Method for generating a coloring evaluation image and generation program

Abstract

To facilitate evaluation of an entire impression when a metallic paint color is painted on a coating surface of an industrial product or the like.SOLUTION: A generation method of a coating color evaluation image comprises: a spectral reflectance calculation process which calculates a spectral reflectance of a metallic paint color for each prescribed angle from a spectral reflectance of the metallic paint color measured at a plurality of light reception angles; a color measurement value calculation process which calculates a color measurement value for each prescribed angle; a mapping process which associates the observation angle for each prescribed angle for each concentration difference level of a coating surface image; a look-up table generation process which generates a look-up table associated with the color measurement value for each prescribed angle for each concentration difference level of the coating surface image; and a coating color evaluation image generation process which generates a coating color evaluation image in which a pixel of the coating surface image is replaced with a pixel indicating the color measurement value corresponding to the concentration difference level of the pixel on the basis of the look-up table.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for generating a colored evaluation image and a generation program.

Background Art

[0002] For the colored coating of paints applied to industrial products such as automobiles, especially the metallic colored coating whose appearance changes depending on the viewing angle, it is difficult to perform color evaluation before applying it to actual industrial products.

[0003] Since the main surface and the sub-surface of the color evaluation panel described in Patent Document 1 have different curvatures, by applying a metallic colored coating, it is possible to more accurately perform color evaluation including the highlights and shades of the metallic colored coating.

[0004] If there is three-dimensional CAD shape data of an industrial product, color evaluation can be performed by visualizing the industrial product with a metallic colored coating through computer simulation. However, in many cases, such as when performing design evaluation of an industrial product in the planning stage of the industrial product, the three-dimensional CAD shape data cannot be obtained.

[0005] On the other hand, regarding the metallic colored coating whose appearance changes depending on the viewing angle, for a panel on the plane to which the metallic colored coating is applied, light is irradiated from a specific angle, and from the spectral reflectance obtained by receiving the reflected light at a plurality of angles, it is known that the spectral reflectance at various light receiving angles can be calculated.

[0006] The method for determining the optical properties of a metallic coating film described in Patent Document 2 can predict the arbitrary spectral reflectance at a wide range of angles from the highlight to the shade of the metallic colored coating.

[0007] The metallic color determination device described in Patent Document 3 can create a Color Simulation image (hereinafter referred to as "CS image"), which is a computer simulation image that can be used as a digital palette, from the spectral reflectance obtained using the method described in Patent Document 2. The CS image includes computer simulation images of metallic colors observed from a wide range of angles from highlight to shade. By using the CS image, for example, a designer can evaluate the coloring of metallic colors according to the observation angle at the planning stage of industrial products.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, the painted surfaces of actual industrial products have different three-dimensional shapes for each product, and the change in shadows on the painted surface is different for each industrial product. Since the CS image does not consider the change in shadows on the painted surface, it is difficult to evaluate the overall impression when a metallic color is painted on the painted surface of an actual industrial product from the CS image.

[0010] In view of the above circumstances, an object of the present invention is to provide a method and a program for generating a coloring evaluation image that facilitate the evaluation of the overall impression when a metallic color is painted on the painted surface of an industrial product.

Means for Solving the Problems

[0011] In order to solve the above problems, the present invention proposes the following means. A method for generating a painted color evaluation image according to a first aspect of the present invention is a method for generating a painted color evaluation image from a painted surface image that displays a painted surface, comprising: a spectral reflectance calculation step of calculating the spectral reflectance of the metallic painted color at each predetermined angle within an observation angle range from the spectral reflectances of the metallic painted color measured at a plurality of light reception angles; a colorimetric value calculation step of calculating a colorimetric value at each predetermined angle within the observation angle range based on the spectral reflectance; a mapping step of associating an observation angle at each predetermined angle within the observation angle range with each gradation level of the painted surface image; a look-up table generation step of generating a look-up table in which the colorimetric values at each predetermined angle within the observation angle range are associated with each gradation level of the painted surface image; and a painted color evaluation image generation step of generating a painted color evaluation image by replacing pixels of the painted surface image with pixels indicating the colorimetric value corresponding to the gradation level of the pixels, based on the look-up table.

[0012] A program for generating a painted color evaluation image according to a second aspect of the present invention is a program for causing a computer to generate a painted color evaluation image from a painted surface image that displays a painted surface, comprising: a spectral reflectance calculation step of calculating the spectral reflectance of the metallic painted color at each predetermined angle within an observation angle range from the spectral reflectances of the metallic painted color measured at a plurality of light reception angles; a colorimetric value calculation step of calculating a colorimetric value at each predetermined angle within the observation angle range based on the spectral reflectance; a mapping step of associating an observation angle at each predetermined angle within the observation angle range with each gradation level of the painted surface image; a look-up table generation step of generating a look-up table in which the colorimetric values at each predetermined angle within the observation angle range are associated with each gradation level of the painted surface image; and a painted color evaluation image generation step of generating the painted color evaluation image by replacing pixels of the painted surface image with pixels indicating the colorimetric value corresponding to the gradation level of the pixels, based on the look-up table, and causing the computer to execute the steps.

Advantages of the Invention

[0013] According to the method and generation program for generating a painted color evaluation image of the present invention, it is possible to generate a painted color evaluation image that facilitates evaluating the overall impression when a metallic painted color is applied to the painted surface of an industrial product.

Brief Description of the Drawings

[0014]

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Embodiments for Carrying Out the Invention

[0015] (First Embodiment) The first embodiment of the present invention will be described with reference to FIGS. 1 to 7. The method for generating a painted color evaluation image according to this embodiment is a method for generating a painted color evaluation image from a painted surface image that displays a painted surface applied to an industrial product, its model, etc. For example, it is realized by a program for generating a painted color evaluation image executed by a computer capable of executing a program.

[0016] FIG. 1 is a configuration diagram of a painted color evaluation image generation device 100 that executes a program for generating a painted color evaluation image. The painted color evaluation image generation device 100 includes an image input unit 1, an image generation unit 2 capable of executing a program, and an image output unit 3 such as an LCD monitor.

[0017] FIG. 2 is a configuration diagram of the image generation unit 2. The image generation unit 2 is a computer capable of executing a program, having a processor 20 such as a CPU, a memory 21 capable of reading a program, a storage unit 22 capable of storing a program and data, and an input / output control unit 23. The functions of the image generation unit 2 are realized by the processor 20 executing the program provided to the image generation unit 2.

[0018] FIG. 3 is a functional block diagram of the image generation unit 2 when the image generation unit 2 executes a program for generating a painted color evaluation image. The functional blocks of the image generation unit 2 include a spectral reflectance calculation unit 51, a colorimetric value calculation unit 52, a mapping unit 53, a look-up table generation unit 54, and a painted color evaluation image generation unit 55.

[0019] FIG. 4 is a two-dimensional image (photo, illustration, etc.) of an automobile that is the object using the method for generating a painted color evaluation image according to this embodiment. In the following description, the image of the sedan shown in FIG. 4 is referred to as the "sedan image". The sedan image is input to the image generation unit 2 using an image input unit 1 such as a scanner.

[0020] Even when the same metallic paint color is applied to the painted surface, the change in the shadow on the painted surface varies depending on the three-dimensional shape of the painted surface. According to the method for generating a paint color evaluation image according to this embodiment, based on the change in the shadow of a painted surface image (two-dimensional image) that displays the painted surface applied to an industrial product or its model, etc., for example, the overall impression when a metallic paint color is applied to the painted surface of the sedan shown in FIG. 4 can be predicted.

[0021] First, preliminary image processing is performed on the sedan image shown in FIG. 4. From the sedan image, a "painted surface image" is generated by cutting out only the image portion of the actual painted surface. FIG. 5 is a painted surface image generated from the sedan image.

[0022] In this embodiment, the painted surface image is obtained by converting a sedan image, which is a color image, into an 8-bit grayscale image. Note that the painted surface image is not limited to a grayscale image. The painted surface image may be an image composed of luminance values of an image represented by an arbitrary number of bits, such as the Y component of the YUV signal or the G component of the RGB signal (hereinafter referred to as "shading level"). In this embodiment, the shading level is 256 gradations represented by 8 bits.

[0023] In the generation of the painted surface image, it is desirable not to include in the painted surface image portions where the change in the shadow of the painted surface does not change based on the three-dimensional shape of the painted surface itself, for example, portions where the shadow of the side mirror is reflected. This is to accurately predict the change in the shadow on the painted surface based on the three-dimensional shape of the painted surface when a metallic paint color is applied to the painted surface.

[0024] Next, the method for generating a paint color evaluation image according to this embodiment will be described in detail. The method for generating a paint color evaluation image according to this embodiment includes a spectral reflectance calculation step S1, a colorimetric value calculation step S2, a mapping step S3, a look-up table generation step S4, and a paint color evaluation image generation step S5.

[0025] The spectral reflectance calculation unit 51 calculates the spectral reflectance of the metallic paint color for each predetermined angle within the observation angle range (0 degrees to 75 degrees) from the spectral reflectance of the metallic paint color measured at a plurality of light reception angles, using, for example, the method for determining the optical properties of the metallic coating film described in Patent Document 2 cited in the prior art documents (spectral reflectance calculation step S1).

[0026] Figure 6 is an example of the measurement of the spectral reflectance of the metallic paint color. For example, as shown in Figure 6, under the conditions of incident angle: 45 degrees, light reception angles (5 angles): highlight 15 degrees, 25 degrees, face 45 degrees, shade 75 degrees, 110 degrees, the spectral reflectance of the metallic paint color is measured. The metallic paint color is selected, for example, from the auto color chips (Kansai Paint) in the sample book of automotive refinish paints. The selected metallic paint color is measured using, for example, the 5-angle spectrophotometer MA-68II of x-rite.

[0027] Next, the spectral reflectance calculation unit 51 calculates the spectral reflectance of the metallic paint color for each predetermined angle within the observation angle range (0 degrees to 75 degrees) from the measured spectral reflectance at 5 angles. The spectral reflectance calculation unit 51 may derive an equation for calculating the spectral reflectance for each arbitrary angle. In the present embodiment, the predetermined angle is approximately 0.3 degrees (observation angle range / gradation level = 75 degrees / 256 = approximately 0.3 degrees). The predetermined angle is obtained by dividing the observation angle range by the number of gradation levels of the shade. The calculated spectral reflectance is recorded in the memory 21 of the image generation unit 2 together with the corresponding predetermined angle.

[0028] The colorimetric value calculation unit 52 calculates the colorimetric value (metallic color) for each predetermined angle within the observation angle range (from 0 degrees to 75 degrees) based on the spectral reflectance calculated by the spectral reflectance calculation unit 51, using, for example, the method for determining the optical properties of the metallic coating film described in Patent Document 2 cited in the prior art documents (colorimetric value calculation step S2). The colorimetric value calculation unit 52 may derive an equation for calculating the colorimetric value for each arbitrary angle. The calculated colorimetric value is recorded in the memory 21 of the image generation unit 2 together with the corresponding predetermined angle.

[0029] The mapping unit 53 associates the observation angles for each predetermined angle in the observation angle range (0 degrees to 75 degrees) with each gradation level of the painted surface image (mapping step S3). In the present embodiment, gradation level 255 (white) is associated with highlight 0 degrees, and gradation level 0 (black) is associated with shade 75 degrees. The highest gradation level is associated with the smallest angle in the observation angle range, and the lowest gradation level is associated with the largest angle in the observation angle range.

[0030] Next, the observation angles corresponding to each gradation level [0 to 255] are calculated by linear interpolation. Table 1 shows the observation angles corresponding to each calculated gradation level [0 to 255]. The calculated observation angles are recorded in the memory 21 of the image generation unit 2 together with the corresponding gradation levels.

[0031]

Table 1

[0032] The look-up table generation unit 54 generates a look-up table (also referred to as a LUT) that associates the colorimetric values (metallic colors) for each predetermined angle in the observation angle range (0 degrees to 75 degrees) with each gradation level of the painted surface image (look-up table generation step S4). The colorimetric values (metallic colors) for each predetermined angle are the colorimetric values calculated in the colorimetric value calculation step S2 and are, for example, RGB values. Table 2 shows a look-up table in which the colorimetric values are associated with each calculated gradation level [0 to 255].

[0033] Note that the look-up table generation unit 54 may generate a look-up table that replaces the gradation levels near the maximum (for example, almost white [254 to 255]) with values corresponding to white (255 for each of the RGB values if they are RGB values). Pixels with gradation levels near the maximum are likely to be the background or its boundary portion that has nothing to do with the vehicle body, and replacing them with values corresponding to white is preferable from the viewpoint of evaluating the impression of the painted surface.

[0034]

Table 2

[0035] The coloring evaluation image generation unit 55 generates a coloring evaluation image in which the pixels of the painted surface image are replaced with pixels indicating colorimetric values corresponding to the shading levels of the pixels based on a look-up table (coloring evaluation image generation step S5).

[0036] FIG. 7 is a coloring evaluation image generated using the colorimetric values of Toyota 3R3 (Red Metallic Mica) for a sedan car image. From the coloring evaluation image generated from the change (shading level) of the shadow on the painted surface of the painted surface image, the user can predict the overall impression when a metallic paint is applied to the painted surface. Since each pixel of the sedan car image is replaced with a colorimetric value corresponding to the shading level, the user can evaluate the impression when a metallic paint is applied not only for the whole sedan car image but also for each part.

[0037] According to the coloring evaluation image generation method and generation program according to the present embodiment, from the coloring evaluation image generated from the change (shading level) of the shadow on the painted surface of the painted surface image, the user can evaluate the overall impression when a metallic paint is applied to the painted surface together with the impression of the shape.

[0038] As described above, the first embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included. In addition, the components shown in the above-described first embodiment and the modified examples shown below can be configured by appropriately combining them.

[0039] (Second Embodiment) The second embodiment of the present invention will be described with reference to FIGS. 8 to 11. In the following description, for the components common to those already described, the same reference numerals are given and the overlapping description is omitted. The coloring evaluation image generation method according to the second embodiment is different only in the look-up table generation step S4.

[0040] In this embodiment, after generating the look-up table, the look-up table generation unit 54 corrects the look-up table (look-up table correction step).

[0041] For example, when the colorimetric value is an RGB value, and the colorimetric values corresponding to the shading level x are R(x), G(x), and B(x), the corrected colorimetric values R'(x), G'(x), and B'(x) in the corrected look-up table are shown by, for example, Equation 1. f(x) is a correction function.

[0042]

Equation

[0043] FIG. 8 is a diagram showing an example of the correction function f(x). The correction function f(x) is a function that increases quadratically as the shading level x increases in the high shading level region where the shading level x is 100 or more.

[0044] FIG. 9 is a diagram showing a coloring evaluation image generated based on the look-up table before correction and a coloring evaluation image generated based on the look-up table after correction by the correction function f(x) shown in FIG. 8. The coloring evaluation image after correcting the look-up table emphasizes the gloss and three-dimensional feeling of the vehicle body surface more than the coloring evaluation image before correction.

[0045] FIGS. 10 and 11 are diagrams showing a coloring evaluation image generated using colorimetric values of different colorings and a coloring evaluation image generated based on the look-up table after correction by the correction function f(x). In any case, the coloring evaluation image after correcting the look-up table emphasizes the gloss and three-dimensional feeling of the vehicle body surface more than the coloring evaluation image before correction.

[0046] By increasing f(x) in the high density level region where the density level x is 100 or more, without significantly changing the impression of the color tone of the painting itself, the gloss and three-dimensional feeling of the vehicle body surface are more emphasized, and the user can more easily grasp the overall impression when the painted surface is painted with a metallic paint color.

[0047] Note that the above correction function f(x) is an example, and a known correction function for image correction may be appropriately selected and used.

[0048] According to the method and generation program for generating a painted color evaluation image according to the present embodiment, the user can evaluate the overall impression when the painted surface is painted with a metallic paint color together with the impression of the shape by the painted color evaluation image generated from the change (density level) of the shadow of the painted surface of the painted surface image. By correcting the look-up table, it is possible to generate a painted color evaluation image that is easier to understand the overall impression, such as a painted color evaluation image that emphasizes the gloss and three-dimensional feeling.

[0049] As described above, the second embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included. In addition, the components shown in the above-described second embodiment and the modification examples shown below can be configured by appropriately combining them.

[0050] (Modification Example 1) For example, in the above embodiment, the observation angle range was 0 degrees to 75 degrees, but the observation angle range is not limited to this. The observation angle range may be, for example, 0 degrees to 90 degrees.

[0051] Note that the program for generating the painted color evaluation image is recorded on a computer-readable recording medium. The program recorded on this recording medium is read into a computer system and executed. Here, the "computer system" shall include hardware such as an OS and peripheral devices. Also, the "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, CD-ROMs, and storage devices such as hard disks built into a computer system. Furthermore, the "computer-readable recording medium" may include those that dynamically hold a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as volatile memory inside a computer system serving as a server or a client in that case. Also, the above program may be for realizing a part of the aforementioned functions, and may further be capable of being realized in combination with a program already recorded in a computer system, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

Industrial Applicability

[0052] The present invention can be applied to the evaluation of industrial products having a painted surface.

Explanation of Signs

[0053] 100 Painted color evaluation image generation device 1 Image input unit 2 Image generation unit 20 Processor 21 Memory 22 Storage unit 23 Input / output control unit 3 Image output unit S1 Spectral reflectance calculation step S2 Colorimetric value calculation step S3 Mapping step S4 Look-up table step S5 Coloring Evaluation Image Generation Process

Claims

1. A method for generating a painted color evaluation image, which is a simulation image, from a painted surface image, which is a two-dimensional image showing a painted surface, comprising: a spectral reflectance calculation step of calculating the spectral reflectance of the metallic paint color for each predetermined angle in an observation angle range, which is a range of angles for observing the painted surface, from the spectral reflectances of the metallic paint color measured at a plurality of light receiving angles; a colorimetric value calculation step of calculating a colorimetric value for each predetermined angle in the observation angle range based on the spectral reflectance; a mapping step of associating the observation angle for each predetermined angle in the observation angle range with each gradation level of the painted surface image; a look-up table generation step of generating a look-up table in which the colorimetric values for each predetermined angle in the observation angle range are associated with each gradation level of the painted surface image; a painted color evaluation image generation step of generating the painted color evaluation image by replacing the pixels of the painted surface image with pixels indicating the colorimetric values corresponding to the gradation levels of the pixels, based on the look-up table; the look-up table generation step corrects the look-up table, the correction of the look-up table adds the colorimetric value corresponding to the region with a high gradation level, A method for generating a painted color evaluation image.

2. The mapping step is as follows: the highest gradation level is associated with the smallest angle in the observation angle range, the lowest gradation level is associated with the largest angle in the observation angle range The method for generating a painted color evaluation image according to Claim 1.

3. A program for causing a computer to generate a painted color evaluation image, which is a simulation image, from a painted surface image, which is a two-dimensional image showing a painted surface, comprising: a spectral reflectance calculation step of calculating the spectral reflectance of the metallic paint color for each predetermined angle in an observation angle range, which is a range of angles for observing the painted surface, from the spectral reflectances of the metallic paint color measured at a plurality of light receiving angles; a colorimetric value calculation step of calculating a colorimetric value for each predetermined angle in the observation angle range based on the spectral reflectance; a mapping step of associating the observation angle for each predetermined angle in the observation angle range with each gradation level of the painted surface image; A look-up table generation step of generating a look-up table in which the color measurement values for each of the predetermined angles in the observation angle range are associated with each of the shading levels of the painted surface image; A painted color evaluation image generation step of generating the painted color evaluation image in which pixels of the painted surface image are replaced with pixels indicating the color measurement values corresponding to the shading levels of the pixels, based on the look-up table; causing the computer to execute; the look-up table generation step corrects the look-up table; the correction of the look-up table adds the color measurement values corresponding to the regions with high shading levels; A program for generating a painted color evaluation image. **Claim 4** The mapping step is as follows: the highest shading level is associated with the smallest angle in the observation angle range; the lowest shading level is associated with the largest angle in the observation angle range. The program for generating a painted color evaluation image according to claim 3.

Images