JPH04196679A - Method of estimating color - Google Patents

Abstract

PURPOSE:To prevent contrast of a reproduced picture by from being decreased moving a maximum lightness point of an input side color cube so as to approach a maximum lightness point of an output side color cube substantially and obtaining combination of output color decomposition picture information corresponding to the moved representing color system. CONSTITUTION:At least at high lightness portion, in response to a deviation from u*, v* or a*, b* of a maximum lightness point of an input side color cube to u*, v* or a*, b* of a maximum lightness point of an output side color cube, the u*, v* or a*, b* of the value of the represented color system obtained for each combination of input color decomposing picture information is moved. Thus, in the color reproduction by output color decomposition picture information to be obtained, the maximum lightness portion of the input color reproduction range is reproduced by the maximum lightness portion of the output color reproduction range. For example, when a color picture of a hard copy is reproduced by a television display device, a white color of the hard copy is reproduced by a white color of the maximum lightness able to be displayed on the television display device. Thus, the reduction in the constant of the reproduced picture is avoided.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides color estimation suitable for application to a color separation image correction device used, for example, to reproduce 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 color 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 from a color hard copy into a color television image, image data for yellow Y, magenta M, cyan C, and black are supplied to the color separation image correction device 200, as shown in FIG. Then, this correction device 200 produces red R9 green G.

Blue B image data (color correction data) is output, and this color correction data is supplied to the television display 100.

Here, as a method for obtaining color correction data from Y, M, C, and K image data, it is conceivable to use a method of referring to a look-up table. 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.

In other words, a color patch based on each combination of Y, M, C, and K 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, and evening is output. Display the patch on a color television display and measure the color to determine the value of the color system. Then, using the values of the color system obtained by measuring the color patches on the color television display, Y, M,
For each combination of C, K image data, R, G, H obtains a color system value that is the same as or close to the color system value obtained by colorimetrically measuring the color patch of the color hard copy based on that combination. This image data is obtained by interpolation calculation.

[Problems to be Solved by the Invention] Generally, the maximum brightness of white on a color television display is bluish.

Incidentally, the solid line a in FIGS. 20 and 21 is the color reproduction range of a television display, and the broken line in the figures is the color reproduction range of a hard copy.

Therefore, when reproducing a hard copy color image on a television display, Y, M
, R, G for the image data of C, K.

According to those who obtain the image data of B, the white color of the hard copy is reproduced at a brightness lower than the maximum brightness white color that can be displayed on a television display. This has the disadvantage that the contrast of the reproduced image on the television display becomes low.

Therefore, it is an object of the present invention to avoid an image having low contrast when reproducing a color image of a color hard copy into a color television image.

[Measures to Solve the Problems] According to the color estimation method according to the present invention, the value of the color system for each combination of a plurality of input color separation image information is determined, and the value of each combination of a plurality of output color separation image information is calculated. Find the value of the above color system for the combination.

As a color system, the L/U/V/V grass color system or the L/A/V/V color system is used.

Then, the u*, v* or a*, b wheels of the maximum brightness point of the input color solid, which is composed of the values of the color system determined for each combination of input color separation image information, and the output color separation image. 0 of the maximum brightness points of the output color solid, which is composed of the values of the color system determined for each combination of information, V
If car or 8 lines, b east occur, at least in the high brightness area, 0 line, V car or am, of the color system values found for any combination of input color separation and both image information.
Let b* be the shift amount from u*, vXK or 8 lines, b lines of the maximum brightness point of the input side color solid to 0 line, V line or a*, b car of the maximum brightness point of the output side color solid. Move accordingly.

Then, using the values of the color system obtained for each combination of a plurality of output color separation image information, the above u*, v'' or a
A combination of output color separation image information is found to obtain a color system value that is the same as the color system value obtained by moving the values of the m and b wheels or obtained by applying a predetermined conversion.

[Function] According to the above-mentioned method, at least in the high brightness part, the maximum brightness point of the input side color solid is u*, v kyoku or 8 lines, and the U car is the maximum brightness point of the output side color solid from the B car.

Depending on the amount of shift to the V line, a line, or b line, 0 lines, ■*, 8 lines, or b* of the color system values obtained for each combination of input color separation image information are moved. Ru.

That is, the maximum brightness point of the input side color solid is moved closer to the maximum brightness point of the output side color solid on the u*, v car or 8 car, b car coordinates.

Since a combination of output color separation image information is found in correspondence with the values of this moved color system, in color reproduction using the obtained output color separation image information, the maximum brightness part of the input color reproduction range is used as the output color reproduction range. It can be reproduced with the maximum brightness part of .

For example, when a hard copy color image is reproduced on a television display, the white color of the hard copy is reproduced with the maximum brightness that can be displayed on the television display.

Therefore, the contrast of the reproduced image does not become low.

[Example] Hereinafter, as an example of the present invention, Y for color printing,
A case of obtaining R, G, and B image data of a color television display corresponding to M, C, and K image data will be explained with reference to the drawings.

Here, Y, M, C, K, R, G, B
The image data are all 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) (converted).

Further, the compressed print data Y', M', and C' are supplied to a color masking device w220 and converted into red R5 green G and blue B image data (display data).

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

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

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

0 army, ■Calculate the value of the car surface color system.

In this case, for each of the image data of Y', M', and C'', 5 of 0.64.128.192.255
Take two quantization levels and create a color patch of each combination of colors (x5x5=125).
(Illustrated in the second figure).

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 values of LX,
Find the values of the u*, vz color system.

Here, by interpolating the middle of 5X5X5=125, 9X
Make 9X9=729. Color measurement may be performed by printing color patches of 9×9×9=729 colors, but this requires a large number of measurements and takes time.

In this way, L car u*, y color system values are 9X9X9=72 based on image data of Y', M', C'.
Find out about 9 colors.

This L book, U wealth, ■ the value of this color system, L book INI (Y ', M', C') u''
INI(Y', M*, C'>v*1N1(Y
',M',C').

FIG. 3 shows the values in the 1-line, u*, v color system, which will hereinafter be referred to as the color solid of printed matter.

■Next, color patches based on 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 book, v*
Find the value of the color system.

In this case, for equal amounts of Y, M, and C, 0.
64, 128. There are five quantization levels of 192 and 255, and K image data is also 0 for each.
,64. 128. A color patch is created by taking the level of 192.255. In other words, as shown in the fourth factor, 5×5×25 color patches are created.

Then, colorimetrically measure this color patch in the same way as in the process in ■ to find the values of the x, y, z color system, and then calculate the L*
, u book, and find the values of the vXI color system.

■Next, Y', M', and C are set so that all of the values of Ll, u, and ■11 color system obtained in ■ are included in the color solid by the combination of Y', M', and C'. ' L*, 1 line, which was obtained by ■, is proportionally extended to the low Lm value side so that the minimum value of L8 value of the color solid of ' is lowered.
Y' corresponding to the value of the vehicle color system.

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

In other words, LX is determined corresponding to each color combination of Y, M, C, and K (5x5=25>).

The values of the u*, y* color system are given as target values 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*, u*, v color system by the above-mentioned process (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.

7th rI! J becomes Y, M, C by processing ■
The combination of and K (5 x 5 = 25 pieces) is L*, 1 piece.

■It is mapped to the car color system.

First, the values of the image data of Y, M, C, and K for each combination of image data, U*, and vehicle color system are given as the target value T' (see Figures 6 and 7). ).

In this case, the target value T' is as shown in FIG. When it is within the area surrounded by grid points a' to d', Y',
Combination of Y' and M' in M' coordinate system (target value T
) is estimated to be within a region surrounded by grid points a to d as shown in FIG.

The location of the target value T in the area formed by the grid points a to d is determined by 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 formula. This is because it 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 to i are calculated by weighted averaging using surrounding grid points that have already been determined. , and the values corresponding to this dividing point C~i are Lm, u*,
■ Plot the values when converted to this color system on the color system in Figure 9, and select which region among the four regions Sl' to 34' formed by the plotted division points e' to i'. Determine whether there is a target value T'. When the target value T is in the region S2' as shown in FIG. 9, it is estimated that the target value T is in the region S2 corresponding to the region 32' as shown in FIG.

Next, the estimated region S2 is equally divided into four regions 85 to S8. The five division points j-n are calculated by weighted averaging using the surrounding grid points and division points that have already been determined. Then, the values when converting the values corresponding to this division point j %, n to L*, U*, ■ this color system are expressed as the 9th
Plotted in the color system shown in the figure, and the plotted division point j′ ~
It is determined in which region of the four regions 55' to 88' formed by n' the target value T' is located. When the target value T is in the region 38' 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, the value corresponding to this dividing point 0 to S is L
The values obtained when converted to the *, u-book, and y-book color systems are subtracted by 70 to the color system shown in Figure 9, and the plotted division point Ω is
4 regions 39' to 812 formed by ' to S'
' in which area the target value T' is located is determined. 9th
As shown in FIG.
It is assumed that it is located at O.

By repeating this region division, the grid becomes smaller and smaller until it finally converges. Then, by averaging the four lattice points or division points forming the converged area, a combination of basic colors that yields 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. , C and K to C
'Y, M, C.

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

■As above, Y, M, C and K are 0.64
Image data of Y', M', and C' are obtained for the combination of quantization levels of ゜128.192.255, 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 it. For example, for point U, grid points e, f
, g, and h by the weighting coefficient to obtain U
Find the point.

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

Image data of Y' corresponding to all points of K) 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 iii*data R,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 H image data is created by the following method.

■First, display color patches based on each combination of R, G, and B image data on a TV display and measure the color.
Find the values of X, Y, 2 color system, and further calculate L*, U
Book, ■Determine the value of the car color system.

In this case, for each of R, G, and B image data, 0. 64. 128. 192. 255 quantization levels are taken, and the colors resulting from each combination of these (5X5X5=125) are displayed one by one on a TV display, and each color is measured using a spectroradiometer, as shown below. Find the values of the X, Y, and Z color systems, and further find the values of L*, U*, and ■the vehicle color system.

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
．． 3 1 2 7Yn / (Xn+Yn+Zn
) = 0. 3290 The absolute value levels of Xn, Yn, and Zn must be determined, but x, y, z
In order to match the level of the measured value, white (R
=G=B=255), X, Y,
Yn is made approximately equal to Y of the value of Z.

In addition, by interpolating the middle of 5X5X5=125, 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 values of L books, u*, v Kyoto color system are R, G,
It is determined for 9x9x9=729 colors based on the B image data. Let the values of this L*, U book 1 v Kyoto color system be L book TVI (R, G, B) U Tokyo TVI (R, G, B) V book TVI (R, G, B). Figure 11 shows the values as L5 u books, v*
This is shown in the color system, and hereinafter this will be referred to as the color solid of the television display.

0th order, L” TVl, u” TV determined by ■
An operation is performed to shift the high brightness part of the color solid of the television display so that the maximum brightness point of the color solid of the television display consisting of the values of I, v'TVI is shifted to the origin of u'' = O1V car = 0. .

In television displays, the color temperature of white is set to about 8,000 to 20,000 in order to produce white clearly, and even the high-definition display used in this example was about 8,500.

The maximum brightness value for the color solid of a television display is the value for white. Since the reference white value is 6500, a white value of 8500 will deviate from the origin of U lines = 0 and V lines = 0. In this example, the values of u* at the maximum brightness point, seven lines, were u''=-20°2, V line=-44.8.

Such a white shift becomes a problem when reproducing a printed image into a television display image as described above.

In other words, the maximum brightness value of white in printed matter is u = 0, v
K: At the origin of Q, the white color with the maximum brightness value of this printed matter is simply expressed as u*=0 in the color solid of the TV display.
,■*=0, if it is reproduced at the maximum point on the LX axis, the white color with the maximum brightness of the printed image no longer corresponds to the white color with the maximum brightness of the TV display, and becomes a white color with low brightness (Fig. 20). and FIG. 21), that is, the contrast of the reproduced television display image becomes low.

In order to solve this problem, in the high brightness area near white of the color solid of printed matter, the maximum brightness point is from u''=o, v car=0 to u''=-
It is conceivable to shift the brightness so that it becomes 20,2, V car = -44,8, and make the maximum brightness of the printed matter correspond to the maximum brightness of the television display.

In this example, the saturation compression mapping process described later, which is performed due to the difference in the size of the color reproduction range of printed matter and the color reproduction range of a television display, is performed on the L axle where u = 0 and vx = 0. Since the image is mapped inward from the center, instead of moving the color solid of the printed matter, the high brightness area near white of the color solid of the TV display is mapped to the point where the maximum brightness point is u''w-20.
, 2, V*=-44, 8 to U lines; 0, V=0, and as a result, the maximum brightness on the printed matter corresponds to the maximum brightness on the television display.

Due to the movement of the color solid of the TV display, it was obtained by the process of ■TV′1, u”T′/1, v”T
Vl as follows: L car TV2, u'TV2, V
Convert this to TV2.

If L wealth TVI < 70, L * TV2 = L TVI u ” TV:'-u ” TVI v ' TV2 = v ” TVI If L wealth TVI < 70, then TV2 = L TV1, u'TV2 = (L TV170) / 30 x 20.2 +
u” TI/1v”TV2 = (Lkyo TVI-70)/30X44.8+v”TVl
In this example, the shift amount is set as a proportional amount of (L TVI-70) in the range of L"TVI≧70, but the threshold value does not have to be 70, and the shift amount also exceeds the threshold value. It may also be changed non-linearly.

(2) Next, find the maximum and minimum values of LX from the color solid values of the printed matter.

In this case, among the 9X9X9=729 colors, the combination that maximizes L ky and the combination that minimizes Lm are determined, and then L colors are determined.

``Maximum value''Y' = M' = C' = O, which is the L value for the white background, and is L' lN15ax.

"Minimum value" This is the value of the L car when black is printed with Y'=M'=C'=255, and L is 1N15 inches.

■Next, the maximum and minimum values of LX are determined from the color solid values of the L Army Tv2, U Main TV2, and ■*Tv2 Niyor TV displays.

In this case, a combination with the maximum LX and a combination with the minimum LX are found among 9X9X9=729 colors, and the L car at that time is determined.

"Maximum value" This is the value of L wealth when white is displayed with R=G=B=255, and it is set as LkyoTV2■ax.

"Minimum value" is the value of Lm when black is displayed with R=G=B=O,
L car TV2-in.

■Next, the value of the color solid of the printed matter L” INl, u”
INI.

V car INI, L book IN2. U car I82.
Convert to v car IN2.

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

X (L car lNl - L car lN1m1n) + L book T
V2@in Accordingly, u* and y K are also converted as shown in the following equation.

[Phase] Next, a gray stage chart in which Lm is equally spaced is displayed on the television display.

In other words, U book, V car = O, L book is 20 to 1
A gray scale chart with a range of 00 and an interval of 5 quantization levels is displayed (see the 12th book).

In this case, the color solid data is L car TV2 (R.

G, B>, u”TV2 (R, G, B),
v”TV2(R.

G, B) is used to find the values of R, G, and H 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 B image data obtained at each step as described above.

0 Next, a printout of a gray stage chart in which L pieces are equally spaced is created.

In other words, U book, V book; 0, L book is 20 to 100.
A gray stage chart is created that has a range of 5 quantization levels and an interval of 5 quantization levels (see FIG. 12).

In this case, the color solid data of the printed matter L"1N2(Y',
M', C'), u'1N2(Y', M
', C').

Using V book yN2(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* Convert the values of the color system.

XCL car IN2max-L book lN2m1n) +
L car lN2m1nHere, change the value of constant γ, L”
lN3. u”lN3. v Recalculate to IN3, and perform the operation of ■ to LIN2゜U bulk IN2. v' lN2
Instead of L*lN3. Apply U car IN3 and V*IN3 and compare again with the chart on the TV display.

Then, repeat the above operations ① and 0, and use the L''lN3.u car IN3.v car IN3 in the following operations.

0th order, R for each combination of 5 of Y', M', C',
Find the combination of G and H (color correction data).

That is, Y' is determined as described above.

The color of each combination of M' and C' (32x32x32=3
L", u*, v value wheel IN3. u" lN3. v”lN3 as the color 3D of the TV display (not shown, L*TV2, u”T
V2, v'' (consisting of TV2) as the target value T', 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, L" lN3. u " lN3. is found for each combination of Y', M', and C'. v car Tl
The value of N3 is given to the color solid of the television display as the target value T'. The values of L*, u book, and v east at this time are respectively L''T', ukyoT', and vkyoT'.

In addition, the saturation value determined by u v is rT′, arctan (v ” T′ /u ” T
), and let θT' be the hue angle found by
The threshold value is the saturation value rTVmidT' which is 8 times (a<1.0), for example, approximately 2/3 times the maximum saturation value rTVmaxT' of the color solid of the television display at N3, θT'. (see figure).

If rT" is less than rTVmidT', do not convert and use Lkyo T"=L"T', u"T"=u car T
′, VkyoT”=vcarT’, rT”=rT’, θT
″=θT′, and if rT′ is larger than rTVmidT′, L*T″=L books T′, θT″=θT
′ and rT″ as shown in the following equation.

x (rT'-rTV+*idT')
+ r TVmidT′ In this formula, r INmax
T' is the maximum value of the saturation of the color solid of the printed matter in the L book IN3, θT' (see the 13th book).

The maximum value of saturation was determined as follows.

Only the values of the combination forming the outer surface of the color solid are converted into lightness Lm, saturation r1, and hue θ and used. Incidentally, there are eight surfaces that are the outer surfaces of the color solid, Y' and M'.

C' or a surface where B, G, and R are all 0 or maximum. Then, the position on the grid that includes the hue θ and brightness wheel is found, and the weighting is determined by averaging the saturation values of the four points around it.

In addition, u"T*, V book T" is θT"=θT',
And rT'' is a value that satisfies the above formula.

As mentioned above, L book T', u car T', v"T'
L*T″, u”T″ converted from (target value T’)
, VkyT'' (target value T'') are all within the color reproduction range of the television display.

Next, for each combination of Y', M', and C', the L"T', u"T", and V book T" obtained as described above are set as the target value T" on the color solid of the television display. give,
Find R, G, and B by convergence calculation. 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', M', and C' to be reproduced on a TV display, for example.
, G, and B are required.

Y', M* obtained by processing ■ to ■ as above
, C' for each combination of image data R, G
, B are stored in a look-up table (LUT) within the color masking device 220, and the image data of Y',
They will be referenced by the image data of 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 B 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 multiple basic grids, and the LUT contains R for the combination of the image data of Y', M*, and C' located at the vertices.
, G, B image data are stored, 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' image data (interpolation points) are included at the vertices of the basic grid RlG, B's image data R, G by weighted average of the image data.

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. 14, if there is an interpolation point P in the basic grid consisting of vertices A to H, 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
R, G, B image data of H to Ri, Gi, B
i (i=1-8), R,,G of vertices A-H.

The weighting coefficient for the image data of B is At (i=1 to 8)
Then, R, G, B image data Rρ of interpolation point P
, Gρ, and Bp are calculated by the following equations.

Rρ=(14,Ai),>, At RiGρ=(1
/ΣAi) At Gi BP= (1, →, Ai ), >, Ai Bi・ (1
) In such an interpolation process, when calculating the R, G, B image data Rp, Gρ, Bp of the interpolation point, eight multiplication and accumulation processes are required for each.

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. 15, a total of six pentagonal pyramids are formed by one-dot chain lines for the basic lattice composed of vertices A to 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, the interpolation point P is then connected to the vertices A, B, C, and G, as shown in Figure 16.
A total of four new pentagonal pyramids are formed, each with a volume V
BCGP, V ACGP, V ABGP,
V ABCP is required. These volumes and vertices A,
B, C, G RlG, B image data RA~
Image data Rρ, Gρ, and Bρ of R, G, and B at the interpolation point P are calculated from RG, GA to GG, and B^ to BG using the following equations.

V ABCG is the volume of the pentagonal pyramid T.

Rρ= 1 /VABCG(VBCGP-R^+VAC
GP-RB +VABGP-RC+VABCP-RG
) Gp = 1 / VABCG (VBCGP-GA
10 VACGP-GB +VABGP-GC+VABCP
GG)Bp = 1 /VABCG(VBCGP・B
A ten VACGP-BB +VABGP-BC+VABC
PBG )... (2) If the coordinates of the interpolation point P differ, the pentagonal pyramid T used will also differ. 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 FIG. 17, 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 Rρ, Gρ, and BP of the interpolation point can be calculated by four times of multiplication and accumulation processing.

FIG. 18 shows an example of a specific configuration of a color masking device.

In the country, 20 is a color correction data storage means, and the lookup table <ML which constitutes this storage means 20 is
UT) 21R to 21B store R, G, and B color correction data, respectively.

By the way, as MLUT21R to 21B, for example, 2
56-bit capacity ROM is used, and as mentioned above, only 32 leap points from the minimum level to the maximum level of the image data of Y', M', and C' are extracted, and the MLUT21R
~32x32x32=32768 for each of 21B
Image data of points is 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, divided into "8" increments starting from 0, 0, 8, . 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 2, 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. For example, if the interpolation point P is at the same position as the vertex A in FIG. P1 to P8 are as follows.

PL, P2. P3. P4. P5. P6.
P7. P8255, 0, 0, O, O,
O, 0, 1 (512, 0, 0, 0, 0, O, O, 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 8x8x8/6=512/6, but This is normalized to 256. Further, the maximum value of one weighting coefficient is set to 255 so that an 8-bit general-purpose IC can be used as the WLUT 60. For example, if the interpolation point P is at the same position as the vertex A in FIG. 15, the weighting factor VBCGP.

V ACGP, V ABGP, and V ABCP are as follows.

V BCGP, V ACGP, V ABGP,
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 constituting the address signal forming means 40.

(PLtJT) 41Y to 41C, and the controller 50 also supplies signals to the PLUTs 41Y to 41C.

PLUTs 41Y to 41C output 5-bit address signals 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 lattice that includes the interpolation point P). It 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 containing the interpolation point P 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 is based on the signal, and the four vertices of the pentagonal pyramid that include the interpolation point P are ML.
Five-bit address signals are sequentially output as specified by the UTs 21R to 21B.

RlG 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 PLUT41 Y to 41C.

The lower 3 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. The 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 MTL3 1R~3
In 1B, R output from MLUT21R~21B
, G, B image data (8 bits) and WLU
Multiplication with the weighting coefficient (8 bits) from T60 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 for addition processing. A reset signal is supplied from the controller 50 to the ALUs 32R to 32B.

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 is reset each time the result is latched by the latch circuit described later. be done.

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/ΣAi in equation (1) and l/V in equation (,2)
ABCG 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, 2
In the case of interpolation processing using a cube, the R and G of the interpolation point P are shown by equation (1), and in the case of interpolation processing using a pentagonal pyramid, the equation (2) is shown.

Image data of B is output.

In the above embodiment, the basic colors of the color separation image of the color hard copy were explained as four colors, Y, M, C, and K, but this method can be applied similarly in the case of three colors, 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 portion for determining M* and C' will be removed.

In this example, the high brightness portion of the color solid of the television display is shifted from u*=-20, 2, 7 lines me 44.8 to u''=Q, v lines=0, This causes the maximum brightness point on the printed matter to correspond to the maximum brightness point on the television display.

Therefore, when a printed image (hard copy color image) is reproduced on a television display, the white color of the printed image is reproduced with the maximum brightness that can be displayed on the television display.

Therefore, the contrast of the reproduced image will not become low.

In the above embodiment, the u* and v values were shifted so that the maximum brightness point of the printed matter matched the maximum brightness point of the display. , it is also possible to achieve high contrast by shifting the V-honzuke to the extent that they approach each other, and this is included in the scope of the present invention.

Furthermore, in the above embodiment, Lm is used as the color system.

0 pieces, ■L number of pieces using the car surface color system.

It can be similarly applied to those using the a*, b color system.

[Effects of the Invention] As explained above, according to the present invention, the maximum brightness point of the far side color solid is moved substantially closer to the maximum brightness point C of the output side color solid, and this moved table Since a combination of output color separation image information is required with corresponding color system values, in color reproduction using output separation image information, the maximum brightness part of the input color reproduction range is reproduced with the maximum brightness part of the output color reproduction range. be able to. Therefore, for example, when a hard copy color image is reproduced on a television display, even if the maximum brightness white of the television display is bluish, the contrast of the reproduced image will not be low.

[Brief Description of the Drawings] Figures 1 to 13 are diagrams for explaining the color estimation method according to the present invention, Figures 14 to 17 are diagrams for explaining interpolation processing, and Figure 18 is a diagram for explaining the color estimation method according to the present invention. Configuration diagram of color masking device, 1st
Figure 9 is a diagram for explaining the conventional method, Figure 20 and Figure 2.
Figure 1 is a diagram comparing the color reproduction ranges of a television display and a hard copy. 100...TV display 200...Color separation image correction device 211-213...Lookup table 220...Color masking device Explanatory diagram of color separation image correction deviceMater C' = 0 64128192255 C
-= 0 64128192255 Figure 2 Lightness L* 0 Assignment of saturation target value T'Y$z'Zagi Figure 8 t asb Yohizuda 2 degrees Ho 20 25 -・-1--95100u*
0 0-, -・・---o. ” o o −−１・−・・−・・0
0 Gray stage chart Fig. 12 Fig. 1 Etsubo tji Rei Shokuki's appearance Sun Moon Fig. 13 Fig. 15

Claims (1)

[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, u^*, v of the maximum brightness point of the input color solid is composed of the values of the color system obtained for each combination of the above input color separation image information. ^* or a^*, b^*, and u^* of the maximum brightness point of the output side color solid, which is composed of the values of the color system obtained for each combination of the above output color separation image information,
If v^* or a^*, b^* are different, at least in high brightness areas, u^*, v^* of the color system values found for any combination of the above input color separation image information
Or a^*, b^* from the maximum brightness point u^*, v^* or a^*, b^* of the input side color solid to the maximum brightness point u^* of the output side color solid, v^* or a^*,
b^* according to the amount of deviation, and using the color system values obtained for each combination of the above plurality of output color separation image information, The above output color separation image information to obtain the value of the color system that is the same as the value of the color system where the values of u^*, v^* or a^*, b^* are shifted or obtained by applying a predetermined conversion. A color estimation method characterized by finding a combination of.