JPS63254887A - Color patch forming method - Google Patents

Abstract

PURPOSE:To obtain the plural colors of the different combinations of signals as the color patch image on a recording medium by mixing plural basic colors based on a color separation picture signal inputted as an electric signal and reproducing on the recording medium as a color picture. CONSTITUTION:A 8 bit interval and a 9 bit interval are distributed in a mixed form as a lattice point. Since the maximum distance between the lattice points is 9 bits, the data of four bits is supplied to a weight coefficient storing means 24 side from an address signal forming means 40 as a weight coefficient referring address signal corresponding to this distance. A control signal for sequentially selecting chips a control terminal is supplied to LUTs 21-23 for color correcting data and the color correcting data is read in the sequence of the LUTs 21-23 and supplied to a multiplying and accumulating means 30. In the means 30, the corrected values of the respective colors are sequentially calculated and the data of high order 8 bits of the accumulated output is sequentially outputted for every color.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to color correction between different color systems, such as when making a hard copy of a television image signal using a video printer, digital color copying device, etc. This invention relates to a color patch creation method suitable for application to color measurement systems such as color proofing.

[Background of the Invention] When making a hard copy of a television image signal using a video printer, digital color copying device, etc., each color system is different. Color separation image correction devices are often used for color correction of patches and the like.

For example, a color masking device, which is one of the color separation image correction devices, cancels the side absorption of coloring materials (toner, ink, thermal transfer ink, pigments of photographic paper, etc.) to produce correct colors. This is a device that makes it possible to reproduce intermediate colors.

That is, a color image of a television image is constructed by an additive color method, and the R, G, B coordinate system of the phosphor can be used as the color system. On the other hand, with photographic paper, etc., a color image is constructed using the subtractive color method, and its color system is L", u", v.
A color system such as ' is used. In such a case, it is necessary to convert signal data (color correction) between these color systems.

For example, in the color masking device 10 shown in FIG. 25, new image data (color-corrected image data, in this example, Cyan, magenta M, and yellow Y) are formed, and a color image is recorded based on the new image data C, M, and Y.

In the figure, 11 is a television receiver, 12 is a color printer, and 13 is a recording medium such as photographic paper.

If you can accurately understand the color characteristics of a color printer, etc.
Since the combination of basic colors (three or four colors) that reproduces a specified color can be accurately determined, color conversion errors are minimized and color reproducibility is significantly improved.

The following two methods are conventionally known as methods for calculating a combination of basic colors (three or four colors) that reproduces a specified color.

When making hard copies using photographic paper, etc., the second
As shown in Figure 6, the spectral absorption density of each monochrome (Y, M, C) is measured, and the overall absorption characteristic is calculated using density additivity. After that, X.

Convert to a color system such as Y, Z, L'', u'', v''.

Density additivity refers to a method of calculation by adding the densities of each color at each spectral absorption density.

In printing, etc., basic color combinations are estimated using the Neugebauer equation.

[Problems to be Solved by the Invention] By the way, among the above-mentioned calculation methods, in the case of photographic paper, density additivity does not hold in an actual system.

Therefore, the accuracy when estimating color reproducibility is poor.

Even when the Neugebauer equation is used, since it is an approximate equation, there is a large discrepancy between the approximate equation and the actual value, and the accuracy of color reproducibility is also insufficient.

One possible way to solve this problem is to directly record a color image from a TV image signal onto a recording medium such as photographic paper, directly measure the color of the recorded image, and calculate a correction value. .

In this way, the present invention proposes a color patch creation method suitable for use in cases where a color image is actually formed and values of different color systems are calculated.

[Technical Means for Solving the Problem] In order to solve the above-mentioned problem, the present invention mixes a plurality of basic colors based on a color-separated image signal input as an electric signal, and mixes a plurality of basic colors on the recording medium. The present invention is characterized in that a color image reproducing apparatus that reproduces a color image ' as a color image reproduces a plurality of colors resulting from different combinations of color separation image signals as a color patch image on a recording medium.

[Operation] A color image is formed by an image signal based on a combination formed by the minimum to maximum levels of basic colors given as color separated image signals.

This color image formed on the recording medium can be used as a color patch image.

When there are m basic colors and each of them is divided into n steps, a color patch image consisting of nff1 combinations is obtained.

Even if there are m basic colors, each step may not be divided at equal intervals. In that case, classification will be done taking into consideration the discrimination ability of the human eye.

The human eye's discrimination ability is the highest for magenta M and the lowest for yellow Y. Therefore, if the steps of yellow Y are roughly divided and the steps of magenta M are finely divided, it is better than simply dividing by n steps. , the number of color patches decreases.

When considering the discrimination ability of the human eye, Y.

The number of signals PY and PM used for the combination of M and C.

The PC is PY<PC≦PM is selected so as to satisfy the relationship.

Note that the following processing steps can be considered in order to create a color patch and calculate the mixing amount of basic colors.

First, there is a step (first step) of outputting in advance a plurality of samples of tone close to the desired intermediate color.

Second, there is a step (second step) of checking the mixing amount of the basic colors of each sample and the corresponding color system value.

Thirdly, there is a step (third step) of performing a convergence calculation using the values of the sample color system.

Through this third step, the amount of mixture of basic colors that reproduces the intermediate color is calculated.

The samples in the first step are determined as follows.

It actually prints color on photographic paper using signals from n discrete points (the total is n'nψn points) regarding the basic colors made up of a specific color system, e.g. Y, M, C coordinate system. Thus, nW' color patch images are formed.

The colors of multiple color patches formed by color printing are actually measured, and the constant data is compared to the color system of photographic paper (
For example, by plotting on the L", u", V" color system, the same applies hereafter), the colors in the Y, M, C coordinate system
They are mapped as values in the '+v' color system. These mapped values become sample values.

In order to convert the measured data into values of a specific color system, a specific conversion formula for that color system is used.

In the third step, the sample value closest to the intermediate color is calculated by sequentially interpolating and converging the sample values. The converged sample value is the mixture amount of basic colors (Y, M
, C).

A plurality of these mixing amounts are prepared as color correction data, and these are referenced by input color information.

In the color separation image correction device, these color correction data are made into a table, and the corresponding color correction data is referred to based on the input color separation image information.

This allows a color image to be recorded based on the modified color separation image information. , [Example] Next, an example of the method for forming a color patch according to the present invention will be described in detail with reference to FIG.

First, the basic principle of the color separation image correction method to which this invention is applied will be explained.

For convenience of explanation, a case will be explained in which three basic colors are Y, M, and C.

Intermediate colors on a recording medium, such as a color photosensitive material such as photographic paper, can be expressed in an infinite number of ways by combining Y, M, and C densities, and the range of expression is shown three-dimensionally. Y, M,
When expressed in the coordinate system of C, the expression range becomes a cube as shown in FIG.

The Y, M, C coordinate system may be changed to another color system, for example, X, Y.

When converted to a two-color system, it becomes a solid as shown in FIG.

In the figure, each vertex A-H corresponds to A'-H'.

As is clear from FIG. 2, most of the solid objects that determine this expression range are distorted, each side is not necessarily a straight line, and each side is a complex curved surface.

Within this solid, a predetermined intermediate color can be reproduced by an appropriate combination of Y, M, and C. Therefore, color correction data must be created to fit within this three-dimensional space.

This invention proposes a method for determining the mixing amounts of Y, M, and C so that they fit into this three-dimensional space.

For simplicity, the basic colors will be explained as two colors (for example, Y and M), and then the algorithm using the original basic colors will be explained.

Each intersection point in Figure 3 (in the example, 5x5=25 grid points)
The color level is supplied to a color printer, and the color level is recorded on a recording medium (hereinafter referred to as photographic paper) to form a color patch.

The actual color was measured from the obtained color patch, the measured value was converted to a color system value (sample value) using the color system conversion formula, and this was plotted for each grid point. This is shown in Figure 4.

Although it is better to have a large number of color patches, since actual color measurement takes time, in this embodiment, about 5×5=25 color patches can be used.

You may use as many color patches as you like.

In that case, the number of color patches may actually be increased, but it is also possible to increase the number of color patches by interpolation processing. For example, if you interpolate the middle of 5X5=25 color patches, this interpolation process will result in 9X9=8
This means that it has been expanded and multiplied to the color patch of 1.

In the example shown below, the combination of basic colors is estimated using 5×5=25 color patches.

Although the color patch setting described above does not take human perceptual characteristics (discrimination ability) into consideration, the number of color patches may be selected in consideration of human perceptual characteristics, as will be described later.

Here, as shown in FIG. 4, if a certain intermediate color is indicated by x (target value T'), then Y indicates this color.

The combination of inter-coordinate systems is estimated to be within the area surrounded by grid points a-d in FIG.

The calculation process for determining which lattice point is closest is determined by converging the color system shown in FIG. 4 while correlating it with the coordinate system shown in FIG. 3.

In this way, the reason for performing convergence calculations using only the color system in Figure 4 and not estimating the convergence results by associating them with the coordinate system in Figure 3 is to change the coordinate system in Figure 4 from the coordinate system in Figure 3. This is because although the conversion to the color system is known, the reverse conversion operation is very complicated, and the preferred conversion formula is not yet known.

For this reason, the target value T shown in the coordinate system of FIG. 3 is estimated by the following process. The estimation processing operation will be explained in detail with reference to FIGS. 5 and 6.

First, using the target value T' and a total of 25 basic grid points (see FIG. 4), the grid point closest to this target value 1'' is calculated.

Actually, the grid point where the difference between the two is the minimum is calculated.

Assuming that this grid point is b', it can be estimated that the lower target value in FIG. 5 is close to the grid point corresponding to grid point b'.

Next, a total of nine lattice points surrounding the lattice point S are set at level intervals where the lattice point spacing is 1/2, and these lattice points are calculated by the weighted average of the surrounding lattice points. For example, it is determined by weighted averaging of two or four surrounding grid points.

The value corresponding to this newly calculated grid point e=1 is plotted again on the color system shown in FIG.

Then, from among the plotted grid points e' to 1' (9 in total), the grid point closest to the target value T' is found by the same method as described above, and that grid point (in this example, h
The grid point in FIG. 5 corresponding to ') and the eight grid points m-t including this are calculated by further narrowing the grid interval to 1/2.

By repeating such grid division, the grid becomes progressively narrower and eventually converges. The target value T in FIG. 5 corresponding to the converged value of the grid point indicates the combination of basic colors (mixing amount of Y, M, and C) for reproducing the intermediate color.

The above estimation operation is executed for each given target value.

It is also possible to create a table of estimated target values and refer to the target values using the values of the input color separation image.

When actually applied to a color separation image correction device, etc.,
A lookup table will be used. An example of this will be described later.

The algorithm when three colors are used as basic colors will be explained below.

It is assumed that Y, M, and C each have a level of 256 steps from 0 to 255. Of these levels, five levels are extracted in this example. For example, Y, M,
0I64.128, 192 and 25 for each of C.
Five levels of 5 are extracted. Color patches of all these combinations of colors (5x5x5=125) are created.

An example of a color patch is shown in FIG. The color system of each color patch is CIE's L", u".

v ” % L ” + a ratio, b0 color system is suitable.

Color patches do not necessarily have the same number of levels for each color. That is, when a color patch is constructed taking into consideration the discrimination ability of the human eye, the number of levels is generally not the same for each color. This is because the human eye has the highest discrimination ability for M (magenta) and the lowest for Y (yellow).
This is because it is conceivable that Karaba Sochi would also have a smaller amount of Y and a larger amount of M.

FIG. 8 shows an example of this, and illustrates the case where Y-M-C=3X5X4. - In this way, when creating a color patch taking into account the discrimination ability of the eye, almost the same result as when forming a color patch by dividing each of Y, M, and C at equal intervals can be obtained.

As a result, the number of color patches is reduced, and the actual color measurement time is correspondingly shortened.

Generalizing these relationships, the numbers of patches PY and PM of Y, M, and C are set so that the following relationships are satisfied.

All you need to do is set up your PC.

PY<PC:ii+PM When increasing the number of color patches by interpolation processing, do as follows.

As a basic lattice, if 5X5X5=125, L"l
The u''+V'' color system is interpolated by curve interpolation shown in the following calculation formula.

In this case, as shown in Figure 9, if the black circle is a grid point (sample point) and the Δ mark and the X mark are the points to be interpolated, there are two grid points before and after the Δ mark. Different interpolation formulas are used for cases where there are one point and three points before and after the X mark.

The color system of the points to be interpolated is I, -, ui, ■-, and the color system of each sample point is Li〒, uf", vi" (
i=1 to 4), the former case is interpolated using the following interpolation formula.

LIll”= −(1/1B) Ll”+ (9/16
) L2”+ (9/16) L3゜-(1/1B)
L4゜u-=-(1/16) ul"+(9/16) u2"
+(9/16) u3”-(1/16) u 4゜V♂= (1/16)vl”+(9/1G)v2”+
(9/16)v3"-(1/16)v4" In the latter case, the following interpolation formula is used.

L ,,” = (5/16) L 1” + (15
/16) L2”-(5/16) L3”-(1/1
6) L4” U♂= (5/16) u 1”+ (15/16)
u2"-(5/16) u3"-(1/16) u4
”V♂= (5/16) v 1”+ (15/16)
v2” - (5/16) v3゜ (1/16) v 4
” An example of the order of interpolation processing is shown in FIG. 10.
Interpolation is performed in the order of II, Ill.

Through such interpolation processing, even though only 125 color patches are actually measured, the number of color patches can be expanded to 729 by electrical processing, which is indicated in the Y, M, C coordinate system at that time. The resulting color patch is as shown in Figure 11.

When this is mapped to the color system of L's ul, vl, the 12th
The result will be as shown in the figure.

Figure A is the color system seen from the apex side in Figure 11, Figure B is the mapping on the L", V" plane side, and Figure C is the color system seen from the vertex side of Figure 11.
This is a mapping on the u* surface side.

Using a total of 729 color patches created by such interpolation processing, the above-mentioned target value T estimation processing is executed.

Here, in order to calculate which grid point the target value T' is close to, E may be used in the following evaluation function.

8E= l LT"-Li"l + I uT"-ui
"1+ l v7"-vi" l ΔE= [(L7"-Li') 2+ (uT'-ui
``)''+ (v7'-vi'') 2J ``2 Any evaluation function may be used.

If the final target value T is calculated entirely by convergence calculation processing, the processing time will be too long, so
In reality, an algorithm is used that completes the process after several convergence processes.

For example, as in the example above, when the basic lattice spacing is divided by 64 quantization steps, the lattice spacing (division spacing) becomes 32 by the interpolation process described above. In such a case, an algorithm is used in which the convergence process is completed by sequentially repeating a total of five convergence processes with a grid spacing of 16.8.4.2.1.

This allows the target value to be estimated with sufficient accuracy.

When a color patch as shown in Figure 11 is obtained by interpolation processing, the interpolation points (each vertex of the solid) are calculated as described above in the first to fifth convergence processing. Although calculation can be performed by curved approximation, the following examples are all based on linear approximation.

The interpolation process using linear approximation is as follows.

Assuming an interpolation point S as shown in Fig. 13, the L*, u*, v m color system of the interpolation point S is expressed as L
An example of the interpolation formula when s ``*u s'', v s'' is shown below.

L s"= (1/EM l) DM I・sit'1
1＾ 1;＾ u s”= (1/DM ]) DM r ・u i”
1lAII＾ vs”= (1/AMi) TreatmentMi−vi”+I＾
1-^ The interpolated color system L s', u S"+v s" is Y.

It is associated with the values of the M, C coordinate system.

Mi is the volume of a rectangular parallelepiped that includes the diagonal vertices and the interpolation point S, and in the case of FIG. 11, M+=323 1^. A specific example of interpolation will be explained in the color segmented image estimation device described later.

By the way, in the above, we have explained the estimation process when both target values T are inside the solid shown in Fig. 2, but when they exist outside the solid as shown in Fig. 14, the following processing is used to estimate the target value T. Presumed. Y to simplify explanation
, M, and C coordinate systems are not used.

The reason why the target value T' exists outside the solid is that the color reproduction range of the output system is narrower than the color reproduction range of the input system.

In this case, move the color in the achromatic direction without changing its hue, and use the color at the point where straight line 1 in the achromatic direction intersects the boundary of the color reproduction range as its target value T4. It is something to do.

In this case as well, the target value T8 is considered to be on the line connecting the grid points q 1 + q 2 in Figure 3, and as described above, it is not associated with the Y, M, C coordinate system, so
q2'' (Fig. 14) is estimated by dividing and converging.

In addition to the above-mentioned algorithm, the following algorithm is added to the algorithm for this estimation operation.

First, when any one of Y, M, and C is O or maximum, it is determined that the target value T' is outside the solid, that is, outside the color reproduction range.

In that case, as shown in Fig. 15, assume a straight line passing through the target value T' and the achromatic axis (this is one point on the L6 axis),
The straight line (hereinafter referred to as convergence line) l and the inclination θ with respect to the u'' and v'' planes are expressed as follows.

1=ar+b θ=arc tan(ut”/VT”)Here, a,
b is an arbitrary real number and is different from a and b in FIG.

When setting not to change the brightness in addition to the hue, 1=LT''.

Next, the cylindrical coordinates (θ
, r, I)=(hue, saturation, brightness) and store it in memory.

Then, each sample point (
Among the lattice points indicated by black circles in FIG.

1i).

It is checked whether one of the four points always satisfies the following conditional expression.

θ≦θi≦θ+180' (i=1 to 4) θ-90°
≦θi≦θ+90' (i=1-4) θ-1800≦
θi≦θ (i=1~4) ar++b−It≧0(i=
1-4) a r l+ b -1+≦O (i ~1-4) When these conditions are satisfied, there is a high possibility that the convergence l111 passes through the set minimum quadrilateral.

It should be noted that although there are countless possible conditional expressions, the above-mentioned conditional expressions are examples that can be performed by simple calculations.

Next, this quadrilateral is calculated by weighted average from its vertices,
Find the midpoint indicated by the circle in Figure 16 and divide the outer surface into four parts.

The above-mentioned conditional expressions are referred to again for these four surfaces, and the same operation is repeated seven times thereafter. Then, the average value of the values of the Y, M, and C coordinate systems corresponding to this seventh vertex is used as the substitute value of the target value T.

Next, an example of a color separation image correction apparatus (color masking apparatus) embodying the above-described color separation image correction method according to the present invention will be explained in detail with reference to FIG. 17 and subsequent figures.

In this example, the target value calculated as described above,
In other words, the color correction data is a LUT (lookup table)
is stored in advance. For example, if the input system is a color CRT
In the case of , the color correction data of each grid point associated with the basic color coordinate system determined by B, G, and R (the same coordinate system as in Fig. 11) is stored, and the color correction data other than the grid points is stored inside. Calculated by interpolation.

When the number of input gradations or output gradations is small, all the color correction data can be stored in memory instead of the color correction data discontinuously like this.

Interpolation processing of corrected color data will be explained with reference to FIG. 17.

In this example, eight color correction data (corresponding to C, M, Y A rectangular parallelepiped spatial region V is defined using known calculated color correction data P1 to P8). Both of the spatial regions W and ■ have Pl as a reference point.

And for each color, 0.32.64, 96, 128, 160°192.22
It is assumed that there is a color correction value for each color combination at each point of 4,255 points.

At this time, the input image data R, G, B are respectively (100,
130, 150), it is interpolated using the color correction data of the vertices (lattice points) of the spatial area surrounded by the eight points shown below.

Here, Pi (i=1 to 8) on the left side indicates the coordinate value of each vertex of the spatial region V, and the right side indicates the color correction data Ci at that time.
r M i *Y i is shown.

Pl: (96,128,128)=(C1,Ml,Yl)P
2: (128, 128, 128) = (C2, M2.Y2)
P3: (96,160,128)= (C3,M3.Y3)P
4: (128, i6o, 128) = (C4, M4.Y4)
P5: (96,128,160)= (C5,M5.Y5)P
6: (128, 128, 160) = (C6, M6.Y6)
Pl: (96,160,160)=(C7,M7.Y7)P
8: (128, 160, 160) = (C8, M8.Y8)
Therefore, the relationship between the spatial area (2) formed by these eight vertices PL-P8 and the spatial area W that can be formed by the input image data is as shown in FIG.

The weighting coefficient for each vertex Pi of the spatial region V is calculated as follows.

As a method of calculating the weighting coefficient, the above-mentioned L"1u"
+v'' color system can be used.

In other words, the volume of the rectangular parallelepiped spatial region W formed by the interpolation point S and the vertex opposite to the point of the correction value to be obtained is used as the weighting coefficient at the point of the correction value to be obtained.

Therefore, the weighting coefficient of point P8 is determined by using the coordinates of Pl and S, from (100, 130, 150) - (96, 128, 128) = (4, 2, 22), The volume of the rectangular parallelepiped spatial region created by is 4X2X22=176, which becomes the weighting coefficient of point P8.

Similarly, weighting coefficients for the remaining points P1 to P7 are calculated.

P1=8400 P2=1200P3=560
P4= 80P5=18480 P6=
2640P7=1232P8=17 The sum of these weighting coefficients is the same as the volume of the cubic spatial region V, and in this example, is 32768 (assumed to be a).

Therefore, the correction values Cs, Ms, Ys at 8 points are Cs = 1/a (PIC1+P2C2+P3C3+P
4C4+P5C5+P6C6+P7C7+P8C8)M
s=1/a (PIM1+P2M2+P3M3+P4M
4+P5M5+P6M6+P7M7+P8M8)Ys=
'l/a (PIY1+P2Y2+P3Y3+P4Y4
+P5Y5+P6Y6+P7Y7+P8Y8).

In other words, the correction values of the 8 points surrounding the point S1 that we want to find are Ci, Mi, Yi (This is the interpolated value of the color system L S"i u S", VS"c) The corresponding Y, M,
C coordinate system) and can be expressed by respective weights.

The above-mentioned color correction data is just an example.

In reality, the number of color correction data is set to a power of 2, taking into account the capacity of the ROM, etc. Therefore, when using a 256-bit ROM, it is possible to have 32 points of color correction data for each color (323=32768 points for all three colors).

FIG. 18 shows an example of the color masking device 10.

As is clear from the above equation, this color masking device 10 includes a color correction information storage means (color correction data storage means) 20 that stores a plurality of color correction data, and an information storage means (color correction data storage means) for weighting.
24; a multiplication/accumulation means 30 for multiplying the referenced color correction data and the weighting coefficient and accumulating the values; and a processing means consisting of a division means. Of these, the division means can be omitted depending on the configuration.

The color correction data storage means 20 divides a color space formed by three-color separation image information that can be input for color correction into a plurality of spatial regions, and performs color correction on the combination of three-color separation image information located at the apex of the space. information is stored.

The weighting coefficient storage means 24 outputs information on weighting of a plurality of color correction data selected from the color correction information storage means based on the input three-color separation image information.

The processing means processes a plurality of pieces of color correction information selected from the color correction data storage means 20 based on the input color separation image information;
Based on the weighting coefficients, corrected color separation image data to be finally obtained is calculated and output.

FIG. 18 shows a case where the present invention is applied to a simultaneous color masking device that attempts to obtain three color correction data C, M, and Y at the same time, and FIG.
This is a case where the present invention is applied to a so-called sequential type color masking device that outputs eruptions of M and Y (for example, in this order).

Next, the configuration of each part of the simultaneous color masking device 10 shown in FIG. 18 will be explained.

20 is a color correction data storage means, in this example, each color c, M
, Y are fully stored in each of the LUTs 21-23. 24 is a weighting coefficient storage means, which is also L.
It is configured as a UT.

Address signals for reading are supplied to the color correction data storage means 2o and the weighting coefficient storage means 24, respectively. Therefore, the input image data B, G, and R are once supplied to the address signal forming means 4o, and an address signal corresponding to the input level is output.

The address signal output means can also be composed of LUTs 41 to 43, respectively. A bipolar ROM is suitable as the LUT. These LUTs 41 to 43 contain a controller 5.
The signal can be supplied for all bits from 0 to 1, but the details will be described later.

The color correction data and data indicating weighting coefficients (hereinafter simply referred to as weighting coefficients) referenced by the address signal corresponding to the input level of the input image data are sequentially supplied to the multiplication/accumulation means 30 a total of eight times.

As described above, the multiplication/accumulation means 30 is for sequentially executing AiKi (Ki is a general term for C, M, and Y) and calculating the sum thereof, and in this example, the multipliers 34 to
36 and accumulators 37-39.

Therefore, each multiplier 34-36 has 512 bits of RO
M are used, and these are supplied with the corresponding color correction data (8 bits) and the weighting factors r/lA i to form A1K1
Multiplication processing is executed, and the multiplication outputs of the upper 8 bits are supplied to subsequent accumulators (ALUs) 37 to 39, where the multiplication outputs are sequentially added.

The accumulators 37 to 39 are operated with an accuracy of 16 pits,
The upper 8 bits can be used as the cumulative output (product-sum output). By this, the cumulative output is changed to the weighting coefficient Ai
You will get the same output as dividing by . In other words, by doing this, the divider can be omitted.

The accumulated output of the upper 8 bits is latched by latch circuits 45 to 47, respectively. Latch pulse is controller 50
is generated.

The configuration of each part will be explained in detail.

The color correction data storage means 20 stores each color C,
L that stores accurate color correction data corresponding to M and Y
U T 21-23 are used.

ROM with pit capacity in 256 as LUT21 to 23
When using , only 32 points are extracted from the minimum level to the maximum level of the input image data. This gives 32 points per color (so for 3 colors, 323=
32,768 points) of color correction data can be stored.

Therefore, when the input level is 256 gradations, 32
For example, the distribution of points is "8" starting from O, as shown below.
Separate by 0, 8. 16.・ ・ Lu war
240. 248 points are distributed equally so that the total number is 32 points, and the 33rd point, which is 249 points or more and 255 points, is not used. Alternatively, points 249 to 255 are treated as 248.

The color correction data at each distribution point is accurately calculated, and the calculated color correction data is applied to each LUT.
21 to 23.

Note that setting the distribution points to 32 in this manner has the advantage that the storage means 20 can be constructed at low cost since a general-purpose ROM with an 8-bit output can be used.

The weighting coefficient Ai at each distribution point is stored in the LUT 24 for weighting coefficient storage means. Now, when allocating 8 bits at a time as described above, 8 weighting coefficients Ai
The total is 8X8X8=512, but as mentioned above, a commercially available general purpose
If you try to use C, the weighting coefficient (
512) increases the number of elements, so in this example, an approximate value compressed to approximately 1/2 of the theoretical value can be used as the actual value of the weighting coefficient.

In the example shown below, the sum of the eight weighting coefficients is always set to 256, and the maximum weighting coefficient is
255.

In such a case, for example in FIG. 17, if S is at the same position as Pl, each weighting coefficient of P1 to P8 is ()
PI, P2. P3.
P4. P5. P6. P7. P8255,
O,0,0,0,O,0,1(512,O,0,0,0
, O, O, O), and the total sum of the weighting coefficients is 256.

Also, when S is between 21 and 23 and is 3 away from Pl (and therefore 5 from P3), P
Each weighting coefficient of 1 to P8 is as follows.

Pl, P2. P3. P4. P5. P.G., P.G.
7. P81(50,0,96,0,0,O,0,1(
320, 0, 192, 0, 0, O, O, O), and each weighting coefficient is appropriately selected so that the total sum of the weighting coefficients in this case is also 256.

In the same way, S is separated by 3 from the plane of P1 to P4, and PI
, P3. P5. 1 away from the plane of P7, and PL,
P2. P5. If it is 5 away from the plane of P6,
The weighting coefficients P1 to P8 are as follows.

PI, P2. P3. P4. P5. P6. P
7. P2S5, 7. 88. 12. 32. 4
．． 53. 7 (105, 15, 175, 25, 63,
9, 105, 15), and each weighting coefficient is appropriately selected so that the sum of the weighting coefficients in this case also becomes 256.

The above-mentioned t:1 bit distribution signal is a control signal for specifying the color correction data before and after the point S.

That is, for convenience of explanation, the relationship between the 32 allocation points (lattice points) and the corresponding address signals is set as shown in 19th [d].

Now, when the level of the input image data is 100, an address signal (12° 13) is generated so that the color correction data (96 and 104) before and after including this input level can be output from the color correction data storage means 20. There is a need to.

Therefore, when the signal is O, the address signal (12) is such that the smaller color correction data (96) can be referenced.
is output, and the allocation can be controlled so that when the signal is 1, an address signal (13) is output so that the larger color correction data (104) is referred to.

However, when the maximum value to be used (248 in this case) is used, and the distribution signal is 0, the color correction data of its own value is selected, and when the distribution signal is 1, the smaller one is selected. color correction data (240 in this case).

The distribution signal is also supplied to the weighting coefficient storage means 24.

By the way, when using a recording medium such as photographic paper,
Since there are differences in sensitivity depending on each lot, if such sensitivity differences are taken into account, it is necessary to provide color correction data that can correct a plurality of sensitivity differences according to each lot. However, it is practically impossible and impractical to prepare color correction data storage means 20 corresponding to sensitivity differences in this way.

If the configuration uses the color correction data storage means 20 in common, it can be realized without much difficulty.

FIG. 20 shows an example of a color masking device 10 suitable for use in such a configuration, in which input image data B, G, and R are once sent to the color masking device via LUTs 55 to 57 for input value correction. 10. The color correction data storage means 20 stores color correction data corresponding to one type of sensitivity.

Corrected image data is calculated from the color correction data from the color correction data storage means 20 and the weighting coefficient at that time. The corrected image data is sent to LUT61 for sensitivity correction.
-63, and corrections are made in accordance with the sensitivity of the photographic paper used.

Here, the LUTs 61 to 63 for sensitivity correction are fully stored with a plurality of types of sensitivity correction values corresponding to differences in sensitivity, and the correction value is selected according to the sensitivity of the photographic paper used.

Furthermore, the input/output characteristics of this LUT for sensitivity correction take human visual characteristics into consideration. If a sensitivity correction curve of input/output characteristics as shown in FIG. 21 is used, the occurrence of false contours due to quantization errors can be minimized.

By the way, although the above example does not have a configuration that makes full use of 256 gradations, for example, if the following idea is followed, it is possible to realize a color masking device that makes full use of 256 gradations. (See Figure 24).

To do this, first, grid points are distributed in a mixed form of 8-bit spacing and 9-bit spacing. By using a mixed type, identification signals with an 8-bit interval and a 9-bit interval are prepared. Therefore, the relationship between the output of the address number 8 forming means 40, the lattice points, and the identification signal is set as shown in FIG. 22.

As a result, for example, when the input is 216, the relationship between the output from the address signal forming means 40 and the output from the controller 50 is controlled as follows.

Distribution No. 48 01 Address signal to 24 63 Address signal to 20 2627 Identification signal 11 Here, the value of the address signal to the weighting coefficient storage means 24 is the minimum value closest to the input 216 when the signal is O. When the signal is 1, the difference (=6) between input 21'6 and the next grid point 219 is selected (=6).

Identification number 48 1 represents a 9-bit interval grid point, 0 represents 8
It represents grid points at bit intervals, and an identification signal is required for the following reasons.

In other words, if the spacing of the grid points is different, the spatial area created by the grid points of the three colors will not be a cube but a rectangular parallelepiped, and its volumes will be 512 (=8X8X8), 576 (=8X8X
9) 648 (=8x9x9), 729 (=9X
9x9) can be done in 4 ways. Therefore, an identification signal is required to determine whether one side is 8 bits or 9 bits.

Further, in the weighting coefficient storage means 24, the respective weighting coefficients are set in accordance with this identification signal so that the total sum thereof becomes 256.

For example, the image data value of each color is (64,143,216) If so, the result will be as shown in FIG.

Therefore, from the weighting coefficients and color correction data as shown,
Final color correction data is obtained according to the above-mentioned calculation formula.

If the bit interval of the lattice points is selected appropriately in this way, 25
Six gradations can be fully used. However, in this case, it goes without saying that the controller 5o can be configured to generate the identification signal as described above.

FIG. 24 shows a color masking device 1 configured in a sequential manner.
This is a case in which the present invention, particularly a configuration that fully uses 256 gradations, is applied to FIG. 0, and parts corresponding to those in FIG.

In this example, the maximum distance between grid points is 9 pits, so
As an address signal for referring to the weighting coefficient corresponding to this distance, 4-bit data is sent to the address signal forming means (BRI).
T) 40 can be supplied to the weighting coefficient storage means 24 side. The address signal forming means 40 outputs signals at roughly 8-bit intervals and 9 bits.
A bit interval identification signal (one pit configuration) is output and supplied to the weighting coefficient storage means 24.

LUT21-23 for color correction data contains the 11J
al i A control signal σ for sequentially selecting chips in the children σπ, which is supplied by r and Y, and is applied to LUTs 21 to 2, for example.
After the color correction data has been read out from each color correction data in the order of 3, it is completely supplied to the multiplication and accumulation means 30.

Also in the multiplication/accumulation means 30, correction value calculation for each color is sequentially processed.

As shown in the figure, the multiplication/accumulation means 30 uses a multiplication accumulator constructed of a single chip, and the data of the upper 8 bits of the product sum output (accumulation output) are sequentially output for each color. Ru.

The controller 50 is composed of a 9-ary counter 51 and a latch circuit 52 for adjusting output timing. A reference clock to the counter 51 is commonly supplied to clock input terminals Xck and Yck of the multiplication accumulator 30,
At this clock timing, each data of the color correction data Ki and the weighting coefficient Ai input to the X and Y terminals can be processed. Then, a clock that has counted down the reference clock to 1/9 is supplied to the Zck terminal so that the final color correction data can be output from the output terminal Z OUT at the next timing after the product-sum output for eight times is obtained. .

Note that when the level of the arithmetic processing control pulse supplied to the accumulate terminal ACC is 1, the product-sum processing of X-Y+Q (Q is the previous product-sum output) is executed. The O-level control pulse is generated every time the ninth reference clock is obtained, thereby resetting the product-sum output and preparing for the next color correction calculation process.

Therefore, during this reset, all O
1 of this storage means 24 so that the weighting coefficient of
A reset signal is supplied to the 17 terminal.

As a result, the data of Yin becomes O due to the pull-down resistor Rp, and a reset process of X-Y (=0) is executed.

The embodiment described above can also be modified as follows.

First, although the final color correction data is calculated from the color correction data of eight grid points in the above description, it may be interpolated from the color correction data of two diagonal vertices. Such an interpolation method is particularly suitable when using correction data for a larger number of points than those described above as color correction data.

Second, although the color correction data is stored in the LUT in the ROM configuration in the above, RAM is used as a storage means for this color correction data, and another memory (ROM, disk memory, etc.) is prepared for storing the color correction data. Then, when necessary, the color correction data is read from this separate memory and transferred to RAM.
It can also be written and used.

According to this configuration, since the 5-RAM can be used as the RAM, it is possible to speed up the calculation processing time.

In this configuration, which uses a separate memory and downloads it when necessary, this separate memory stores data such as color inversion data, data that selects a certain output color, data that changes the color tone depending on the type of illumination light, and color data. Data for special effects such as data for emphasis can be prepared. You can create special effects relatively easily by downloading and using these as many times as you need.

Thirdly, when the color masking device is applied to printing, it is only necessary to separately prepare an LUT storing black (stain) data in the color correction data storage means 20. In this case, it is better to configure it as a sequential color masking device because the configuration can be simplified.

Fourth, the weighting coefficient may be calculated by using the reciprocal of the distance from the point Pi (or its nth power) instead of using the volume of the rectangular parallelepiped as the weighting coefficient.

Fifth, color correction data storage means 20. Multiplication accumulation means 30
By connecting a latch circuit between each stage, processing between each stage can be separated from each other, thereby enabling high-speed arithmetic processing.

Sixth, the transformation of color space coordinates is (B, G, R), (L
It is easy to understand that it can also be applied to "+a", b"), (X, Y, Z), etc.

[Effects of the Invention] As explained above, according to the present invention, a color image including all combinations of maximum and minimum values of each color separation image signal is formed as a color patch image on a recording medium. This is what I did. Color conversion data for the color system is created by actually measuring colors for the number of color patches.

By doing so, the number of colors to be measured is specified, making color measurement easier.

In addition, if the color patches that can be used during actual measurements are formed taking into account the human eye's discrimination ability, even if the number of color patches is reduced, color patches created without considering the human eye's discrimination ability can still be used. It is possible to obtain color conversion data equivalent to that obtained when

As a result, there is the practical benefit of being able to significantly shorten the color measurement time for color patches without reducing color measurement accuracy.

Therefore, the present invention provides the following advantages when reproducing an intermediate color of a certain color system by mixing a plurality of basic colors constituting a color separation image.
Convergence calculations are performed sequentially while associating the values of the color system close to the target intermediate color set in the color system with the values of the coordinate system made up of basic colors, and the value of the color system closest to the target intermediate color is calculated. The present invention is extremely suitable for application to a method for creating a color patch used in a color separation image correction apparatus in which a target value of a coordinate system corresponding to a value is corrected as a combination of basic colors that reproduces a desired intermediate color.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of Y, M, C coordinate system, Figure 2 is L''
* u ” * v ” An explanatory diagram of the color system, Figure 3 is the same as Figure 1.
An explanatory diagram of the Y, M coordinate system, which is a rough simplification of the coordinate system in the figure,
Fig. 4 is an explanatory diagram of the color system showing the brightness and saturation at that time, Figs. 5 and 6 are explanatory diagrams of interpolation processing, and Figs. 7 and 8 are examples of color patches according to the present invention. Figure 9 is an explanatory diagram of curve approximation, Figure 10 is an explanatory diagram of the sample point expansion obtained at that time, and Figures 11 and 12 are the coordinate system and color system obtained by the sample point expansion. Figure 13 is an explanatory diagram of interpolation processing, Figure 14 is an explanatory diagram when the target value is outside the solid, Figure 15 is a cylindrical coordinate diagram showing the color reproduction range in the color system, and Figure 14 is an explanatory diagram of the interpolation process. Figure 16 is an explanatory diagram of the convergence operation,
Figure 17 is an explanatory diagram of the interpolation process similar to Figure 13;
The figure is a system diagram of the main parts of the color masking device.
Fig. 19 is a diagram showing the distribution relationship of grid points, Fig. 20 is a schematic system diagram showing another example of the present invention, Fig. 21 is a diagram showing the sensitivity correction curve used at that time, Fig. 22 and second
Fig. 3 is a diagram showing the relationship between distribution signals, color correction data, identification signals, etc. Fig. 24 is a system diagram similar to Fig. 18 showing still another example of the present invention, and Fig. 25 is a diagram showing the conventional color scheme. FIG. 26, which is a block diagram of the decomposed image correction device, is a spectral absorption density curve diagram. 10... Color masking device 20... Color correction data storage means 30... Multiplying and accumulating means 40... Address signal forming means 50... Controller Figure 5 Figure 6 Figure 7 M MC=0641
28192255 C=064128192255 Red Figure 8 Watch shelf system G fw'δ';) Figure 13 Figure 15 Figure 16 Figure 17 Figure 20 Figure 21 Quantum A to i-

Claims (5)

[Claims] (1) A color image reproduction device that mixes a plurality of basic colors based on a color separation image signal input as an electrical signal and reproduces the mixture as a color image on a recording medium produces a plurality of colors based on different combinations of the above color separation image signals. A method for creating a color patch, characterized in that a color is reproduced as a color patch image on a recording medium. (2) The color patch according to claim 1, wherein the plurality of colors include at least all the colors that can be reproduced by a combination of the maximum signal value and the minimum signal value of each of the color separation image signals. How to make. (3) The above color separation image signals are yellow Y, magenta M
, cyan C, cyan C, and cyan C. (4) Number of signals PY used for the above combination of Y, M, and C
, PM, and PC are selected so as to satisfy the relationship: PY<PC≦PM. (5) The method for producing a color patch according to any one of claims 1 to 4, wherein the recording medium is a color photographic material.