JPH0388479A - Gradation correction method for color video printer - Google Patents

Abstract

PURPOSE:To attain sufficient gradation even in the absence of R,G signals in input R, G, B signals by mixing an additive mixing primary color component not in the relation of complementary color with one primary color in 3 subtractive mixing primary colors with a subtractive mixing primary color component in the relation of complementary color and applying coloring with the mixed signal. CONSTITUTION:A trace of other primary color signal is mixed to primary color signals R(red), G(green) and B(blue) being input signals to a color video printer to convert the signals into R', G' and B' signals. Then an additive mixing primary color component not in the relation of complementary color with one primary color of three primary colors of subtractive mixture converted from the R', G' and B' signals is mixed with the primary color component in the relation of complementary color with the primary color component, resulting in producing Cy' (cyan), Mg' (magenta) and Ye' (yellow) signal thereby forming a print signal coloring the 3 primary colors for a printer. Thus, even when no green component is included and only a blue signal is included, sufficient gradation is taken.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to correcting the color gradation of a color video printer.

[Conventional technology]

Conventional color video printers use additive mixture of three primary colors, R (red), G (green), and B, as shown in the color relationship diagram in Figure 4.
Colored printing was performed using Cy (cyan), Mg (magenta), and Ye (yellow) signals, which are complementary colors of the (blue) signal, as the three primary colors of the print signal.

[Problem to be solved by the invention] The relational expression of the conventional coloring printing method using CySMg and Ye signals as the three primary colors is cy=1- R-・-・−−−−−−−(1) Ceramic=
1-G ------------(2) Ye=1-B
-1・-(3) (However, 1 represents the maximum saturation signal, and 0≦R, G, B≦1.) It can be expressed as follows, and the relationship Ye=1−B can be expressed as the electrical signal level Expressing the relationship as shown in Figure 5, for example, when the B signal, which is the color video printer input signal, changes from the O level to the 1 (Bmax) level, that is, the 100χ signal, the Ye signal of the print signal changes to 1 (Ye m
ax) level, that is, the change from the 100χ signal to the O level.

In a color video printer that uses the three signals of Cy, Mg, and Ye, for example, if there is no R, G signal and only B among the R, C, and B human input signals, the method shown in Figure 3 and As can be seen from equations (1), (2), and (3), Cy,
Mg becomes the maximum saturation signal, and the B gradation appears at the Ye gradation.

However, the darkness of CySMg at maximum saturation is much darker than that of Ye, so it has the disadvantage that the blue gradation is extremely narrow.

Therefore, it has become necessary to be able to obtain sufficient gradations even when there is no R1G weight system in the human signals of R, G, and B signals.

[Means to solve the problem]

In order to solve the above problem, the present invention mixes a small amount of other primary color signals with each of the R, G, and B primary color signals, which are human input signals of a color video printer, and converts each primary color signal into R'G'
, B' signals, and one of the three subtractive primary colors converted from the R', G'B' signals and an additive primary color component that is not in a complementary color relationship is mixed with a complementary color component in a complementary color relationship.Cy'
, Mg', and Ye' signals are print signals for coloring the three primary colors of a color video printer.

[Effect]

In the gradation correction method for a color video printer according to the present invention configured as described above, the relational expression of the three primary colors Cy', Mg', and Ye' of the color video printer is Cy'-1-
R' = 1- (R0KgX G 10KbX B) -
--(4) Mg'-1-G'-1-(KrXR+G+KbXB) ---(5
)Ye'-1-B'-1-(KrXR+KgXG+B) ---(6)(
However, each coefficient is O≦Kr, Kg, b<1.1 is the maximum saturation signal, 0≦R, G, B≦1. ), and for example, if there is no R1G weight control signal among the R', G', and B' signals, Cy'-1-R' -1-Kbx B ------
------(1) Mg' = 1-11;' = 1-
KbXB -(8)Ye'-1-B
' -1-B -・-----1----(9)
As is clear from equations (7), (8), and (9), the Cy' (cyan) and Mg' (magenta) signals do not reach the maximum saturation signal, but the blue level reaches the Ye' (yellow) signal. You can get the right tone.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tone correction device for a color video printer according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment according to the present invention, in which the three primary colors are additively mixed.
', G', B' signals or R'', G, B'' signals are passed through a matrix circuit 1 which is converted into signals of Cy, Mg, and Ye, which are the three primary colors of subtractive mixing, in a complementary color converter 2. It shows.

FIG. 2 shows a portion of the matrix circuit 1 shown in FIG. 1 in a first embodiment of the present invention, and shows an example of simultaneously correcting three primary colors of subtractive mixing.

The R signal input via matching resistor R1 is terminated at resistor R4, and the G signal input via matching resistor R2 is terminated at resistor R5 and then via matching resistor R3. The manually inputted B signal is terminated at resistor R6.

The intersection of R2 and R4 and the intersection of R2 and R3 are connected to resistor Rrg.
Connect the intersection of R2 and R6 and the intersection of R3 and R6 with a resistor Rgb, and connect the intersection of Ro and R4 and the intersection of R3 and R.
5 through a resistor Rrb.

The input signals R, G, and B are converted into R' and G'B' signals, respectively, and are expressed by the following formula: R' = R + KgXG 10 Kb
XB G' - KrXR + G0Kb
Kg, In is in the relationship of < 1.

Here, the resistance values of resistors R+, Rz, R3, R4, R5, and R6 are made equal, and the resistance values of resistors Rrg, Rgb, and Rrb are made equal, and in consideration of color fidelity, Rrg) 1/2X
If it is set to RI, the coefficient value in the above formula becomes Kr-g
= Kb, and the value is approximately R1/2...Rr
g Rr + Rrg/2 R+ /2Kr
, Kg, KbL:.

R+ /2・Rrg RrgR10 R1+Rrg/2 required by.

Kr, Kg, and b are within the practical range of 0.01~0.
If the value is 1, the three primary colors Cy', Mg', and Ye' signals of the coloring print signal of the color video printer will be Cy' = 1.
-R'= 1- (R+0.01~0.I X G +0.01~
0. IXB), and 1 to 10χ of G and Bs signals, which are not in a complementary color relationship, are included. Similarly, Mg'=1-G'-1-(0,01~0.I XR+G+O, old~0.IX
B), and the R and B signals, which are not in a complementary color relationship, are 1~IO! included. Similarly, Ye'=1-B' is 1-(0,01~0.1 x R+0.01~0.1
x c + B), and 1 to 10χ of R and G signals that are not in a complementary color relationship are included.

Fig. 3 shows a second embodiment of the present invention, in which the matrix circuit l shown in Fig. 1 can simultaneously correct the three primary colors of the subtractive mixture, and can also correct one specific color. be.

The n signal input via matching resistor R4 is connected to resistor R
4, the G signal input via matching resistor R2 is terminated at resistor R1, and the B signal input via matching resistor R3 is terminated at resistor R6. .

The input terminal of the n signal and the intersection of resistors R2 and R5 are connected through a resistor Rrg, and the intersection between resistors R3 and R6 is connected through a resistor Rrb.

The input terminal of the G signal and the intersection of resistors R8 and R4 are connected through a resistor Rgr, and the intersection between resistors R8 and R6 is connected through a resistor Rgb.

The input terminal of the B signal and the intersection of resistors R and R4 are connected through a resistor Rbr, and the intersection between resistors R2 and R6 is connected through a resistor Rbg.

The input signals R, G, and B are converted into R", G"B n signals, respectively, and are combined using the following formula: R"=R+KrgX
G + Krb X BG"-Kgr X R+ G
10 Kgb X BB' = Kbr X Rf l
1g
gr, Kgb, Kbr, Kbg are coefficients, 0≦Krg, Krb, Kgr XKgb,
There is a relationship of Kbr, Kbg<1.

Here, resistors R1, R2, R3, R4, R6, R6 are made equal, and Rrg, Rrb, Rgr,
Rgb, Rbr, Rbg) 1/2XR+, each coefficient is calculated by the following formula.

Krg'i (R+ /2)/Rgr, Kr
b # (R+ /2)/RbrKgr”,
(R+ /2) /Rrg, Kgb #
(R+ /2)/RbgKbr', (R
+ /2) / Rrb, Kbg ”i
(R+ /2)/Rgb, and the color printer's colored print signals cyan (Cy"), magenta (Mg"), and yellow (ye#) are Cy'=1-R'- 1-(R+ Krg X G + Krb
Mg"-1-G"= 1 (Kgr XR+G+Kgb XB)Ye"=
1-B"= 1- (Kbr X R+ Kbg X G + B
).

In the above embodiment, the gradations of the coloring print signals for all colors are corrected, but it is also possible to at least correct one particular color, such as blue, which is difficult to obtain gradations.

That is, when correcting only blue color, the following conditions are met.

Cy“-1-(R-1-Krb XB) Ugly” = 1-
(G+Kgb XB)Ye"=1-CKbr
XR+Kbg xG1B) Krg, Kgr
= 0 0≦Kbr, Krb, Kgb, Kbg<
1 By setting in this way, it is possible to correct the blue color.

Note that the coefficients Kbr, Krb, Kgb, Kb
The experiment was conducted by selecting a value of 0.1 or less as the value of g.

〔Effect of the invention〕

As is clear from the above embodiments, in the gradation correction method for a color video printer according to the present invention, the printing signals of the color video printer, cyan, magenta, and you, are converted into complementary color signals of red, green, and blue. During conversion, the three primary colors for printing are made by mixing a very small amount of other three signals that are not in the complementary color signal signal, so for example, even if there is no signal for red and green and only blue, the maximum saturation signal for cyan and magenta can be obtained. Zusian,
Since the darkness of the magenta color has been relaxed, it has become possible to clearly add steps in the brightness of the blue color at yellow lights.
It is especially effective for artificial images such as computer images, and as a result of reproduction experiments, it was found that with the conventional method, there was no gradation when coloring a single blue color, but with this correction method, it was particularly noticeable in blue. Yes, almost ten levels of gradation were obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram, and FIG. 2 is a first diagram of the present invention.
Figure 3 is a connection diagram showing the second embodiment, Figure 4 is a diagram of the relationship between the three primary colors of additive mixture and the three primary colors of subtractive mixture, and Figure 5 is the diagram of the relationship between yellow and green signals in electrical signals. It is a relationship diagram. 1 is a matrix circuit, 2 is a complementary color converter, R1R2, R
3, R4, R, , R6, Rrg, RBr, Rgb,
Rbg, Rrb, and Rbr are resistors.

Claims (2)

[Claims] (1) A cyan signal (C), which is a subtractive primary color that has a complementary color relationship, is derived from the red signal (R), green signal (G), and blue signal (B) that make up a video signal using the three additive primary colors.
y), magenta signal (Mg), and yellow signal (Ye).
A gradation correction method for a color video printer in which an additive primary color component that is not in a complementary color relationship with one of the three primary colors in a subtractive mixture is mixed with a subtractive primary color component that is in a complementary color relationship, and coloring is performed using the mixed signal. (2) Cyan signal and magenta signal which are gradation correction signals,
Claim characterized in that in the yellow signal, at least one set of the same plurality of sets of coefficient values for configuring the cyan signal, magenta signal, and yellow signal is set as a different coefficient value and used as a coloring signal of a color video printer. 1) The gradation correction method for the color video printer described above.