JPS60140348A - Determining device of net point area rate - Google Patents

Abstract

PURPOSE:To determine easily a net point area rate of each color print by selecting color information which is the most similar to the color information derived by a color measuring means, from the color information of a color information - net point area rate converting table, and outputting the net point area rate. CONSTITUTION:A color information data of an object to be measured is derived by a color measuring means 20, and stored temporarily in a storage means 30. A selecting means 40 compares color information of a color information - net point area rate converting table stored in a storage means 10 with the color information stored in a storage means 30, and selects that which is the most similar to color information of the object to be measured, from in the color information - net point area rate converting table. A net point area rate corresponding to color information selected by a color information selecting means 40 is outputted by a net point area rate output means 60.

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, in order to create printed matter, image information is captured from a color original, and C (cyan), M (magenta), Y (yellow), and Bk (black) are used for printing based on the image information. ) Calculate the dot area ratio of each plate and output a halftone film for each medication, or create a gravure printing plate by engraving the printing plate for each medication using a mechanical engraving method, laser engraving method, etc. There are known devices that do this.

In such a device, image information is stored in a storage device, and the arrangement of the images can be freely set, the color of a part or a specific part of the image can be modified or changed, or the color of a specified part or part of the image can be modified or changed. There are products on the market that allow you to arrange specified colors on parts in a specified manner. A typical device is commonly called a layout scanner. Devices such as such layout scanners are used to reproduce colors of image information.

When changing the color of a certain part or setting a digit in a device such as the layout scanner, the changed color or the color to be set may be specified. In such a case, if the color is specified by the dot area ratio, it is sufficient to key in the value and there will be no problem. However, a problem arises when colors are specified using color samples.

When a color is specified using a color sample in this way, the following method can be considered as a method of inputting information on the color in the form of a halftone area ratio to a device such as a layout scanner.

For example, assume that a printing layout sheet has a large number of color samples attached to it for specifying colors. For example, suppose you want to uniformly fill a background with a certain color, and a small piece of paper with the background color is attached as a color sample.

If you want to print the specified part with the same color as this color sample C
, M, Y, and Bk, to determine what dot area ratio to print, use this color sample and a color chart that is printed with the dot area ratio changed at approximately 10% intervals. The selected color is determined by visually comparing the colors and selecting the most similar one, and using the fact that the percentage of the halftone area of each plate is written on the color chart. It is common to input the information into the device. However, this method has the disadvantage that it takes time to make the comparison, and the colors selected from the color chart vary depending on the person, so that the determined halftone area ratio tends to vary. Accurately specifying the dot area ratio requires an experienced veteran, but even then it is not perfect.

On the other hand, reflection densitometers that can measure the density of an object to be measured and calculate the dot area ratio are currently on the market. In this densitometer, the measured density value is processed by a microcomputer built into the densitometer to calculate the dot area ratio. The Niel-Nielsen equation is usually used to calculate the dot area ratio from this density value. In order to use this Niel-Nielsen equation, measure the standard density in advance and set the halftone area ratio of that part to the standard value (100%).
, then it is necessary to actually measure the dot area ratio of the target object and use the relationship with the reference density.

Therefore, it is only applicable to colors that have a standard density, and is usually used only for monochrome colors. Moreover, the above-mentioned Nielsen equation can be established without dot gain (if the halftone dots are ideally reproduced, and by appropriately setting coefficients that vary depending on the screen frequency, density, and paper transparency). Therefore, in actual use, it is not possible to accurately obtain the dot area ratio over a wide range from the light part to the shadow part even if it is a single color.It is even more difficult to calculate the dot area ratio for secondary colors or higher. It is.

Therefore, such a densitometer cannot display a combination of halftone area ratios for expressing the color of a color sample for each of the 1, M, C, and Bk versions.

In addition, such conventionally known densitometers have a dot area ratio of Y, which is used to express the color of the color sample, due to the following reasons.
It is not possible to display a combination of M, C, and Bk versions. That is, the printing ink y, rv+,
The c ink is not ideal; Y ink contains M and C components, M ink contains Y and C components, and C ink contains M and Y components. Contains ingredients. Y, M used in reality
, Since the printing ink of C is not ideal, the colors of the object to be measured such as color samples are B (blue violet), G (green), and It, which are complementary colors of Y, M, and C.
Even if you calculate the dot area ratio using the Niel-Nielsen formula using the density values obtained by measuring through each filter (and RAD), the value ゛ is not actually required. Y, M
.

It does not show the dot area ratio of each screen in C.

This will be more clearly understood by the following example.

For example, it is easy to understand if we assume that an image with a dot area ratio of 100% is printed using only C ink from a certain ink manufacturer. This printed matter is applied to R filter, G filter, respectively.
If the density is calculated through the B filter, it is 1.53.
0.52.017, but these values are IL
It is clear that it cannot be used to calculate the halftone area ratio of C, M, and Y plates, which are complementary colors of G and [3.

This becomes even more complicated when not only one color of ink but a plurality of color inks are to be overprinted. Therefore, such a densitometer cannot be used to measure the halftone dot area ratio of a printing plate of each color on which the color of a color sample is to be reproduced.

The present invention eliminates the various drawbacks mentioned above, and allows any color to be changed to Y, ~1. To provide a device that can easily determine whether the halftone area ratio of each color plate should be combined to 5 when expressing with ink of each color of C or ink of each color of Y, M, C, and Bk. This is what I am trying to do.

That is, the present invention provides a color information-dot area ratio conversion table showing a correspondence relationship between color information and combinations of dot area ratios corresponding to the color information of color separation plates of three colors Y, M, and C. Bk showing the correspondence between the halftone area ratio of the Bk color separation and color information
a first storage means in which plate calculation data is stored;
a color measuring means for measuring the color of the object to be measured and storing color information; and a second color measuring means for storing the color information determined by the color measuring means.
, and the halftone dot area of the Bk plate from the color information stored in the second storage means and the Bk plate calculation data stored in the first storage means based on preset conditions. At the same time, the luster axis corresponding to the halftone area ratio of the Bk plate is subtracted from the color information stored in the second storage means. A plate halftone area ratio calculating means, a color information-halftone dot area ratio conversion table stored in the first storage means, color information stored in the second storage means, and/or a printing plate on the 11. The color information stored in the second storage means and/or the color information in consideration of the Bk plate is selected from among the color information in the color information-halftone area ratio conversion table by comparing the color information with the color information taken into consideration. a color information selection means for selecting a similar color information; and a dot area ratio output means for outputting a combination of dot area ratios corresponding to the color information selected by the color information selection means and the dot area ratio of the Bk plate. It is an object of the present invention to provide a halftone dot area ratio determination device characterized by comprising the following.

Note that as the color information, color density, chromaticity, etc. can be used as a reference. In the following, the case where color density is used will be mainly explained for simplicity, but the same process can be performed even when chromaticity or the like is used as color information.

That is, it is well known that color density and chromaticity are used as one of the methods of expressing a certain color, that is, one of the color representation methods.

R (red), G (green), and B (blue violet) color systems are well known as color systems for color density.

The color system for chromaticity is the XYZ color system (CI E (19
31) XYZ color system), l, 'a'b1 color system (CI E
1976(L'a'b') -Color 5pac
e) isospecies her') are known. In the XYZ color system, chromaticity, where x, y, and z are tristimulus values, is expressed as the chromaticity difference △E. = ((Y+-Y2)2+(x+-x
z)2+(y+-y2)2)"2.

In addition, in the Lab color system, chromaticity is expressed as chromaticity, a, b, and the closeness of two colors is chromaticity difference 2, k, +a2.
Table 217 E= ((Ll-L2)→-(al-a2) + (
bl - b2)).

As described above, chromaticity and chromaticity difference are used to express colors and the closeness of colors.

The aforementioned color density and color density difference are also used as methods to express colors and color closeness, but it is more convenient to use chromaticity and chromaticity difference when handling colors numerically. Special ICL'a
The 'b' system is excellent for quantitatively handling colors that are close to the colors that humans perceive.

The present invention provides an apparatus that can measure the chromaticity, color density, etc. of an object to be measured and easily determine the dot area ratio of each color plate when expressing the color of the object in print. This is what we are trying to provide.

Next, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 is a conceptual diagram of the device of the first invention of this application,
The first storage means (10) stores color information and the color separations of a plurality of colors in advance! Color information-dot area ratio conversion table showing the correspondence with the combination of halftone area ratios corresponding to N and Hk plate calculation data showing the correspondence between the halftone area ratio of the Bk color separation plate and color information is memorized, and the pressed 1
The color information data determined by the color measuring means (20) for storing color information data of a fixed object is temporarily stored in the second storage means l30). As the color information data stored in the second storage means G30), for example, the color density of the object to be measured is determined by combining three types of color density obtained through each of the R filter, G filter, and B filter. This may be a combination of sets or chromaticity. Next, color information selection means (4
(2) is the color information of the color information-dot area ratio conversion table stored in the first storage means (1o) and the color information of the object to be measured stored in the second storage means (30), or as described below. The color information of the object to be measured or the +31 Select the closest one.

On the other hand, the Bk dot area ratio calculating means (50) calculates the color information stored in the second storage means (301) and the color information stored in the first storage means (IOJK) based on preset conditions. Calculate the halftone dot 5 area ratio of the Bk version from the Bk version calculation data, and subtract the lust axis corresponding to the halftone dot area ratio of the Bk version from the color information stored in the second storage means f301. It stores color information that takes the Bk version into consideration.

In this case, the Bk halftone area ratio calculation means (50
The processing by the color information selection means (4tj) selects the color information closest to the color information stored in the second storage means, and determines the conditions for Bk plate calculation based on the selected result. You may ask them to do it later, or
[It is also possible to determine the conditions for the 3k plate calculation and to perform the processing by the Bk plate halftone area ratio calculation means (50) before the processing by the color information selection means (40) K, It is convenient to be able to switch which one to perform.

After the processing by the Bk halftone area ratio calculation means (50) is completed as described above, the color information selection means (40) selects the color information closest to the color information considering the Bk version. Selected from the dot area ratio conversion table.

In this way, the combination of dot area ratios corresponding to the color information selected by the color information selection means (40) is interpolated by the interpolation means as necessary, and then the dot area ratio output means f60 outputs the dot area ratio. ) Output from K.

As described above, when expressing the color of an object to be measured (for example, a colored book) by printing with printing ink, the halftone area ratio at which each color of ink should be printed can be easily determined.

Figure 2 (al, (bl) shows an example of a color information-dot area ratio conversion table when color density is adopted as color information. shows the combination of color densities obtained through each of the R filter, G filter, and B filter, and the right side shows the combinations of Y, M, and C corresponding to the color density combination shown on the left side 1. Only combinations of dot area ratios of three color separations are shown.

Such a color density-dot area ratio conversion table is created as follows. First, print Y and M on the printing paper.

Using each ink of C0, dot area ratio 0% to 100%
at appropriate intervals, for example 1 as in the case of Figure 2.
A color chart is created by actually printing by changing the spacing to 0%. That is, in the example of FIG. 2, numbers 1 to 11 are 1. Y.

The plates have a dot area ratio of 0%, and only the C plate is changed from 0% to 100% in 10% increments, and numbers 12 to 22
Until now, the halftone area ratio of the Y8 version was 0%, and the halftone area ratio of the M version was 1.
0%, and only the C plate was changed in 10% increments between 10% and 100%.Hereinafter, various halftone dot area ratios of each Y, M, and C plate were changed at a 10% spacing. Create a color chart based on the combination. Such a combination is Y, M,
C.

When the halftone dot area ratio is changed at an interval of 10% for each version, 11 = 1331 combinations are generated.

For each color of the color chart created as described above, the combination of color densities obtained through the R filter, G filter, and B filter is determined.

As described above, a color density-dot area ratio conversion table is created that shows the correspondence between combinations of color densities and corresponding combinations of halftone area ratios of plates of each color for various colors.

Further, FIG. 3 shows the dot area ratio and f(,
It is a table showing the correspondence relationship with color density through each of G and H filters.

Similarly to the creation of the color density-dot area ratio conversion table, the dot area ratio of the plate is changed in 10% increments in step 13, and after actual printing, the RoG and B filters are applied. It is obtained by measuring color density through - Naori K version calculation data is not in the form of a table as shown in Figure 3, but is expressed in a graph as shown in Figure 4 using the method of least squares at °C based on the data in the table. This form of function may also include functions such as .

Although it is common to measure color density using the f(, G, and B filters) mentioned above, it is possible to measure color density using filters such as interference filters that have a peak in the absorption part of the spectral reflection curve of printing ink. The same filter used when creating the color density-dot area ratio conversion table must be used when measuring the color density of the object to be measured.

Looking at the color density-dot, Ij, 1 area ratio conversion table obtained as above, for example, numbers 1 to 11 in FIG.
Up to this point, the dot area ratio of each M, Y, and Y plate is 0% and does not change, and only the C plate changes. Just (,
The color density through the other G, B, and amber filters also changes.

This is because the C ink contains not only the C component but also other color components.

This relationship holds true for other inks as well, and they contain other components. Therefore, when determining the halftone dot area ratio of an object to be measured, it is also necessary to take into account the color density through a σ) filter, which is equivalent to a lath passive filter. The data of the color density-dot area ratio conversion table and the data for Bk plate calculation are stored in the first storage means (10), and such storage means include magnetic disks, floppy disks, 1( An appropriate value such as 0 or 1 is used.

As described above, the color information-dot area ratio conversion table and the Bk plate calculation data are stored in advance in the first storage means (10).

Further, the color measuring means (20) measures the color of the object to be measured to obtain color information, and FIG. 5 is a block diagram showing one embodiment thereof. The example in FIG. 5 shows an example in which color density is used as color information, and an object to be measured (1) such as a color sample is irradiated by a light source (21),
The reflected light is input to a photoelectric conversion element (23) via a filter (22), where it is converted into an electrical signal. The filter (22) is the same as the one used when creating the color density-dot area ratio conversion table, and 1 (three types of filters, fillet letter, G filter, B filter, etc.) are installed so that they can be converted. In this case, the filter can be switched electrically or manually.In addition, in the example shown in Figure 5, the light from the light is Although it is designed to emit light from an angle of 45 degrees and receive the light directly above, it is also possible to emit light from directly above and receive the light at a 45 degree angle (・.

The electrical signal generated by the photoelectric conversion element (23) is sent to the amplifier (
24), is amplified by the correction circuit (25), is subjected to logarithmic conversion processing by the logarithmic converter (26), and is converted to A/
The D converter (27) converts the analog signal into a digital signal, and inputs the color density as color information to the second storage means (7) and stores it. Furthermore, the electric signal is a trap so that its value can be checked on the display meter (28). Note that the display meter (28) may be placed after the A/I converter (27) to provide a digital display.

As described above, the object to be measured is measured for each filter to obtain color information of the object to be measured, and these are stored in the second storage means 00) as described above. As the second storage means, an appropriate one such as a RAM can be selected.

The color information selection means (40) includes, in part, a second storage means (3).
0) and the color information of the object to be measured stored in the first storage means (
10) Compare the color information stored in the color information-dot area ratio conversion table with the color information in the color information-dot area ratio conversion table, and select the one closest to the color information of the object to be measured from among the colors and reports in the color information-dot area ratio conversion table. The selection is made as follows. For example, when color density is used as color information, the color density of the object to be measured is DR%Da, which is obtained through each of the I (filter, G filter, and B filter).
Da, and the It filter, G filter, K at the nth number of the color information-dot area ratio conversion table, and the color density-dot area ratio conversion table.
The color density through the filter is T u(nl,
TG(nl, Tn(nl).Next, the combination of color densities of the object to be measured DRlDa, DB and the combination of the nth number of color densities in the color density-dot area ratio conversion table Tn( nl.

A combination of color densities TR(nl, Tc(nl,
TB (take nl.

Distance SA(nl is (SA(nl) 2= (T+t(nl-Da E 2
+ (Tc(nl-Dc) 2+ (1'B(nl-
It can be determined from the relational expression Ds ) 2 .

The value of n where the distance 5A(nl) is the minimum matches the value of n where the distance (5A(nl) is the minimum. Therefore, using the above relational expression, the color density such that rsA(nl)2ka'jtThJ\ -N = combination of color densities in the halftone area ratio conversion table
By searching by changing the value of n sequentially from 1 to the end, we can find the value of n that minimizes 5A (nl). 5A
The combination of color densities in the color density expansion-halftone area ratio conversion table corresponding to n that minimizes (n) is determined as the one closest to the combination of color densities of the object to be measured, and the combination of color densities is The combination of dot area ratios of the corresponding Y, M, and C versions is determined.

In this case as well, if (5A(nl) 2) becomes zero during the search, that is, during the search, the combination of the color densities of the object to be measured and the color density in the color density-dot area ratio conversion table If a match is found, the subsequent search may be discontinued since the data determines the combination of halftone area ratios corresponding to the combination of color densities at the current value of n.

Although color information is selected in the manner described above, the same process may be performed even when chromaticity or the like is employed in addition to color density as color information.

The combination of dot area ratios of the Y, M, and C versions determined as described above is outputted by the dot area ratio output means K.The dot area ratio output means outputs the determined dot area This is for outputting the rate, and a display, printer, etc. can be used.

The combination of the halftone dot area ratios output as described above indicates the halftone dot area ratio of each plate, and if the combination of the halftone dot area ratios outputted in this way is used to print with each color ink, 6111 It is possible to obtain printed matter with the same or similar color to the regular object. For example, if the 125th color density is selected as the closest color density to the combination of color densities obtained by measuring the object to be measured, then from the table in Figure 2, the 0th edition is 30%.
, the M version is output as 0%, and the Y version as 10% by the dot area ratio output means.

By the way, it is well known that depending on the combination of dot area ratios output in this way, a portion of them can be replaced with Bk ink. Therefore, in the present invention, a human determines whether or not it can be replaced with Bk ink based on the content of the combination of outputted halftone dot area ratios. The means (50) is used to make it. Alternatively, conditions for replacing with Bk ink can be set in advance, and when the conditions are met, the color information selection means (combination of halftone area ratios corresponding to the color information selected in the phrase) B without outputting it by the output means or with outputting it.
K-plate halftone dot area ratio calculation means (50) It is also possible to calculate the halftone dot area ratio of the Bk plate.

Alternatively, the operator may visually check the color of the object to be measured and determine in advance whether it is better to replace it with Bk ink. In this case, if it is determined in advance that a portion of each of Y, M, and C inks is to be replaced with Bk ink, the one closest to the color information stored in the second storage device is selected. It is also possible to directly enter the processing by the Bk halftone dot area ratio calculation means without going through the above-mentioned steps.

It is desirable to be able to switch so that any one of these can be selected.

To determine whether or not to perform processing by the Bk halftone dot area ratio calculation means based on the combination of halftone dot area ratios corresponding to the color information selected by the color information selection means (40), proceed as follows. Good.

First, for brown and gray colors, use Bk ink, Y, M,
It is a color for which it is better to replace a part of the ink of C, and whether or not it is such a color is one criterion for judgment. For example, to judge whether the color is brown or not, the dot area ratio of C, M, and Y should be 10 to 80%, 50% or more, and 50% to 50%, respectively.
It is possible to adopt a criterion of whether or not the condition of % or more is met.

For example, to determine that it is gray, C0 to 1. The difference between the Y halftone area ratio of i10 large and small is 20
It is possible to adopt the condition that it is within %.

Furthermore, LlkBk ink 1M can also be used for dark colors that cannot be expressed with normal three-color printing of Y, Iul, and L:.
, Y may be successfully expressed by replacing part of the three colors of ink.

For dark colors in such a case, for example, the halftone area ratio of the object to be measured is all 10% or more, and at least one of the colors is 100% (or 100% in the case of interpolation processing as described below). (It may be more than that). For example, in the case of dark blue, the dot area ratios of C, M, and Y are 115%, 30%, and 10%, respectively. When actually printing this, you have to print C as 100%, but
If you do this, the color balance will be disrupted. Therefore, other colors are normalized so that 115% of C becomes 100%, and the halftone area ratio of C, M, and Y is 100% and 26%, respectively.
, 9%, the color becomes insufficiently dark compared to the color of the object to be measured.

In such colors, C0 to l depending on the Bk version.

By replacing part of the Y ink, the same color and satisfactory density can be obtained. Therefore, the criteria for determining whether or not it is better to replace such a dark color with Bk ink is, for example, if the halftone area ratio of C, M, and Y is all 10% or more, and at least one color is is 100
% (or 100% or more).

Whether or not the above conditions are met can be determined automatically as described above, or by a human being based on the results output by the halftone area ratio output means. It's okay.

Next, the processing by the Bk halftone dot area ratio calculating means will be explained.

First, as an initial setting condition, it is necessary to decide at what ratio the Bk version is to be input.

Originally, the Bk version is used nine times to compensate for the lack of density in a part of the shadow, so it only needs to be used from the middle to the end. This is called skeleton black. However, if the theory of color reproduction is H, then B
For the K version, you can use the divine style, starting from skeleton black to full black, which uses as much of the Bk version as possible and suppresses the 3-color version as much as possible.
There are many combinations in which the printed results can be made exactly the same by appropriately changing the amount of three-color plates depending on the format of the K-plate. Figure 6 shows the tone reproduction curves of skeleton black and full black, and between them, the density of the middle 127th to lowest σ version of various formats is replaced with the Bk version. No. 92 shows cases in which full black and medium black Bk versions are adopted, respectively. Among these various Bk version formats, it is necessary to decide in advance which format to use. Based on the determined Bk version format, the halftone area ratios of the Bk version and the three-color version are determined.

Next, looking at C1 measured through R, G, and B filters, C1
The concentration is the lowest value. How much of this concentration is 1
3. Whether to replace it with the version depends on the Bk version format determined by Rufj. If it is full black, the entire density of C plate will be replaced by 13k plate, and if it is intermediate black or skeleton black, Bk will change variously depending on the above conditions.
Replace C plate density with plate. The density of the C plate to be replaced with this Bk plate is BR.

Next, using the Bk plate calculation data stored in the storage means of Pigeon 1, it is determined what percentage of the dot area ratio of the Bk plate is required. Examples of the data for calculation of the sumi version are shown in FIGS. 3 and 4. The horizontal axis of i 4 +X+ is the Bkk print area ratio, and the vertical axis is 1(. The density measured through the G and B filters is respectively.

The density BR to be replaced with the Bk version obtained above, and ■+
By finding the intersection point with the density measured through the filter and reading the value on the horizontal axis at that point, the dot area ratio of the Bk plate can be determined. By reading the density through the B and G filters at the determined halftone dot area ratio of the Bk plate,
3, the densities Bc and BB of the M plate and Y plate, which are replaced by the plate, can be seen.

Next, calculate the density value of each remaining plate that will not be replaced with the Bk plate.
Densities D'R11) 'c, D' that are not replaced with the Bk version for the densities passed through the R, Cr, and B filters
B can be calculated using the following formula.

D'R= DR-BR D'c = Dc -BG D'B = DB -BB Note that Dn, Da, I)B is the I(
. G, concentration through +3 filter, BR, Bc, B
B is each density to be replaced with 13 plates. D
'R, D'c, I)'B is color information in consideration of the Bk version when color density is adopted as color information.

The same thing can be done when using chromaticity or other information other than color density as color information.

Using the color information in consideration of the Bk version determined as described above, the color information selection means selects the color information closest to the color information in consideration of the Bk version in the color information-dot area ratio conversion table. Choose from among them.

The combination of dot area ratios corresponding to the color information selected in this way and the dot area ratio of the Bk plate are determined by the dot area ratio output means 60)
is output by

Note that the color information closest to the color information stored in the second storage means is selected from the color information-halftone area ratio conversion table, and the Bk plate is created according to the result of calculating the corresponding halftone area ratio. There are cases in which a combination of dot area ratios is considered, and in such a case, the color information stored in the second storage means is stored in B.
The color information selection means may perform processing by replacing the color information with color information that takes into account the K version.

Printers, display tubes, c
A display device such as a +t'r display can be employed. Further, in order to input the determined dot area ratio to an external device such as a layout scanner, it may be outputted to a data storage medium such as a professional disk, magnetic tape, or paper tape, or it may be directly outputted to an external device. Good too.

The accuracy of the halftone dot area ratio determined as described above depends on the accuracy with which the halftone dot area ratio in the color information-halftone dot area ratio conversion table is created. Second
In the example shown in the figure, the halftone dot area ratio is changed at 10% intervals, so the accuracy is up to 10%.

Therefore, if you need a more accurate halftone area ratio, you can create a color information to halftone area ratio conversion table with the required accuracy. The amount of data in the dot area ratio conversion table becomes extremely large, and creating such data is extremely time-consuming and requires a storage device with a large storage capacity. This method has the disadvantage that it takes a long time to perform comparison calculations with measured data.

In the following, we will discuss interpolation to eliminate such drawbacks and determine the halftone area ratio at intervals finer than the data interval of the halftone area ratio in the color information-halftone area ratio conversion table. Give an explanation.

First, as mentioned above, when the color information selected by the color information selection means (decoy) is the distance 5A=OO, that is, the color information is selected as a result of completely matching the color information of the object to be measured or the color information considering the Bk plate. If so, the corresponding combination of dot area ratios is directly outputted by the dot area ratio output means (60).
You can output it using . However, if the selected color information is selected in a case other than 5A=0, the halftone area ratio corresponding to the selected color information is interpolated to further improve the color of the object to be measured. To output a combination of halftone area ratios that can print colors close to . The interpolation of the dot area ratio may be performed by an appropriate method, and a dot area ratio interpolation means for this purpose may be provided as desired.

How to interpolate the dot area ratio will be described below based on its implementation.

First, select the one closest to the combination d (DR, Dc, DB) of the chromaticity of the object to be measured from the color density-dot area ratio conversion table with halftone dot area ratio or 10% interval as shown in Figure 2. and the combination of color densities is t (TR1′1゛G,
1゛B), and the corresponding combination of halftone area ratios is P(
C, m1y). In this case, for example, the dot area ratio is 1%
We also accept orders from customers. In this case, the dot area ratio to be found is 10 with P as the center.
%, ie, 5%, in the direction of magnitude.

In Figure 8, the dot area ratio is shifted by 5% in the direction of size with P as the center, and each point is represented by C, M, which represents the dot area ratio.
A expressed in the Y coordinate system (c+5, m-5, y+5
), B(C+5, m+5, y+5), C(c+5, m+
5, y-5), D(c+5, m-5, y-5), E(c
-5, m-5, y+5), F(c-5, m+5, y+5
), G (c-5, m+5, y-5), l-1 (C-5,
m-5, y-5), and there is a dot area ratio that fits into a solid having these points as vertices.

Therefore, this three-dimensional object is divided into five parts as shown in Fig. 8 according to the required accuracy, and for each combination of halftone area ratios shown by each grid point, a combination of chromatic degrees is determined, and the distance of color density is determined. All you need to do is to select the point where the distance is the minimum using the formula, and determine the combination of dot area ratios at that point as the combination of the dot area ratios with the accuracy reduced. , E.
Although the dot area ratios of points F, G, and I-1 are known as described above, the corresponding color densities are unknown.

Therefore, A'(C+10, m-1
0, y+to), B'(c+'lo, m+10, y-1
-10), C1 (c+10.1η+10, y-10),
D'(C+101m-10, y-10), E'(c-1
0, m-10, y+10), F'(c-10Sm+10
,y+10),G(C-10,m+10,y-]0)H
'(C-10, m-10, y-io) array K's respective loyal points) (c, m-10, y + t O), J (c-m+1
o, y+10), K(c, m+ IQ, y-10),
L (c, mouth]-10, y-10), M (C+10, m,
y+10), N(c+10.m+10,y), O(c+
10, m, y-10), Q(C+I 01m-10, y
), R(c, m, y+10), S(c, m+IQ
, y)T(c, m5y-10), U(c, m-10,
y), v(C-10, m, y+10), W(c-10,
m+101>'), X (c-10, m, y-10), Y
(c-10, m-10, y), Z(c+]o, m, y)
, ZZ (c-10, m, y) can be known from the color density-dot area ratio conversion table, so
First, using the color density values of each of these points and the color density value of point P, (
- Interpolate and calculate the color density introduction of each of the points A, B, C, D, E, F, G, and l-1.

FIG. 9 shows the position of each point 10% away from point P in the C, M, Y coordinate system representing the halftone area ratio. First, we will explain how to determine the combination of color densities at point A (C+5, m-5, y+5) by interpolation.
(c+10, m, y+10), Z(c+10, m,
y), Q(c10, m-10, y), I(cSm-
10, y+10), R(c, m, y+10), P
(c, m, y), U(c.

m-10, y) is located at the center of the cube. Therefore, calculate the average of each color density component of points AI, M, Z, Q, I, R, P, and U, and use that value as the color density component of point A, that is, the combination of 〇 color density to point.

Note that if the color density-dot area ratio conversion table is not created using equally spaced dot area ratios, the points A-1M, Z
The solid composed of SQ, I, R1P, and U may be a rectangular parallelepiped rather than a cube, and in that case, the distance of point A from each vertex of the rectangular parallelepiped will be different, so the distance from each vertex will be All you have to do is 5&C using a proportional calculation formula or an appropriate function.

Similarly, other points 13, CS L), E, I・', G,
For each of 1-1, each color density combination is calculated.

As above (points A, B, C, D, E, l'', G.

Now that we have found the combinations of color densities for all 14 points, we can use the color densities of these points to find the color densities of each grid point, dividing the cube at required intervals as shown in Figure 8. The combinations are determined using an appropriate method such as proportional allocation in the same manner as described above. Next, the combination of the color densities of each grid point determined in this way and the color densities of the object to be measured d (DR, D
A grid point is selected such that the distance SA between the two points (C, DB) is the minimum trap. At the grid points selected in this way, the combination of the dot area ratios is usually known, so the combination of the dot area ratios is the combination of the dot area ratios of the object to be measured P(
c, m, y) is output from the dot area ratio output means (60) as data obtained by interpolating the data.

By the way, points A, B, and C as shown in FIG.

Determining the combination of color densities at all the grid points with the required precision for all areas D, E, F, G, and H requires a large number of grid points, which makes processing difficult. Therefore, consider eight small solid bodies whose diagonal lines are the lines connecting point P and each vertex in FIG. In this way, the desired combination of color densities will be included in one of these small solids. Where it is included is determined by the combination d (DR, DC,
DB) is determined based on which point of the combination of color densities of vertices A-H is closest to the combination.

Once a small solid is determined in this way, the combination of color densities of each lattice point separated by the required precision is interpolated only for this small solid, and then the combination of color densities of each lattice point in this small solid is interpolated. Combination d (D
The grid point closest to R, DG, DB) may be selected. In this way, the calculation time can be reduced by about 8 minutes.

When the color information in the color information-dot area ratio conversion table and the color information of the object to be measured completely match, the dot area ratio output means outputs the dot area ratio corresponding to the matched color information. If they do not match completely, a combination of halftone area ratios interpolated as described above is output.

The required halftone area ratio can be entered using a numeric keypad, etc. (ゝ0 Figure 10 is an explanatory diagram of another interpolation method. B
The axes represent the color density obtained through the R, G, and BQ filters, respectively, and the color density combination t(TR, Ta, 1' B )
is expressed as the origin.

Here, if we set the vector Btd(Un, Bc, BB), Bn gate DR-TR, BG=DG-Tc, Bn
It becomes agony D s -1' B .

In addition, for the combination P (c, m, y) of the dot area ratio corresponding to the color density combination t, the dot area ratio is shifted by 1 unit (i.e., 10% in the case of FIG. 2). Set the combination Ps (c soil 10, m ± 10, y ± 10), and set the corresponding color density combination t5 (1'a5.1
G5, TBS) can be known from the color density-dot area ratio conversion table.

The dot area ratio Ps (c±10.m±10.y±i
o) Whether to take a positive or negative value is determined depending on whether each component of the vector Brd (BR, BG, BB) is greater than or equal to zero but less than zero; if it is greater than or equal to zero, it is considered positive; If it is also small, it is considered a negative value. In this case, the blades to be adopted for C-10, m±10, and y±io are determined by the blades of BR, BG, and Ba.

Then, color information data in the vicinity of the color information selected by the color information selection means is selected from the color information-dot area ratio conversion table. Color information data in this vicinity can be expressed by that number.

can be expressed as a composition of several vectors.

For the sake of simplicity, the following description will be made assuming that each component of the vector Btd is greater than zero, but the same process can be performed even in other cases.

The combinations of dot area ratios when the C component increases by 10% and when the C component and m component each increase by 10% with respect to the combination of dot area ratios P (c, m, y) are respectively Pl (c-1-10, m, y), P2 (C+10
5m+10,y).

The combinations of color densities corresponding to the combinations Pl and P2 of the dot area ratios are t+ (Ta1, Tc+, To+) and t2 (Th2, Th2,
Tc2, T, n2).

Therefore, vector Btts is vector Btt+, Bt+
t2, air t1♀Yuqj 12-1-Bt by Jo 21g
2L5 ='i mountain and K Yo-CCLjrt t+
-1-5t j t2 + 7”B1,1.i,l!:
Li can be expressed.

Here, since each component of the vector Btd (Ba, BG, 13B) is known as described above, c(7 is subtracted from the above relational expression).

Therefore, the combination d (DR, Da, D
A combination of halftone area ratios P(c, 1n, -y
) Interpolated dot area ratio combination 1) l(CI, ml,
y') is c' since the table in Figure 2 is at 10% intervals.
= c −1−(Xx i.

m'=m-10βXl0 Y' = y + jxl.

becomes.

As described above, the combination pl (C
I, ml, yl) are determined.

Note that there are various methods of expressing the vector 1tts as a composition of other vectors in addition to the above, and any vector may be used.

However, in order to obtain a reasonable interpolation value, as shown in FIG. It is preferable to select

If the vector method is adopted in this way, the processing time required for interpolation to find the combination of highly accurate dot area ratios will be extremely shortened.

Furthermore, the interpolation of the dot area ratio can be performed in a similar manner not only for color density but also for chromaticity.

11 and 12 are 1-flow charts showing how the halftone area ratio is determined in the present invention, and FIG. 11 shows the second memory selected by the color information selection means. This is a case where it is determined whether or not a Bk plate is necessary based on the result of the halftone area ratio corresponding to the color information closest to the color information that has not been stored in the device.
This is for the case where you have already decided that you need the K version.

Since the present invention has the above configuration, it has the following effects.

First of all, according to the device of the invention of this application, even if the color to be reproduced in printing is specified as an actual color, such as in a color sample, it is easy to use even without experience. Moreover, it is possible to determine the halftone dot area ratio of the halftone positive of each color to reproduce the designated color in a short time.

Next, according to the device of the invention of this application, the dot area ratio of the dots of each plate is always determined in a standardized form, unlike the conventional method in which humans judge it, so the quality of printed matter can be controlled. becomes easier.

Further, according to the invention of this application, in addition to the above-mentioned effects, by further employing an interpolation means, it is possible to determine the halftone area ratio with the necessary accuracy extremely easily.

In addition, as a color sample, the color when no plate is required for 13 is often used, but even when a plate is required for 13, the present invention determines the halftone area ratio considering the Bk plate. be able to. In this case, according to the present invention, there is no need for a color density-dot area ratio conversion table in which the dot area ratios of the four versions of Y, M, and C1Bk are all changed with a predetermined precision and combined. , and C, and the data for calculating the Bk plate are all that is required, and the storage capacity can be saved and the calculation time can also be shortened.

[Brief explanation of drawings]

(bl is an explanatory diagram of a color density-dot area ratio conversion table, FIG. 3 is a table as an example of Bk plate calculation data, FIG. 4 is a graph of functions as an example of Bk plate calculation data), FIG. 5 is an explanatory diagram of a color measuring means; FIGS. 8, 9, and 10 are diagrams for explaining the method of interpolation processing of the dot ml area ratio; FIGS. 11 and 12 The figure shows a flowchart of an example of determining a combination of halftone dot area ratios using the apparatus of the present invention. Storage means (20)...Color density measurement means (21)・Light source (22)
)... Filter (23)... Photoelectric conversion element (24
)...Amplifier (25)...Correction circuit (26)...
・Logarithmic converter (27)...A/D converter (2
8)...Display meter (30)--Second storage means (40)...Color density selection means (5o)...Bk
Plate halftone area ratio calculation means (60)... Halftone area ratio output means Patent applicant: Toppan Printing Co., Ltd. Representative: Kazuo Suzuki Figure 3 Figure 4 Figure 6 Figure 6) (i) (0L) (b) ( , M Y e r'l Y Bt 笥7fig.

Claims (1)

[Claims] (1) A color information-dot area ratio conversion table showing the correspondence between color information and combinations of dot area ratios corresponding to the color information of the three color separations of Y, M, and C, and the color of Bk. a first storage means that stores Bk plate calculation data indicating the correspondence between the halftone area ratio of the separation plate and color information; and a color measurement unit that measures the color of the object to be measured and stores color information. means, a second storage means for storing the color information determined by the color measuring means, and a color information stored in the second storage means based on preset conditions and the color information determined by the first color measurement means. The dot area ratio of the Bk plate is calculated from the Bk plate calculation data stored in the storage means of the second storage means, and the color tone corresponding to the dot area ratio of the Bk plate is stored in the second storage means. Bk halftone dot area ratio calculation means for subtracting color information considering the Bk version from existing color information; a color information to halftone dot area ratio conversion table stored in the first storage means; and the second The color information stored in the storage means and/or the color information considering the Bk plate are compared, and the color information of the color information-halftone area ratio conversion table is stored in the second storage means. a combination of halftone area ratios corresponding to the color information selected by the color information selection means, and a combination of halftone area ratios corresponding to the color information selected by the color information selection means; 1. A dot area ratio determining device comprising: a dot area ratio output means for outputting a dot area ratio of a printing plate. (2) The combination of halftone area ratios corresponding to the color information selected by the color information selection means is interpolated by the interpolation means that performs interpolation processing based on the color information-halftone area ratio conversion table. A dot area ratio determination device according to claim 1, characterized in that: