JP2014204172A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce colored gloss according to recording material in a soft proof process of a printed matter under observation illumination.SOLUTION: For each pixel of image data which is to be proofed, following processes are made. In short, at a diffusion component specification part 102, a color value of a diffuse reflection component of observation illumination light obtained from a printed matter of an interested pixel is specified. At a surface ink specification part 103, a recording material deposited on a top surface of the printed matter of the pixel is specified. At a gloss component specification part 104 and a deflection characteristic specification part 105, a color value of regular reflection component of the observation illumination light caused by the specified printed matter of the recording material and a deflection reflection characteristic are respectively specified. At a proof image generation part 106, a proof color is calculated from color values of the specified diffusion reflection component and regular reflection component as well as the deflection reflection characteristic, to generate a proof image.

Description

  The present invention relates to an image processing apparatus and an image processing method for performing soft proof processing for reproducing a printed matter under observation illumination on a monitor.

  2. Description of the Related Art Conventionally, in the field of printing, a technique called soft proof is used in which a finished state of an actual printed matter by a printer or the like is simulated and displayed on a device. In general soft proofing, color matching processing is performed on the color components of diffusely reflected light in an actual printed product, and the color is faithfully reproduced on a display device. The flow of a general soft proof process is shown below. First, print image data composed of CMYK data is converted into a standard color space, for example, L * a * b *. Then, L * a * b * obtained by the color conversion is converted into RGB data based on a display device profile held in advance, and the RGB data is input to a color monitor to display an image. Soft proofing is realized.

  On the other hand, in recent soft proof processing, in addition to the diffuse reflection component described above, a computer graphics (hereinafter referred to as CG) is used to add a gloss component (specimen reflection component) to a gloss component (reflection of an illumination image). ) And other technologies for simulation are spreading. For example, for a target printed matter, a variable angle reflection characteristic (hereinafter referred to as a variable angle characteristic) indicating how the irradiated light is reflected with respect to each emission angle is represented by a CG model such as a Phong model. To approximate the glossy component. Further, in order to reflect the angle change characteristic with higher accuracy, a method of synthesizing and approximating a plurality of CG models for each color of input image data has been proposed (for example, see Patent Document 1).

JP 2004-126692 JP

  However, when gloss reproduction by the above-described conventional technique is performed in the soft proof process, it is possible to reproduce the angle change characteristic, but it is impossible to reproduce the glossy coloring. Here, the glossy coloring is a phenomenon in which the reflection of the illumination image (the illumination image observed on the sample surface on the monitor) looks different from the original color of the illumination. In the following, the bronze phenomenon that occurs according to the ink characteristics will be described as being the main cause of glossy coloring. For example, in the case of approximating only the angle change characteristic by the method of Patent Document 1 described above, the change in glossy color due to the difference in ink cannot be reproduced, and the glossy color is white or always a uniform color depending on the light source color. It had become.

  In view of the above problems, an object of the present invention is to provide an image processing apparatus and an image processing method capable of reproducing glossy coloring according to a recording material in soft proof processing of printed matter.

  As a means for achieving the above object, an image processing apparatus of the present invention comprises the following arrangement.

  That is, an image processing apparatus that performs soft proofing of a printed matter under observation illumination, and includes input means for inputting image data to be proofed, and observation illumination light from the printed matter having a pixel value for each pixel of the image data. Diffuse component specifying means for specifying the color value of the diffuse reflection component, recording material specifying means for specifying the recording material deposited on the outermost surface of the printed material for each pixel of the image data, and the printed material of the specified recording material Gloss component specifying means for specifying the color value of the regular reflection component of the observation illumination light, and calculating the proof color from the color value of the diffuse reflection component specified and the color value of the regular reflection component for each pixel of the image data. And a proof image generating means for generating a proof image.

  According to the present invention, it is possible to reproduce the gloss coloring according to the recording material in the soft proofing process of the printed matter.

A block diagram showing a configuration of a soft proof system in a first embodiment according to the present invention, The figure which shows the concept of the diffusion component in 1st execution form, luster component and angle change characteristic, A diagram showing various LUT examples used in the first embodiment, A flowchart showing surface ink identification processing in the first embodiment, A flowchart showing a proof image generation process in the first embodiment, The figure which shows an example of the virtual observation environment used in the case of the proof image generation of 1st Embodiment, The figure which shows the example of the illumination intensity distribution in the virtual observation environment of 1st Embodiment, Block diagram showing the configuration of the soft proof system in the second embodiment, A flowchart showing gloss component identification processing in the second embodiment, Block diagram showing the configuration of the soft proof system in the third embodiment, FIG. 10 is a diagram showing various LUT examples used in the third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments do not limit the present invention related to the scope of claims, and all combinations of features described in the present embodiments are essential for the solution means of the present invention. Is not limited.

  The present invention performs the following processing for each pixel of image data to be proofed in an image processing apparatus that performs soft proofing of printed matter under observation illumination. First, the color value of the diffuse reflection component of the observation illumination light by the printed matter having the pixel value is specified (diffusion component specifying process). Further, the recording material to be deposited on the outermost surface of the printed material of the pixel is specified (recording material specifying process), the color value of the specular reflection component of the observation illumination light by the printed material of the specified recording material, and the variable reflection characteristics thereof (Glossy component identification processing, variable angle characteristic identification processing). Then, a proof color is calculated from the color value of the diffuse reflection component, the color value of the regular reflection component, and the variable reflection characteristic, and a proof image is generated (proof image generation processing). By displaying the proof image on the monitor, the glossy color depending on the recording material can be faithfully reproduced.

<First Embodiment>
In the present embodiment, the configuration and processing of a soft proof system that displays an image to be printed on a color monitor and confirms the print finish before actually printing with the printing apparatus will be described. In the present embodiment, four basic color inks including cyan, magenta, yellow, and black pigments are assumed as recording materials used in the printing apparatus, and the color or data of the color and the hue are represented by C, M. , Y, K, etc. That is, C represents cyan or its data or hue, M represents magenta or its data or hue, Y represents yellow or its data or hue, and K represents black or its data or hue. . Needless to say, the ink color and the number of inks used in the printing apparatus are not limited to this example.

System Configuration FIG. 1 is a block diagram showing the configuration of the soft proof system in this embodiment. The soft proof system according to the present embodiment includes an image processing apparatus 100 that generates display data by specifying a diffuse reflection component and a regular reflection component from input image data, display data input from the image processing apparatus 100, The image display device 110 displays a GUI and the like. The image display device 110 is a color monitor such as a CRT or a liquid crystal display. In addition, as a system configuration in the present embodiment, there are various components other than the above, but a description of a configuration that is not the main point of the present invention is omitted.

  In the image processing apparatus 100, first, from the image data input by the image input unit 101, the diffuse reflection component (hereinafter referred to as diffusion component) is diffused by the diffusion component specifying unit 102, and the type of ink deposited on the outermost surface by the surface ink specifying unit 103 Is specified for each pixel. Next, in accordance with the specified ink type of the surface, the specular reflection component (hereinafter referred to as gloss component) is obtained by the gloss component identification unit 104, and the variable angle reflection characteristic (hereinafter referred to as variable angle characteristic) by the variable angle characteristic identification unit 105. Identify. Finally, the proof image generation unit 106 generates a proof image based on the diffusion component, the gloss component, and the angle change characteristic, and converts the generated proof image into image data for display.

  Hereinafter, the proof image generation process in the present embodiment will be described in detail. First, FIG. 2 shows the relationship between the diffusion component, the gloss component, and the angle change characteristic. This figure shows how light (incident light) 202 incident on the printed material 203 from the light source 201 is reflected and light is emitted in multiple directions, and the difference in intensity depending on the emission direction is expressed by the length of the arrow. Yes. In the figure, the intensity of light 204 reflected in the vertical direction of the printed matter 203 is weak because the illumination image is not reflected, but the light 205 reflected in the regular reflection direction of the incident light 202 is reflected in the illumination image. Strength increases. In the present embodiment, the reflected light 204 that is reflected in the vertical direction of the printed matter 203 and does not reflect the illumination image is defined as a diffusion component, and the reflected light 205 in the regular reflection direction of the incident light 202 is defined as a gloss component. Also, the reflection intensity characteristic that changes depending on the reflection direction, indicated by the dotted line 206 in FIG. Reference numerals 207 and 208 are measuring instruments for measuring the reflected lights 204 and 205, respectively.

  Next, the operation of each processing unit constituting the image processing apparatus 100 of the present embodiment will be described in detail.

Image Input Processing In the image input unit 101, image data similar to that input to a printing apparatus that actually performs printing by an application is input in response to a user instruction. Here, the image data is, for example, 1-bit binary data in which dot on / off is defined for each CMYK ink, but the image data is not limited to this example, and is converted to CMYK 1-bit binary data. I can do it. Therefore, for example, an HT processing unit for converting CMYK multi-value data into binary data by halftone (HT) processing similar to that of the printing apparatus may be provided. In addition, a color separation processing unit that converts RGB multi-value data into CMYK multi-value image data may be provided.

  The image data input from the image input unit 101 is input to the diffusion component specifying unit 102 and the surface ink specifying unit 103. Hereinafter, an operation in each processing unit after image data is input will be described.

Diffusion component identification process The diffusion component identification unit 102 obtains XYZdiff, which is a diffusion component (XYZ value) corresponding to the value of each pixel of the input image data, from a lookup table (LUT) held in advance in the interior. . FIG. 3 (a) shows an example of this diffusion component LUT. The diffusion component LUT is created in advance as follows. First, a chart obtained by outputting specific image data under the same printing conditions as a printing apparatus that outputs a printed material to be reproduced is prepared. Then, for the chart, the same observation conditions as when observing the printed material to be reproduced, that is, the color value (XYZ value) of the diffusion component by the same observation illumination light is measured, and the diffusion component LUT is created based on the measurement result To do. As the specific image data, for example, image data on which 16 colors combining ON and OFF of four CMYK dots are printed is used. Further, the color measurement of the diffusion component is performed according to a 45/0 geometric condition such as the light source 201, the printed material 203, and the measuring device 207 shown in FIG. Even if the diffusion component LUT is not held in advance, the user may input the colorimetric value of the chart output by the printing apparatus and create the LUT based on the colorimetric value.

  The acquired diffusion component XYZdiff is input to a proof image generation unit 106 described later.

Surface ink identification process The surface ink identification unit 103 identifies the type of ink that accumulates on the outermost surface at each position of the printed matter output by the printing device, based on the input CMYK image data and the printing order for each color. Ink identification processing is performed. Here, it is assumed that the ink printing order is the order of K, C, M, and Y.

  FIG. 4 shows a flowchart of the surface ink specifying process in the present embodiment. In this processing, all the pixels recorded in the image data are scanned in order, but the scanning order is not limited. The type of ink on the top surface is specified for each selected pixel, and the variable Nij {i = 0 to X-1, j = 0 to Y-1} indicating the ink type at the pixel position (i, j) Record the ink ID. Here, the surface ink ID is a code for identifying each color. In this embodiment, Y = 1, M = 2, C = 3, and K = 4, and when the ink is not white and the paper is white. Records 0. X represents the number of pixels in the main scanning direction of the image, and Y represents the number of pixels in the sub scanning direction.

  In FIG. 4, for the selected pixel, first, in S401, it is determined whether or not the Y signal value is 1 indicating dot ON. If the Y dot is on, the process proceeds to S402 and Nij is set to 1. If it is off, the process proceeds to S403. In S403, as in S401, it is determined whether or not the M signal value is 1 indicating dot on. If the M dot is on, the process proceeds to S404 and Nij is set to 2. If it is off, the process proceeds to S405. Similarly, in S405, it is determined whether or not the C signal value is 1 indicating dot ON. If the C dot is on, the process proceeds to S406 and Nij is set to 3. If it is off, the process proceeds to S407. Similarly, in S407, it is determined whether or not the K signal value is 1 indicating dot on. If the K dot is on, the process proceeds to S408 and 4 is set in Nij. On the other hand, if the K dot is off, it is a paper white area where there is no ink to be hit, so the process proceeds to S409 and 0 is set to Nij.

  By the above processing, the outermost ink type for each pixel is specified. Needless to say, the specification of the surface ink is not limited to the above processing order. Since it is only necessary to be able to specify the type of surface ink, for example, if the ink printing order is K, Y, M, and C, it is only necessary to confirm dot on / off in the order of C, M, Y, and K. In this embodiment, the case where each color is a single pass and the print head is scanned in one direction has been described as an example. However, the image forming order is not limited to the above example. For example, even in the case of single pass, if the scanning direction of the print head is bidirectional, the final printed ink may be specified for each pixel in consideration of the printing order for each scanning direction. In the case of multi-pass, the final printed ink may be specified for each pixel in consideration of the pass mask for each scan and the scan direction of the print head. Further, the ink having the most dominant area on the outermost surface may be specified in consideration of ink spreading, dot size, and landing fluctuation.

  The variable Nij in which the type of the outermost ink is recorded as described above is input to the glossy component specifying unit 104 and the variable angle characteristic specifying unit 105.

● Glossy component identification processing The glossy component identification unit 104 obtains the glossy component XYZ values XYZSpec corresponding to the ink type of the outermost surface recorded in Nij input from the surface ink identification unit 103 from the LUT that holds it in advance. To do. FIG. 3 (b) shows an example of the gloss component LUT. The gloss component LUT is created based on values measured in advance in the same manner as the diffusion component LUT used in the diffusion component specifying unit 102. That is, from the color value (XYZ value) of the specular reflection component measured by the same observation illumination light as observed during the observation of the printed material to be reproduced, measured for the chart output under the same printing conditions as the printing device that outputs the printed material to be reproduced, Create a gloss component LUT. As specific image data, a single patch of each ink, for example, image data on which four single-color patches are printed for CMYK four colors is used. Further, the color measurement of the gloss component is performed at five points obtained by adding paper white to the above-described four colors under the 45/45 geometric condition, for example, as in the light source 201, the printed matter 203, and the measuring device 208 shown in FIG. Even if the gloss component LUT is not stored in advance, the user may input the colorimetric value of the chart output by the printing apparatus and create the LUT based on the colorimetric value.

  The acquired gloss component XYZSpec is input to a proof image generation unit 106 described later.

Deflection characteristic identification processing The deflection characteristic identification unit 105 corresponds to the outermost ink type recorded in Nij input from the surface ink identification unit 103 and corresponds to the light emission angle k. (k = −45 to 45) is acquired from the LUT held in advance inside. FIG. 3 (c) shows an example of this variable angle characteristic LUT. The change-angle characteristic LUT is created in advance from the colorimetric values under the same observation illumination as when observing the printed material to be reproduced, for the chart output under the same printing conditions as the printing apparatus that outputs the printed material to be reproduced. As the specific image data, image data on which four color patches of CMYK are printed is used as in the above-described gloss component color LUT. In the measurement of the variable angle characteristic, for example, the light source 201 and the printed material 203 are fixed in FIG. 2, and the luminance is measured by changing the emission angle k as in the measuring device 207 and the measuring device 208. Luminance Yk {k = −45 to 45} obtained by measuring the printed material 203 (chart), and luminance Ywk {k = −45 to 45} obtained by measuring the diffuse reflector similarly instead of the printed material 203 } Is used to obtain the deflection characteristic Pk {k = −45 to 45} from the following equation (1).

Pk = Yk / Ywk (1)
As can be seen from the equation (1), the angle changing characteristic indicates the ratio of the diffusion component and the gloss component according to the light emission angle k.

  In this embodiment, an example is shown in which only the variable angle characteristic when the incident angle is 45 degrees is retained, but the variable angle characteristic with the incident angle variable may be retained. Further, the variable angle characteristic may be held as XYZ values instead of luminance. Alternatively, a value measured by the user may be input, and the bend angle characteristic LUT may be created based on the measured value. Further, the range of the emission angle is not limited to the above example, and for example, a variable angle characteristic in a range of −90 to 90 degrees may be used.

  The obtained variable angle characteristic Pk is input to a proof image generation unit 106 described later.

Proof Image Generation Processing The proof image generation unit 106 first arranges illumination and printed matter in the virtual space, and calculates the correspondence between the printed matter and the reflected illumination. Next, the intensity of the reflected illumination (reflection intensity) is calculated based on the calculated correspondence relationship and the variable angle characteristic Pk. Finally, a proof color is calculated from the diffusion component XYZdiff and the glossy component XYZSpec according to the reflection intensity.

  FIG. 5 shows a flowchart of proof image generation processing in the present embodiment. First, in S501, an environment (virtual observation environment) for observing the printed matter in the virtual space is created. For example, as shown in FIG. 6 (a), first, a virtual space 601 in which objects such as walls, ceilings, and floors are arranged is created. Next, a virtual printed material 611 and a virtual viewpoint 613 are set at the center of the virtual space 601. Finally, virtual illumination 612 is arranged on the ceiling of the virtual space 601.

  The ceiling portion of the virtual space 601 is divided into a plurality of areas as shown in FIG. 7 (a), and holds the illumination intensity Lij {i = 0 to X-1, j = 0 to Y-1} for each area. . X represents the number of areas in the main scanning direction when detecting the illumination intensity on the ceiling, Y represents the number of areas in the sub-scanning direction, and FIG. 7A shows an example where X = 10 and Y = 8. A virtual illumination 612 held in advance by the proof image generation unit 106 is disposed on the ceiling. Here, FIG. 7 (b) shows an example of the virtual illumination 612 having two lines as shown in FIG. 6 (a). FIG. 7 (b) creates a luminance distribution with the area size shown in FIG. 7 (a) as the virtual illumination 612 based on a value obtained by measuring the luminance distribution of a predetermined illumination in advance. FIG. 7 (c) shows an example of luminance distribution when the virtual illumination 612 shown in FIG. 7 (b) is arranged on the ceiling shown in FIG. 7 (a). In FIG. 7C, it is assumed that the area where the virtual illumination 612 is not arranged remains in the initial state (illumination intensity 0). In the present embodiment, an example in which the virtual space and the virtual illumination are stored in advance is shown. However, for example, a virtual space may be constructed by inputting a CG model designated by the user.

  When the virtual observation environment is constructed in S501 as described above, the proof color is calculated in S502 to S504 for each pixel of the virtual printed material 611.

  In S502, the illumination intensity L of the ceiling area reflected on the pixels on the selected virtual printed matter 611 is specified. Here, FIG. 6B shows a cross section of the virtual space 601. In FIG. 6B, if the selected pixel on the virtual printed matter 611 is a point G, the point G includes a ceiling portion (point Q) in the virtual space 601 in the vertical upward direction of the point G. When the intersection point between the normal vector of the virtual printed matter 611 and the ceiling is a point P, the distance z from the point P to the point Q can be calculated using the following equation (2).

z ＝ D / (tanθt)… (2)
In Equation (2), D represents the distance between the ceiling and the point G, and θt represents the angle formed between the perpendicular from the ceiling at the point G and the normal vector from the virtual printed material 611. In the present embodiment, θt is fixed to 45, but this can be made variable according to a user instruction, for example. In order to make θt variable, it is only necessary to hold the variable angle characteristic Pk corresponding to the changed θt.

  By calculating the distance z from the point P to the point Q as described above, the illumination intensity L of the area reflected in the selected pixel (point G) can be specified from the ceiling luminance distribution shown in FIG. .

  Next, in S503, the reflected illumination intensity is based on the illumination intensity L identified in S502, the angle θe formed by the normal vector of the virtual printed material 611 and the virtual viewpoint 613, and the deflection characteristic Pk (k = −45 to 45). SpecStrength is calculated from the following equation (3).

SpecStrength ＝ L × Pθe… (3)
In the present embodiment, the reflected illumination intensity is expressed as a one-dimensional variable SpecStrength, but it may be a multidimensional variable. For example, the intensity corresponding to each value of XYZ may be calculated.

  Next, in S504, the proof color XYZout is calculated based on the diffusion component XYZdiff and the gloss component XYZSpec input from the diffusion component specifying unit 102 and the gloss component specifying unit 104, and the reflected illumination intensity SpecStrength calculated in S503. This calculation follows the following formula (4).

Xout = (Xspec−Xdiff) × SpecStrength + Xdiff
Yout ＝ (Yspec−Ydiff) × SpecStrength + Ydiff… (4)
Zout = (Zspec−Zdiff) × SpecStrength + Zdiff
The above-described proof color calculation processing in S502 to S504 is executed for each pixel of the virtual printed matter 611. When the processing for all the pixels is completed, the process goes out of the loop and proceeds to S505.

  In S505, the proof color calculated in S504 is converted into a data format that can be displayed on the image display device. In the present embodiment, an example of performing conversion from XYZ values to sRGB values is shown. The proof image generation unit 106 holds, as an XYZdisply value, an XYZ value obtained by measuring a screen displayed in advance when a value of sRGB = 255, 255, 255 is input to the image display device. In S505, based on the XYZdisply value, XYZout ′ obtained by normalizing the proof color XYZout calculated in S504 is calculated according to the following equation (5).

Xout '= Xout / Xdisplay
Yout '＝ Yout / Ydisplay… (5)
Zout '= Zout / Zdisplay
If XYZout ′ after normalization exceeds 1, that is, exceeds the color gamut that can be expressed by the image display device, it is within the expressible range using a well-known range compression method.

  Next, an sRGB value for image display device input is calculated from XYZout ′ using the following equation (6).

  When the conversion to sRGB values is completed for all pixels, the created display image is input to the image display device.

  As described above, according to the present embodiment, the gloss color corresponding to the type of ink on the surface of the printed material is specified by preliminarily holding the color of the gloss component corresponding to the recording material, and the conventional diffusion component In addition, it is possible to reproduce glossy coloring according to the recording material. Therefore, it is possible to perform a simulation more faithful to the actual product, which reproduces the color of the printed matter itself and the glossy color due to the reflection of illumination on the printed matter.

<Second Embodiment>
Hereinafter, a second embodiment according to the present invention will be described. In the first embodiment described above, an example in which the LUT (gloss component LUT, angle change characteristic LUT) for specifying the gloss component XYZSpec and the angle change characteristic Pk from the type of ink on the surface of the printed material is stored in advance is shown. In the second embodiment, an example in which each of the gloss component XYZSpec and the angle change characteristic Pk is specified from the refractive index of the outermost ink will be described.

  FIG. 8 is a block diagram showing the configuration of the soft proof system in the second embodiment. In the figure, the same reference numerals are given to the same components as those in FIG. 1 shown in the first embodiment, and the description thereof will be omitted. The image processing unit 200 according to the second embodiment is characterized by having a gloss component specifying unit 801, an ink characteristic holding unit 802, and a variable angle characteristic specifying unit 803.

Gloss Component Identification Processing The gloss component identification unit 801 identifies light reflected from the interface between air and the outermost ink, that is, the gloss component XYZSpec, from the refractive index and Fresnel equation for each wavelength of the recording material. Hereinafter, this gloss component specifying process will be described with reference to the flowchart of FIG.

  According to FIG. 9, the gloss component XYZSpec is calculated in S902 to S903 for each pixel of the input image data. First, in S901, the refractive index Ni {i = 380 to 780} for each wavelength, which is the optical characteristic value of the surface ink specified by the surface ink specifying unit 103, is acquired from the ink property holding unit 802. Here, an example is shown in which the refractive index of a wavelength of 380 nm to 780 nm is used in increments of 10 nm. However, the refractive index is not limited to this example, and the wavelength range may be further widened, and increments may be made to reduce the number of data. It may be rough. Further, a configuration may be adopted in which the refractive index of the ink is input by the user.

  Next, in S902, the spectral reflectance when the geometric condition is 45/45 is specified based on the refractive index for each wavelength acquired in S901. This geometric condition is the same as the geometric condition when the gloss component is previously acquired by colorimetry in the first embodiment. Then, the refractive index of air is 1, the incident angle of light is θo, the refractive index of ink is Ni, the refractive angle of incident light is θi = 45, and the reflectance Ri {i = 380 to 780} is expressed as the Fresnel equation. It is calculated by the following applied formula (7).

  Next, in S903, the gloss component XYZSpec of the reflected light is specified based on the spectral reflectance Ri at the interface between the air and the surface ink calculated in S902 and the spectral distribution of illumination held in advance. The gloss component XYZSpec specified here is input to the proof image generation unit 106 as in the first embodiment. In the second embodiment, the case where the illumination is non-polarized has been described as an example. However, the spectral reflectance Ri can be obtained based on the Fresnel equation considering the case where the illumination is non-polarized.

Deflection characteristic identification processing Deflection characteristic identification unit 803 identifies, for each reflection angle, light reflected at the interface between air and the outermost ink from the refractive index and Fresnel equation for each wavelength of the recording material. That is, as with the glossy component specifying unit 804, first, the refractive index Ni {i = 380 to 780} for each wavelength of the surface ink specified by the surface ink specifying unit 103 is acquired from the ink characteristic holding unit 802. Next, the reflectance Rik {i = 380 to 780, k = −45 to 45} when the light incident angle formula θi is changed from −45 to 45 is calculated from the above formula (7). Then, XYZk {k = −45 to 45} which is an XYZ value for each incident angle of light is calculated from the calculated reflectance Rik and the spectral distribution of illumination held in advance. From the calculated Y value of XYZk and Ywk {k = −45 to 45} when using a diffuse reflector that is held in advance, the angle variation characteristic Pk {k = −45 to 45} is obtained using equation (1). Ask for. The variable angle characteristic Pk specified in this way is input to the proof image generation unit 106 as in the first embodiment.

  As described above, according to the second embodiment, the glossy color can be specified according to the ink refractive index on the surface of the printed material, and the simulation of reproducing the glossy color can be performed as in the first embodiment.

<Third embodiment>
The third embodiment according to the present invention will be described below. The third embodiment is characterized in that subsequent processing is switched according to the format of the input image. FIG. 10 is a block diagram showing the configuration of the soft proof system in the third embodiment. In the figure, the same reference numerals are given to the same components as those in FIG. 1 shown in the first embodiment, and the description thereof will be omitted. The image processing unit 300 according to the third embodiment includes an input format determination unit 1001, a diffusion component specification unit 1002, a gloss component specification unit 1003, and a variable angle characteristic specification unit 1004. Each of the diffusion component specifying unit 1002, the glossy component specifying unit 1003, and the variable angle characteristic specifying unit 1004 holds in advance a plurality of optical characteristics corresponding to a plurality of data types. Then, according to the data type of the input pixel determined by the input format determination unit 1001, which optical characteristic is used is switched. Hereinafter, detailed operations of each unit will be described.

Input format determination processing In the input format determination unit 1001, whether or not the input image input from the image input unit 101 is print data that has already been subjected to HT processing, that is, whether or not it is CMYK binary data. Determine whether. If it is CMYK binary data, the image data is input to the diffusion component specifying unit 1002 and the surface ink specifying unit 103 as in the first embodiment. Since processing when binary image data is input is the same as in the first embodiment, description thereof is omitted.

  On the other hand, if the input image data is not CMYK binary data, the image data is input to the diffusion component specifying unit 1002, the gloss component specifying unit 1003, and the variable angle characteristic specifying unit 1004. Hereinafter, a case where RGB 8-bit multi-value data is input as image data that is not a CMYK binary value will be described as an example.

Diffusion component identification processing When the diffusion component identification unit 1002 processes RGB multilevel data in addition to the first diffusion component LUT that is referred to when performing the same processing as the first embodiment on CMYK binary data The second diffusion component LUT referred to is held. When RGB multilevel data is input, a diffusion component XYZdiff corresponding to the value of each pixel is acquired from the second diffusion component LUT by interpolation. Here, FIG. 11 (a) shows an example of the second diffusion component LUT for RGB multilevel data. Similar to the first diffusion component LUT, the second diffusion component LUT is created by measuring the XYZ values of the chart. As this chart data, for example, patch data composed of pixel values of representative points (total of 729 colors in 9 divisions) obtained by dividing the range from RGB = (0,0,0) to (255,255,255) at equal intervals is used. . Then, the color measurement is performed under a 45/0 geometric condition using the color measuring device 207 in FIG. If the input RGB multivalued data does not match the representative point held by the second diffusion component LUT, the diffusion component XYZdiff is acquired by a well-known interpolation operation using the colorimetric values of the surrounding representative points. To do. The acquired diffusion component XYZdiff is input to the proof image generation unit 106.

Gloss component identification processing The gloss component identification unit 1003 receives the RGB input in addition to the first gloss component LUT for the variable Nij indicating the outermost ink type input from the surface ink specification unit 103 as in the first embodiment. It holds a second gloss component LUT that is referred to when processing multi-value data. When RGB multilevel data is input, the gloss component XYZSpec corresponding to the value of each pixel is acquired from the second gloss component LUT by interpolation. Here, FIG. 11 (b) shows an example of the second gloss component LUT for RGB multi-value data. The second gloss component LUT is created by measuring the XYZ values of the chart in the same manner as the second diffusion component LUT. This chart data is also representative point values in RGB similar to the second diffusion component LUT, and the color measurement is performed under a 45/45 geometric condition using the colorimeter 208 in FIG. If the input RGB multivalued data does not match the representative point held by the second glossy component LUT, the glossy component XYZSpec is obtained by a well-known interpolation operation using the colorimetric values of the surrounding representative points. To do. The acquired gloss component XYZSpec is input to the proof image generation unit 106.

Deflection characteristic identification processing The deflection characteristic identification unit 1004 is input in addition to the first variation angle characteristic LUT for the variable Nij indicating the outermost surface ink type input from the surface ink identification unit 103 as in the first embodiment. The second variable angle characteristic LUT which is referred to when processing the processed RGB multi-value data is held. When RGB multi-value data is input, the variable angle characteristic Pk (k = −45 to 45) corresponding to the value of each pixel is acquired from the second variable angle characteristic LUT by interpolation. Here, FIG. 11 (c) shows an example of the second variable angle characteristic LUT for RGB multi-value data. Similarly to the second diffusion component LUT, the second variable angle characteristic LUT is created by measuring the XYZ values of the chart. This chart data and its colorimetric method are the same as those of the second diffusion component LUT. The acquired gloss component XYZSpec is input to the proof image generation unit 106.

  Note that the processing after the proof image generation unit 106 is the same as that in the first embodiment, and thus the description thereof is omitted.

  In the third embodiment, two types of input image data, CMYK binary data and RGB multi-value data, are considered. However, classification into other data types such as CMYK multi-value data is considered. It is also possible to do. That is, it is only necessary that each LUT is created for each data type and can be used by adaptively switching.

  As described above, according to the third embodiment, it is possible to perform a simulation in which glossy coloring is reproduced, similarly to the first embodiment, regardless of the format of the input image data.

<Other embodiments>
In each of the above-described embodiments, an example in which the gloss component and the angle change characteristic are estimated from the type of the surface ink has been shown, but the characteristics of the underlying ink or paper may be considered.

  Further, although an example in which the XYZ value of the proof color is converted into the sRGB value for display according to the above equation (4) has been shown, a conversion equation to another display format (for example, AdobeRGB) may be used. Further, although an example in which the angle change characteristic is specified according to the type of surface ink has been shown, the angle change characteristic may be specified using a well-known CG model such as a Phong model.

  Further, although an example has been shown in which the gloss component is predicted by specifying one ink type on the outermost surface for each pixel, the present invention is not limited to this example. For example, from the ink area ratio CMYKrate occupying the pixel and the gloss component XYZspec_CMYK of each color, the gloss component XYZspec ′ due to ink color mixture may be calculated using the following equation (8).

Xspec '= Crate ・ X (spec_C) + Mrate ・ X (spec_M) + Yrate ・ X (spec_Y) + Krate ・ X (spec_k)
Yspec '= Crate ・ Y (spec_C) + Mrate ・ Y (spec_M) + Yrate ・ Y (spec_Y) + Krate ・ Y (spec_k)… (8)
Zspec '= Crate ・ Z (spec_C) + Mrate ・ Z (spec_M) + Yrate ・ Z (spec_Y) + Krate ・ Z (spec_k)
In each of the above embodiments, it is assumed that the ink area ratio and the XYZ value are linear. However, the mixed gloss component XYZspec ′ may be calculated in consideration of the nonlinearity of the area ratio and the XYZ value. good.

  In addition, an example of specifying glossy color from the type of surface ink for each pixel of input image data was shown, but the average value of glossy color within a certain area is specified from the combination of surface ink type for each pixel You may make it do.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and the computer of the system or apparatus (or CPU, MPU, etc.) reads the program. It is a process to be executed.

Claims (12)

An image processing apparatus that performs soft proofing of printed matter under observation illumination,
An input means for inputting image data to be proofed;
For each pixel of the image data, a diffusion component specifying means for specifying a color value of a diffuse reflection component of observation illumination light by a printed matter having a value of the pixel;
Recording material specifying means for specifying the recording material deposited on the outermost surface of the printed matter for each pixel of the image data;
Gloss component specifying means for specifying the color value of the regular reflection component of the observation illumination light by the printed material of the specified recording material;
Proof image generation means for generating a proof image by calculating a proof color from the color value of the specified diffuse reflection component and the color value of the regular reflection component for each pixel of the image data;
An image processing apparatus comprising: Furthermore, it has an angle change characteristic specifying means for specifying an angle change reflection characteristic of the printed material of the specified recording material,
2. The image processing according to claim 1, wherein the proof image generation unit calculates the proof color from a color value of the diffuse reflection component, a color value of the regular reflection component, and the variable angle reflection characteristic. apparatus.   3. The image processing apparatus according to claim 1, wherein the recording material specifying unit specifies the recording material based on a recording material overlapping order in the printing of the image data.   The diffuse component specifying means specifies a color value of the diffuse reflection component from a measurement result of the diffuse reflection component obtained by measuring a printed matter having a predetermined pixel value in advance under the observation illumination. The image processing apparatus according to claim 1. Furthermore, it has holding means for holding the optical characteristics of the recording material,
5. The gloss component specifying unit specifies a color value of the regular reflection component using optical characteristics of the recording material held by the holding unit. An image processing apparatus according to 1.   6. The image processing apparatus according to claim 5, wherein the holding unit holds a measurement result of a specular reflection component obtained by measuring a printed material of the recording material alone under the observation illumination in advance.   6. The image processing apparatus according to claim 5, wherein the holding unit holds a refractive index for each wavelength of the recording material. Furthermore, it has a determination means for determining the data type for each pixel of the image data,
The diffusing component specifying means and the gloss component specifying means hold in advance measurement results under the observation illumination for the printed matter of each pixel value for a plurality of data types, and according to the data types determined by the determining means 5. The image processing apparatus according to claim 1, wherein the color value of the diffuse reflection component and the color value of the regular reflection component are specified using the measurement result.   9. The image processing apparatus according to claim 8, wherein the determination unit determines whether or not the data is binary data for each pixel of the image data.   10. The image processing apparatus according to claim 1, wherein the proof image generation unit generates the proof image as a printed matter arranged in a virtual space. An image processing method in an image processing apparatus that includes an input unit, a diffusion component specifying unit, a recording material specifying unit, a gloss component specifying unit, and a proof image generating unit, and performing soft proofing of a printed matter under observation illumination,
The input means inputs image data to be proofed,
The diffusion component specifying means specifies, for each pixel of the image data, a color value of a diffuse reflection component of observation illumination light by a printed matter having a value of the pixel,
The recording material specifying means specifies the recording material deposited on the outermost surface of the printed matter for each pixel of the image data,
The gloss component specifying means specifies the color value of the specular reflection component of the observation illumination light by the printed material of the specified recording material;
The proof image generating means generates a proof image by calculating a proof color from the color value of the diffuse reflection component and the color value of the specular reflection component specified for each pixel of the image data. Processing method.   11. A program for causing a computer to function as each unit of the image processing apparatus according to claim 1 when executed by the computer.

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