Image processing apparatus, image processing method, and program

Abstract

To suitably apply a three-dimensional feeling to an object or a subject that a user wants to reproduce as an image.SOLUTION: An image processing device generates data for forming an image on a recording medium by using a first ink having the different intensity of light reflected in the regular reflection direction with respect to the intensity of the light reflected in the diffusion direction when the light is incident at a prescribed angle with respect to a state of being applied on a medium, and a second ink different from the first ink and having a smaller ratio of the intensity of the light reflected in the regular reflection direction with respect to the intensity of the light reflected in the diffusion direction when the light is incident at the prescribed angle with respect to the state of being applied on the medium in comparison with the first ink, and comprises: first acquisition means which acquires first image data being a printing object; second acquisition means which acquires second image data showing the same subject as the subject of the first image data and expressed under a different geometric condition from the first image data; and first determination means which determines an ink amount of each ink including the first ink and the second ink on the basis of the brightness at each position of the first image data and the second image data.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to an image processing technique for performing image formation using ink that has different brightness depending on observation conditions.

Background Art

[0002] In recent years, metallic ink or glossy ink that contains metal particles and can impart metallic luster onto a recording medium has been used for printing using a recording device or the like. Further, metallic ink or glossy ink is also used in combination with color ink, and various printing methods have been proposed for adding metallic luster to high-quality color printing.

[0003] For example, in Patent Document 1, a three-dimensional effect is imparted to a printed matter by the difference in luster between a portion where metallic ink is used and a portion where it is not used. Further, a method of imparting a three-dimensional effect to a printed matter by performing gradation printing using metallic ink is described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as to what kind of gradation to give, it is either selected from a predetermined pattern or set by the user. For this reason, it has been unknown what kind of gradation expression is suitable for imparting a three-dimensional effect to an object or subject to be reproduced as an image, and there have been cases where a suitable three-dimensional effect cannot be imparted.

[0006] Therefore, an object of the present invention is to suitably impart a three-dimensional effect to an object or subject to be reproduced as an image.

Means for Solving the Problem

[0007] An image processing apparatus according to an aspect of the present invention is an image processing apparatus that generates data for forming an image on a recording medium using a first ink in which the intensity of light reflected in the specular reflection direction is different from the intensity of light reflected in the diffusion direction when light is incident at a predetermined angle with respect to the state applied on the medium, and a second ink that is different from the first ink and has a smaller ratio of the intensity of light reflected in the specular reflection direction to the intensity of light reflected in the diffusion direction when light is incident at a predetermined angle with respect to the state applied on the medium than the first ink, the image processing apparatus comprising: first acquisition means for acquiring first image data to be printed; second acquisition means for acquiring second image data that shows the same subject as the subject of the first image data and is represented under geometric conditions different from those of the first image data; first determining means for determining a declination reflection characteristic indicating the intensity of brightness at each position of an image based on a difference in brightness between the first image data and the second image data; using the declination reflection characteristic determined by the first determining means determination means for determining the ink amount of each ink including the first ink and the second ink. two It is characterized by having.

Advantage of the Invention

[0008] According to the present invention, a three-dimensional effect can be suitably imparted to an object or subject to be reproduced as an image.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not necessarily limit the present invention. Also, not all combinations of features described in this embodiment are essential for the solution means of the present invention.

[0011] <<Embodiment 1>> <Hardware Configuration of Image Processing Apparatus 1> FIG. 1 is a diagram showing the hardware configuration of an image processing apparatus 1. The image processing apparatus 1 is, for example, a computer. The image processing apparatus 1 includes a CPU 101, a ROM 102, a RAM 103, a VC (video card) 104, a general-purpose I / F (interface) 105, a SATA (Serial ATA) I / F 106, and a NIC (network interface card) 107.

[0012] The CPU 101 executes an OS (Operating System) or various programs stored in the ROM 102 or the HDD (Hard Disk Drive) 113, etc., using the RAM 103 as a work memory. Also, the CPU 101 controls each component via the system bus 108. Incidentally, the processing according to the flowchart described later is executed by the CPU 101 after the program code stored in the ROM 102 or the HDD 113, etc. is expanded to the RAM 103. A display 115 is connected to the VC 104. An input device 110 such as a mouse or a keyboard, or an image forming apparatus 111 is connected to the general-purpose I / F 105 via the serial bus 109. A general-purpose drive 114 that reads and writes to the HDD 113 or various recording media is connected to the SATA I / F 106 via the serial bus 112. The NIC 107 performs input / output of information with an external device. The CPU 101 uses various recording media mounted on the HDD 113 or the general-purpose drive 114 as storage locations for various data. The CPU 101 displays a UI (User Interface) screen provided by a program on the display 115 and receives inputs such as user instructions received via the input device 110.

[0013] <Principle of Stereoscopic Sensation> In the present embodiment, the observer is made to perceive a three-dimensional feeling by utilizing the fact that printed matter to which image processing is applied shows different brightness distributions according to the observation conditions.

[0014] Figure 2 is a conceptual diagram explaining the principle related to stereo perception. The plan view (a) of Figure 2 shows the relationship between the light source, the subject, and the camera. Here, the subject is a quadrangular prism, and the normal lines of the surfaces A and B of the subject are inclined at 45° with respect to the directions of the light source and the camera. At this time, if the reflectivities of the surfaces A and B are the same, as shown in the camera image (b) of Figure 2, the brightnesses of the surfaces A and B will be the same. The plan view (c) of Figure 2 represents that the light source has moved in the direction indicated by the arrow from the position of the plan view (a). At this time, the image taken by the camera will be like the camera image (d). Since the light source approaches the direction directly facing the surface B, compared with the camera image (b), the surface B is brighter and the surface A is conversely darker.

[0015] In the conventional two-dimensional print, the surface normal is the same as the vertical direction of the printed matter at any position of the image. Therefore, even if the position of the light source is changed during observation, the brightnesses of the surfaces A and B change in the same way, and the three-dimensional shape cannot be recognized due to the change in brightness as described above. In the present embodiment, reproducing the change in brightness according to the normal of the subject due to the difference in the position of the light source is taken as one element for recognizing the three-dimensional shape in the printed matter.

[0016] Figure 3 is a schematic diagram showing the effect of image processing. In the present embodiment, as illustrated in Figure 2, two scenes with different geometric conditions such as the light source position are input as target images. As shown in Figure 3, the printed matter simulates the change in the geometric conditions of the scene and imparts a three-dimensional feeling by reproducing the target image 1 in one observation environment and the target image 2 in another observation environment. More specifically, in the target image 1, an observation environment where "the main light source does not shine on the printed matter", which is a general image observation environment, is reproduced. In the target image 2, an observation environment where "the main light source is intentionally made to shine on the printed matter" is reproduced.

[0017] When light is incident on the metallic ink at a predetermined angle with respect to the state applied on a medium such as a printed matter, the intensity of the light reflected in the specular reflection direction is different from the intensity of the light reflected in the diffused direction. That is, it has a high directivity in the direction of reflecting light and reflects more light in the specular reflection direction. For this reason, the appearance of a printed matter using metallic ink is greatly affected by the brightness of the image reflected in the specular reflection direction. In the present embodiment, the amount of the metallic ink is changed to control the amount of reflected light in the specular reflection direction at each position of the printed matter. An observer can perceive changes in brightness at different positions of the printed matter by reflecting or removing the light source while tilting the printed matter. As a result, it is possible to perceive as if the lighting on the subject in the printed matter has changed, and a three-dimensional effect can be imparted to the printed matter. On the other hand, for color inks such as CMYK, the ratio of the intensity of the light reflected in the specular reflection direction to the intensity of the light reflected in the diffused direction when light is incident at a predetermined angle with respect to the state applied on the medium is small. Below, the characteristics of the metallic ink and the color ink will be described with reference to FIG. 4.

[0018] FIG. 4 is a schematic diagram showing the angular reflection characteristics in a printed matter using color ink and metallic ink. The angular reflection characteristic is a characteristic showing the difference in brightness under different geometric conditions. In patterns (a) to (i) of FIG. 4, the angular reflection characteristics when using different amounts of color ink and metallic ink are shown. Patterns (a) to (i) show that the amount of color ink increases as the arrow goes to the right. Also, the amount of metallic ink increases as the arrow goes down. The dashed arrow indicates the incident light on the printed matter, and the shape on the printed matter shows the intensity of the light reflected at each angle from the light incident point. The upper left pattern (a) shows the angular reflection characteristics of the paper white without printing ink. This distribution has little bias such as strong reflection in a specific direction, and the change in brightness is small when viewed from any angle. Pattern (c) shows the angular reflection characteristics when printed with only color ink. Similar to pattern (a), there is little bias for each angle, but since the color ink absorbs light, the amount of reflection decreases as the amount of color ink increases. Also, pattern (g) shows the angular reflection characteristics when printed with only metallic ink. Metallic ink has high directivity and reflects strong light in the specular reflection direction. Due to such characteristics, the change in brightness when the observation angle is changed by the same amount from the specular reflection light to the diffusion direction is larger for metallic ink than for color ink. For this reason, when viewed by reflecting the light source, it appears bright according to the brightness of the light source. However, since there is little component diffusing other than the specular reflection direction, it appears dark unless the light source is reflected.

[0019] Both the color ink and the metallic ink can generate intermediate characteristics as in patterns (b) and (d) respectively according to the area gradation. Also, when the color ink and the metallic ink are mixed as in patterns (e), (f), (h), and (i), characteristics obtained by multiplying the respective angular reflection characteristics can be generated. In practice, even in printing with only color ink, it is common to show slightly stronger reflection in the specular reflection direction compared to other directions. However, since the amount of reflection is less than that of metallic ink, it is omitted for easier explanation. Such differences in angular reflection characteristics are modeled by a Bidirectional Reflectance Distribution Function or the like and can be measured with a commercially available BRDF measuring device.

[0020] Figure 5 is a schematic diagram for explaining a mechanism for giving a three-dimensional effect to a printed matter by utilizing the angular reflection characteristics of metallic ink. Figure 5 shows an example in which, on a two-dimensional printed matter, only color ink is used for printing in the area representing surface A, and both color ink and metallic ink are used for printing in the area representing surface B. Here, the brightness of surface A and surface B when observed from angle θ1 is almost the same. On the other hand, when observed from angle θ2, surface B where metallic ink is used reflects strongly in the specular reflection direction and is perceived as brighter than surface A. By associating the change in brightness with the printing amount of metallic ink in this way, the change in brightness when a light source is projected can mimic the change in the geometric conditions of the actual scene, and a three-dimensional effect can be perceived.

[0021] <Logical Configuration of Image Processing Apparatus 1> Figure 6 is a diagram showing the logical configuration of the image processing apparatus 1. The CPU 101 of the image processing apparatus 1 includes a first image acquisition unit 601, a second image acquisition unit 602, a color conversion unit 603, an angular reflection characteristic determination unit 604, a metallic ink amount determination unit 605, a color ink amount determination unit 606, and an output unit 607.

[0022] The first image acquisition unit 601 acquires first image data representing a scene under certain geometric conditions of the subject. The second image acquisition unit 602 acquires second image data. The second image data is image data representing a scene of the same subject as the first image data but under geometric conditions different from those of the first image data. The color conversion unit 603 converts the color information of the first image data and the second image data into tristimulus values XYZ. The declination reflection characteristic determination unit 604 determines the difference in brightness between the two images from the tristimulus values of the first image data and the second image data. The metallic ink amount determination unit 605 determines the metallic ink amount from the difference in brightness between the first image data and the second image data. The color ink amount determination unit 606 determines the color ink amount based on the first image data and the metallic ink amount. The output unit 607 outputs the determined metallic ink amount and color ink amount to the image forming apparatus 111.

[0023] <Configuration of the image forming apparatus 111> FIG. 7 is a configuration diagram of the image forming apparatus 111. The image forming apparatus 111 in the present embodiment is, for example, an inkjet printer that forms an image by recording ink on a recording medium.

[0024] The image forming apparatus 111 includes a head cartridge 701, a carriage 702, a guide shaft 703, a main scanning motor 704, a motor pulley 705, a driven pulley 706, a timing belt 707, a recording medium 708, and a conveyance roller 709. The image forming apparatus 111 also includes an auto sheet feeder (hereinafter referred to as ASF) 710, a paper feed motor 711, a pickup roller 712, a line feed motor (hereinafter referred to as LF motor) 713, a paper end sensor 714, and a control unit 720.

[0025] The head cartridge 701 has a recording head composed of a plurality of ejection ports and an ink tank that supplies ink to the recording head. A connector is provided for receiving signals for driving each ejection port of the recording head. Five types of inks, namely color inks (cyan, magenta, yellow, and black) and metallic ink, are independently filled in the ink tank.

[0026] The head cartridge 701 is detachably mounted on the carriage 702, and the carriage 702 is provided with a connector holder for transmitting drive signals and the like to the head cartridge 701 via the connector. The carriage 702 is capable of reciprocating movement along the guide shaft 703. Specifically, the carriage 702 is driven via a drive mechanism such as a motor pulley 705, a driven pulley 706, and a timing belt 707 using the main scanning motor 704 as a drive source, and its position and movement are controlled. In the present embodiment, the movement of the carriage 702 along the guide shaft 703 is referred to as "main scanning", and the movement direction is referred to as the "main scanning direction".

[0027] A recording medium 708 such as printing paper is placed on the ASF 710. During image formation, the pickup roller 712 rotates via a gear by driving the paper feed motor 711, and the recording medium 708 is separated one by one from the ASF 710 and fed. Further, the recording medium 708 is conveyed to a recording start position facing the ejection port surface of the head cartridge 701 on the carriage 702 by the rotation of the conveyance roller 709. The conveyance roller 709 is driven via a gear using the LF motor 713 as a drive source. The determination of whether the recording medium 708 has been fed and the determination of the position at the time of feeding are made when the recording medium 708 passes through the paper end sensor 714. The head cartridge 701 mounted on the carriage 702 is held such that the ejection port surface protrudes downward from the carriage 702 and is parallel to the recording medium 708. The control unit 720 is composed of a CPU, storage means, etc., receives data for forming the above-described layers from the outside, and controls the operations of the respective parts of the image forming apparatus 111 based on the data.

[0028] <Operation of Image Forming Apparatus 111> The image forming operation in the image forming apparatus 111 will be described below. In this embodiment, generally used inkjet paper is used as the recording medium 708. First, when the recording medium 708 is conveyed to a predetermined recording start position, the carriage 702 moves on the recording medium 708 along the guide shaft 703, and metallic ink and color ink are ejected from the ejection ports of the recording heads during the movement. Then, when the carriage 702 moves to one end of the guide shaft 703, the conveyance roller 709 conveys the recording medium 708 by a predetermined amount in a direction perpendicular to the main scanning direction of the carriage 702. In this embodiment, the conveyance of the recording medium 708 is referred to as "paper feed" or "sub-scanning", and this conveyance direction is referred to as "paper feed direction" or "sub-scanning direction". When the conveyance of a predetermined amount of the recording medium 708 is completed, the carriage 702 moves again along the guide shaft 703. In this way, an image is formed on the recording medium 708 by repeating the scanning of the carriage 702 of the recording head and the paper feed.

[0029] FIG. 8 is a diagram for explaining the operation of forming an image by scanning the recording head on the recording medium 708. In this embodiment, as shown in FIGS. 8(a) and (b), formation of a layer is performed by the main scanning by the carriage 702 by the width L of the recording head, and every time the recording of one line is completed, the recording medium 708 is conveyed by a distance L in the sub-scanning direction.

[0030] In addition, in order to suppress image quality deterioration such as periodic unevenness due to the driving accuracy of the recording head, so-called multi-pass printing may be performed. Examples of two-pass recording are shown in FIGS. 8(c) to (e). In this example, formation of a layer is performed by the main scanning by the carriage 702 by the width L of the recording head, and every time the recording of one line is completed, the recording medium 708 is conveyed by a distance L / 2 in the sub-scanning direction. Region A is recorded by the m-th main scanning (FIG. 8(c)) and the (m + 1)-th main scanning (FIG. 8(d)) of the recording head, and region B is recorded by the (m + 1)-th main scanning (FIG. 8(d)) and the (m + 2)-th main scanning (FIG. 8(e)) of the recording head.

[0031] Here, the operation of two-pass recording has been described, but the number of passes for recording can be changed according to the desired accuracy. For example, when performing n-pass recording, each time the recording of one line is completed, the recording medium 708 is conveyed by a distance of L / n in the sub-scanning direction. Note that the recording medium 708 is not limited to paper, and various materials can be used as long as they can support the formation of layers by the recording head.

[0032] FIG. 9 is a schematic diagram showing the representation of an image controlled by the area gradation method. For simplicity of explanation, the recording head in the present embodiment is assumed to be controlled in a binary manner as to whether or not to eject ink droplets. Further, in the present embodiment, the on / off of the ink is controlled for each pixel defined by the output resolution of the image forming apparatus 111, and the state where all the pixels in the unit area are turned on is treated as 100% of the ink recording amount. Note that "on" represents ejecting ink, and "off" represents not ejecting ink. In such a binary printer, in a single pixel, the ink recording amount can only be represented as 100% or 0%, so the intermediate gradation is represented by a set of a plurality of pixels.

[0033] In the example shown in FIG. 9, instead of performing intermediate gradation representation at a density of 25% as shown in the lower left of the figure, ink is ejected onto 4 pixels out of 16 pixels (4×4 pixels) as shown in the lower right, thereby performing an area representation of 25% (4 / 16). The same can be applied to other gradations. Note that the total number of pixels for representing the intermediate gradation, the pattern of pixels to be turned on, etc. are not limited to the above example. The pattern of pixels to be turned on can be determined using periodic screen processing called halftone dots or error diffusion processing. Note that the above-described binarization process can be extended to a multi-valued process with a plurality of modifiable levels, and is also applicable to a recording head in which the ink ejection amount is modifiable, and is not limited to binarization.

[0034] <Flowchart executed by image processing apparatus 1> As described above, as a main factor for perceiving a three-dimensional effect in a printed matter, it is possible to reproduce a change in brightness that occurs due to a change in geometric conditions such as the position of a light source or the posture of a camera. Below, a method for determining an appropriate usage amount of metallic ink used to reproduce a change in geometric conditions will be described.

[0035] FIG. 10 is a flowchart showing the flow of data from the image processing apparatus 1 until it outputs data for forming an image on a recording medium to the image forming apparatus 111 in the present embodiment. Note that the processing in each step of FIG. 10 is performed by the CPU 101 of the image processing apparatus 1 expanding and executing the program code stored in the ROM 102 in the RAM 103. Also, the symbol "S" in the description of each process means that it is a step in the flowchart.

[0036] First, in S1001, the first image acquisition unit 601 acquires, from an external device such as the HDD 113, an image to be formed on the recording medium, that is, first image data that is the object to be printed. Let the pixel value at the pixel position (x, y) be RGB 1 (x, y). The first image data is an image having color information of 16 bits for each of the R (red), G (green), and B (blue) values, a total of 48 bits per pixel. The pixel value of the first image data in the present embodiment is an RGB value defined in the sRGB space. Other generally used RGB images defined in AdobeRGB, Lab images corresponding to CIELAB, or HSV images composed of hue, saturation, and lightness can also be used. Note that the pixel position (x, y) indicates the pixel position in the image when the horizontal coordinate of the pixel is x and the vertical coordinate of the pixel is y.

[0037] In S1002, the second image acquisition unit 602 acquires second image data RGB representing an image to be formed on the recording medium from an external device such as the HDD 113 2Obtain (x, y). The second image data is RGB values defined in the sRGB space with 16 bits per color, similar to the first image data. The first image data and the second image data are images representing scenes of different geometric conditions of the same subject as described above. That is, one is an image under the condition of reflecting light in the specular reflection direction, and the other is an image under the condition of reflecting light in the diffused direction.

[0038] In S1003, the color conversion unit 603 converts the first image data acquired by the first image acquisition unit 601 and the second image data acquired by the second image acquisition unit 602 into tristimulus values XYZ, respectively. The color conversion unit 603 converts the pixel value RGB which is an RGB value 1 (x, y) and RGB 2 Convert (x, y) into tristimulus values (XYZ values) defined in the CIE1913 XYZ color space. Specifically, based on the following formulas (1) and (2), the pixel value XYZ after conversion 1 (x, y) and XYZ 2 Calculate (x, y). R L = degamma(R) G L = degamma(G) ··· Formula (1) B L = degamma(B)

[0039]

Number

[0040] Here, R, G, and B are the R value, G value, and B value that respectively constitute RGB 1 (x, y) and RGB 2 (x, y). The RGB values defined in the sRGB space have gamma characteristics corresponding to the characteristics of a standard display. Degamma is a function that converts this RGB value into linear RGB values R L , G L , and B L as described later. X, Y, and Z are the XYZ 1 (x, y) and XYZ2 (x, y) consists of an X value, a Y value, and a Z value. M is a conversion matrix that converts linear RGB values defined in the sRGB space into XYZ values defined in the CIE1913 XYZ color space.

[0041] In S1004, the declination reflection characteristic determination unit 604 determines the declination reflection characteristic using the Y value, which is the value representing brightness, among the XYZ values of the first image data and the second image data respectively. In the present embodiment, the difference in brightness when changing from the first image data to the second image data is calculated. Therefore, as shown in the following formula (3), the declination reflection characteristic ΔY can be calculated by obtaining the difference between the Y value of the first image data and the Y value of the second image data. ΔY = Y 1 − Y 2 ··· Formula (3)

[0042] In S1005, the metallic ink amount determination unit 605 calculates the metallic ink amount Me(x, y) using formula (4) based on Y 1 (x, y), Y 2 (x, y), and the declination reflection characteristic ΔY obtained by formula (3).

[0043]

Equation

[0044] Here, ΔY max is the maximum value of ΔY(x, y), ΔY minis the minimum value of ΔY(x, y). Further, Equation (4) is a general normalization process, and the maximum value of Me is 1 and the minimum value is 0. The maximum value of 1 corresponds to an area ratio of 100% in the area gradation shown in FIG. 9, and the minimum value of 0 corresponds to an area ratio of 0%. That is, when changing from the first image data to the second image data, it is a process of increasing the amount of metallic ink used according to the brightness for each coordinate. That is, a process of applying a large amount of metallic ink to bright coordinates and not applying metallic ink to dark coordinates. In the present embodiment, the relationship between ΔY and the amount of metallic ink Me is linear, but it is also possible to adjust the gradation characteristics or adjust the maximum and minimum values of the amount of metallic ink Me by using an appropriate function or look-up table (LUT) process.

[0045] In S1006, the color ink amount determination unit 606 determines the CMYK color ink amount based on the XYZ values of the first image data determined by the color conversion unit 603, which is XYZ 1 and the amount of metallic ink Me determined by the metallic ink amount determination unit 605. Here, the first image is set as the target value in an observation environment with little influence of regular reflection light, and the amount of color ink is determined in consideration of the influence of the diffusion color of the metallic ink determined previously. First, the XYZ value of the color ink, which is XYZ color is calculated by the following Equation (5). XYZ color = XYZ 1 / XYZ Me ··· Equation (5)

[0046] Here, XYZ Me is the XYZ value representing the diffusion color of the metallic ink. XYZ Me can be determined, for example, by previously holding the relationship between the amount of metallic ink Me and the colorimetric value as a LUT by a 0° / 45° colorimeter excluding the influence of regular reflection light. Also, when a color development model holds in which the XYZ value of the printed matter can be obtained by multiplying the XYZ value of the metallic ink and the XYZ value of the color ink, the target value XYZ 1 is XYZ MeBy dividing, the necessary XYZ values in the color ink can be obtained. Note that this step is performed to adjust the amount of color ink because the brightness of the diffused light decreases depending on the amount of metallic ink added. XYZ color To determine the CMYK color ink amount from color , general methods such as using a pre-prepared LUT can be used. Note that the determined XYZ color If it cannot be reproduced, it may be clipped to be within the reproducible range. Also, a method of adjusting the amount of metallic ink to be within the reproducible range can be considered.

[0047] In S1007, the output unit 607 outputs the metallic ink amount Me determined by the metallic ink amount determination unit 605 and the CMYK color ink amount determined by the color ink amount determination unit 606 to the external image forming apparatus 111, and ends the process.

[0048] As described above, according to the present embodiment, a three-dimensional effect can be suitably imparted to an object or a subject to be reproduced as an image. Specifically, based on the above-described flow, by printing a printed matter using metallic ink, it becomes possible to reproduce the change in the brightness of the light reflected by the subject due to the difference in the position of the light source. Thereby, in an observation environment where the main light source is not reflected, the first image data is reproduced in the same manner as a conventional printed matter, and in an observation environment where the main light source is intentionally reflected, a printed matter with the amount of change in brightness controlled for each location of the image can be formed. Therefore, it becomes possible to simulate the change in brightness due to the geometric conditions of a three-dimensional object in a two-dimensional image, and a suitable three-dimensional effect can be imparted to an object or a subject to be reproduced as an image.

[0049] Note that from equation (2), XYZ 1 and XYZ 2 At the stage of calculating, the pre-prepared X 1 , Y 1 , Z 1 , Y 2Also, the amounts of inks CMYK and Me may be determined by referring to a LUT in which the correspondence with the respective ink amounts C, M, Y, K, and Me is described.

[0050] <<Embodiment 2>> In Embodiment 1, an example was described in which two pieces of image data were input and the amount of metallic ink to be applied was determined from the difference in their brightness. In this embodiment, an example of determining the ink amount by virtually generating second image data with different geometric conditions from the first image data will be described.

[0051] Regarding the parts common to Embodiment 1, the description will be omitted or simplified, and the following will focus on the differences.

[0052] <Logical Configuration of Image Processing Apparatus 1> FIG. 11 is a diagram showing the logical configuration of the image processing apparatus 1 in this embodiment. The image processing apparatus 1 includes a first image acquisition unit 1101, a normal vector information acquisition unit 1102, a light source setting unit 1103, a reflectance determination unit 1104, a second image determination unit 1105, a color conversion unit 1106, an ink amount determination unit 1107, and an output unit 1108.

[0053] The first image acquisition unit 1101 acquires first image data representing a scene under certain geometric conditions of the subject. The normal information acquisition unit 1102 acquires normal information of the subject with respect to the first image data. The normal information is information indicating the direction in which the minute surface of the three-dimensional subject reproduced at each coordinate on the first image faces. The light source setting unit 1103 sets light source information of the scene represented by the first image data and second image data described later. The light source information is information indicating the direction in which the light source is located with respect to the subject. The reflectance determination unit 1104 determines the reflectance of the subject from the first image data, the normal information, and the light source information. The second image determination unit 1105 generates second image data from the normal information, the light source information, and the reflectance of the subject. The color conversion unit 1106 converts the color information of the first image data and the second image data into tristimulus values XYZ. The ink amount determination unit 1107 determines ink amount data for each color from the tristimulus values of the first image data and the second image data. The output unit 1108 outputs the determined ink amount data to the image forming apparatus 111.

[0054] <Flowchart executed by the image processing apparatus 1> FIG. 12 is a flowchart showing the flow until the image processing apparatus 1 outputs data for forming an image on a recording medium to the image forming apparatus 111 in the present embodiment. Note that the processing in each step of FIG. 12 is performed by the CPU 101 of the image processing apparatus 1 expanding and executing program codes stored in the ROM 102 in the RAM 103. In addition, the symbol "S" in the description of each process means that it is a step in the flowchart.

[0055] First, in S1201, the first image acquisition unit 1101 acquires first image data RGB 1 (x, y). Since the first image acquisition unit 1101 is the same as the first image acquisition unit 601 in the first embodiment, a detailed description thereof is omitted.

[0056] In S1202, the normal information acquisition unit 1102 acquires a normal vector corresponding to the first image data from an external device such as the HDD 113

[0057]

Number

[0058] Obtain. Hereinafter, the arrow of the vector is omitted and denoted as n(x, y) (except for the notation of the formula).

[0059] Here, the normal line n is a three-dimensional vector representing the direction in which the micro surface of the three-dimensional subject reproduced at each coordinate x, y on the first image faces. Therefore, the normal line information can be obtained simultaneously with the shooting of the first image using, for example, a stereo camera or the like. Alternatively, it is also possible to obtain the normal line information in combination with the rendered image from the 3DCG model.

[0060] In S1203, the light source setting unit 1103 sets the light source vector

[0061]

Number

[0062] Set. Hereinafter, the arrow of the vector is omitted and denoted as L 1 (except for the notation of the formula). The light source vector L 1 is a three-dimensional vector representing the direction from which the light source hits the subject. For example, similar to the normal line information, by using a fish-eye lens or the like at the time of shooting to obtain the luminance distribution in all directions of the scene, it is possible to obtain the direction of the main light source. Alternatively, as also mentioned in S1202, it is also possible to obtain information from the 3DCG model. Also, a method in which the user gives an arbitrary value is conceivable. In the present embodiment, as long as the change in brightness under different geometric conditions can be reproduced and the three-dimensional feeling can be perceived, it does not necessarily have to be accurate information. For example, the light source direction may be set in advance, such as being in the same position as the camera, that is, in the vertical direction with respect to the captured two-dimensional image.

[0063] In S1204, the reflectance determination unit 1104 calculates the reflectance Ref(x, y) of the subject in the first image using the following formula (6).

[0064]

Equation

[0065] Here, I 1 represents the brightness of the first image, and RGB1 is the linear RGB values R L , G L , and B L constituted from. The reflectance Ref is the reflectance R 1 for each of the three channels of the linear RGB values R L , G L , and B L of the image brightness I RL , R GL , and R BL constituted by. L 1 ·n represents the inner product of the light source vector L 1 and the normal vector n. This means calculating the reflectance inversely using a model in which the brightness of the first image is determined by the reflected light in the so-called diffusion direction of "the angle formed by the light source and the normal" and "the reflectance of the subject".

[0066] In S1205, the light source setting unit 1103 arbitrarily sets the light source vector L 2 of the second image data. Since the light source vector L 1 mentioned above does not necessarily have to be accurate information, it is also possible to preset a vector obtained by shifting a predetermined angle from the light source vector L 1 .

[0067] In S1206, the second image determination unit 1105 calculates the second image data I 2 using the following formula (7).

[0068]

Equation

[0069] Here, I 2 represents the brightness of the second image and is composed of the linear RGB values R L , G L , and B L .

[0070] In S1207, the ink amount determination unit 1107 determines the color ink amounts CMYK and the metallic ink amount Me. Specifically, first, the color conversion unit 1106 converts the brightness I 1 of the first image and the brightness I 2 of the second image into XYZ 1 , XYZ 2 respectively based on Equation (2). In this embodiment, by referring to the LUT in which the correspondence between the prepared X 1 , Y 1 , Z 1 , Y 2 and each ink amount C, M, Y, K, Me is described, each ink amount CMYK and Me are determined. Note that each ink amount may be determined by the same method as in Embodiment 1 using XYZ 1 , XYZ 2 .

[0071] In S1208, the output unit 1108 outputs each ink amount CMYK and Me to the external image forming apparatus 111.

[0072] As described above, according to this embodiment, by virtually generating second image data with different geometric conditions from the first image data, a suitable three-dimensional effect can be imparted without inputting two image data.

[0073] <<Other Embodiments>> In the above-described embodiment, metallic ink is used as the ink having a bias in the angular reflection characteristic. In addition, the same effect can be obtained by using so-called gloss control ink such as clear ink that improves the smoothness of the printed surface and strengthens the regular reflected light, or high refractive index ink that uses a material with a high refractive index to obtain strong regular reflected light.

[0074] Further, in Embodiment 1, in the step of determining the color ink amount, when determining the XYZ values by the color ink, the color development model by multiplying the XYZ values was used for explanation. In addition, it is possible to use other color development models or color development simulations suitable for the image forming apparatus to be used.

[0075] Further, in Embodiment 2, as a model for determining the reflected light, a simple model of a light source vector, a normal vector, and a reflectance was used for explanation. As another method, it is also possible to use other models such as specular reflection light or ambient light called ambient used in computer graphics.

[0076] Further, in the step of determining the ink amount in Embodiment 2, the inputs to the LUT are X 1 Y 1 Z 1 and Y 2 However, instead of Y 2 it is possible to use ΔY, or normΔY obtained by normalizing ΔY. Further, instead of considering the change in the brightness information, the hue of the second image is also considered, and X 1 Y 1 Z 1 X 2 Y 2 and Z 2 It is also possible to use a method using a LUT that takes the above values as inputs. Further, it is possible to use Lab values, HSV values, RGB values, etc. obtained by color-converting the above values.

[0077] The present invention can also be realized by supplying a program capable of operating one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Explanation of Signs

[0078] 1 Image processing apparatus 111 Image forming apparatus 601 First image acquisition unit 602 Second image acquisition unit 604 Deflection angle reflection characteristic determination unit 605 Metallic ink amount determination unit 606 Color ink amount determination unit

Claims

1. An image processing apparatus for generating data for forming an image on a recording medium, comprising: a first acquisition means for acquiring first image data to be printed; a second acquisition means for acquiring second image data representing the same subject as the subject of the first image data and represented under geometric conditions different from those of the first image data; a first determination means for determining a specular reflection characteristic indicating the intensity of brightness at each position of the image based on the difference in brightness between the first image data and the second image data; a second determination means for determining the ink amount of each ink including the first ink and the second ink using the specular reflection characteristic determined by the first determination means; the image is formed using the first ink, in which the intensity of light reflected in the diffuse reflection direction is different from the intensity of light reflected in the specular reflection direction when light is incident at a predetermined angle on the first ink applied on the recording medium, and the second ink, which is different from the first ink and has a smaller ratio of the intensity of light reflected in the specular reflection direction to the intensity of light reflected in the diffuse reflection direction when light is incident at a predetermined angle on the second ink applied on the recording medium than the first ink. An image processing apparatus characterized by this.

2. The image processing apparatus according to claim 1, wherein the specular reflection characteristic includes brightness information of at least two image data represented under different geometric conditions.

3. The image processing apparatus according to claim 2, wherein the first determination means determines brightness information in the specular reflection direction from one of the first image data and the second image data, and determines brightness information in the diffuse reflection direction from the other.

4. The image processing apparatus according to any one of claims 1 to 3, wherein the second determination means determines the ink amount of the first ink based on the specular reflection characteristic, and determines the ink amount of the second ink based on the first image data or the second image data and the determined ink amount of the first ink.

5. The image processing apparatus according to claim 1, wherein the second acquisition means acquires second image data in which the light source is set at an arbitrary position different from the light source position of the first image data, using the brightness information included in the first image data and the reflectance that can be represented by the light source information and the normal information corresponding to the first image data.

6. The image processing apparatus according to claim 1 or 5, wherein the second determination means determines the ink amount of each ink by using a look-up table having a function that takes as input the first image data and information on the brightness of the second image data and outputs the respective ink amounts.

7. The image processing apparatus according to any one of claims 1 to 6, wherein the first ink includes at least one of a metallic ink, a gloss control ink, and a high refractive index ink.

8. The image processing apparatus according to any one of claims 1 to 7, wherein the second ink is a color ink including cyan ink, magenta ink, yellow ink, and black ink.

9. A control method for an image processing apparatus that generates data for forming an image on a recording medium, comprising: a first acquisition step of acquiring first image data to be printed; a second acquisition step of acquiring second image data that shows the same subject as the subject of the first image data and is represented by geometric conditions different from those of the first image data; a first determination step of determining a specular reflection characteristic indicating the intensity of brightness at each position of the image based on the difference in brightness between the first image data and the second image data; a second determination step of determining the ink amount of each ink including a first ink and a second ink by using the specular reflection characteristic determined in the first determination step; and The image is formed using the first ink, in which the intensity of light reflected in the diffuse reflection direction is different from the intensity of light reflected in the specular reflection direction when light is incident at a predetermined angle on the first ink applied on the recording medium, and the second ink, which is different from the first ink and has a smaller ratio of the intensity of light reflected in the specular reflection direction to the intensity of light reflected in the diffuse reflection direction when light is incident at a predetermined angle on the second ink applied on the recording medium than the first ink. An image processing method characterized by that.

10. A program for causing a computer to function as each means in the image processing apparatus according to any one of claims 1 to 8.

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