JP2013145982A - Imaging apparatus, image processing apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display an image of in-focus state suitable for a photographic scene without the hassle of a user, when displaying image data captured by a light field camera.SOLUTION: The imaging apparatus includes a photographic lens (101), an image sensor (103) consisting of multiple pixels arranged two-dimensionally and outputting image data by performing photoelectric conversion of the incident light, multiple microlenses (102) arranged between the photographic lens and the image sensor and corresponding, respectively, to the multiple regions of the image sensor consisting of a predetermined number of pixels, a refocus image processing circuit (106) performing refocus processing for creating an image focused to an arbitrary distance, from the image data of multiple pixels output from the image sensor, an operation circuit (110) for selecting a scene corresponding to parameters used for the refocus processing, and display means (111) for displaying the image created by the refocus image creation means by using parameters corresponding to the scene selected by the selection means.

Description

  The present invention relates to display of an image taken by an imaging apparatus, and more particularly to an image display technique capable of changing the focus distance of an image after shooting.

  2. Description of the Related Art In recent years, an imaging apparatus (light field camera) that can acquire not only the intensity distribution of light but also information on the incident direction of light (light rays) has been proposed in an imaging apparatus such as an electronic camera. A light field can be said to be a “field” of rays that fly through an unoccluded space. In order to identify one light ray in the light field, for example, two parallel planes are appropriately set as shown in FIG. 13, and the intersection (x ′, y ′), ( u, v) may be specified. The light field camera is a camera that captures and records the light ray information field with an image sensor.

  For example, according to Non-Patent Document 1, as shown in FIG. 14, a microlens array 1402 is arranged between a photographing lens 1404 and an image sensor 1401, and one microlens 1403 is provided for a plurality of pixels of the image sensor 1401. To correspond. In this way, light that has passed through the microlens 1403 is acquired by a plurality of pixels for each incident direction. Therefore, the output value L of each pixel of the image sensor 1401 has information as light rays, and the output value L (x ′, y ′, u, v) is recorded as light field information. On the other hand, in the case of a normal imaging device, an imaging device is arranged at the position of the microlens array, and L (x ′, y ′, u, v) is integrated with respect to the lens surface (u, v). Is recorded as the output value E (x ′, y ′) of each pixel, and information on the incident direction is lost.

  The light field information acquired as described above is integrated by u and v optically performed in the conventional imaging apparatus, and is integrated by arithmetic processing in the light field camera. With this method, in addition to generating normal captured images, a technique called “Light Field Photography” can be applied to re-create a 2D image focused on an arbitrary virtual image plane (refocus plane) after shooting. Can be configured.

Ren.Ng and 7 others, “Light Field Photography with a Hand-Held Plenoptic Camera”, Stanford Tech Report CTSR 2005-02

  However, in the conventional light field camera, the in-focus state can be freely set after shooting. However, in order to obtain an image in a desired in-focus state during shooting or after checking the image, the user needs to The user has to specify the focus position.

  The present invention has been made in view of the above problems, and when displaying image data captured by a light field camera, an image in a focused state suitable for a shooting scene is displayed without the user's effort. The purpose is to be able to.

  In order to achieve the above object, an imaging apparatus according to the present invention includes a photographic lens, an imaging device including a plurality of two-dimensionally arranged pixels that photoelectrically convert incident light to output image data, and the photographic lens. And a plurality of microlenses arranged between the image sensor and corresponding to each of a plurality of regions of the image sensor composed of a predetermined number of pixels, and the plurality of pixels output from the image sensor Refocus image generation means for performing refocus processing for generating an image focused at an arbitrary distance from image data, selection means for selecting a scene corresponding to a parameter used for the refocus processing, and the selection means Display means for displaying the image generated by the refocus image generation means using the parameter corresponding to the scene selected by.

  ADVANTAGE OF THE INVENTION According to this invention, when displaying the image data image | photographed with the light field camera, it can display the image of the focusing state suitable for an imaging | photography scene, without a user's effort.

1 is a block diagram showing a schematic configuration of an imaging apparatus according to an embodiment of the present invention. FIG. 6 is a diagram for explaining a positional relationship between pixels of the image sensor according to the embodiment and a microlens array. 4A and 4B are diagrams for explaining a positional relationship among a photographic lens, an image sensor pixel, and a microlens array according to the embodiment. FIG. 6 is a diagram for explaining a correspondence relationship between a pupil region and a light receiving pixel of the photographing lens according to the embodiment. The figure explaining the passage area of the refocus image generation light ray concerning an embodiment. 6 is a flowchart illustrating processing during a shooting operation according to the first embodiment. 5 is a flowchart of refocus image generation processing according to the first embodiment. The figure which shows the virtual concept of the optical system at the time of the pan focus image production | generation in 1st Embodiment. The figure which shows the correspondence of the pupil region of the imaging lens at the time of the pan focus image generation in 1st Embodiment, and a light reception pixel. The figure which shows the virtual concept of the optical system at the time of the refocus process focused on the face in 1st Embodiment. The figure which shows the correspondence of the pupil region of the imaging lens at the time of the refocus process focused on the face in 1st Embodiment, and a light reception pixel. 10 is a flowchart showing processing at the time of image reproduction in the second embodiment. Explanatory drawing of the coordinate system which identifies a light ray. The figure which shows the optical system of a light field camera.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. The embodiment described below is an example for realizing the present invention, and should be appropriately modified or changed according to the configuration and various conditions of the apparatus to which the present invention is applied. It is not limited to the embodiment.

<First Embodiment>
FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus 100 according to an embodiment of the present invention. In the configuration shown in FIG. 1, light that has passed through the photographic lens 101 forms an image near the focal position of the photographic lens 101. The microlens array 102 includes a plurality of microlenses 1020, and is arranged in the vicinity of the focal position of the photographing lens 101 so that light that has passed through different pupil regions of the photographing lens 101 is divided and emitted for each pupil region. It has the function to do. The imaging element 103 is a photoelectric conversion element typified by a CMOS image sensor or a CCD image sensor, and photoelectrically converts incident light and outputs an image signal. By arranging two-dimensionally so that a plurality of pixels correspond to each of the plurality of microlenses 1020, the light emitted after being divided for each pupil region by the microlens 1020 is received while maintaining the division information. The image signal can be converted into a data processable image signal.

  An analog signal processing circuit (AFE) 104 performs correlated double sampling processing, signal amplification, reference level adjustment, A / D conversion processing, and the like on the image signal output from the image sensor 103. A digital signal processing circuit (DFE) 105 performs digital image processing such as reference level adjustment on the image signal output from the analog signal processing circuit 104.

  The image processing circuit 106 performs predetermined image processing on the image signal output from the digital signal processing circuit 105 and refocusing calculation (development processing) for focusing on an arbitrary focusing distance unique to the light field camera. Further, the image processing circuit 106 performs processing such as detecting a human face from the image. The memory circuit 107 is a volatile memory that temporarily holds image data, and is excellent in high-speed and random accessibility. The recording circuit 108 is a control circuit for recording on a recording medium such as a nonvolatile memory or a memory card for recording and holding the image data output from the image processing circuit 106.

  The control circuit 109 performs overall drive control of the entire imaging apparatus 100 such as the imaging element 103 and the image processing circuit 106. The operation circuit 110 is a circuit that receives a signal from an operation member provided in the imaging apparatus 100 and reflects various setting contents such as a user instruction and a scene selection described later to the control circuit 109. The display circuit 111 displays an image after shooting, a live view image, various setting screens, and the like.

  Next, the positional relationship among the taking lens 101, the microlens array 102, and the image sensor 103 in the image pickup apparatus of the present embodiment will be described.

  FIG. 2 is a view of the image sensor 103 and the microlens array 102 as seen from the direction of the optical axis Z in FIG. One microlens 1020 is arranged to correspond to the plurality of divided pixels 201. A plurality of divided pixels 201 behind one microlens are collectively defined as a pixel array 200. In the first embodiment, the pixel array 200 is configured by a total of 25 divided pixels 201 of 5 rows and 5 columns.

  FIG. 3 is a diagram of a state in which light emitted from the photographing lens 101 passes through one microlens 1020 and is received by the image sensor 103 as viewed from a direction perpendicular to the optical axis Z. Light emitted from each of the pupil regions a1 to a5 of the photographing lens 101 and passed through the central microlens 1020 forms an image on the corresponding divided pixels p1 to p5, respectively.

  FIG. 4A shows the aperture of the photographic lens 101 viewed from the optical axis Z direction in order to explain the state of the light passing area of the photographic lens 101 and the light receiving area of the image sensor 103 shown in FIG. It is a figure. FIG. 4B is a view of one microlens 1020 and the pixel array 200 disposed behind the microlens 1020 when viewed from the optical axis Z direction. As shown in FIG. 4A, when the pupil region of the photographing lens 101 is divided into the same number of regions as the pixels behind one microlens 1020, one pixel is divided into one pupil division region of the photographing lens 101. The emitted light is imaged. However, here, it is assumed that the F-numbers of the photographing lens 101 and the microlens 1020 are substantially the same.

  The correspondence between the pupil regions a11 to a55 of the photographing lens 101 shown in FIG. 4A and the pixels p11 to p55 shown in FIG. 4B is point-symmetric when viewed from the optical axis Z direction. Therefore, the light emitted from the pupil region a11 of the photographing lens 101 forms an image on the pixel p11 in the pixel array 200 behind the microlens 1020. Similarly, light emitted from the pupil region a11 and passing through another microlens 1020 forms an image on the pixel p11 in the pixel array 200 behind the microlens 1020.

In the case of the relationship between the image sensor 103 and the microlens 1020 as shown in FIG. 2, the number of pupil divisions is the number of pixels (5 × 5 = 25) that fall within one microlens. Here, the pupil division position (u, v) is set to u = 0, 1, 2, 3, 4, v = 0, 1, 2, 3, 4, and the microlens position coordinates (x ′, y ′) are set. X ′ = 0, 1, 2, 3, 4 and y ′ = 0, 1, 2, 3, 4. In this case, the pixel coordinates (p, q), p = 0 to 24, and q = 0 to 24 of the image sensor 103 are pupil division position coordinates (u, v) and microlens position coordinates (x ′, y ′). Can express
p (x ′, u), q (y ′, v) (1)

It can be expressed as.
Here, a method for calculating a focal position (refocus plane) corresponding to an arbitrary subject position in the screen will be described. As described with reference to FIG. 4, each pixel of the pixel array 200 receives light that has passed through different pupil regions with respect to the photographing lens 101. By combining a plurality of pixel signals from these divided signals, a pair of signals divided into pupils in the horizontal direction is generated.

  Expression (2) is obtained by integrating the light passing through the left area (pupil areas a11 to a51 and a12 to a52) of the exit pupil of the photographing lens 101 for each pixel of a certain pixel array 200. This is applied to a plurality of pixel arrays 200 arranged in the horizontal direction, and a subject image constituted by these output signal groups is defined as an A image. Expression (3) is obtained by integrating the light passing through the right area (pupil areas a14 to a54 and a15 to a55) of the exit pupil of the photographing lens 101 for each pixel of a certain pixel array 200. This is applied to a plurality of pixel arrays 200 arranged in the horizontal direction, and a subject image constituted by these output signal groups is defined as a B image. A correlation operation is performed on the A image and the B image, and an image shift amount (pupil division phase difference) is detected. Furthermore, the focal position corresponding to an arbitrary subject position in the screen can be calculated by multiplying the image shift amount by the focal position of the photographing lens 101 and a conversion coefficient determined by the optical system.

  Next, image reconstruction at an arbitrarily set focal position (refocus plane) is performed on imaging data (light field information) acquired by the configuration of the photographing lens 101, the microlens array 102, and the imaging element 103. Processing will be described.

  FIG. 5 shows a direction perpendicular to the optical axis Z indicating from which pupil division region of the photographing lens 101 light that passes through a pixel on an arbitrarily set refocus plane is emitted and which microlens 1020 is incident. It is the figure seen from. Here, the position of the pupil division region of the photographing lens 101 is coordinates (u, v), the pixel position on the refocus plane is coordinates (x, y), and the position of the microlens 1020 on the microlens array 102 is coordinates (x ', Y'). Further, the distance from the photographing lens 101 to the microlens array 102 is F, and the distance from the photographing lens 101 to the refocus plane is αF. α is a refocus coefficient for determining the position of the refocus plane and can be arbitrarily set by the user. In FIG. 5, only the directions of u, x, and x ′ are shown, and v, y, and y ′ are omitted. As shown in FIG. 5, the light passing through the coordinates (u, v) and the coordinates (x, y) reaches the coordinates (x ′, y ′) on the microlens array 102. The coordinates (x ′, y ′) can be expressed as in Equation (4).

When the output of the pixel receiving this light is L (x ′, y ′, u, v), the output E (x, y) obtained with the coordinates (x, y) on the refocus plane is L Since (x ′, y ′, u, v) is integrated with respect to the pupil region of the photographic lens 101, Equation (5) is obtained.

  In equation (4), if the refocus coefficient α is determined, the coordinates (x, y) on the refocus plane and the pupil division region position coordinates (u, v) are given, so that the position of the microlens where the light enters. (X ′, y ′) is obtained. Then, the pixels p and q on the image sensor corresponding to the position (u, v) from the pixel array 200 corresponding to the microlens are obtained from the equation (1), and the pixel output of this image sensor is L (x ′, y ′, u, v) = L (p, q). E (x, y) can be calculated by performing this operation for all pupil division regions and integrating the obtained pixel outputs. If (u, v) is the representative coordinates of the pupil division area of the taking lens, the integral of equation (5) can be calculated by simple addition.

  Next, the operation at the time of shooting of the image pickup apparatus of the present invention will be described with reference to the flowchart of FIG. Each step is performed in each unit according to an instruction from the control circuit 109 or the control circuit 109. When shooting is started (S601), in S602, the scene selection content set by the user in the imaging apparatus is acquired. The scene select is for comprehensively setting various shooting parameters so that the user can easily capture a desired image. For example, image processing contents such as AE (Auto Exposure) setting, image tint, resolution, and the like are set to contents suitable for a scene, and a focus state is set. Then, the user sets the scene selection through the operation circuit 110. In the imaging apparatus of the first embodiment, portrait (person) photography, landscape photography, macro photography, night scene photography, and the like can be selected. The scene select setting may be automatically set by a known scene discrimination technique or the like.

  In S603, AE is set according to the scene select setting. For example, when night scene shooting is selected as a scene, settings such as a slow shutter speed are performed. In step S604, a refocus process to be applied is selected according to the set scene select. In step S <b> 605, a live image is generated by executing the selected refocus processing on the light field information output obtained from the image sensor 103 by the image processing circuit 106, and displayed on the display circuit 111. Details of selection and processing contents of the refocus processing will be described later.

  During shooting, the image to be displayed is continuously updated at a predetermined time interval (loop from S605 to S606). When the user changes the scene selection, the refocus processing is changed (S607), and the display image is sequentially updated. When the user presses the shutter, the recording circuit 108 records the light field information at that time on the recording medium in S608. After recording, a confirmation image is generated with the content of the refocus process currently selected and displayed on the display circuit 111 (S609). If the user changes the scene selection setting within a predetermined time (S610), the refocus processing content is changed (S611), and a confirmation image is generated and displayed again based on the content. If the scene select setting is not changed after a predetermined time, it is determined that the setting has the desired contents, and the scene select information is used as additional information of the already recorded light field information. Recording is performed in association with the field information (S612). The above is the flow of processing during imaging and recording of the imaging apparatus according to the first embodiment.

  Here, refocus image generation processing (S605, S608) according to scene selection will be described with reference to the flowchart of FIG.

  In the imaging apparatus according to the first embodiment, when landscape shooting or night scene shooting is selected as the scene select, “pan focus” is selected as the refocus processing. When the refocus image generation process is started in this state, the process branches from S702 to S703, and a pan focus image is generated.

  A method of generating a pan focus image will be described with reference to FIGS. In FIG. 9, the divided pixels used for generating the pan-focus image are shown in white, and the divided pixels not used are shaded. When the F number of the photographic lens 101 is small, only the divided pixels on which light near the center of the optical axis is incident are used among the divided pixels. In FIG. 9B, an image having a resolution equivalent to that of the microlens array 102 is generated by constructing an image as an output that represents only the microlens 1020 among the divided pixels of the pixels p11 to p55. The In this case, as shown by the virtual aperture 112 in FIG. 8, a virtual small aperture state is reproduced, which generates an image having a deep depth of field (pan focus image). Become. For example, in the case of FIG. 2, the image is composed of 5 × 5 pixels, but in actuality, it is composed of a very large number of microlenses.

  Further, in the image pickup apparatus of the present invention, when the person photographing is selected as the scene select, “focus on the face” is selected as the refocus processing. In this state, when the refocus image generation processing is started, the process branches from S702 to S704. First, in order to detect the face from the shooting target, first, a pan focus image having a deep depth of field is generated by the method described above. (S704). Face detection processing is performed on the generated pan focus image, and the position of the face is specified (S705). When the position of the face is obtained, the subject focus position for focusing on the face is calculated (S706), and the refocus coefficient α is determined (S707). When a plurality of faces are detected, the refocus coefficient α is obtained for each face, and the face with the largest α (the face in front) is set as the face to be focused. When the refocus coefficient α is determined, a refocus image is generated by arithmetic processing according to the above equation (5) (S708). The above process is schematically shown in FIG. This figure shows an example in which a human face is detected almost at the center of the image and an image refocused to the face position is generated. Here, only one dimension in the direction perpendicular to the optical axis Z is considered, and the position of the virtual image plane 113 to be refocused is located at a certain position on the photographing lens side from the microlens array 102.

  The light beam formed on the virtual pixel 114 on the virtual image surface 113 enters the microlens array 102 in a state of diverging from this point. Furthermore, as shown in FIG. 10, the light passes through different microlenses 1020 depending on the angle of the light beam, and enters the divided pixels p1 to p5 with a certain shift amount. Therefore, the pixel output of the virtual pixel 114 on the virtual image plane 113 is obtained by adding and averaging the outputs of the divided pixels p1 to p5 (more precisely, weighting according to the incident angle and the shift amount). More specifically, as shown in FIG. 11, out of 5 rows and 5 columns of divided pixels corresponding to each microlens 1020, 1 row and 5 columns are set as one set, and each microlens 1020 is shifted by one row. A total of 5 rows and 5 columns of divided pixels may be configured.

  In the above example, for ease of explanation, an example in which the shift amount is one row of divided pixels has been described, but this shift amount depends on the position of the virtual image plane 113. Therefore, a weighting matrix is calculated depending on the position of the virtual image plane 113, and a matrix operation (weighted addition) is performed on the output of the divided pixels to obtain a refocused image on an arbitrary virtual image plane 113. be able to. However, in practice, a two-dimensional operation is required. Further, in order to reduce the calculation amount and the calculation time, a weighting matrix in a specific virtual image plane 113 is held in advance, and matrix calculation is performed on the output of the divided pixels. Thereby, a refocus image (here, an image refocused on a human face) on a specific virtual image plane 113 can be obtained.

  In the imaging apparatus of the first embodiment, when a scene other than the above is selected as a scene selection, such as macro shooting, “focus on the foremost subject” is selected as the optimum focus process as the refocus process. The When the refocus image generation process is started in this state, the process branches from S702 to S709. Since it is unknown at which position in the image the foremost subject exists, a plurality of focus positions and refocus coefficients α are calculated at some representative points (step S709). For example, the image is divided into 5 × 5 small regions, and 25 focal positions and a refocus coefficient α are calculated with the center point as a representative point. Subsequently, a refocus image focused on the representative point having the largest α (= most forward) is generated by the arithmetic processing of the above-described equation (5) (S710, S711).

  As described above, at the time of shooting by the imaging apparatus of the first embodiment, in the live view image and the image confirmation display after shooting, the optimal field corresponding to the scene selection selected by the user is determined from the light field information. Display the focus image. Thereby, an imaging device (light field camera) that is easy for the user to shoot can be provided.

<Second Embodiment>
In the second embodiment, a procedure for reproducing and displaying light field information recorded by the imaging apparatus described in the first embodiment will be described.

  When the user gives an instruction to reproduce an image from arbitrary light field information, the single image reproduction process shown in FIG. 12 is started (S1201). The recorded light field information is read and scene select information recorded as additional information is acquired (S1202). A refocus image is generated and displayed by refocus processing optimal for the acquired scene select information (S1203). When the user performs an operation to change the selection of the scene select on the displayed image, the refocus processing optimum for the newly selected scene select is performed (S1204, 1205), and the refocused image is re-executed. Display. Further, the recorded scene select information is changed to the currently selected scene select for recording (S1206). As a result, the image can be reproduced from the next time in the focus state according to the desired scene selection.

  According to the imaging apparatus of the second embodiment, a refocus image can be generated from the recorded light field information. Further, by using the scene select information recorded as the additional information, it is possible to initially display the refocus image in the focus state desired by the user as the default image.

<Other embodiments>
In the first and second embodiments described above, the case where the face determination and recording processing is performed by the imaging apparatus has been described, but the present invention is not limited to this. For example, the above-described processing described with reference to FIGS. 6 to 12 is performed by an external image processing apparatus using image data output from an imaging apparatus that generates image data that can be refocused. Aim can be achieved.

  In addition, even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a scanner, a video camera, etc.), a device (for example, a copying machine, a facsimile device, etc.) composed of a single device. You may apply to.

  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 a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (10)

A taking lens,
An image sensor comprising a plurality of two-dimensionally arranged pixels for photoelectrically converting incident light and outputting image data;
A plurality of microlenses arranged between the photographing lens and the image sensor and corresponding to each of a plurality of regions of the image sensor composed of a predetermined number of pixels;
Refocus image generation means for performing a refocus process for generating an image focused on an arbitrary distance from the image data of the plurality of pixels output from the image sensor;
A selection means for selecting a scene corresponding to the parameter used for the refocus processing;
An image pickup apparatus comprising: a display unit configured to display an image generated by the refocus image generation unit using a parameter corresponding to a scene selected by the selection unit.   The image sensor outputs image data at a constant time interval, and the refocus image generation means uses the parameter corresponding to the scene selected by the selection means when the image data is output, The imaging apparatus according to claim 1, wherein refocus processing is performed on the image data, and the display unit sequentially displays the refocused images on the display unit.   2. The image processing apparatus according to claim 1, further comprising recording means for recording the image data output from the image sensor and the parameter corresponding to the scene selected by the selection means as additional information in association with the image data. Or the imaging device of 2.   The refocus image generation means further reads out the image data recorded by the recording means and the additional information recorded in association with the image data, and uses the read image data and the additional information. The imaging apparatus according to claim 3, wherein the refocus processing is performed.   The scene includes person photographing, and when the person photographing is selected by the selection unit, a parameter for focusing on a face included in the image of the image data is set in the refocus processing. The imaging device according to any one of claims 1 to 4.   The scene includes landscape shooting and night scene shooting, and when either the landscape shooting or night scene shooting is selected, a parameter for deepening the depth of field is set in the refocus processing. The imaging device according to any one of claims 1 to 5. A photographic lens, an image sensor composed of a plurality of pixels arranged in two dimensions for photoelectrically converting incident light to output image data, the photographic lens, and the image sensor are arranged and determined in advance. An image processing device for processing image data output from an imaging device comprising a plurality of microlenses corresponding to each of a plurality of regions of the imaging device comprising a plurality of pixels,
Refocus image generation means for performing a refocus process for generating an image focused on an arbitrary distance from the image data of the plurality of pixels output from the image sensor;
A selection means for selecting a scene corresponding to the parameter used for the refocus processing;
An image processing apparatus comprising: a display unit configured to display an image generated by the refocus image generation unit using a parameter corresponding to the scene selected by the selection unit. A photographic lens, an image sensor composed of a plurality of pixels arranged in two dimensions for photoelectrically converting incident light to output image data, the photographic lens, and the image sensor are arranged and determined in advance. An image processing method for processing image data output from an imaging device including a plurality of microlenses corresponding to each of a plurality of regions of the imaging element including a plurality of pixels,
A refocus image generation step for performing a refocus process for generating an image focused on an arbitrary distance from the image data of the plurality of pixels output from the image sensor;
A selection step for selecting a scene corresponding to the parameter used for the refocus processing by the selection means;
An image processing method comprising: a display step, wherein a display unit displays an image generated in the refocus image generation step using a parameter corresponding to the scene selected in the selection step.   A program for causing a computer to execute each step of the image processing method according to claim 8.   A computer-readable storage medium storing the program according to claim 9.

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