JP2018093269A - Plate curve creation device, method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plate curve creation device, method and program for approximating the hue of a print by offset-printing to the hue of a specific color reference.SOLUTION: A plate curve creation device 1 includes a plate curve calculation unit 15 calculating a plate curve 25a for approximating object data, i.e., the hue data after applying the plate curve 25a to the print data 23a, i.e., the hue data of a print 31, to the color reference data 22a, i.e., the hue data of color reference, and a storage processing unit 16 for storing the plate curve 25a, calculated by the plate curve calculation unit 15, in a plate curve storage unit 25.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, offset printing type printing machines are used in the fields of publication printing and commercial printing. A press plate curve is applied as one of means for adjusting the color tone in offset printing. The printing plate curve is a one-dimensional lookup table applied to plate making data in a plate making process for producing 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 values specified in the plate making data. By using the printing plate curve, it is possible to make the dot gain appropriate and suppress the variation 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 (halftone dot area) of the printed matter actually printed in the primary color (color in which only one of CMYK is used). Rate) and the difference. According to the standard based on the Japan Color certification system, the dot gain at the 50% halftone dot portion is 14% for all of C, M, Y, and K. The printing conditions include the type of printing press, ink, paper, the number of screen lines at the time of printing plate, and the like.

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

JP 2000-341525 A

In recent years, the required quality for printed matter has increased, and the degree of demand for color accuracy has increased. In addition, not only those based on the Japan Color certification system, but 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 tone of secondary colors, tertiary colors, and quaternary colors (colors reproduced by superimposing two or more types of CMYK), which are more important in printed materials.

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

The present invention solves the above problems by the following means.
According to a first aspect of the present invention, there is provided the printing plate curve that approximates target data that is color tone data after applying a printing plate curve to print data that is color tone data of a printed matter, and color reference data that is color reference color tone data. And a storage control means for storing the printing plate curve calculated by the calculation means in a storage unit.
According to a second aspect of the present invention, in the printing plate curve creating apparatus according to the first aspect, the color tone data is data representing CMYK values as Lab values, and the printing plate curve is parameter data indicating a change amount with respect to the CMYK values. This is a printing plate curve creating device characterized by that.
According to a third aspect of the present invention, in the printing plate curve creating apparatus according to the first or second aspect of the present invention, the printing curve creating apparatus further comprises weight receiving means for receiving weight data indicating the importance of color tone, and the calculating means includes the color reference data and the color reference data The printing plate curve creating apparatus is characterized in that the printing plate curve that minimizes an evaluation value obtained by multiplying the difference from the target data by the weighting data received by the weighting receiving unit is calculated.
According to a fourth aspect of the present invention, in the printing plate curve creating apparatus according to any one of the first to third aspects, an interpolation process is performed on the colorimetric color tone data which is color tone data generated by measuring the color of the printed matter. The printing plate curve creating apparatus is characterized by comprising interpolation processing means for generating the print data.
According to a fifth aspect of the present invention, there is provided a method for creating a printing plate curve by a printing plate curve creating apparatus, wherein the printing data receiving unit receives printing data which is color tone data of a printed matter, and the color reference data receiving unit Receiving the color reference data that is reference color data, and the printing plate in which the calculation means approximates the target data that is the color data after applying the printing plate curve to the print data and the color reference data The method includes a step of calculating a curve, and a storage control unit storing the plate curve calculated by the calculation unit in a storage unit.
A sixth invention is a program for causing a computer to function as any one of the printing plate curve creating apparatuses from the first invention to the fourth invention.

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

It is a functional block diagram of a printing plate curve creating apparatus according to the present embodiment. It is a figure for demonstrating the color reference data which concern on this embodiment. It is a figure for demonstrating the printing data which concern on this embodiment. It is a figure which shows the example of the weighting data which concern on this embodiment. It is a flowchart which shows the printing plate curve creation process in the printing plate curve creation apparatus which concerns on this embodiment. It is a figure for demonstrating the calculation processing content in the printing plate curve production apparatus which concerns on this embodiment. It is a figure which shows the example of the printing plate curve produced with the printing plate curve production apparatus which concerns on this embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. This is merely an example, and the technical scope of the present invention is not limited to this.
(Embodiment)
<Pressure curve creation device 1>
FIG. 1 is a functional block diagram of a printing plate curve creating apparatus 1 according to this 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 illustrating an example of the weighting data 24a according to the present embodiment.

A printing plate curve creating apparatus 1 shown in FIG. 1 is a device that creates a printing plate curve using print data that is color tone data of a printed matter and color reference data that is color reference color tone data. Specifically, the printing plate curve creating apparatus 1 calculates a printing plate curve that is obtained by applying the printing plate curve to the print data and approximates the color reference data.
In this example, a description will be given assuming that a reference printed matter having a color reference is received from a customer, and a printing plate curve for producing a printed matter approximate to the received reference printed matter by a target printing machine is calculated. Then, by using the calculated printing plate curve when printing with this printing press, the printed matter output from the printing press can have a color tone similar to the reference printed matter.

The plate curve creating apparatus 1 can be realized using a server, for example. In addition, the printing plate curve creating apparatus 1 may be a personal computer (PC) or the like.
The plate curve creating apparatus 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 apparatus 1. The controller 10 executes various functions in cooperation with the hardware described above by appropriately reading and executing an operating system (OS) and application programs stored in the storage unit 20.

The control unit 10 includes a color reference data receiving unit 11 (color reference data receiving unit), a print data receiving unit 12 (print data receiving unit), an interpolation processing unit 13 (interpolation processing unit), and a weighting data receiving unit 14 ( A weight receiving unit), a printing plate curve calculation unit 15 (calculation unit), and a storage processing unit 16 (storage control unit).
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 material 30. The reference printed material 30 is, for example, a color chart received from a customer. Examples of color charts include IT8 / 4 and ECI2002 charts.
The reference printed material 30 indicates a color standard such as a color based on the Japan Color certification system or a JMPA (magazine advertisement standard) color. The color reference may be any of various standards such as industry. Also, the color reference is not a primary color but a secondary color, a tertiary color, or a quaternary color. Here, the primary color refers to one in which any one of the CMYK values changes and the rest is 0%.

FIG. 2B shows an example of the color reference data 22a created as a result of color measurement of the reference print 30 by a color measurement device (not shown). In the color measurement device, the color of each color chart of the reference printed matter 30 is measured, and a color measurement value such as CIE Lab is obtained.
The color reference data 22a is color reference color tone data, and can be expressed as, for example, a CMYK-Lab conversion table for converting CMYK values into Lab values.
Here, the CMYK values are halftone dot area ratios 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. Colorimetric values according to CIE Lab can be expressed as L *, a *, b *. L * represents lightness, black when close to 0, and white when close to 100. 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. a * and b * indicate that the greater the numerical value, the higher the saturation.

  Instead of receiving the reference print 30 from the customer, the color reference 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 print data 23a (colorimetric color tone data).
Here, generation of the print data 23a will be described with reference to FIG.
FIG. 3A shows an example of the printed material 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 varies depending on printing conditions such as the type of printing press, ink, paper, and the number of screen lines at the time of printing plate. Therefore, the printed matter 31 is preferably printed under the same conditions as the conditions for printing plate making data.
And the color reproduction value of each color patch of the printed matter 31 is measured by a color measurement device (not shown) to obtain a color measurement value such as CIE Lab. FIG. 3B shows an example of the print data 23a created as a result of the color measurement of the printed matter 31 by the color measurement device. Similarly to the color reference data 22a, the print data 23a can also be expressed 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 Lab values for CMYK values not included in the color reference data 22a by 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 not included 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 weighting data receiving unit 14 receives weighting data 24a in which the importance w is associated with the CMYK value. FIG. 4 shows an example of the weighting data 24a. The weighting data 24a is created, for example, by a request from a customer by the operator of the printing plate curve creating apparatus 1. The weighting data 24a is used by the operator to attach importance to colors that are likely to receive complaints about color tone from customers. The weighting data 24a may be created by an operator registering weighting from a weighting registration screen (not shown).
In the weighting data 24a, the importance w of a color that requires more accuracy is set to a large value. In the example of the weighting data 24a illustrated in FIG. 4, the importance w is an integer from 1 to 10. The importance w varies with respect to each printed matter 31. For example, an automobile manufacturer places importance on red and the like, and a cosmetic manufacturer places importance on skin color and the like.

Returning to FIG. 1, the printing plate curve calculation unit 15 calculates a printing plate curve that approximates the target data after applying the printing plate curve to the print data 23a and the color reference data 22a. 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 the printing plate curve by simulating a printing plate curve having a minimum 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.
Details of each process will be described later.

The storage unit 20 is a storage area such as a hard disk or a semiconductor memory element 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 weighting 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 a 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 apparatus 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 print data 23a.
The weighting data storage unit 24 is a storage area for storing weighting 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 an input device such as a keyboard and a mouse, for example.
The output unit 28 is 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 via a communication network such as an Internet line.

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

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

In S12, the control unit 10 (print data receiving unit 12) receives print data 23a from a color measurement 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 23 a in the print data storage unit 23.
In S13, the control unit 10 (interpolation processing unit 13) calculates Lab values for CMYK values not included in the print data 23a by interpolation calculation. Then, the Lab value corresponding to the calculated CMYK value is added to the print data 23a, and the print data 23a is updated. The control unit 10 performs an interpolation process similar to S11, so that the print data 23a includes Lab values for the CMYK values of the 14641 pattern.

  In S14, the control unit 10 (weighting data receiving unit 14) receives the weighting data 24a. The weighting data 24a represents the importance w for the CMYK values to be weighted, for example, as an integer from 1 to 10. The weighting 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 (press plate curve calculation unit 15) performs a calculation process. The calculation process is a process for creating a printing plate curve for realizing a reference color tone in the target printing press.
Here, the print data 23a used in the calculation process is expressed as follows.

In addition, the color reference data 22a used in the calculation process is expressed as follows.

The plate curve is expressed as follows.

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

  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. The weighted average value is multiplied by the importance w. The color plate data 22a and the color reference data 22a are similar to each other in color tone when the printing plate curve that minimizes the evaluation function ef is applied to the print data 23a. Therefore, a printing plate curve that minimizes the evaluation function ef may be calculated. Then, a printing plate curve that minimizes the evaluation function ef may be calculated using, for example, a conjugate gradient method.

Note that the 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 a printing plate curve having the smallest color difference between the target data obtained by applying the printing plate curve to the print 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. The table 40 shows CMYK values of the print data 23a before application of the printing plate curve.

The control unit 10 applies one printing plate curve selected from a plurality of different printing plate curves prepared in advance to the table 40 (# 1) to obtain the table 41. Table 41 shows 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 data indicated by the table 41 and the table 42.
Next, the control unit 10 minimizes the value obtained by multiplying ΔE which is the magnitude (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.

Returning to FIG. 5, in S <b> 16, the control unit 10 (storage processing unit 16) stores the printing plate curve 25 a calculated by the above-described 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 on the horizontal axis and the halftone dot area ratio of the CMYK value after correction is represented on the vertical axis. The CMYK value before correction is a specified value specified by a printing machine or the like. The corrected CMYK value is a value at the time of actual printing with a printing machine or the like. For example, if a halftone dot area ratio of 50% is specified by input, the printing press indicates that printing is performed with a halftone dot area ratio of 40% by applying the 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 dot area ratio before correction from the dot area ratio after correction. By doing so, as shown in FIG. 7A, it is possible to express the plate curve 25a that is difficult to see because the CMYK values overlap each other.
Returning to FIG. 5, the control unit 10 then ends this process.

Thus, according to the printing plate curve creating apparatus 1 of the present embodiment, there are the following effects.
(1) Using the color reference data 22a and the print data 23a that represent CMYK values as Lab values, the target data after applying the plate curve to the print data 23a and the plate curve 25a that approximates the color reference data 22a are obtained. It can be calculated. Therefore, by applying this printing plate curve 25a at the time of printing with 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 reference.
(2) A weighted average value of the color difference, which is a difference between the target data and the color reference data 22a, and the printing plate curve 25a that approximates the target data after applying the printing plate curve to the print data 23a and the color reference data 22a. Is calculated as a minimum. Therefore, the printing plate curve 25a can be obtained by numerical calculation by a computer.
(3) By adding weights, the printing plate curve can be calculated so that a color tone having a high importance w is more approximate. Therefore, it is possible to calculate a plate curve that more closely approximates the required color.
(4) Since the printing plate curve 25a is calculated so as to minimize the difference in Lab values, the printing plate curve 25a that places importance on human appearance can be employed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above. In addition, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments. In addition, although embodiment mentioned above and the deformation | transformation form mentioned later can also be used in combination as appropriate, detailed description is abbreviate | omitted.

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

DESCRIPTION OF SYMBOLS 1 Printing plate curve creation apparatus 10 Control part 11 Color reference data reception part 12 Print data reception part 13 Interpolation processing part 14 Weighting data reception part 15 Printing plate curve calculation part 16 Storage processing part 20 Storage part 21a Printing plate curve creation program 22a Color Standard data 23a Printing data 24a Weighting data 25a Printing plate data

Claims (6)

Calculation means for calculating the printing plate curve that approximates the target data that is the color tone data after applying the printing plate curve to the printing data that is the color tone data of the printed matter, and the color reference data that is the color reference color tone data; ,
Storage control means for storing the printing plate curve calculated by the calculation means in a storage unit;
A plate curve making device. In the printing plate curve creating apparatus according to claim 1,
The color tone data is data representing CMYK values as Lab values,
The printing plate curve is parameter data indicating a change amount with respect to a CMYK value.
A plate curve making device characterized by In the printing plate curve creating apparatus according to claim 1 or 2,
A weight receiving means for receiving weight data indicating the importance of the color tone;
The calculating unit calculates the plate curve that minimizes an evaluation value obtained by multiplying the difference between the color reference data and the target data by the weighting data received by the weighting receiving unit;
A plate curve making device characterized by In the printing plate curve creating apparatus according to any one of claims 1 to 3,
Interpolation processing means for generating the print data by performing an interpolation process on the colorimetric color tone data, which is color tone data generated by measuring the color of the printed matter,
A plate curve making device characterized by A method of creating a printing plate curve with a printing plate curve creating device,
A step in which the print data receiving means receives print data which is color tone data of the printed matter;
A step in which the color reference data receiving means receives color reference data which is color reference tone data;
Calculating means for calculating the plate curve that approximates the target data, which is tone data after applying the plate curve to the print data, and the color reference data;
A storage control unit storing the plate curve calculated by the calculation unit in a storage unit;
Including methods.   The program for functioning a computer as a printing plate curve production apparatus in any one of Claim 1- Claim 4.

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