JPH023357A - Predicting method for reproducing color - Google Patents

Abstract

PURPOSE:To obtain a reproducing-color predicting method having excellent accuracy by investigating the presence of the printing of ink as a basis at every dot, counting the number of the dots of all colors existing in one picture element composed of a dot matrix and acquiring an area factor to the whole one picture element. CONSTITUTION:The N kinds of Yi, Mi and Ci in array consisting of 1 and 0 corresponding to the positions of dot matrices forming one picture element, a shape that 1 is disposed at the positions of dots to be printed and 0 at the positions of dots not printed, are combined and assigned. The array of dot patterns Yi, Mi and Ci of No.i Y, M and C in the dot patterns of N kinds is set, and either of the eight colors of W, Y, M, C, R, G, B and K is decided at every dot according to the dot patterns. The number of the dots of each color is counted, an area factor at a time when the area of the whole dot matrices made up of LMAX lines and MMAX rows constituting one picture element is represented by 1 is acquired, and the tristimulus values of colors are computed. The area factor and the tristimulus values of eight colors assigned first are substituted, and the tristimulus values of the color of an (i) picture element obtained are determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for predicting reproduced colors, and particularly to a method for predicting reproduced colors when colors are reproduced using a printer.

[Prior Art] In color printers that cannot control the density of each dot,
The so-called area gradation method is adopted, which is binary, that is, dots are printed, but dots are not printed, and represent halftone recording. This is a method in which one pixel is formed by dots of several colors, and the hue and density are changed by changing the proportion of the area printed by the dots of each color. For color printers that use binary dots, colors from Dra 1 to 1 are generally reproduced based on three colors of ink: yellow, magenta, and cyan (hereinafter abbreviated as Y for yellow, M for magenta, and C for cyan). I do. Y, M,
, when two of C overlap, red, green, blue (hereinafter red is abbreviated as R, tarino as G, and blue as B)
A dot appears. In addition, R is the overlap of Y and M, and G is the overlap of Y
The overlap between B and C consists of the overlap between M and C. Also, Y,
When M and C all overlap, it becomes black (hereinafter abbreviated as ni).

On the other hand, the part of the transfer paper that is not printed on is blurry.
(hereinafter abbreviated as W). Also, the portions that do not overlap remain as Y, M, and C. In the above case, the area ratio of the eight colors has conventionally been determined using a simple formula. For example, it is introduced on page 113 of Hiroaki Kodera's ``Image processing and practical examples in color reproduction'' ([Proceedings of the Japan Society of Printing, Vol. 23, No. 3]] - pages 1 to 122). As if
The area ratios of the eight colors are expressed by a simple conversion formula for the areas of the three color inks, under the assumption that the three color inks of YMC are mixed on average and overlap with a probability equal to 1.

FIG. 8 is an explanatory diagram when calculating the area ratio of the above-mentioned conventional example of )', M, and C. In the figure, (70) is Y, M,
41), which represents one pixel made up of C dots, shows Y printing when they do not overlap, (42) shows M when they do not overlap, (43) shows C when they do not overlap, and (
72) is Y (41), M (42).

C (43) shows the Y part that remains when they overlap on the transfer paper, <73) shows the M part that remains when they overlap, (74) shows the C part that remains when they overlap, (75) ~ (78
) corresponds to R, G, B, and K produced by the overlap of Y (41), M (42), and C (43), and (71) represents the remaining W. Y (41), M (42) C (43) when there is no overlap
), the area ratio for one pixel (70) is Ky.

W(7], )Y when Km and Kc overlap once
(72), M (73), C (74), R (75), G (
76) The area ratio of B (77) and K (78) to one pixel (70) is Ay, Am, Ac, Ar, Ag, Ab, Ak
, Aw, Y(/] ]), M(42), C(4
Assuming that B) occur in various overlapping ways with the same probability, Ay, Am, Ac, Ar, Ag, Ab, Ak, Aw
The area ratio of is expressed on average by the formula.

When the area ratio of eight colors is determined in this way, minute dots of eight colors are gathered.] The visible color of pixel (70) is the (X, Y, Z) values that indicate the color characteristics, the so-called [=stimulus value] -1 (International Commission on Illumination, abbreviated as CIE 1. Based on the 931 recommendation) Since (X, Y, Z) is created to have a linear relationship with the area ratio, it is a first-order determinant. It can be expressed.

Note that Xa, Ya, and Za are (X, '1', Z) values that indicate the characteristics of one pixel (70) as a collection of minute points;

Xw, Yw, ZIa, Xy, Yy, Zy, Xrn,
Ym, Zm, Xc, Yc, Zc, Xr, Yr,
ZrXg, Yg, Zg, Xb, Yb, Zb, Xk, Yk
, Zk exhibits the characteristics of one color when each of the 24 values WC, M, Y, B, G, R, K exists independently (X, Y, Z
) value.

[Problems to be Solved by the Invention] In the conventional color reproduction prediction method as described above, assuming that various overlaps of YM and C occur with the same probability,
Since the reproduced color is predicted by calculating the average area ratio of color dots, Y, M, C,
There was a problem in that the color and the predicted color were significantly different when the overlap was almost constant.

The present invention was made to solve this problem, and an object of the present invention is to obtain an accurate reproduction color prediction method by accurately determining the area ratio of a plurality of colors to the top.

[Means for Solving the Problems] The reproduced color prediction method according to the present invention checks the presence or absence of basic ink printing for each driver, and calculates all color dots present in one pixel consisting of a dot matrix. This method calculates the area ratio for the entire pixel and predicts the reproduced color.

[Function] In this invention, the process of calculating the area ratio of each color is to estimate the color of each dot by checking the presence or absence of basic ink for each dot 1 to The area ratio of dots I for each color is determined by counting the number of dots of a plurality of colors within one pixel, which are configured by the dots I and I, for each color.

``Embodiment'' An embodiment of the present invention will be explained below with reference to the figures.
Figure 9 is a diagram showing a schematic flowchart 1 to 1 of a reproduction color prediction method according to an embodiment of the present invention.
is the process of specifying the tristimulus values of the 8 colors that make up 11 strokes, (
2) is the process of specifying N types of dot patterns within one pixel for each of the three basic colors of ink Y1M and C, (
3) is the process of setting the array of the i-th Y, M, C driver 1 to pattern Yi MiCi among N types; (4)
is a process for calculating the area ratio of all eight colors in the above dot pattern.

(5) uses the area ratio to calculate the tristimulus value of the color of one pixel (Xi
, Y i , Z i ).

A series of processes from the process (1) for specifying the tristimulus values of eight colors to the process (5) for calculating the tristimulus value of one pixel using the two area ratio will be described in detail.

First, the tristimulus values (Xw, Yw, Zw), (Xy, Yy,
Zy) (Xm, Ym, Zm), (Xc, Yc, Zc),
(Xr, YrZl-), (Xg, Yg, Zg), <Xb
, Yb, Zb), (Xk, )' k, Z k
), and the dot patterns for YM and C are first arranged in an array of 7 dots forming a pixel, that is, 1s are placed at the dot positions to be printed, and 0s are placed at the dot positions not to be printed. Yi, MiCj<i=1
．． 2. - After performing the process (2) of specifying a combination of N types of N). Process for setting the above array (3)
, Process for calculating area ratio (4), Process for calculating tristimulus values (
5) is repeated for number 1 to number of pattern types, here N times. 1st YMC of N types of dot patterns
After performing the process (3) of setting the arrangement of the dot patterns Yi, Mi, Ci, each dot is set in 8 colors (w, Y, M, C, R, G, B, I) according to the dot pattern. [Judging which one it is and counting the number of dots of each color] Calculate the area ratio when the area of the entire area of the I-MAX rows and MMAX columns that make up the pixel is set to 1. The calculation process (4) is performed, and the process (5) of calculating the color tristimulus value from these area ratios uses the formula (B) described in the explanation of the conventional example above, and the process (4) for calculating the area ratio The obtained area ratio and. First, by substituting the tristimulus values of the eight colors specified in process (1), the tristimulus value of the color of one pixel to be sought is determined.

By performing all of the above processing, prediction of colors to be reproduced from various combinations of YM and C dots is completed.

The method for calculating the area ratio (4), which is the most characteristic process among the processes for predicting reproduced colors, will be explained with reference to FIGS. 2 to 7.

FIG. 2 is a flowchart showing the process step 4) for determining the area ratio of dots of eight basic colors from the dot pattern. In the figure, (21) is the process of initializing the number of rows and columns of the dot pattern and the number counters of 8 color dots, and (22) is the process of initializing the number of rows and columns of the dot pattern. The color of the dot is determined based on the presence/absence of the three types of dots, and the dot number counter is incremented by 1. (2B)
is a process of converting the eight color dot counter values obtained from process (22) into area ratios. Processing (22) Y, MC
The presence or absence of the three types of dots is determined by the element Yi(j!, m)MiQ! of the array consisting of the values 1 and 0 set in process (3).
, m), Ci((!, m), if each is 1, it is determined that there is 1 head, and if it is 0, it is determined that there is no dot. For example, Yi (1, m), Mi (R, m) Ci
If (#, m) are all O, dot number counter Tw of W
increases by 1, and conversely, if all 1, then the dot number counter T
Increase by k or 1. The dot number counters Ty, Tm, Tc, TrTg, and Tb of Y, M, C, RG, and B are also Y, respectively.
It is counted up from the values of i (f, m), Mi (1, m), Ci (n, m). FIG. 3 shows the conditions of YiMi and Ci corresponding to the 8-color driver 1-number counter. (31) shown in FIG. 3 is W. (32> or Y, (33) is M,
(3 4) is C, (35) is R, (36) is G, (3
7) Yi (f, m) Mi (ffi, m), Ci that satisfy the condition that B, (38) increases the dot number counter of K
(N, m> value.

less than. Number of lines 4. Taking a dot matrix pattern with four columns as an example, the method of process (4) for determining the area ratio will be explained with reference to FIGS. 4 to 7.

Figure 4 shows the dot pattern of a 4x4 dot matrix for each of Y, M, and C, and Figure 5 shows the dot pattern of the above dot pattern with array elements having values of 1 and 0 for Yi, Mi, and Ci for each row and column. Figures 6 and 7 of Table 1, written in
This is a dot matrix pattern showing the distribution of dots in eight colors when the patterns are overlapped. Not shown in Figure 4 (41
) indicates the portion where Y (42) is printed with M dots, and (4B) indicates the portion where C dots are printed, respectively. (51) shown in FIG. 5 is the value of the array element Yi, Mi, and Ci at the position of the 1st row and 1st column.
,1)=1. Mi(1,1>-〇, C1(1,])=0
and is set in the process (4) for calculating the area ratio. Similarly, the fifth
When the values are sequentially set in YiMi and Ci until reaching the 4th row and 4th column (52) in the figure, the process (22) of counting up the corresponding dot number counter according to the color for each position (2nd row, 1m column) is performed. It will be done.

Let's follow the process (22) in order using FIG.

1st row, 1st column) In (61,), (Yi, Mi, C4)
(Since 1, 0, 0>, the number of dots counter T in Y,
When y becomes 1 and (1st row, 2nd column) < 62), R's tiger 1 to number counter T+- becomes 1. (1st row, 3rd column) (6B>, R dot number counter Tr is 2.1st row, 4th column) (6
In 4), the dot number counter Tm of 1M becomes 12 (4).
By repeating the process (22) up to the position (row, column 4) (65), the number of dots is obtained, and by superimposing the MMC of Fig. 7, the results are W (71), Y (72), M ( 73)C
(74), R(75), G(76), B(77), K(
The distribution of 78) can be expressed by the numbers 1 to 1 of formula (C) in 1. The number of dots in these formulas (C) is the number of lines per line
The value of the number of columns, that is, divided by the total number of dots constituting the dot matrix, indicates the area ratio for one pixel (70) in FIG. Note that the area ratio is expressed in three significant digits.

In the above embodiment, the colors W, Y, M, C, R, and G are produced by overlapping the three basic inks of Y, M, and C for printing in the printer.

Although the case where the basic ink consists of three colors other than Y, M, and C, and the colors produced by overlapping one another become eight colors is shown, the above embodiments and the same can be applied. Similar methods can be applied.

In addition, in the case where the number of colors is different from the above embodiment, for example, when the basic colors of ink are two or four or more colors, a counter for the number of dots is set for the number of colors generated by overlapping, and a branch of the count-up condition is set. By changing the number of , the same method as in the above embodiment can be applied. For example, if the basic colors of ink are two colors Y and M, the colors produced by overlapping the two colors will be four colors W, Y, M, and R. Therefore, by counting the number of dots for these four colors, the reproduced color can be predicted.
If you add black (different from K, which comes from the overlapping of Y, M, and C) to the three colors above, the number of colors created by overlapping becomes 16 colors. Therefore, if we increase the dot number counter so that we can dot ~ numbers for these 16 colors and change the branches of the count up conditions, the reproduced color can be predicted in the same way as in the above example. .

[Effects of the Invention] As explained above, this invention counts the transfer area ratio of the color portion constituting 9 pixels for each number of dots, so it is possible to accurately predict the reproduced color and improve the accuracy of two-color reproducibility. This has the effect of allowing the printer to produce high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of a reproduction color prediction method according to an embodiment of the present invention, FIG. 2 is a flowchart of a process for determining area, FIG. 3 is a table showing the conditions for determining eight colors, and FIG. 4 is a Y , M, C 4 x 4 dot matrix pattern diagram; Figure 5 is a 4 x 4 F dot matrix pattern diagram of array elements corresponding to each position; Figures 6 and 7 are Y, M, C
FIG. 8 is an explanatory diagram of a conventional reproduction color prediction method. In the figure, (2)...processing to specify the dot pattern of the basic ink, (4)...processing to calculate the area ratio of multiple colors generated from the basic ink (5)...calculated area ratio. This process determines the characteristics of reproduced colors from Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a method for predicting the reproduction of images output from a printer,
In the dot matrix that constitutes the pixels of the output image of the printer, the presence or absence of printing of multiple basic color inks is checked for each dot, and the number of dots for each color is calculated for all colors resulting from the superposition of these basic color inks. 1. A method for predicting reproduced color, characterized in that reproduced color characteristics are predicted by calculating the area ratio for one entire pixel.