JP2845523B2 - Color estimation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a color estimation method suitable for use in a color separation image correcting apparatus used for reproducing a color image of a color hard copy into a color television image, for example. About the method.

BACKGROUND OF THE INVENTION When a color image of a color hard copy is reproduced on a color television image, each color system is different. That is, a television image is formed into a color image by an additive method,
The R, G, B color system is used as the color system. On the other hand, a hard copy has a color image formed by a subtractive color method, and a Y, M, C coordinate system is used as a color system, for example. In such a case, conversion of image data, that is, color correction is performed in these color systems.

For example, when a color image of a color hard copy is reproduced as a color television image, the image data of yellow Y, magenta M, cyan C, and sumi K are supplied to the color separation image correcting device 200 as shown in FIG. Then, red R, green G, and blue B image data (color correction data) are output from the correction device 200, and the color correction data is supplied to the television display 100.

Here, as a method of obtaining color correction data from the Y, M, C, and K image data, a method of referring to a lookup table may be used. As a method for obtaining the color correction data stored in the look-up table, for example,
A method as described in JP-A-63-254864 has been proposed.

That is, a color patch based on each combination of Y, M, C, and K image data is output and colorimetrically determined to obtain a color system value, and a color patch based on each combination of R, G, and B image data is calculated. It is displayed on a color television display and colorimetrically measured to determine a color system value. Then, using the color system values obtained by measuring the color patches on the color television display, for each combination of the Y, M, C, and K image data, The image data of R, G, and B that obtain the same value as the color system obtained by measuring the color patches or the value obtained based on the value of the color system is obtained by interpolation.

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

Therefore, as described above, the values of the color system determined for the image data of Y, M, C, and K are directly associated with the values of the color system for the image data of R, G, and B. According to the method for obtaining the G and B image data, there is only a narrow range of colors within the color reproduction range based on the R, G and B image data, and the range of lightness and saturation is narrow, and low lightness ( High density) color,
There was a drawback that high-saturation colors could not be reproduced, resulting in images lacking in contrast and vividness.

Accordingly, an object of the present invention is to enable good reproduction of lightness and saturation when a color image of a color hard copy is reproduced as a color television image.

[Means for Solving the Problems] According to the color estimation method according to the present invention, a color system value for each combination of a plurality of input color separation image information is obtained, and each combination of a plurality of output color separation image information is obtained. Using the color system values determined for each combination of a plurality of output color separation image information,
A color estimation method for obtaining a combination of output color separation image information that obtains a value obtained based on the same color system value or a value of the color system for an arbitrary combination of input color separation image information, The output color reproduction range based on the color system value obtained for each combination of the plurality of output color separation image information is based on the color system value obtained for each combination of the plurality of input color separation image information. When the color gamut is wider than the input color gamut, the colorimetric system determined for each combination of input color separation image information is expanded so that the input color gamut is expanded according to the ratio of the input / output color gamut. The values are enlarged and mapped, and a combination of output color separation image information that obtains the same color system value as the enlarged mapped color system value is obtained.

In addition, when performing the enlargement mapping as described above, for example, in the lightness direction, linear or non-linear mapping conversion is performed so as to match the range, and in the saturation direction, the central portion of the overlapping portion of the color reproduction range on the input / output side. Does not perform mapping conversion, but performs mapping conversion only on its peripheral portion.

[Operation] According to the above method, when the output color gamut is wider than the input color gamut, the input color separation is expanded so as to expand the input color gamut according to the ratio of the input and output color gamut. Since the value of the color system obtained for the combination of image information is enlarged and mapped, and the combination of the output color separation image information is obtained in correspondence with the value of the enlarged color system,
The required color reproduction based on the output color separation image information covers the entire output color reproduction range, and can reproduce sufficient lightness and saturation.

[Embodiment] Hereinafter, as one embodiment of the present invention, Y,
A case of obtaining R, G, B image data of a color television display corresponding to M, C, K image data will be described with reference to the drawings.

Here, the image data of Y, M, C, K, R, G, and B are all 8
It is assumed that bits take values from 0 to 255.

FIG. 1 shows a color-separated image correcting apparatus for obtaining R, G, B image data corresponding to Y, M, C, K image data.

In the figure, image data (print data) of yellow Y, magenta M, cyan C and sumi K are supplied to look-up tables 211 to 213 constituting the first color conversion means, and yellow Y ', magenta M' , Cyan C '(compressed print data). The compressed print data Y ', M', and C 'are supplied to the color masking device 220 and converted into red R, green G, and blue B image data (display data).

The look-up tables 211 to 213 store compressed print data Y ', M', and C ', respectively, and use the print data (Y and K), (M and K), and (C and K) to compress each data. The print data Y ', M', and C 'are referred to.

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

First, color patches of each combination based on 8-bit Y ', M', and C 'image data are measured, X, Y, and Z color system values are obtained, and L ^* , u ^* , and v ^* tables are obtained. Find the value of the color system.

In this case, five quantization levels of 0.64, 128, 192, and 255 are taken for each of the image data of Y ', M', and C ', and a color patch (5 × 5 × 5 = 125) of a combination of these quantization levels is obtained. (Shown in FIG. 2).

Then, the color patches are measured by a colorimeter, and the values of the X, Y, Z color system are obtained as follows, and the values of the L ^* , u ^* , v ^* color system are obtained as follows.

Here, the middle of 5 × 5 × 5 = 125 is interpolated to 9 ×
9 × 9 = 729. Although color patches of 9 × 9 × 9 = 729 may be printed to measure the colors, the number of measurements increases and it takes time.

In this way, the values of the L ^* , u ^* , v ^* color system are Y ', M',
It is obtained for 9 × 9 × 9 = 729 colors based on the image data of C ′. FIG. 3 shows the values in the L ^* , u ^* , v ^* color system, which will be hereinafter referred to as a printing color solid.

Then, Y, M, C, and colorimetry color patches by each combination of image data of K, X, Y, determine the value of Z color system, further L ^*, u ^*, v ^* color system Find the value.

In this case, 0,64,128,192,255 for equivalent Y, M, C
In addition to the five quantization levels described above, the color patch is created by taking the image data of K at the levels of 0, 64, 128, 192, and 255 for each. That is, as shown in FIG.
5 × 5 = 25 color patches are created.

Then, the color patch is measured in the same manner as in the above process, the values of the X, Y, Z color system are obtained, and the values of the L ^* , u ^* , v ^* color system are obtained.

Next, Y ′, M ′, C ′ are set so that all the values of the L ^* , u ^* , v ^* color system obtained in the above are included in the color solid by the combination of Y ′, M ′, C ′. of the L ^* value to lower the minimum value of the color solid of L ^* value in advance in proportion extended to low L ^* value side,
A combination of the image data of Y ', M', and C 'corresponding to the values of the L ^* , u ^* , v ^* color system obtained in the above is calculated.

That is, the color of each combination of Y, M, C and K (5 × 5
= 25), the values of the L ^* , u ^* , v ^* color system are given as target values T ', and Y', M ', C'
Find the value of

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

FIG. 5 shows a Y, M coordinate system. When each grid point (for example, 5 × 5 = 25) is mapped to the L ^* , u ^* , v ^* color system by the processing shown in FIG. 6, as shown in FIG. Become. FIG. 7 shows a combination of Y, M, C and K (5 × 5 = 25) mapped to the L ^* , u ^* , v ^* color system by the processing of FIG.

First, the values of the L ^* , u ^* , v ^* color system for each combination of the image data of Y, M, C and K are given as target values T '(see FIGS. 6 and 7).

In this case, when the target value T 'is in the area surrounded by the lattice points a' to d 'as shown in FIG. 6, the combination of the Y' and M 'in the Y and M coordinate systems (the target value T) Is assumed to be in the area surrounded by the lattice points a to d as shown in FIG.

The location of the target value T in the area formed by the lattice points a to d is determined by performing convergence calculation processing while associating the color system of FIG. 6 with the coordinate system of FIG. The convergence calculation process is performed in such a way that, although the conversion from the coordinate system of FIG. 5 to the color system of FIG. 6 is known, the reverse conversion is very complicated and is still good. This is because the conversion formula is not known.

The target value T 'is determined as to which of a plurality of regions formed by the 25 grid points (see FIG. 6).
When it is in the area S0 'as shown in FIG. 9, it is estimated that the target value T is in the area S0 corresponding to the area S0' as shown in FIG.

Next, the estimated area S0 is equally divided into four areas S1 to S4. The five division points e to i are calculated by weighted averaging using surrounding grid points that have already been obtained. Then, values obtained by converting the values corresponding to the division points e to i into the L ^* , u ^* , v ^* color system are plotted in the color system of FIG. 9, and the plotted division points e 'to It is determined which of the four areas S1 'to S4' formed by i 'has the target value T'. When it is in the area S2 'as shown in FIG. 9, the target value T is in the area S2 corresponding to the area S2' as shown in FIG.
It is estimated that

Next, the estimated area S2 is equally divided into four areas S5 to S8. The five division points j to n are calculated by weighted averaging using surrounding grid points and division points that have already been obtained. Then, values corresponding to the division points j to n are represented by L ^* ,
The values converted to the u ^* , v ^* color system are plotted in the color system of FIG. 9 and among the four regions S5 'to S8' formed by the plotted division points j 'to n'. In which area the target value T 'is located is determined. As shown in FIG. 9, the region S8 '
, The target value T is in the region S as shown in FIG.
It is estimated that it is in the area S8 corresponding to 8 '.

Next, the estimated area S8 is equally divided into four areas S9 to S12. The five division points o to s are calculated by weighted averaging using surrounding grid points and division points that have already been obtained. Then, values corresponding to the division points o to s are represented by L ^* ,
The values converted to the u ^* , v ^* color system are plotted in the color system of FIG. 9, and among the four areas S9 'to S12' formed by the plotted division points o 'to s'. In which area the target value T 'is located is determined. As shown in FIG.
When it is at 0 ', it is estimated that the target value T is in the area S10 corresponding to the area S10' as shown in FIG.

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

Using the values of Y ', M', and C 'for the combination of Y, M, and C equivalents and K obtained as described above, Y' is derived from Y and K, and M 'is derived from M and K. , C and K, the conversion from Y, M, C, K to Y ', M', C 'is performed.

As described above, the image data of Y ', M', and C 'for the combination of the quantization levels of 0, 64, 128, 192, and 255 of Y, M, C, and K are obtained. The image data of M 'and C' are interpolated by interpolation.

That is, the interpolation processing is performed based on data of four grid points including points to be interpolated. In this interpolation processing, as shown in FIG. 10, when an input (Y, K) is given, a weighted average of four grid points surrounding the input (Y, K) is calculated. For example, in the case of the point U, the output of each point of the lattice points e, f, g, and h is multiplied by a weight coefficient to obtain the point U '.

The above interpolation processing is performed for each point of the quantization level of 0 to 255 excluding the lattice points, and Y ′ image data corresponding to all the points of the input (Y, K) is calculated.

M ′ corresponding to all points of the input (M, K) and (C, K),
The same applies to C ′.

The image data of Y ', M', and C 'obtained by the above processes (1) and (2) are respectively stored in lookup tables.
They are stored in 211, 212 and 213, respectively, and are referred to by (Y, K), (M, K) and (C, K), respectively.

Also, in the color masking device 220 in FIG. 1, the display data R, G, B are obtained from the compressed print data Y ', M', C '.
It is conceivable to provide a look-up table to obtain That is, the display data R, G, and B are stored in the lookup table, and the display data R, G, and B are referred to by the compressed print data Y ', M', and C '.

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

First, a color patch based on each combination of R, G, and B image data is displayed on a television display to measure the color, and X, Y,
The value of the Z color system is obtained, and the value of the L ^* , u ^* , v ^* color system is further obtained.

In this case, for each of the R, G, B image data, 0, 64,
The five quantization levels of 128, 192, and 255 are taken, and the colors (5 × 5 × 5 = 125) of each combination are displayed one by one on a television display, and the colors are measured one by one using a spectroradiometer. The values of the X, Y, Z color system are obtained, and the values of the L ^* , u ^* , v ^* color system are obtained.

In this equation, Xn, Yn, Zn are x, y of standard light D65
X, Y, and Z values. The relationship between x, y and X, Y, Z is as follows.

x = X / (X + Y + Z) y = Y / (X + Y + Z) Since the value of D65 is x = 0.3127 and y = 0.3290, Xn,
Yn and Zn satisfy the following equations.

Xn / (Xn + Yn + Zn) = 0.3127 Yn / (Xn + Yn + Zn) = 0.3290 The level of the absolute value of Xn, Yn, Zn must be determined. When (R = G = B = 255) is displayed, Yn is made substantially equal to Y of X, Y, Z values.

It should be noted that the intermediate of 5 × 5 × 5 = 125 is interpolated to 9 × 9
× 9 = 729. Color measurement may be performed by displaying 9 × 9 × 9 = 729 colors, but the number of measurements increases and it takes time.

In this way, the values of the L ^* , u ^* , v ^* color system are obtained for 9 × 9 × 9 = 729 colors based on the R, G, B image data.
The values of the L ^* , u ^* , v ^* color system are defined as L ^* out u ^* out v ^* out. FIG. 11 shows the values in the L ^* , u ^* , v ^* color system, which will be hereinafter referred to as the color solid of the television display.

Next, using the values of the L ^* , u ^* , v ^* color system obtained by measuring the color patches of each combination of the image data of Y ', M', and C ', Y', M ' , C ′ each 0,8,16, ・ ・ ・, 24
When the 32 quantization levels of 0,248 are taken, the L ^* , u ^* , and L ^* of the color (32 × 32 × 32 = 32768) by each of these combinations
v ^* The value of the color system is determined by interpolation through interpolation.

The values of the L ^* , u ^* , v ^* color system are defined as L ^* in1 u ^* in1 v ^* in1.

Next, as shown in FIG. 12, in the color reproduction from color hard copy to a color television display, the obtained by processing L ^*, u ^*, v ^* color system value L ^* out, u ^* o
Color reproduction range by ut, v ^* out (output side color reproduction range) Lout
Is wider than the color reproduction range (input-side color reproduction range) Lin based on L ^* , u ^* , v ^* color system values L ^* in1, u ^* in1, v ^* in1 obtained by general processing. Therefore, the values L ^* in1, u ^* in of the color system obtained by the processing of such that the input-side color reproduction range Lin is expanded in accordance with the ratio of the input-output-side color reproduction range.
1, v ^* in1 is enlarged and mapped.

In this example, when performing the enlargement mapping, the brightness direction is linearly mapped so as to match the range, and the saturation direction is not mapped at the center of the overlapping portion of the input / output color reproduction range, Only the part is transformed.

In this case, L ^* , u ^* , v ^* color system values L ^* , u ^* , v ^* are
Mapping is performed by converting into lightness L ^* , saturation C ^*, and hue θ according to the following equation.

[Conversion in the lightness direction] Linear conversion is performed by the following equation so as to match the entire range.

Here, L ^* in1 is the value of brightness before conversion, and L ^* in1 is the value of brightness after conversion.

L ^* outmax and L ^* outmin are the maximum value and the minimum value on the L ^* axis of the output-side color reproduction range Lout, respectively (see FIG. 13). L ^* outmax is the value of L ^* out when measuring white color displayed on the television display with R = G = B = 255. L ^* outmin is the value of L ^* out when measuring black color displayed on the television display with R = G = B = 0.

Further, L ^* in1max and L ^* in1min are the maximum value and the minimum value on the L ^* axis of the input-side color reproduction range Lin, respectively (see FIG. 13). L ^* in1max is the value of L ^* in1 when a white background color patch is measured with Y = M = C = 0. L ^* in1min is a value of L ^* in1 when a black color patch printed at Y = M = C = 255 is measured.

[Conversion of saturation direction] After converting the lightness as described above, u ^* in1, v ^* in1
The saturation ^{C *} in1 by, to convert to color saturation ^{C *} in2.

In this case, the input-side color reproduction range in Lin, the value C ^* in 2/3 of the maximum value C ^* INmax and 2/3 of the saturation in the corresponding brightness and hue saturation C ^* in1 to be converted (See FIG. 14).

Further, within the output-side color reproduction range Lout, the maximum value C ^* outmax of the saturation at the lightness and hue corresponding to the saturation C ^* in1 to be converted is obtained (see FIG. 14).

Then, the saturation C ^* in2 is obtained as follows.

When C ^* in1 ≦ C ^* in 2/3, C ^* in2 = C ^* in1. When C ^* in1> C ^* in 2/3, And

Note that C ^* inmax (Y ', M', C ') is obtained as follows. C ^* outmax (R, G, B) can be obtained in the same manner.

That is, of the values of the L ^* , u ^* , v ^* color system for each combination of the image data of Y ', M', and C ', only the value of the combination which is the outer surface of the color solid is represented by the lightness L ^* , chromatic The degree C ^* is converted into the hue θ and stored in the memory. Incidentally, there are eight surfaces which become the outer surfaces of the color solid, which are the surfaces in which any of the Y ', M', and C 'image data becomes 0 or the maximum.

Then, as shown in FIG. 15, a position on the grid containing the lightness L ^* and the hue θ corresponding to the saturation C ^* in1 to be converted is searched, and the saturation C ^* of the four surrounding points is found. C ^* inmax is obtained by weighted averaging from the values.

Lightness L ^* in2 and chroma C obtained as described above
^* In2 (hue θ does not change) is converted to a value of L ^* , u ^* , v ^* color system. The L ^* ,
u ^* , v ^* color system value L ^* in1, u ^* in1, v ^* in1 is L ^* in2, u
^* In2, v Enlarged mapping to ^* in2.

Then, in the obtained ^{L *, u *, v *} color system of value ^{L *} in
A combination of R, G, B image data corresponding to 2, u ^* in2, v ^* in2 is calculated.

That is, the color of each combination of Y ', M', and C '(32 × 32
× 32 = 32768) L ^* in2, u ^* in2, v
^* In2 is given as a target value T ′ to the color solid (shown in FIG. 11) of the television display, and Y ′,
The values of R, G, and B for each combination of M 'and C' are obtained. The convergence calculation is the same as that described with reference to FIGS. 5 to 9, and a description thereof will be omitted.

Y ', M', C 'obtained by the above processing
Are stored in a look-up table (LUT) in the color masking device 220, and are referred to by the image data of Y ', M', and C ', respectively. Become.

Next, an example of the color masking device 220 for obtaining R, G, B image data from Y ′, M ′, C ′ image data will be described.

By the way, if R, G, and B image data corresponding to all combinations of Y ', M', and C 'image data are stored in the LUT, the capacity of the LUT becomes enormous.

In order to reduce the memory capacity, the present applicant divides the color space formed by the image data of Y ', M', and C 'into a plurality of basic lattices, and the LUT is located at the apex thereof. R, G, B for the combination of Y ', M', C 'image data
When there is no R, G, B image data for the combination of Y ', M', C 'image data, the image data of Y', M ', C' (interpolation points) It is proposed to obtain the R, G, B image data by the weighted average of the R, G, B image data of the vertices of the basic lattice containing.

In this sense, as described above, R, G, B corresponding to 32 × 32 × 32 = 23,768 combinations of image data of Y ′, M ′, C ′.
Is obtained, and this is stored in the LUT.

For example, as shown in FIG. 16, when an interpolation point P exists in a basic lattice formed of vertices A to H, each vertex at the diagonal position and the interpolation point P are formed with respect to that vertex. The volume of the rectangular parallelepiped is used as a weighting factor for the image data of R, G, and B at vertices A to H.

That is, the vertex A of the basic lattice including the interpolation point P
To H, R, G, B image data Ri, Gi, Bi (i = 1 to 8),
The weighting factors for the image data of vertices A to H for R, G, B are Ai
If (i = 1 to 8), the image data Rp, Gp, Bp of R, G, B at the interpolation point P is calculated by the following equation.

In such interpolation processing, when image data Rp, Gp, and Bp of R, G, and B at interpolation points are calculated, eight multiplication and accumulation processes are required for each.

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

As shown in FIG. 17, a total of six triangular pyramids are formed by dashed lines with respect to the basic lattice constituted by vertices A to H. When the coordinates of the interpolation point P are (5, 1, 2), it is understood that the interpolation point P is included in the triangular pyramid T formed by the vertices A, B, C, and G as shown in FIG.

When the triangular pyramid T is determined, as shown in FIG. 18, the interpolation point P and the vertices A, B, C, and G are connected to form a total of four new triangular pyramids. Volume of VBCGP, VACGP, VABG
P and VABCP are required. These volumes and the vertices A, B, C, G R,
From the G and B image data RA to RG, GA to GG, and BA to BG, the R, G, and B image data Rp, Gp, and Bp of the interpolation point P are calculated by the following equations.

 VABCG is the volume of the triangular pyramid T.

Rp = 1 / VABCG (VBCGP · RA + VACGP · RB + VABGP · RC + VABCP · RG) Gp = 1 / VABCG (VBCGP · GA + VACGP · GB + VABGP · GC + VABCP · GG) Bp = 1 / VABCG (VBCGP · BA + VACGP · BC + VACGP · BC + BB · BC + BB · BB (2) If the coordinates of the interpolation point P are different, the triangular pyramid T used will also be different. For example, if the coordinates of the interpolation point P are P (3,1,
In the case of (5), since the interpolation point P is included in the triangular pyramid T formed by the vertices A, C, D, and G as shown in FIG. 19, the triangular pyramid T is used.

As described above, in the interpolation processing using the triangular pyramid, the image data Rp, Rp,
Gp and Bp can be calculated.

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

In the figure, reference numeral 20 denotes a color correction data storage unit, and a look-up table (MLUT) constituting the storage unit 20
21R to 21B store R, G, and B color correction data, respectively.

By the way, as the MLUTs 21R to 21B, for example, a ROM having a capacity of 256K bits is used, and only 32 points between the minimum level and the maximum level of the image data of Y ', M', and C 'are extracted as described above. 32 × 32 × for each of MLUT21R ~ 21B
32 = 32768 image data are stored.

In this case, the image data of Y ', M', and C 'is 8 bits and has 256 gradations. The distribution of 32 points is, for example, divided from "0" by "8" in the order of 0,8,16. , ..., 240, 248 are equally divided so that the total is 32, and it is the 33rd point
249 to 255 are not used or treated as 248.

Image data of R, G, and B at the vertices of the basic lattice in which each of the distribution points, that is, the basic lattice interval is 8 quantization levels, is calculated by the above-described processing, and the calculated image data is MLUT21R ~ 21B.

Reference numeral 60 denotes a look-up table (WLUT) constituting the weight coefficient storage means. The WLUT 60 stores a weight coefficient corresponding to each interpolation point.

In the case of the interpolation processing using a cube, when the basic lattice spacing is 8 quantization levels as described above, the total of the eight weighting coefficients is 8 × 8 × 8 = 512, which is 256. Is normalized so that In addition, the maximum value of the weight coefficient is set to 255 so that an 8-bit general-purpose IC can be used as the WLUT 60. For example, when the interpolation point P is located at the same position as the vertex A in FIG. 16, the weighting factors P1 to P8 are as follows.

 P1, P2, P3, P4, P5, P6, P7, P8 255,0,0,0,0,0,0,1 (512,0,0,0,0,0,0,0) The sum of the coefficients is always 256.

Further, in the case of the interpolation process using the triangular pyramid, when the basic lattice interval is 8 quantization levels as described above, the sum of the four weighting coefficients is 8 × 8 × 8/6 = 512/6. Which is normalized to 256. In addition, the maximum value of the weight coefficient is set to 255 so that an 8-bit general-purpose IC can be used as the WLUT 60. For example, when the interpolation point P is located at the same position as the vertex A in FIG. 17, the weighting factors VBCGP, VACGP, VABGP, VABCP are as follows.

 VBCGP, VACGP, VABGP, VABCP 255,0,0,1 (512 / 6,0,0,0), and the sum of the weighting factors is always 256.

The image data of Y ', M', and C 'are used as address signal forming means.
The look-up tables (PLUTs) 41Y to 41C that constitute the 40 are supplied to the PUTs 41Y to 41C.
A distribution signal is supplied from 50.

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

In the case of the interpolation processing using a cube, eight vertices of the basic lattice including the interpolation point P are determined based on the distribution signal.
As sequentially specified by the MLUTs 21R to 21B, 5-bit address signals are sequentially output.

In the case of the interpolation process using the triangular pyramid, four vertices of the triangular pyramid including the interpolation point P are ML based on the distribution signal.
As sequentially specified by the UTs 21R to 21B, 5-bit address signals are sequentially output.

R, G, B image data output from MLUT21R-21B is
Multipliers (MTL) 31R constituting the multiplication / accumulation means 30, respectively
Supplied to 31B.

From the PLUTs 41Y to 41C, the lower 3 bits of the image data of Y ', M', and C '(representing the position of the interpolation point P in the basic grid)
Is output as a weight coefficient designation signal, and this weight coefficient designation signal is supplied to the WLUT 60. A distribution signal is supplied from the controller 50 to the WLUT 60, and a weight coefficient is sequentially output based on the distribution signal.

In the case of an interpolation process using a cube, eight weighting factors P1 to P8 are sequentially output in correspondence with the eight vertices of the basic lattice including the interpolation point P being sequentially specified by the MLUTs 21R to 21B. Is done.

In the case of the interpolation process using the triangular pyramid, four weighting factors are sequentially output in correspondence with the four vertices of the triangular pyramid including the interpolation point P being sequentially designated by the MLUTs 21R to 21B. .

The weight coefficients output from the WLUT 60 are supplied to the MTLs 31R to 31B. And in this MTL31R-31B, MLUT21R-21B
R, G, B image data (8 bits) output from WLU
Multiplication with the weight coefficient (8 bits) from T60 is performed.

The multiplied outputs of the upper 8 bits of the MTLs 31R to 31B are supplied to accumulators (ALUs) 32R to 32B, respectively, where they are added.
A reset signal is supplied from the controller 50 to the ALUs 32R to 32B.

In the case of an interpolation process using a cube, an addition process is sequentially performed corresponding to the eight vertices of the basic lattice including the interpolation point P, and the result is reset each time the result is latched by a latch circuit described later. Is done.

In the case of an interpolation process using a triangular pyramid, an addition process is sequentially performed corresponding to four vertices of the triangular pyramid including the interpolation point P, and each time the result is latched by a latch circuit described later. Reset.

As described above, the sum of eight weighting factors in the case of interpolation using a cube and the sum of four weighting factors in the case of interpolation using a triangular pyramid become 256. Have been. In this example, the higher 8 bits of the multiplication output of the MTLs 31R to 31B are used, and a so-called 8-bit shift is performed. And the processing of 1 / VABCG in equation (2) is performed.

Outputs of the ALUs 32R to 32B constituting the multiplication / accumulation means 30 are supplied to latch circuits 71R to 71B, respectively. A latch pulse is supplied from the controller 50 to the latch circuits 71R to 71B.

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

In the case of the interpolation processing using the triangular pyramid, the result of the sequential addition processing corresponding to the four vertices of the triangular pyramid including the interpolation point P is latched.

Therefore, from the latch circuits 71R to 71B, the interpolation processing using a cube is represented by equation (1), and the interpolation processing using a triangular pyramid is represented by equation (2). The image data of R, G, B at the interpolation point P to be output is output.

In the present embodiment, the basic colors of the color separation image of the color hard copy are described as four colors of Y, M, C, and K.
This method can be similarly applied to the case of three colors of Y, M, and C. In that case, the data of Y, M, C can be used directly for Y ', M', C ', and in that case, Y', M ', C' are obtained from Y, M, C, K. Part will be removed.

In the method of this example, the color system value L ^* in1, u obtained for the image data of Y ', M', C 'according to the ratio of the color reproduction ranges Lin and Lout on the input and output sides. ^* In1, v ^* in1 is enlarged and the value L ^* in2, u ^* in obtained by this enlarged mapping is obtained.
Since the image data of R, G, B is obtained corresponding to 2, v ^* in2, the color reproduction by the image data of R, G, B is the color reproduction range of the TV display by the image data of R, G, B. It can cover the entirety and can have a sufficient range of brightness and saturation. That is, a television image having a sufficient contrast and vividness can be reproduced.

In the above embodiment, the conversion in the brightness direction is performed linearly. However, the present invention is not limited to this. In some cases, the conversion may be performed nonlinearly.

In the above embodiment, L ^* , u is used as the color system.
^* , V ^{* The} color system is used, but instead of R, G,
The same can be applied to those using other color systems such as the B color system, the X, Y, Z color system, the L ^* , a ^* , b ^* color system.

[Effects of the Invention] As described above, according to the present invention, the input color separation image information is obtained such that the input color reproduction range is expanded in accordance with the ratio of the color reproduction ranges on the input and output sides. Since the color system values are enlarged and mapped and the output color separation image information is obtained in correspondence with the enlarged and mapped color system values, the color reproduction based on the obtained output color separation image information is output color reproduction. This covers the entire range, and can have a sufficient range of brightness and saturation.

[Brief description of the drawings]

1 to 15 are diagrams for explaining a color estimation method according to the present invention, FIGS. 16 to 19 are diagrams for explaining an interpolation process,
FIG. 20 is a configuration diagram of a color masking device, and FIG. 21 is a diagram for explaining a conventional method. 100 TV display 200 Color separation image correction device 220 Color masking device

Claims (2)

(57) [Claims] 1. A color system value for each combination of a plurality of input color separation image information is determined, and a color system value for each combination of a plurality of output color separation image information is determined. Using the color system value obtained for each combination of the separated image information, the same value as the color system value for the arbitrary combination of the input color separated image information or the value of the color system is used. In the color estimation method for obtaining the combination of the output color separation image information to obtain the value obtained by the above, the output color reproduction range based on the color system value obtained for each combination of the plurality of output color separation image information is When the input-side color reproduction range is wider than the input-side color reproduction range based on the color system value obtained for each combination of the plurality of input color separation image information, the input-side color reproduction is performed according to the ratio of the input-output color reproduction range. Range In order to increase the value of the color system obtained for each combination of the input color-separated image information, the output is obtained by enlarging and mapping the same color system value as the enlarged mapped color system value. A color estimating method characterized by determining a combination of color separation image information. 2. When performing the above-mentioned enlarged mapping, linear or non-linear mapping conversion is performed so as to adjust the range in the brightness direction, and in the chroma direction, the center of the overlapping portion of the input / output color reproduction ranges is 2. The color estimating method according to claim 1, wherein only the peripheral portion of the color is converted without performing the mapping conversion.