JPH08320922A - Color adjusting device - Google Patents

Abstract

PURPOSE: To provide a color adjusting device capable of shortening the time up to the start of interpolating processing. CONSTITUTION: Each of interpolating processors 11C, 11M, 11K selects a reference table corresponding to a color adjusting parameter set up at the time of color adjustment from plural color-adjusted reference tables calculated and prepared in each of color adjustment parameters at the time of color adjustment and stored in a reference table storing memory 10 and executes interpolating processing based upon the selected reference table.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color adjusting device used for color adjustment in a color printer, a color copying machine, a color scanner or the like.

[0002]

2. Description of the Related Art In recent years, the performance of hard copy has made remarkable progress, and high-fidelity color reproduction comparable to color photography and color printing is being obtained. As the fidelity increases in this way, the color reproduction problem is about to develop from the mere pursuit of fidelity to “preferred color reproduction”. That is, in addition to the color correction function that is indispensable for color reproduction of hard copy, in the future, a color adjustment function and the like for matching the desired color tone by the user will be required.

A conventional color adjustment procedure for a color image will be described below. FIG. 10 shows the configuration of a conventional color adjusting device for performing this color adjustment. First, R (red) G (green) B (blue)
Is the perceptual color space from the RGB system of the three primary color separation values of L ^* u
Convert to ^* v ^* system (where ^* represents a vector).
The RGB system is converted into color tristimulus values X, Y, and Z, and further converted into the L ^* u ^* v ^* system. Corresponding to the color space conversion means 1, respective conversion formulas are shown in formula 1 and formula 2.

[0004]

[Equation 1]

[0005]

[Equation 2]

Next, from the L ^* u ^* v ^* system to the polar coordinates in the L ^* u ^* v ^* coordinate system (Huv ° (hue angle), L ^* (luminance), Cuv ^* (saturation)) system (here Then, ° represents an angle). Corresponding to the inner polar coordinate conversion means 2, the conversion formula is shown in formula 3.

[0007]

(Equation 3)

FIG. 11 shows the L ^* u ^* v ^* coordinate system. (H
The uv °, L ^* , Cuv ^* ) coordinate system is polar coordinates of the L ^* u ^* v ^* coordinate system, and the hue adjustment is D for the hue angle Huv °.
Hue rotation of H °, saturation Cuv ^* expands / contracts K _c times, brightness L
^* Is made by expanding and contracting K _L times.

Corresponding to the selective color adjusting means 3 of FIG.
The conversion formula is shown in Formula 4.

[0010]

[Equation 4]

The obtained (Huv °) ', (L ^* )',
(Cuv ^* ) 'is inversely transformed from the L ^* u ^* v ^* coordinate system to the RGB system via the XYZ system. A conversion equation is shown in Equation 5 corresponding to the inverse color space conversion unit 4.

[0012]

(Equation 5)

In this way, color-adjusted values are obtained. Also, to output to a color printer or the like, RG
A conversion means 5 for converting from the B system to the printing four primary colors C (cyan) M (magenta) Y (yellow) K (black) system is also added. As described above, in the color adjustment, the calculation is complicated as shown in Expressions 1 to 5.

In order to improve this, JP-A-53-123
As shown in Japanese Patent Publication No. 201-201, complicated conversion from three input signals to one output signal is performed by an interpolation method using a lookup table.

In this interpolation method, as shown in FIG. 12, the values of grid points of a large cube having the values of the input signals RGB as orthogonal axes are stored in advance, and the large cube is converted into a unit cube including the grid points. The unit cube ABCDEFGH containing the converted signal to be divided is cut out, and the converted signal is obtained by performing interpolation processing on the data of the lattice points.

By performing the above-mentioned color adjustment based on the interpolation method using the reference table, the calculation can be simplified. The reference table is a value R ′, which is obtained by performing the calculations of Expressions 1 to 5 on the above-mentioned grid point data RGB.
It is obtained by setting G'and B'into each table. By performing the interpolation using the reference table having the color adjusted values, the color adjusting process can be simplified and speeded up.

[0017]

However, in the conventional color adjusting apparatus as described above, when the color adjusting parameter is changed when the color adjusting is performed, the color adjusting parameter is changed every time the color adjusting parameter is changed. There is a problem that it is necessary to recalculate the reference table corresponding to the parameter, and it takes a lot of time until the interpolation process is started.

The present invention solves the above-mentioned problems, and a reference table corresponding to any color adjustment parameter is calculated without calculating a reference table for interpolation processing each time the color adjustment parameter is changed. Can get
An object of the present invention is to provide a color adjustment device that can reduce the time until the interpolation process is started.

[0019]

In order to achieve the above object, a color adjusting apparatus of the present invention is a color adjusting apparatus for performing color adjustment by interpolating a color image signal using data of a reference table. A plurality of reference tables created in advance for each color adjustment parameter when performing adjustment, and a reference table corresponding to the color adjustment parameter based on the color adjustment parameter from the plurality of reference tables Is selected, and an interpolation processing means for performing the interpolation processing according to the reference table is selected.

[0020]

According to the above-mentioned structure, the interpolation processing means is configured in advance.
Select a reference table corresponding to the color adjustment parameter set when performing color adjustment from the multiple reference tables that have been adjusted for color adjustment and are created for each color adjustment parameter when performing color adjustment. Interpolation processing is performed using a table.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color adjusting apparatus according to an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an overall configuration of an image processing apparatus using the color adjusting apparatus of this embodiment. In FIG. 1, reference numeral 6 is a color image signal input unit such as a color scanner for reading RGB three primary color separation values from a color original or the like. Reference numeral 7 denotes a color adjustment signal output unit, which is input from the situation of the color image according to the user's preference or is determined from the characteristics of the device in order to bring the image read by the color scanner or the like closer to the original image. Reference numeral 8 denotes a color adjusting device of this embodiment that receives a color adjusting signal from the color adjusting signal output unit 7 and performs color adjustment. Reference numeral 9 denotes a color image output unit such as a color display or a color printer that outputs a color-adjusted color image signal.

FIG. 2 shows a block diagram of the color adjusting device 8 of this embodiment. In the color adjusting device 8 of FIG. 2, reference numeral 10 is a reference table storage memory composed of a ROM or the like for storing a plurality of reference tables and outputting the values. When calculating the plurality of reference tables, the range of the amount of change and the number of divisions of the rotation angle DH of an appropriate hue angle, the expansion / contraction ratio K _{C of} saturation and the expansion / contraction ratio K _L of luminance are adjusted as color adjustments. decided. The rotation angle DH of the hue angle divides the range of -15 ° to 15 ° into 9 steps, and the expansion / contraction ratio K _{C of the} saturation divides the range of 0.625 to 1.6 into 7 steps to obtain the expansion / contraction ratio of luminance. K _L is from 0.625
The range of 1.6 was divided into 7 steps.

As a method of each division, as shown in equation 6, the hue angle is determined by ΔH, the saturation is determined by the saturation ratio α, and the luminance is determined by the luminance ratio β. The rotation angle DH of the hue angle is -15.00,-
11.25, -7.50, -3.75, 0.00, 3.
75, 7.50, 11.25, 15.00, and 0.62 as the expansion and contraction ratios K _C and K _L for saturation and luminance.
5, 0.73, 0.855, 1.0, 1.17, 1.3
It is 7,1.6. Also, ΔH = 3.75, α = β =
It was set to 1.17.

[0025]

(Equation 6)

The reference table for color adjustment is 9 × 7.
× 7 = 441, which is stored in the reference table storage memory 10. As shown in FIG. 2, one reference table (for example, LUT1) stored in the reference table storage memory 10 is composed of C, M, Y, and K reference tables in this order.

11C, 11M, 11Y and 11K are
This is an interpolation processing device as an interpolation processing unit that reads a reference table from the reference table storage memory 10 and performs an interpolation process using the reference table.

Color adjustment constructed as shown in FIGS. 1 and 2.
The operation of the device 8 will be described below. First, the color
Refer to the color adjustment signal output from the adjustment signal output unit 7.
A lighting table is selected. For example, the hue that is the selection signal
Angle rotation angle DH, saturation expansion / contraction K _C , Brightness expansion / contraction
Rate K_L Are 1 step, 1 step, 1 step,
The reference table is stored in the reference table storage table shown in FIG.
The LUT1 in the memory 10 is output.

Reference tables LUT1, LUT2, LU
Each of T3, LUT4, ... Is further configured in the order of reference tables C, M, Y, K, and the values of the reference tables C, M, Y, K correspond to the interpolation processing devices 11C, 11C, respectively. It is read into 11M, 11Y, and 11K. The RGB signals detected and output by the color image signal input unit 6 are read into the respective interpolation processing devices 11C, 11M, 11Y, 11K, subjected to interpolation processing using the reference tables C, M, Y, K, and after color adjustment. A CMYK signal is obtained, and this CMY
The K signal is output to the color image output unit 9.

Incidentally, the interpolation processing devices 11C, 11M, 1 used in the interpolation processing by the above table interpolation method.
A more detailed configuration diagram of 1Y and 11K is shown in FIG. 5, and the description thereof will be described later.

FIG. 3 shows the principle of the tetrahedral division of the table interpolation method used in the color adjusting apparatus of this embodiment. Here, two cubes ABCDEFGH and EFGHIJ
KL are overlapped, and the basic lattice points E of those cubes,
Finally, four tetrahedrons EHQP, EFQP, FGQP, GH are used by using H, F, G and respective body-centered lattice points Q, P.
A method of dividing into QPs is shown. As is clear from FIG. 3, each tetrahedron is composed of two basic lattice points and two body-centered lattice points.

In FIG. 3, 8 obtained from the adjacent unit cube EFGHIJKL on the unit cube ABCDEFGH.
Although we considered the tetrahedron EFGHQP, as shown in FIG.
HQP, ADHESP, BCGFPT, ABFEUP,
CDHGVP exists, and each octahedron is divided into four, totaling 24 tetrahedra ABRP, CBRP, CDR
P, ADRP, FEQP, FGQP, HGQP, HEQ
P, ADSP, HDSP, HESP, AESP, CBT
P, CGTP, FGTP, FBTP, ABUP, FBU
P, FEUP, AEUP, CDVP, CGVP, HGV
P and HDVP exist.

Any two points A, B, C, D, E, F, G and H in the unit cube ABCDEFGH are 24 points.
It belongs to any of the tetrahedra. In this division method, the size of the tetrahedron is small (volume of 1/12 of the unit cube), and the size and shape are all the same.
The accuracy of the converted signal is good, and the accuracy does not vary from region to region.

FIG. 5 is a block diagram of an interpolation processing device used in the color adjusting device of this embodiment. The operation of the interpolation processing devices 11C, 11M, 11Y and 11K will be described below based on the configuration diagram shown in FIG.

First, three 8-bit input signals R, G,
B is divided into upper 4-bit signals R ', G', B'and lower 4-bit signals r, g, b, respectively, and the lower 4-bit signals r, g, b are input to the tetrahedral determining means 12, and the upper 4 The bit signals R ′, G ′, B ′ are input to the address generating means 13. Here, for convenience of description, the input signals R, G, and B are fixed-point numerical values, the upper 4 bits are the integer part, and the lower 4 bits are the decimal part.

The tetrahedron judging means 12 judges which tetrahedron of the 24 tetrahedrons the point to be found in the unit cube belongs to, and the lower 4 bit signals r and g shown in Table 1 are shown. , B, six relational expressions g−r, g + r−1, b
-R, b + r-1, b-g, and b + g-1 are determined by whether they are positive (+) or negative (-), and the determination result is used as a 5-bit tetrahedron determination signal TE and the lower 4 It outputs together with the bit signals r, g, and b. However, when the value of each relational expression is 0, it may be either positive (+) or negative (-), but here it is assumed to be positive (+).

The address generating means 13 receives the input signals R,
The table address corresponding to the coordinates of each point of the four tetrahedrons is output based on the upper 4 bit signals R ′, G ′, B ′ of G and B and the tetrahedron determination signal TE. The four grid point addresses of the tetrahedron are the two basic grid point addresses AD0,
It is composed of AD1 and two body-centered lattice point addresses AD2 and AD3, and corresponds to the lattice point address shown in Table 2 according to the tetrahedral determination signal TE. The grid point address is the input signal R,
It is composed of the values R ″, G ″, B ″ generated by the operation shown in Table 3 based on the upper 4 bits R ′, G ′, B ′ of G, B.

By the above-described processing, the basic grid point addresses AD0, AD1 and the body-centered grid point addresses AD2, AD
3 are generated and input to the two basic lattice point data storage means 14 and the two body-centered lattice point data storage means 15, respectively.

Each of the reference tables C, M, Y and K constituting each of the reference tables LUT1 ... Is a series of tables of the data of the basic lattice points and the data of the body-centered lattice points. The values of the reference table are input to the semiconductor memory, and as shown in FIG. 6, the address signals AD0, AD1,
When AD2 and AD3 are input, the data DA0, DA1, DA2 and DA3 corresponding to the address are read.

The data of the basic lattice point data storage means 14 and the body-centered lattice point data storage means 15 are stored in accordance with the address.
Data of the lattice points shown in FIG. 7 are stored. The basic grid point addresses AD0 and AD1 correspond to the coordinates of the basic grid point as they are, but the body-centered grid point addresses AD2 and AD3 are values obtained by adding 0.5 to the coordinates R, G and B of the body-centered grid points. . Output signals DA0, DA1, DA2 from the basic lattice point data storage means 14 and the body-centered lattice point data storage means 15,
DA3 is the value of each vertex of the tetrahedron and is sent to the interpolation means 17.

The weighting factor calculating means 16 is
Tetrahedral decision signal TE from tetrahedral decision means 12 and lower 4
Four weighting factors W based on the bit signals r, g, b
H0, WH1, WH2, and WH3 are obtained and output to the interpolation means 17.

The interpolation means 17 includes vertex data DA0, DA1, DA2, DA3 from the two basic lattice point data storage means 14 and the two body-centered lattice point data storage means 15, and
The weighting factors WH0, WH1, from the weighting factor calculating means 16
The sum of products operation with WH2 and WH3 is performed.

FIG. 8 shows the construction of the interpolating means 17. The data of each vertex and the weighting coefficient are calculated by four multipliers 18, and the products are summed by an adder 19 to add the inside of the tetrahedron. Data is interpolated to obtain converted signals C, M, Y, K
Is output.

FIG. 9 is a block diagram showing the procedure for creating the reference table. The CIE1976L ^* u ^* v ^* system is used as the perceptual color space used for color adjustment in the color adjustment apparatus of this embodiment.

Lookup table shown in the block diagram of FIG.
The procedure for creating is explained. In FIG. 9, step # 20
The grid point data of the reference table used for RGB interpolation processing in
Enter the data and L is entered in step # 21.^* u^* v^* Convert to system
And then L ^* u^* v^* The inner polar coordinate system of the system (Hu
v^* , L^* , Cuv^* ) System, and in step # 22
Hue angle rotation angle DH, saturation expansion / contraction ratio K_C , Brightness scaling factor
K_L Color adjustment by (Huv^* , L^* ,
Cuv^* ) L in step # 23^* u^* v^* Back to system
In step # 24, the primary color system is changed to the RGB system.
Inverse conversion is performed to obtain a look-up table for each signal. Up
In the creation procedure described above, a series of calculations of Expression 1 to Expression 5 are performed.
It

In this way, one reference table is obtained for a set of color adjustment parameters: hue angle rotation angle DH, saturation expansion / contraction ratio K _C , and brightness expansion / contraction ratio K _L.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

[0050]

[Table 4]

[0051]

As described above, according to the present invention, the interpolation processing means performs color adjustment from a plurality of color-adjusted reference tables created by calculating in advance for each color adjustment parameter when performing color adjustment. It is possible to select a reference table corresponding to the color adjustment parameter set when performing, and use this reference table to perform interpolation processing.

Therefore, it is possible to obtain a reference table corresponding to any color adjustment parameter without calculating the reference table for the interpolation processing each time the color adjustment parameter is changed, and to start the interpolation processing. The time can be shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image processing apparatus using a color adjusting apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a color adjusting apparatus according to an embodiment of the present invention.

FIG. 3 is a principle diagram of table interpolation tetrahedron division in the embodiment.

FIG. 4 is an explanatory diagram of division of 24 tetrahedrons of the table interpolation method in the embodiment.

FIG. 5 is a block diagram of an interpolation processing device in the same embodiment.

FIG. 6 is an explanatory diagram of grid point data of a table interpolation method in the embodiment.

FIG. 7 is a table-interpolating tetrahedron A according to the embodiment.
Illustration of BRP

FIG. 8 is a block diagram of an interpolation means in the same embodiment.

FIG. 9 is a block diagram showing a procedure for creating a reference table in the embodiment.

FIG. 10 is a block diagram showing a color adjustment procedure in a conventional color adjustment device.

FIG. 11 is an explanatory diagram of a coordinate system of a perceptual color space.

FIG. 12 is a principle diagram of an interpolation method using a reference table.

[Explanation of symbols]

 10 Reference Table Storage Memory 11C, 11M, 11Y, 11K Interpolation Processing Device

Claims (2)

[Claims] 1. In a color adjusting device for performing color adjustment by interpolating a color image signal using data of a reference table, a reference table created in advance corresponding to each color adjustment parameter when performing the color adjustment. A plurality of reference tables, and based on the color adjustment parameters, a reference table corresponding to the color adjustment parameters is selected from the plurality of reference tables, and the interpolation processing is performed by the reference table. Color adjustment device. 2. The color adjusting apparatus according to claim 1, wherein the reference table is constituted by data in which the lightness, the saturation, and the hue are independently adjusted in a color appearance space including the lightness, the saturation, and the hue.