JPH04196678A - Method of estimating color - Google Patents

Abstract

PURPOSE:To obtain balance of saturation in an excellent way by deviating a hue of a peak of each color of an input side color cube in a direction of a peak of a color corresponding to an output side color cube in the case of compressing the saturation of the input side color cube. CONSTITUTION:The L* among a representing color system is converted in response to a spread ratio of the lightness on an achromatic color axis of an input side color cube and an output side color cube in relation to the direction of the lightness, the lightness of the input side color cube is compressed and mapped. In relation to the saturation direction, no conversion is implemented in the middle at a part where the color reproduction range of the input side color cube and the output side color cube and u*, v* or a*, b* among the value of the representing color system are converted in response to the spread of the saturation of the two color cubes at the circumference part and the saturation of the input side color cube is expanded and mapped. Moreover, when the saturation of the input side color cube is expanded and mapped, the hue of the peak of each color of the input side color cube is deviated in a direction of the color peak corresponding to the output side color cube. The color reproduction has a range of sufficient lightness and saturation and the entire saturation is well balanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This invention relates to color estimation suitable for application to a color separation image correction device used, for example, when reproducing a color image of a color hard copy into a color television image. Regarding the method.

[Background of the Invention] When reproducing a color image of a cocolor hard copy into a color television image, each color system is different. That is, television images are constructed using the additive color method, and the color system is R, G.

The B color system is used. On the other hand, in a hard copy, a color image is constructed by a subtractive color method, and the Y, M, C coordinate system, for example, is used as the color system. In such a case, image data conversion, that is, color correction, is performed using these color systems.

For example, when reproducing a color image of a color hard copy into a color television image, image data of yellow Y, magenta M, and cyan C is supplied to the color separation image correction device 200, as shown in No. 21511, and the correction device 20
i# image data (color correction data) of red R7 green G and blue B is output from 0, and this color correction data is supplied to the television display 100.

Here, it is conceivable to use a method of referring to a lookup table as a method of obtaining color correction data from Y, M, and C image data. As a method for obtaining color correction data to be stored in this lookup table, a method as described in, for example, Japanese Unexamined Patent Publication No. 63-254864 has been proposed.

That is, a color patch based on each combination of Y, M, and C image data is output and measured to determine the value of the color system, and a color patch based on each combination of R, G, and B image data is output on a color TV. Measure the color by displaying it on the display to find the value of the color system. Then, for each combination of Y, M, and C image data, the color of the color hard copy for each combination of Y, M, and C image data is calculated using the values of the color system obtained by colorimetrically measuring the color patches on the color television display. R to obtain a color system value that is the same as or close to the color system value obtained by colorimetrically measuring the patch;
G.

The image data of B is obtained by interpolation calculation.

[Problem to be solved by the invention] By the way, in general, the R, G,
The color reproduction range based on the B image data is wider than the color reproduction range based on the Y, M, and C image data of the color hard copy.

Therefore, as mentioned above, the values of the color system obtained for the image data of Y, M, and C can be expressed as
According to the method that calculates the R, G, and B image data in correspondence with the values of the color system for the G and B image data,
Only a narrow range of colors exists within the color reproduction range of R, G, and B image data, and the range of brightness and saturation is narrow, making it impossible to reproduce colors with low brightness (high density) or colors with high saturation. This had the disadvantage that images lacked contrast and shadows.

In order to eliminate such inconvenience, Y, M.

By expanding the color reproduction range based on C and K image data, R,
It is necessary to approximate the color reproduction range of G and B image data. In this case, if the brightness is expanded to match the maximum and minimum brightness values, and then the saturation is moved to the high saturation side using a hue-constant method, the amount of movement will be determined according to the outer shape of the color solid, There was a problem in that the balance of saturation between each hue shifted after the movement.

For example, assume that the solid line a in FIG. 22 is the color reproduction range of a television display, and the solid line @b in the figure is the color reproduction range of a hard copy. A value C1 in the hard copy color reproduction range,
C2 is the value CI' of the color reproduction range of the television display,
When moved to C2', the difference in saturation between C1' and C2' becomes larger than the difference in saturation between C1 and C2, and the balance of saturation is disrupted after the movement.

Furthermore, when reproducing a color hard copy consisting of the three primary colors Y, M, and C into a color television image consisting of the three primary colors R, G, and B, the color hard copy consists of R,
Among the 6 colors of G, B, Y, M, and C, Y,
M.

The saturation of the three C colors tends to be high, whereas color TV images have R, G, B, Y, and M colors.

Among the six colors of C, the saturation of three colors, R, G, and B, tends to be higher. Therefore, for example, if a highly saturated color such as C in printing is moved within the color reproduction range of a television image with a constant hue, the increase in saturation will be reduced. As described above, there is a problem in that the amount of increase in saturation is small for the highly saturated colors of the hard copy, and the overall saturation balance between colors is shifted after movement.

Therefore, an object of the present invention is to enable good reproduction of brightness and saturation without shifting the balance of saturation between colors when reproducing a color hard copy as a color television image. It is something.

[Means for Solving the Problems] In the color estimation method according to the first invention, a value of a color system for each combination of a plurality of input color separation image information is determined, and a value of a color system for each combination of a plurality of output color separation image information is determined. Find the value of the color system for.

As a color system, an L"u" v book color system or an L"a book color system is used.

Then, LX of the color system values obtained for any combination of input color separation image information is input as an input consisting of color system values obtained for each combination of input color separation image information. The achromatic color axis of the output side color solid consists of the difference between the maximum and minimum brightness values on the achromatic color axis of the side color solid and the values of the color system obtained for each combination of output color separation image information. Convert according to the ratio of the difference between the maximum and minimum brightness values above.

Among the values of the color system obtained for any combination of input color separation image information, U*, v plant height, or a-b* are expressed as chroma at the hue and brightness of the input color solid at that time. a times the maximum saturation value (if smaller than a<1.0>, do not convert; if the saturation is more than a times the maximum saturation value at the hue and lightness of the input side color solid) , the inner surface of the input side color solid is composed of a times the maximum saturation value of each hue and lightness of the input side color solid, and the input side color is composed of the maximum saturation value of each hue and brightness of the input side color solid. The part surrounded by the outer surface of the solid is continuous, whereas the entire part surrounded by the inner surface of the input color solid and the outer surface of the output color solid, which is composed of the maximum saturation values of each hue and brightness of the output color solid, is continuous. Convert it so that it corresponds to

As a method for this correspondence, when the saturation increases, the hue determined from an arbitrary combination of input color separation image information is determined by the blue, green, and red of each color in the input color solid.

When entering a predetermined range before and after the hue of any of the six maximum chroma points of yellow, magenta, and cyan, the direction of the hue of the maximum chroma point of the color of the output color solid that is the same as the color corresponding to that hue. Decide to shift the hue.

Then, using the value of the color system obtained for each combination of the plurality of output color separation II image information, the same value as the above-converted color system value for any combination of input color separation image information is obtained. Find a combination of output color separation image information to obtain .

Furthermore, when the three primary colors of the input color separation image information and the three primary colors of the output color separation image information are different, according to the color estimation method according to the second invention, the color estimation method for each combination of the plurality of input color separation image information The values of the color system are determined, and the values of the color system for each combination of the plurality of output color separation image information are determined.

As a color system L * u * y * color system or L'
Use the a car b* color system.

Then, among the color system values obtained for any combination of input color separation image information, Lm is inputted from the color system values obtained for each combination of input color separation image information. The achromatic color axis of the output side color solid is composed of the difference between the maximum and minimum brightness values on the achromatic color axis of the side color solid and the values of the color system obtained for each combination of output color separation WigIA information. Convert according to the ratio of the difference between the maximum and minimum brightness values above.

Among the values of the color system obtained for any combination of input color separation image information, U*, V car or akyo, b car are 5
If the saturation is smaller than a times (a<1.0) the maximum saturation value at the current hue and lightness of the input color solid, no conversion is performed,
If the saturation is more than a times the maximum saturation value at the current hue and lightness of the input color solid, each hue of the input color solid,
In the part surrounded by the inner surface of the input color solid, which is composed of a times the maximum chroma value in lightness, and the outer surface of the input color solid, which is composed of each hue of the input color solid, and the maximum chroma value in lightness. On the other hand, the entire portion surrounded by the inner surface of the input color solid and the outer surface of the output color solid formed by the maximum saturation values of each hue and lightness of the output color solid is converted so as to correspond continuously.

As a method for this correspondence, when the saturation increases, the hue determined from any combination of input color separation image information is set within a predetermined range before and after any of the hues at the maximum saturation point of the 31 [colors] in the input color solid. When entering the output color solid, the hue is determined to be shifted in either direction of two of the hues at the maximum saturation points of the three primary colors in the output side color solid that are located before and after on the hue wheel.

Then, using the values of the color system obtained for each combination of the plurality of output color separation image information, the input color separation image information is calculated. A combination of output color separation image information that yields the same value as the value of the converted color system for the combination of is determined.

[Function] In the first invention method, in the lightness direction, each combination of input color separation image information is adjusted according to the ratio of the spread of lightness on the achromatic color axis of the input side color solid and the output side color solid. Among the values of the color system obtained for this, Lm is converted, and the brightness of the input color solid is enlarged and mapped. ′ Regarding the saturation direction, the central part of the overlap between the color reproduction ranges of the input color solid and the output color solid is not converted, and the input color separation is performed in the peripheral part according to the spread of the saturation of the two color solids. Among the values of the color system obtained for each combination of image information, the U-car, V-car, or a-kyo, b-car are converted, and the saturation of the input side color solid is enlarged and mapped.

Further, when the saturation of the input color solid is enlarged and mapped, the hue is shifted so that the peak of each color in the input color solid is shifted in the direction of the peak of the corresponding color in the output color solid.

As a result, the color reproduction range on the input side approaches the color reproduction range on the output side while balancing the overall saturation through natural conversion, and the color reproduction based on the required output color separation image information has sufficient brightness and saturation. , and the overall color saturation is well-balanced.

In the second invention method, when the three primary colors of the input color separation image information, for example, Y, M, C, and the three primary colors of the output color separation image information, for example, R, G, B, are different, the input side color solid is When the saturation of is enlarged and mapped, the peaks of the three primary colors of the input color solid are shifted in the direction of the peaks of the three primary colors of the output color solid.

Although this causes a shift in hue, the overall saturation is balanced.

[Example] Hereinafter, as an example of the present invention, Y for color printing,
A case of obtaining R, G, B image data of a color television display corresponding to M, C, K image data will be explained with reference to the drawings. Here, Y, M, C, K, R, It is assumed that both G and B image data are 8 bits and take values from 0 to 255.

FIG. 1 shows a color separation image correction apparatus which obtains R, G, and B image data corresponding to Y, M, C, and K image data.

In the figure, image data (print data) for yellow Y, magenta M, cyan C, and ink are supplied to lookup tables 211 to 213 constituting the first color conversion means, and are supplied to yellow Y', magenta M' , cyan C' image data (compressed print data).

Further, the compressed print data Y', M', and C' are supplied to a color masking device 220 and converted into red R1 green G and blue B image data (display data).

Lookup tables 211 to 213 (store compressed print data Y', M', and C', respectively, and print data (Y and K), (M and K), and (C and K) respectively. Print data Y', M', and C' are referenced.

The image data of Y', M', and C' are created by the following method.

■First, color patches are measured for each combination using 8-bit Y', M", and C' Iil data, and x,
Find the values of y and z color system, and then LX.

Find the values of u*, v in this color system.

In this case, for each of the image data of Y', M', and C', 0. 64. 128. 192. 5 of 255
Take two quantization levels and create color patches (5x5x5=125>) based on each combination of these (
(Illustrated in Figure 2).

Then, measure the color patch with a colorimeter, obtain the values of the x, y, z color system as shown below, and further calculate the LX,
Ll *, v Find the value of this color system.

At two points, interpolate the middle of 5X5X5=125 to obtain 9x
Make 9x9=729. Color measurement may be performed by printing a color batch of 9×9×9=729 colors, but the number of measurements increases and it takes time.

In this way, L number 1 u car, ■ car color system value is Y',
It is determined for 9X9X9=729 colors based on the image data of M' and C'.

These L*, u*, ■values of this color system are L car INI(Y', M', C')u"
IN 1 (Y', M', C'
) V car lN1(Y', M', C').

FIG. 3 shows these values in the present color system, which will hereinafter be referred to as the color solid of printed matter.

■Next, color batches of each combination of Y, M, C, and K image data are measured, and x, y,
Find the value of the z color system, and further calculate Lg, u car, v*
Find the value of the color system.

In this case, for equal amounts of Y, M, and C, 0.
64.5 quantization levels of 128, 192, 255 are taken, and K image data are also 0, 6 for each.
4,128. Create a color batch by taking 192,255 levels. In other words, as shown in Figure 4, 5X
5=25 color batches are created.

Then, colorimetrically measure this color batch in the same manner as in the process of ■, calculate the values of the x, y, and z color system, and then calculate the
*, u*, y* Calculate the values of the color system.

■Next, Y', M', In order to lower the minimum value of the L-substitution of the color solid C', the L-substitution is proportionally extended to the low Lm value side, and the values of Ll, u-car, and the car surface color system obtained in ■. Y′ corresponding to .

A combination of image data of M' and C' is calculated.

In other words, Lmu* calculated corresponding to each color combination of Y, M, C and K (5x5=25),
The value of the v* color system is given as the target value T', and the values of Y', M', and C' are determined by convergence calculation.

For the sake of simplicity, the description will be made assuming that there are two basic colors (for example, Y', M').

FIG. 5 shows the Y', M' coordinate system. When each lattice point is mapped to the L wheel, the U wheel, and the main color system by the above-mentioned processing (2), the result is as shown in FIG. 6. Vertices B, C, G, and F of the square in FIG. 5 correspond to vertices B', C', G', and F' in FIG. 6, respectively.

Figure 7 shows how L combinations of Y, M, C, and K (5x5=25) are created by processing (■).

■It is mapped to this color system.

First, the values of the Ll, u-car, and v* color systems for each combination of image data of Y, M, C, and K are given as target values T' (see FIGS. 60 and 7).

In this case, the target value T' is set at the lattice point a as shown in the 60th
When it is within the area surrounded by ' to d', the combination of Y' and M' (target value T) in the Y', M' coordinate system is surrounded by grid points a to d as shown in Figure 5. It is estimated that it is within the area.

The location of the target value T in the area formed by the grid points a % d is determined by performing a convergence calculation while associating the color system of FIG. 6 with the coordinate system of FIG. 5. The reason for performing convergence calculations in this way is that although the conversion from the coordinate system shown in Figure 5 to the color system shown in Figure 6 is already known, the reverse conversion is very complicated and there is still no good conversion. This is because the formula is not known.

It is determined in which region the target value T' is located among a plurality of regions formed by 81 lattice points (see FIG. 6).

When the target value T is in the area SO' as shown in FIG. 9, the target value T is in the area SO' corresponding to the area SO' as shown in FIG.
It is assumed that the

Next, the estimated area SO is equally divided into four areas 81 to S4. The five division points e~1 are calculated by weighted averaging using the surrounding grid points that have already been found. Then, the values corresponding to the dividing points e to t are L car, u*,
■ Plot the values when converted to the car color system on the color system shown in Figure 9, and choose which region among the four regions 81' to S4' formed by the plotted division points e' to i'. Determine whether there is a target value T'. As shown in Figure 9, area S
2', it is estimated that the target value T is in a region S2 corresponding to the region S2', as shown in FIG.

Next, the estimated region S2 is equally divided into four regions 85 to S8 at 5 division points, which are calculated by weighted averaging using the surrounding grid points and division points that have already been found. . Then, the value corresponding to this dividing point j - n is plotted in the color system shown in Fig. 9, and the value obtained when converted to the u-ywI-color system is plotted, and the divided point j is calculated by 70.
4 regions S5' to S8' formed by ' to n'
It is determined in which region the target value T' is located. When the target value T is in the region 88' as shown in FIG. 9, it is estimated that the target value T is in the region S8 corresponding to the region 88' as shown in FIG.

Next, the estimated region S8 is equally divided into four regions 89 to S12. The five division points 0 to S are calculated by weighted averaging using the surrounding grid points and division points that have already been determined. Then, calculate the values corresponding to the division points 0 to S,
, v Plot the values when converted to the color system in the color system shown in Fig. 9, and determine which region among the four regions S9' to S12' formed by the plotted division points 0' to S'. Determine whether there is a target value T'. When the target value T is in the region 810' as shown in FIG. 9, it is estimated that the target value T is in the region SIO corresponding to the region 810' as shown in FIG.

By repeating such region division, the grid becomes gradually smaller and finally converges. Then, by averaging the four lattice points or division points forming the converged area, a combination of basic colors that will give the target value T is determined.

Using the values of Y', M', and C' for the combination of Y, M, and C equivalents and K obtained as above, we can calculate Y' from Y and K, and M from M and K. Y, M, C by calculating C' from C and K.

Conversion from K to Y', M', and C' will be performed.

■As above, Y, M, C and K are 0.64
゜128,. Image data of Y', M', and C' are obtained for combinations of 192 and 255 quantization levels, and Y' corresponding to other quantization levels.

The image data of M' and C' are interpolated by interpolation processing.

That is, the interpolation process is performed based on data of four grid points including the point to be interpolated. In this interpolation process, as shown in FIG.
When given, take the weighted average of the four grid points surrounding it1.For example, if it is 0 point, grid points e, f
, g, and h by the weighting coefficient to obtain U
Find the point.

The above interpolation processing is performed for each point at a quantization level of 0 to 255 including the grid points, and input (Y.

For all points in K), the corresponding image data of Y' is calculated.

M corresponding to all points of input (M, K), (C, K)
' and C' are calculated in the same way.

Y′ obtained by the above processing of ① to ②.

The image data of M' and C' are stored in lookup tables 211, 212 and 213, respectively, and (
Y, K), (M, K) and (C, K), respectively.

Furthermore, in the color masking device 220 in FIG.
, G, and B by providing a lookup table. In other words, this lookup table contains image data R and G.

B is stored, and display data R, G, and B are referenced by compressed print data Y', M', and C'.

This R, G, and B image data is created by the following method.

■First, color patches based on each combination of R, a, and B image data are displayed on a TV display and measured, and the values of the x, y, and z color systems are determined, and then L*
, U East, ■ Find the value of the East table color system.

In this case, for each of R, G, and B image data, 0. 64. 128. 192. 255, five quantization levels are taken, and the colors resulting from each combination of these (5x 5x 5 = 125 > are displayed one by one on a TV display, and each color is measured using a spectroradiometer, and the following is done. The values of the X, Y, and Z color systems are determined as follows, and the values of LX, u*, and the 78 color system are also determined.

In this formula, Xn, Yn, and Zn are x of standard light D65,
These are the values of x, y, and z such that y. X.

The relationship between y, x, y, and z is as follows.

x=X/ (X+Y+Z)y=Y/ (X+Y+Z)D
The value of 65 is: X=0. 3127, y=0.329
Since it is 0, Xn, Yn, and Zn satisfy the following formula.

Xn/(Xn+Yn+Zn)=0. 312
7Yn/(Xn+Yn+Zn)=0. 32
90 The absolute value levels of Xn, Yn, and Zn must be determined, but in order to match the levels of the measured values of x, y, and z, white < R = G = B = 255).
Yn is made approximately equal to Y of the x, y, and z values when displayed.

In addition, by interpolating the middle of 5X5X5=125, it becomes 9x9
Set x9=729. Although 9X9X9=729 colors may be displayed and measured, the number of measurements increases and it takes time.

In this way, the value of 1-*, u5 78 color system becomes R
, G, B for 9X9X9=729 colors. Let the values of the L car, u', and v car color systems be 5 L car TV [R, G, B) U car TV (R, G, B) V main TV (R, G, B). FIG. 11 shows the values of L*, U*, and ■this color system, which will hereinafter be referred to as the color solid of a television display.

0 Next, the maximum and minimum values of LX are determined from the color solid values of the printed matter.

In this case, among 9X9X9=729 colors, a combination with the maximum number of L cars and a combination with the minimum number of L cars are found, and the L numbers at that time are determined.

"Maximum value"Y' = M' = C' = O is the value of L values for the white background, and it is assumed that L car INI ax.

"Minimum value" is the value of LX when black is printed with Y' = M' = C' = 255, and is defined as L '' lN1m1n.

(2) Next, find the maximum and minimum values of the L car from the color solid values on the television display.

In this case, among 9X9X9=729 colors, a combination with the maximum number of L cars and a combination with the minimum number of L cars are determined, and Lm at that time is determined.

“Maximum value” This is the value of L when white is displayed with R=G-B=255, and is defined as L” TVmax.

"Minimum value" is the value of the L car when black is displayed with R=G=B=0,
Let it be L car TV layer 1n.

0th order, the value of the color solid of the printed matter L” INI, u”
INl, v less INI to L car IN2. u East IN2
．． Convert to v'lN2.

That is, linear conversion is performed as shown in the following equation so that the maximum and minimum values of LX of the color solid of the printed matter become the maximum and minimum values of L of the color solid of the television display.

X (L book INI -L” lN1m1n) 10L
” TVmin Accordingly, the u car and y car are also converted as shown in the following formula.

(2) Next, display on the television display a gray scale chart in which LX is equally spaced.

In other words, 0*, V line = 0, L car is 20~1°O
A gray scale chart with a range of 5 quantization levels and an interval of 5 quantization levels is displayed (see FIG. 12).

In this case, L'TV (R.

G, B), u book TV (R, G, B),
v car TV (R,G.

B) is used to find the values of R, G, and B at each step of the gray stage chart by convergence calculation.

Since the convergence calculation is the same as that explained in FIGS. 5 to 9, the explanation will be omitted.

Then, a gray level chart is displayed on a television display from the R, G, and H image data obtained at each step as described above.

[Phase] Next, a printout of a gray stage chart with L pieces equally spaced is created.

Tsuieri, 0*, V book = 0, LX is 20 to 10
A gray step chart is created that has a range of 0 and an interval of 5 quantization levels (see FIG. 12).

In this case 5 Color solid data of printed matter L"1N2(Y'
, M', C'), u car lN2(Y',
M', C'>.

Using V book lN2(Y', M', C'), Y', at each step of the gray stage chart is calculated by convergence operation.
Find the values of M' and C'. Since the convergence calculation is the same as that explained in FIGS. 5 to 9, the explanation will be omitted.

Also, Y at each step determined as described above.
The image data of ', M', and C' are printed through a plate-making printing process to create a gray level chart.

Next, compare the gray stage chart on the TV display with the gray stage chart on the printed version, and check whether the boundaries of each step on the printed chart are the same as the chart on the TV display. However, if they are not the same, L* of the color solid of the printed matter is as follows.
, u*, v values of the original color system are converted.

x(L car IN2+gax-L *IN2+*in
) + L car IN2 here, change the value of constant γ, L"lN3. u"lN3. v book IN
Recalculate to 3 and change the operation of [stock] to L car IN2゜u”lN
2.Instead of V car IN2, use L”lN3.u car IN3゜v
” Apply lN3 and compare again with the chart on the TV display.

Then, repeat the above operations 0 and ■, and then print the book IN3. U car [N3. Let's use v*IN3 in the following operation.

0th order, R for each combination of Y', M', C',
Find the combination of G and B (color correction data).

That is, Y' and M' are obtained as described above.

The color of each combination of C' (32X32X32=3276
8) for L*, 0*, ■Value wheel IN3 of this color system.
u book [N3. v''lN3 is given as the target value T' to the color solid of the television display (shown in FIG. 11), and the values of R, G, and B for each combination of Y', M', and C' are determined by convergence calculation.

At this stage, the color reproduction range of the TV display is wider than that of printed matter, mainly in high-brightness areas, but conversely, the color reproduction range of printed matter is wider in some low-brightness areas. In some areas, there are some areas (see Figure 13).

Therefore, in low brightness areas, the target value T' may be outside the color reproduction range of the television display, and the target value T' is converted to be within the color reproduction range of the television display.

This conversion is performed as follows.

That is, the L car rN3. is sought for each combination of Y', M', and C'. Ukyo IN3. The value of vIN3 is applied to the color solid of the television display (shown in FIG. 11) as the target value T'. At this time, L book.

The values of car U and v are respectively L''T' and car T'
.

Let V ning T'. In addition, the saturation value determined by uT'+v' is r T', arctan (v ''T'
/ u book T') is θT', the maximum value of saturation of the color solid of the TV display at L'IN3, θT' is 8 times (a
ll, O), for example, about 2/3 times the saturation value rTV■
Let idT' be the threshold value (see FIG. 13).

If rT' is less than or equal to r TV * idT', do not convert, L"T" = L car T', U car T- = u grass T', V car T'' = v"T', rT #=rT', θ
Let T″=θT″.

However, when rT' is larger than rTV*idT', L pieces T''=L pieces T', θT''=θT', and rT' is set as shown in the following equation.

x (rT'-rTVmidT')
+ r TVmidT' In this formula, r INmax
T' is the maximum value of the saturation of the color solid of the printed matter at L''T' and θT' (see FIG. 13).

In addition, u"T", V car T" is θT" = θ
T', and rT'' are values such that the above expressions are satisfied.

As mentioned above, L army T'', u''T=, V vehicle T
“(Target value T”) is all within the color reproduction range of the television display.

Taste, L”T”, uIXT”, V required in this way
The main T'' is expanded outward within the color reproduction range of the television display using the methods described in [Example 1] and [Example 2] below.

The maximum value of saturation was determined as follows.

Only the combined values that form the outer surface of the color solid are lightness Lm, saturation, and saturation.There are eight surfaces that form the outer surface of the Japanese color solid, Y' and M'.

C' or B, G. It is a surface where all R is O or maximum. and hue θ. The position on the grid that includes the brightness wheel is found, and the weighting is determined by averaging the saturation values of the four points around it.

c Example 1] The maximum value of the saturation of the color solid on the printed matter (input side) at L'T'', θT'' is rlNaxT'', and the maximum value of the saturation of the color solid on the TV display (output side) is r TVma
xT'', r rNmaxT'' is rTVmaxT
−When less than or equal to r^maxT” = r INm
axT-, and rlNmaxT″ is rTVmaxT″
When it is larger, r AmaxT''=rTV■axT
~. Then, r^-axT” is multiplied by 8 (a<1,
0), for example, the saturation value rAidT'' which is approximately 2/3 times as large as the threshold value (as shown in FIG. 14).

If rT″ is less than r AvidT″, do not convert and convert L car T″ 2=L'T″, u”T″ 2=u
"T", v"T=2=v book T", rT"2= r d#
, θT #2=θT−.

Moreover, if rT″ is larger than r^m1dT″, θ
Depending on T″, rT″2 etc. are set as follows.

The hue angle θ is as follows: θ = Oo ... Positive θ on the U * axis = 90° ... ■ Positive θ on the main axis = 180" ... - Negative θ on the U * axis = 270'
... V axle upper pressure θ = 360" ... When U-axle member (see Fig. 15), 120°≦θT"≦1
When 70° is not satisfied, L”T”2=L book T”,
Set θT″2=θT″ and set rT″2 as shown in the following equation.

X (rT″-r Am1dT-) +r Avid
T"U main T"2, V vehicle T-2 are θT"2; θT
″, and rT″2 are values such that the above expression is satisfied.

Next, when 120°≦θT″≦170＠ is satisfied, first convert “0” to θT″2 using the following equation.

In Uni, 131° is the hue angle at the maximum saturation of G (green) in the color solid of a television display (see Figure 11), and 147° is the maximum saturation of G (green) in the color solid of printed matter. (See Figure 3).

120’≦θT″≦1476, 8 guns “2” becomes.

147"<θT"≦170°, θT”　2 becomes.

Also, set L'T"2=L'T" and set rT"2 as follows.Here, the saturation of the color solid of the printed matter (input side) at L4T"2, θT"2 Maximum value rlN
The layer axT~2 is assumed, and the maximum value of the saturation of the color solid on the television display (output side) is assumed to be rTVmaxT''2.

When r INmaxT″2 is less than or equal to rTV layer aXd″2, rAmaxT″2= r INmaxT
``2, r INg + axT'' 2 is rT
When larger than VsaxT″2, r AmaxT″2
= r TVmaxT″2. And r A
The saturation value obtained by multiplying m1dT″2 by a (a<1°0), for example 2/3, is defined as rAvidT″2.

X (r T--r Am1dT# 2) + r
Am1dT#2 Note that u*T″2 and v″T″2 have values that result in the hue angle θT″2 and the saturation value rT″2 as described above.

L*T"2.u"T"2.v*T obtained in this way
"2 (target value T"2) means that the saturation is increased within the color reproduction range of the television display.

[Example 2] The maximum value of the saturation of the color solid on the printed matter (input side) at L*T'', θT'' is rINmaxT'', and the maximum value of the saturation of the color solid on the TV display (output side) is rTVma.
xT″, r INmaxT″ is r TVmaxT
``When it is less than r AmaxT'' = r INm
axT", rlNsaxT" is rTVmaxT"
When larger than r AmaxT″= r TVma
xT''. Then r Ag+axT'' is multiplied by a (
a<1.0), for example, the saturation value r^m1d multiplied by about 2/3
Let T″ be the threshold value (as shown in FIG. 14).

If rT" is less than rA idT"Am1dT", do not convert, L*T"2=L book T", U book T" 2= u car T
−, v car T″2=v car T″, rT″2″ r T″, θ
Let T″2θT″.

Moreover, if rT″ is larger than r Am1dT″,
rT″2 etc. are set as follows according to θT″.

When 200°≦θd−≦300@ is not satisfied,
Let L car T''2=L car number#, θT-2=θT#, and set rT″2 as shown in the following equation.

X (r T# - r Am1dT") + r
Am1dT=U car T″2, v″T″2 is θT″2
=θT-5 and rT"2 are values such that the above equation is satisfied.

Next, when 200@≦θT″≦300° is satisfied, θT″ is first converted into θT″2 using the following equation.

Here, 266''' is the hue angle of B (blue) at maximum saturation in the color solid of a television display (see Figure 11), and 234° is the hue angle of C (cyan) in the color solid of printed matter.
This is the hue angle at maximum saturation (see Figure 3).

200°≦θT″≦234°, θT”2 becomes.

At 234″×θT″≦300°, θT" 2 becomes.

Also, L*T″2=L book T″, and rT″2
Let be as follows. Here, the maximum value of the saturation of the color solid of the printed matter (input side) in the L car T"2, θT"2 is rl
The N column axT is set to "2," and the maximum value of the saturation of the color solid on the television display (output side) is set to rTVmaxT"2.

When r INmaxT= 2 is less than r TVmaxT-2, r^maxT″ 2= r INmax
T″2 and rINmaxT″2 is rTV
When larger than saxT″2, r Am1dT″2=
Let r TVmaxT″2. And r^ma
The saturation value obtained by multiplying xT″2 by a (a<1°0), for example 2/3, is defined as rAm1dT″2.

x(rT" -r Am1dT" 2) + r
Am1dT"2, u'T"2, v'T"2 are
The values are such that the hue angle θT is "2" and the saturation value rT is "2" as described above.

L book T″2, which is obtained in this way, u book T−2, v
'T''2 (target value T''2) has increased saturation within the color reproduction range of the television display.

In addition, in this [N1] and U example 2, the saturation is increased to the maximum of the color reproduction range of the TV display, but of course it is not necessary to increase it to the maximum, and the amount of increase can be changed as desired. Just adjust it.

Next, L"T"2. which is determined as described above for each combination of Y', M', and C'. u”T”2゜V book T”
2 is given to the color solid of the TV display array (shown in FIG. 11) as a target value T″2, and by convergence calculation, R, G,
Find B. Since the convergence calculation is the same as that explained in FIGS. 5 to 9, the explanation will be omitted.

This allows the reproduction colors of each combination of Y'2M' and C' to be reproduced on a TV display, for example.
.

As mentioned above, Y', M obtained by processing ■~@
R for each combination of image data of ', C',
Image data of G and B is color masking W220
is stored in a lookup table (LUT) within Y'
, M', and C', respectively.

Next, from the image data of Y', M', and C', RlG,
An example of the color masking device 220 that obtains H image data will be described.

By the way, if the LUT were to store R, G, and H image data corresponding to all the combinations of Y', M', and C' image data, the capacity of the LUT would become enormous.

Therefore, in order to reduce the memory capacity, the applicant has
The color space formed by the image data of Y', M', and C' is divided into a plurality of basic grids, and the LUT contains R for the combination of the image data of Y', M', and C' located at the vertices.
, G, H, Y', M',
R, G, for the combination of image data of C'
When the image data of B does not exist, these Y', M
', C' at the vertices of the basic lattice that includes the image data (interpolation points) RlG, R, G by the weighted average of the image data of B.

We proposed to obtain image data of B.

In this sense, as described above, only R, G, and B image data corresponding to 32X32X32=32768 combinations of Y', M', and C' image data are obtained and stored in the LUT.

For example, as shown in FIG. 16, if there is an interpolation point P in the basic grid consisting of vertices A-H, then the interpolation point P and the diagonal vertices are created. The volume of the rectangular parallelepiped is used as a weighting factor for the R, G, and B image data of vertices A to H.

That is, the vertices A~ of the basic lattice that include this interpolation point P
RlG of H, image data of B as Ri, Gt, B
i (i=1~8), FL of vertices A~H, G.

The weighting coefficient for the image data of B is Ai (i=1~
8), R, G, B image data RP, GP, Bρ at the interpolation point P are calculated by the following equations.

Rp = (1/ΣAi) Ai Ri Gρ = (1/ΣAi) ΣAi Gi Bρ = (1/ΣAi) ΣAi Bt (1) In such interpolation processing, R, G, B of the interpolation point When calculating the image data Rp, Gp, and BP of , it is necessary to perform the multiplication and accumulation process eight times for each image data.

The present applicant has proposed an interpolation process that can reduce the number of times this multiplication and accumulation process is performed.

As shown in FIG. 17, a total of six pentagonal pyramids are formed by one-dot chain lines with respect to the basic lattice composed of vertices A-H. When the coordinates of the interpolation point P are (5, 1°2), this interpolation point P is located at the vertices A and B as shown in FIG.
It can be seen that it is included in the pentagonal pyramid T formed by , C, and G.

Once the pentagonal pyramid T is determined, as shown in Fig. 18, the interpolation point P is then connected to the vertices A, B, C, and G.
A total of four new pentagonal pyramids are formed, each with a volume V
BCGP, V ACGP, V ABGP,
VABCP is required. These volumes and vertices A,
B, C, G RlG, B image data RA~
Interpolation point P from RCi, GA~GG, BA~BG
The R, G, and B image data RP, Gρ, and BP are calculated using the following equations.

V ABCG is the volume of the pentagonal pyramid T.

Rp = 1 / VABCG (VBCGP-RA + VACGP-RB + VABGP-RC + VABCP
-RG)Gp = 1/VABCG(VBCGP-GA
+VACGP-GB+VABGP, GC+VABCP
, GO) Bp = 1/VABCG (VBCGP・BA
10VACGP-BB+VABOP-BC+VABCP,
BG) (2) If the coordinates of the interpolation point P change, the pentagonal pyramid T used will also change. For example, if the coordinates of the interpolation point P are P(3, 1,
5), this interpolation point P is included in the pentagonal pyramid T formed by the vertices A, C, D, and G, as shown in the 19th country, so this pentagonal pyramid T is used.

In this way, in the interpolation process using a pentagonal pyramid, the R, G, and B image data Rp, Gp, and BP of the interpolation point can be calculated by four times of multiplication and accumulation processing.

FIG. 20 shows an example of a specific configuration of a color masking device.

In the same figure, 2o is a color correction data storage means, and a lookup table (ML
LIT) 21R to 21B have R, G, H, respectively.
color correction data is stored.

By the way, as MLUT21R to 21B, for example, a 256-bit capacity ROM is used, and as mentioned above, only 32 points between the minimum level and the maximum level of the image data of Y', M', and C' are extracted. and MLUT21
32x32x32=3276 for each of R~21B
Eight points of image data are stored.

In this case, the image data of Y', M', and C' is 8 bits and has 256 gradations, and the distribution of 32 points is, for example, starting from 0 and dividing it into "8" increments. 16.
..., 240.248, making a total of 32 points, and the 33rd point from 249 to 255 is not used or is treated as 248.

R and G of each such distribution point, that is, the vertices of the basic lattice whose basic lattice spacing is 8 quantization levels.

The image data of B is calculated by the above-mentioned processes ① to ＠, and the calculated image data is stored in the MLUTs 21R to 21B.

Further, 60 is a look-up table (WLUT) constituting a weighting coefficient storage means. The WLUT 60 stores weighting coefficients corresponding to each interpolation point.

In the case of interpolation processing using a cube, when the basic lattice spacing is 8 quantization levels as described above, the sum of the 8 weighting coefficients is 8x8x8=512, but this is normalized to 256. be converted into In addition, so that an 8-bit general-purpose IC can be used as the WLUT 60, the maximum value of the weighting coefficient is set to 255.1For example, if the interpolation point P is at the same position as the vertex A in Fig. 16, the weighting coefficient P1 to P8 are as follows.

PL, P2. P3. P4. P5. P6. P
7. P8255, 0 , 0 , 0 , 0 ,
0, 0, 1 (512, O, 0, 0, O, 0,
0, O), and the sum of the weighting coefficients is always 256.

In addition, in the case of interpolation processing using a pentagonal pyramid, when the basic grid spacing is 8 quantization levels as described above, the sum of the four weighting coefficients is 5x8x8/6=512/6, but This is normalized to 256. In addition, so that an 8-bit general-purpose IC can be used as the WLUT 60, the maximum value of the weighting coefficient is set to 255. For example, if the interpolation point P is at the same position as the vertex A in FIG. VaCσ.

V AC (F, V AB (F, V ABCP) is as follows.

V BCGP, V AC(F, V ABG
P, V ABCP255, 0. 0.
1 (512/6. 0. 0. 0
), and the sum of the weighting coefficients is always 256.

The image data of Y', M', and C' are stored in a look-up table (PLUT) 4 constituting the address signal forming means 40.
1Y to 41C, and this PLUT41
The signals Y to 41C are supplied with signals from the controller 50.

PLUTs 41Y to 41C output a 5-bit address signal corresponding to the upper 5 bits of the image data of Y', M', and C' (representing the reference point of the vertex of the basic grid including the interpolation point P). Each is supplied to MLUTs 21R to 21B.

In the case of interpolation processing using a cube, the distribution is based on the signal, and the eight vertices of the basic lattice where the interpolation point P is combined are M
Five-bit address signals are sequentially output as specified by LUTs 21R to 21B.

In the case of interpolation processing using a pentagonal pyramid, the distribution of signals is based on the four vertices of the pentagonal pyramid that includes the interpolation point P.
Five-bit address signals are sequentially output as specified by the UTs 21R to 21B.

R and G output from MLUT21R~21B.

The B image data is supplied to multipliers (MTL) 31R to 31B that constitute the multiplication and accumulation means 30, respectively.

Also, Y' and M' from PLUT41Y to 41C.

The lower three bits of the image data of C' (representing the position of the interpolation point P in the basic grid) are output as a weighting coefficient designation signal.
This weighting factor designation signal is supplied to the WLUT 60. This WLUT 60 is supplied with a signal for the distribution from the controller 50, and weighting coefficients for the distribution are sequentially output based on the signal.

In the case of interpolation processing using a cube, eight weighting coefficients P1 to P8 are specified in response to the eight vertices of the basic lattice including the interpolation point P being sequentially specified in the MLUTs 21R to 21B.
are output sequentially.

In the case of interpolation processing using a pentagonal pyramid, four weighting coefficients are sequentially output as the four vertices of the pentagonal pyramid including the interpolation point P are sequentially specified in MLUTs 21R to 21B. .

The weighting coefficients output from WLUT60 are MTL31R~
31B. And this MTL31R~31
In B, R output from MLUT21R to 21B,
G, B image data (8 bits) and WLUT
Multiplication with a weighting factor (8 bits) from 60 is performed.

The multiplication outputs of the upper 8 bits of the MTLs 31R to 31B are respectively supplied to accumulators (ALUs) 32R to 32B and subjected to addition processing. For this ALLI32R~32B,
A reset signal is supplied from the controller 50.

In the case of interpolation processing using a cube, addition processing is performed sequentially corresponding to the eight vertices of the basic lattice that includes the interpolation point P, and each time the result is latched by a latch circuit described later, it is reset.・It will be recorded.

In the case of interpolation processing using a pentagonal pyramid, addition processing is performed sequentially corresponding to the four vertices of the pentagonal pyramid that include the interpolation point P, and each time the result is latched by a latch circuit described later. will be reset.

As mentioned above, the sum of 8 weighting coefficients in the case of interpolation processing using a cube and the summation of 4 weighting coefficients in the case of interpolation processing using a pentagonal pyramid is 256. In this example, MTL31R to 31B
The upper 8 bits of the multiplication output are used and a so-called 8-bit shift is performed, so that 1/S Ai in equation (1) and l/V A in equation (2)
BCG+7) processing will be performed.

The outputs of the ALUs 32R to 32B constituting the multiplication/accumulation means 30 are supplied to latch circuits 71R to 71B, respectively. A controller 50 is provided in these latch circuits 71R to 71B.
A latch pulse is supplied.

In the case of interpolation processing using a cube, the results of sequential addition processing corresponding to eight vertices of the basic lattice including the interpolation point P are latched.

In the case of interpolation processing using a pentagonal pyramid, the results of sequential addition processing corresponding to the four vertices of the pentagonal pyramid including the interpolation point P are latched.

Therefore, from these latch circuits 71R to 71B, in the case of interpolation processing using a cube, the equation (1) is shown, and in the case of interpolation processing using a pentagonal pyramid, the output is shown in equation (2). R, G of interpolation point P.

Image data of B is output.

In this example, the basic colors of the color separation image of the color hard copy are explained as four colors, Y, M, C, and K. However, this method can be applied similarly in the case of the three colors of Y, M, and C. can be applied. In that case, Y'.

It is sufficient to use the data of Y, M, and C directly for M' and C'. In that case, from Y, M, C, and K,
'.

The part for determining M' and C' will be removed.

In this way, in this example, regarding the brightness direction, the brightness spread on the achromatic axis of the color solid of the printed matter (input side) and the color solid of the television display (output side) is
Of the color system values obtained for each combination of Y', M', and C', Lm is converted, and the brightness of the color solid of the printed matter is enlarged and mapped. In addition, regarding the saturation direction, conversion is not performed in the central part of the overlap between the printed matter's color solid and the TV display's color solid, and in the periphery, Y' , M', and C', of the values of the color system obtained for each combination, the U and V wheels are converted, and the saturation of the color solid of the printed matter is enlarged and mapped.

In this case, if the color solid of the television display is smaller than the color solid of the printed matter in the direction of saturation, the color solid of the printed material is compressed and mapped to fit within the color solid of the television display, and then enlarged. Mapping is performed.

Then, based on the values of the color system enlarged and mapped in this way, R, corresponding to each combination of Y', M', and C' are calculated.
Since a combination of G and B is required, the color reproduction on the TV display using the required R, G, and B image data naturally covers the color reproduction range of the TV display, and has sufficient brightness and color. It may have a range of degrees.

Furthermore, when the saturation of the color solid of a printed matter is enlarged and mapped, the G (green) peak of the printed color solid may move in the direction of the G (green) peak of the color solid of the television display, or Since the hue of C (cyan) is shifted in the direction of the B (blue) peak of the color solid of the television display, the overall saturation is balanced.

In addition, in [Example 2] of @ in the above embodiment, the hue of the C (cyan) peak of the color solid of the printed matter is shifted in the direction of the B (blue) peak of the color solid of the television display. However, it may be shifted in the direction of the G (green) peak in the opposite direction.

In addition, in [Example 1 and [Example 2] of @ of the above embodiments,
Although the hue range in which each hue is shifted is only one region, it may be multiple, and the two examples [Example 1] and [Example 2] may be used in combination.

Further, in the above embodiment, the brightness is kept constant when the saturation is changed, but the brightness may be changed as the saturation is changed.

[Effects of the Invention] As explained above, according to the present invention, in the brightness direction, input color separation image information is Of the color system values obtained for each combination, LX is converted,
The brightness of the input color solid is enlarged and mapped. Regarding the saturation direction, the central part where the color reproduction ranges of the input and output color solids overlap is not converted, and in the surrounding area, the input color separation is performed according to the spread of the saturation of the two color solids. Among the color system values obtained for each combination of image information, U*,
Five V lines or A cars are converted, and the saturation of the input color solid is enlarged and mapped. Then, a combination of output color separation ILF image information is obtained in correspondence with the values of the enlarged and mapped color system, so that the color reproduction based on the obtained output color separation image information naturally covers the output color reproduction range. Therefore, it can have a sufficient range of brightness and saturation. Also, when the saturation of the input color solid is expanded, the hue of each color in the input color solid is shifted in the direction of the peak of the corresponding color in the output color solid, so the overall saturation balance is It can be treated as something that has been harvested.

[Brief explanation of the drawing]

FIGS. 1 to 15 are diagrams for explaining the color estimation method according to the present invention, FIGS. 16 to 19 are diagrams for explaining the interpolation process, and 20th is a configuration diagram of the color masking device. Second
1 and 22 are diagrams for explaining the conventional method. 100...Television display 200...Color separation image correction device 211-213...Lightness L * Assignment of target value T' Fig. 6 SL Y (M' seat Fig. 8 81' 20 25---95 100u* 0
0 ・・・・・・−・−・・・・・−・・・・・・
00v" OO------------... 0
0 clay stage chart Fig. 12 V* *N Relationship between hue angle and U axis, V axis Fig. 15 Explanation of the opposite valley line Fig. 13 H 8 '8 Expansion of the range of values 4 da'' Fig. 22

Claims (2)

[Claims] (1) Find the value of the color system for each combination of a plurality of input color separation image information, find the value of the color system for each combination of a plurality of output color separation image information, and calculate L^ as the color system. *u^*v^*Color system or L^
Using the *a^*b^* color system, L^* of the values of the color system obtained for any combination of the above input color separation image information is calculated for each combination of the above input color separation image information. The difference between the maximum and minimum brightness values on the achromatic color axis of the input color solid, which is composed of the values of the color system determined for , and the table determined for each combination of the output color separation image information. It is converted according to the ratio of the difference between the maximum value and the minimum value of brightness on the achromatic color axis of the output color solid composed of color system values, and the obtained value is obtained for any combination of the above input color separation image information. Among the color system values u^*, v^* or a^*,
b^* is the hue of the input side color solid whose saturation is above,
If the saturation is smaller than a times the maximum saturation value at lightness (a < 1.0), no conversion is performed, and the saturation is at least a times the maximum saturation value at the hue and lightness of the input side color solid at that time. In the case of The outer surface of the output color solid consists of the inner surface of the input color solid and the maximum saturation value of each hue and lightness of the output color solid. The entire area surrounded by When the hue falls within a predetermined range before and after the maximum saturation point of the six colors blue, green, red, yellow, magenta, and cyan, the output side is the same as the color corresponding to that hue. The hue is determined to be shifted in the direction of the maximum saturation point of the color of the color solid, and the color system values obtained for each combination of the plurality of output color separation image information are used to calculate the input color. A color estimation method characterized by determining a combination of the output color separation image information that obtains the same value as the value of the converted color system for any combination of color separation image information. (2) When the three primary colors of the input color separation image information and the three primary colors of the output color separation image information are different, the value of the color system for each combination of the plurality of input color separation image information is calculated, and the Find the value of the above color system for each combination of decomposed image information, and use L^*u^*v^* color system or L^ as the above color system.
Using the *a^*b^* color system, L^* of the values of the color system obtained for any combination of the above input color separation image information is calculated for each combination of the above input color separation image information. The difference between the maximum and minimum brightness values on the achromatic color axis of the input color solid, which is composed of the values of the color system determined for , and the table determined for each combination of the output color separation image information. It is converted according to the ratio of the difference between the maximum value and the minimum value of brightness on the achromatic color axis of the output color solid composed of color system values, and the obtained value is obtained for any combination of the above input color separation image information. Among the color system values u^*, v^* or a^*,
b^* is the hue of the input side color solid whose saturation is above,
If the saturation is smaller than a times the maximum saturation value at lightness (a < 1.0), no conversion is performed, and the saturation is at least a times the maximum saturation value at the hue and lightness of the input side color solid at that time. In the case of The outer surface of the output color solid consists of the inner surface of the input color solid and the maximum saturation value of each hue and lightness of the output color solid. The entire area surrounded by middle 3
When any of the hues at the maximum chroma point of a primary color falls within a predetermined range before and after it, which of the two hues at the maximum chroma point of the three primary colors in the output color solid that are located before and after that on the hue wheel Using the values of the color system obtained for each combination of the plurality of output color separation image information, the above for any combination of the input color separation image information is determined so as to shift the hue in that direction. A color estimation method characterized by determining a combination of the output color separation image information that yields the same value as the value of the converted color system.