JP6794802B2 - Printing plate curve making device, method and program - Google Patents

Description

The present invention relates to a plate curve creating apparatus, method and program for obtaining a plate curve in offset printing.

Conventionally, in the fields of publication printing and commercial printing, offset printing presses have been used. Then, a printing plate curve is applied as one of the means for adjusting the color tone in offset printing. The printing plate curve is a one-dimensional look-up table applied to plate making data in a plate making process of making a plate from plate making data which is original data for making a plate for offset printing.

The printing plate curve has a color tone correction function that changes the CMYK value specified in the plate making data. Then, by using the printing plate curve, it is possible to make the dot gain appropriate and suppress fluctuations in the color tone of the printed matter due to the printing machine and printing conditions. Here, the dot gain is the gradation value of the plate making data and the measured value of the gradation of the actually printed printed matter (halftone dot area) in the primary color (color in which only one of CMYK is used). It represents the difference from the rate). According to the standard based on the Japan Color certification system, the dot gain of 50% halftone dots is 14% for C, M, Y, and K. Further, the printing conditions include the model of the printing machine, ink, paper, the number of screen lines at the time of printing, and the like.

By the way, a method of creating a printing plate curve for adjusting a dot gain amount of a primary color has been proposed (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2000-341525

In recent years, the required quality for printed matter has become higher, and the demand for color tone accuracy has also increased. In addition, not only those based on the Japan Color certification system, but also plate making data produced according to various color standards such as JMPA (magazine advertisement standard) color may be submitted, and the required color tone can be realized. It's getting harder.
In particular, it is necessary to consider the reproducibility of the color tones of the secondary color, the tertiary color, and the quaternary color (colors reproduced by superimposing two or more types of CMYK), which are more important in printed matter.

Therefore, an object of the present invention is to provide a printing plate curve creating device, a method, and a program for approximating the color tone of a printed matter produced by offset printing to the color tone of a specific color standard.

The present invention solves the above-mentioned problems by the following solutions.
The first invention is the printing plate curve in which the target data, which is the color tone data after applying the printing plate curve to the print data, which is the color tone data of the printed matter, and the color reference data, which is the color reference color tone data, are close to each other. It is a printing plate curve creation device including a calculation means for calculating the above and a storage control means for storing the printing plate curve calculated by the calculation means in a storage unit.
According to the second invention, in the printing plate curve creating apparatus of the first invention, the color tone data is data in which a CMYK value is represented by a Lab value, and the printing plate curve is parameter data indicating an amount of change with respect to the CMYK value. It is a printing plate curve creating device characterized by being.
A third invention comprises a weighting receiving means for receiving weighted data indicating the importance of color tone in the printing plate curve creating apparatus of the first invention or the second invention, and the calculation means includes the color reference data and the said. The printing plate curve creating apparatus is characterized in that the printing plate curve is calculated by multiplying the difference from the target data by the weighted data received by the weighting receiving means to minimize the evaluation value.
A fourth invention is an interpolation process for color measurement color tone data, which is color tone data generated by measuring the color of the printed matter in any of the printing plate curve creating devices from the first invention to the third invention. The printing plate curve creating apparatus is provided with an interpolation processing means for generating the print data.
A fifth invention is a method of creating a printing plate curve by a printing plate curve creating device, in which a step of receiving print data which is color tone data of a printed matter and a color reference data receiving means of a color are used. The step of receiving the color reference data which is the reference color tone data, and the printing plate whose calculation means approximates the target data which is the color tone data after applying the printing plate curve to the print data and the color reference data. This is a method including a step of calculating a curve and a step of storing the printing plate curve calculated by the calculation means in a storage unit by the storage control means.
The sixth invention is a program for operating a computer as a printing plate curve creating device according to any one of the first invention to the fourth invention.

According to the present invention, it is possible to provide a printing plate curve creating device, a method and a program for approximating the color tone of a printed matter by offset printing to the color tone of a specific color reference.

It is a functional block diagram of the printing plate curve making apparatus which concerns on this embodiment. It is a figure for demonstrating the color reference data which concerns on this embodiment. It is a figure for demonstrating the print data which concerns on this Embodiment. It is a figure which shows the example of the weighting data which concerns on this embodiment. It is a flowchart which shows the printing plate curve creation process in the printing plate curve making apparatus which concerns on this embodiment. It is a figure for demonstrating the content of the calculation process in the printing plate curve making apparatus which concerns on this embodiment. It is a figure which shows the example of the printing plate curve created by the printing plate curve making apparatus which concerns on this embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. It should be noted that this is only an example, and the technical scope of the present invention is not limited to this.
(Embodiment)
<Printing plate curve creation device 1>
FIG. 1 is a functional block diagram of the printing plate curve creating device 1 according to the present embodiment.
FIG. 2 is a diagram for explaining the color reference data 22a according to the present embodiment.
FIG. 3 is a diagram for explaining the print data 23a according to the present embodiment.
FIG. 4 is a diagram showing an example of weighted data 24a according to the present embodiment.

The printing plate curve creating device 1 shown in FIG. 1 is an apparatus that creates a printing plate curve by using print data which is color tone data of a printed matter and color reference data which is color reference color tone data. Specifically, the printing plate curve creating device 1 calculates a printing plate curve in which the printing plate curve applied to the printing data is similar to the color reference data.
In this example, it is assumed that a standard printed matter showing a color standard is received from a customer, and a printing plate curve for producing a printed matter similar to the received standard printed matter by a target printing machine is calculated. Then, by using the calculated printing plate curve when printing on this printing machine, the printed matter output from the printing machine can have a color tone close to that of the reference printed matter.

The printing plate curve creating device 1 can be realized by using, for example, a server. The printing plate curve creating device 1 may also be a personal computer (PC) or the like.
The printing plate curve creating device 1 includes a control unit 10, a storage unit 20, an input unit 27, an output unit 28, and a communication interface unit 29.
The control unit 10 is a central processing unit (CPU) that controls the entire printing plate curve creating device 1. The control unit 10 appropriately reads and executes the operating system (OS) and the application program stored in the storage unit 20 to cooperate with the above-mentioned hardware and execute various functions.

The control unit 10 includes a color standard data receiving unit 11 (color standard data receiving means), a print data receiving unit 12 (print data receiving means), an interpolation processing unit 13 (interpolation processing means), and a weighted data receiving unit 14 (weighted data receiving unit 14). It includes a weighted reception means), a printing plate curve calculation unit 15 (calculation means), and a storage processing unit 16 (memory control means).
The color reference data receiving unit 11 receives the color reference data 22a.
Here, the generation of the color reference data 22a will be described with reference to FIG.
FIG. 2A shows an example of the reference printed matter 30. The reference printed matter 30 is, for example, a color chart received from a customer. As a color chart, for example, there are charts such as IT8 / 4 and ECI2002.
Further, the standard printed matter 30 indicates, for example, a color standard based on the Japan Color certification system, a JMPA (magazine advertisement standard) color, or the like. The color standard may be any of various standards in the industry and the like. Further, the color standard is not a primary color but a secondary color, a tertiary color, and a quaternary color. Here, the primary color means that any one of the CMYK values changes and the rest is 0%.

FIG. 2B shows an example of color reference data 22a created as a result of measuring the color of the reference printed matter 30 with a color measuring device (not shown). The color measuring device measures the color of each color chart of the reference printed matter 30 and obtains a color measuring value such as CIE Lab.
The color reference data 22a is color reference color tone data, and can be represented as, for example, a CMYK-Lab conversion table that converts CMYK values into Lab values.
Here, the CMYK value is the halftone dot area ratio of C (cyan), M (magenta), Y (yellow), and K (black). In the printing machine, CMYK data is used. Since the Lab space is designed to approximate human vision, the Lab value is described as a color visible to the human eye. The colorimetric value by CIE Lab can be expressed as L *, a *, b *. L * represents lightness, and when it is close to 0, it is black, and when it is close to 100, it is white. a * represents green to red, a negative value is green, and a positive value is red. b * represents blue to yellow, a negative value is blue, and a positive value is yellow. For a * and b *, the larger the numerical value, the higher the saturation.

Instead of receiving the standard printed matter 30 from the customer, the color standard data 22a provided as an ICC (International Color Consortium) profile may be directly received.

Returning to FIG. 1, the print data receiving unit 12 receives the print data 23a (colorimetric color tone data).
Here, the generation of the print data 23a will be described with reference to FIG.
FIG. 3A shows an example of the printed matter 31. The printed matter 31 is a color patch printed by a target printing machine (not shown). Here, the color tone of the printed matter 31 differs depending on the printing conditions such as the model of the printing machine, the ink, the paper, and the number of screen lines at the time of printing. Therefore, it is desirable that the printed matter 31 is printed under the same conditions as those for printing the plate making data.
Then, the print reproduction color of each color patch of the printed matter 31 is measured by a color measuring device (not shown) to obtain a color measurement value such as CIE Lab. FIG. 3B shows an example of print data 23a created as a result of measuring the color of the printed matter 31 with a color measuring device. Similar to the color reference data 22a, the print data 23a can also be represented as, for example, a CMYK-Lab conversion table that converts CMYK values into Lab values.

Returning to FIG. 1, the interpolation processing unit 13 performs interpolation processing on the color reference data 22a and the print data 23a.
The interpolation processing unit 13 calculates the Lab value for the CMYK value that is not in the color reference data 22a by the interpolation calculation. Then, the interpolation processing unit 13 includes the calculation result in the color reference data 22a.
Further, the interpolation processing unit 13 calculates a Lab value for a CMYK value that is not in the print data 23a by interpolation calculation. Then, the interpolation processing unit 13 includes the calculation result in the print data 23a.
The interpolation calculation is performed using, for example, linear interpolation.

The weighted data receiving unit 14 receives the weighted data 24a in which the CMYK value is associated with the importance w. FIG. 4 shows an example of weighted data 24a. The weighted data 24a is created, for example, by the operator of the printing plate curve creating device 1 at the request of the customer. The weighted data 24a is for the operator to place importance on matching colors that are likely to receive complaints about color tones from customers. Further, the weighting data 24a may be created by the operator registering the weighting from a weighting registration screen (not shown).
The weighted data 24a makes the importance w of the color, which requires more accuracy, a large value. In the example of the weighted data 24a shown in FIG. 4, the importance w is an integer from 1 to 10. The importance w varies with respect to each printed matter 31, and for example, an automobile maker attaches importance to red color and the like, and a cosmetics maker attaches importance to skin color and the like.

Returning to FIG. 1, the printing plate curve calculation unit 15 calculates a printing plate curve in which the target data after applying the printing plate curve to the printing data 23a and the color reference data 22a are approximate. Here, the printing plate curve is parameter data indicating the amount of change with respect to the CMYK value.
The printing plate curve calculation unit 15 calculates the color difference between the target data and the color reference data 22a. Then, the printing plate curve calculation unit 15 calculates by simulating the printing plate curve that minimizes the evaluation value obtained by multiplying the color difference by the importance w.
The storage processing unit 16 stores the calculated printing plate curve in the printing plate curve storage unit 25.
The details of each process will be described later.

The storage unit 20 is a storage area for a hard disk, a semiconductor memory element, or the like for storing programs, data, and the like necessary for the control unit 10 to execute various processes.
The storage unit 20 includes a program storage unit 21, a color reference data storage unit 22, a print data storage unit 23, a weighted data storage unit 24, and a printing plate curve storage unit 25.
The program storage unit 21 is a storage area for storing various programs. The program storage unit 21 stores the printing plate curve creation program 21a. The printing plate curve creating program 21a is a program for performing various functions executed by the control unit 10 of the printing plate curve creating device 1.

The color reference data storage unit 22 is a storage area for storing the color reference data 22a.
The print data storage unit 23 is a storage area for storing the print data 23a.
The weighted data storage unit 24 is a storage area for storing the weighted data 24a.
The printing plate curve storage unit 25 is a storage area for storing the calculated printing plate curve.
The input unit 27 is, for example, an input device such as a keyboard or a mouse.
The output unit 28 is, for example, a display device such as an LCD (Liquid Crystal Display).
The communication interface unit 29 is an interface for performing communication with, for example, a color measuring device or the like via a communication network such as an Internet line.

<Processing of printing plate curve creation device 1>
Next, the processing of the printing plate curve creating device 1 will be described.
FIG. 5 is a flowchart showing a printing plate curve creating process in the printing plate curve creating device 1 according to the present embodiment.
FIG. 6 is a diagram for explaining the content of calculation processing in the printing plate curve creating device 1 according to the present embodiment.
FIG. 7 is a diagram showing an example of a printing plate curve created by the printing plate curve creating device 1 according to the present embodiment.

In step S (hereinafter referred to as “S”) 10 of FIG. 5, the control unit 10 (color reference data reception unit 11) of the printing plate curve creating device 1 is, for example, a color measurement not shown via the communication interface unit 29. The color reference data 22a is received from the device. Then, the control unit 10 stores the received color reference data 22a in the color reference data storage unit 22.
In S11, the control unit 10 (interpolation processing unit 13) calculates the Lab value for the CMYK value that is not in the color reference data 22a by interpolation calculation. Then, the control unit 10 adds the Lab value with respect to the calculated CMYK value to the color reference data 22a, and updates the color reference data 22a.
In the interpolation process, for example, the halftone dot area ratio of each (C, M, Y, K) of the CMYK values is set from 0% to 100% in units of 10%, and the Lab value for the CMYK value not included in the color reference data 22a is set. , Calculated using linear interpolation. By this interpolation processing, 11 patterns when each of C, M, Y, and K is from 0% to 100% in units of 10% are calculated for each of the four values (CMYK). As a result, the color reference data 22a includes the Lab value with respect to the CMYK value of the 14641 pattern (color) which is 11 to the 4th power in total.

In S12, the control unit 10 (print data receiving unit 12) receives the print data 23a from a color measuring device (not shown) via the communication interface unit 29, as in the process in S10. Then, the control unit 10 stores the received print data 23a in the print data storage unit 23.
In S13, the control unit 10 (interpolation processing unit 13) calculates the Lab value for the CMYK value that is not in the print data 23a by interpolation calculation. Then, the Lab value with respect to the calculated CMYK value is added to the print data 23a to update the print data 23a. The control unit 10 performs the same interpolation processing as in S11, so that the print data 23a includes a Lab value with respect to the CMYK value of the 14641 pattern.

In S14, the control unit 10 (weighted data receiving unit 14) receives the weighted data 24a. The weighted data 24a represents the importance w with respect to the CMYK value to be weighted by, for example, an integer from 1 to 10. The weighted data 24a may be data for all CMYK values, or may have only data for CMYK values to be weighted.

また、算出処理で用いる色基準データ２２ａを、以下のように表す。

そして、刷版カーブを、次のように表すとする。

In S15, the control unit 10 (printing plate curve calculation unit 15) performs the calculation process. The calculation process is a process for creating a printing plate curve for realizing a standard color tone in the target printing machine.
Here, the print data 23a used in the calculation process is represented as follows.

Further, the color reference data 22a used in the calculation process is represented as follows.

Then, it is assumed that the printing plate curve is expressed as follows.

Then, the printing plate curve that minimizes the evaluation function ef can be calculated by the following formula.

The formula for calculating the evaluation function ef is, for example, the color difference (ΔE) between the target data to which the printing plate curve is applied for each value represented by the CMYK value in the print data 23a and the color reference data 22a of each value. It is the weighted average value multiplied by the importance w. The color tone of the printing plate curve that minimizes the evaluation function ef applied to the printing data 23a and the color reference data 22a are similar to each other. Therefore, the printing plate curve that minimizes this evaluation function ef may be calculated. Then, the printing plate curve that minimizes the evaluation function ef may be calculated using, for example, the conjugate gradient method.

The printing plate curve may be calculated by a method other than the above formula.
For example, a plurality of printing plate curves having different values are prepared, and the printing plate curve having the smallest color difference between the target data obtained by applying the printing plate curve to the printing data 23a and the color reference data 22a is adopted. It may be a thing.
FIG. 6 is a diagram for explaining the target data 43 after applying the printing plate curve used in this method. Table 40 shows the CMYK values of the print data 23a before applying the printing plate curve.

The control unit 10 applies one plate curve selected from a plurality of different plate curves prepared in advance to the table 40 (# 1) to obtain the table 41. Table 41 shows the CMYK values of the target data. Then, the control unit 10 obtains the Lab value corresponding to the table 41 by interpolation calculation using the Lab value of the print data 23a (# 2), and obtains the table 42. The target data 43 is the data shown by the table 41 and the table 42.
Next, the control unit 10 minimizes the value obtained by multiplying ΔE, which is the magnitude of the difference (color difference) between the table 42, which is the Lab value of the target data 43, and the Lab value of the color reference data 22a, by the importance w. Adopt a printing plate curve that becomes.

Returning to FIG. 5, in S16, the control unit 10 (storage processing unit 16) stores the printing plate curve 25a calculated by the above processing in the printing plate curve storage unit 25.
FIG. 7 shows an example of the calculated printing plate curve 25a.
FIG. 7A is a printing plate curve 25a in which the halftone dot area ratio of the CMYK value before correction is represented by the horizontal axis and the halftone dot area ratio of the CMYK value after correction is represented by the vertical axis. The CMYK value before correction is a designated value specified by a printing machine or the like. Further, the corrected CMYK value is a value when actually printing with a printing machine or the like. For example, if a 50% halftone dot area ratio is specified by input, the printing machine indicates that printing is performed with a 40% halftone dot area ratio specification by applying this printing plate curve 25a. ..
FIG. 7B shows the printing plate curve 25a shown in FIG. 7A with the CMYK value before correction as the horizontal axis and the correction amount as the vertical axis. The correction amount is a value obtained by subtracting the halftone dot area ratio before correction from the halftone dot area ratio after correction. By doing so, as shown in FIG. 7A, the printing plate curve 25a in which the CMYK values overlap and is difficult to see can be expressed in an easy-to-see manner.
Returning to FIG. 5, after that, the control unit 10 ends this process.

As described above, the printing plate curve creating device 1 of the present embodiment has the following effects.
(1) Using the color reference data 22a and the print data 23a representing the CMYK value as the Lab value, the target data after applying the printing plate curve to the print data 23a and the printing plate curve 25a in which the color reference data 22a is approximate are obtained. Can be calculated. Therefore, by applying this printing plate curve 25a at the time of printing on the target printing machine, the color tone of the printed matter by offset printing can be approximated to the color tone of a specific color standard.
(2) The printing plate curve 25a in which the target data after applying the printing plate curve to the print data 23a and the color reference data 22a are similar to each other is the weighted average value of the color difference which is the difference between the target data and the color reference data 22a. Is calculated as the minimum. Therefore, the printing plate curve 25a can be obtained by numerical calculation by a computer.
(3) By adding weighting, the printing plate curve can be calculated so that the color tones having a high importance w are closer to each other. Therefore, it is possible to calculate a printing plate curve in which the required color is closer.
(4) Since the printing plate curve 25a is calculated so that the difference between the Lab values is minimized, the printing plate curve 25a that emphasizes the human appearance can be adopted.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Moreover, the effects described in the embodiments are merely a list of the most suitable effects arising from the present invention, and the effects according to the present invention are not limited to those described in the embodiments. The above-described embodiment and the modified form described later can be used in combination as appropriate, but detailed description thereof will be omitted.

(Transformed form)
(1) In the present embodiment, the CMYK value is increased from 0% to 10% to 100%, but is not limited thereto. For example, it may be increased by 20% to 100%. However, as the amount of increase is smaller, the printing plate curve can be evaluated more precisely, so that the color difference can be reduced.
(2) In the present embodiment, the method of calculating the printing plate curve that minimizes the evaluation function by using the conjugate gradient method has been described as an example, but the present invention is not limited to this. Other methods may be used. Further, the weighted average value of the color difference was used to calculate the printing plate curve that minimizes the evaluation function, but the calculation is not limited to this.

1 Printing plate curve creation device 10 Control unit 11 Color reference data reception unit 12 Print data reception unit 13 Interpolation processing unit 14 Weighted data reception unit 15 Printing plate curve calculation unit 16 Storage processing unit 20 Storage unit 21a Printing plate curve creation program 22a Color Reference data 23a Print data 24a Weighted data 25a Printing plate data

Claims (6)

A calculation means for calculating the printing plate curve in which the target data, which is the color tone data after applying the printing plate curve to the print data, which is the color tone data of the printed matter, and the color reference data, which is the color reference color tone data, are close to each other. ,
A storage control means for storing the printing plate curve calculated by the calculation means in the storage unit, and
Equipped with a,
The color tone data is data in which the CMYK value is represented by a Lab value.
The printing plate curve is a printing plate curve creating device which is parameter data indicating the amount of change with respect to the CMYK value . An interpolation processing means for generating print data which is the color tone data of the printed matter by performing interpolation processing on the color measurement color tone data which is the color tone data generated by measuring the color of the printed matter.
A calculation means for calculating the printing plate curve in which the target data, which is the color tone data after applying the printing plate curve to the printing data, and the color reference data, which is the color standard color tone data, are close to each other.
A storage control means for storing the printing plate curve calculated by the calculation means in the storage unit, and
A printing plate curve making device equipped with. In the printing plate curve creating apparatus according to claim 1 or 2.
Equipped with a weighting reception means that accepts weighted data indicating the importance of color tone
The calculation means is a printing plate curve creating device that calculates the printing plate curve that minimizes the evaluation value obtained by multiplying the difference between the color reference data and the target data by the weighted data received by the weighted receiving means. .. It is a method of creating a plate curve with a plate curve creation device.
A step in which the print data receiving means receives print data which is color tone data of printed matter,
A step in which the color standard data receiving means receives color standard data, which is color standard color tone data,
A step in which the calculation means calculates the printing plate curve in which the target data, which is the color tone data after applying the printing plate curve to the printing data, and the color reference data are approximate to each other.
A step in which the storage control means stores the printing plate curve calculated by the calculation means in the storage unit,
Only including,
The color tone data is data in which the CMYK value is represented by a Lab value.
The method in which the printing plate curve is parameter data indicating the amount of change with respect to the CMYK value . It is a method of creating a plate curve with a plate curve creation device.
A step in which the print data receiving means receives the color measurement color tone data, which is the color tone data generated by measuring the color of the printed matter,
A step in which the color standard data receiving means receives color standard data, which is color standard color tone data,
A step in which the interpolation processing means performs interpolation processing on the colorimetric data to generate print data.
A step in which the calculation means calculates the printing plate curve in which the target data, which is the color tone data after applying the printing plate curve to the printing data, and the color reference data are approximate to each other.
A step in which the storage control means stores the printing plate curve calculated by the calculation means in the storage unit,
How to include. A program for operating a computer as a printing plate curve creating device according to any one of claims 1 to 3 .

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