JP2000246874A - Method and apparatus for correcting color - Google Patents

Abstract

PROBLEM TO BE SOLVED: To upgrade reproducibility in the case of printing by using a special ink by gradation converting a pixel vale of a specific color in a main printer, thereby obtaining the gradation converted pixel value. SOLUTION: An input unit 1 inputs engraving plate data formed by another engraving system to an arithmetic unit 2 through a LAN (local area network). The unit 2 separates the data into color separating process to generate separate color engraving data, and conducts color matching calculations and gradation conversion. The conversion is obtained as gradation conversion functions of respective process colors corresponding to the specific color pixel values of γc(v), γm(v), γy(v) and γk(v), pixel values of the respective colors corresponding to the specific reference pixel values of Cs, Ms, Ys, Ks, and gradation converted pixel values of the respective colors corresponding to the gradation conversion values of the respective colors corresponding to the specific pixel values of C, M, Y and K.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of color proofing which simulates color reproduction by the printing press in a proof output machine. In particular, the present invention provides a color proofing method and apparatus having good color reproducibility when printing is performed using a special color ink.

[0002]

2. Description of the Related Art Process inks are known as yellow (Y),
Red (M; Magenta), Indigo (C; Cyan), Ink (K; Black)
) Is a combination of inks that can reproduce colors by four-color printing.
In many color prints, printing is performed using this process ink, but printing may be performed using a special color ink. For example, a case where a special color occupies a large area in a printed matter, a case where a high printing effect is required, a case where it cannot be expressed only by process ink, and the like. In particular, printing on many flexible packaging materials and carton materials includes both a portion printed with process ink and a portion printed with special color ink.

In general, before a printed product as a product is printed on a printing press (main printing press) (printing on the main press), a proof print is printed on a proof printing press (proof printing). This is because, in the proof print, whether the contents and arrangement of the character patterns are appropriate, whether the color reproducibility is appropriate (color proof), and the like are checked in advance. This proof printing includes, for example, a DDCP for inputting digital data and outputting a color print.
(Direct Digital Color Printer) is used. In conventional color proofing using DDCP, output is performed using data that has been converted by a look-up table (LUT). The look-up table is a look-up table for data conversion for obtaining data in which proper color reproduction can be obtained in DDCP with respect to data when printing is performed using process ink in the printing press.

With respect to the special color ink, a color sample of a special color solid (pixel value 100%) is prepared by a main printing machine (or a proof printer equivalent thereto). Then, a pixel value (vector) of the process color (YMC or YMCK) of the calibration output device corresponding to the colorimetric value of the color sample (for example, the colorimetric value in the L ^* a ^* b ^* color space) is obtained. When the spot color is halftone, a pixel value (vector) obtained by multiplying the pixel value (scalar) is used. Based on the pixel value obtained by adding (adding a vector) the pixel value to the pixel value of the process ink corresponding to the pixel, the proof printing is performed with reference to the above-mentioned lookup table.

[0005]

However, when a special color is represented by a process color by the above-described method, the solid color of the special color is based on the colorimetric value and has good color reproducibility. But,
The halftone of a spot color is derived from a solid color of the spot color by a simple calculation, and the color reproducibility is not always good.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a color proofing method and a color proofing device having good color reproducibility when printing is performed using a special color ink. The purpose is to:

[0007]

The above objects are achieved by the present invention described below. That is, the color proofing method according to claim 1 of the present invention is a color proofing method that simulates color reproduction by the present printing press in a proof output device, and performs gradation conversion on a pixel value of a special color in the printing press. It has a special color gamma correction operation for obtaining a pixel value after gradation conversion. According to the present invention, a gradation-converted pixel value obtained by performing gradation conversion on a pixel value of a special color is obtained. Therefore, when printing is performed using a special color ink, a color proofing method with good color reproducibility can be obtained. Is provided.

According to a second aspect of the present invention, there is provided the color proofing method according to the first aspect, wherein the simulated calculation of the overprinting of each color is performed based on the printing order and transmittance of each color in the printing press. Is performed. According to the present invention, the simulated operation of the printing of each color is performed in the simulated operation process, and in the simulated operation, the printing order and the transparency of each color in the printing press are used as operation parameters. Therefore, when printing is performed using not only process inks but also special color inks, a color proofing method with good color reproducibility is provided, taking into account the order in which process inks and special color inks are overprinted and the transparency of those inks. Is done.

According to a third aspect of the present invention, there is provided the color proofing method according to the first or second aspect, wherein the gradation conversion is performed for each of a plurality of special colors n, where n is a positive integer. , V are pixel values of the special color n, γn (v) is a gradation conversion function of the special color n, and v ′ is a pixel value after gradation conversion, and is performed based on the following Expression 3.

## EQU3 ## According to the present invention, the gradation-converted pixel value v 'is obtained from the pixel value v of the special color n by the gradation conversion function γn (v) of the special color n. Therefore, tone conversion is performed on the pixel value of the spot color itself.

According to a fourth aspect of the present invention, there is provided a color proofing method according to the first or second aspect, wherein the gradation conversion is performed based on a pixel value of each process color corresponding to a pixel value of a spot color. The tone conversion is performed.
According to the present invention, gradation conversion is performed on the pixel value of each process color corresponding to the pixel value of the spot color.

According to a fifth aspect of the present invention, in the color proofing method according to the fourth aspect, the gradation conversion is such that v is a pixel value of a special color, γc (v), γm (v), γy
(V) and γk (v) are the gradation conversion functions of each process color corresponding to the pixel value of the special color, and Cs, Ms, Ys, and Ks are the process colors corresponding to the reference pixel value (for example, 100%) of the special color. The pixel values C, M, Y, and K are defined as the gradation-converted pixel values of each process color corresponding to the pixel value of the special color based on the following Expression 4.

C = Cs × γc (v) M = Ms × γm (v) Y = Ys × γy (v) K = Ks × γk (v) According to the present invention, a reference pixel value of a special color (for example, 100
%), The pixel values Cs, Ms, and Y of the respective process colors
s, Ks and gradation conversion functions γc (v), γm (v), γy (v), γk of each process color corresponding to the pixel value of the spot color
According to (v), the pixel values C, M, and G of the process colors corresponding to the pixel values of the special color from the pixel value v of the special color have been subjected to gradation conversion.
Y and K are obtained.

The color proofing method according to claim 6 of the present invention is the color proofing method according to claim 5, wherein n is a positive integer and a plurality of tone conversion functions γ corresponding to each of the plurality of special colors n.
nc (v), γnm (v), γny (v), γnk
(V). According to the present invention, a plurality of tone conversion functions γnc (v), γnm (v), γn corresponding to a plurality of special colors n as tone conversion functions, respectively.
y (v) and γnk (v) are used.

According to a seventh aspect of the present invention, in the color proofing method according to the fourth to sixth aspects, the pixel value of each process color corresponding to the pixel value of the special color is based on a special color correspondence table. It is something that you get. According to the present invention, the pixel value of each process color corresponding to the pixel value of a special color is obtained based on the special color correspondence table. Also, in the color proofing method according to claim 8 of the present invention, in the color proofing method according to any one of claims 1 to 7, the gradation conversion function for the gradation conversion may be obtained based on a special color correspondence table. It was made.
According to the present invention, a gradation conversion function for gradation conversion can be obtained based on the special color correspondence table.

In a color proofing method according to a ninth aspect of the present invention, in the color proofing method according to the seventh or eighth aspect, the spot color correspondence table is obtained by a process color correspondence table generation step and a spot color correspondence table generation step. In the process of generating a process color correspondence table, the calibration output device outputs color patches whose pixel values of the process color are known, and measures colorimetric values (for example, L ^* a ^* b ^* values) obtained by measuring each color patch. ), A process color correspondence table which is a correspondence table between the pixel values of the process colors and the colorimetric values is generated, and the spot color correspondence table generating step includes the steps of: A patch is printed, and the process color correspondence table is referred to based on the colorimetric values obtained by measuring each of the patches to generate a special color correspondence table that is a correspondence table between the pixel values of the spot color and the pixel values of the process color. It was made.

According to the present invention, in the process of generating the process color correspondence table, the calibration output device outputs the color patches whose pixel values of the process color are known, and the colorimetric values obtained by measuring each of them (for example, L ^*). a ^* b ^* values), a process color correspondence table that is a correspondence table between pixel values of the process colors and colorimetric values is generated. Then, in the spot color correspondence table generation process, a color patch whose pixel value of the spot color is known is printed by the printing press, and the process color correspondence table is referred to based on the colorimetric values obtained by measuring each spot color. A spot color correspondence table, which is a correspondence table between pixel values and pixel values of process colors, is generated. Therefore, the special color correspondence table, which is a correspondence table between the pixel values of the special color and the pixel values of the process color, so that the colorimetric value of the special color by the printing press matches the colorimetric value of the special color by the proof output device using the process color. A table is generated.

According to a tenth aspect of the present invention, in the color proofing method according to the ninth aspect, the process color correspondence table and / or the spot color pixel value, the colorimetric value and the spot color pixel value are related. Alternatively, an interpolation method is applied to a value that does not exist in the special color correspondence table. According to the present invention, the process color correspondence table and / or the spot color correspondence table can be referred to in a value that does not exist due to the application of the interpolation method.

In the color proofing method according to the eleventh aspect of the present invention, in the color proofing method according to any one of the first to tenth aspects, the tone conversion function for the tone conversion is such that the spot color is solid (pixel). The interpolation method is applied based on the value of the gradation conversion function when the value is 100%) and the value of the gradation conversion function when the spot color is middle (pixel value: about 50%).
According to the present invention, an interpolation method is applied to the gradation conversion function based on a value when the spot color is solid and a value when the spot color is middle. Therefore, a tone conversion function can be obtained only by two values of solid and middle, so that simple and good color reproducibility can be obtained.

According to a twelfth aspect of the present invention, in the color proofing method according to the eleventh aspect, the tone conversion function for the tone conversion further includes a special color having a shadow (pixel value of about 90%). ), The interpolation method is applied based on the value of the gradation conversion function. According to the present invention, it is possible to obtain a gradation conversion function including the value of the shadow, thereby simplifying the function and obtaining particularly excellent color reproducibility even in the shadow. The color proofing method according to claim 13 of the present invention is the color proofing method according to claim 11 or 12,
The gradation conversion function for gradation conversion is such that an interpolation method is applied based on the value of the gradation conversion function when the spot color is a highlight (pixel value: about 10%). According to the present invention, it is possible to obtain a gradation conversion function including the value of highlight, which is simple, and also particularly excellent color reproducibility can be obtained in highlight.

A color proofing apparatus according to a fourteenth aspect of the present invention is a color proofing method for simulating a color reproduction by the printing press in a proof output device, wherein a tone conversion for a pixel value of a special color in the printing press is performed. A special color gamma correction operation means for obtaining a pixel value after gradation conversion is performed. According to the present invention, a gradation-converted pixel value obtained by performing gradation conversion on a pixel value of a special color can be obtained. Therefore, when printing is performed using a special color ink, a color proofing device having good color reproducibility is obtained. Is provided.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The color proofing method and apparatus of the present invention will be described below with reference to embodiments. FIG. 1 shows the configuration of the color proofing device of the present invention. In FIG. 1, 1 is an input device such as a keyboard and a mouse, 2 is a computing device which is a main body of a computer or the like, 3 is a display device such as a CRT color display, 4 is a storage device such as a hard disk device, 5
Denotes a color print output device (DDCP). As is apparent from this configuration, the color proofing device of the present invention is a computer system having a color print output device 5 for color proofing output. Although not shown in FIG.
N (local area network), it is possible to input plate making data created by another plate making system via a LAN.

The arithmetic unit 2 performs color separation processing of the input plate making data to generate color separation data, and performs color matching calculation and gradation conversion on the color separation data. Then, the separation data is synthesized, and calibration data to be output to the output device 5 is generated. Further, those data are stored in the storage device 4. On the other hand, the output device 5 inputs the calibration data and outputs a color print. The arithmetic unit 2
Displays a screen relating to various settings and various designations to be input by the operator from the input device 1 through the input device 1 on the display device 3 and displays a GUI (grafical use) for the operator.
r interface) to provide the operation environment.

FIG. 2 shows the overall process of data processing in the color proofing device of the present invention. In FIG. 2, the plate making data to be subjected to the calibration output has already been input. First, in step S1 of FIG. 2, plate making data to be combined is selected. Next, in step S2, input of synthesis information is performed. The input items in step S2 will be described. (Item 1) The plate making data of one work item is composed of a set of data. These include CT (continuous tone) data which is continuous tone data such as photographs, and LW which is line drawing data such as logos, illustrations and patterns.
(Line work) data is included. The data to be subjected to the calibration output is selected from the plurality of data.

(Item 2) The printing color of the printing plate to be used is selected. At this time, a printing plate that is not used is also input. The printing color is C, M, Y, K, white, another registered color, a new color that is not registered, or not used. Further, the printing order is input. (Item 3) As a characteristic of the ink of the printing plate to be used, “opaque” is designated for the characteristic of hiding, and “transparent” is designated for the characteristic of transmitting. (Item 4) A characteristic curve of gradation conversion, that is, a curve (monochromatic curve, black plate curve, special color curve) used in gamma correction calculation and a table referred to in color matching calculation are designated or input. (Item 5) A cutoff value which is an upper limit value for forcibly setting a value of a light portion (3% or less) which is difficult to be reproduced by the printing machine to 0% is input.

Next, in step S3, a separation process is performed based on the "combination" of the combination information and the "printing plate to be used". By the separation processing, data (separation data) of each printing plate is obtained. Next, in step S4, adjustment (gradation conversion) is performed on the generated separation data using a single color curve created by the user. Next, in step S5, color matching calculation is performed for the CMY plate, adjustment is performed using the black plate curve for the K plate, and adjustment is performed using the special color curve for the special color plate.

The adjustment using the special color curve of the special color plate in step S5 is one of the gradation conversions performed by the special color gamma correction calculation process (or special color gamma correction calculation means) in the present invention. The gradation conversion performed here is
For each of the plurality of special colors n, where n is a positive integer, v is the pixel value of the special color n, γn (v) is the gradation conversion function of the special color n,
This is performed based on Equation 5 below, where v ′ is a pixel value after gradation conversion.

[Mathematical formula-see original document] v '= [gamma] n (v) [mathematical formula-see original document] As shown in equation 5, the tone conversion functions [gamma] 1 (v), [gamma] 2 (v), [gamma]
3 (v),...

Next, in step S6, the converted separated data is combined. The processing items in step S6 will be described. (Item 1) For the special color plate, CMYK conversion is performed and the special color data (scalar) is converted to CMYK.
Expressed by data (vector). (Item 2) For each pixel based on the ink characteristics and printing order of the synthetic information,
Conversion to pixel values to be output to the proof press. That is,
Multiply pixel values by transparency, add / integrate process colors,
Calculations such as updating of the transmittance are performed (details will be described later).

In step S6, the special color plate is subjected to CMYK conversion, and the special color data (scalar)
Expressed by MYK data (vector) (item 1). The CMYK conversion is a process of obtaining a pixel value (C, M, Y, K) of the process color for the pixel value v of the special color plate. This CMYK conversion is one of the gradation conversions performed by the special color gamma correction calculation process (or special color gamma correction calculation means) in the present invention. That is, this gradation conversion is performed as gradation conversion of the pixel value of each process color corresponding to the pixel value of the special color.

In the gradation conversion performed here, v is a pixel value of a special color, γc (v), γm (v), γy (v), γk
(V) is the gradation conversion function of each process color corresponding to the pixel value of the special color, Cs, Ms, Ys, and Ks are the pixel values of each process color corresponding to the reference pixel value (for example, 100%) of the special color; , M, Y, and K as gradation-converted pixel values of each process color corresponding to the pixel value of the special color, based on Equation 6 below.

C = Cs × γc (v) M = Ms × γm (v) Y = Ys × γy (v) K = Ks × γk (v)

In Equation 6, when a plurality of spot colors are used, a plurality of tone conversion functions γnc (v), γnm (v), and γ corresponding to each of the plurality of spot colors n, where n is a positive integer.
ny (v) and γnk (v) are used. In that case,
Naturally, the reference pixel value of the special color n (for example, 100
The pixel value of each process color corresponding to (%) also differs depending on each spot color, and can be expressed as Cns, Mns, Yns, Kns.

Next, a method for obtaining the pixel values Cs, Ms, Ys, Ks of each process color corresponding to the reference pixel value (for example, 100%) of the special color in Equation 6 will be described.
First, a reference pixel value is set to 100%, and a solid color (pixel value is 100%) of a special color is printed by the printing press. A colorimetric value in the solid L ^* a ^* b ^* color space of this special color (may be another color space) is obtained. On the other hand, the proofreading device outputs a color patch whose pixel value of the process color is known and, based on the colorimetric value in the L ^* a ^* b ^* color space obtained by measuring each, the pixel value of the process color and A process color correspondence table that is a correspondence table with colorimetric values is generated in advance. With reference to the process color correspondence table, the pixel values of the process color that match the solid colorimetric value of the special color are obtained, thereby obtaining the pixel values Cs, Ms, Ys, and K.
s can be obtained.

By such a method, not only the pixel values Cs, Ms, Ys, and Ks of each process color corresponding to the solid color of the special color, but also the pixel values of each process color corresponding to any pixel value of the special color are obtained. Can be. That is, first, a color patch whose pixel value of a special color is known is printed by the printing press. A colorimetric value in the L ^* a ^* b ^* color space obtained by measuring each is obtained. The above-described process color correspondence table is referred to based on the colorimetric values. Then, a special color correspondence table which is a correspondence table between the pixel values of the spot color and the pixel values of the process color is generated. The pixel value of each process color corresponding to the pixel value of the spot color can be obtained based on the spot color correspondence table.

The fact that the pixel value of each process color corresponding to the pixel value of the spot color can be obtained in this way means that the tone conversion function for tone conversion as shown in Expression 6 has been obtained. That is, the gradation conversion function can be embodied based on the spot color correspondence table. For example, the gradation conversion function can be embodied as an interpolation formula by a well-known interpolation method, based on an arbitrary number of sets of pixel values of the spot color and pixel values of the corresponding process colors.

With respect to the pixel values of the process colors, the colorimetric values, and the pixel values of the special colors, an interpolation method is applied to the values that do not exist in the process color correspondence table and / or the special color correspondence table. By applying the interpolation method, it is possible to refer to the process color correspondence table and / or the spot color correspondence table for values that do not exist. The present invention is not limited by the type of the interpolation method. For example, Lagrange interpolation, Hermit interpolation, spline
e) Interpolation methods such as interpolation can be applied.

FIGS. 7 to 10 show examples of the gradation conversion function to which the interpolation method is applied. 7 to 10, the horizontal axis is the pixel value (0 to 100%) of the special color, and the vertical axis is the gradation conversion function γ.
The value of (v), that is, the pixel value after gradation conversion (0 to 100)
%). FIG. 7 shows the value of the gradation conversion function when the spot color is solid (pixel value 100%) and the spot color when the spot color is middle (pixel value about 50%).
%), An example in which an interpolation method is applied based on the value of the gradation conversion function at the time of (%) to obtain a gradation conversion function. in this case,
A tone conversion function can be obtained with only two values of solid and middle, so that simple and good color reproducibility can be obtained.

FIG. 8 shows the values of the gradation conversion function when the spot color is solid (pixel value 100%) and the spot color when the spot color is middle (pixel value about 50%).
%), And an interpolation method is applied based on the value of the tone conversion function when the spot color is a shadow (pixel value: about 90%) and the tone conversion function is obtained. An example is shown. In this case, a gradation conversion function including the value of the shadow is obtained, so that the simplicity and particularly the excellent color reproducibility of the shadow can be obtained.

FIG. 9 shows the value of the tone conversion function when the spot color is solid (pixel value 100%) and the spot color when the spot color is middle (pixel value about 50%).
%) And the interpolation method is applied based on the value of the tone conversion function when the spot color is a highlight (pixel value about 10%) and the tone conversion function is obtained. Here is an example. In this case, a gradation conversion function including the value of the highlight is obtained, so that simple and particularly good color reproducibility can be obtained in the entire gradation.

FIG. 10 shows the value of the tone conversion function when the spot color is solid (pixel value 100%), the value of the tone conversion function when the spot color is shadow (pixel value about 90%), and the spot color is middle. The interpolation method is applied based on the value of the gradation conversion function when the pixel value is about 50% and the value of the gradation conversion function when the spot color is highlight (pixel value about 10%). An example of obtaining a tone conversion function is shown. In this case, a gradation conversion function including shadow, middle, and highlight values is obtained, and simple and particularly excellent color reproducibility is obtained for highlights.

Next, a data conversion process in the color proofing method and apparatus of the present invention will be described. FIG. 3 shows a data conversion process in the color proofing method and apparatus of the present invention. In FIG. 3, reference numeral 31 denotes synthetic information, 32a denotes continuous tone data of a process color, 32b denotes line drawing data of a process color,
32c is spot color continuous tone data, 32d is spot color line drawing data, 33a is process color data separation processing, 33b is spot color continuous tone data 32c separation processing, 33c is spot color line drawing data 32d separation processing, 34a is C version data, 34
b is M plane data, 34c is Y plane data, 34d is K plane data, 34e is gold plane data, 34f is special one plane data, 34g is white plane data, 34h is special two plane data,
34i is special three-color plate data, 35a, 35b, 35c, 3
5d, 35e, 35f, 35g, 35h, and 35i represent a single color curve adjustment (gradation conversion) process for each color plane data;
a is adjusted C-plate data, 36b is adjusted M-plate data, 36c is adjusted Y-plate data, 36d is adjusted K-plate data, 36e is adjusted gold-plate data, 3
6f is the adjusted special color data, 36g is the adjusted white color data, 36h is the adjusted special two color data, 3
6i is the adjusted special three-color plate data, 37 is a color matching calculation process, 37d is a K plate (black plate) curve adjustment (gradation conversion) process, 37e, 37f, 37g, 37h, 37i.
Indicates special color curve adjustment (gradation conversion) processing, 38a, 3
Reference numerals 8b and 38c denote C, M, and Y plane data generated by the color matching calculation processing, 38d, 38e, 38f,
38g, 38h, and 38i are K-plates that have been subjected to gradation conversion,
Color plate data of special one color, white, special two colors, special three colors, 3
Reference numeral 9 denotes a combination process, and reference numeral 40 denotes print data to be output to the output device 5 that performs proof printing.

The composite information 31 is the composite information input in step S2 of FIG. As shown by the arrow coming out of the composite information 31 in FIG.
a, 33b, 33c, monochromatic curve adjustments 35a, 35b,
35c, 35d, 35e, 35f, 35g, 35h, 3
5i, color matching 37, K-plate curve adjustment 37d,
Special color curve adjustment 37e, 37f, 37g, 37h, 37
i, used in the synthesis processing 39.

From the continuous tone data 32a of the process color and the line drawing data 32b of the process color, C
Plate data 34a, M plate data 34b, Y plate data 34c
And K-version data 34d are generated. In addition, the color separation processing 33b converts the special color continuous tone data 32c into the golden color data 34e, the special one color data 34f, and the white color data 3c.
4 g are produced. Further, the special two-color plane data 34h and the special three-color plane data 34i are generated from the line drawing data 32d of the special color. These processes simulate the process of generating original data in plate making. These generated data 34a, 34b, 34c, 34d, 34e, 34f, 3
4g, 34h, 34i correspond to original data for creating a printing plate. That is, a gravure engraving plate corresponds to data input to the gravure engraving machine or a reflection original read by the gravure engraving machine. In addition, a gravure erosion plate corresponds to an original film that is exposed in close contact with a resist. Further, in the case of an offset printing plate, it corresponds to an original plate film that is brought into close contact with a PS plate.

Next, the generated data 34a, 3a
4b, 34c, 34d, 34e, 34f, 34g, 34
h, 34i, the single color curve adjustment 35a, 3
5b, 35c, 35d, 35e, 35f, 35g, 35
h, 35i are performed. Thus, the adjusted C-plate data 36a, M-plate data 36b, Y-plate data 36c, K
Plate data 36d, golden plate data 36e, special one-color plate data 36f, white plate data 36g, special two-color plate data 36h, and special three-color plate data 36i are generated. These monochromatic curve adjustments 35a, 35b, 35c, 35d, 35e,
35f, 35g, 35h and 35i simulate a process of obtaining a printing plate from original plate data in plate making. Therefore, these generated data 36a, 36b, 3
6c, 36d, 36e, 36f, 36g, 36h, 36
i is data corresponding to the plate.

Next, a color matching calculation process 37 is performed from the adjusted C-plate data 36a, M-plate data 36b and Y-plate data 36c to obtain C-plate data 38.
a, M-version data 38b and Y-version data 38c are generated. Further, the adjusted K-version data 36d is further
By performing the plate curve adjustment 37d, the K plate data 38
d is generated. In addition, the gold color plate data 36e, the special one color plate data 36f, the white color plate data 36g, and the special two color plate data 3
The golden color data 38e, the special one color data 38f, the white color data 38g, and the special two color data 38h are obtained by performing special color curve adjustments 37e, 37f, 37g, 37h, and 37i on the 6h and the special three color plane data 36i. And the special three color plane data 38i is generated. These generated data 38a, 38b, 38c, 38d, 38e, 38f, 3
By performing the synthesizing process 39 (to be described in detail later) on 8g, 38h, and 38i, print data 40 to be output to the output device 5 that performs proof printing is obtained. The process of obtaining the print data 40 and the output process of the output device 5 simulate the printing process of the printing press.

FIG. 4 shows the basic concept regarding the synthesis process in the color proofing method and apparatus of the present invention. As shown in FIG. 4, the input data in the synthesizing process is image data of each plate arranged in the printing order. Here, the meaning of the printing order means the printing order when printing is performed on the soft packaging material. In a flexible packaging material, printing is performed on one side of a transparent film, and the printed matter is viewed from the side opposite to the printed side. That is, the printing order here refers to the order of the printing layers that are overprinted from the side where the printed matter is viewed. When printing on printing paper or the like, the printed matter is viewed from the side of the printing surface, and the printing order here is the reverse of the actual printing order. The combining process is performed on the target pixels of the image data in the printing order, and the combining process is sequentially performed on all the pixels by changing the target pixels. The output data of the synthesizing process is image data to be output to DDCP.

FIGS. 5 and 6 show details of the synthesizing process in the color calibration 4 method and apparatus of the present invention. In FIG. 5 and FIG. 6, the pixel value component has a value of 0 to 255, for example, when represented by 8 bits.
It shall have a value of 100%. FIGS. 5 and 6 show a process of synthesizing one target pixel v (i, j). Needless to say, the synthesis processing for all pixels can be performed in the same manner as for the target pixel (i, j).
First, in step S101, variables are initialized.
That is, for the process color variables Cp, Mp, Yp, and Kp, Cp = Mp = Yp = Kp = 0%, and the special color variable Cp
Cc = Mc = Yc = Kc for c, Mc, Yc, Kc
= 0%, and the transmittance t is set to t = 100%.

Next, in step S102, the pixel value Vn is multiplied by the transmittance t. That is, V '= Vn * t. Next, in step S103, it is determined whether the pixel value Vn is a pixel value of a process color plate. If no (NO), the process proceeds to step S104, where special color γ correction is performed. That is, V ″ = γs (V ′) is calculated using γs () as a gradation conversion function for the special color S. Next, in step S105, the special color is converted into a process color, that is, Sc (), Sm ( ), Sy (), S
k () as a function to convert a spot color to a process color, C '
= Sc (V "), M '= Sm (V"), Y' = Sy
(V "), K '= Sk (V"). Next, in step S106, the spot color variables Cc, Mc, Yc, K
Multiply by c. That is, Cc = Cc + C ′, Mc = M
c + M ′, Yc = Yc + Y ′, Kc = Kc + K ′ are calculated, and the spot color variables Cc, Mc, Yc, Kc are updated.

On the other hand, if it is determined in step S103 that the pixel value Vn is the pixel value of the process color plate (YES), it is determined in step S107 whether or not the pixel value is the K plate. If not (NO), in step S109, the process variables Cp, Mp, Yp, K
Multiply by p. If it is determined in step S107 that the image is the K-version (YES), the process proceeds to step S1.
In step 08, after performing K color γ correction,
At 09, the process variables Cp, Mp, Yp, and Kp are integrated. That is, assuming that γk () is a gradation conversion function for the process color K, Cp = Cp + V ′ for the C plane, Mp = Mp + V ′ for the M plane, Yp = Yp + V ′ for the Y plane,
In the case of the K version, Kp = Kp + γk (V ′) is calculated, and the process variables Cp, Mp, Yp, and Kp are updated.

Next, in step S110, the pixel value Vn is set to the value of "opaque", which is a characteristic that the ink has a hiding property.
Is determined. If not (NO), the process proceeds to step S112. If it is determined in step S110 that the pixel value Vn is a pixel value of “opaque”, which is a characteristic of the ink having concealing properties (YES), an operation for reducing the transmittance is performed in step S111. Proceed to S112. That is, t = t−
V 'is calculated. Next, in step S112, a magnitude comparison between the transmittance t and the threshold T is performed. That is, it is determined whether or not the transmittance t <T. If not (NO), the process proceeds to step S113, and it is determined whether or not it is the last plate of the overprint. If no (NO), the process returns to step S102, and the pixel value Vn is set to the pixel value of the next printing order.
Is performed, and the above-described step S102 and subsequent steps are repeated. Also, in step S112,
If it is determined that the transmittance t <T (YES),
Proceed to step 114. The threshold value T is, for example, 10
%.

Next, in step S114, a color matching operation is performed on the process color variables Cp, Mp, Yp using a three-dimensional table or function. That is, using Fc (), Fm (), and Fy () as three-dimensional color matching functions, Cp ′ = Fc (Cp, Mp, Y
p), Mp '= Fm (Cp, Mp, Yp), Yp' = F
Calculate y (Cp, Mp, Yp). Then, Cp ', Mp', Yp 'are substituted for the process color variables Cp, Mp, Yp. That is, Cp = Cp ′, Mp = Mp ′, Yp
= Yp ′. Next, in step S115, the process color variables Cp, Mp, Yp, Kp and the spot color variables Cc,
Mc, Yc, and Kc are added. That is, C = Cp + C
Calculate c, M = Mp + Mc, Y = Yp + Yc. Image data to be output to the calibration output device (DDCP) is obtained from a set of pixel values (C, M, Y, K) obtained in this manner.

[0049]

[Embodiment 1] Next, the above-described synthesizing process will be described based on an embodiment (part 1). Kin (impermeable), K (impermeable), C (impermeable), special red (impermeable), M (impermeable), Y
It is assumed that six printing plates using (transparent) ink are overprinted in this printing order and printing is performed. A pixel to be subjected to the synthesis processing is selected. The pixel value expressed in percent (%) is as follows: Kin (non-transparent) v1 = 100% K (transmitted) v2 = 0% C (transmitted) v3 = 50% Special red (non-transparent) v4 = 0% M (transmitted) ) Let v5 = 100% Y (transmission) v6 = 30%.

The combining process is performed on the above-mentioned pixels. First, variable initialization is performed. Variable initialization: Cp, Mp, Yp, Kp = 0% Cc, Mc, Yc, Kc = 0% t = 100%

The processing of the kin (impermeable) in the first printing order is performed. Multiply pixel value by transmittance: v '= v1 * t = 100% Perform special color gamma correction: v "= γkin (v') = 95% Perform process conversion: C '= Sckin (v") = 15% M '= Sm kin (v ") = 8% Y' = Sy kin (v") = 87% K '= Sk kin (v ") = 5%

Performing process color integration: Cc = Cc + C ′ = 15% Mc = Mc + M ′ = 8% Yc = Yc + Y ′ = 87% Kc = Kc + K ′ = 5% Subtraction of transmittance Perform: t = t−v ′ = 0% Transmission is less than threshold 10% (t <T = 10
%). Therefore, it breaks out of the loop.

Perform a color matching operation: Cp '= Fc (Cp, Mp, Yp) = 0% Mp' = Fm (Cp, Mp, Yp) = 0% Yp '= Fy (Cp, Mp, Yp) = 0 %

Add process color and spot color (process color addition): C = Cp '+ Cc = 15% M = Mp' + Mc = 8% Y = Yp '+ Yc = 87% K = Kp + Kc = 5%

Therefore, C = 15% M = 8% Y = 87% K = 5% is obtained as a pixel value to be output to DDCP.

[0056]

[Embodiment 2] Next, the combining process will be described based on another embodiment (part 2). Kin (impermeable), K (impermeable), C (impermeable), special red (impermeable), M (impermeable), Y
It is assumed that six printing plates using (transparent) ink are overprinted in this printing order and printing is performed. A pixel to be subjected to the synthesis processing is selected. The pixel value expressed in percent (%) is: Kin (non-transparent) v1 = 60% K (transmitted) v2 = 10% C (transmitted) v3 = 50% Special red (non-transparent) v4 = 80% M (transmitted) ) Let v5 = 100% Y (transmission) v6 = 30%.

The combining process is performed on the above pixels. First, variable initialization is performed. That is, variable initialization: Cp, Mp, Yp, Kp = 0% Cc, Mc, Yc, Kc = 0% t = 100%

The processing of the kin (impermeable) in the first printing order is performed. Multiply pixel value by transparency: v '= v1 * t = 60% Perform special color gamma correction: v "= γkin (v') = 52% Perform process color conversion: C '= Sckin (v") ) = 6% M ′ = Sm kin (v ″) = 4% Y ′ = Sy kin (v ″) = 51% K ′ = Sk kin (v ″) = 3%

Performing process color integration: Cc = Cc + C ′ = 6% Mc = Mc + M ′ = 4% Yc = Yc + Y ′ = 51% Kc = Kc + K ′ = 3% Subtraction subtraction Perform: t = t−v ′ = 40%

The processing of K (transmission) in the next printing order is performed. Multiply pixel value by transmittance: v '= v2 * t = 4% Perform K-color γ correction: γk (v ′) = 3% Integrate to Kp: Kp = Kp + γk (v ′) = 3%

The processing of C (transmission) in the next printing order is performed. Multiply pixel value by transmittance: v '= v3 * t = 20% Integrate into Cp: Cp = Cp + v' = 20%

The special red (non-transparent) processing in the next printing order is performed. Multiply pixel value by transparency: v '= v4 * t = 32% Perform special color gamma correction: v "= γ special red (v') = 26% Perform process color conversion: C '= Sc special red ( v ′) = 0% M ′ = Sm special red (v ″) = 40% Y ′ = Sy special red (v ″) = 44% K ′ = Sk special red (v ″) = 0%

Process color integration is performed: Cc = Cc + C ′ = 6% Mc = Mc + M ′ = 44% Yc = Yc + Y ′ = 95% Kc = Kc + K ′ = 3% Perform: t = t−v ′ = 8% Transmission is less than threshold 10% (t <T = 10
%). Therefore, it breaks out of the loop.

Perform a color matching operation: Cp '= Fc (Cp, Mp, Yp) = 24% Mp' = Fm (Cp, Mp, Yp) = 3% Yp '= Fy (Cp, Mp, Yp) = 5 %

Add process color and spot color (process color addition): C = Cp '+ Cc = 30% M = Mp' + Mc = 47% Y = Yp '+ Yc = 100% K = Kp + Kc = 6%

Therefore, C = 30% M = 47% Y = 100% K = 6% is obtained as a pixel value to be output to DDCP.

[0067]

[Embodiment 3] Next, the combining process will be described based on another embodiment (part 3). Kin (impermeable), K (impermeable), C (impermeable), special red (impermeable), M (impermeable), Y
It is assumed that six printing plates using (transparent) ink are overprinted in this printing order and printing is performed. A pixel to be subjected to the synthesis processing is selected. The pixel value expressed in percent (%) is: Kin (non-transparent) v1 = 60% K (transmitted) v2 = 10% C (transmitted) v3 = 50% Special red (non-transparent) v4 = 80% M (transmitted) ) Let v5 = 100% Y (transmission) v6 = 30%.

The combining process is performed on the above-mentioned pixels. First, variable initialization is performed. That is, variable initialization: Cp, Mp, Yp, Kp = 0% Cc, Mc, Yc, Kc = 0% t = 100%

The first printing order of kin (impermeable) is processed. Multiply the pixel value by the transparency: v '= v1 * t = 60% Perform special color γ correction and process color conversion: C ′ = C kin × γc (v ′) = 6% M ′ = M kin × γm ( v ′) = 4% Y ′ = Y kin × γy (v ′) = 51% K ′ = K kin × γk (v ′) = 3%

Performing process color integration: Cc = Cc + C ′ = 6% Mc = Mc + M ′ = 4% Yc = Yc + Y ′ = 51% Kc = Kc + K ′ = 3% Perform: t = t−v ′ = 40%

The processing of K (transmission) in the next printing order is performed. Multiply pixel value by transmittance: v '= v2 * t = 4% Perform K-color γ correction: γk (v ′) = 3% Integrate to Kp: Kp = Kp + γk (v ′) = 3%

The processing of C (transmission) in the next printing order is performed. Multiply pixel value by transmittance: v '= v3 * t = 20% Integrate into Cp: Cp = Cp + v' = 20%

The special red (opaque) processing in the next printing order is performed. Multiply pixel value by transmittance: v '= v4 * t = 32% Perform special color γ correction and process color conversion: C ′ = C special red × γc (v ′) = 0% M ′ = M special red × γm (v ′) = 40% Y ′ = Y special red × γy (v ′) = 44% K ′ = K special red × γk (v ′) = 0%

Perform process color integration: Cc = Cc + C ′ = 6% Mc = Mc + M ′ = 44% Yc = Yc + Y ′ = 95% Kc = Kc + K ′ = 3% Perform: t = t−v ′ = 8% Transmission is less than threshold 10% (t <T = 10
%). Therefore, it breaks out of the loop.

Perform color matching operation: Cp ′ = Fc (Cp, Mp, Yp) = 24% Mp ′ = Fm (Cp, Mp, Yp) = 3% Yp ′ = Fy (Cp, Mp, Yp) = 5 %

Add process color and spot color (process color addition): C = Cp '+ Cc = 30% M = Mp' + Mc = 47% Y = Yp '+ Yc = 100% K = Kp + Kc = 6%

Therefore, C = 30% M = 47% Y = 100% K = 6% is obtained as the pixel value to be output to DDCP.

As described above, the present invention has been described based on the embodiments. However, the present invention is not limited to the embodiments, and is embodied in various forms based on the technical idea of the present invention. It goes without saying that they are also included in the present invention. For example, in the embodiment, the characteristics of the ink relating to the transmittance are classified into two types: “opaque” having a hiding property and “transmitting” having a transparency. In cases where color reproduction is significantly affected, an intermediate characteristic, for example, "semi-transmission" can be provided. Then, in the synthesizing process, in the determination in step S110 (see FIG. 6), the process branches into three. In the case of “transparent”, the subtraction of the transmittance is not performed.
Assuming that a predetermined coefficient between 0 and 1 is ρ, t = t−ρ * v ′
Is performed, and in the case of "non-transparency", the calculation of t = tv 'can be performed.

[0079]

As described above, according to the color proofing method according to the first aspect of the present invention, a gradation-converted pixel value obtained by performing gradation conversion on a pixel value of a special color is obtained. A color proofing method with good color reproducibility is provided when printing is performed by using the color proofing method. Further, according to the color proofing method according to claim 2 of the present invention, when printing is performed using not only process inks but also special color inks, the order in which process inks and special color inks are overprinted, and the transmittance of those inks. Is provided, and a color proofing method with good color reproducibility is provided.
Further, according to the color proofing method of the third aspect of the present invention, a pixel value v ′ whose gradation has been converted from the pixel value v of the special color n is obtained by the gradation conversion function γn (v) of the special color n. Tone conversion is performed on the pixel value itself. According to the color proofing method of the present invention, gradation conversion is performed on the pixel value of each process color corresponding to the pixel value of the special color.
According to the color proofing method of the fifth aspect of the present invention, the pixel values Cs, Ms, Ys, and Ks of each process color corresponding to the reference pixel value (for example, 100%) of the special color and the pixel value of the special color are used. The gradation conversion function γc (v) of each corresponding process color,
From γm (v), γy (v), γk (v), the gradation-converted pixel values C, M, Y, and K of each process color corresponding to the pixel value of the spot color are obtained from the pixel value v of the spot color. Can be Further, according to the color proofing method according to claim 6 of the present invention, a plurality of tone conversion functions γnc (v), γnm (v), γny (v) corresponding to each of the plurality of special colors n as the tone conversion function. , Γn
k (v) is used. According to the color proofing method of the present invention, the pixel value of each process color corresponding to the pixel value of the special color can be obtained based on the special color correspondence table. Further, according to the color proofing method of the present invention, a gradation conversion function for gradation conversion can be obtained based on the special color correspondence table. According to the color proofing method of the ninth aspect of the present invention, the pixel of the special color is adjusted so that the colorimetric value of the special color by the printing press matches the colorimetric value of the special color by the proof output device using the process color. A spot color correspondence table, which is a correspondence table between values and pixel values of process colors, is generated. Further, according to the color proofing method according to the tenth aspect of the present invention, the process color correspondence table and / or the spot color correspondence table can be referred to in a value that does not exist by applying the interpolation method. According to the color proofing method according to the eleventh aspect of the present invention, a tone conversion function can be obtained only by two values of solid and middle, so that simple and good color reproducibility can be obtained. Further, according to the color proofing method of the twelfth aspect of the present invention, a gradation conversion function including the value of the shadow is obtained, so that the simplicity can be obtained, and particularly good color reproducibility can be obtained even in the shadow. According to the color proofing method according to the thirteenth aspect of the present invention, the gradation conversion function including the value of the highlight is obtained, so that the simplicity and particularly the excellent color reproducibility of the highlight can be obtained. Further, according to the color proofing device according to the fourteenth aspect of the present invention, since a gradation-converted pixel value obtained by performing gradation conversion on the pixel value of the special color is obtained, the printing is performed using the special color ink. And a color proofing device having good color reproducibility.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color proofing device of the present invention.

FIG. 2 is a diagram showing an overall process of data processing in the color proofing device of the present invention.

FIG. 3 is a diagram showing a data conversion process in the color proofing method and apparatus of the present invention.

FIG. 4 is a diagram showing a basic concept regarding a synthesis process in the color proofing method and apparatus of the present invention.

FIG. 5 is a flowchart (first half) showing details of a synthesis process in the color proofing method and apparatus of the present invention.

FIG. 6 is a flowchart (second half) showing details of a synthesis process in the color proofing method and apparatus of the present invention.

FIG. 7 is a diagram (part 1) illustrating an example of a gradation conversion function to which an interpolation method is applied;

FIG. 8 is a diagram (part 2) illustrating an example of a gradation conversion function to which an interpolation method is applied;

FIG. 9 is a diagram (part 3) illustrating an example of a gradation conversion function to which an interpolation method is applied;

FIG. 10 is a diagram (part 4) illustrating an example of a gradation conversion function to which an interpolation method is applied;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Input device 2 Computing device 3 Display device 4 Storage device 5 Output device 31 Synthetic information 32a Continuous color data of process color 32b Line drawing data of process color 32c Continuous tone data of special color 32d Line drawing data of special color 33a Separation process of process color data 33b Separation processing of special color continuous tone data 32c 33c Separation processing of special color line drawing data 32d 34a C plane data 34b M plane data 34c Y plane data 34d K plane data 34e Golden plane data 34f Special one plane data 34g White plane Data 34h Special two-color plate data 34i Special three-color plate data 35a, 35b, 35c, 35d, 35e, 35f, 3
5g, 35h, 35i Single color curve adjustment (gradation conversion) processing of each color plate data 36a Adjusted C plate data 36b Adjusted M plate data 36c Adjusted Y plate data 36d Adjusted K plate data 36e Adjustment Gold plate data 36f Adjusted special color plate data 36g Adjusted white plate data 36h Adjusted special two color plate data 36i Adjusted special three color plate data 37 Color matching calculation processing 37d K plate (black plate ) Curve adjustment (gradation conversion) processing 37e, 37f, 37g, 37h, 37i Each special color curve adjustment (gradation conversion) processing 38a, 38b, 38c C, M, Y plane data 38d generated by color matching calculation processing , 38e, 38f, 38g, 38h, 38i Each of gradation-converted gold, special one color, white, special two colors, and special three colors Color plate data 39 Compositing processing 40 Print data to be output to an output device that performs proof printing

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/46 H04N 1/40 D // G03F 3/10 1/46 Z F term (Reference) 2C250 EA12 EA13 2G020 AA08 DA05 DA14 DA43 5B057 AA12 CA01 CB01 CE11 CE17 CH07 5C077 LL12 MP08 PP15 PP33 PP37 PQ23 TT08 5C079 HA18 HB03 KA04 LA12 LB01 MA05 MA10 NA03 PA07

Claims (14)

[Claims] 1. A color proofing method for simulating color reproduction by a printing press in a proofreading output machine, wherein a special color is obtained by performing a gradation conversion on a pixel value of a special color in the printing press to obtain a pixel value after the gradation conversion. A color proofing method comprising a gamma correction operation process. 2. The color proofing method according to claim 1, further comprising a simulation operation step of performing a simulation operation of the printing of each color based on the printing order and transmittance of each color in the printing press. Color proofing method. 3. The color proofing method according to claim 1, wherein, in said gradation conversion, n is a positive integer, v is a pixel value of the special color n, and γn (v ) Is a tone conversion function of the special color n, and v ′ is a pixel value after the tone conversion, and is performed based on the following equation (1). ## EQU1 ## v ′ = γn (v) 4. The color proofing method according to claim 1, wherein said gradation conversion is performed as a gradation conversion of a pixel value of each process color corresponding to a pixel value of a special color. Method. 5. The color proofing method according to claim 4, wherein in said gradation conversion, v is a pixel value of a special color, γc (v), γm
(V), γy (v) and γk (v) are represented by gradation conversion functions of each process color corresponding to the pixel value of the special color, Cs, Ms, Ys,
Ks is the pixel value of each process color corresponding to the reference pixel value (for example, 100%) of the special color, and C, M, Y, and K are the pixel values of each process color corresponding to the pixel value of the special color after gradation conversion. A color proofing method performed based on the following equation (2). C = Cs × γc (v) M = Ms × γm (v) Y = Ys × γy (v) K = Ks × γk (v) 6. A color proofing method according to claim 5, wherein n is a positive integer and a plurality of tone conversion functions γnc (v), γnm (v), γny (v),
A color proofing method characterized by having γnk (v). 7. A color proofing method according to claim 4, wherein
The pixel value of each process color corresponding to the pixel value of the spot color is:
A color proofing method obtained based on a special color correspondence table. 8. A color proofing method according to claim 1, wherein said tone conversion function for said tone conversion is obtained based on a special color correspondence table. 9. The color proofing method according to claim 7, wherein the spot color correspondence table is obtained by a process color correspondence table generation step and a spot color correspondence table generation step. Output a color patch whose pixel value of the process color is known by the proof output device,
Colorimetric values obtained by measuring each (for example, L ^* a ^* b ^* values)
A process color correspondence table, which is a correspondence table between pixel values of the process color and the colorimetric values, based on the process, wherein the spot color correspondence table generation step is a color patch in which pixel values of the spot color are known in the printing press. Print, referring to the process color correspondence table based on the colorimetric value obtained by measuring each,
A color correction method for generating a special color correspondence table which is a correspondence table between the pixel values of the special color and the pixel values of the process color. 10. A color proofing method according to claim 9, wherein a pixel value of a process color, a colorimetric value, and a pixel value of a special color are interpolated by a value not present in said process color correspondence table and / or special color correspondence table. A color proofing method characterized by applying the following. 11. The color proofing method according to claim 1, wherein the gradation conversion function for gradation conversion is:
Applying the interpolation method based on the value of the tone conversion function when the spot color is solid (pixel value 100%) and the value of the tone conversion function when the spot color is middle (pixel value about 50%). Characteristic color proofing method. 12. The color proofing method according to claim 11,
A color proofing method, wherein the tone conversion function for tone conversion further applies an interpolation method based on the value of the tone conversion function when the spot color is shadow (pixel value: about 90%). 13. The color proofing method according to claim 11, wherein the gradation conversion function for the gradation conversion further includes a gradation conversion function for a spot color having a highlight (pixel value of about 10%). A color proofing method characterized by applying an interpolation method based on a value. 14. A color proofing method for simulating color reproduction by a printing press in a proofreading output machine, wherein a tone color is obtained by performing a tone conversion on a pixel value of a spot color in the printing press to obtain a pixel value after the tone conversion. A color proofing device comprising gamma correction calculating means.