JP2013005070A - Image processing device, printer, image processing method, method of manufacturing printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of image processing of image data.SOLUTION: The image processing device performs image processing on image data to be output to a printer that uses special gloss ink for printing, as print image data. The image data includes: hue information that is information on hue of an image based on spectral reflectance for a plurality of angles; and gloss degree information that is information on a degree of gloss of the image based on the spectral reflectance for the plurality of angles. The image processing device includes a specifying unit that specifies an ink amount set of ink to be used by the printer for printing, on the basis of the input hue information and the gloss degree information of the image data. The hue information and the gloss degree information to be used by the specifying unit for specification are calculated on the basis of a product of a non-gloss multi-angle spectral reflectance which is a multi-angle spectral reflectance of the image formed by combining inks of the printer other than the special gloss ink, and a gloss multi-angle spectral reflectance that is a multi-angle spectral reflectance of the image formed by the special gloss ink.

Description

  The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus that performs image processing on image data representing an image to be printed and outputs the image data to a printing apparatus, and a printing technique related thereto.

  Conventionally, there has been a demand for accurately reproducing special gloss such as metallic luster and gloss of a print object in a printed image. For example, Patent Document 1 discloses a technique in which the color and glossiness of a printing object having special gloss are recorded as image data as separate parameters and reflected in a print image. However, since the glossiness has different visibility depending on various observation angles, there is a demand for reproducing such characteristics with high accuracy.

JP 2006-261819 A

  Based on the above problems, the problem to be solved by the present invention is to accurately reproduce the glossiness of special gloss in a printed image.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
An image processing apparatus that performs image processing on image data representing an image and outputs the image data as print image data for printing to a printing apparatus that performs printing using a special glossy ink having a special gloss. Color information that is information indicating the color of the image based on the spectral reflectance at an angle, and gloss level information that is information indicating the degree of gloss of the image based on the spectral reflectance at a plurality of angles, Based on the input unit that inputs the image data, and the color information and the gloss level information of the input image data, an ink amount set that is a combination of ink amounts of the respective inks used for the printing by the printing apparatus A specifying unit for specifying, and an output unit for outputting print image data for printing based on the specified set of ink amounts to the printing apparatus, The color information and the gloss level information used for identification include the non-glossy multi-angle spectral reflectance which is a multi-angle spectral reflectance of an image by a combination of inks included in the printing apparatus other than the special glossy ink, and the special glossy An image processing apparatus that is information calculated based on a product of glossy multi-angle spectral reflectance, which is a multi-angle spectral reflectance of an image of ink.

  According to this image processing apparatus, for an image data including color information and gloss level information based on spectral reflectances at a plurality of angles of an image, an ink amount set is specified based on the color information and gloss level information. Therefore, the color and glossiness of the image can be accurately reproduced.

[Application Example 2]
The image processing apparatus according to application example 1, wherein the color information includes information based on a spectral reflectance at a regular reflection angle of the image.

  According to this image processing apparatus, it is possible to perform image processing so that a color value influenced by image bronzing is reproduced in a printed image.

[Application Example 3]
The image processing apparatus according to Application Example 1 or Application Example 2, wherein the specifying unit specifies the non-glossy multi-angle spectral reflectance corresponding to an arbitrary combination of ink amounts other than the special glossy ink. The non-glossy multi-angle spectroscopic model includes ink amount specifying data for specifying the ink amount set based on the color information and the gloss level information generated using the non-glossy multi-angle spectroscopic model. The multi-angle spectral reflectance was constructed based on each non-glossy multi-angle spectral reflectance measured in each printed image by a combination of a predetermined number of ink amounts of ink included in the printing device other than the glossy ink. An image processing apparatus which is a cell division Yule-Nielsen Spectral Neugebauer Model.

  According to this image processing device, the cell division Yule-Nielsen spectral Neugebauer model extended to multi-angle spectral reflectance is used as the non-glossy multi-angle spectral model, so the non-glossy multi-angle spectral reflectance can be specified with high accuracy. Can do.

[Application Example 4]
The image processing apparatus according to Application Example 3, wherein the ink amount specifying data is an image processing table in which an ink amount set is stored at each grid point with the color information and the gloss level information as axes. apparatus.

  According to this image processing apparatus, since the ink amount specifying data is a lookup table, the ink amount set can be specified as a relatively simple process.

[Application Example 5]
A printing apparatus comprising: the image processing apparatus according to any one of Application Examples 1 to 4; and a printing unit that performs printing based on the print image data.

  According to this printing apparatus, for image data including color information and gloss level information based on spectral reflectances at a plurality of angles of an image, an ink amount set is specified based on the color information and gloss level information. Therefore, it is possible to perform printing that accurately reproduces the color and glossiness of the image.

[Application Example 6]
An image processing method for performing image processing on image data representing an image and outputting as print image data for printing to a printing apparatus that performs printing using special glossy ink having special gloss, wherein the image data includes a plurality of image data Color information that is information indicating the color of the image based on the spectral reflectance at an angle, and gloss level information that is information indicating the degree of gloss of the image based on the spectral reflectance at a plurality of angles, Based on the input step of inputting the image data and the color information and the gloss level information of the input image data, an ink amount set that is a combination of ink amounts of the respective inks used for the printing by the printing apparatus A specifying step for specifying, and an output step for outputting print image data for printing based on the specified set of ink amounts to the printing apparatus. The color information and the glossiness information used in the process include a non-glossy multi-angle spectral reflectance which is a multi-angle spectral reflectance of an image by a combination of inks included in the printing apparatus other than the special glossy ink, and the special glossy An image processing method, which is information calculated based on a product of gloss multi-angle spectral reflectance, which is multi-angle spectral reflectance of an image of ink.

  According to this image processing method, for an image data including color information and gloss level information based on spectral reflectances at a plurality of angles of an image, an ink amount set is specified based on the color information and gloss level information. Therefore, the color and glossiness of the image can be accurately reproduced.

[Application Example 7]
A method of manufacturing a printing apparatus using a look-up table for converting a special glossy color expressed using special glossy into an ink amount set which is a combination of a plurality of ink amounts including special glossy ink having special glossiness A sample ink amount set preparing step for preparing a sample ink amount set which is a predetermined number of ink amount sets, and in each of the sample ink amount sets, a large number of images by combining inks other than the special glossy ink. A measuring step of measuring a non-glossy multi-angle spectral reflectance that is a spectral reflectance of an angle and a glossy multi-angle spectral reflectance that is a multi-angle spectral reflectance of an image of the special glossy ink, and the amount of each sample ink The multi-angle spectral reflectance of the set image is calculated based on the product of the non-glossy multi-angle spectral reflectance and the glossy multi-angle spectral reflectance. The special gloss using the calculating step for calculating, the calculated multi-angle spectral reflectance, and the calculation means for calculating the color of the special gloss color and the degree of gloss of the special gloss from the multi-angle spectral reflectance A look-up table generating step for generating the look-up table by storing an ink amount set at each grid point of the look-up table about the color of the special gloss color and the degree of gloss of the special glossy color; And a step of associating a lookup table with the printing apparatus.

  According to this method for manufacturing a printing apparatus, it is possible to manufacture a printing apparatus that stores a lookup table in which ink amount sets that reproduce the color of special gloss and the degree of special gloss are stored at lattice points.

[Application Example 8]
A method for generating a look-up table used for printing to convert a special glossy color expressed using special glossy into an ink amount set that is a combination of a plurality of ink amounts including special glossy ink having special glossiness. A sample ink amount set preparing step for preparing a sample ink amount set which is a predetermined number of ink amount sets, and in each of the sample ink amount sets, a large number of images by combining inks other than the special glossy ink. A measuring step of measuring a non-glossy multi-angle spectral reflectance that is a spectral reflectance of an angle and a glossy multi-angle spectral reflectance that is a multi-angle spectral reflectance of an image of the special glossy ink, and the amount of each sample ink Calculates multi-angle spectral reflectance of the set image based on the product of the non-glossy multi-angle spectral reflectance and the glossy multi-angle spectral reflectance Using the calculated multi-angle spectral reflectance and the calculation means for calculating the color of the special gloss color and the gloss of the special gloss from the multi-angle spectral reflectance. And an ink amount set storing step of storing an ink amount set at each lattice point of the look-up table centered on the color of the special gloss color and the gloss level of the special glossy color.

  According to this lookup table generation method, an ink amount set that reproduces the color of special gloss and the degree of special gloss can be stored in the grid points.

[Application Example 9]
The lookup table generation method according to Application Example 7, wherein the calculation step includes the non-glossy multi-angle spectral reflectance as Rc (λ, θ) and the glossy multi-angle spectral reflectance as Rm (λ, θ). , Rw (λ, θ), λ is the spectral component of the spectral reflectance, θ is the measurement angle of the spectral reflectance, and ic is the ink other than the special glossy ink. When the ink amount by combination, is is the ink amount of the special gloss ink, and i is the ink amount of the ink amount set including the special gloss ink,
R (λ, θ, i) = Rc (λ, θ, ic) · Rm (λ, θ, is) / Rw (λ, θ)
The look-up table generation method for calculating the multi-angle spectral reflectance R (λ, θ, i) defined in (1) as the multi-angle spectral reflectance of the image by each of the sample ink amount sets.

  According to this lookup table generation method, the multi-angle spectral reflectance of the ink amount set including the special glossy ink, the non-glossy multi-angle spectral reflectance Rc (λ, θ), and the glossy multi-angle spectral reflectance Rm ( It is calculated by the above formula using λ, θ). Therefore, if the non-glossy multi-angle spectral reflectance Rc (λ, θ) and the glossy multi-angle spectral reflectance Rm (λ, θ) are acquired separately, an ink amount set (ink amount set including special glossy ink) The look-up table can be generated without requiring the direct determination of the multi-angle spectral reflectance.

1 is an explanatory diagram illustrating a schematic configuration of a printing system 10. FIG. 2 is a configuration diagram of a printer 200. FIG. It is explanatory drawing explaining image data ORG-A. 6 is a flowchart illustrating a flow of printing processing. 3 is an explanatory diagram illustrating a configuration of a color conversion LUT generation apparatus 300. FIG. It is explanatory drawing explaining the data structure of initial LUT332. It is the flowchart explaining the flow of the LUT generation process. It is explanatory drawing explaining the multi-angle spectroscopic printing model converter RC. It is explanatory drawing explaining the metallic degree value converter DmC and the metallic color value converter CmC. It is a flowchart explaining the flow of an optimization process. It is explanatory drawing explaining prediction of the multi-angle spectral reflectance by a neural network.

Embodiments of the present invention will be described based on examples.
A. First embodiment:
(A1) System configuration:
FIG. 1 is an explanatory diagram illustrating a schematic configuration of a printing system 10 as a first embodiment of the present invention. The printing system 10 includes a computer 100 as a print control device and a printer 200 that actually prints an image under the control of the computer 100. The printing system 10 functions as a printing device in a broad sense as a whole.

  The computer 100 includes a CPU 20, a ROM 60, a RAM 62, and a hard disk (HDD) 66. The computer 100 is connected to a display 70, a keyboard 72, and a mouse 74 by respective cables. A predetermined operating system is installed in the computer 100, and an application program 30, a video driver 40, and a printer driver 50 operate under this operating system. The functions of these programs are stored in the ROM 60, the RAM 62, and the HDD 66, and are realized by the CPU 20 reading and executing each program from these storage areas.

  The application program 30 is a program for reproducing the image data ORG acquired from the memory card as the data supply unit 80. The pixel data of each pixel constituting the image data ORG includes a color value on the metallic luster defined in advance (hereinafter also referred to as a metallic color value Cm) and a degree of metallic luster (hereinafter referred to as metallic). Is also called a degree value Dm). The metallic color value Cm is recorded with gradation values of red (R), green (G), and blue (B), and the metallic degree value Dm is a scalar quantity, and is recorded with gradation values. Hereinafter, these values may be collectively expressed as pixel color component values (Cm, Dm) or (R, G, B, Dm). Details of the image data ORG will be described later.

  The application program 30 includes a source profile 31 for converting the color component value of the image data ORG into a preset print standard color, and a media profile 32 for reproducing the color of the image to be printed on a predetermined print medium. Are loaded from the HDD 66 into the RAM 62. When printing processing described later is started, the application program 30 performs data conversion on the acquired image data ORG using the source profile 31 and the media profile 32. Hereinafter, for convenience of explanation, the image data ORG input from the data supply unit 80 is the image data ORG-A, the image data ORG after the data conversion by the source profile 31 is the image data ORG-B, and the image after the data conversion by the media profile 32 Data ORG may be referred to as image data ORG-C.

  The source profile 31 includes one set of (L *, G, B) for one set of metallic color values (R, G, B) among the color component values (R, G, B, Dm) of the image data ORG-A. It is a three-dimensional lookup table that outputs the values of a *, b *). Further, the metallic degree value Dm remains after the data conversion using the source profile 31 and is recorded in the pixel data. That is, the color component value of each pixel data of the image data ORG-B after data conversion by the source profile 31 is recorded in the format of (L *, a *, b *, Dm).

  The media profile 32 is a set of (L *, a *, b *) color components among the color component values (L *, a *, b *, Dm) of the image data ORG converted by the source profile 31. It is a three-dimensional lookup table that outputs a set of (R, G, B) color component values for a value. Further, the metallic degree value Dm remains after the data conversion using the media profile 32 and is recorded in the pixel data. That is, the color component value of each pixel data of the image data ORG after data conversion by the media profile 32 is recorded in the format of (R, G, B, Dm). Hereinafter, the color component value of the image data ORG-A may be referred to as (Cm0, Dm0), and the color component value of the image data ORG-C may be referred to as (Cm1, Dm1).

  The printer driver 50 includes a color conversion module 52, a halftone module 54, and an interlace module 56. The color conversion module 52 uses a color conversion lookup table 64 (hereinafter also referred to as a color conversion LUT 64) included in the RAM 62 to use the color component values (R, R, C) of the pixel data of the image data ORG-C acquired from the application program 30. G, B, Dm) is converted into a combination of ink amounts of ink colors provided in the printer 200 (hereinafter also referred to as an ink amount set). The color conversion lookup table 64 is stored in the storage unit of the ROM 60, the RAM 62, or the HDD 66 when the printing system 10 is manufactured. The color conversion LUT 64 will be described in detail later.

  The halftone module 54 performs binarization processing on the ink amount set after color conversion and performs dot data generation processing (hereinafter also referred to as halftone processing). Specifically, the halftone module 54 uses image data ORG (hereinafter referred to as image data ORG) that is color-converted and expressed as an ink amount set using a dither matrix (not shown) prepared in advance by the printer driver 50. -D), dot data expressed by dot on / off is generated. The image data ORG represented by the gradation of the ink amount by the halftone module 54 becomes data represented by the distribution of dots. The interlace module 56 rearranges the dot arrangement of the generated dot data in the order to be transferred to the printer 200 and outputs the print data to the printer 200 as well as various commands such as a print start command and a print end command. Is output to the printer 200 to control the printer 200.

  FIG. 2 is a configuration diagram of the printer 200. As shown in FIG. 2, the printer 200 includes a control circuit 220 that controls the entire printer 200 and receives print data from the computer 100, and an operation panel 225. Further, the printer 200 drives a mechanism for transporting the print medium P by the paper feed motor 235, a mechanism for reciprocating the carriage 240 in the axial direction of the platen 236 by the carriage motor 230, and a print head 260 mounted on the carriage 240. And a mechanism for ejecting ink and forming dots, and a paper feed motor 235, a carriage motor 230, and a print head 260.

  The control circuit 220 includes a CPU, a ROM, a RAM, a PIF (peripheral device interface), and the like connected to each other via a bus. The control circuit 220 controls operations of the carriage motor 230 and the paper feed motor 235 to control the carriage 240. The main scanning operation and the sub scanning operation are controlled. When the print data output from the computer 100 is received via the PIF, the control circuit 220 supplies a drive signal corresponding to the print data to the print head 260 in accordance with the main scanning or sub scanning movement of the carriage 240. In addition, each color head can be driven.

  The carriage 240 is composed of C (cyan), M (magenta), Y (yellow), and K (black) color inks, and metallic ink having metallic luster (hereinafter also referred to as Mt) for a total of five colors. Ink cartridges 241 to 245 respectively containing the inks are mounted. The print head 260 below the carriage 240 is formed with five types of nozzle rows 261 to 265 corresponding to the above-described inks of the respective colors. When the ink cartridges 241 to 245 are mounted on the carriage 240 from above, ink can be supplied from the cartridges to the nozzle rows 261 to 265. In this embodiment, the ink cartridges 241 to 245 are arranged in the order of C, M, Y, K, and Mt in the main scanning direction of the carriage 240 as shown in FIG. Each nozzle is provided with a piezo element, and the control circuit 220 controls the contraction movement of the piezo element, so that the printer 200 can form dots for each ink color.

  When printing using these inks (C, M, Y, K, Mt), as shown in the figure, the latter half of the nozzle rows 261 to 264 that discharge color ink in the sub-scanning direction, and metallic ink Printing is performed using the first half portion in the sub-scanning direction of the nozzle row 265 that discharges the ink. In this way, by using each nozzle row, the metallic ink (Mt) dots are first formed on the print medium P, and the color ink dots are formed on the metallic ink (Mt). It can be expressed by a printed image.

  Here, details of the metallic ink will be described. A metallic ink is an ink in which a printed material exhibits a metallic feeling. As such a metallic ink, for example, an oil-based ink composition containing a metal pigment, an organic solvent, and a resin can be used. In order to produce a visually metallic texture effectively, the above-mentioned metal pigment is preferably tabular grains, the major axis on the plane of the tabular grains is X, the minor axis is Y, When the thickness is Z, the 50% average particle diameter R50 of the equivalent circle diameter determined from the area of the XY plane of the tabular grains is 0.5 to 3 μm, and the condition of R50 / Z> 5 is satisfied. It is preferable.

  Such a metal pigment can be formed of, for example, aluminum or an aluminum alloy, or can be formed by crushing a metal vapor-deposited film. The concentration of the metal pigment contained in the metallic ink can be set to 0.1 to 10.0% by weight, for example. Of course, the metallic ink is not limited to such a composition, and any other composition can be adopted as long as it is a composition that produces a metallic feeling. In this embodiment, the composition of the metallic ink is 1.5% by weight of an aluminum pigment, 20% by weight of glycerin, 40% by weight of triethylene glycol monobutyl ether, and 0.1% by weight of BYK-UV3500 (manufactured by Big Chemie Japan). did.

(A2) Printing process:
Next, a printing process performed by the printing system 10 on the image data ORG will be described. First, the image data ORG-A acquired by the printing system 10 from the data supply unit 80 will be described. FIG. 3 is an explanatory diagram for explaining the image data ORG-A. As described above, in each pixel data of the image data ORG-A, the color component value is defined by the metallic color value Cm and the metallic degree value Dm.

  The metallic color value Cm (R, G, B) is specified based on the spectral reflectance (multi-angle spectral reflectance) of the image to be printed at a plurality of reflection angles (spectral reflectance measurement angles). , A value representing the color of the image. For example, assuming that the direction perpendicular to the measurement surface of the print object for measuring the spectral reflectance is the reference direction (θ = 0 °), incident light is irradiated to the print object at an incident angle of θ = 45 ° with respect to the reference direction. The spectral reflectance at a plurality of angles such as reflection angle θ = 0 ° and −45 ° is measured. Thereafter, each spectral reflectance is converted into L * a * b * using a color matching function. In this embodiment, the spectral reflectance is measured at a reflection angle θ = 0 °, which is generally employed for colorimetry, and at θ = −45 ° (regular reflection angle) where a bronzing phenomenon (gold shine) appears remarkably. . After that, based on the two obtained L * a * b * (reflection angle θ = 0 °, −45 °), based on predetermined data and conversion formula, a metallic defined by (R, G, B) Convert to color value Cm. The predetermined data used for the conversion is, for example, a multi-angle spectral reflectance using various color samples (color patches) having a metallic luster (in this embodiment, a reflection angle θ = 0 °, −45 °), Measured data that associates the ink amount set used to generate the color patch and (R, G, B) represented by the ink amount set, or a prediction model based on the measured data can be used.

  On the other hand, the metallic degree value Dm is a value representing the degree of gloss of an image based on the spectral reflectance (multi-angle spectral reflectance) of the image at a plurality of reflection angles (spectral reflectance measurement angles) with respect to the reference direction. It is. For example, incident light is irradiated onto the printing object at an incident angle of θ = 45 ° with respect to the reference direction, and the spectral reflectance at a plurality of angles such as reflection angles θ = −30 ° and −45 ° is measured. Thereafter, each spectral reflectance is converted into L * a * b * using a color matching function. Then, among each L * a * b * after conversion, each brightness value “L *” (hereinafter, the brightness value at each reflection angle is described as L * (−30 °) or L * (−45 °). Therefore, the metallic degree value Dm as the scalar quantity is specified by a predetermined method. As a method for defining the correspondence between the plurality of lightness values L * and the metallic degree value Dm as one scalar quantity, for example, a patch (metallic metallic pattern) in which metallic ink Mt is printed at a plurality of stages of ink quantities. By using an experiment, a correspondence relationship between a lightness value L * (for example, L * (−30 °) and L * (−45 °)) and a metallic degree value Dm is established by experiment, and other lightness values are obtained. Correspondence between L * and metallic degree value Dm is calculated and specified by interpolation. In this way, the image data ORG-A is defined. Note that the image data ORG-A defines the color component value as (R, G, B, Dm), and therefore, when there is a predetermined color area that does not have metallic luster on the print target, the image data The color component value corresponding to the area in ORG-A may be recorded as Dm = 0.

  In the present embodiment, the metallic degree value Dm as the scalar amount is specified from L * (−30 °) and L * (−45 °), but the metallic degree value Dm is determined as L * (−30 °) or L * It may be specified as a vector quantity consisting of (−45 °) and applied to the printing system 10.

  In the present embodiment, the metallic color value Cm and the metallic degree value Dm are measured and recorded as image data using a spectral reflectometer. For example, the multi-angle reflected light of the printing object is reflected by a mirror or a plurality of CCDs ( Using a scanner that can measure the multi-angle spectral reflectivity of the print object, record the metallic color value Cm and the metallic degree value Dm of the print object as image data. You may do that.

  Next, the flow of printing processing performed by the CPU 20 will be described. FIG. 4 is a flowchart illustrating the flow of the printing process. The printing process is started when the user instructs printing on the application program 30. When the printing process is started, the CPU 20 uses the source profile 31 as a function of the application program 30 to convert the image data ORG-A recorded by the color component values (R, G, B, Dm) to the color. Data conversion (source profile conversion) is performed on the image data ORG-B defined by the component values (L *, a *, b *, Dm) (step S112). Thereafter, the CPU 20 uses the media profile 32 to convert the image data ORG-B defined by the color component values (L *, a *, b *, Dm) into the color component values (R, G, B, Dm). Data conversion (media profile conversion) is performed on the image data ORG-C defined by (step S114). That is, the application program 30 applies the values (R, G, B) of the metallic color values Cm of the image data ORG-A recorded with the color component values (Cm, Dm) to the print standard color and the print medium. The image data ORG-C output from the application program 30 also has a color component value in the format of (Cm, Dm).

  After performing the media profile conversion, the CPU 20 includes the color component values (R, G, B, Dm) of the image data ORG-C using the color conversion LUT 64 as a function of the color conversion module 52. Color conversion is performed to an ink amount set (C, M, Y, K, Mt) defined by the ink amounts of C, M, Y, K, and Mt (step S116). Hereinafter, the ink amount set data is also referred to as ink amount data.

  The color conversion lookup table 64 is a four-dimensional lookup table composed of four axes of R, G, B, and Dm. Each grid point has an ink amount set (C, M, Y, K). , Mt) are stored. The axes (R, G, B) of the color conversion lookup table 64 indicate the metallic color value Cm, that is, (R, G, B) as the color value on the metallic luster. Each grid point of the color conversion lookup table 64 is adjusted so as to reproduce the color and gloss level in the metallic luster determined by the metallic color value Cm and the metallic degree value Dm recorded in the image data ORG-A. (C, M, Y, K, Mt) ink amount sets are stored. Further, the ink amounts C, M, Y, K, and Mt are respectively defined by gradations of 0 to 255. Using the color conversion lookup table 64, the color conversion module 52 performs color conversion processing.

  After performing the color conversion process, the CPU 20 performs a halftone process (step S118) and an interlace process (step S120) on the ink amount data, and causes the printer 200 to execute printing (step S122). In this way, the printing system 10 performs a printing process.

(A3) Color conversion LUT generation method:
Next, a method for generating the color conversion LUT 64 used for the color conversion process (FIG. 4: step S116) will be described. The color conversion LUT 64 is generated using the color conversion LUT generation device 300. FIG. 5 is an explanatory diagram illustrating the configuration of the color conversion LUT generation device 300. The color conversion LUT generation apparatus 300 is configured as a computer including a CPU 310, a ROM 320, a RAM 330, a hard disk (HDD) 340, a monitor (not shown) and various input / output interfaces. The CPU 310 includes a processing target grid point selection unit 312, an optimization processing unit 314, and an LUT update unit 316. Further, the optimization processing unit 314 includes a multi-angle spectral printing model converter RC, a metallic degree value converter DmC, and a metallic color value converter CmC. These processing units are realized by the CPU 310 reading out the program stored in the ROM 320 to the RAM 330 and executing the program. The RAM 330 stores an initial LUT 332. The HDD 340 stores an evaluation function 344.

  The color conversion LUT 64 is generated by the color conversion LUT generation device 300 performing an LUT generation process to be described later and optimizing and updating the ink amount set stored in each grid point of the initial LUT 332. FIG. 6 is an explanatory diagram for explaining the data structure of the initial LUT 332. The initial LUT 332 includes a metallic degree value Dm and a metallic color value Cm (R, G, B) as input value axes, and an ink amount set (C, M, Y, K, Mt) as an output value. Each grid point of the initial LUT 332 before the LUT generation process stores an ink amount set before updating (hereinafter also referred to as an initial ink amount set). The initial ink amount set can be set by various methods. For example, the ink amount set (C, M, Y, K, Mt) = (255, 0, 0, 0, 0), (0, 255, 0, 0, 0), (0, 0, 255, 0, 0), (0,0,0,255,0), (0,0,0,0,255), etc., and several representative ink amount sets (representative ink amount sets) are selected and the representative inks are selected. Create a color patch as a color sample that was actually printed with a quantity set, measure the multi-angle spectral reflectance of the color patch, and perform calculations using color matching functions. A color value Cm and a metallic degree value Dm are specified. Then, each corresponding representative ink amount set is stored in each grid point of the initial LUT 332 corresponding to the specified metallic color value Cm (R, G, B) and the metallic degree value Dm. In this way, the representative ink amount set is stored in several grid points, and the remaining grid points are set based on the grid points in which the representative ink amount set is already stored by a predetermined interpolation operation. Is stored. In this embodiment, the initial LUT 332 is created in this way and stored in the RAM 330.

  Next, the LUT generation process performed by the CPU 310 will be described. FIG. 7 is a flowchart illustrating the flow of the LUT generation process. When the color conversion LUT generation process is started, the CPU 310 selects a processing target grid point to be processed from the initial LUT 332 according to a predetermined order as a function of the processing target grid point selection unit 312 (step S202). Then, the CPU 310 reads the ink amount set stored in the processing target grid point (step S204). Thereafter, as a function of the optimization processing unit 314, the CPU 310 performs an optimization process of adjusting each ink amount value of the read ink amount set of the processing target grid point to an ink amount value that meets a predetermined condition (Step S310). S210). In this optimization process, the CPU 310 uses a multi-angle spectral printing model converter RC, a metallic degree value converter DmC, and a metallic color value converter CmC. The optimization process will be described in detail later.

  After the optimization process, the CPU 310 updates the initial LUT 332 by overwriting the processing target grid point with an ink amount set (hereinafter also referred to as an optimal ink amount set) in which the value of each ink amount is optimized (step S222). . The CPU 310 performs optimization and update of the ink amount set as described above using all grid points of the initial LUT 332 as processing target grid points (step S224), and ends the LUT generation process. In addition, after the LUT generation process is completed, the initial LUT 332 of the RAM 330 is updated, and the color conversion LUT 64 is generated. In this way, the LUT generation process is performed.

(A4) Optimization process:
Next, the optimization process (step 210) will be described. First, the multi-angle spectral printing model converter RC, the metallic degree value converter DmC, and the metallic color value converter CmC used for the optimization process will be described. FIG. 8 is an explanatory diagram for explaining the multi-angle spectral printing model converter RC. As shown in FIG. 8A, the multi-angle spectral printing model converter RC converts an arbitrary ink amount set (C, M, Y, K, Mt) to a multi-angle spectral reflectance R (λ, θ, i). It is a converter to convert to. In this embodiment, the multi-angle spectral reflectance R (λ, θ, i) is defined by the following formula (1).

(Equation 1)
R (λ, θ, i) = Rc (λ, θ, ic) · Rm (λ, θ, im) / Rw (λ, θ) (1)
λ: wavelength element of reflected light θ: reflection angle element of reflected light i: ink amount (C, M, Y, K, Mt) of ink used for printing processing
ic: Color ink set (C, M, Y, K)
im: Ink amount of metallic ink (Mt)

  In Expression (1), Rc (λ, θ, ic) indicates the multi-angle spectral reflectance of the printed image in the ink amount set ic of the color ink. Rm (λ, θ, im) represents the multi-angle spectral reflectance of the printed image at the ink amount im of the metallic ink single color. Rw (λ, θ) represents the multi-angle spectral reflectance of the ground color of a predetermined print medium, that is, the print medium used for the printing process. In the present embodiment, the spectral reflectance R (λ, θ, i) is calculated by the equation (1). However, the present invention is not limited to this, and an external factor that affects the spectral reflectance R (λ, θ, i). Spectral reflectance R (λ, θ, i) may be calculated using a relational expression in which factors are added as parameters and coefficients.

  FIG. 8B is an explanatory view for conceptually explaining the multi-angle spectral printing model converter RC. The multi-angle spectroscopic printing model converter RC is a measured value of Rc (λ, θ, ic) and Rm (λ, θ, im) in a predetermined number of ink amount sets (C, M, Y, K, Mt). This is a prediction model for predicting the multi-angle spectral reflectance R (λ, θ) in an arbitrary ink amount set (C, M, Y, K, Mt) from (measured value). When the multi-angle spectral printing model converter RC predicts the multi-angle spectral reflectance R (λ, θ), the multi-angle spectral reflectance Rc (λ, θ, ic) in the ink amount set of the color ink and the metallic ink The multi-angle spectral reflectance Rm (λ, θ, im) is predicted separately, and the multi-angle spectral reflectance R (λ, θ) is calculated from the predicted reflectances by performing calculation according to the equation (1). .

  A method of predicting the multi-angle spectral reflectance Rc (λ, θ, ic) in the ink amount set of color ink will be described. First, a color patch is actually printed at a plurality of representative points in the ink amount space of the color ink (C, M, Y, K), and the multi-angle spectral reflectance (in this embodiment, the reflection angle θ = 0 °, -45 °) is measured with a spectral reflectometer. And, using the database of multi-angle spectral reflectivity obtained by measurement, the Cell Division Yule-Nielsen Spectral Neugebauer Model (hereinafter referred to as CYNSN model) extended to multi-angle spectral reflectivity. The multi-angle spectral reflectance Rc (λ, θ, ic) when printing is performed with an ink amount set (C, M, Y, K) of an arbitrary color ink. Note that prediction by the cell division Yule-Nielsen Spectral Neugebauer Model is a known technique (for example, Japanese Patent Application Laid-Open No. 2007-511161), and thus description thereof is omitted.

  A method for predicting the multi-angle spectral reflectance Rm (λ, θ, im) of the metallic ink will be described. First, the ink amount is changed in several steps, and a printed image (hereinafter also referred to as a metallic patch) as a metallic ink color sample for each ink amount is actually printed, and the multi-angle spectral reflectance of each metallic patch is determined. Actually measured (actually measured) with a spectral reflectometer. Then, using a database of multi-angle spectral reflectances in the ink amount of each metallic ink obtained by measurement and performing an interpolation operation (for example, linear interpolation), printing is performed with an ink amount of an arbitrary metallic ink. Multi-angle spectral reflectance Rm (λ, θ, im) is predicted.

  Rw (λ, θ), which is the multi-angle spectral reflectance of the ground color of the print medium, is obtained by actually measuring the print medium with a spectral reflectometer. In this way, the multi-angle spectroscopic printing model converter RC performs multi-angle spectroscopic from (C, M, Y, K) to an arbitrary ink amount set (C, M, Y, K, Mt) input in this way. The reflectance Rc (λ, θ, ic) is predicted, the multi-angle spectral reflectance Rm (λ, θ, im) is predicted from (Mt), and the multi-angle spectral reflectance of the print medium acquired in advance by measurement Using Rw (λ, θ), R (λ, θ, i) shown in Equation (1) is output by calculation.

  Next, the metallic color value converter CmC and the metallic degree value converter DmC will be described. FIG. 9 is an explanatory diagram for explaining the metallic color value converter CmC and the metallic degree value converter DmC. The metallic color value converter CmC acquires the multi-angle spectral reflectance R (λ, θ) output by the multi-angle spectral printing model converter RC for the ink amount set (C, M, Y, K, Mt), and reflects it. R (λ) at an angle θ = 0 ° and a reflection angle θ = −45 ° is calculated. Then, for each of the calculated two R (λ) (θ = 0 °, −45 °), an L * a * b * value is calculated using a color matching function. Then, (R, G, B) as the metallic color value Cm is specified by a predetermined method using the calculated two L * a * b * values. As a method of specifying the metallic color value Cm from the two L * a * b * values, for example, as described above, a method of specifying the metallic color value Cm in the image data ORG-A can be used.

  On the other hand, the metallic degree value converter DmC acquires the multi-angle spectral reflectance R (λ, θ) output by the multi-angle spectral printing model converter RC for the ink amount set (C, M, Y, K, Mt). For example, when the metallic degree value Dm is defined by the spectral reflectances at two reflection angles of reflection angles θ = −30 ° and −45 °, the spectral reflectance R (at reflection angles θ = −30 ° and −45 °) λ) is calculated. Then, L * a * b * values are calculated for each calculated spectral reflectance R (λ) using a color matching function. Thereafter, the metallic degree value Dm is specified by a predetermined method using each L * (−30 °) and L * (−45 °) of the calculated L * a * b * values. As a method of specifying the metallic degree value Dm as the scalar quantity from the plurality of lightness values L *, for example, as described above, a method of specifying the metallic degree value Dm in the image data ORG-A can be used.

  The CPU 310 performs an optimization process using the multi-angle spectral printing model converter RC, the metallic degree value converter DmC, and the metallic color value converter CmC described above. FIG. 10 is a flowchart showing the flow of optimization processing performed by the CPU 310. When the optimization process is started, the CPU 310 sets the ink amount set of the processing target grid point read as the LUT generation process (FIG. 7: step S204) as an optimization initial value (hereinafter also referred to as an initial ink amount set). (Step S211).

  Then, as shown in the lower part of FIG. 10, the evaluation is performed using the multi-angle spectral printing model converter RC, the metallic degree value converter DmC, the metallic color value converter CmC, and the evaluation function defined in the following formula (2). The value of each ink amount in the initial ink amount set (C, M, Y, K, Mt) is adjusted so that the value E is minimized (step S212). Ix = (Cx, Mx, Yx, Kx, Mtx) shown in the lower part of FIG. 10 indicates an adjusted ink amount set input to the multi-angle spectral printing model converter RC when adjusting the ink amount set. Dmx indicates the metallic color value Cm (= R, G, B) output via RC, DmC, CmC and the metallic degree value Dm for the adjusted ink amount set ix.

  In the above equation (2), w1 and w2 indicate predetermined weighting factors. <> Means a vector. Cm0 and Dm0 are Cm0 and Dm0 as target values set by a predetermined method (for example, experiments and interpolation based on experimental values). In addition, Cm0 and Dm0 can be set by various methods such as adopting a value compliant with the ICC profile. Further, as a method for adjusting the ink amount so that the evaluation value E becomes the minimum value, an optimization method such as a steepest descent method, a quasi-Newton method, or a simplex method can be employed.

  In the present embodiment, the above formula (2) is adopted as the evaluation function, but another evaluation function in the form of the general formula shown in the following formula (3) using Cmx and Dmx as parameters may be adopted. In addition, as an evaluation factor of the evaluation function, a term for evaluating gradation with adjacent grid points, a term for evaluating the graininess of ink dots, and a term for controlling the image quality of a printed image may be added. .

  In this way, after adjusting each ink amount with respect to the initial ink amount set, the CPU 310 sets the ink amount set (C, M, Y, K, Mt) that minimizes the evaluation value E to the optimum ink amount. As a set, the initial LUT 332 is updated using the optimum ink amount set in step S222 in the LUT generation process (FIG. 7) described above. The optimization process has been described above.

  As described above, according to the printing system 10, the color and the gloss level of the image to be printed are defined using the metallic color value Cm and the metallic degree value Dm based on the multi-angle spectral reflectance of the image. In the printing process, the ink amount of the metallic ink is specified based on the metallic color value Cm and the metallic degree value Dm of the image data ORG, so that the metallic glossy color and the degree of glossiness are suitably reproduced in the printed image. be able to.

  In the printing system 10 according to the present embodiment, the metallic color value Cm is defined based on the spectral reflectance of regular reflection (reflection angle θ = −45 °) that is likely to cause bronzing when the object surface is observed. . Therefore, it is possible to reproduce the color value influenced by the bronzing of the print object on the print image. Further, in the process in which the multi-angle spectral printing model converter RC predicts the multi-angle spectral reflectance R (λ, θ, ic) of the ink amount set (C, M, Y, K) of any color ink, Since prediction is performed using the CYNSN model extended to the spectral reflectance, it is possible to perform prediction with high accuracy.

  Furthermore, in this embodiment, the multi-angle spectral reflectance R (λ, θ, i) is set to the spectral reflectance Rc (λ, θ, ic) of the ink amount set (C, M, Y, K) of the color ink. , And defined as the product of multi-angle spectral reflectance Rm (λ, θ, im) in the amount of ink of metallic ink (Mt) single color. The multi-angle spectral reflectance Rm (λ, θ, im) for the ink amount of the metallic ink single color is measured by a color sample (metallic patch) generated by changing the ink amount of the metallic ink single color in several stages. From the angular spectral reflectance, the multi-angle spectral reflectance at an arbitrary amount of metallic ink is predicted by a relatively simple interpolation calculation. From these, it is compared with the case where the multi-angle spectral reflectance R (λ, θ, i) of the ink amount set (C, M, Y, K, Mt) including the metallic ink is directly measured and predicted. Thus, the multi-angle spectral reflectance R (λ, θ, i) can be predicted with a small amount of information, and the number of work operators required for measurement and the like can be reduced.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.
(B1) Modification 1:
In the above embodiment, the spectral reflectance R (λ, θ, i) is calculated in the equation (1). However, the present invention is not limited to this, and external factors that affect the spectral reflectance R (λ, θ, i) are used. Spectral reflectance R (λ, θ, i) may be calculated using a relational expression added as a parameter or coefficient. Thereby, the accuracy of the spectral reflectance R (λ, θ, i) can be improved.

(B2) Modification 2:
In the above embodiment, the multi-angle spectral printing model converter RC predicts the multi-angle spectral reflectance R (λ, θ, ic) of the ink amount set (C, M, Y, K) of the color ink. Although the prediction is performed using the CYNSN model extended to the multi-angle spectral reflectance, the present invention is not limited to this. For example, the multi-angle spectral reflectance R (λ, θ, ic) may be specified using a neural network. Good. FIG. 11 is an explanatory diagram for explaining prediction of the multi-angle spectral reflectance R (λ, θ) by the neural network. As shown in the figure, for example, it can be realized by a three-layer network in which the input layer is an ink amount and the output layer is a multi-angle reflectance component. The neural network can be designed by a general method, and a plurality of inputs xi to each node (neuron) are converted as shown in the following equation (4).

  Here, i identifies the input to the neuron, ai is the weight for each input, and b is a parameter as a bias. ψ represents a transfer function, and a linear transformation, a sigmoid function, or the like can be adopted. These parameters ai and b exist in the intermediate layer and the output layer, and each parameter is determined by learning such as backpropagation. Even if R (λ, θ) is predicted from the ink amount set (C, M, Y, K) by such a method, the metallic luster can be suitably reproduced in the printed image as in the above-described embodiment. . Furthermore, since a neural network can be constructed by a relatively simple process, the multi-angle spectral printing model converter RC can be easily generated.

(B3) Modification 3:
In the above embodiment, C, M, Y, and K are used as the color inks provided in the printing apparatus. However, for example, light cyan (Lc), light magenta (Lm), etc. are also used, and the printing system in the above embodiment 10 can be expanded. In addition, the printing system 10 can be expanded using inks such as orange (Or) and green (G) for expanding a color region that can be reproduced in printing.

(B4) Modification 4:
In the above-described embodiments, the configuration in which printing is performed using metallic ink and color ink has been described. However, configurations using color ink and various special glossy inks can be employed. Special gloss ink is an ink that exhibits a special gloss on the surface of the printed media, and reflects the optical properties of the ink printed on the surface of the print medium in addition to the metallic ink containing a pigment that expresses a metallic feeling. The ink may have angle dependency and may have various appearances depending on the viewing angle. Specifically, as the ink, in addition to the metallic ink, a pearly ink containing a pigment that develops a pearly luster after fixing on the medium surface; A laminar ink or a pigment-containing ink containing a pigment having fine irregularities so as to express a textured background can be used. In addition, a special glossy ink for reproducing the texture such as a clear ink for reproducing the gloss and a gold ink having a gold color can be adopted and applied to the printing system 10. In this way, various textures can be reproduced.

(B5) Modification 5:
In the above-described embodiments, the metallic degree value Dm in the image data ORG-A is the scalar amount specified from the multi-angle spectral reflectance of the print object, but the image data in which the metallic ink amount (Mt) is recorded as it is. ORG, for example, Mt of image data ORG recorded as (R, G, B, Mt) is interpreted as a metallic degree value Dm as it is, or is interpreted as a metallic degree value Dm by a predetermined conversion, and printing processing is performed. Also good.

(B6) Modification 6:
As the reflection angle θ of the multi-angle spectral reflectance used when defining the metallic color value Cm and the metallic degree value Dm, a reflection angle θ other than that employed in the above embodiment may be adopted. Even if it does in this way, the effect similar to the said Example can be acquired.

(B7) Modification 7:
The color conversion process using the color conversion lookup table 64 described above can be realized in various modes. For example, the created color conversion lookup table 64 may be stored in a storage unit (for example, ROM) included in the printer 200, and the printer 200 may perform color conversion processing using the color conversion lookup table 64. As another configuration, as in the above-described embodiment, the created color conversion lookup table 64 is stored in a storage unit such as a computer (for example, a hard disk, ROM, or RAM) that can communicate with the printing apparatus, and the computer uses a color. The converted image data may be transmitted to the printing apparatus. As another aspect, the color conversion lookup table 64 is stored in a server or the like without being stored in the storage unit of the printing apparatus or computer, and the color conversion lookup table 64 is stored in the printer 200 together with the storage. It is also possible to adopt a mode in which the fact that it can be used is recognizable.

10 ... Printing system 20 ... CPU
DESCRIPTION OF SYMBOLS 30 ... Application program 31 ... Source profile 32 ... Media profile 40 ... Video driver 50 ... Printer driver 52 ... Color conversion module 54 ... Halftone module 56 ... Interlace module 62 ... RAM
64 ... Color conversion lookup table 70 ... Display 72 ... Keyboard 74 ... Mouse 80 ... Data supply unit 100 ... Computer 200 ... Printer 220 ... Control circuit 225 ... Operation panel 230 ... Carriage motor 231 ... Drive belt 232 ... Pulley 233 ... Sliding Shaft 235 ... Motor 236 ... Platen 240 ... Carriage 241 ... Ink cartridge 260 ... Print heads 261 to 266 ... Nozzle array 300 ... Color conversion LUT generator 310 ... CPU
312 ... Processing target grid point selection unit 314 ... Optimization processing unit 330 ... RAM
332 ... Initial LUT
ORG-A to D ... image data P ... print medium RC ... multi-angle spectral printing model converter DmC ... metallic degree value converter CmC ... metallic color value converter Dm ... metallic degree value Cm ... metallic color value ix ... adjusted ink amount set

Claims (7)

An image processing apparatus that performs image processing on image data representing an image and outputs the image data as print image data for printing to a printing apparatus that performs printing using special glossy ink having special gloss,
The image data is color information that is information indicating the color of the image based on spectral reflectance at a plurality of angles, and gloss that is information indicating the degree of gloss of the image based on the spectral reflectance at a plurality of angles. Including degree information,
An input unit for inputting the image data;
Based on the color information and the gloss level information of the input image data, a specifying unit that specifies an ink amount set that is a combination of ink amounts of each ink used for the printing by the printing device;
An output unit that outputs print image data for printing based on the specified ink amount set to the printing apparatus,
The color information and the gloss information used for the identification by the identifying unit are the non-glossy multi-angle spectral reflectance that is a multi-angle spectral reflectance of an image by a combination of inks included in the printing apparatus other than the special glossy ink. And an image processing apparatus that is information calculated based on a product of the glossy multi-angle spectral reflectance that is the multi-angle spectral reflectance of the image with the special glossy ink. The image processing apparatus according to claim 1,
The image processing apparatus, wherein the color information includes information based on a spectral reflectance at a regular reflection angle of the image. The image processing apparatus according to claim 1 or 2,
The specific part is:
The color information and the gloss generated using the non-glossy multi-angle spectral model, which is a model for specifying the non-glossy multi-angle spectral reflectance corresponding to any combination of ink amounts other than the special glossy ink. From the degree information, ink amount specifying data for specifying the ink amount set is provided,
The non-glossy multi-angle spectroscopic model is
A multi-angle spectral reflectance constructed based on each non-glossy multi-angle spectral reflectance measured in each print image by a combination of ink amounts of a predetermined number of inks included in a printing device other than the special gloss ink. An image processing device that is an expanded Cellular Yule-Nielsen Spectral Neugebauer Model. The image processing apparatus according to claim 3,
The image processing apparatus is an image processing apparatus in which the ink amount specifying data is a look-up table in which an ink amount set is stored at each grid point with the color information and the gloss level information as axes. An image processing apparatus according to any one of claims 1 to 4,
And a printing unit that executes printing based on the print image data. An image processing method for performing image processing on image data representing an image and outputting as print image data for printing to a printing apparatus that performs printing using special glossy ink having special gloss,
The image data is color information that is information indicating the color of the image based on spectral reflectance at a plurality of angles, and gloss that is information indicating the degree of gloss of the image based on the spectral reflectance at a plurality of angles. Including degree information,
An input step of inputting the image data;
A specifying step of specifying an ink amount set that is a combination of ink amounts of the respective inks used by the printing apparatus based on the color information and the gloss level information of the input image data;
An output step of outputting print image data for printing based on the specified ink amount set to the printing apparatus;
With
The color information and the glossiness information used in the specifying step are a non-glossy multi-angle spectral reflectance which is a multi-angle spectral reflectance of an image by a combination of inks included in the printing apparatus other than the special glossy ink, and An image processing method, which is information calculated based on a product of glossy multi-angle spectral reflectance, which is multi-angle spectral reflectance of an image with special glossy ink. A method of manufacturing a printing apparatus using a look-up table for converting a special glossy color expressed using special glossy into an ink amount set which is a combination of a plurality of ink amounts including special glossy ink having special glossiness There,
A sample ink amount set preparation step of preparing a sample ink amount set which is a predetermined number of ink amount sets;
In each of the sample ink amount sets, a non-glossy multi-angle spectral reflectance that is a multi-angle spectral reflectance of an image by a combination of inks other than the special glossy ink, and a multi-angle spectral reflection of the image by the special glossy ink. A measurement process for measuring the glossy multi-angle spectral reflectance, which is a rate,
A calculation step of calculating the multi-angle spectral reflectance of the image by each sample ink amount set based on the product of the non-glossy multi-angle spectral reflectance and the glossy multi-angle spectral reflectance;
Utilizing the calculated multi-angle spectral reflectance and calculation means for calculating the color of the special gloss color and the gloss level of the special gloss from the multi-angle spectral reflectance, the color of the special gloss and the special gloss A lookup table generation step of generating the lookup table by storing an ink amount set at each grid point of the lookup table with the gloss level of gloss color as an axis;
Associating the generated lookup table with the printing apparatus.

Images