JPH0449104B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides C (cyan), M
This invention relates to an apparatus for determining the halftone dot area ratio of each plate (magenta), Y (yellow), and Bk (black).

Conventionally, a large number of color samples for specifying colors may be attached to printing layout sheets. For example, if you want to fill the background uniformly with a specific color,
A small piece of paper with the background color is attached as a color sample.

When printing a specified area with the same color as this color sample, to determine what halftone area ratio to print each CMYBk plate, set the halftone area ratio at approximately 10% intervals from this color sample. Visually compare the printed color charts with the different colors and select the one that is most similar. Generally, decisions are made based on what is written. 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 Yule-Nielsen equation is usually used to calculate the dot area ratio from this density value. In order to use this Yule-Nielsen equation, measure the standard density in advance and set the halftone area ratio of that part to the standard value (100%).
It is necessary to set the dot area ratio to , then actually measure the object to be measured for the dot area ratio, 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 Yule-Nielsen equation can be established by ideally reproducing halftone dots without dot gain, 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 a wide range of dot area ratios from light areas to shadow areas even in monochromatic areas. Furthermore, it is extremely difficult to calculate the dot area ratio of secondary colors or higher.

Therefore, such a densitometer cannot display a combination of dot area ratios for each YMBk version to express the color of the color sample.

Further, such conventionally known densitometers cannot display the combination of dot area ratios for each YMCBk version for the following reason. In other words, printing ink
YMC 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. Since the YMC printing ink actually used is not ideal, the colors of the measured objects such as color samples are B (blue violet), G (green), and R (red), which are complementary colors of YMC. Even if you calculate the dot area ratio using the Yule-Nielsen formula from the density values obtained by measuring through each filter, the value will not match the actually required dot area of each positive YMC. It does not indicate the percentage.
This will be more clearly understood by the following example. For example, it is easier to understand if we assume that an image with a halftone dot area ratio of 100% is printed using only C ink from a certain ink manufacturer. If we calculate the density of this printed matter through an R filter, a G filter, and a B filter, we will get 1.53, 0.52, and 0.17, respectively.If we consider these values to be complementary colors of RGB,
It is clear that it cannot be used to calculate the dot area ratio of the CMY version. This becomes even more complicated when not only one color of ink but a plurality of color inks are to be overprinted.

The present invention eliminates the various drawbacks described above, and when expressing any color using ink of each YMC color or each color of YMCBk, it is possible to determine the dot area ratio of each color plate. The purpose is to provide a device that can easily determine which combinations should be used.

That is, the first invention of this application is a color density-dot area ratio conversion that shows the correspondence between a combination of color densities and a combination of halftone area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors. a first storage means in which a table is stored; a color density measurement means for determining the combination of color densities of the object to be measured; and a second storage means for storing the combinations of color densities determined by the color density measurement means. a storage means, a combination of color densities of a color density-dot area ratio conversion table stored in the first storage means and a combination of color densities of the object to be measured stored in the second storage means; a color density selection means for comparing and selecting the combination of color densities closest to the color density combination of the object from among the combinations of color densities in the color density-dot area ratio conversion table; It is an object of the present invention to provide a halftone dot area determination device characterized by comprising a halftone dot area ratio display means for displaying a combination of halftone dot area ratios corresponding to a combination of color densities.

Further, a second invention of this application provides an apparatus that can obtain more detailed combinations of dot area ratios using a table similar to the color density-dot area ratio conversion table used in the first invention. This is what I am trying to do.

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

FIG. 1 is a conceptual diagram of an apparatus according to the first invention of this application, in which a combination of color densities and a combination of color densities of a plurality of color separation plates are stored in advance in a first storage means 10. A color density-dot area ratio conversion table showing the correspondence relationship with combinations of dot area ratios is stored, and the color density determined by the color density measuring means 20 for determining the combination data of the color densities of the object to be measured is stored. The combination data is temporarily stored in the second storage means 30. As the color density combination data stored in the second storage means 30, for example, three types of color density obtained by passing the color density of the object to be measured through each of the R filter, G filter, and B filter are used. For example, a combination of a set of filters or an amber filter or
This is a set of four types of color densities, including the color densities obtained through an ND filter. Next, the color density selection means 40 selects the color density combination of the color density-dot area ratio conversion table stored in the first storage means 10 and the object to be measured stored in the second storage means 30. The combination of color densities closest to that of the object to be measured is selected from among the combinations of color densities in the color density-dot area ratio conversion table.

In this way, the combination of dot area ratios corresponding to the combination of color densities selected from the color density-dot area ratio conversion table as the one closest to the combination of color densities of the object to be measured is displayed by the dot area ratio display means 50. Displayed by. As described above, when expressing the color of an object to be measured (for example, a color sample) by printing with printing ink, it is easily determined at what halftone area ratio each color of ink should be printed.

Figures 2a and b show an example of a color density-dot area ratio conversion table, and the left side shows the combinations of color densities obtained through each of the R filter, G filter, B filter, and amber filter. are shown, and on the right side, combinations of halftone area ratios corresponding to the combinations of color densities shown on the left side are shown.

Such a color density-dot area ratio conversion table is created as follows. First, YM on printing paper
Using each ink of C.Bk, halftone area ratio 0%
to 100% at appropriate intervals, for example at 10% intervals as in the case of FIG. 2, and actually prints to create a color chart. That is, in the example in Figure 2, for numbers 1 to 11, the MYBk version has a halftone area ratio of 0%, and only the C version has a dot area ratio of 0% to 100%, varying in 10% increments, and for numbers 12 to 11, the dot area ratio is 0%. number 22
Until now, the dot area ratio was 0% for the Y.Bk version, 10% for the M version, and the dot area ratio was between 10% and 100% for the C version only.
The dot area ratio of each plate of YMCBk was changed in 10% increments, and color charts were created using various combinations. Such combinations result in 11 ⁴ =14641 combinations when the dot area ratio is varied at 10% intervals for each version of YMCBk.

For each color of the color chart created as described above, a combination of color densities obtained through the R filter, G filter, B filter, or further through an amber filter or ND filter is used. Find the combination with the added color density. 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.

Although color density is generally measured using the RGB amber or ND filters described above, an interference filter or the like having a peak in the absorption portion of the spectral reflection curve of the printing ink may also be used. 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 area ratio conversion table obtained as above, for example, from number 1 to number 11 in Figure 2, the dot area ratio of each version of MYBk remains 0% and does not change. Although only the C version has changed, not only the color density through the R filter, which is the complementary color of C, but also the color density through the other GB amber filters has changed. 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 dot area ratio of a certain object, it is necessary to take into account not only the color density through one filter but also the color density through other filters. The data of the color density-dot area ratio conversion table is stored in the first storage means 10, and such storage means may be a magnetic disk, a floppy disk,
An appropriate device such as ROM is used.

As described above, the color density-dot area ratio conversion table is stored in the first storage means 10 in advance.

The color density measuring means 20 measures the color density of the object to be measured, and FIG. 3 is a block diagram showing one embodiment thereof. In the example shown in FIG. 3, the object 1 to be measured, such as a color sample, is illuminated by a light source 21, and 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 that used when creating the color density-dot area ratio conversion table, and includes an R filter, a G filter,
Three types of B filters or four types of filters, including an amber filter or ND filter, are installed in a convertible manner. In this case, the filter may be switched electrically or manually. In addition, in the example shown in Figure 3, the light from the light source is irradiated from an angle of 45 degrees,
Although the light is received directly above, it is also possible to emit light from directly above and receive the light at a 45° angle. The electrical signal generated by the photoelectric conversion element 23 is amplified by an amplifier 24, subjected to necessary correction by a correction circuit 25, subjected to logarithmic conversion processing by a logarithmic converter 26, and then converted from an analog signal to a digital signal by an A/D converter 27. is converted into a color density, and is input and stored in the second storage means 30 as a color density. Note that the value of the electrical signal subjected to logarithmic conversion processing by the logarithmic converter 26 can be checked on a display meter 28.
The display meter 28 is an A/D converter 27.
It may also be displayed digitally by placing it after the .

As described above, the object to be measured is measured for each filter to obtain a combination of color densities of the object to be measured, and these are stored in the second storage means 30 as described above. As the second storage means 30, an appropriate one such as a RAM can be selected.

The color density selection means 40 selects a combination of color densities of the object to be measured stored in the second storage means 30 and a combination of color densities in the color density-dot area ratio conversion table stored in the first storage means 10. The method is to compare the color density to halftone area ratio conversion table and select the one closest to the color density combination of the object to be measured from among the color density combinations in the color density-dot area ratio conversion table.The selection is performed as follows. It will be done. The color density obtained through each of the R filter, G filter, B filter, and amber filter of the object to be measured is D _R , D _G , D _B ,
D _A , and the color densities via the R filter, G filter, B filter, and amber filter at the nth number of the color density-dot area ratio conversion table are T _R (n) and T _G respectively.
(n), T _B (n), and T _A (n). Next, the combinations of color densities of the object to be measured D _R , D _G , D _B , D _A and the n-th number of color densities in the color density-dot area ratio conversion table T _R (n), T _G (n), T _B (n), T _A
Combinations of color densities T _R (n), T _G (n), T _B (n), T _A (n) that minimizes the distance SA (n) between (n)
seek.

The distance SA (n) is [SA (n)] ² = [T _R (n) - D _R ] ² +
[T _G (n)-D _G ] ² + [T _B (n) + D _B ] ² + [T _A (n)-
D _A ] It is obtained from the relational expression of ² .

The value of n that minimizes the distance SA(n) is [SA(n)]
² matches the minimum value of n. Therefore, using the above relational expression, select the combination of color densities in the color density-dot area ratio conversion table that minimizes [SA(n)] ² by sequentially changing the value of n from n = 1 to the end. By searching, you can find the value of n that minimizes SA(n). The combination of color densities in the color density-dot area ratio conversion table corresponding to n that minimizes SA(n) is determined as the one closest to the combination of color densities of the object to be measured, and Corresponding Y.
The combination of dot area ratios for each version of MCBk is determined.

Even in this case, if [SA(n)] ² becomes zero during the search, the combination of color densities of the object to be measured and the color density -
If a matching color density is found in the halftone area ratio conversion table, the combination of halftone area ratios corresponding to the combination of color densities at the value of n at that time is the data to be sought. You may abort the search.

The combination of dot area ratios of each YMCBk version determined as described above is displayed by the dot area ratio display means 50. As the dot area ratio display means, an appropriate device such as a printer or a CRT display can be used.

The above well-displayed combination of halftone dot area ratios indicates the halftone dot area ratio of each plate, and depending on the combination of halftone dot area ratios obtained in this way, printing using each color ink will result in a It is possible to obtain a printed matter with the same or similar color to the measured 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 C version is 30%, the M version is 0%, Y
The screen is displayed as 10% and the Bk plate as 0% by the halftone area ratio display means. Therefore, by printing using ink of each color in the combinations shown here, it is possible to obtain a printed matter that is the same as or similar to the color of the object to be measured.

Incidentally, the type of paper for the color chart used to create the data of the color density-dot area ratio conversion table may be different from the type of paper used for actual printing. Or, if the solid density value used as the standard when creating the data of the color density-dot area ratio conversion table is different from the solid density value used as the standard at the printing factory when actually printing at that printing factory. In some cases, it may be. In such cases, the conditions for creating the color density-dot area ratio conversion table and the conditions for actual printing are different, so the color density of the color density-dot area ratio conversion table is When comparing the combinations of color densities of the object to be measured, it is necessary to take into account the differences in the conditions mentioned above.

An example of how to take such a difference in conditions into consideration is explained below, but since it would be very complicated to completely compensate for the difference in conditions, in the example below, A case of approximate correction is shown.

Figure 4 is a graph for explaining the relationship between color density and halftone area ratio.For simplicity, we will explain this as a linear relationship, but the same idea can be applied to curves. All you have to do is make a correction.

In Figure 4, when creating the color density-dot area ratio conversion table, the part where only the C plate is 100% and all other plates are 0% is changed to the color obtained through the R filter, which is a complementary color of C. Assume that the density is X _C and that all the plates are 0%, that is, the color density obtained through the R filter on the portion of the color chart paper where no ink is applied is N _C.
Furthermore, solid printing is performed in advance on the paper to be actually printed using a C plate with a density determined as a standard solid density at the printing factory and a plate having a halftone dot area ratio of 100%. The solid density of the C plate printed on the paper to be actually printed is measured by the apparatus of the present invention through the R filter, and the color density is X _C ', and the paper without printing is Assume that the color density obtained by measurement through an R filter using the apparatus described above is N _C '. In FIG. 4, straight lines a and b indicate the relationship between color density and halftone dot area ratio when creating a color density to halftone dot area ratio conversion table and when actually printing. In this case, the color density obtained by passing the object to be measured such as a color sample through an R filter using the apparatus of the present invention is
If D _C ′, then calculating the dot area ratio without making any correction will yield the dot area ratio P′, but the value differs from the dot area ratio P that should actually be calculated. You can get it. Therefore, in order to correct the error in this case, the color density value of the object to be measured is corrected as follows. In other words, the color density obtained by measuring the object to be measured through the R filter
If the color density after correcting the value of D _C ′ is D _C , then the relationship D _C = (D _C ′−N _C ′)×X _C −N _C /X _C ′−N _C ′+N _C The color density of the object to be measured obtained through the R filter is corrected using the formula. In the same way, the color density of the M plate only printed at 100%, the Y plate only printed at 100%, and the Bk plate only printed at 100% is determined through the G filter, B filter, and amber filter, and then Obtain the color density of the paper itself through the G filter, B filter, and amber filter, and use these color density data to obtain the measured object through the G filter, B filter, and amber filter (or ND filter). The corrected color densities are also corrected, and the corrected color density combinations D _C , _DG , D _B , and _DA are compared with the color density combinations in the color density-dot area ratio conversion table. used for That is, when performing correction in this example, first, the color density of the paper to be actually printed is determined using the apparatus of the present invention through R, G, and B filters. Furthermore, the reference solid printing area of each color ink at the printing factory is processed using the apparatus of the present invention, using the R filter for C ink, the G filter for M ink, and the B filter for Y ink.
Filter: For Bk ink, determine the color density measured through an amber filter. These data are recorded in the device of the present invention. Next, the color density of the object to be measured is measured using the apparatus of the present invention through R, G, B, and amber filters. Correction is performed using the density value.

In the example of correction described above, the color density of the paper used for actual printing and the color density of the solid printed area of each color ink were actually measured using the apparatus of the present invention to obtain correction data. If the data has been obtained in advance, the data may be input using a numeric keypad or the like.

Furthermore, as another correction method, as a color density measuring means, the light part and the shadow part are R, G,
If a densitometer that can be adjusted independently for each of the B and amber filters is used, the following procedure may be used. In other words, the light section measures the unprinted part of the paper to be printed,
Color density-dot area ratio conversion table C, M, Y,
Each of Bk is 0% (in case of number 1 in Figure 2)
Adjust the density through R, G, B, and amber filters so that the color density becomes Prepare a print with density, and use R for the solid density part of C ink.
Measure the color density of the shadow area through the filter, and calculate the color density of the R filter when C in the color density-dot area ratio conversion table is 100% (in the case of number 11 in Figure 2). Similarly, M ink, Y ink, and Bk ink are measured through G filter, B filter, and amber filter, and Y, M, and Bk in the color density-dot area ratio conversion table are adjusted. Adjust so that the color density of the G filter, B filter, and amber filter is the same as when each is 100%. After making these adjustments, the actual object to be measured is measured to determine the combination of dot area ratios.

Although various correction methods have been described above, none of them can provide 100% correction.

FIG. 5 is a flowchart showing how combinations of dot area ratios are determined using the apparatus of the present invention, including such corrections.

In Fig. 5, the number of the color temperature-dot area ratio conversion table when the distance is the minimum value is memorized, and the dot area ratio is calculated from this number. This is possible by determining in advance the percentage interval at which the halftone dot area ratio of each plate is to be changed and the order in which they are to be arranged. In this case, the first storage means does not need to store data on halftone area ratios, but only data on color density combinations can be stored in a predetermined order. This is convenient because a storage means with a small storage capacity can be used.

The accuracy of the dot area ratio determined as described above depends on the accuracy with which the dot area ratio is created in the color density-dot area ratio conversion table. In the example shown in FIG. 2, the dot area ratio is changed at 10% intervals, so the accuracy is up to 10%.

Therefore, if a more accurate halftone area ratio is required, it is sufficient to create a color density to halftone area ratio conversion table with the required accuracy.
In this case, the amount of data in the color density-dot area ratio conversion table becomes extremely large, and creating such data not only requires a great deal of time and effort, but also 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 measurement data of the object to be measured.

The second invention of this application is a device that can eliminate such drawbacks and determine halftone area ratios at intervals finer than data intervals of halftone area ratios in a color density-halftone area ratio conversion table. This is what we are trying to provide.

That is, the second invention of this application is a color density-dot area ratio conversion that shows a combination of color densities and a combination of halftone area ratios corresponding to the combination of color densities of a color separation plate of a plurality of colors. a first storage means in which a table is stored; a color density measurement means for determining the combination of color densities of the object to be measured; and a second storage means for storing the combinations of color densities determined by the color density measurement means. a storage means, a combination of color densities of a color density-dot area ratio conversion table stored in the first storage means and a combination of color densities of the object to be measured stored in the second storage means; color density selection means for comparing and selecting the color density combination closest to the color density combination of the object to be measured from among the color density combinations in the color density-dot area ratio conversion table; dot area ratio interpolation means for determining a combination of interpolated dot area ratios based on the color density-dot area ratio conversion table when the combination and the combination of color densities of the object to be measured do not match; If the selected combination of color densities and the combination of color densities of the object to be measured do not match, the interpolated halftone area ratio is displayed, and if they match, it corresponds to the selected combination of color densities. and a halftone dot area ratio display means for displaying a combination of halftone dot area ratios.

FIG. 6 is a conceptual diagram of the apparatus of the second invention of this application, which includes a first storage means 10 in which a color density-dot area ratio conversion table is stored, a color density measurement means 20, and a second storage. means 30, color density selection means 40
is the same as the first invention, and the first invention is the same as the first invention.
Similarly to the apparatus of the invention, the combination of color densities closest to the combination of color densities of the object to be measured is selected from the color density-dot area ratio conversion table.

If the combination of color densities selected in this way is selected as a result of the distance SA=0, that is, if it is selected as a result of completely matching the combination of color densities of the object to be measured, then the corresponding halftone area ratio It is sufficient to display the combinations as they are on the dot area ratio display means 70. However, if the selected combination of color densities is selected in a case other than the SA=0, the dot area ratio corresponding to the selected combination of color densities is determined by the dot area ratio interpolation means 60. Interpolation is performed to obtain a combination of dot area ratios that can print a color that is even closer to the color of the object to be measured.

How to interpolate the dot area ratio will be explained below.

First, from the color density-dot area ratio conversion table with dot area ratios in 10% intervals as shown in Figure 2, the color density combination d (D _R , _DG , D _B , D _A ) of the object to be measured is determined. The closest one is selected and its color density combination is t
(T _R , T _G , T _B , T _A ) and the corresponding combination of halftone area ratios is P (C, m, y, bk). In this case, for example, it is assumed that it is desired to obtain even a dot area ratio of the order of 1%. In this case, the surface dot area ratio to be determined exists within the dot area ratio shifted by half of 10%, that is, 5%, in the direction of magnitude with P as the center. In the following explanation, in order to simplify the explanation, we will use the following combinations of halftone area ratios.
Although the explanation will be limited to the three colors C, M, and Y excluding Bk, the interpolation process can be performed in exactly the same way even when Bk is not excluded.

Figure 7 shows A (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), H(c-5, m-5, y-5)
The dot area ratio to be determined exists in a solid having these points as vertices.

Therefore, divide this solid into parts with the required accuracy as shown in Fig. 7, and calculate the combination of color densities for each combination of halftone area ratios shown by each grid point, and use the above formula to calculate the distance of color densities. The point at which the distance is the minimum may be selected, and the combination of dot area ratios at that point may be determined as a combination of dot area ratios with increased accuracy.

However, the above A, B, C, D, E, F, G, H
The dot area ratio of the point is known as mentioned above,
The corresponding color density is unknown.

Therefore, A'(c+10, m-
10, y+10), B'(c+10, m+10, y+10),
C'(c+10, m+10, y-10), D'(c+10, m-
10, y-10), E'(c-10, m-10, y+10),
F′(c-10, m+10, y+10), G′(c-10, m+
10, y-10), H'(c-10, m-10, y-10) and their respective midpoints I(c, m-10, y+10), J
(c, m+10, y+10), K(c, m+10, y-
10), L(c, m-10, y-10), M(c+10, m,
y+10), N(c+10, m+10, y), O(c+10,
m, y-10), Q(c+10, m-10, y), R(c,
m, y+10), S(c, m+10, y), T(c, m,
y-10), U(c, m-10, y), V(c-10, m,
y+10), W(c-10, m+10, y), X(c-10,
m, y-10), Y(c-10, m-10, y), Z(c+
Since the combination of color densities of 10, m, y) and ZZ (c-10, m, y) can be known from the color density-dot area ratio conversion table, first, the color density of each of these points and point P Using the color density values of A, B,
The combination of color densities of points C, D, E, F, G, and H is determined by interpolation calculation.

FIG. 8 shows the position of each point 10% away from point P in the C, M, Y coordinate system representing the halftone area ratio.

First, a method for finding a combination of color densities at point A (c+5, m-5, y+5) using an interpolation method will be described. Point A is point A'(c+10, m-
u, y+10), M(c+10, m, y+10), Z(c+
10, m, y), Q(c+10, m-10, y), I(c,
m-10, y+10), R(c, m, y+10), P(c,
m, y), U(c, m-10, y). Therefore, points A′, M,
Find the average of each color density component of Z, Q, I, R, P, and U, and calculate that value as the color density component of point A, that is, point A.
A combination of color densities.

Note that if the color density-dot area ratio conversion table is not created using equally spaced dot area ratios,
A solid composed of A′, M, Z, Q, I, R, P, and U may be a rectangular parallelepiped instead of a cube.
In that case, the distance of point A from each vertex of the rectangular parallelepiped will be different, so it may be determined using a proportional calculation formula or an appropriate function depending on the distance from each vertex.

Similarly, other points B, C, D, E, F, G, H
Also calculate the combination of color densities for each of them.

As above, points A, B, C, D, E, F, G
Now that we have found the combination of color densities for all of these points, we can use the color densities of these points to calculate the densities of each grid point that divides the cube at required intervals as shown in Figure 7. The combinations are determined in the same manner as described above using an appropriate method such as proportional allocation. Next, find a grid point that minimizes the distance SA between the color density combination of each grid point obtained in this way and the color density combination d (D _R , D _G , D _B ) of the object to be measured. select. Since the combination of dot area ratios at the grid points selected in this way is already known, the combination of dot area ratios corresponds to the combination of dot area ratios P(c, m, y) of the object to be measured. The interpolated data is input to the dot area ratio display means 70 and displayed.
As the dot area ratio display means, an appropriate device such as a CRT display or a printer is used.

By the way, A, B, C, as shown in FIG.
Determining the combination of color densities at all grid points with the required precision for all regions D, E, F, G, and H requires a large number of grid points, making 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 of color densities d (D _R , D _G , D _B ) of the object to be measured.
is determined based on which point among the combinations is closest to the color density of the vertices A to H.

Once a small solid is determined in this way, the combination of color densities of each lattice point separated by the required precision is determined by interpolation only for this small solid, and then the combination of color densities of each lattice point in this small solid is determined by interpolation. The grid point closest to the combination d (D _R , D _G , D _B ) of analyte concentrations may be selected from among them. In this way, the calculation time can be reduced to about one-eighth.

When the combination of color densities in the color density-dot area ratio conversion table and the combination of color densities of the object to be measured completely match, the dot area ratio display means 70 displays the matched color density combination. Corresponding combinations of dot area ratios are displayed, and if they do not match completely, a combination of dot area ratios interpolated as described above is displayed.

Note that the required halftone area ratio may be input using a numeric keypad or the like.

FIG. 9 is a flowchart showing how combinations of dot area ratios are determined using the apparatus according to the second invention of this application described above.

Since the invention of this application has the above structure, it has the following effects.

First of all, according to the device of the invention of this application:
Even if the colors to be reproduced in printing are specified as actual colors, such as in a color sample, it is extremely easy and quick for even non-experienced users to determine the colors of each color to reproduce the specified colors. The halftone dot area ratio of halftone positive can be determined.

Next, according to the device of the invention of this application, the halftone positive halftone dot area ratio 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.

Furthermore, according to the second invention of this application, in addition to the above-mentioned effects, it is extremely easy to obtain a dot area ratio with the required accuracy.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the apparatus of the first invention, FIGS. 2a and 2b are explanatory diagrams of a color density-dot area ratio conversion table, and FIG. 3 is an explanatory diagram of an embodiment of the color density measuring means. FIG. 4 is a graph for explaining the relationship between color density and halftone dot area ratio, FIG. 5 is a flowchart for determining a combination of halftone dot area ratios using the apparatus of the invention shown in FIG. 1, and FIG. 6 is a graph for explaining the relationship between color density and halftone dot area ratio. is a conceptual diagram of the apparatus of the second invention, FIGS. 7 and 8 are diagrams for explaining the interpolation processing method of the halftone area ratio in the second invention, and FIG. 9 is a conceptual diagram of the apparatus of the second invention.
Flowcharts for determining combinations of halftone dot area ratios using the apparatus of the invention are shown. 1...Object to be measured, 10...First storage means, 2
0...Color density measuring means, 21...Light source, 22...
Filter, 23... Photoelectric conversion element, 24... Amplifier, 25... Correction circuit, 26... Logarithmic converter,
27... A/D converter, 28... Display meter, 30... Second storage means, 40... Color density selection means, 50, 70... Halftone area ratio display means,
60...Dot area ratio interpolation means.

Claims (1)

[Scope of Claims] 1. A color density-dot area conversion table is stored that indicates a correspondence relationship between a combination of color densities and a combination of dot area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors. a first storage means for storing the combination of color densities of the object to be measured; a second storage means for storing the combination of color densities determined by the color density measurement means; The combination of color densities in the color density-dot area ratio conversion table stored in the first storage means is compared with the combination of color densities of the object to be measured stored in the second storage means. color density selection means for selecting the color density combination closest to the color density combination of the object to be measured from among the color density combinations in the color density-dot area ratio conversion table; A dot area ratio determining device comprising a dot area ratio display means for displaying a combination of dot area ratios corresponding to the combination. 2. A first storage unit storing a color density-dot area ratio conversion table showing a correspondence relationship between a combination of color densities and a combination of dot area ratios corresponding to the combinations of color densities of color separation plates of a plurality of colors; a storage means, a color density measurement means for determining the combination of color densities of the object to be measured, a second storage means for storing the combination of color densities determined by the color density measurement means, and the first storage. The combination of color densities in the color density-dot area ratio conversion table stored in the means is compared with the combination of color densities of the object to be measured stored in the second storage means to determine the color density-dot area ratio. color density selection means for selecting a combination of color densities closest to the color density combination of the object to be measured from among the combinations of color densities in the area ratio conversion table; If the combination does not match, the color density -
a dot area ratio interpolation means for determining a combination of interpolated dot area ratios based on a dot area ratio conversion table;
If the selected combination of color densities and the combination of color densities of the object to be measured do not match, the interpolated halftone area ratio is displayed, and if they match, it corresponds to the selected combination of color densities. 1. A dot area ratio determining device comprising: a dot area ratio display means for displaying a combination of dot area ratios.