JPS59163973A - Color recording system - Google Patents

Abstract

PURPOSE:To simplify the color correction and to quicken the processing speed by deciding a recording area rate of black and selected ink based on each reflection factor of the ink in a system reproducing color with plural colors (including black color) of inks. CONSTITUTION:Color separation output signals R, G, B from a television camera 601 are inputted to a processing section 603, area rates (y), (m), (c), (k) of each print ink to the combination of each color are calculated based on the reflection factor of each color stored in a memory 608 and the area rate in matching with the conditions is outputted. The area rates (y), (m), (c), (k) thus selected are inputted to a print section 607 through a nonlinear converting circuit 605 and printed. Then, the combination of the ink color to be printed directly is selected from the color input signals R, G, B and also the area rates of the selected color and black inks to be printed are decided at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a color recording system that reproduces colors using inks of a plurality of colors including spot colors. .

BACKGROUND OF THE INVENTION Conventionally, in the fields of color printing and photography, color correction methods using (1) the Manosking equation and (2) the Z-Geba equation have been used as techniques for more faithfully reproducing colors. On the other hand, color recording devices are changing over time from halftone expression using the conventional analog recording method to halftone expression using the digital recording method.

Color photography is a typical example of the analogue medium-style expression method.
There are color electrophotography methods, etc. These colors are reproduced using the subtractive color method on the recording material P as shown in Figure 1.
Each of the 1 cyan C inks forms a complete layer structure.

On the other hand, representative examples of digital halftone expression methods include a multicolor overlay printing method, an inkjet recording method, and a binary recording method using electrophotography. These color reproductions are shown in Figure 2 (A)
Inks of multiple colors do not form a complete layer structure.

Incidentally, the above-mentioned masking equation is defined as an equation established based on the density of printed matter based on additive cutting. Therefore, this equation can be applied to a color overlay system with a primary layer structure as shown in Figure 1, but additive cutting cannot be applied to a color overlay system with a partial layer structure as shown in Figure 2. First, it is difficult to perform complete color correction using masking equations. The Noigba equation is an equation formed on the assumption that the overlapping areas of printing inks are random and the area ratio of the overlapping parts is proportional to the size of each ink area. Therefore, it is fully applicable when the overlapping of printing inks is random due to screen corner processing, etc., as seen in the overlapping of colors in printing, but in cases such as the one shown in Figure 2, it is not possible to completely solve the problem using the Noigpa equation. Color correction is difficult.

As is clear from the above explanation, the color correction equation based on digital recording has the drawback that it cannot be processed by conventional masking equations or Neugeber equations.

In addition, for the purpose of achieving good intermediate A4 expression,
As shown in FIG. 2(B), black, which is reproduced by overlapping all of Y, M, and C, may be reproduced separately using black ink, a so-called public insertion process. For this processing, minimum value detection for focus data detection,
Processing such as so-called undercolor removal, which removes the black component from other color data, is required, and this requires memory for data storage and complex arithmetic circuits, and this also increases processing speed. There are problems such as a decrease in

Purpose The present invention was made in view of the above points, and its purpose is to provide a recording method suitable for digital color recording.
Specifically, the purpose of the present invention is to provide a method for determining a printing ink area ratio suitable for digital color recording. Another object of the present invention is to provide a method for determining the printing area ratio of a plurality of color printing inks including black suitable for Hayashi digital color recording in order to improve β tone reproduction.

Example The present invention will be further explained below with reference to the drawings.

In order to explain the present invention, (A) Theoretical background.

(B) The practical implementation method will be explained in two steps.

(A) Theoretical Background Let us consider a case where a large number of colors are digitally expressed using two colors and a black recording area as shown in FIG. 2 (B).

When printing on recording paper P, prepare printing inks of three primary colors using the subtractive color method and four colors of black, namely yellow (Y), magenta (M), cyan (C), and black (K). In principle, any color can be reproduced by selecting and printing a maximum of two colors from black and six other colors. There are six combinations in which two colors are selected from the three colors mentioned above.

This is shown in FIG.

The area ratio of each ink for Y, M, O, is expressed as y per unit area,
Assuming m, C, and k, the areas for each composite color in cases (a) to (f) of FIG. 6 are as shown in FIG. 4. However, the unit area was set to 1.

Next, the light energy of each color reflected from each ink combination is calculated.

The case of FIG. 4(a) will be specifically explained by taking as an example.

The respective reflectances when printed with each single color ink on recording paper P are red light reflectance Rs, green light reflectance 0 days, and blue light reflectance BS.
shall be. Here, it is expressed as Sba7+mrC+k, where y is yellow, m is magenta, C is cyan, and k is a nafix that distinguishes between the cases where black ink is used. Similarly, the respective reflectances when two different color inks are overlapped are designated as red light reflectance Rd, green light reflectance Gd, and blue light reflectance B(i).

Here, d is a combination of two of the three colors y, m, and c. Therefore, Rym indicates the red light reflectance when yellow ink and magenta ink are overlapped.

Generally, even if two inks of the same color are stacked, the reflectance will differ depending on the order in which they are stacked. Accordingly, suppose that the Nafix is determined to indicate the order of the recording ink layers on the recording paper P, and the Rym
This is the red light reflectance when there is first yellow on the td recording paper P, and then there is magenta on the yellow. That is, Rym
% Rmy.

Further, the suffix W is added to the reflectance from the white background portion.

FIG. 5 shows the state of red light reflection for the four colors of white, black, yellow, and green when ink is recorded as shown in FIG. 5(a).

From the area ratio of each color shown in Figure 4 (a), the total red light reflected energy RT of 55 wards is RT = (1-(k+y))Rw+kRk+mRy
m+ (y-m)Ry, transform this to RT-4w=(Rk-Rw)k+(Ry-Rvr)y+
(Rym-Ry)m.

Ru. The conditional expression is the combination of Figure 3 (a)) 1≧y≧m≧
It becomes 0. Also, black ink K is 1≧≧o Thy:,. On the other hand, since the sum of the area ratios of Bear and Yellow Y C7) is less than 1, 1≧ and +y≧0.

Here, among the respective reflectances, those whose reflectances are very close to 1 as determined by actual measurements are marked as 1, and those whose reflectances are very close to 0 are marked as ○. That is, Rm=Ry=Gy=R
ym Gw == B W-= 1Re = Gm =
If By=Rk==Gk=Bk=0, each equation in Table 1 is simplified and becomes as shown in Table 2. Also, the reflectance of the area where two colors of ink overlap is
$ of reflectance for each color.

For example, it can be considered as Emy=Rm-Ry.

Compared to using conventional color correction equations, the advantages of using color correction equations based on Table 1 or Table 2 are as follows: (1) Three color signal components from the input device Let R, G, and B be R: RT in the formula in Table 1 or Table 2.

G: GT, J3=B7, and at the same time the area ratios y, m, c, k of the ink to be directly printed are determined, two colors to be selected from the three colors of printing ink excluding black are automatically determined.

(2) Complementary color conversion is not required compared to the case based on conventional color correction equations, and undercolor removal is automatically performed, so there is no need to newly remove the black ink component.

(6) In the case of conventional masking equations, there was a problem that the additive side did not hold due to color superposition, but with this method, it is possible to perform color superposition, measure the reflectance of the fc result, and substitute it into the color correction equation. Therefore, the problem of the proportionality law not being satisfied on the additive side disappears.

(4) The area ratio of black ink to be printed is automatically determined by the input signal KGB at the same time as that of other colors.

(B) Practical implementation method A concrete implementation method for achieving color correction according to Tables 1 and 2 is shown in Figures 6 and 7. ◇ 601 in Figure 6 is an input device, such as a three-tube TV. It's a camera. 602 is a color separation signal from the television camera 601, which is separated into R (red), G (green), and B (blue) components, and enters the processing unit 603. R
The GB signal is an incident light energy proportional signal with white as 1 and black as 0. Reference numeral 608 denotes a memory for storing the reflectance of each color component, and is used to store each reflectance inputted externally by an operator using a keyboard, for example, to be entered into the formula in Table 1. Namely, this memo!
If the above-mentioned approximate data is stored in J60B, correction using the simplified correction formula shown in Table 2 will be carried out. 605 is based on the color reflectance stored in the memory 608, and based on Table 1 or Table 2, each printing ink area of six color combinations of R, G, B human power from in to (to) for strawberry. rate y.

m, c, and k are determined and output as 604. In Table 1 or Table 2, RT r "T p Assign the R, G, and B signals from the television camera 602 as they are to BT. Therefore, ("p71+m1) (k2J2tC2) (k
x, +”5rys) (k4.m4.C4) (k5
+%A) (k6.C6, y6) six calculation results are calculated. Of the six calculation results, there is always at least one that satisfies the conditional expression, so by checking it, you can check the result. One is selected.

FIG. 7 is a flowchart showing the processing procedure in the processing unit 603. In step 701, six color signals B, G, and R are inputted from the input ad601. Step 702 is the processing section 6
Six ink area ratios (ki,
71. mi, ci) are calculated according to Table 1 or Table 2 and stored. In step 706, in order to output Ck, +719m+at) of the six area ratios stored,
Set 1 to 11. In step 704, according to the value of 1, all the calculation results of the six letters stored in step 702 are:
E4th reading, in the next steps 707 to 710 (a) ~
Determine whether conditional expression (e) is satisfied.

For example, the calculation result (k4.y,, m, ) is the conditional expression (a)
If it is determined in step 705 that the following is satisfied, the process moves to step 711, where black is set to 1, yellow is set to yl, and magenta is set to km.

Cyan C is not printed.

If conditional expression (a) is not satisfied in step 705, the process proceeds to step 706, and it is determined whether conditional expression (b) is satisfied. In this manner, the selection of the color to be printed and the area ratio of the ink to be printed are determined, and in step 717, the results are output to an external printing device or the like.

607 is a printing unit that records an image according to input data, such as an inkjet printer. Printing department 607
In this case, the reflectance of the print result relative to the human data is not necessarily linear.

This is because, although the human data versus the number of printed dots is linear, the human data versus the printed dot area is no longer linear due to the overlapping area between dots. In order to supplement this nonlinearity, a correction circuit 605 having a nonlinear correction table is provided.
Ru.

Therefore, the printing area ratio c, m, y to be printed output from Table 1 or Table 2 is non-linearly corrected and output 606
As c', m', y', k' and Nasi printing section 60
7 is input.

As is clear from the above explanation, the combination of ink colors to be printed and the area ratio to be printed with the selected color ink are determined directly from the input TV camera output signal Semi-2B without passing through the complementary color conversion circuit. .

At the same time, the black area ratio for inscription and the related undercolor removal processing are performed without providing a dedicated circuit.

Note that it is necessary to print the black ink so that it does not overlap with other color inks as much as possible. This is an example, and two dither patterns are provided as shown in Figure 8.
This can be achieved by using different dither patterns for digitally expressing gradation according to the area ratio, such as for black ink (play) and for other color inks (A).

This explanation uses an inkjet printer as an example, but
Needless to say, it can be applied to other laser beam printers, thermal printers, etc.

Further, the @R, G, and B data to be recorded may also be data read from an image file, data transmitted via a line, or the like.

Further, the present invention can be applied to a method in which the size of a recording dot corresponding to a pixel itself is changed, and a method in which a pixel is constituted by a plurality of sets of certain unit dots.

Effects As explained above, according to the present invention, color human input signals R,
The combination of ink colors to be printed can be directly selected from G and B, and the area ratio to be printed with the selected color ink and black ink can be determined at the same time.

Further, since the F color corresponding to black ink has already been removed, there is no need to newly remove the undercolor.

In addition, it eliminates the inconveniences of additive side and proportional law failure due to color overlapping, and enables faithful color reproduction for a wide variety of input documents. In order to determine the color conversion parameters that match the input document, a professional operator adjusts a large number of A adjustment knobs to automatically adjust the optimum cutting edge and the most suitable color correction for any input document. can.

Table 2

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing the overlapping state of ink in color reproduction, Figure 5 of Techuzentsubaki is a diagram showing the combination of black and two other colors, and Figure 4 is the combination shown in Figure 6. 5 is a diagram showing the reflectance, FIG. 6 is a block diagram showing an example of a circuit configuration for achieving the present invention, and FIG. 7 is a flowchart showing the processing procedure of the processing unit 603. 8 are diagrams showing dither patterns suitable for the present invention. Y...Yellow M...Magenta C...Cyan K...Black P...Recording material 601...TV camera 603...Processing section 607...Printing section 608... ·memory

Claims (1)

[Scope of Claims] (1) In a color recording system that reproduces colors using ink of multiple colors including black, a color signal of three colors from a human-powered device is calculated based on the reflectance of each of the inks of the multiple colors. , a color recording method characterized in that at least two ink colors to be combined with black are selected, and the recording area ratios of black and the selected ink are determined respectively. (2. In claim (1), the color recording method is characterized in that the plurality of color inks are inks of four colors, including black and three subtractive primary colors. (3) Claim (1) In item (1), the color recording method is characterized in that recording with black ink is performed so as not to overlap with recording with the selected ink.