JPH02136848A - Estimating method for color reproduction characteristic using color patch - Google Patents

Abstract

PURPOSE:To improve color reproduction characteristics by finding combination of Y, M, C and K where K reaches the maximum density value for each specific point of color coordinates given discretely, and estimating the density value of Y, M, C, and K corresponding to the color coordinates except the specific point from the colorimetry of a color patch formed by the discrete combination. CONSTITUTION:When the discrete point number (n) of Y, M, C, and K is selected as five, and the maximum quantizing level as 256, each point interval is 64 steps. By combining basic colors Y, M, C and K of these five points (0, 64, 128, 192, 255), actual recording is performed on a recording medium. For instance, when recording is carried out on a printing sheet with ink, color patches are obtained. The color patches are actually subjected to colorimetry, the colorimetric values are converted into the value of a colored system L*u*v* by using a conversion formula regarding another colored system; moreover, they are plotted at every color patch. Then, a colorimetric value of each color patch corresponds to each lattice point. Therefore, the color reproduction characteristic can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] This invention is applicable to color coordinates given, (are), - when V) 1, -
Accurately input the input color separation surface signal corresponding to the color JE
Regarding the method of estimating color reproducibility characteristics using a color patch suitable for application in a given case, L2 has been aimed at improving the color reproducibility characteristics, particularly by shortening the processing time for estimating color reproducibility characteristics.

[Background of the Invention] When full-color printing is performed by printing, thermal transfer, inkjet, electrophotography, etc., the output colors of a color printer are generally Y and M.

Four colors, C and K, are often used.

However, in order to express the four colors, this Y, M.

There are various methods for determining the combination of C and K. This method is generally u (: R(Un
It is called der Co for Removal), or 100% UCR is a specific method.

In the 100% tJcR method, as shown in Figure 24, the original Y,
This is a method of replacing the minimum density of M and C (Yo, Mo, Co) with a dark blue density, and as shown in A of the same figure, Yo
When is the minimum concentration, replacing with 100% UCR results in the result shown in Figure B. The concentrations after substitution are Yn,
Between n * Cn + K n (However, Yn=O)
becomes.

It is known that such a 100% UCR method has the following characteristics.

- Increased reliability of work.

- Stable gray balance.

・You can save on ink.

・Can cover some ink instability.

- Saves energy in ink drying and reduces drying problems. This is K for the sum of Y, M, and C ink amounts.
This is because the amount of ink can be reduced to approximately 1/3.

On the other hand, when determining the color reproduction characteristics of Y, M, C, and K,
Create a small number of color patches with discrete combinations of M, C, and K, actually embellish these color patches, and interpolate and calculate the colorimetric values to create -Y', M, and other combinations other than the above.
It has been considered to estimate the color reproduction characteristics of C and K, that is, the colorimetric values for a certain combination of Y, M, C, and K.

Conversely, when a specific color coordinate is specified, the combination of Y, M, C, and K that is emitted by that color coordinate is also estimated by interpolating and calculating the values actually measured from the color patch. can do.

In this way, all combinations of Y, M, C, K, Y, M,
If estimated using a color patch created based on an ih combination of C and K, Y, M, and C can be estimated from the actual colorimetric values.
, K, the estimation accuracy is improved and the color reproduction characteristics are further improved.

Note that FIG. 25 shows an example of a color patch created by a discrete combination of Y, M, C, and K. The figure shows Y,
This is a color patch when the maximum values of M, C, and K are each set to the 8th power of 2, and the color density is extracted in 5 stages with 64 steps.

Also, when a certain color coordinate is given in this way, or an electric signal corresponding to that color coordinate (for example, R, G, B
48) is given, in any case, Y, M, and C are obtained from these.

A color output modification means is required to obtain the K combination.

FIG. 26 shows an example of this, in which a color masking device 1, which is one of the color separation image correction devices, is installed upstream of the printer 12.
0 is provided, and the color separation image signals of R, G, and B corresponding to the color coordinates are converted into color No. 43 of Y, M, and CK, and then supplied to the printer 1; M,C
, K on the recording medium 13.

[Problems to be Solved by the Invention] By the way, although the above-mentioned 100% UCR method has the above-mentioned advantages, - the saturation generally decreases.

・When the proportion of the black plate increases and 7<, the density decreases.

These disadvantages include deterioration of color reproduction characteristics.

Therefore, in this invention, in addition to improving the color reproduction characteristics which is the f-ma point of the 100% UCR method, it is possible to estimate the color reproduction characteristics using fewer color patches when applying the method of estimating the color reproduction characteristics using Color Gutsuchi. This is how it was done.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in this invention, when color coordinates are specified, yellow Y1 indicating the color coordinates is
In a color reproduction characteristic estimation method for estimating the combination of magenta, M, cyan, C, and smudge, among the combinations of Y, M, C, and K indicating the given color coordinates, the value of K is the maximum density value. M.C.

The combination of K is determined for each specific point of the discretely given color coordinates, and color patches of Y, M, C, and K are created by these discrete combinations, and the created color patch paste is made of 11 colors. The present invention is characterized in that Y, M, C, and K density values corresponding to color coordinates other than the specific point are estimated from the values.

[Action] When the color coordinates of Nintei: are given, the color is represented by tY,
In general, there are an infinite number of combinations of M, C, and K.
In order to make this countless number of combinations unique, a condition is introduced that the value of t3,K of the combinations indicating the given f-color coordinates has the maximum density value.

This condition is that any one of Y, M, and C has the minimum density, or that K has the maximum density (this is nothing but solid in printing). In addition, we added the following condition (improved condition): ``The value of K takes the maximum density value within the range that can represent a certain color'' (t: 100%t), and converted the JCR method to an improved version for convenience. This is called the 100%tJ CR method. By using the improved 100% OCR method, the color reproduction characteristics are improved,
It will be done.

The required color patches are also determined based on this improved condition (FIGS. 1, 3, and 5), and the number of color patches can be reduced.

[Embodiment 1 Continued-C1 A method for estimating color reproduction characteristics using color patches according to the present invention will be explained in detail with reference to FIG. 1 and subsequent figures.

When given any color coordinates, it does not represent that color, Y, M
, C, K combinations - in general, there are an infinite number of them? r exists.

In order to make the countless combinations of 2 quasi-, a condition is introduced that K takes the maximum density value among the combinations showing the given color coordinates.

That is, even within the range of color coordinates, K takes on various L values;
Since q, the maximum value of K that can be taken is 11' of K.
If it is decided as l, then other Y will be determined by this.

This is because determining the combination of M and C results in X.

This condition is based on Y, M, and C. One must be the minimum concentration, or K must be the maximum concentration, and when converted into a bay, ・When Y is O, 9M is O. When ・When C is O ・When K is maximum (255) ・ ・ ・ (1) This is nothing but the condition. Then, the color solid that cannot be determined is the color reproduction range.

In the 1.00% OCR method, K is replaced by Y.

If any one of M and C is replaced, the replaced minimum density color will be O, or under the above conditions (if K is the maximum density "L'", one of Y, M, and C will be O). This is because it is not necessarily the case (improving the kneading for convenience 100% U C
(referred to as R method).

A color patch is created using this improved 100% UCR method, as shown in Figure 1.

The figure shows the discrete bound numbers 1'l of Y, M, C, and K.
5 and the maximum quantization level is set to 256 steps, L: In this case, each pollind interval becomes 64 steps. These five points
(0,64,128,192,255) is also ζ light blue Y,
By combining M, C, and K, you can actually create a recording medium, such as printing paper.
When ink is recorded on L, the color patch shown in FIG. 1 is printed.

The first step is to actually embellish the color patch in the figure and use its colorimetric values (given color coordinates) and other color systems (for example, l-
Using the conversion formula for "; The 11 color values of each color patch correspond to the respective grids.However, for convenience of explanation, this second figure is expressed on two axes of saturation and lightness, so it is It is drawn with the value of C omitted.The same applies to the j color system shown below.

The color patches satisfying the above-mentioned formula (1) can also be made as shown in FIG. 23. According to this FIG. 3, the number of color patches is roughly reduced from that in FIG. 1.

Actual color patch in Figure 3 LJ: a'1 color l
-6u ” 1./' 1q image ゛4 in the color system, 4th
Figure 1: It becomes sea urchin.

This is the value obtained by actually embellishing the black circle.

In the color system shown in Figure 4, as the value of K increases, the lattice spacing is reduced approximately 1g7 linearly, so when K is thick, the white circle lattice point is the one on the previous lattice. Even if it is determined by i-line interpolation (for example, internal interpolation) based on point data, the error will be small.

If all the white circle grid points are interpolated, the color system will be the same as the color system shown in FIG. This is the same as using the color patch shown in FIG. 1 as the color patch.

In other words, not only does it simply match Equation (1), but even if the number of color patches is reduced as the K value increases using the properties of colorimetric values, if interpolation and arithmetic processing are performed, the result will be the same as in Figure 1. ,
The number of color patches can be reduced.

The color patch may have a configuration as shown in FIG.

By electrical processing, the lattice spacing can be roughly 1/1/2 compared to the above.
To make the value 2, interpolation and calculation may be performed based on the mapped value. The interpolation process in this case is nonlinear interpolation process. An example of interpolation processing is shown in FIG.

As shown in Fig. 6, if the black circle is a grid point (sample point) and the Δ mark and the Different interpolation formulas are used when there are one point and three points before and after the X mark, respectively.

The color system of the point to be interpolated is L*'+ um * V-, and the color system of each sample point is Li'ui'' v
i'' (i=1 to 4), the former case can be interpolated using the following interpolation formula.

L, n”= −(1/16) Ll+(9/16)
L2”+ (9/16) L 3°-(1/16) L
4"u-=-(1/16)ul"+(9/16)u2
"+ (9/16) u 3" - (1/16) u
4”v-=-(1/1B) vl”10 (9/16)
v2"+ (9/16) v 3m - (1/16) v
4° In the latter case, the following interpolation formula is used:

L♂= (5/16) L 1” + (15/16)
L 2”-(5/16) L 3”-(1/1(5
) L 4t′u,” = (5/16) u 1
" + (15/16) u 2" - (5/16) u
3"-(1/10) u 4"v," = (5
/ 16) v 1” ten (15/16) v2”-(5
/16) v 3° (1/16) v 4c' An example of the order of interpolation processing is shown in FIG. Number I.

Interpolation is performed in the order of II and Ill.

Through such interpolation processing, it is possible to obtain a similar number of grid points in a color system using a larger number of color patches than the number actually measured.

The interpolation process may be an interpolation process using linear approximation.

If you do the above, you can avoid increasing the number of color patches.
The only thing to do is to obtain the color coordinate values corresponding to the colorimetric values. In this case, the color coordinate values are all grid point data.

The values of color coordinates that exist outside the grid points are calculated by convergent interpolation as described below.

That is, as shown in FIG. 8, the color coordinate point (target value) T1' that is off the grid point corresponds to the target value T1 of the Y, M coordinate system shown in FIG. This corresponds to T2 in the MK coordinate system of B, and point T3- corresponds to T3 in the M, Y coordinate system of C in the figure.

For the sake of simplicity, the relationship with FIG. 9A will be explained.

The target value TI'' shown in FIG. 10 is within the area surrounded by grid points a' to d', and therefore Y in FIG.

In the K coordinate system, it is assumed that the area is within the area surrounded by the square grid points a - d (actually, within the three-dimensional area), so the calculation process to check which area it is in is shown in Figure 10. The area is determined by converging while associating the color system of with the coordinate system of FIG.

FIG. 12 is an enlarged view of FIG. 10, and FIG. 13 is an enlarged view of FIG. This is determined by examining the geometrical positional relationship between the grid points and the target value TF.

In reality, regions are selected by checking the coordinates of vertices in each region using a determination formula described later. If this area is assumed to be So'', it can be estimated that the target value T1 is within the area So corresponding to the area So= in the coordinate system of FIG.

Next, the estimated area So is divided into four equal parts. A total of five lattice points (division points) e=i to be divided into four equal parts are calculated by weighted averaging using the surrounding lattice points a=d which have already been found. 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 of FIG. 12.

Then, the target value T
The region S2- containing t, :+ is obtained by the same method as described above, and the region S2 in FIG. Ru.

By repeating such region division, the grid becomes progressively narrower and eventually converges. This converged area (in Fig. 12, this is designated as 810' for convenience)
By averaging the values of the four vertices that make up the target value T1 surrounded by the corresponding area SIO, the target value T1 is determined as the tth basic color combination (actually, , Y, M, C, K).

On the other hand, if the target value r' of the given color coordinates is outside the color coordinates shown in FIG. 14, a point (actually, a surface) T'' that intersects with the color coordinates is calculated.

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, as shown in Fig. 17, move in the achromatic direction without changing the hue of the color, and change the color at the point where the straight line q in the achromatic direction intersects the boundary of the color reproduction range to the target color. It is sufficient to use the value "T" and "C".

As shown in FIG. 15, determining the intersection point r is nothing but searching for the outer peripheral surfaces a' to r' of the color coordinates, and Y, M, C
In the coordinate system, it is nothing but finding the intersection with each axis a to r in FIG. 16.

In FIG. 14, the plane where the target value T' intersects is any of the 12 planes shown by the following conditions.

1, Y61 and K is 0 2, Between is O and K is 0 3, C is O or K is 0 4, Y is O and M is the maximum value 5, Y is the maximum value and M is 0 6, M is O and Y is the maximum value 7, between is the maximum value and C is 0 8, C is 0 and Y is the maximum value 9, C is the maximum value or Y is 0 10, Y is the maximum value or K is the maximum value 11, M is the maximum value Maximum value and K is maximum value 12, C is maximum value, K is maximum value After the intersection plane is determined, as shown in Fig. 18, from the area surrounded by the grid points (displayed by black circles), calculate the area within the white circle display. The target value T '' h is calculated by converging the area.

Based on the above, there are two cases (Y in J).

Combinations of M, C, and K can be found.

■ If the given color coordinates are included in the color solid, Il, If the given color coordinates are not included in the color solid, this series of color reproduction characteristics estimation algorithms are as shown in Figure 19. becomes.

In the above explanation, each value of Y, M, C, and K is not necessarily the minimum density when it is 0, and the maximum density when it is the maximum LA (255 on the upper side). For example, the settings shown in (Table 1) are not acceptable.

(Table-1) YMCKO value Printing Thermal transfer Electrophotographic method 0
Formula % (8 bits) (M1 percent) (concentration)
(1 If heart) In the explanation of the electrophotographic method, O indicates the state in which no l.ner is placed at all, and 2
56 shows a state in which toner is completely loaded.

By doing as shown in Table 1, you can prevent instability and jumps near highlights and shadows.

Next, an example of a color masking device (color separation image correction device) suitable for applying the method of estimating color reproduction characteristics using color patches according to the present invention will be described.

The target values (Y, M.

A combination of C and K (color correction data) is stored in advance in the main lookup table (M LUT ). If the input system is a color CRT,
The coordinate system for Y, M, and C, which is associated with the basic color coordinate system determined by B, G, and R, becomes the given color coordinate.

This color coordinate is obtained by calculation. R,G.

The relationship between the coordinate system of B, for example, the coordinate system of B, G, and the coordinate system of Y, M, is as shown in Fig. 20, so the input coordinate system,
For example, a process is performed in which a dot is associated with t' and a point S is associated with S'. Therefore, these R, G, B coordinate systems and Y
, M, C, and the coordinate system, a main lookup table (MLUT) is prepared. For example, when a coordinate system representing point t is input, the coordinate system of t' is referred to. .

Color correction data other than grid points is calculated by interpolation.

As mentioned above, in the improved 100% UCR method,
YMCK data is determined in advance under any of the following four conditions depending on the data of the input coordinate system.

(a) Y, M, K (C=O) (b) y, C, K (M=O) (c) M, C, K (Y=O) (d) Y, M, C (K is Maximum density, solid)...
- (2) To simplify the explanation, (a) will be explained.

In this example, as shown in FIG. 21, positive data is created using eight colors 11 including a rectangular parallelepiped-shaped space W (with an interpolation point S at its diagonal apex) determined by three input image data R, G, and B. A rectangular parallelepiped spatial region V is defined by (known calculated color correction data P1 to P8 corresponding to Y, M, C (=O), and K). Both of the spatial regions W and ■ have Pl as a reference point. And for each color, 0.32.64.96, 128°160 + 192, 224. , 255 have color correction values as described above. At this time, if the input image data R, G, and B each have a value of (100, 130, 150), the color of the vertex (1'8 child point) of the spatial area surrounded by the 8 points shown below. Interpolated using corrected data.

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 Ki at that time.
+Ci, Mi+Yi are shown.

Pl: (96,0,128,128)=(KL, CI
, Ml, Yl) P2: (128,0,128,12
8) = (K2. C2, M2. Y2) P3: (96,
0,160,128)=(K3.C3,M3.Y3
) P4: (128, 0, 160, 128) = (K4.
C4, M4. Y4) P5: (9G, 0.128.1
60) = (K5. C51M51 Y5) P6: (12
8,0,128,160)=(K6.C6,M6.
Y6) P7: (96,0,160,160)=(K7.
C7, M? , Y7) P8: (128,0,160,
160) = (K8. C8, M8. Y8) spatial region V
The weighting coefficient for each vertex Pi is calculated as follows.

In this example, the volume of a rectangular parallelepiped spatial region W formed by the vertex opposite to the point of the correction value to be obtained and the interpolation point S is set as the weighting coefficient Wi at the point of the correction value to be obtained.

Therefore, the weighting coefficient of point P8 is calculated using the coordinates of Pl and S: (100, 130, 150) (96, 128, 12
8) = (4, 2, 22), the volume of the rectangular parallelepiped spatial region created by S and Pl 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 (2), and in this example, it is 32768 (assumed to be a).

Therefore, the positive values Ks, Cs, Ms, Y at point S
s is Ks = 1/a (PIK1 + 2 for P2 + 3 for P3 + 4 for P4 + 5 for P5 + 6 for P6 + 7 for P7 + 8 for P8) Cs
-1/a(PIC1+P2C2+P3C3+P4C4+
P5C5+P(5C6+P7C7+P8C8)=0M
s = 1/ a (PIMI + P2M2+ P
3M3+ P4M4+P5M5+P6M6-1-P7M
7+P8M8) Y s = L'a (PIY1+ P2
Y2+ P3Y3+ P4Y4→-1 5Y5+ P6
Y6+ P7Y7+ P8'Y8). That is,
For a certain request t, the correction values of the 8 points surrounding the two points S1 are Kin Ct + Min Yi (this means t in the color system
, p-value 1. ．． ．． s", u s", v S", and t2Y, M, C, are the values of the coordinate system), and the respective weighting coefficients are Ai, then Ks-" (1/nAi)nAiKi I Eagle 1 i=1 Ms= (1/1'1Ai) AkiraAiMi11□I
Ys-=(1/DΔi) 4AiYi1=l
+=1 (5 years old) Can say ``i~go''.

Input (earth drift system) 2. When the data of G and B are different,
The weight and mesh coefficients Ai calculated by 1 are interpolated corresponding to the human data.

Since this manual data already satisfies conditional expression (2) and contains the i value, the interpolation device does not change it according to conditional expression (2).

Note that, 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, each color has 132 bits.
Point color (I correct data (all 3 colors C1323 = 3276
8 points).

FIG. 22 shows an example of the color masking device 10.

The data storage means 20 stores the old colors Y and M for the color f[.

The color correction data for C and K are each M i,...
Stored in UTs 21-24. , 25 are weighting coefficient storage means, which are configured as L, LJT.

Input image data B, G, R1f - Once supplied to address No. 4g forming means 40 S C1 One L corresponding to one human-powered novel
A 5-bit address signal is output and supplied to the A1 stage 20 for color correction data. 3 or I: From this point on, the weighting coefficient designation signal of t2 lower 3 bits is supplied to the weighting coefficient storage means 25.

When the color coordinates determined by the input image data R, G, and B are outside the grid points in Fig. 20, the 4-) grid in the coordinate system surrounding the color target is Y, M, and C. The color correction data storage means 20 may be referenced by a 5-bit address W-J or manual image data R, G, B and outputted, as specified by 4X. 1- Become.

address)] forming means 40 also includes a people LUT (Pl, -U
T ) 4 L -- 13 Te 14 will be completed. ,,T,
(As a JT, a bipolar ROM/B is suitable. For these PLs and UTs 41-...13, roughly, the controller 50 supplies a 1-bit swing of the balance, or details thereof. will be described later.

There are a total of 8 data indicating color correction data and weighting coefficients (hereinafter referred to as weighting coefficients) corresponding to input 1 of the input image data.
The multiplication/accumulation signal is sequentially supplied to the -1 stage 30 over multiple times.

Multiplication g accumulation f stage 30 is jc, 1 uni Δ1Bi (
[31 is a general term for Y, M, C, K] is executed sequentially, and the I-th sum is calculated, and in this example, 1) 1 calculator 31; Calculator: To 5 38
It is composed of

The sub-) C', 3 multipliers 31-2 34 use a 512-bit ROM, and are supplied with the corresponding color correction data (8 bits) and weighting coefficients Δi etc.
The multiplication process of 1B1 is actually 1-f, and the multiplication υ output to the 1st and 3rd place 1 is output to the subsequent accumulator (8L t,,
J ) 35 - = 38 is supplied and sequentially multiplied p output or added ■
It is processed.

The accumulators 35 to 38 are operated using 16-bit multiplication factors, or the cumulative outputs (sum-of-products outputs) are used. It will be done. This: Therefore,
The same output is obtained when the cumulative output is divided by the weighting coefficient Δi.

The cumulative output of the L-order 8 bits is generated by the latch circuit 46--4.
9 is latched. U-nchivals are generated by the needle roller 50.

The configuration of each part will be explained in more detail.

I used as color correction data storage means 20;

UT2] to 24 are the minimum 1.256 bit capacity ROM of human image data. - Extract 32 points from the bell to the maximum level. by this,
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 points are distributed in order from 0 to r8 as shown below.
Divide into 0.8, 16. ...240.248, total 3
Divide it evenly so that there are 2 pieces, and the 33rd point is 249.
Points above 255 points will not be used. Or 249~
The point 255 is treated as 248.

The color correction data at each distribution point is accurately calculated, and the calculated color correction data is applied to each LU.
This is stored in T21 to T24.

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 8-bit output can be used.

The weighting coefficient Ai at each distribution point is stored in the LUT 25 for weighting coefficient storage means. Now, if 8 bits are distributed as described above, the weight factor TAA will be 8 times.
The total number of i is 8X8X8=512, but as mentioned above, a commercially available general-purpose I with an 8-bit output
If you try to use C, the weighting coefficient (
512), the number of elements increases, so in this example, an approximate value compressed to approximately 1/2 of the theoretical value is 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 of each is 256.
5.

In such a case, for example in FIG. 21, the interpolation point S is P
If it is located at the same position as P1 to P8, each weighting coefficient of P1 to P8 is PL, P2.
P3. P4. P5. P6. P7. P8255
, O, O, O, O, O, 0, 1 (512, O, O,
O, 0, 0+ Ol O), and the sum of the weighting coefficients is 256.

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

PL, P2. P3. P4. P5. P6. P
7. P8160, 0. 96. O, O, 0, 0
, 0 (320, 0, 192, O, O, O, O, O), and the sum of the weighting coefficients in this case is also 256.
Each weighting coefficient is selected as appropriate.

Similarly, S is 3 away from the plane of P]~P4, and Pl
,,P3. P5. 1 away from the plane of P7, and PI
, P2. P5. If the distance is 5 from the plane of P6, the following weighting coefficients P1 to P8 will be obtained.

PL, P2. P3. P4. P5. PI3.
P7. P2S5, 7. 88. 12. 32.
4. 53. 7 (105, 15, 175, 25, 63
,9,io5. 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 1-bit allocation 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 32 allocation points (lattice points) and the corresponding address signals is set as shown in FIG. 23.

Now, when the level of the input image data is 100, the address signal (12, 13) is outputted from the color correction data storage means 20 to output the color correction data (96 and 104) before and after this input level. need to be formed.

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

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

The distribution signal is also supplied to the weighting coefficient storage means 25.

In this invention, the given color coordinates depend on the input device r. -LAs mentioned above, if the input device is a digital display, the color coordinates can be calculated from the R, G, and B values, and if the input device is a printing system, there are four colors for Y, M, and C. It can be calculated from .

Furthermore, if the input device is Sugyana, the color coordinates can be obtained from the values of RK] and B.1. [Effects of the Invention] As explained above, according to the present invention, the color coordinates can be calculated from the values of RK] and B. In the method for estimating color reproduction characteristics, the combination of yellow a - Y1 indicating the color coordinates, magenta M, cyan C and black is determined by Jffl4. , K combinations, the value of K or the maximum density value is Y, M, C.

The combination of l( is found separately for each specific point of the Buddha seat (tsu) given separately, and color patches of J, Ru, Y, M, C, and K are created for these i-numerical combinations (7 , the density values of Y, M, C, and K corresponding to color coordinates other than a specific point are estimated from the colorimetric values of the created color patch.

According to this method, deterioration of color reproduction characteristics, which is a drawback of the 100% UCR method, can be prevented, and in addition, the following effects are also achieved.

- Saves money on ink and toner.

・Achromatic colors (gray balance) can be stabilized.

- Maximize the color reproduction range. .

・Since the amount of ink is reduced, the life of the ink spatula, thermal head, laser, photoreceptor drum, etc. is extended.

- In particular, when recording character areas, false colors on character edges caused by digital 'are reduced, and misregistration of color overlapping plates becomes less noticeable.

Then, use color patches to create Y, M, and C.

When calculating the combination of K, a! Since the number of IJ color patches is reduced, it is possible to shorten the time required for actually performing tricolor Qjj1 color processing.

For this reason, the present invention is extremely suitable for application to cases where color image information is recorded in four colors of YMCK, such as printing, inkjet printing, thermal transfer, etc.

/11 Figure 0liji Funeral explanation Figure 1 is here σ) Provided for explanation of the invention l OO% U C
To the R method, ↓, and the batch diagram to the N color, Figure 2 is the color patch ij! Set the t1 color value to 1. , Figures 3 and 5 are diagrams of color patches mapped to the ゝUゝv'' color system, Figures 3 and 5 are diagrams of color patches according to the improved 100% tJ CR method according to the present invention, and Figure 4 is the diagram. Color patch secondary color value L + t
Fig. 6 is an explanatory diagram of curve approximation, Fig. 7 is an explanatory diagram of target value expansion obtained at that time, Fig. 8 is a diagram of the ``u'v'' color system when mapped to the utt■7 color system. Diagram showing the system, Part 3
The figure shows the coordinate system in Y, M, and the same relationship as in Figures 10 and 11, Figures 8 and 9. Figure 12 and Figure 13 are illustrations of convergence calculations. , Fig. 14 to Fig. 18 are explanatory diagrams when the color coordinates are outside the color reproduction range, and Fig. 19
The figure shows the color coordinates, Y, M,
Flow f-1・-1・, which shows the algorithm for finding the combination of C, K, and FIG.
Figure 211 is an explanatory diagram of interpolation processing, Figure 22 is a system diagram of a color masking device to which this invention is not applied, and Figure 23 is a diagram showing the relationship with the coordinate system.・A diagram showing the relationship between responses and color correction data, Figure 24 is an explanatory diagram of the 00% UCR method, and Figure 25 is Y, M, C, K
FIG. 26 is an explanatory diagram of a color patch according to No. 26-1, which is a system 4 of a color image forming apparatus used for explaining the present invention.

10... Color masking device 12...Color printer 13...Recording medium

Claims (1)

[Claims] (1) When a color coordinate is specified, in a color reproduction characteristic estimation method that estimates a combination of yellow Y, magenta M, cyan C, and black K indicating the color coordinate, Y, M indicating the given color coordinate. , C, and K, the combination of Y, M, C, and K for which the value of K is the maximum density value is determined for each specific point of the discretely given color coordinates, and the combination of these discrete Create color patches of Y, M, C, and K based on the combination, and estimate the density values of Y, M, C, and K corresponding to color coordinates other than the above specific points from the colorimetric values of the created color patches. A method for estimating color reproduction characteristics using color patches, characterized in that: