JPH0585893B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device for inputting the dot area ratio of a color to a device used for reproducing or displaying the color. Conventionally, in order to create printed matter, image information is imported from a color original, and the halftone area of each version of C (cyan), M (magenta), Y (yellow), and Bk (black) is used for printing based on the image information. There are devices that calculate the ratio and output halftone film for each plate, or create gravure printing plates by engraving printing plates for each plate using mechanical engraving or laser engraving. It is being
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 example of such a device is what is commonly called a layout scanner. Devices such as such layout scanners are used to reproduce colors of image information. When changing or setting the color of a certain part in a device such as the layout scanner, a color to be changed or a 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 for inputting the 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. 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. It is common to make a decision using what is written and input it 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 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 YMCBk 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 the densities of this printed matter are determined through an R filter, a G filter, and a B filter, they will be 1.53, 0.52, and 0.17, respectively, but these values are converted to G.
It is clear that it cannot be used to calculate the halftone area ratio of the MY version. 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 determine the halftone dot area ratio of a printing plate of each color on which the color of the color sample is to be reproduced. By the way, most of the parts expressed by the colors of the color samples attached to the printing layout paper for color specification are plain parts such as backgrounds of people and color bands. In such cases, in most cases, three or fewer of the four YMCBk inks are sufficient to express the color of the color sample for color specification. Therefore, the present invention eliminates various drawbacks as described above, and when expressing a color specified in a color sample with three or less inks of the four YMCBk colors, the netting of each color plate is improved. It is an object of the present invention to provide a device that can easily input information on how to combine point area ratios to a device that is to reproduce or display the color. That is, the first invention of this application provides color information and YMC corresponding to the color information of color separations of multiple colors.
At least one of the four colors of Bk has a halftone dot area ratio of 0%.The first color information-halftone dot area ratio conversion table indicating the correspondence with the combination of halftone area ratios is stored. a color measuring means for measuring the color of the object to be measured to obtain color information; a second storing means for storing the color information obtained by the color measuring means; and the first memory. The color information of the color information-dot area ratio conversion table stored in the means is compared with the color information of the object to be measured stored in the second storage means to generate the color information-dot area ratio conversion table. color information selection means for selecting color information closest to the color information of the object to be measured from among the color information of the color information; and a halftone dot for outputting a combination of halftone area ratios corresponding to the color information selected by the color information selection means. It is an object of the present invention to provide a halftone dot area ratio determination device characterized by comprising an area ratio output means. Further, a second invention of this application provides a device that can output a more detailed combination of halftone dot area ratios using a table similar to the color information-halftone dot area ratio conversion table used in the first invention. This is what we are trying to provide. Note that as the color information, color density, chromaticity, etc. can be used as a standard. In the following, for the sake of simplicity, we will mainly explain the case where color density is used, 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. The color system for color density is R (red), G
(Green) and B (Blue Violet) color systems are well known. The XYZ color system (CIE (1931)) is the color system for chromaticity.
XYZ color system) or L ^* a ^* b ^* color system (CIE1976 (L ^* a ^*
b ^* )−Color Space), etc. are known. In the XYZ color system, the chromaticities x, y, and z are

[C] However, X, Y, and Z are expressed as tristimulus values, and the closeness (similarity) between two colors is the chromaticity difference △
E = [(Y ₁ − Y ₂ ) ² + (x ₁ − x ₂ ) ² + (y ₁ − y ₂ ) ² ] ^1×2
It is expressed as In addition, in the L ^* a ^* b ^* color system, the chromaticities L ^* , a ^* , b ^* are

[C] However, X, Y, and Z are expressed as tristimulus values, and X ₀ , Y ₀ , and Z ₀ are expressed as tristimulus values of the illumination light source, and the closeness of two colors is expressed as the chromaticity difference △E =
[(L ₁ ^* −L ₂ ^* ) ² + (a ₁ ^* −a ₂ ^* ) ² + (b ₁ ^* −b ₂ ^* )] ^1/2
It is expressed as 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. In particular, the L ^* a ^* b ^* system is excellent for quantitatively handling colors that are close to those perceived by humans. The present invention provides an apparatus that can measure the chromaticity, color density, etc. of the object to be measured and easily determine the halftone dot area ratio of each color plate when expressing the color of the object in print. 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 color information and YM corresponding to the color information of a plurality of color separations are stored in the first storage means 10 in advance.
At least one of the four colors of C.Bk has a dot area ratio of 0%.A color information-dot area ratio conversion table indicating the correspondence with a combination of dot area ratios is stored. The color information data obtained by the color measuring means 20 for obtaining the color information data of the object to be measured is temporarily stored in the second storage means 30. As the color information data stored in the second storage means 30, for example, the color density of the object to be measured is stored in the R filter, the G filter, and the G filter.
It is a combination of three types of color densities obtained through each of the filters and the B filter, or chromaticity. Next, the color information selection means 40 selects the color information of the color information-dot area ratio conversion table stored in the first storage means 10 and the color of the object to be measured stored in the second storage means 30. The color information is compared with the color information and the one closest to the color information of the object to be measured is selected from among the color information in the color information-dot area ratio conversion table. In this way, the combination of dot area ratios corresponding to the color information selected from the color information-dot area ratio conversion table as the one closest to the color information of the object to be measured is outputted by the dot area ratio output means 50. be done. As described above, when expressing the color of an object to be measured (for example, a color sample) by printing with printing ink, the halftone area ratio at which each color of ink should be printed is easily determined. Figure 2 a, b, and c are color information-dot area ratio conversion tables when color density is used as color information.
This shows an example, and the R filter and G filter are shown on the left.
The combinations of color densities obtained through the filter and the B filter are shown, and the combinations of dot area ratios corresponding to the combinations of color densities shown on the left are shown on the right. In this combination of dot area ratios, at least one of the four colors of YMCBk includes a dot area ratio of 0%, three colors of YMC, three colors of YMBk, and three colors of YC
The combinations of the three Bk colors and the three MCBk colors change to various values. Such a color density-dot area ratio conversion table is created as follows. First, YM on printing paper
Using a combination of the above three inks of each of the C.Bk inks, dot area ratios from 0% to 100% are set at appropriate intervals, for example as in the case of Fig. 2.
Create a color chart by actually printing with changes in 10% increments. In other words, in the example in Figure 2, numbers 1 to 1331 are combinations of three types of CMY inks, and among them, numbers 1 to 11 have a halftone area ratio of 0% for the MY version, and only the C version. 0%
~100% in 10% increments, and from number 12 to number 22, the halftone area ratio is 0% for the Y version, 10% for the M version, and 10% for the C version only. ~100
% is changed in 10% increments, and hereafter YMC
The halftone area ratio of each version is changed in 10% intervals. Similarly, numbers 1332 to 2541 are a combination of the three MCBk inks, and numbers 2542 to 3641 are Y.
Combination of three types of C.Bk inks, number 3642 ~ number
For up to 4641, the combinations of three types of YMBk inks were varied at intervals of 10% between 0% and 100% dot area ratio. In this way, color charts with various combinations have been created. Such a combination is 11 ⁴ = 14641 when the halftone area ratio is changed at 10% intervals for each version of YMCBk.
However, as in the case of the present invention, Y.
In the case of a combination of three of the four types of MCBk inks, 4641 combinations are sufficient. For each color of the color chart created as described above, the combination of color densities obtained through each of the R filter, G filter, and B filter is determined. Note that Bk ink is in the visible range. Since the reflectance is considered to be almost constant in the wavelength range of 400 to 700 mm, any RGB filter can be used without preparing a special filter to detect changes in Bk ink.
Changes in Bk ink can be captured. Therefore, in the case of a combination of Bk ink and other inks,
For example, in the case of a combination of MCBk, it is considered that a change in concentration through the B filter indicates a change in Bk.
Similarly, when combining YCBk and YMBk, the concentration through G filter and R filter respectively
This shows the change in Bk. 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 each of the RGB 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 plate is changing, 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 filters is changing. This is because the C ink contains not only the C component but also other color components. This relationship is the same for other inks, which 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. Color density -
The data of the dot area ratio conversion table is stored in the first storage means 10, and an appropriate storage means such as a magnetic disk, floppy disk, ROM, etc. can be used as such storage means. As described above, the color information-dot area ratio conversion table is stored in the first storage means 10 in advance. The color measuring means 20 measures the color of the object to be measured to obtain color information, and FIG. 3 is a block diagram showing one embodiment thereof. The example in FIG. 3 shows an example in which color density is used as color information, and the object to be measured 1, such as a color sample, is irradiated by a light source 21, and the reflected light is passed through a filter 2.
2 to the photoelectric conversion element 23, where it is converted into an electrical signal. The filter 22 has a color density of -
This is the same as the one used when creating the dot area ratio conversion table, and three types of filters, R filter, G filter, and B filter, are installed so that they can be converted. In this case, the filter may be switched electrically or manually. Also, in the example shown in Figure 3, the light from the light source is diagonal.
Although it is designed to emit light from 45 degrees and receive light directly above, it is also possible to emit light from directly above and receive light at 45 degrees. 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 color information and is input to and stored in the second storage means 30 as 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. Note that the display meter 28 may be placed after the A/D 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 30 as described above. As the second storage means 30, an appropriate one such as a RAM can be selected. The color information selection means 40 compares the combination of color information of the object to be measured stored in the second storage means 30 and the color information in the color information-dot area ratio conversion table stored in the first storage means 10. Then, from among the color information in the color information-dot area ratio conversion table, the one closest to the color information of the object to be measured is selected.
The selection is made as follows. For example, when color density is used as color information, R of the object to be measured is
Let the color densities obtained through the filter, G filter, and B filter be D _R , D _G , D _B ,
Also, the R filter, G filter at the n-th number of the color information-dot area ratio conversion table as a color density-dot area ratio conversion table,
The color density through the B filter is T _R (n),
Let T _G (n) and T _B (n). Next, the combination of color densities D _R , D _G , D _B of the object to be measured and the combination T _R (n), T _G ( n), T _B (n) distance S _A
Combination of color densities T _R that minimizes (n)
(n), T _G (n), and T _B (n). 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 ] 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. 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 each YMCBk edition determined as described above is outputted by the dot area ratio output means 50. The dot area ratio output means is for inputting the determined dot area ratio to an external device such as a layout scanner, and once the dot area ratio is outputted to a data storage medium such as a floppy disk, magnetic tape, or paper tape. The point area ratio data may be stored and input into an external device, or may be directly input without being stored. Alternatively, the dot area ratio output means is a device that displays the dot area ratio, such as a printer, a liquid crystal display device,
It may also be a CRT display device or the like. The combination of halftone dot area ratios output as described above indicates the halftone dot area ratio of each plate, and depending on the combination of halftone dot area ratios output in this way, printing using ink of each color 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%, and the M version is 0.
%, 10% for the Y version, and 0% for the Bk version by the dot area ratio output means. Therefore, by printing using the ink of each color in the combination output 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 information-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 information - halftone area ratio conversion table is different from the solid density value used as the standard at the printing factory when actually printing. In some cases, it may be. In such a case, the conditions for creating the color information-dot area ratio conversion table and the conditions for actual printing are different, so the color information in the color information-dot area ratio conversion table is When comparing the color information of the object to be measured, it is necessary to take into account the difference in the conditions mentioned above. An example of how to take such a difference in conditions into account 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 information and halftone area ratio, and shows an example where color density is used as color information.For simplicity, it is assumed that these are in a linear relationship. As will be explained, correction can be applied to curves by applying the same concept. 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.
In addition, solid printing is performed in advance on the actual paper to be 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 an R filter
When the color density after correcting the value of D _C ′ is D _C , the relational expression 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. In the same way, the color density of only the M plate printed at 100% and only the Y plate printed at 100% is determined through the G filter and B filter, and the color density of only the Bk plate printed at 100%.
For items printed in %, the color density is determined through one of the RGB filters, and then the color density is determined through the G filter and B filter of the paper itself, and these color density data are used to calculate the color density. The color densities obtained from the measured object through the G filter and B filter are also corrected, and the corrected color density combinations D _C , _DM , and _DY are included in the color density-dot area ratio conversion table. Used for comparison with color density combinations. In other words, when performing correction in this example, first the color density of the paper to be actually printed is determined using the device of the present invention through each RGB filter, and then The standard solid printed area of each color ink is measured using the apparatus of the present invention through an R filter for C ink, a G filter for M ink, a B filter for Y ink, and one of RGB filters for Bk ink. Find the concentration. These data are stored in the device of the present invention. Next, the object to be measured is subjected to R. using the device of the present invention.
The color density measured through each of the GB filters is corrected using the previously determined color density of the paper and the color density value of the reference solid print area. 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 method of correction, when a densitometer is used as the color density measuring means, the light part and the shadow part can be adjusted independently for each RGB filter, the following may be used. In other words, the light section measures the unprinted portion of the paper to be printed, and each of CMYBk in the color density - halftone area ratio conversion table is 0%.
Adjust the density through each RGB filter so that the color density becomes (in the case of number 1 in Figure 2),
Also, the shadow part is the paper CMY to be printed.
Prepare a print with a standard solid density for each Bk color ink, measure the solid density part of the C ink through an R filter, and calculate the color density of the shadow part at this time by calculating the color density - When C in the dot area ratio conversion table is 100% (number in Figure 2)
11)), and similarly measure M ink, Y ink, and Bk ink through G filter and B filter, and create a color density-dot area ratio conversion table. of
Adjust so that the color density of the G filter and B filter is the same as when each of YMBk 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, as an example, how a combination of halftone area ratios is determined using the apparatus of the present invention, including such correction, when color density is used as color information. . In Fig. 5, the number of the color density-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 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. 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 information to halftone area ratio conversion table with the required accuracy.
In this case, the amount of data in the color information-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 eliminates such drawbacks and is capable of determining and outputting halftone area ratios at intervals finer than data intervals of halftone area ratios in a color information-halftone area ratio conversion table. The aim is to provide a device that can. That is, the second invention of this application provides color information and YM corresponding to the color information of color separations of multiple colors.
At least one of the four colors of CBk has a halftone dot area ratio of 0%.The first color information-halftone dot area ratio conversion table showing the correspondence relationship with a combination of halftone dot area ratios is stored. a storage means, a color measurement means for measuring the color of the object to be measured to obtain color information, a second storage means for storing the color information obtained by the color measurement means, and the first storage means; The color information of the stored color information-dot area ratio conversion table is compared with the color information of the object to be measured stored in the second storage means to determine the color of the color information-dot area ratio conversion table. color information selection means for selecting the color information closest to the color information of the object to be measured from among the information; and, if the selected color information and the color information of the object to be measured do not match, the selected color information; a dot area ratio interpolation means for determining a combination of ink types to be interpolated based on the color information and the interpolated dot area ratio combination based on the color information-dot area ratio conversion table; and the selected color. If the information and the color information of the object to be measured do not match, output the interpolated combination of halftone dot area ratios, and if they match, output the combination of halftone dot area ratios corresponding to the selected color information. and dot area ratio output means. 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 information-dot area ratio conversion table is stored, and a color measurement means 2.
0, the second storage means 30 and the color information selection means 40 are similar to those of the first invention, and similarly to the apparatus of the first invention, they select the color information closest to the color information of the object to be measured. Select from the color information-dot area ratio conversion table. The color information selected in this way is the distance SA=
If it is 0, that is, if it is selected as a result that completely matches the color information of the object to be measured, then the corresponding combination of halftone dot area ratios is output as is by the halftone dot area ratio output means 70. good. However, if the selected color information is selected in a case other than the SA=0, the dot area ratio corresponding to the selected color information is interpolated by the dot area ratio interpolation means 60. Then, a combination of halftone area ratios that can print a color that is even closer to the color of the object to be measured is input. The interpolation of the dot area ratio may be performed using an appropriate method. How to interpolate the dot area ratio will be described below based on its implementation. First, from the color density-dot area ratio conversion table with dot area ratios in 10% intervals as shown in Figure 2, select the one closest to the color density combination d (D _R , _DG , D _B ) of the object to be measured. is selected, and the combination of color densities is expressed as t(T _R ,
T _G , T _B ) 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, if the color information-dot area ratio conversion table number of the selected color density combination d (D _R , D _G , D _B ) is between 1 and 1331, then C.
Interpolate with the combination of MY, and if the following numbers are between 1332 and 2541, the combination of Bk, C, M, numbers 2542 and up.
If between number 3641, combination of Bk, C, Y, number
If the number is between 3642 and 4641, interpolation may be performed using a combination of Bk, M, and Y. Therefore, first, a combination of ink types to be interpolated is determined based on the selected combination of color densities. Next, the halftone dot area ratio to be found for the type of ink determined in this way exists within the halftone 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, three colors, C, M, and Y, will be explained as ink combinations, but the interpolation process can be performed in the same manner in other cases as well. 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), and the halftone area ratio to be sought exists in a solid with these points as vertices. . Therefore, divide this solid into parts with the required accuracy as shown in Figure 7, and use the above-mentioned formula to calculate the color density distance for each combination of halftone area ratios shown by each grid point. 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 the 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 determining the combination of color densities at point A (c+5, m-5, y+5) using an interpolation method will be described. Point A is A'(c+10,m-
10, 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, the 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 consisting of points A', M, Z, Q, I, R, P, and U is used. 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 use a proportional calculation formula or an appropriate function depending on the distance from each vertex. All you have to do is ask for it. 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,
Now that we have found the combination of color densities for all of G and H, we can use the color densities of these points to calculate the lattice points of each grid point that divides the cube into required intervals as shown in Figure 7. Combinations of color densities are determined by 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 obtained in this way and the color densities of the object to be measured d (D _R , D _G ,
Select the grid point that minimizes the distance SA between D and _B ). At the grid points selected in this way, the combination of the dot area ratios is already known, so the combination of the dot area ratios is the combination of the dot area ratios P(c, m, y) of the object to be measured. The interpolated data is input to the dot area ratio input means 70. The dot area ratio input means is the same as in the first invention. By the way, points A, B, C, as shown in FIG.
Obtaining 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, making the 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 of the object to be measured d (D _R , D _G , D _B )
is determined based on which point is closest to the combination of color densities of 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 the color densities of the object to be measured may be selected from among them. In this way, the calculation time can be reduced to about one-eighth. Note that when interpolating a color combination that includes Bk, for example, in the case of a combination of Bk.C, M, the change in density through the B filter is considered to be a change in Bk, and the color density - halftone area ratio is calculated as follows: By considering P(c, m, y) as P(c, m, bk), the combination of halftone area ratios for the closest combination of color densities t(T _R , T _G , T _B ) in the conversion table is as follows: C,M,
Interpolation can be performed in the same way as for the Y combination. Similarly, for the combination of Bk, C, and Y,
Considering the change in density through the G filter as the change in Bk and the combination of dot area ratio P(c, bk, y),
In the case of a combination of Bk, M, and Y, interpolation can be performed by considering the change in density through the R filter as a change in Bk, P(bk, m, y). 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 70 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. Note that the required halftone area ratio may be input using a numeric keypad or the like. FIG. 9 is a flowchart showing an example of how the combination of halftone area ratios is determined using the apparatus according to the second invention of this application described above, when color density is used as color information. be. FIG. 10 is an explanatory diagram of another interpolation method.
The G and B axes represent the color densities obtained through the R, G, and B filters, respectively, and the color density combination t(T _R ,
T _G , T _B ) is the origin. Here, if the vector B→td ( _BR , _BG , _BB ) is set, BR = _R - _{T R} , _BG = D _G - T _G , B _B = D _B - T _B. Further, the dot area ratio is shifted by 1 unit (i.e., 10% in the case of FIG. 2) for the combination P (c, m, y) of the dot area ratio corresponding to the color density combination t. combination P ₃ (c±10, m±10, y
±10) and the corresponding color density combination
t ₃ (T _R3 , T _G3 , T _B3 ) can be known from the color density-dot area ratio conversion table. The dot area ratio P ₃ (c±10, m±10, y±10)
Whether to take a positive or negative value is determined depending on whether each component of the vector B → td (B _R , B _G , B _B ) is greater than or equal to zero or less than zero, and if it is greater than or equal to zero, then It is taken as a positive value, and if it is smaller than zero, it is taken as a negative value. In this case, the numbers to be adopted for each of c±10, m±10, and y±10 are determined by the numbers B _R , B _G , and B _B . Here, considering vector B → tt ₃ , vector B → tt ₃
can be expressed as a composition of several vectors. Here, for the sake of simplicity, the following description will be made assuming that each component of the vector B→d is greater than zero, but the same procedure 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 above combination of dot area ratios P (c, m, y) are respectively P ₁ (c+10, m, y),
Let P ₂ (c+10, m+10, y). The combinations of color densities corresponding to the combinations P ₁ and P ₂ of the dot area ratios are t ₁ (T _R1 , T _G1 , T _B1 ) and t ₂ (T R2 , T _R2 , respectively) according to the color density-dot area ratio conversion table.
T _G2 , T _B2 ). Therefore, vector B→tt ₃ is vector B→tt ₁ , B→t ₁ t ₂
B →
By t ₂ t ₃ , it can be expressed as B→tt ₁ +B→t ₁ t ₂ +B→t ₂ t ₃ =B→tt ₃ . Therefore, vector B→td is vector B→tt ₁ , B→t ₁ t ₂
，
αB→tt ₁ +βB→t ₁ t ₂ +γB→t ₂ t ₃ by B _→ t 2 t ₃
=B→td
It can be expressed as Here, each component of the vector B→td (B _R , B _G , B _B ) is known as described above, so from the above relational expression α,
Find β and γ. Therefore, the color density combination d(D _R , D _G ,
The combination of halftone area ratios P( _c ,
The combination of dot area ratios P′(c′,
m', y') are at 10% intervals in the table in Figure 2, so c' = c + α x 10 m' = m + β x 10 y' = y + γ x 10. As described above, the combination of halftone area ratios after interpolation
P′(c′, m′, y′) is determined. Note that there are various methods of expressing the vector B→tt ₃ as a combination of other vectors in addition to the above, and any vector may be used. However, in order to obtain a reasonable interpolated value, the fifth
As shown in the figure, it is preferable to select vectors such that the vector obtained by connecting the combinations of color densities obtained from the color density-dot area ratio conversion table reaches the combination _t3 of color densities. If the vector method is adopted in this way, the processing time required for interpolation to find the combination of highly accurate halftone area ratios can be extremely shortened. Furthermore, the interpolation of the dot area ratio can be performed in the same manner not only for color density but also for chromaticity. As in the case of the first invention, various types of dot area ratio output means can be selected as appropriate, and in addition to layout scanners, display devices such as CRT displays and printers can also be selected. . 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 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 dot area ratio of the 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 possible to extremely easily determine the dot area ratio with the required accuracy. Furthermore, according to the invention of this application, the amount of data to be stored in the first storage means is extremely small, and the time required for comparison, retrieval, and interpolation with the data stored in the second storage means can be significantly reduced. be shortened.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the apparatus of the first invention, FIGS. 2 a, b, and c are explanatory diagrams of a color density-dot area ratio conversion table, and FIG. 3 is an explanation of one embodiment of the color density measuring means. 4 is a graph for explaining the relationship between color density and halftone dot area ratio, and FIG. 5 is a flowchart of an example of determining a combination of halftone dot area ratios using the apparatus of the first invention. FIG. 6 is a conceptual diagram of the apparatus of the second invention; FIGS. 7, 8, and 10 are diagrams for explaining the method of interpolating the halftone dot area ratio in the second invention; FIG. 1 and 2 respectively show flowcharts of an example of determining a combination of halftone dot area ratios using the apparatus of the second invention. 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 output means,
60...Dot area ratio interpolation means.

Claims (1)

[Scope of Claims] 1. Color information and a dot area ratio of at least one of the four colors of YMCBk corresponding to the color information of the color separation plate of multiple colors including a dot area ratio of 0%. a first storage means in which a color information-dot area ratio conversion table indicating a correspondence relationship with a combination is stored; a color measurement means for measuring the color of an object to obtain color information; and the color measurement means. a second storage means for storing the color information obtained by the method, and color information of the color information-dot area ratio conversion table stored in the first storage means and the color information stored in the second storage means. color information selection means for selecting color information closest to the color information of the object from among the color information of the color information-dot area ratio conversion table by comparing the color information of the object to be measured; 1. A dot area ratio determining device comprising: a dot area ratio output means for outputting a combination of dot area ratios corresponding to the color information selected by the information selection means. 2. Find the correspondence relationship between color information and a combination of halftone area ratios in which at least one of the four colors of YMCBk corresponding to the color information of the multi-color color separation version includes a halftone area ratio of 0%. a first storage means in which a color information-dot area ratio conversion table is stored; a color measurement means for measuring the color of an object to obtain color information; and a color information obtained by the color measurement means. A second storage means to store, color information of the color information-dot area ratio conversion table stored in the first storage means, and color of the object to be measured stored in the second storage means. color information selection means for selecting color information closest to the color information of the object from among the color information in the color information-dot area ratio conversion table; If the color information of the measurement object does not match, the combination of ink types to be interpolated is determined based on the selected color information, and then the halftone dot area is interpolated based on the color information-halftone area ratio conversion table. a halftone dot area ratio interpolation means for calculating a combination of dot area ratios; and when the selected color information and the color information of the object to be measured do not match, output a combination of the interpolated halftone dot area ratios; and a dot area ratio output means for outputting a combination of dot area ratios corresponding to the selected color information.