JP2019016924A - Print color adjustment system and print color adjustment method - Google Patents

Abstract

To provide a print color adjustment system for adjusting the control value of a print device, corresponding to ink adjustment by area modulation gradation or concentration modulation gradation of a printer, so that the color of a print printed by a simple print device matches the color of a print printed by area modulation gradation or concentration modulation gradation in the printer.SOLUTION: A print color adjustment system includes a color profile generation section generating the color profile of a first printer printing a print, by using a print color prediction model for obtaining the prediction value of color of the print printed from a command value of area modulation gradation or concentration modulation gradation, from the colorimetric value of each solid printing of the ink used in the print printed by area modulation gradation or concentration modulation gradation, and a print control section for obtaining the prediction value of a color corresponding to the command value of the dots of image data of the print, in a color profile, and converting this prediction value, as the color information of the color of a print, into a control value by the color profile of the second printer, before outputting to the second printer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing color adjustment system and a printing color adjustment method for adjusting the color of a printed matter output by an inkjet printer or a digital printing machine to the color of the printed matter obtained by printing ink with halftone dots.

In gravure printing, screen printing, offset printing, etc., the reproduction color is adjusted by area modulation (area modulation gradation expression) or density modulation (density modulation gradation expression), and a predetermined image is printed on the print medium. .
These printing methods are suitable for large-scale printing that prints a large number of sheets, and are not suitable for printing a small number of sheets because of cost.
For this reason, when the number of printed materials is insufficient, it is costly to reprint by the above printing. Therefore, it is necessary to print a predetermined number of extra sheets and store them as stock.

However, when storing as inventory, if the extra printed inventory is no longer used, the cost for inventory is wasted.
In addition, it is necessary to secure a place to store the stock, and in order to store a stock of a plurality of types of printed matter, a wide storage place must be prepared, and a lot of useless space is used.

Therefore, when a small amount of reprinting is required, a simple printing device such as an ink jet printer or a digital printing machine is used as an output device for printed matter.
At this time, it is necessary that the color of the printed material printed in large quantities matches the color of the printed material of the simple printing device, and color management for matching is performed. That is, the color profile of a printing press that performs mass printing (the area modulation gradation expression is converted into predetermined reference color information (for example, CIELAB value)), and the color profile of a simple printing device (reference color information is converted into the printing device). Are converted to the control values of the printer and the colors of the printed material printed in large quantities and the printed material of a simple printing device are matched (for example, see Patent Document 1 and Patent Document 2).

JP-T-2007-516663 JP 2006-329753 A

However, if the color of the printed material is deviated from the above color profile due to variations in printing in the printing machine, or the color is intentionally changed, the printed material of a simple printing device printed using the color profile and the printing machine Colors do not match with the printed material printed at.
As for special colors, color profiles are often not created, and even if they exist, it is difficult to match the colors of the printed material of a simple printing device and the printed material printed by a printing machine for the reasons described above. It is.

Further, it is conceivable that the color printed by the simple printing device is adjusted to the color of the printed matter of the printing machine by adjusting the control value (for example, CMYK value) of the printing device.
However, when printing with a plurality of special colors, any special color is tried to be adjusted, for example, by adjusting the CMYK value, all the special colors are changed, and only one special color is changed. Cannot be changed, and the entire color is shifted from the color of the printed matter.

  The present invention has been made in view of such circumstances, and the color of a printed matter printed by a simple printing device matches the color of a printed matter printed by an area modulation gradation expression or density modulation gradation on a printing press. Thus, a printing color adjustment system and a printing color adjustment method for adjusting a control value of a printing device corresponding to an adjustment method of a printing press are provided.

  The printing color adjustment system of the present invention is based on color measurement values for solid printing of ink used for printed matter printed with area modulation gradations and density modulation gradations, from area modulation gradation and density modulation gradation command values. A color profile generation unit that generates a color profile of a first printing press that prints the printed matter using a print color prediction model for obtaining a predicted value of the color of the printed matter to be printed, and image data of the printed matter by the color profile A predicted value of a color corresponding to the command value of each dot is obtained, the predicted value is used as color information of the color of the printed matter, and the color information is converted into a control value by a color profile of a second printing press, and the first And a printing control unit for outputting to the two printing machines.

  The print color adjustment system of the present invention adjusts parameters used for calculation of prediction of the predicted color in the print color prediction model, and corresponds to the parameters adjusted in a plurality of stages, and a plurality of the print color prediction models And an adjustment control unit that generates a plurality of color profiles, and the print control unit outputs each control value obtained from each of the color profiles to the second printing machine. And

  In the print color adjustment system of the present invention, the print color prediction model uses the absorption coefficient and the scattering coefficient of each solid print of ink to predict the predicted value when the ink is overprinted, and It includes a process for obtaining the spectral reflectance of each dot by the Kubelka-Munk equation.

  The printing color adjustment system of the present invention is characterized in that the thickness of the ink for solid printing in the Kubelka-Munk equation is used as the parameter.

  The printing color adjustment system of the present invention is characterized in that the color value of the ink for solid printing in the Kubelka-Munk equation is used as the parameter.

  The print color adjustment system according to the present invention is characterized in that the predicted color gradation characteristic in the halftone of the command value is used as the parameter.

The printing color adjustment system according to the present invention provides the ink for solid printing in the Kubelka-Munk equation for obtaining the spectral reflectance of the ink to be overlaid on another ink when changing the predicted color when the ink is overprinted. Is used as the parameter.

  In the printing color adjustment system of the present invention, when the adjustment control unit adjusts the plate deviation of the printed matter, the position of each of the ink plates of the printed matter is shifted, and the printing control unit is shifted in position. In addition, in the overlap of the plates, a predicted value of the color of each dot of the printed matter is obtained.

  The print color adjustment system of the present invention is characterized in that the adjustment control unit superimposes noise on the predicted value of the image data.

  The printing color adjustment method of the present invention includes a color measurement process for measuring a color measurement value of solid printing of each ink used for a printed matter printed with an area modulation gradation and a density modulation gradation, and an area from the color measurement value. Generating a color profile of a first printing press that prints the printed matter using a print color prediction model that obtains a predicted value of the color of the printed matter to be printed from a command value of modulation gradation or density modulation gradation; A predicted color value corresponding to the command value of each dot in the image data of the printed material is obtained from the color profile, the predicted value is used as color information of the color of the printed material, and the color information is obtained from the color profile of the second printing press. The control value is converted and output to the second printing machine, and the color of the printed matter printed by the first printing press is compared with the color of the printed matter printed by the second printing press. And the printing A process of selecting a parameter that needs to be adjusted in the prediction model, and changing the parameter in multiple stages, generating a plurality of print color prediction models, and each of the color profiles corresponding to each of the print color prediction models And a step of causing the second printing machine to print the image data according to control values corresponding to color information obtained from each of the color profiles.

  As described above, according to the present invention, the printing machine is configured so that the color of the printed matter printed by the simple printing device matches the color of the printed matter printed by the area modulation gradation or the density modulation gradation in the printing press. It is possible to provide a printing color adjustment system and a printing color adjustment method for adjusting a control value of a printing device corresponding to ink adjustment by area modulation gradation and density modulation gradation.

1 is a block diagram illustrating a configuration example of a print color adjustment system according to a first embodiment of the present invention. It is a block diagram which shows the structural example of the color prediction model production | generation part 12 in FIG. It is a figure explaining the correspondence of a command halftone dot area rate and the appearance rate of the density gradation field in the halftone dot formed with a command halftone dot area rate. It is a flowchart which determines the compounding ratio of the primary color ink which comprises a special color ink, and calculates the absorption coefficient _Kt ((lambda)) and the scattering coefficient _St ((lambda)) of a special color ink. It is a figure explaining calculation of the density gradation spectral reflectance _Rim ((lambda)) of the ink printed by overlapping on the ink as a foundation | substrate. It is a flowchart which shows the process which calculates a Neugebauer primary color by superposition of a special color ink. It is a figure explaining calculation of the ratio of the appearance rate of the overlap of the density gradation area | region of the background ink, and the density gradation area | region of the ink printed on the background ink (spot color ink or primary color ink). FIG. 8 is a table showing calculation results of appearance rates of areas Q1 to Q9 in FIG. 6 is a flowchart for explaining an operation example of color profile generation processing by the color prediction model generation unit 12 and the color profile generation unit 13 in the present embodiment. 6 is a flowchart for explaining an operation example of an adjustment process in which the color printed by the printing device is the same as the color of the printed matter of the printing press by the printing color adjustment system according to the present embodiment.

In the present invention, a halftone dot printed matter that reproduces the color of an image by printing ink in a halftone dot shape on a printing medium by a technique such as gravure printing, screen printing, and offset printing on a printing press (commercial printing press) When printing the same image data with the same color with a simple printing machine (printing device) such as an ink jet printer or digital printing machine, by adjusting the parameters of the color prediction model that models the dot shape, the ink jet Adjust the printer color.
Hereinafter, in the present embodiment, description will be given for gravure printing.
In gravure printing, when ink is printed on a print medium, halftone dots corresponding to the command halftone dot area ratio indicating the degree of gradation are formed on the surface of the print medium. As for halftone dots, the area of the surface of the print medium on which ink is printed (area modulation gradation expression) and the thickness of the printed ink (density modulation gradation expression) vary depending on the command dot area ratio. . For example, it can be said that the halftone dots formed in printing are similar to the structure of a mountain, the larger the mountain, the wider the base and the higher the height, and the smaller the mountain, the narrower the base and the lower the height. . That is, the halftone dot in printing changes not only the area where the ink is printed but also the thickness of the printed ink according to the command halftone dot area ratio.

  For this reason, in the present invention, the color prediction is performed on the color of each dot in the halftone dot printed matter printed on the printing medium (for example, paper) by using the prediction model. The result (e.g., CIELAB value) is converted into color data in the CMYK format or the like by an ICC (International Color Consortium) profile of the inkjet printer to be printed, and is output to the inkjet printer. As described above, when adjusting the color in printing by the ink jet printer, the color adjustment of the ink jet printer is performed by adjusting the parameters of the color prediction model instead of controlling the control value of the ink jet printer.

Hereinafter, a configuration example of the printing color adjustment system in FIG. 1 will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration example of a print color adjustment system according to the first embodiment of the present invention.
1, the print color adjustment system 1 includes an input control unit 11, a color prediction model generation unit 12, a color profile generation unit 13, an adjustment control unit 14, a control value generation unit 15, a display unit 16, a print data output unit 17, and Each of the storage units 18 is provided.
The input control unit 11 writes the image data for each ink plate used for printing the printed material supplied from the external device in the storage unit 18 and stores the image data.
In addition, the user measures the colorimetric values of the solid print of the ink used for printing the printed matter, and prints the colorimetric values of each ink and the printing order using an input unit (not shown) such as a keyboard. Input to the adjustment system 1. As a result, the input control unit 11 writes and stores the color measurement values for the solid printing of the input inks and the printing order of the inks in the storage unit 18 in association with the printed matter.

The color prediction model generation unit 12 generates a color prediction model indicating the correspondence between the command halftone dot area ratio given to the printing press and the predicted spectral reflectance R (λ) of the print portion (described in detail later). Here, the command halftone dot area ratio is a numerical value given to a commercial printing machine that performs gravure printing or the like as a control value for printing a reference print that is a halftone print. That is, the color prediction model generation unit 12 corresponds to the printing order of each ink, obtains a predicted spectral reflectance R (λ) for each combination of command halftone dot area ratios of the inks, and calculates the predicted spectral reflectance R (λ ) To calculate a color measurement value and generate a color prediction model (color prediction table) indicating the correspondence between the command dot area ratio and the color measurement value.
The color profile generation unit 13 converts into a known ICC profile format based on the color prediction model (color prediction table), and generates a converted color profile (also referred to as a color prediction profile).

The adjustment control unit 14 adjusts parameters used in an equation used when obtaining the predicted spectral reflectance R (λ) in the color prediction model in a plurality of stages. Then, the adjustment control unit 14 outputs the adjusted parameters of a plurality of stages to the color prediction model generation unit 12, and generates a color prediction model corresponding to each parameter. Here, when a plurality of types of parameters are adjusted in multiple stages, the number of color prediction models corresponding to the combination of each stage of the plurality of types of parameters is generated. For example, when each of the five types of parameters is adjusted to 5 levels, 5 ⁵ = 3125 is combined, and 3125 color prediction models are generated. Accordingly, the color profile generation unit 13 generates 3125 color profiles based on the 3125 color prediction models.

  The control value generation unit 15 uses the color profile generated by the color profile generation unit 13 to obtain a colorimetric value for predicting the color to be printed based on the command halftone dot area ratio for each ink of the image data. . Then, the control value generation unit 15 obtains a control value corresponding to the predicted colorimetric value by extracting it from the device color profile of the printing device that is about to print a small amount.

The display unit 16 is, for example, a liquid crystal display, and displays an input screen for data necessary for processing, an operation screen for performing operations for processing for generating control values for the printing device, and the like.
The print data output unit 17 outputs the control value for each pixel of the image data as an image data control value to the printing device to print the image.

<Printer color profile generation process>
In the color prediction model described below, the halftone dot structure in printing corresponds to the command halftone dot area ratio, the area of the print medium surface of the halftone dot on which ink is printed, and the ink in the halftone dot to be printed. A calculation model (core fringe model described later) representing thickness is used. That is, when performing color prediction of each gradation degree of a single color or a special color printed on a print medium (for example, paper), halftone dots of each gradation degree generated by the command halftone dot area ratio include a plurality of density gradation areas. A calculation model obtained by modeling a halftone dot shape generated from (same configuration as contour lines) is used.

Hereinafter, the color prediction model generation unit 12 in FIG. 1 will be described with reference to the drawings.
FIG. 2 is a block diagram illustrating a configuration example of the color prediction model generation unit 12 in FIG. In FIG. 2, a color prediction model generation unit 12 includes an input unit 101, a density gradation spectral reflectance calculation unit 102, a density gradation appearance rate calculation unit 103, a density gradation appearance rate table database 104, and a measured spectral reflectance database. 105, absorption coefficient / scattering coefficient database 106, absorption coefficient / scattering coefficient calculation unit 107, spectral reflectance prediction unit 108, spectral optical density prediction unit 111, mixed prediction unit 114, spot color ink spectral reflectance calculation unit 121, spot color ink composition Ratio determination unit 122, spot color ink density gradation appearance rate calculation unit 123, temporary storage unit 125, prediction parameter database 126, approximate color database 128, spot color ink reproduction color calculation unit 129, density tone spectral optical density calculation unit 202, density A gradation appearance rate calculation unit 203 and a density gradation appearance rate table database 204 are provided.

The input unit 101 is connected to, for example, an external computer via the input control unit 11 and inputs data such as a command value of a command halftone dot area ratio of each primary color set by a user and primary color ink. .
Further, the input unit 101 outputs data such as a command value of a command halftone dot area ratio of each primary color of ink set by the user, which is input via the input control unit 11, to each unit in the color prediction model generation unit 12. It is good also as composition to do.

In the absorption coefficient / scattering coefficient database 106, for each primary color ink, the command halftone dot area ratio is 100%, that is, the color of the ink obtained from the printed portion printed on a solid print medium (for example, coated paper). The scattering coefficient S (λ) and absorption coefficient K (λ) of the layer are written and stored in advance by the external computer or the like. Here, when obtaining the scattering coefficient S (λ) and the absorption coefficient K (λ), the printed portion is created by printing the primary color ink solidly on each of the white and black print media.
Then, the spectral reflectance of the colored layer of the ink printed on the surface of each of the white and black print media is measured. Here, the spectral reflectance of the printed portion on the white print medium surface is defined as the white background measured spectral reflectance, and the spectral reflectance of the printed portion on the black print medium surface is defined as the black measured spectral reflectance.
The scattering coefficient S (λ) and the absorption coefficient K (λ) in the printed portion in which the primary color ink is printed on the printing medium with a solid color are obtained from the obtained white background measured spectral reflectance and black background measured spectral reflectance. Further, the scattering coefficient S (λ) and the absorption coefficient K (λ) are obtained at a plurality of wavelengths λ within a predetermined wavelength range.

  In the approximate color database 128, for a plurality of types of spot color inks (reference spot color inks) with different combinations of the blended primary color inks, the colorimetric values of the spot color inks and the blend ratios of the primary colors are written and stored in advance. .

In the measured spectral reflectance database 105, the measured spectral reflectance Rs (λ) of the printed portion printed on the printing medium with a plurality of command halftone dot area ratios for each primary color ink is written and stored in advance by the external computer or the like. Has been. For example, this printed portion is a step chart printed at a command halftone dot area ratio in m stages. When the measured spectral reflectance Rs (λ) is obtained, halftone dots having a plurality of command halftone dot area ratios are respectively printed on a printing medium used for actual printing using primary color ink. Here, s is a command halftone dot area ratio. Then, the spectral reflectance of the printed portion printed on the print medium is measured for each printed portion having a halftone dot of the command halftone area ratio. Further, in the measured spectral reflectance database 105, the base spectral reflectance R ₀ (λ) of the print medium used for actual printing is the same as the above-described measured spectral reflectance Rs (λ). Is previously written and stored.

The temporary storage unit 125 is a storage unit that stores intermediate calculation results of each unit in the present embodiment, and internally includes a scattering absorption coefficient table, a special color ink composition ratio table, a special color ink density gradation appearance rate table, a Neugebauer primary color table, A spectral reflectance table or the like is written and stored.
In the prediction parameter database 126, a weighting coefficient w described later used in the mixed prediction unit 114 in the present embodiment is stored. The weighting coefficient w is printed so that the teacher data is printed and the error between the spectral reflectance obtained from the model created by the weighting coefficient and the spectral reflectance as the printed teacher data is minimized. It has been demanded. Further, when the Yule-Nielsen modified Neugebauer model is used as the spectral reflectance prediction model for the print color, an n value may be set.

Calculation of density gradation appearance rate based on spectral reflectance The density gradation spectral reflectance calculation unit 102 corresponds to the corresponding primary color from the absorption coefficient / scattering coefficient database 106 according to the type of primary color ink supplied from the input unit 101. The ink absorption coefficient K (λ) and scattering coefficient S (λ) are read out. Further, the density gradation spectral reflectance calculation unit 102 determines from the measured spectral reflectance database 105 the measurement spectral for each command halftone dot area ratio according to the type of primary color ink and the type of print medium supplied from the input unit 101. Each of the reflectance Rs (λ) and the base spectral reflectance R ₀ (λ) of the print medium is read out.

Then, the density gradation spectral reflectance calculation unit 102 receives the absorption coefficient K (λ) and the scattering coefficient S (λ) of the primary color ink read from the absorption coefficient / scattering coefficient database 106 measured spectral reflectance database 105, and the printing medium. Each of the base spectral reflectance R ₀ (λ) and the density gradation film thickness coefficient X _m (as will be described later, the film thickness coefficient X _m is changed for each density gradation area) is as follows: Substituting into the equation (Kuberka-Munk equation), density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ),..., R _im (λ) are calculated.
In the following equation (1), a (λ) is a numerical value obtained by adding the scattering coefficient S (λ) and the absorption coefficient K (λ) and dividing the addition result by the scattering coefficient S (λ). b (λ) is a numerical value obtained by subtracting 1 from a numerical value obtained by squaring a (λ) and calculating the square root of the subtraction result.

In this embodiment, expression of the Kubelka-Munk shown in above-mentioned (1) (Kubelka-Munk), namely (1) the thickness of coefficients X _m of printed ink in the equation, the print medium primary ink in solid Based on the printed part, it is used as a numerical value indicating the density gradation of the printed part. That is, the film thickness coefficient _Xm is arbitrarily set. For example, the solid print portion having the thickest ink film thickness is set to 100%, the film thickness coefficient is set to 1, and this 1 is a density gradation. The area is divided into m corresponding to the number m of film thicknesses in the region. For example, if there are five stages of film thickness in the density gradation area indicated by the command halftone dot area ratio, m = 1, 2, 3, 4, 5 and the film thickness coefficient _Xm is the respective density scale. Corresponding to the thickness of the tone region, X ₁ = 1.0, X ₂ = 0.8, X ₃ = 0.6, X ₄ = 0.4, and X ₅ = 0.2.

The thickness factor X _m, as already mentioned, the underlying spectral reflectance R ₀ of the base of the print medium _(lambda), and the absorption coefficient K (lambda), together with the scattering coefficient S (lambda) in equation Kubelka-Munk The density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R are substituted as spectral reflectances of the density gradation regions included in the halftone dots of the respective command halftone area ratios by substituting them into a certain equation (1). Each of _i3 (λ),..., R _im (λ) is calculated. The density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ),..., R _im (λ) are used for a plurality of density levels constituting a halftone dot used in a calculation model described later. Used as the spectral reflectance of each of the tonal regions.

The density gradation appearance rate calculation unit 103 receives density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ),..., R _im ( Read each of λ). Further, the density gradation appearance rate calculation unit 103 reads each of the measured spectral reflectances Rs (λ) for each command halftone dot area rate from the measured spectral reflectance database 105.
Then, the density gradation appearance rate calculating unit 103 performs density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ), ..., each of R _im (λ) is substituted, and a calculated spectral reflectance R ′ (s, λ) is calculated by a process described later.

Here, the density gradation appearance rate calculation unit 103 is a numerical value of the appearance rate (area ratio of the density gradation area of each density gradation constituting the halftone dot in the print portion of the paper) in the following equation (3). The calculated spectral reflectance R ′ (s, λ) is calculated while changing. Then, the density gradation appearance rate calculating unit 103 calculates the mean square error RMSE between each of the calculated calculated spectral reflectances R ′ (s, λ) and the measured spectral reflectance Rs (λ) as a command halftone dot area. Each rate is obtained in a predetermined wavelength range.
The density gradation appearance rate calculation unit 103 obtains the appearance rate of each density gradation region where the mean square error between the calculated spectral reflectance R ′ (s, λ) and the measured spectral reflectance Rs (λ) is the smallest. . Here, s is a command halftone dot area ratio.

Then, the density gradation appearance rate calculation unit 103 determines the appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s) of each density gradation region based on the appearance rates of the density gradation regions. ..., a _m (s) is obtained. Here, the density gradation appearance rate calculation unit 103 uses the appearance rate obtained for each density gradation region to fit this appearance rate with a quadratic function of the command halftone dot area rate s, and the like. The functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m (s) may be obtained. Density gradation appearance ratio calculating unit 103, the appearance of each gray scale region determined function _{a 1 (s), a 2} (s), a 3 (s), ..., a m a (s), concentration Floor It is written and stored in the key appearance rate table database 104.

In the above equation (3), the density gradation appearance rate calculation unit 103 calculates the mean square error RMSE obtained by adding the square of the error at each wavelength λ by the step size obtained by dividing the wavelength λ from 380 nm to 730 nm by n. Calculated for each area ratio.
As described above, the density gradation appearance rate calculation unit 103 uses the calculation model (2) to print, for each density gradation included in a halftone dot, in a printed portion where ink is printed according to the command halftone area ratio. , Density gradation spectral reflectance R _im (λ) of density gradation and density gradation appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m (s) Are added together to calculate the spectral reflectance R ′ (s, λ) (calculated spectral reflectance) of the printed portion of the command dot area ratio.

FIG. 3 is a diagram for explaining the correspondence relationship between the command halftone dot area ratio and the appearance rate of the density gradation area in the halftone dots formed with the command halftone dot area ratio. In FIG. 3A, the horizontal axis represents the command halftone dot area rate s, and the vertical axis represents the appearance rate a. With the appearance rate function a _m (s), the appearance rate of each density gradation area in the command halftone dot area rate can be obtained. As already described, the density gradation appearance rate calculation unit 103 sets each of the appearance rate functions a _m (s) for each density gradation region to a density scale corresponding to the command halftone dot area ratio obtained by the equation (3). The appearance rate for each key area is obtained by functioning as an approximate expression of a quadratic function. FIG. 3A shows the appearance rate functions a ₁ (s), a ₂ (s), and a ₃ (s) for each of the density gradation areas of the four gradations when m = 4. , A ₄ (s).

FIG. 3B is a diagram illustrating the shape of the halftone dots in plan view in each of the command halftone dot area ratios s ₁ , s ₂ , s ₃ , and s ₄ in FIG. In the command area coverage s _1, only the density gradation region P ₁ is formed. Further, at the command halftone dot area ratio s ₂ , the density gradation area P ₂ is formed inside the density gradation area P ₁ . In the command area coverage s _3, only the density gradation region P ₂ is formed. In the command area coverage s _4, density gradation region P ₄ in the interior of the density gradation region P ₃ is formed. As described above, in the present embodiment, the halftone dot structure in the gravure printing is modeled as the halftone dot structure shown in FIG.

Returning to FIG. 2, the density gradation appearance rate calculation unit 103 calculates an appearance rate function a _m (s) indicating the appearance rate of each density gradation region in the calculated halftone dot area ratio of the obtained density gradation region. The tone appearance rate table database 104 is written and stored in correspondence with the density gradation spectral reflectance of the density gradation region. Similarly, the density gradation appearance rate calculation unit 103 also applies the appearance rate function a _m indicating the appearance rate of each density gradation area to the command halftone dot area ratio of the density gradation area for each of the other primary color inks. (S) is written and stored in the density gradation appearance rate table database 104.

The spot color ink spectral reflectance calculation unit 121 reads the spot color ink whose colorimetric value is the closest to the color measurement value of solid printing of the ink used for the printed material from the spot color inks having different combinations of primary color inks in the approximate color database 128. The approximate color database 128 stores the colorimetric value of primary color ink and the mixing ratio of primary colors, and the primary color combination of the special color ink that reproduces the colorimetric value of solid printing is based on the read ratio of primary color of the special color ink. Set as a ratio.
Further, the spot color ink spectral reflectance calculation unit 121 reads the base spectral reflectance R ₀ (λ) of the print medium from the measured spectral reflectance database 105.
From the absorption coefficient / scattering coefficient database 106, the absorption coefficient / scattering coefficient calculation unit 107 calculates the absorption coefficient K of each of the primary color inks, for example, the primary color ink # 1 and the primary color ink # 2, which constitute the primary color ink included in the set blending ratio. ₁ (λ) and K ₂ (λ) and the scattering coefficients S ₁ (λ) and S ₂ (λ) are read out.

Then, the absorption coefficient / scattering coefficient calculation unit 107 calculates the absorption coefficient K _t (λ) and the scattering coefficient S _t (λ) of the special color ink mixed with the primary color ink by the following equation (4). In the case of this special color ink, the scattering coefficient S _t (λ) and the absorption coefficient K _t (λ) of the special color ink are calculated in the following equation (4) according to the ratio of the primary color ink to be mixed. Further, the spot color ink spectral reflectance calculation unit 121 writes and stores each of the obtained scattering coefficient S _t (λ) and absorption coefficient K _t (λ) of the spot color ink in the scattering absorption coefficient table of the temporary storage unit 125. .

In the above equation (4), each of the coefficient α and the coefficient β is a coefficient indicating a mixing ratio of the primary color ink # 1 and the primary color ink # 2. The absorption coefficient K ₁ (λ) of the primary color ink # 1 is multiplied by the coefficient α, the absorption coefficient K ₂ of the primary color ink # 2 is multiplied by the coefficient β, and the sum is obtained as the absorption coefficient K of the special color ink. _t (λ). Similarly, the scattering coefficient S ₁ (λ) of the primary color ink # 1 is multiplied by a coefficient α, the scattering coefficient S ₂ (λ) of the primary color ink # 2 is multiplied by a coefficient β, and the added numerical value is The scattering coefficient S _t (λ) of the special color ink is used.

As a result, the spot color ink spectral reflectance calculation unit 121 uses the absorption coefficient K _t (λ) and the scattering coefficient S _t (λ) and the base spectral reflectance R ₀ (λ) of the printing medium with respect to the equation (1). and substituting each of a thickness factor X _m of gray scale to determine the spectral reflectance of the spot inks R _{KM (λ).}
The spot color ink reproduction color calculation unit 129 sets the spectral distribution of the light source in the observation environment and the standard observer with respect to the spectral reflectance R _KM (λ) of the spot color ink calculated by the spot color ink spectral reflectance calculation unit 121. It is converted into a colorimetric value (for example, L * a * b * value) and output to the special color ink blending ratio determining unit 122.

  The spot color ink blending ratio determination unit 122 checks the color difference between the color measurement value obtained by the special color ink reproduction color calculation unit 129 and the solid color measurement value. Then, when the color difference is within a preset allowable range, the spot color ink blending ratio determining unit 122 determines the blending ratio of each primary color ink in the color obtained by the spot color ink spectral reflectance calculating unit 121 as the sample spot color ink. Are written and stored together with the special color ink identification information, which is the identification information of the special color ink, in the special color ink combination ratio table of the temporary storage unit 125 as the type of primary color ink and the mixing ratio thereof.

FIG. 4 is a flowchart for determining the mixing ratio of the primary color inks constituting the special color ink and calculating the absorption coefficient K _t (λ) and the scattering coefficient S _t (λ) of the special color ink.
Step S101:
The user measures the color measurement value of solid printing used for reproduction and inputs it to the color prediction model generation unit 12.

Step S102:
The spot color ink spectral reflectance calculator 121 reads the base spectral reflectance R ₀ (λ), which is the spectral reflectance of the print medium, from the measured spectral reflectance database 105.

Step S103:
Next, the spot color ink spectral reflectance calculation unit 121 reads a combination of primary color inks constituting the spot color ink from the approximate color database 128. For example, at this time, the spot color ink spectral reflectance calculation unit 121 extracts and selects the spot color ink having the color measurement value closest to the color measurement value acquired from the solid printing from the approximate color database 128.

Step S104:
The absorption coefficient / scattering coefficient calculation unit 107 reads the scattering coefficient S (λ) and the absorption coefficient K (λ) of the primary color ink constituting the special color ink selected in step S103 from the absorption coefficient / scattering coefficient database 106.

Step S105:
The spot color ink blending ratio determining unit 122 sets an initial value for the blending ratio of each primary color ink constituting the spot color ink. As the initial value, the special color mixture ratio extracted from the approximate color database 128 in step S103 is set.

Step S106:
Next, as shown in equation (4), the absorption coefficient / scattering coefficient calculation unit 107 multiplies the mixing ratio of each primary color ink by the scattering coefficient S (λ) and the absorption coefficient K (λ) of the primary color ink, respectively. .
Then, the absorption coefficient / scattering coefficient calculation unit 107 adds the multiplication results, thereby obtaining the scattering coefficient S _t (λ) and the absorption coefficient K of the special color ink at the blending ratio (for example, α, β in the equation (4)). _t (λ) is calculated.

The spot color ink spectral reflectance calculation unit 121 substitutes the base spectral reflectance R ₀ (λ), the scattering coefficient S _t (λ), and the absorption coefficient K _t (λ) of the printing medium into the equation (1). Then, the spectral reflectance of the special color ink is calculated. Further, the spot color ink reproduction color calculation unit 129 calculates a colorimetric value from the spectral reflectance of the spot color ink calculated by the spot color ink spectral reflectance calculation unit 121.
The spot color ink blending ratio determination unit 122 calculates a color difference between the color measurement value L * a * b * value for solid printing and the color measurement value L * a * b * value obtained by the spot color ink reproduction color calculation unit 129.

Step S107:
Then, the spot color ink blending ratio determining unit 122 determines whether or not the color difference is within a preset allowable range.
At this time, if the color difference is within the preset allowable range, the spot color ink mixture ratio determination unit 122 advances the process to step S108. On the other hand, when the color difference is not within the preset allowable range, the spot color ink blending ratio determining unit 122 advances the process to step S110.

Step S108:
Next, the spot color ink blending ratio determining unit 122 sets the blend ratio of the primary color ink in the spot color ink corresponding to the solid printing as the current blending ratio.
Then, the spot color ink blending ratio determination unit 122 writes the type of the primary color ink in the spot color ink and the blending ratio of each primary color ink in the blending ratio table of the temporary storage unit 125 and stores them.

Step S109:
Next, the spot color ink blending ratio determination unit 122 calculates the scattering coefficient S _t (λ) and the absorption coefficient K _t (λ) of the spot color ink corresponding to the solid printing, the current scattering coefficient S _t (λ), and the absorption coefficient K. Let _t (λ).
Then, the spot color ink blending ratio determining unit 122 writes and stores the scattering coefficient S _t (λ) and the absorption coefficient K _t (λ) of the spot color ink in the scattering absorption coefficient table of the temporary storage unit 125.

Step S110:
The spot color ink blending ratio determining unit 122 determines whether or not the number of blending ratio changes is within a preset rule.
At this time, if the number of changes in the mixture ratio is within a preset specified number, the spot color ink mixture ratio determination unit 122 advances the process to step S111. On the other hand, when the number of changes in the mixture ratio exceeds the preset number of times set in advance, the spot color ink mixture ratio determination unit 122 advances the process to step S112.

Step S111:
The spot color ink blending ratio determining unit 122 changes the blending ratio of each primary color ink constituting the spot color ink.
Then, the special color ink blending ratio determining unit 122 increments a counter that counts the number of times of blending ratio change (increases the count value by one), and advances the process to step S106.

Step S112:
The spot color ink mixture ratio determination unit 122 displays a selection screen for selecting whether or not to change the combination of primary color inks on a display unit (not shown) of the color prediction model generation unit 12.
When the user selects to change the combination of primary color inks, the spot color ink mixture ratio determination unit 122 advances the process to step S113. On the other hand, when the user selects not to change the combination of primary color inks, the special color ink composition ratio determination unit 122 advances the process to step S108.

Step S113:
The spot color ink blending ratio determining unit 122 resets a counter that counts the number of times the blending ratio is changed, and sets the count value, that is, the number of changes to “0”.

Step S114:
The spot color ink blending ratio determination unit 122 outputs a control signal for changing the combination of primary color inks to the spot color ink spectral reflectance calculation unit 121.
The spot color ink spectral reflectance calculation unit 121 newly reads a combination of primary color inks constituting the spot color ink from the approximate color database 128.

Returning to FIG. 2, the spot color ink density gradation appearance rate calculation unit 123 obtains an appearance rate function a _m (s) for each density gradation area of the spot color ink generated by mixing the primary color inks at a predetermined ratio. Then, the spot color ink density gradation appearance rate calculation unit 123 writes the obtained appearance rate function a _m (s) into the spot color ink density gradation appearance rate table of the temporary storage unit 125 and stores it. Here, the spot color ink density gradation appearance rate calculation unit 123 reads out the appearance rate function a _m (s) of any primary color ink constituting the spot color ink from the density gradation appearance rate table database 104, and this spot color ink. Is an appearance rate function a _m (s). Further, the spot color ink density gradation appearance rate calculating unit 123 combines the appearance rate functions a _m (s) of the primary color inks constituting the spot color ink according to the blending ratio of the primary color inks, and the spot color ink appearance rate. The function a _m (s) may be used.

Operation of Spectral Reflectance Prediction Unit 108 Next, the spectral reflectance prediction unit 108 includes an extended Neugebauer primary color calculation unit 1081, an extended Neugebauer primary color appearance rate calculation unit 1082, and a spectral reflectance calculation unit 1083.
The extended Neugebauer primary color calculation unit 1081 determines ink (primary color ink or special color ink) to be a base and ink to be printed on the surface of the base in accordance with the order of colors to be superimposed. Further, the extended Neugebauer primary color calculation unit 1081 reads from the input unit 101 the command halftone dot area rate of each ink to be superimposed.

The extended Neugebauer primary color calculation unit 1081 reads from the absorption coefficient / scattering coefficient database 106 the scattering coefficient S (λ) and the absorption coefficient K (λ) of the primary color ink that overlaps the underlying ink. Further, the extended Neugebauer primary color calculation unit 1081 reads the scattering coefficient S _t (λ) and the absorption coefficient K _t (λ) of the special color ink that overlaps the base ink from the scattering absorption coefficient table of the temporary storage unit 125.

Next, the extended Neugebauer primary color calculation unit 1081 calculates the density gradation spectral reflectance R _im (λ) of the density gradation area at the halftone dot of the ink (spot color ink or primary color ink) as the background in the formula (1). Substituting as the reflectance R ₀ (λ), and substituting the scattering coefficient S (λ) and absorption coefficient K (λ) of the ink overlapping the underlying ink and the film thickness coefficient X _m of the density gradation region. By doing so, the density gradation spectral reflectance R _im (λ) in the density gradation area constituting the halftone dot of the ink printed on the underlying ink is calculated.

Here, the extended Neugebauer primary color calculation unit 1081 includes the density gradation area of the halftone dot of the background ink and the density gradation area constituting the halftone dot of the ink printed on the background ink. The density gradation spectral reflectance R _im (λ) of the overlapping portion is calculated based on the density gradation area at the halftone dot of the background ink and the ink (spot color ink or primary color ink) printed on the halftone dot of the background ink. This is performed for all combinations of the halftone dots with the density gradation region.

FIG. 5 is a diagram for explaining the calculation of the density gradation spectral reflectance R _im (λ) of the ink printed over the ink as the base.
The density gradation spectral reflectance calculation unit 102 uses the spectral reflectance of the printing medium as the base spectral reflectance R ₀ (λ) of the base, and the absorption coefficient K (λ) and scattering coefficient S (λ) of the ink 1000 region. The density gradation spectral reflectance R _im (λ) of the density gradation area of the halftone dot area of the ink 1000 (spot color ink or primary color ink) printed on the printing medium is obtained from the equation (1). .

Then, the extended Neugebauer primary color calculation unit 1081 calculates the spectral reflectance R _KM (λ) shown in the region 1005 printed above the ink region 1004 with respect to the ink 1000 having the spectral reflectance shown in the region 1002. . Here, the extended Neugebauer primary color calculation unit 1081 sets the spectral reflectance R _KM (λ) of the density gradation region of the halftone dot in the region of the ink 1000 as the base spectral reflectance R ₀ (λ) of the base, and shows the region 1003. absorption coefficient of the ink 1001 K and (lambda) and the scattering coefficient S (lambda), the thickness factor _{X m} of density gradation region, (1) by substituting in the expression to overlap the area of the ink 1000 in the region 1004 print The spectral reflectance R _KM (λ) of the density gradation region at the halftone dot of the region 1004 of the ink 1001 (spot color ink or primary color ink) is obtained.

As a result, the extended Neugebauer primary color calculation unit 1081 allows the density gradation area at the halftone dot of the background ink (spot color ink or primary color ink) and the density gradation of the halftone dot of the ink printed on the halftone dot of the background ink. In combination with the area, the spectral reflectance R _KM (λ) in the overlapping area of the density gradation area of the halftone dot of the upper ink (spot color ink or primary color ink) printed on the halftone dot of the underlying ink is As will be described later, the spectral reflectance R _KM in the printed portion in which the ink is overprinted is calculated by calculating all combinations of the density gradation area in the halftone dot of the base ink and the upper ink halftone dot. Find (λ). The extended Neugebauer primary color calculation unit 1081 writes and stores the obtained spectral reflectance R _KM (λ) in the Neugebauer primary color table of the temporary storage unit 125.

FIG. 6 is a flowchart showing a process for calculating the Neugebauer primary color by superposing special color inks. Further, as the ink to be superposed, not only the special color ink but also the primary color ink and the special color ink may be combined.
Step S201:
The user corresponds to the combination of the special color inks, inputs the printing order of the special color inks in each combination, and sets it for the color prediction system.

Step S202:
The extended Neugebauer primary color calculation unit 1081 reads the base spectral reflectance R ₀ (λ), which is the spectral reflectance of the print medium, from the measured spectral reflectance database 105.

Step S203:
The extended Neugebauer primary color calculation unit 1081 reads each of the scattering coefficient S (λ) and the absorption coefficient K (λ) of the spot color ink to be superimposed from the scattering absorption coefficient table of the temporary storage unit 125.

Step S204:
The extended Neugebauer primary color calculation unit 1081 stores the film thickness coefficient, which is the film thickness correction value input by the user, in the spectral reflectance, that is, stores the film thickness coefficient used in the equation (1) in the internal storage unit.

Step S205:
The extended Neugebauer primary color calculation unit 1081 calculates the spectral reflectance R _KM (λ) of a printed matter printed using the special color ink or the primary color ink as a base. At this time, the extended Neugebauer primary color calculation unit 1081 calculates all Neugebauer primary colors of the combinations of the respective film thickness coefficients in the special color ink to be superimposed. That is, the extended Neugebauer primary color calculation unit 1081 obtains the spectral reflectance R _KM (λ) of the special color ink printed on the base printing medium, and uses the obtained spectral reflectance R _KM (λ) as the new spectral reflectance of the base. And Then, the extended Neugebauer primary color calculation unit 1081 calculates the spectral reflectance when a new spot color ink is superimposed on the spot color ink having the obtained spectral reflectance R _KM (λ), and this is used as the spectral value of the Neugebauer primary color. The reflectance is R _KM (λ).
Here, when the measured value of the spectral reflectance is known in advance, such as when the background is solid of process ink, the spectral reflectance that is the measured value is not overlaid, but is calculated instead of calculating the spectral reflectance when printing on the medium. It may be used as the spectral reflectance of the base to be combined.
Then, the extended Neugebauer primary color calculation unit 1081 writes the calculated spectral reflectance R _KM (λ) in the Neugebauer primary color table of the temporary storage unit 125 and stores it.

Step S206:
The extended Neugebauer primary color calculation unit 1081 determines whether or not calculation of all Neugebauer primary colors of the combination of spot color inks has been completed.
At this time, the extended Neugebauer primary color calculation unit 1081 ends the process when calculation of all Neugebauer primary colors is completed. On the other hand, if the calculation of all Neugebauer primary colors has not been completed, the extended Neugebauer primary color calculation unit 1081 advances the process to step S207.

Step S207:
The extended Neugebauer primary color calculation unit 1081 changes the combination of the special color inks, sets the order of the special color inks to be superimposed as the order of the next special color ink combination, and advances the processing to step S205.

Returning to FIG. 2, the extended Neugebauer primary color appearance rate calculation unit 1082 uses the appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m from the density gradation appearance rate table database 104. Read (s).
Then, the expanded Neugebauer primary color appearance rate calculating unit 1082 appears at a halftone dot appearing at a halftone dot in the command halftone dot area ratio of the background ink, and at a halftone dot in the command halftone dot area ratio of the ink overlaid on the underlying ink. Appearance probability functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m (s) that are read from the density gradation appearance rate table database 104. )
Further, the extended Neugebauer primary color appearance rate calculation unit 1082 calculates the ratio of the appearance rate of the overlap between the density gradation region of the background ink and the density gradation region of the ink printed over the background ink.

FIG. 7 is a diagram for explaining the calculation of the ratio of the appearance ratio of the overlap between the density gradation area of the background ink and the density gradation area of the ink printed over the background ink (spot color ink or primary color ink). It is.
In FIG. 7, for simplicity, two types of ink to be superimposed are used, and two types of density gradation regions are also used. However, even if each of the overlapping ink and the density gradation area type is 3 or more, the overlap between the density gradation area of the underlying ink and the density gradation area of the ink printed on the underlying ink is overlapped. The ratio of the appearance rate can be calculated in the same manner as described below.

  FIG. 7A shows a case where there are two types of density gradation areas. The ink dot 1 command dot area ratio (set halftone) and the density scale appearing at the dot in the command dot area ratio. The correspondence relationship with the appearance rate of each of the core and fringe, which are the key regions, is shown. Also, ink # 2 has the same correspondence as ink # 1. Each of ink # 1 and ink # 2 is either a primary color ink or a special color ink. In each of ink # 1 and ink # 2, there are two types of density gradation areas, density gradation core area 1 and density gradation fringe area 2, and density gradation core area 1 has a film thickness of 100%. The density gradation fringe region 2 has a film thickness of 50%. Other inks have the same correspondence.

  FIG. 7B shows the overlapping of the density gradation core region 1 and the density gradation fringe region 2. In FIG. 7B, for example, ink # 1 is cyan (C), and ink # 2 is magenta (M). There are nine types of overlapping combinations of the density gradation core region 1 and the density gradation fringe region 2 from the region Q1 to the region Q9. The region Q1 is a region including only the cyan density gradation core region 1. The region Q2 is a region having only the cyan density gradation fringe region 2. The area Q3 is an area of only the magenta density gradation core area 1. The region Q4 is a region of only the magenta density gradation fringe region 2. The region Q5 is a region where the density gradation core regions 1 of cyan and magenta overlap each other. The area Q6 is an area where the magenta density gradation fringe area 2 and the cyan density gradation core area 1 overlap. The area Q7 is an area where the magenta density gradation core area 1 and the cyan density gradation fringe area 2 overlap. The region Q8 is a region where the density gradation fringe regions 2 of cyan and magenta overlap each other. The region Q9 is a region where neither cyan nor magenta ink exists.

  FIG. 8 is a table showing the calculation results of the appearance rates of the areas Q1 to Q9 in FIG. In FIG. 8, the primary color inks C (cyan) and M (magenta) are described, but the appearance rate is calculated in the same manner with special color inks. In this table, C is a cyan density gradation area, M is a magenta density gradation area, CM is an area where cyan and magenta density gradation areas overlap, and W is either cyan or magenta. The area where no ink exists is shown. In FIG. 8, the appearance rate α1 is the appearance rate of the cyan density gradation core region 1, and the appearance rate α2 is the appearance rate of the cyan density gradation fringe region 2. The appearance rate α0 is the sum of the appearance rate α1 and the appearance rate α2 (α0 = α1 + α2). The appearance rate β1 is the appearance rate of the magenta density gradation core region 1, and the appearance rate β2 is the appearance rate of the magenta density gradation fringe region 2. The appearance rate β0 is the sum of the appearance rate β1 and the appearance rate β2 (β0 = β1 + β2).

The primary appearance rate of the region Q1 and the region Q2 is α0 * (1-β0) obtained by multiplying the appearance rate α0 where cyan ink appears by the rate (1-β0) which is the rate at which magenta ink does not appear. , The appearance rate of the area of only cyan ink is shown. In the present embodiment, * indicates multiplication.
The primary appearance rate of the region Q3 and the region Q4 is β0 * (1-α0) obtained by multiplying the appearance rate β0 where magenta ink appears by the rate (1−α0) which is a rate where cyan ink does not appear. , Shows the appearance rate of the magenta ink-only area.

The primary appearance rate of the region Q5 to the region Q8 is α0 * β0, which is obtained by multiplying the appearance rate α0 where the cyan ink appears by the appearance rate β0 where the magenta ink appears, and the cyan ink and the magenta ink Shows the appearance rate of the overlapping area.
The single-order appearance rate of the area Q9 is (1-α0) * obtained by multiplying (1-α0), which is a rate at which cyan ink does not appear, by (1-β0), which is a rate at which magenta ink does not appear. (1−β0), which indicates the appearance rate of a region where neither cyan ink nor magenta ink exists.

The sub-appearance rate of the region Q1 indicates the appearance rate of only the density tone core region 1 of the halftone dot of cyan ink. The appearance rate α1 of the density tone core region 1 is represented by the density tone core region 1. Is a rate divided by the addition result of the appearance rate α1 and the appearance rate α2 of the density gradation fringe region 2.
The sub-appearance rate of the area Q2 indicates the appearance rate of only the density gradation fringe area 2 of the halftone dot of cyan ink, and the appearance rate α1 of the density gradation core area 1 is expressed as the density gradation core area 1. Is divided by the addition result of the appearance rate α1 and the appearance rate α2 of the density gradation fringe region 2, and the division result is subtracted from 1.

The sub-appearance rate of the region Q3 indicates the appearance rate of only the density gradation core region 1 of the magenta ink dot, and the appearance rate β1 of the density gradation core region 1 is set as the density gradation core region 1. Is a rate divided by the addition result of the appearance rate β1 and the appearance rate β2 of the density gradation fringe region 2.
The sub-appearance rate of the area Q4 indicates the appearance rate of only the density gradation fringe area 2 of the magenta ink dot, and the appearance ratio β1 of the density gradation core area 1 is represented by the density gradation core area 1. Is divided by the addition result of the appearance rate β1 and the appearance rate β2 of the density gradation fringe region 2, and the division result is subtracted from 1.

  The sub-appearance rate of the region Q5 indicates the appearance rate of the overlapping portion of the density gradation core region 1 of each of the ink dots of cyan and magenta, and the density gradation core region of the halftone dot of cyan ink 1 is divided by the addition result of the appearance rate α1 of the density gradation core region 1 and the appearance rate α2 of the density gradation fringe region 2 and the density gradation core region 1 of the magenta ink dot. Is the rate obtained by multiplying the appearance rate β1 by the rate obtained by dividing the appearance rate β1 of the density gradation core region 1 by the addition result of the appearance rate β2 of the density gradation fringe region 2.

  The sub-appearance rate of the region Q6 indicates the appearance rate of the overlapping portion of the density gradation core region 1 of the halftone dot of cyan ink and the density gradation fringe region 2 of the halftone dot of magenta ink. The ratio obtained by dividing the appearance rate α1 of the density gradation core region 1 of the halftone dot of the ink by the addition result of the appearance rate α1 of the density gradation core region 1 and the appearance rate α2 of the density gradation fringe region 2, and magenta ink The rate obtained by subtracting from 1 the rate obtained by dividing the appearance rate β1 of the density gradation core region 1 of the halftone dot by the addition result of the appearance rate β1 of the density gradation core region 1 and the appearance rate β2 of the density gradation fringe region 2 Is the rate of the result of multiplying

  The sub-appearance rate of the region Q7 indicates the appearance rate of the overlapping portion of the density gradation fringe region 2 of the cyan ink halftone dot and the density gradation core region 1 of the magenta ink halftone dot. The rate obtained by dividing the appearance rate α1 of the density gradation core region 1 of the ink halftone dot by the addition result of the appearance rate α1 of the density gradation core region 1 and the appearance rate α2 of the density gradation fringe region 2 is subtracted from 1. The rate obtained by dividing the appearance rate β1 of the density gradation core region 1 of the halftone dot of the magenta ink by the addition result of the appearance rate β1 of the density gradation core region 1 and the appearance rate β2 of the density gradation fringe region 2 Is the rate of the result of multiplying

  The sub-appearance rate of the area Q8 indicates the appearance rate of the overlapping portion of the density gradation fringe area 2 of the halftone dot of cyan ink and the density gradation fringe area 2 of the halftone dot of magenta ink. The rate obtained by dividing the appearance rate α1 of the density gradation core region 1 of the ink halftone dot by the addition result of the appearance rate α1 of the density gradation core region 1 and the appearance rate α2 of the density gradation fringe region 2 is subtracted from 1. The rate obtained by dividing the appearance rate β1 of the density gradation core region 1 of the halftone dot of the magenta ink by the addition result of the appearance rate β1 of the density gradation core region 1 and the appearance rate β2 of the density gradation fringe region 2 Is a rate obtained by multiplying the rate obtained by subtracting 1 from 1.

  The sub-appearance rate of the region Q9 indicates the appearance rate of a region where neither cyan ink nor magenta ink exists, and is “1”.

As described above, the expression of the appearance rate used for overlaying the inks to be used is set in advance and written and stored in the density gradation appearance rate table database 104 as a table shown in FIG.
Returning to FIG. 2, the expanded Neugebauer primary color appearance rate calculation unit 1082 determines the density gradation appearance rate table database 104 by combining each of the type of ink to be superimposed and the command halftone dot area ratio indicating the halftone dot of the superimposed ink. 8 is read.
Further, the extended Neugebauer primary color appearance rate calculating unit 1082 uses the density tone appearance rate table database 104 to display the appearance rates α1, α2, and the density tone fringe regions 2 of cyan and magenta, respectively. β1 and β2 are read.

The extended Neugebauer primary color calculation unit 1081 generates a magenta that appears at a specified halftone dot area ratio with the spectral reflectance of cyan as the background spectral reflectance R ₀ (λ) of the background when cyan is the background and the magenta is superimposed on cyan. The spectral reflectance R _KM (λ) of the density gradation area in the overlapping portion is calculated by the equation (1) using the film thickness of the density gradation area. For example, when the extended Neugebauer primary color calculation unit 1081 obtains the spectral reflectance R _KM (λ) in the region Q5, the density gradation spectral reflectance R _im (λ) at a film thickness of 100% of cyan ink on the print medium is calculated. As the base spectral reflectance R ₀ (λ) of the base, the spectral reflectance R _KM (λ) of the printed portion in the overlapping portion when the film thickness of 100% of magenta ink is overlapped is calculated.

Similarly, when the extended Neugebauer primary color calculation unit 1081 obtains the spectral reflectance R _KM (λ) in the region Q7, the density gradation spectral reflectance R _im (λ) at a thickness of 50% of the cyan ink on the printing medium. Is the base spectral reflectance R ₀ (λ) of the base, and the spectral reflectance R _KM (λ) when 100% of the magenta ink film thickness is overlapped is calculated. Similarly, spectral reflectance R _KM (λ) is calculated for all combinations of extended Neugebauer primaries.
Next, when the extended Neugebauer primary color appearance rate calculating unit 1082 calculates the extended Neugebauer primary color appearance rate of the region Q1, the primary appearance rate α0 * (1-β0) and the secondary appearance rate α1 / (α1 + α2). Is obtained by multiplying by. Further, when the extended Neugebauer primary color appearance rate calculating unit 1082 calculates the extended Neugebauer primary color appearance rate of the region Q2, the primary appearance rate α0 * (1-β0) and the secondary appearance rate {1-α1 / ( It is obtained by multiplying α1 + α2)}. Each of the region Q3 and the region Q4 can be obtained in the same manner as the region Q1 and the region Q2 described above only by changing cyan to magenta.
When the extended Neugebauer primary color appearance rate calculating unit 1082 calculates the extended Neugebauer primary color appearance rate of the region Q5, the primary appearance rate α0 * β0 and the secondary appearance rate {α1 / (α1 + α2)} * {β1 / ( It is obtained by multiplying by β1 + β2)}.
When the extended Neugebauer primary color appearance rate calculating unit 1082 calculates the extended Neugebauer primary color appearance rate in the region Q6, the primary appearance rate α0 * β0 and the secondary appearance rate {α1 / (α1 + α2)} * {1-β1. / (Β1 + β2)} is obtained by multiplication.
When the extended Neugebauer primary color appearance rate calculation unit 1082 calculates the extended Neugebauer primary color appearance rate of the region Q7, the primary appearance rate α0 * β0 and the secondary appearance rate {1-α1 / (α1 + α2)} * {β1 / (Β1 + β2)} is obtained by multiplication.
When the extended Neugebauer primary color appearance rate calculating unit 1082 calculates the extended Neugebauer primary color appearance rate of the region Q8, the primary appearance rate α0 * β0 and the secondary appearance rate {1-α1 / (α1 + α2)} * {1 It is obtained by multiplying by -β1 / (β1 + β2)}.
The extended Neugebauer primary color appearance rate calculation unit 1082 multiplies the primary appearance rate (1-α0) * (1-β0) by the secondary appearance rate 1 when calculating the extended Neugebauer primary color appearance rate of the region Q9. Ask for it.

Then, the spectral reflectance calculation unit 1083 multiplies the spectral reflectance of each of the extended Neugebauer primaries in the above-described region Q1 to region Q9 by the extended Neugebauer primary color appearance rate, and adds them for each wavelength.
The spectral reflectance calculation unit 1083 prints the first predicted spectral reflectance R _D1 (λ) of the printed portion when the magenta ink halftone dot is printed on the print medium on which the cyan ink halftone dot is printed. Is calculated.

Calculation of density gradation appearance rate based on spectral optical density Further, the density gradation spectral optical density calculation unit 202 obtains primary colors from the absorption coefficient / scattering coefficient database 106 according to the type of primary color ink supplied from the input unit 101. The absorption coefficient K (λ) and scattering coefficient S (λ) of the colored layer obtained from the printed portion where the ink is printed on the printing medium with a solid ink are read out. In addition, the density gradation spectral optical density calculation unit 202 determines the measurement spectrum for each halftone dot area rate according to the type of primary color ink and the type of print medium supplied from the input unit 101 from the measurement spectral reflectance database 105. Each of the reflectance Rs (λ) and the base spectral reflectance R ₀ (λ) of the print medium is read out.

Then, the density gradation spectral optical density calculation unit 202 reads the absorption coefficient K (λ) and scattering coefficient S (λ) of the read primary color ink, the background spectral reflectance R ₀ (λ) of the print medium, and the density gradation. of each of the film thickness coefficient X _m, already described (1) is substituted into (equation of Kubelka-Munk), as the spectral reflectance of the gray scale regions, the density gradation spectral reflectance R _{i1 (lambda)} , R _i2 (λ), R _i3 (λ),..., R _im (λ) are calculated.
Further, the density gradation spectral optical density calculation unit 202 calculates each of the obtained density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ),..., R _im (λ). The density gradation spectral optical densities OD _i1 (λ), OD _i2 (λ), OD _i3 (λ),..., OD _im (λ) are respectively converted by the following equation (5).

Also in density gradation spectroscopic concentration calculator 202, as with density gradation spectral reflectance calculating section 102, the thickness factor X _m of printed ink in (1) (wherein the Kubelka-Munk), printing This is used as a numerical value indicating the density gradation of the printed portion, based on the printed portion in which the primary color ink is solidly printed on the medium. That is, the film thickness coefficient _Xm is arbitrarily set. For example, the solid print portion having the thickest ink film thickness is set to 100%, the film thickness coefficient is set to 1, and the film thickness coefficient is set to 1. Divide into m corresponding to the number m of thickness steps. For example, if there are five stages of film thickness in the density gradation area indicated by the command halftone dot area ratio, m = 1, 2, 3, 4, 5 and the film thickness coefficient _Xm is the respective density scale. Corresponding to the thickness of the tone region, X ₁ = 1.0, X ₂ = 0.8, X ₃ = 0.6, X ₄ = 0.4, and X ₅ = 0.2.

The thickness factor X _m, as already mentioned, the underlying spectral reflectance R ₀ of the print medium _(lambda), and the absorption coefficient K (lambda), together with the scattering coefficient S (lambda), is the equation of Kubelka-Munk The density gradation spectral reflectances R _i1 (λ), R _i2 (λ), and R _i3 are substituted into the equation (1) and are used as the spectral reflectances of the density gradation areas included in the halftone dots of the respective command halftone area ratios. Each of (λ),..., R _im (λ) is calculated. Then, each of the density gradation spectral reflectances R _i1 (λ), R _i2 (λ), R _i3 (λ),..., R _im (λ) is expressed by a density gradation spectral optical density OD according to the equation (5). _i1 (λ), OD _i2 (λ), OD _i3 (λ),..., OD _im (λ), respectively. The density gradation spectral optical densities OD _i1 (λ), OD _i2 (λ), OD _i3 (λ),..., OD _im (λ) are used for a plurality of density levels constituting a halftone dot used in a calculation model described later. It is used as the spectroscopic optical density of each tone area.

The density gradation appearance rate calculation unit 203 receives the density gradation spectral optical density OD _i1 (λ), OD _i2 (λ), OD _i3 (λ),... OD _im ( Read each of λ). Also, the density gradation appearance rate calculation unit 203 reads each of the measured spectral reflectances Rs (λ) for each command halftone dot area rate from the measured spectral reflectance database 105.
Then, the density gradation appearance rate calculating unit 203 converts each of the measured spectral reflectances Rs (λ) into measured spectral optical densities ODs (λ) by using the equation (5).
Next, the density gradation appearance rate calculation unit 203 performs density gradation spectral optical densities OD _i1 (λ), OD _i2 (λ), and OD _i3 (λ) with respect to the following equation (6) (calculation model). ,..., OD _im (λ) is substituted, and the calculated spectral optical density OD ′ (s, λ) is calculated by the processing described later.

  Here, the density gradation appearance rate calculation unit 203 changes the numerical value of the appearance ratio (area ratio of the density gradation area of each density gradation constituting the halftone dot in the printed portion of the paper) in the equation (6). At the same time, the calculated spectral optical density OD ′ (s, λ) is calculated. The density gradation appearance rate calculation unit 203 then calculates the mean square error between each of the calculated spectral optical densities OD ′ (s, λ) calculated in the following equation (7) and the measured spectral optical density ODs (λ). RMSE is determined in a predetermined wavelength range for each command halftone dot area ratio. The density gradation appearance rate calculation unit 203 obtains the appearance rate of each density gradation region where the mean square error between the calculated spectral optical density OD ′ (s, λ) and the measured spectral optical density ODs (λ) is the smallest. . Here, s is a command halftone dot area ratio.

  In the above equation (7), the density gradation appearance rate calculation unit 203 calculates the calculated spectral optical density OD ′ (s, λ) and the measured spectral optical density ODs (λ by the step size obtained by dividing the wavelength λ from 380 nm to 730 nm by n. ) And the mean square error RMSE obtained by adding the square of the error to each wavelength λ is obtained for each command halftone dot area ratio.

Then, the density gradation appearance rate calculation unit 203 determines the appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s), and the like of each density gradation region based on the appearance rates of the density gradation regions. ..., a _m (s) is obtained. Here, the density gradation appearance rate calculation unit 203 uses the appearance rate obtained for each density gradation region to fit the appearance rate to a quadratic function of the command halftone dot area rate s, and the like. A function may be obtained. Density gradation appearance ratio calculating section 203, the incidence of the density gradation area determined function _{a 1 (s), a 2} (s), a 3 (s), ..., a m a (s), concentration Floor It is written and stored in the key appearance rate table database 204. As for the appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m (s), the calculation model of the equation (6) is the same as the description in the spectral reflectance prediction unit 108. 3 is a function for determining the appearance rate of the density gradation region used in FIG. 3, and is used to model the structure of halftone dots by gravure printing as described in FIG.

As described above, the density gradation appearance rate calculation unit 203 uses the calculation model of the equation (6), and the density included in the halftone dots in the print portion where the ink (primary color ink) based on the command halftone area ratio is printed. For each gradation, density gradation spectral optical density OD _im (λ) and density gradation appearance rate function a ₁ (s), a ₂ (s), a ₃ (s) _,. The spectral optical density of the printed portion of the command halftone dot area ratio is calculated by adding the results obtained by multiplying (s).

In addition, the density gradation appearance rate calculation unit 203 uses the appearance rate function a _m (s) indicating the appearance rate of each density gradation region in the calculated halftone dot area ratio of the obtained density gradation region as the density gradation appearance rate. The table database 204 is written and stored in correspondence with the density gradation optical density of the density gradation region. Similarly, the density gradation appearance rate calculation unit 203 also applies to each of the other primary color inks, an appearance rate function a _m indicating the appearance rate of each density gradation region in the command halftone dot area ratio of the density gradation region. (S) is written and stored in the density gradation appearance rate table database 204.

Further, in the case of spot color ink generated by mixing primary color inks at a predetermined ratio, the above-described appearance rate function a _m (s) of the density tone region of the primary color ink is read from the density tone appearance rate table database 204 and used. . Here, the appearance rate function a _m (s) of any primary color ink to be mixed with the special color ink may be used, and the appearance rate function a _m (s) of each primary color ink to be mixed is determined according to the blending rate. You may use it in combination.
In the case of this special color ink, the scattering coefficient S _t (λ) and the absorption coefficient of the special color ink in the already described equation (4) according to the ratio of the primary color ink to be mixed, as described in the spectral reflectance prediction unit 108. K _t (λ) is calculated.

In the above equation (4), each of the coefficient α and the coefficient β is a coefficient indicating a mixing ratio of the primary color ink # 1 and the primary color ink # 2. The absorption coefficient K ₁ (λ) of the primary color ink # 1 is multiplied by the coefficient α, the absorption coefficient K ₂ of the primary color ink # 2 is multiplied by the coefficient β, and the sum is obtained as the absorption coefficient K of the special color ink. _t (λ). Similarly, the scattering coefficient S ₁ (λ) of the primary color ink # 1 is multiplied by a coefficient α, the scattering coefficient S ₂ (λ) of the primary color ink # 2 is multiplied by a coefficient β, and the added numerical value is The scattering coefficient S _t (λ) of the special color ink is used.
From the absorption coefficient / scattering coefficient database 106, the density gradation spectral optical density calculating unit 202 calculates the scattering coefficients S1 (λ) and S2 (λ) of the primary color ink # 1 and the primary color ink # 2 constituting the special color ink. And the absorption coefficients K1 (λ) and K2 (λ) are read out. Further, the density gradation spectral optical density calculation unit 102 </ b> A reads the base spectral reflectance R 0 (λ) of the print medium from the measured spectral reflectance database 105.
Next, the density gradation spectral optical density calculation unit 202 calculates the calculated scattering coefficient St (λ) and absorption coefficient Kt (λ) of the special color ink, the background spectral reflectance R0 (λ) of the print medium, and the density gradation. Are substituted into the above equation (1), and the density gradation spectral reflectances Ri1 (λ), Ri2 (λ), Ri3 (λ) are obtained as spectral reflectances in the density gradation region. ,... Rim (λ) is calculated.
The density gradation spectral optical density calculation unit 202 calculates the calculated density gradation spectral reflectance Ri1 (λ),
Each of Ri2 (λ), Ri3 (λ),..., Rim (λ) is expressed by the equation (5), and the density gradation optical densities ODi1 (λ), ODi2 (λ), ODi3 ( λ), NO, ODi
Each is converted to m (λ).

Operation of Spectral Optical Density Prediction Unit 111 Next, the spectroscopic optical density prediction unit 111 includes an extended Neugebauer primary color calculation unit 1111, an extended Neugebauer primary color appearance rate calculation unit 1112, a spectral optical density calculation unit 1113, and a spectral reflectance calculation unit 1114. I have.
The extended Neugebauer primary color calculation unit 1111 determines ink (primary color ink or special color ink) to be a base and ink to be printed on the surface of the base in accordance with the order of colors to be superimposed. Further, the extended Neugebauer primary color calculation unit 1111 reads from the input unit 101 the command halftone dot area ratio of each ink to be superimposed.

The extended Neugebauer primary color calculation unit 1111 reads the scattering coefficient S (λ) and the absorption coefficient K (λ) of the ink (primary color ink or special color ink) printed on the underlying ink.
Next, the extended Neugebauer primary color calculation unit 1111 applies the density gradation spectral reflectance R _im (λ) of the background ink to the formula (1) and the background ink as already described in FIG. and scattering coefficient of the ink to be printed S (lambda) and the absorption coefficient K (lambda), by substituting each of a thickness factor X _m of the density gradation region, the concentration of the halftone dots is printed on the ink base The gradation spectral reflectance R _im (λ) is calculated.

Here, the extended Neugebauer primary color calculation unit 1111 calculates the density gradation spectral reflectance R _im (λ) of the halftone dot of the ink printed on the above-described halftone dot of the background ink. This is performed in all the combinations of the overlapping portions of the density gradation area in FIG. 5 and the density gradation area of the halftone dot of the ink printed on the halftone dot of the base ink. Then, the extended Neugebauer primary color calculation unit 1111 calculates the density gradation spectral reflectance R _im (λ) of the ink printed on the halftone dot of the obtained background ink by the expression (5). Convert to density OD _im (λ). The extended Neugebauer primary color calculation unit 1111 writes and stores the obtained density gradation spectral optical density OD _im (λ) in the Neugebauer primary color table of the temporary storage unit 125.

  Returning to FIG. 2, the extended Neugebauer primary color appearance rate calculation unit 1112 calculates the density gradation area of the background ink and the density gradation area of the ink printed over the background ink, as in the description of FIG. 7. The ratio of the overlap appearance rate is calculated.

Further, as described in the spectral reflectance prediction unit 108, the expression of the appearance rate used for superimposing the inks to be used (primary color ink or spot color ink) is a density gradation appearance rate table as the appearance rate table shown in FIG. It is written and stored in the database 204.
The extended Neugebauer primary color appearance rate calculation unit 1112 stores the table of FIG. 8 in the density gradation appearance rate table database 204 based on the combination of the type of ink to be superimposed and the command halftone dot area ratio indicating the halftone dot of the superimposed ink. The expression of is read.
Further, the extended Neugebauer primary color appearance rate calculating unit 1112 uses the density tone appearance rate table database 204 to display the appearance rates α1, α2, and the density tone fringe regions 2 of cyan and magenta, respectively. β1 and β2 are read.

Further, the extended Neugebauer primary color calculation unit 1111 appears with the command halftone dot area ratio, assuming that cyan is the background and magenta is superimposed on cyan, and that the spectral reflectance of cyan is the background spectral reflectance R ₀ (λ) of the background. The spectral reflectance R _KM (λ) of the density gradation area in the overlapping portion is calculated by the equation (1) using the film thickness of the density gradation area of the magenta. For example, when the extended Neugebauer primary color calculation unit 1111 obtains the spectral reflectance R _KM (λ) in the region Q5, the density gradation spectral reflectance R _im (λ) at 100% of the cyan ink film thickness on the printing medium is obtained. As the base spectral reflectance R ₀ (λ) of the base, the spectral reflectance R _KM (λ) of the printed portion in the overlapping portion when 100% of the magenta ink film thickness is superimposed on the base is calculated. Then, the extended Neugebauer primary color calculation unit 1111 converts the calculated spectral reflectance R _KM (λ) into a spectral optical density OD _KM (λ) by the equation (5).

Similarly, when the extended Neugebauer primary color calculation unit 1111 obtains the spectral reflectance R _KM (λ) in the region Q7, the density gradation spectral reflectance R _im (λ) at a film thickness of 50% of the cyan ink on the printing medium. Is the base spectral reflectance R ₀ (λ) of the base, and the spectral reflectance R _KM (λ) when 100% of the magenta ink film thickness is overlapped is calculated. Then, the extended Neugebauer primary color calculation unit 1111 converts the calculated spectral reflectance R _KM (λ) into a spectral optical density OD _KM (λ) by the equation (5). Similarly, the spectral optical density OD _KM (λ) is calculated for all combinations of extended Neugebauer primaries.
The extended Neugebauer primary color appearance rate calculation unit 1112 multiplies the primary appearance rate α0 * (1-β0) by the secondary appearance rate α1 / (α1 + α2) when calculating the extended Neugebauer primary color appearance rate of the region Q1. Ask for it. Further, when the extended Neugebauer primary color appearance rate calculation unit 1112 calculates the extended Neugebauer primary color appearance rate of the region Q2, the primary appearance rate α0 * (1-β0) and the secondary appearance rate {1-α1 / ( It is obtained by multiplying α1 + α2)}. Each of the region Q3 and the region Q4 can be obtained in the same manner as the region Q1 and the region Q2 described above only by changing cyan to magenta.
When the extended Neugebauer primary color appearance rate calculation unit 1112 calculates the extended Neugebauer primary color appearance rate in the region Q5, the primary appearance rate α0 * β0 and the secondary appearance rate {α1 / (α1 + α2)} * {β1 / ( It is obtained by multiplying by β1 + β2)}.
When the extended Neugebauer primary color appearance rate calculating unit 1112 calculates the extended Neugebauer primary color appearance rate of the region Q6, the primary appearance rate α0 * β0 and the secondary appearance rate {α1 / (α1 + α2)} * {1-β1 / (Β1 + β2)} is obtained by multiplication.
When the extended Neugebauer primary color appearance rate calculating unit 1112 calculates the extended Neugebauer primary color appearance rate in the region Q7, the primary appearance rate α0 * β0 and the secondary appearance rate {1-α1 / (α1 + α2)} * {β1 / (Β1 + β2)} is obtained by multiplication.
When the extended Neugebauer primary color appearance rate calculating unit 1112 calculates the extended Neugebauer primary color appearance rate of the region Q8, the primary appearance rate α0 * β0 and the secondary appearance rate {1-α1 / (α1 + α2)} * {1 It is obtained by multiplying by -β1 / (β1 + β2)}.
The extended Neugebauer primary color appearance rate calculation unit 1112 multiplies the primary appearance rate (1-α0) * (1-β0) by the secondary appearance rate 1 when calculating the extended Neugebauer primary color appearance rate of the region Q9. Ask for it.
Then, the spectral optical density calculation unit 1113 multiplies the optical density of each of the extended Neugebauer primary colors in the above-described areas Q1 to Q9 by the extended Neugebauer primary color appearance rate.
The spectral optical density calculation unit 1113 calculates the predicted optical density OD (λ) of the printed portion when the magenta ink halftone dot is printed on the print medium on which the cyan ink halftone dot is printed.

Then, the spectral optical density calculation unit 1113 multiplies the spectral optical density of each of the extended Neugebauer primaries in the above-described region Q1 to region Q9 by the extended Neugebauer primary color appearance rate, and adds them for each wavelength.
The spectral optical density calculation unit 1113 calculates the predicted spectral optical density OD _D (λ) of the printed part when printing the magenta ink halftone dot on the print medium on which the cyan ink halftone dot is printed. To do.

The spectral reflectance calculation unit 1114 converts the predicted spectral optical density OD _D (λ) calculated by the spectral optical density calculation unit 1113 into the second predicted spectral reflectance R _D2 (λ) using the following equation (8). To do.

Operation of Mixed Prediction Unit 114 The mixed prediction unit 114 reads, from the prediction parameter database 126, the weighting coefficient w by which the first predicted spectral reflectance R _D1 (λ) and the second predicted spectral reflectance R _D2 (λ) are multiplied. . For example, the mixed prediction unit 114 adds wR _D1 (λ) and (1-w) R _D2 (λ) to obtain the integrated predicted spectral reflectance R _D (λ). Then, the mixed prediction unit 114 outputs the integrated predicted spectral reflectance R _D (λ) to the color profile generation unit 13 as the predicted spectral reflectance R (λ).

<Generation of color profile>
Then, the color profile generation unit 13 determines an observation light source based on the predicted spectral reflectance R (λ), calculates tristimulus values XYZ, CIELAB values, and the like, and creates a color prediction table for predicting reproduced colors To do. That is, the color profile generation unit 13 reproduces the reproduction color that is predicted based on the information of the input data (CMY value in this embodiment) that is the object of the color prediction process and the predicted spectral reflectance R (λ). A color prediction table is created as a color profile that associates color information. In this embodiment, the color profile generation unit 13 creates this color prediction table in a known ICC (International Color Consortium) profile format, and writes and stores it in the storage unit 18.

  FIG. 9 is a flowchart for explaining an operation example of color profile generation processing by the color prediction model generation unit 12 and the color profile generation unit 13 in the present embodiment.

Step S401:
The extended Neugebauer primary color appearance rate calculating unit 1082 reads the spectral reflectance R _KM (λ) of the Neugebauer primary color of the spot color ink in the overlapping region from the Neugebauer primary color table of the temporary storage unit 125.
Similarly, the extended Neugebauer primary color appearance rate calculation unit 1112 reads the spectral optical density OD _KM (λ) of the Neugebauer primary color of the spot color ink in the overlapping region from the Neugebauer primary color table of the temporary storage unit 125.

Step S402:
The mixed prediction unit 114 integrates the first predicted spectral reflectance R _D1 (λ) predicted by the spectral reflectance prediction unit 108 and the second predicted spectral reflectance R _D2 (λ) predicted by the spectral optical density prediction unit 111. In this case, the weighting coefficient w by which each of the first predicted spectral reflectance R _D1 (λ) and the second predicted spectral reflectance R _D2 (λ) is multiplied is read from the predicted parameter database 126.

Step S403:
Next, the expanded Neugebauer primary color appearance rate calculation unit 1082 extracts an uncalculated command halftone dot area rate in a matrix of command halftone dot area rates of ink to be superimposed in the color prediction table in the temporary storage unit 125.
Then, the extended Neugebauer primary color appearance rate calculation unit 1082 sets a combination of the extracted command halftone dot area rates as a calculation target. The processing described above may be configured to be performed by the extended Neugebauer primary color appearance rate calculation unit 1112.

Step S404:
The spectral reflectance prediction unit 108 calculates the first predicted spectral reflectance R _D1 (λ) based on the combination of the command halftone dot area ratios.
The spectroscopic optical density prediction unit 111 calculates the second predicted spectral reflectance R _D2 (λ) based on the combination of the command dot area ratios.

Further, the mixed prediction unit 114 adds the weight coefficient w and (1-w) read out in step S402 to the first predicted spectral reflectance R _D1 (λ) and the second predicted spectral reflectance R _D2 (λ), By adding wR _D1 (λ) and (1-w) R _D2 (λ), an integrated predicted spectral reflectance R _D (λ) is obtained. Further, the colorimetric value is calculated by setting the spectral distribution of the observation light source and the standard observer for the calculated integrated predicted spectral reflectance R _D (λ).

Step S405:
Then, the mixture prediction unit 114 writes the calculated colorimetric value in the color prediction table of the storage unit 18 so as to correspond to the combination of the command halftone dot area ratios of the superposed ink (spot color ink or primary color ink).

Step S406:
The extended Neugebauer primary color appearance rate calculation unit 1082 determines whether or not the calculation of the integrated predicted spectral reflectance R _D (λ) of all combinations of command halftone dot area rates in the color prediction table of the storage unit 18 has been completed. .
Then, the extended Neugebauer primary color appearance rate calculation unit 1082 advances the process to step S407 when the calculation of the integrated predicted spectral reflectance R _D (λ) for all combinations of the command halftone dot area rates is completed. On the other hand, the extended Neugebauer primary color appearance rate calculation unit 1082 advances the process to step S403 when the calculation of the integrated predicted spectral reflectance R _D (λ) of all combinations of the command halftone dot area rates has not been completed. The processing described above may be configured to be performed by the extended Neugebauer primary color appearance rate calculation unit 1112.

Step S407:
The color profile generation unit 13 reads the data of the color prediction table in the storage unit 18, converts it into a known ICC profile format, and writes and stores the converted color prediction profile data in the storage unit 18.

As described above, according to the present embodiment, the absorption characteristics and scattering characteristics of the spot color ink are estimated from the primary color ink, the spectral reflectance of the spot color ink is calculated, and the spectrum of the overlapping area when the spot color ink is overprinted is calculated. The reflectance can be determined.
For this reason, according to the present embodiment, the color prediction of the reproduced color in the printed matter in which the special color ink is overprinted in the printing such as gravure printing having both the area modulation gradation expression and the density modulation gradation expression is performed. It can be easily performed with high accuracy.

Further, according to the present embodiment, the spectral reflectance of the extended Neugebauer primary color, the first predicted spectral reflectance R _D1 (λ) calculated from the appearance rate, the spectral optical density of the extended Neugebauer primary color, and the appearance rate thereof. Since the calculated second predicted spectral reflectance R _D2 (λ) is mixed with the weight coefficient w obtained in advance, the mixed predicted spectral reflectance R _W (λ is calculated as the predicted spectral reflectance closer to the actually measured spectral reflectance. ) Can be obtained as the predicted spectral reflectance R (λ).

<Description of the operation of the print color adjustment system>
FIG. 10 is a flowchart for explaining an operation example of adjustment processing in which the color printed by a printing device (for example, an ink jet printer) is similar to the color of a printed matter of a printing press by the printing color adjustment system according to the present embodiment.
Step S501:
The user measures the color of the color patch for the solid printing of the ink used when the printing machine prints the printed matter, and obtains the colorimetric value of each ink. Then, the user inputs each measured colorimetric value of the measured ink to the print color adjustment system 1 from an input means (keyboard, touch panel, etc.).
In addition, the user inputs image data (data on the command halftone dot area ratio of each pixel) of the printed material plate from the external device to the print color adjustment system 1.

Step S502:
The input control unit 11 outputs the colorimetric value supplied from the input unit to the color prediction model generation unit 12. Further, the input control unit 11 writes and stores the image data of the printed matter supplied from the input unit in the storage unit 18.
Then, as already described, the color prediction model generation unit 12 generates a color prediction model (color prediction table) and writes the generated color prediction model in the storage unit 18 for storage.

Step S503:
The color profile generation unit 13 refers to the color prediction model (color prediction table) in the storage unit 18 and calculates each predicted spectral reflectance R (λ) corresponding to each combination of the command halftone dot area ratios of ink. The data is converted into a known ICC profile format, and the converted color profile (color prediction profile) data is written and stored in the storage unit 18.

Step S504:
The adjustment control unit 14 displays, on the display screen of the display unit 16, an image for extracting a partial image as a reference image for evaluating the color of the printed matter printed by the printing device from the image in the image data. This reference image is a partial image of a portion including a color to be expressed particularly in the image data image.
Then, the adjustment control unit 14 cuts out the partial image region selected by the user from the image data as the reference image in the image data image displayed on the display screen of the display unit 16.

Step S505:
The control value generation unit 15 predicts a combination of the command halftone dot area ratios of the respective inks in each pixel of the reference image cut out from the image data of the printed matter by the adjustment control unit 14 with reference to the color profile of the storage unit 18. Convert to colorimetric values.
Further, the control value generation unit 15 refers to the device color profile of the printing device in the storage unit 18, converts the predicted colorimetric value of each pixel of the reference image into the control value of the printing device, and writes it to the storage unit 18. Remember me.
Then, the print data output unit 17 reads the control value of each pixel of the reference image from the storage unit 18, and outputs the control value for printing the printed material of the read reference image to the printing device.

Step S506:
Accordingly, the user observes and compares the colors of the printed material of the reference image printed by the printing device and the region corresponding to the reference image in the printed material of the printing press. Then, the color of the printed material of the reference image printed by the printing device is within the allowable range of the color of the area corresponding to the reference image in the printed material of the printing press (that is, matches the color). Is determined).

Step S507:
If the user determines that the color of the printed material of the reference image printed by the printing device matches the color of the area corresponding to the reference image in the printed material of the printing machine, the process proceeds to step S508.
On the other hand, if it is determined that the color of the printed material of the reference image printed by the printing device does not match the color of the area corresponding to the reference image in the printed material of the printing press, the process proceeds to step S509.

Step S508:
In order to print a predetermined number of sheets, the user inputs the number of prints to the print color adjustment system 1 via the input unit.
Thereby, the control value generation unit 15 predicts the combination of the command halftone dot area ratios of the respective inks in all the pixels in the image data of the printed matter of the printing machine with reference to the color profile of the storage unit 18. The value is converted into a value, stored in the storage unit 18, and output to the print data output unit 17.
Then, the print data output unit 17 outputs the control value of the image data supplied from the control value generation unit 15 to the printing device, and prints the number of printed materials.

Step S509:
When the color difference between the printed material of the reference image of the printing device and the printed material of the printing machine exceeds an allowable range, the user performs a parameter changing process in the color prediction model. This change process will be described later in detail.
Then, the adjustment control unit 14 generates a multi-stage adjustment parameter for each of the adjustment target parameters based on the type of the adjustment target parameter input by the user from the input unit and the adjustment ratio, and the color prediction model The data is output to the generation unit 12 and a new color prediction model is generated.

Accordingly, the color prediction model generation unit 12 generates a color prediction model corresponding to each of a plurality of adjustment parameters in multiple stages. For example, when there are two types of parameters to be adjusted and these parameters are adjusted in five stages, the color prediction model generation unit 12 has 25 color prediction models corresponding to combinations of 5 × 5 = 25. Is generated.
Then, the color prediction model generation unit 12 writes and stores the generated color prediction model in the storage unit 18.

Step S510:
The color profile generation unit 13 refers to the adjusted color prediction model in the storage unit 18 and generates a color profile corresponding to each color prediction model of a combination of parameters to be adjusted.
Then, the color profile generation unit 13 writes and stores each of the generated color profiles in the storage unit 18.

Step S511:
The control value generation unit 15 combines the command halftone dot area ratio of each ink in each pixel of the reference image extracted from the image data of the printed matter by the adjustment control unit 14, and sets each color profile after adjustment in the storage unit 18. Are sequentially referred to and converted into expected colorimetric values for each color profile. That is, the control value generation unit 15 generates reference image data converted into the expected colorimetric values for each color profile.
Further, the control value generation unit 15 refers to the device color profile of the printing device in the storage unit 18, converts the predicted colorimetric value of each pixel in the data of each reference image into the control value of the printing device, and stores the storage unit 18. Write to and store. As a result, the control value generation unit 15 generates control value data for reference images having different numbers of color profiles.
Then, the print data output unit 17 reads the control value of each pixel of the reference image from the storage unit 18, and outputs the read control value of each reference image to the printing device.

As a result, the process proceeds to step S506, and the user observes and compares the colors of each of the printed materials of the plurality of reference images printed by the printing device and the areas corresponding to the reference images in the printed materials of the printing press. To do. Then, the user has any color of the printed material of the reference image printed by the printing device within the allowable range of the color of the area corresponding to the reference image in the printed material of the printing press (that is, , They match).
In step S507, if there is a reference image whose color matches the printed matter of the printing press, the process proceeds to step S508, and if there is no matching reference image, the process proceeds to step S509.

<Color prediction model parameter adjustment>
When the user compares the colors of the printed matter of the printing press and the printed matter of the printing device and determines that they do not match, the parameter of the color prediction model is adjusted as described above.
The parameters to be adjusted include the following types corresponding to items to be adjusted.

a. Parameter for adjusting the case of adjusting the concentration of the printing is a change in the numerical value of the thickness of coefficients X _m in the formula of Kubelka-Munk shown in equation (1). If it is desired to increase the color density of the ink to be adjusted, the film thickness coefficient _Xm is increased. On the other hand, if it is desired to reduce the color density of the ink to be adjusted, the film thickness coefficient _Xm is decreased. Adjustment control unit 14, when changing in multiple stages is varied in a predetermined ratio, for example, in the case of changing the dark, if the adjusting current thickness coefficients into five levels with respect to the thickness factor X _m 1.05, 1.10, 1.25, 1.20, 1.25, etc. are multiplied to generate a parameter for adjustment with a slight change. The adjustment control unit 14, if the change of thinning, if you adjust the current thickness coefficients into five stages, with respect to the thickness factor _{X m} 0.95,0.90,0.85,0 .80, 0.75, etc., are used as adjustment parameters that are slightly changed. The color prediction model generation unit 12 generates a color prediction model in which the color density of the ink to be adjusted is adjusted in multiple stages.
The ratio may be input by the user using the input means, or may be set in advance.

b. When adjusting the color value of printing If you want to change the color value of one of the inks on the print medium, the ink selected by the color measurement value of the solid printing of the ink used for the printed material is changed to another ink. When the user inputs an instruction to change this parameter, the spot color ink spectral reflectance calculation unit 121 has a colorimetric value close to that other than having already selected a colorimetric value ink (spot color ink) close to solid printing. A plurality are sequentially extracted from the approximate color database 128, and the extracted plurality are displayed on the display screen of the display unit 16. In order to change the color value of the ink in multiple stages, the user selects a multi-stage number of spot color inks from the displayed spot color inks.

  Thus, the adjustment control unit 14 changes the blending ratio (values of α and β) of the blended ink in the spot color ink in the equation (4) for each of the spot color inks selected. The spectral reflectance obtained by adjusting the absorption coefficient K (λ) and the scattering coefficient S (λ) is calculated for each blending ratio, and the predicted colorimetric value obtained from the spectral reflectance is used for printing the printed matter. A blending ratio that is the same as the color measurement value of the solid ink printing is selected. The color prediction model generation unit 12 generates a color prediction model using the selected spot color ink and the absorption coefficient K (λ) and scattering coefficient S (λ) of the spot color ink based on the blending ratio of the ink. As a result, the color prediction model generation unit 12 generates a color prediction model corresponding to a combination of a plurality of spot color inks selected by the user and the absorption coefficient K (λ) and scattering coefficient S (λ) of the spot color ink. .

c. When adjusting the gradation characteristics of printing In the function in each of the appearance rate functions a ₁ (s), a ₂ (s), a ₃ (s),..., A _m (s) in the following equation (9) The parameters are changed to adjust the shape and position of each appearance rate function shown in FIG.
This makes it possible to arbitrarily change the gradation characteristics at the density stage of each ink. The parameters in this function are changed in a plurality of stages, a table corresponding to FIG. 7 for a plurality of gradation characteristics is created, and a color prediction model corresponding to each table is generated.

d. When adjusting to the printing device's trapping state on the printing device When determining the density gradation spectral reflectance R _KM of the ink superimposed on the upper side in the configuration in which the ink is overlaid, using the Kubelka-Munk equation (1) The film thickness coefficient _Xm is changed. Changes to this thickness factor X _m are the same as those already described in the "case of adjusting the concentration of a. Print". Then, the color prediction model generation unit 12 adjusts the density of the color of the ink above the overlap to be adjusted in multiple stages, and generates a color prediction model in which the trapping state is changed.

e. When adjustment of misalignment of each plate in the printed material is adjusted for the printing device The adjustment control unit 14 reads out the image data of the plate stored in the storage unit 18 and synthesizes the respective plates to generate an image of the printed material. When data is generated, the plates are not overlapped with each other completely matched, but are overlapped with a predetermined shift amount (a slight shift). Thereby, the combination of the command halftone dot area ratio of each pixel differs depending on the overlap of the plates. A number of image data corresponding to this number is generated by a plurality of different shift amounts.
Then, the control value generation unit 15 converts the combination of the command halftone dot area ratios of the inks in the respective pixels of the image data of the plurality of printed materials into the expected colorimetric values with reference to the color profile of the storage unit 18. To do. The control value generation unit 15 refers to the device color profile of the printing device in the storage unit 18, converts the predicted colorimetric value of each pixel into the control value of the printing device, and writes and stores the control value in the storage unit 18.

f. When adjustment is performed on the printing device in accordance with the graininess of the printed matter, the adjustment control unit 14 performs a filter process for superimposing noise on the image data, for example, a filter process for superimposing Gaussian noise, thereby performing pixel processing on the image data. The command halftone dot area ratio is changed, and granular noise is superimposed on the image. A plurality of adjusted image data can be obtained by changing the shape of the noise to be superimposed in multiple stages.
Then, the control value generation unit 15 converts the combination of the command halftone dot area ratios of the inks in the respective pixels of the image data of the plurality of printed materials into the expected colorimetric values with reference to the color profile of the storage unit 18. To do. The control value generation unit 15 refers to the device color profile of the printing device in the storage unit 18, converts the predicted colorimetric value of each pixel into the control value of the printing device, and writes and stores the control value in the storage unit 18.

  According to this embodiment, as described above, a halftone dot printed matter that reproduces the color of an image by printing ink in a halftone dot shape on a printing medium by a technique such as gravure printing, screen printing, and offset printing on a printing press. When the same image data with the same color is printed with a simple printer (printing device) such as an inkjet printer or digital printer, printing is performed by adjusting the parameters of the color prediction model that models the dot shape By adjusting the color of the printed matter on the device, it is possible to adjust the color of the printed matter on the printing device corresponding to the ink unit on which the halftone printed matter is printed. When adjusting the printing corresponding to a predetermined ink of a dot printed matter, it does not affect the color of other inks other than this predetermined ink. The color of each of the adjustment of the adjustment object can be easily performed in Surimono.

In addition, according to the present embodiment, when a small amount of a printed matter printed by a commercial printing machine capable of printing in large quantities is desired, it is not a commercial printing machine that requires a small amount of printing, but an inkjet printer or digital printing. By using a simple printing machine such as a printing press, it becomes possible to print a printed matter similar to a printed matter printed by a commercial printer, and a small amount of printed matter can be added at low cost and in real time.
Further, according to the present embodiment, when there is not enough printed matter printed by a commercial printer capable of printing in large quantities, printed matter similar to the printed matter printed by a commercial printer can be obtained at low cost and in real time. Printing can be performed using a simple printing machine, and it is not necessary to have extra inventory in anticipation of being insufficient as in the prior art.

  Further, in the present embodiment, the absorption characteristics and scattering characteristics of the special color ink are estimated from the primary color ink, the spectral reflectance of the special color ink is calculated, and the spectral reflectance of the overprinted area of the special color ink of the printed matter is obtained, The color prediction model that estimates the colorimetric value of each pixel of the printed material is used, but any configuration may be used as long as the color prediction model can estimate the colorimetric value from the combination of the command halftone dot area ratios. .

Note that a program for realizing the function of the printing color adjustment system of FIG. 1 in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into the computer system and executed. Thus, the color adjustment of the printed matter printed by the printing device may be controlled. Here, the “computer system” includes an OS and hardware such as peripheral devices.
The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Print color adjustment system 11 ... Input control part 12 ... Color prediction model production | generation part 13 ... Color profile production | generation part 14 ... Adjustment control part 15 ... Control value production | generation part 16 ... Display part 17 ... Print data output part 18 ... Memory | storage part 101 ... Input unit 102 ... Density gradation spectral reflectance calculation unit 103,203 ... Density gradation appearance rate calculation unit 104,204 ... Density gradation appearance rate table database 105 ... Measured spectral reflectance database 106 ... Absorption coefficient / scattering coefficient database DESCRIPTION OF SYMBOLS 107 ... Absorption coefficient / scattering coefficient calculation part 108 ... Spectral reflectance prediction part 110 ... Output part 111 ... Spectral optical density prediction part 112 ... Weight coefficient calculation part 113 ... Weight coefficient database 114 ... Mixing prediction part 121 ... Special color ink spectral reflectance Calculation unit 122 ... Special color ink blending ratio determination unit 123 ... Special color ink density gradation appearance rate calculation unit 125 ... Temporary storage unit 126 ... Prediction parameter database 128 ... Approximate color database 202 ... Density gradation spectral optical density calculation unit 1081, 1111 ... Extended Neugebauer primary color calculation unit 1082, 1112 ... Extended Neugebauer primary color appearance rate calculation unit 1083, 1114 ... Spectral reflectance Calculation unit 1113 ... Spectral optical density calculation unit

Claims (10)

Prediction of the color of the printed material printed from the area modulation gradation and density modulation gradation command values from the color measurement values of the solid printing of each ink used for the printed matter printed with the area modulation gradation and density modulation gradation A color profile generation unit that generates a color profile of a first printing press that prints the printed matter using a print color prediction model for obtaining a value;
Based on the color profile, a predicted value of a color corresponding to the command value of each dot in the image data of the printed material is obtained, the predicted value is used as color information of the color of the printed material, and the color information is the color profile of the second printing machine. A printing color adjustment system comprising: a printing control unit that converts the control value into a control value and outputs the control value to the second printing press. Adjusting parameters used for calculation of predicted color prediction in the print color prediction model, generating a plurality of print color prediction models corresponding to the parameters adjusted in a plurality of stages, and a plurality of the color profiles An adjustment control unit for generating
The print color adjustment system according to claim 1, wherein the print control unit outputs each control value obtained from each of the color profiles to the second printing machine. The print color prediction model uses the absorption coefficient and scattering coefficient of each solid print of ink to predict the predicted value when the ink is overprinted, and the spectral reflectance at each dot of the printed matter is determined by Kubelka. The printing color adjustment system according to claim 2, further comprising a process to be calculated using a Munch equation. The printing color adjustment system according to claim 3, wherein the thickness of the ink for solid printing in the Kubelka-Munk equation is used as the parameter. The printing color adjustment system according to claim 3 or 4, wherein the color value of the ink for solid printing in the Kubelka-Munk equation is used as the parameter. The print color adjustment system according to any one of claims 3 to 5, wherein a gradation characteristic of the predicted color in a halftone of the command value is used as the parameter. When changing the predicted color when the ink is overprinted, the thickness of the ink for solid printing in the Kubelka-Munk equation for obtaining the spectral reflectance of the ink to be overlaid on another ink is used as the parameter. The printing color adjustment system according to any one of claims 3 to 6, wherein When the adjustment control unit adjusts the plate deviation of the printed matter, the position of each of the ink plates of the printed matter is shifted,
The printing according to any one of claims 2 to 7, wherein the print control unit obtains a predicted value of a color of each dot of the printed matter in the overlap of the plates whose positions are shifted. Color adjustment system. The print color adjustment system according to any one of claims 2 to 8, wherein the adjustment control unit superimposes noise on the predicted value of the image data. A colorimetric process for measuring the colorimetric value of each solid print of ink used for printed matter printed with area modulation gradation and density modulation gradation;
A color profile of a first printing machine that prints the printed matter using a print color prediction model that obtains a predicted value of the color of the printed matter to be printed from a command value of area modulation gradation or density modulation gradation from the colorimetric value. The process of generating
Based on the color profile, a predicted value of a color corresponding to the command value of each dot in the image data of the printed material is obtained, the predicted value is used as color information of the color of the printed material, and the color information is the color profile of the second printing machine. Converting the control value into a control value and outputting to the second printing press;
Comparing the color of the printed matter printed by the first printing press with the color of the printed matter printed by the second printing press and selecting a parameter that needs to be adjusted in the printing color prediction model;
Changing the parameters in multiple stages, generating a plurality of print color prediction models, and generating each of the color profiles corresponding to each of the print color prediction models;
And a step of causing the second printing machine to print the image data according to control values corresponding to color information obtained from each of the color profiles.

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