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-R
An OM, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer, or another program. Needless to say, the program code is included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with application software or the like.

Further, the supplied program code is stored in a memory provided in a function expansion board of the computer or a function expansion unit connected to the computer, and then stored in the function expansion board or the function storage unit based on the instruction of the program code. It is needless to say that the present invention includes a case where a provided CPU or the like performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0058]

According to the present invention, high-accuracy calibration can be performed for secondary colors and tertiary colors constituting gray lines.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration related to calibration in a first embodiment.

FIG. 2 is a diagram illustrating a system configuration according to the first embodiment.

FIG. 3 is a diagram illustrating a processing flow for creating a correction table for primary, secondary, and tertiary colors from White.

FIG. 4 is a diagram showing a patch pattern for examining CMYK primary color gradation characteristics.

FIG. 5 is a diagram showing a primary color initial table and a primary color correction table.

FIG. 6 is a diagram illustrating primary color actual characteristics and primary color target characteristics of measurement results from a sensor unit 107;

FIG. 7 is a diagram illustrating a CMYK primary color correction table derived by processing from steps S3-1 to S3-5.

FIG. 8 is a diagram showing an M, Y ink initial table, an M, Y initial correction table, and an M, Y correction table 1 constituting a Red secondary color.

FIG. 9 is a diagram illustrating patch patterns of secondary and tertiary colors.

FIG. 10 is a diagram for explaining steps S3-10 and S11.

FIG. 11 is a diagram for explaining a table of an ink color separation table unit.

FIG. 12 is a flowchart illustrating a basic configuration of an ink color separation table creating unit.

FIG. 13 is a diagram for describing six tetrahedrons obtained by dividing an input cube.

FIG. 14 is a flowchart for explaining step S3-4 in detail.

FIG. 15 is a diagram illustrating ink amount contour lines as a result of internal interpolation in a case where a change curve of ink amounts on three sides of a triangle is illustrated.

FIG. 16 is a flowchart for explaining step S5-3.

FIG. 17 is a flowchart illustrating step S7-4.

18 is a diagram for explaining the specific contents of a non-linear approximation step of the ink amount contour line in FIG. 7;

FIG. 19 is a diagram for explaining an approximate curve when the value of a is changed in step S9-1.

FIG. 20 is a diagram for describing contour line generation of a target triangle when the maximum values of three sides are the same.

FIG. 21 is a diagram for explaining contour line generation of a target triangle when the maximum value of two sides is the same and the maximum value of one side is 0;

FIG. 22 is a diagram for explaining contour generation of a target triangle when the maximum values of two sides of the target triangle are the same and overlap one vertex.

23 is a diagram illustrating an example of interpolation within a triangle by vertices W-C-Bk in FIG. 2, where C, M,
A curve example of the ink amounts of Y and K is shown.

FIG. 24 shows C, M, Y, and K in the target triangle of FIG.
FIG. 3 is a diagram showing contour lines of respective inks.

FIG. 25 is a diagram for explaining division of an input cube into eight tetrahedrons when red or green color inks other than CMYK are used.

FIG. 26 is a diagram for explaining a conventional color printer calibration technique.

Continued on the front page F-term (reference) 2C262 AA24 AA26 AB11 BA02 BA07 BA09 BC01 BC10 BC19 FA13 5B057 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CC01 CE11 CE18 5C077 LL19 MP08 PP15 PP32 PP33 PP36 PP37 PP44 PP45 5C079 HB01 HB02 MA MA10 NA03 NA29 PA03

Claims (6)

[Claims] 1. An image processing method for calibrating a table for converting an input color component signal into a color component signal corresponding to a color material color used in a color output device, the image processing method comprising: Is output by the color output device, and from the patch measurement data obtained by measuring the output patch, a tone correction table corresponding to the first, second, and tertiary colors of the color material colors is calibrated. And defining a plurality of first lines from white to a primary color and a secondary color in a color solid represented by a plurality of color components indicating the input color component signal, based on the gradation correction table; A plurality of second lines from the primary color and the secondary color to black in the color solid are defined based on the tone correction table, and a white line in the color solid is defined based on the tone correction table. Defining a third line to black from the first, the image processing method characterized by creating the table from the second and third lines. 2. An initial correction gradation table for the secondary and tertiary colors is created based on a gradation correction table corresponding to a primary color of the color material color. An image processing method, wherein the color output device outputs patches corresponding to the secondary and tertiary colors using an initial corrected gradation table. 3. The image processing method according to claim 2, wherein an inking point on the second line and the third line can be controlled. 4. A color material color used in the color output device,
The image processing method according to claim 1, wherein the secondary colors are cyan, magenta, yellow, and black color material colors, and the secondary color is a mixed color of cyan and magenta, magenta and yellow, and yellow and cyan. 5. An image processing apparatus for calibrating a table for converting an input color component signal into a color component signal corresponding to a color material color used in a color output device, comprising: Means for outputting a patch corresponding to the color output device by the color output device; and a tone correction table corresponding to the first, second, and tertiary colors of the color material colors from patch measurement data obtained by measuring the output patch. And a plurality of first lines from white to a primary color and a secondary color in a color solid indicated by a plurality of color components indicating the input color component signal are defined based on the gradation correction table. Means for defining a plurality of second lines from the primary color and the secondary color to black in the color solid based on the gradation correction table; An image comprising: means for defining a third line from white to black in the color solid; and means for creating the table from the first, second, and third lines. Processing equipment. 6. A recording medium for recording a program for implementing an image processing method for calibrating a table for converting an input color component signal into a color component signal corresponding to a color material color used in a color output device, The patches corresponding to the color material colors 1, 2, and 3 are output by the color output device. Based on the patch measurement data obtained by measuring the output patches, the color material colors 1, 2, and 3 are output. Calibrating a gradation correction table corresponding to the next color, and converting a plurality of white to primary colors and secondary colors in a color solid indicated by a plurality of color components indicating the input color component signal based on the gradation correction table. And defining a plurality of second lines from the primary color and the secondary color to black in the color solid based on the gradation correction table. A program for defining a third line from white to black in the color solid based on a table, and recording a program for creating the table from the first, second, and third lines. Medium.