Patent Publication Number: US-9894339-B2

Title: Image processing apparatus, image processing method and program

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an image processing apparatus, an image processing method and a program. 
     Description of the Related Art 
     In general, an imaging apparatus such as a digital camera has an automatic white balance controlling function of automatically adjusting the color tone of a photographed image. According to conventional automatic white balance control, a calculated white balance correction value is applied to an entire image. Hence, in the case of photographing in an environment in which plural light sources exist (for example, photographing with strobe light-emitting), it is difficult to obtain an image having coloring appropriate to each of the light sources. 
     To deal with this, for example, an electronic still camera described in Japanese Patent No. 3540485 compares an image at photographing with strobe light-emitting and an image at photographing without strobe light-emitting for each arbitrary object region to obtain the ratio of data, and determines the degree of contribution of strobe light based on the value of the obtained ratio. Then, according to the degree of contribution, the electronic still camera described in Japanese Patent No. 3540485 selects a white balance correction value for each region of image data obtained by emitting strobe light for light exposure, to thereby perform white balance control. 
     Unfortunately, in the case of the technique described in Japanese Patent No. 3540485, there is a time difference in acquisition timing between image data photographed with strobe light-emitting and image data photographed without strobe light-emitting. Hence, the electronic still camera described in Japanese Patent No. 3540485 has a problem that, for example, in the case where one of an object and a camera is moving, the radiation range and the radiation amount of strobe light are erroneously detected and a coloring discrepancy occurs in a boundary portion of a substance such as the object. Moreover, the electronic still camera described in Japanese Patent No. 3540485 performs development processing after varying a white balance correction value for each region. Hence, other controls such as color reproduction control may not be appropriate to the white balance correction value. As a result, appropriate coloring cannot be sufficiently reproduced. 
     SUMMARY OF THE INVENTION 
     The present invention, which has been made in view of the above-mentioned problem, has an object to provide an image processing apparatus, an image processing method and a program that enable white balance correction appropriate to an image photographed with strobe light-emitting. 
     According to an aspect of the present invention, an image processing apparatus comprises: a first correcting unit that corrects data on a strobe light-emission image photographed with strobe light-emitting, using a first white balance correction value corresponding to environmental light, and generates first white balance correction image data; a second correcting unit that corrects the data on the strobe light-emission image using a second white balance correction value corresponding to strobe light, and generates second white balance correction image data; an acquiring unit that acquires distance information indicating a distance from an imaging unit, of each object included in the strobe light-emission image; a calculating unit that calculates a ratio of a component of the strobe light for each region of the strobe light-emission image, based on distribution characteristics of the strobe light and the distance information; and a combining unit that combines the first white balance correction image data and the second white balance correction image data for each region using a combining ratio according to the component ratio. 
     According to the present invention, white balance correction appropriate to an image photographed with strobe light-emitting is enabled. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a schematic configuration of an imaging apparatus of an embodiment. 
         FIG. 2  is a diagram illustrating a configuration of a WEB correcting unit of the embodiment. 
         FIG. 3  is a diagram illustrating a state where photographing controls by the imaging apparatus are arranged in chronological order. 
         FIG. 4  is a flowchart of white balance correction processing. 
         FIG. 5  is a flowchart of white balance correction value determination processing. 
         FIGS. 6A and 6B  are characteristic diagrams each illustrating an example relation of a color evaluation value for performing white detection. 
         FIG. 7  is a flowchart of strobe light component calculation processing in a first embodiment. 
         FIGS. 8A, 8B and 8C  are diagrams for describing the strobe light component calculation processing. 
         FIGS. 9A and 9B  are diagrams for describing face detection processing. 
         FIG. 10  is a diagram illustrating a relation between a direction normal to an object surface and reflected light of strobe light. 
         FIG. 11  is a flowchart of strobe light component calculation processing of a fourth embodiment. 
         FIGS. 12A and 12B  are diagrams for describing moving region detection processing. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
     First Embodiment 
     Hereinafter, exemplary embodiments of the present invention are described in detail with reference to the drawings. First, an image processing apparatus of the first embodiment is described with reference to  FIG. 1  to  FIG. 8C . The image processing apparatus of the first embodiment is an imaging apparatus  100  such as a digital camera capable of acquiring a distance map (to be described later) including information on a distance to an object. 
       FIG. 1  is a diagram illustrating a schematic configuration of the imaging apparatus  100  of the present embodiment. In  FIG. 1 , the imaging apparatus  100  includes an imaging optical system  101 , an imaging device  102 , an A/D converter  103 , an image processing unit  104 , a system controlling unit  106 , an operating unit  107 , a display unit  108 , a recording unit  109 , a memory unit  110  and a light emitting unit  111 . 
     The imaging optical system  101  includes a diaphragm and a group of lenses including a focus lens. The imaging optical system  101  receives light from the object, and guides the light to the imaging device  102 . The focus lens included in the imaging optical system  101  is driven based on a drive command from a lens drive controlling unit (not illustrated), and enables adjustment of a point of focus. Note that the focus lens may be driven in response to a turning operation of a focus ring. A light flux that has passed through the imaging optical system  101  forms an optical image of the object on the imaging device  102 . 
     The light emitting unit  111  includes: a strobe light emitting unit that emits so-called strobe light; and an auxiliary light source unit that continues in a lighting-up state to assist illumination at photographing. The strobe light emitting unit may be a strobe built in a camera, may be a so-called external strobe not attached to a camera, and may be an external strobe connected by a cable or wirelessly. Light emitting operations (such as emitting strobe light and not emitting strobe light) of the light emitting unit  111  are controlled by the system controlling unit  106 . 
     The imaging device  102  is an imaging device including a CCD and a CMOS, has a surface covered by RGB color filters arranged in, for example, Bayer layout, and is capable of color photography. The imaging device  102  converts the received light flux into an electrical signal, and outputs the electrical signal as an analog signal to the A/D converter  103 . The A/D converter  103  is a converter for converting the analog signal from the imaging device  102  into a digital signal. The A/D converter  103  outputs the converted digital signal to the image processing unit  104 . 
     The operating unit  107  is an operating device including various switches, various dials, and a shutter button provided to the imaging apparatus  100 . The operating unit  107  enables a photographer to input operation commands for photographing parameter settings and a photographing operation. An operation input signal that is given by the photographer through the operating unit  107  is output to the system controlling unit  106 . Note that the shutter button includes a switch capable of being pressed halfway and pressed fully. 
     The display unit  108  includes a liquid crystal display (LCD), displays an image at photographing transferred from the system controlling unit  106  and an image stored in the recording unit  109 , and displays various setting screens. A detachable recording medium such as a memory card compliant with various standards is attached to the recording unit  109 . The recording unit  109  records image data transferred through the system controlling unit  106 , into the recording medium, and reads the recorded data out of the recording medium. 
     The image processing unit  104  performs various image processing operations including white balance correction processing and face detection processing. The white balance correction processing by the image processing unit  104  may be achieved by a circuit configuration of a white balance correcting unit  105 , and may be achieved by a group of programs executed by the system controlling unit  106 . Hereinafter, in the present embodiment, the white balance is represented as “WEB” as appropriate. A detailed configuration of the WEB correcting unit  105  and a method of determining a white balance correction value are described later. Moreover, the face detection processing by the image processing unit  104  may be achieved by a circuit configuration of a face detecting unit  112  or the like, and may be achieved by a group of programs executed by the system controlling unit  106 . The face detection processing is described later in a second embodiment. The image processing unit  104  performs image processing on a group of digital signals supplied from the A/D converter  103 , based on a control command from the system controlling unit  106 , and generates image data for recording and image data for display. The image processing performed by the image processing unit  104  includes: processing of applying color gain to image data after WEB correction to convert the image data into one of a color difference signal and a RGB signal; and development processing such as gamma correction processing. Note that, at the time of performing the image processing, the image processing unit  104  stores the image data into the memory unit  110  as appropriate, and reads out the image data as appropriate. 
     Moreover, the image processing unit  104  acquires data on a distance map holding information on a distance to the object, based on a signal imaged by the imaging device  102 . Here, an acquiring method when the image processing unit  104  acquires the distance map data is described. In the imaging device  102 , plural microlenses are arranged in a lattice-like pattern, and plural divided pixels are provided below each microlens. For example, in the case where two right and left divided pixels in the horizontal direction are provided below each microlens, first, the image processing unit  104  calculates a correlation value of a value of the left divided pixel and a value of the right divided pixel that are provided within the same line in the horizontal direction. Then, based on a parallax between divided pixels having the highest correlation value and information on a pixel pitch of the imaging device  102 , the image processing unit  104  calculates a distance in the real space, that is, a distance in the depth direction in the real space from the imaging device  102  to the object. The image processing unit  104  repetitively performs such processing as described above for each arbitrary region, to thereby generate a distance map including distance information of each arbitrary region. In the present embodiment, the arbitrary region used for acquiring the distance map is defined, as an example, as a region of each block obtained by dividing an image as described later. Accordingly, in this case, the resolution of the distance map is equal to the resolution of each block obtained by dividing the image. 
     The system controlling unit  106  includes a CPU, and performs operation control of the entire system such as drive control of the focus lens in the imaging optical system  101 , according to a control program stored in the memory unit  110 . The system controlling unit  106  also performs signal input/output among components, for example, acquires data obtained by the image processing by the image processing unit  104  and lens position information of the imaging optical system  101 . 
     The memory unit  110  includes a ROM and a RAM. The ROM of the memory unit  110  stores: basic software that is a system program; programs for the system controlling unit  106  and the image processing unit  104  to execute various controls and various signal processing operations to be described later; and various pieces of data used during the execution of the programs. The programs executed by the system controlling unit  106  and the image processing unit  104  are developed in the RAM of the memory unit  110 , and the RAM of the memory unit  110  serves as a data area used by the programs. In the present embodiment, examples of various pieces of data stored in the ROM of the memory unit  110  include: data on distribution characteristics of strobe light; data on an average standard reflectance of a general substance; data on a reflectance of a human face; and data on a three-dimensional model of a face, although the details thereof are described later. Examples of pieces of data temporarily stored in the RAM of the memory unit  110  include: photographed image data; image data at photographing without strobe light-emitting; image data at photographing with strobe light-emitting; and data on a distance map at photographing with strobe light-emitting, although the details thereof are described later. 
     Hereinabove, the schematic configuration of the imaging apparatus  100  of the present embodiment has been described. Next, the configuration of the WEB correcting unit  105  of the image processing unit  104  and the method of determining a white balance correction value are described in detail.  FIG. 2  is a diagram illustrating the configuration of the WEB correcting unit  105 . In  FIG. 2 , the WEB correcting unit  105  includes an input unit  201 , a first WEB correction value determining unit  206 , a first correcting unit  207 , a second WEB correction value determining unit  208 , a second correcting unit  209 , a strobe light component calculating unit  210 , a combining ratio calculating unit  211 , a combining unit  212  and an output unit  213 . 
     The input unit  201  reads image data  202  at photographing without strobe light-emitting, data on distribution characteristics  203  of strobe light, data on a distance map  204  at photographing with strobe light-emitting and image data  205  at photographing with strobe light-emitting out of the memory unit  110 , and outputs these pieces of data to each unit. The details of how these pieces of data are acquired and used are described later. 
       FIG. 3  is a diagram illustrating a state where photographing controls by the system controlling unit  106  are arranged in chronological order. In  FIG. 3 , before a state  301  (hereinafter, represented as SW 1 ) where the shutter button is pressed halfway, the system controlling unit  106  controls the imaging optical system  101  and the imaging device  102  to photograph an image  310  for so-called live view display for each frame cycle. In the state of SW 1  where the shutter button is pressed halfway, the system controlling unit  106  controls the imaging optical system  101  to perform an AF lock  311  and an AE lock  312 . Note that the AF lock  311  is control for locking a focal distance in autofocus control for driving the focus lens in the imaging optical system  101 . The AE lock  312  is control for locking an exposure value in automatic exposure control. After a holding period  302  during which the state of SW 1  is held, when a state  303  (hereinafter, represented as SW 2 ) where the shutter button is pressed fully comes, the system controlling unit  106  controls the light emitting unit  111  to perform test light-emitting  314 . After that, the system controlling unit  106  controls the imaging optical system  101 , the imaging device  102  and the light emitting unit  111  to perform main light exposure  315  for actually photographing an image of the object. 
     Here, before the test light-emitting  314  is performed, the system controlling unit  106  controls the imaging optical system  101  and the imaging device  102  to perform light exposure also in a period that is illustrated as environmental light exposure  313  in  FIG. 3 . In the present embodiment, image data that is exposed to light in the period of the environmental light exposure  313  corresponds to the image data  202  at photographing without strobe light-emitting in  FIG. 2 , and image data that is exposed to light in the period of the main light exposure  315  corresponds to the image data  205  at photographing with strobe light-emitting in  FIG. 2 . The image data  202  at photographing without strobe light-emitting is image data acquired by imaging by the imaging device  102  using environmental light without strobe light-emitting by the light emitting unit  111 . The image data  205  at photographing with strobe light-emitting is image data acquired by imaging by the imaging device  102  with strobe light-emitting by the light emitting unit  111 . Note that the image data  202  at photographing without strobe light-emitting may be photographed image data that is exposed to the environmental light after the main light exposure  315 . 
     Returning to the description of  FIG. 2 , the first WEB correction value determining unit  206  determines a WEB correction value corresponding to the environmental light based on the image data  202  at photographing without strobe light-emitting, and outputs data on the WEB correction value to the first correcting unit  207 . The second WEB correction value determining unit  208  determines a WEB correction value corresponding to the strobe light based on the image data  205  at photographing with strobe light-emitting, and outputs data on the WEB correction value to the second correcting unit  209 . 
     The first correcting unit  207  performs WEB correction on the image data  205  at photographing with strobe light-emitting, based on the WEB correction value corresponding to the environmental light. The second correcting unit  209  performs WEB correction on the image data  205  at photographing with strobe light-emitting, based on the WEB correction value corresponding to the strobe light. The image data after the WEB correction by the first correcting unit  207  and the image data after the WEB correction by the second correcting unit  209  are output to the combining unit  212 . 
     The strobe light component calculating unit  210  calculates a strobe light component for each region (to be described later) of the image data  205  at photographing with strobe light-emitting, from the data on the distribution characteristics  203  of the strobe light and the data on the distance map  204  acquired with strobe light-emitting, and outputs the strobe light component to the combining ratio calculating unit  211 . The detail of the distribution characteristics  203  of the strobe light is described later. 
     The combining ratio calculating unit  211  calculates a combining ratio for image combining, based on the image data  205  at photographing with strobe light-emitting and the strobe light component, and outputs the combining ratio to the combining unit  212 . The combining unit  212  combines the image data after the WEB correction by the first correcting unit  207  and the image data after the WEB correction by the second correcting unit  209 , based on the combining ratio output by the combining ratio calculating unit  211 . The image data combined by the combining unit  212  is sent as final white balance correction image data to the output unit  213 . The output unit  213  outputs the white balance correction image data to a processing unit in the subsequent stage. 
     Hereinabove, the configuration of the WEB correcting unit  105  inside of the imaging apparatus  100  of the first embodiment has been described. Next, a WEB correcting operation by the WEB correcting unit  105  of the present embodiment is described.  FIG. 4  is a flowchart of correction processing performed by the WEB correcting unit  105 . 
     First, in Step S 401 , the first WEB correction value determining unit  206  determines first WEB correction values corresponding to environmental light, based on the image data  202  at photographing without strobe light-emitting. The WEB correction value determination processing at photographing without strobe light-emitting in Step S 401  is described in detail with reference to  FIG. 5 ,  FIGS. 6A and 6B .  FIG. 5  is a flowchart of the WEB correction value determination processing.  FIGS. 6A and 6B  are characteristic diagrams each illustrating a relation of a color evaluation value for performing white detection,  FIG. 6A  illustrates a white detection range at photographing without strobe light-emitting, and  FIG. 6B  illustrates a white detection range at photographing with strobe light-emitting. 
     In Step S 501  in the flowchart of  FIG. 5 , the first WEB correction value determining unit  206  divides an image of the received image data  202  at photographing without strobe light-emitting into an arbitrary number n (1 to n) of blocks. In the present embodiment, the block division number “n” for the image data  202  at photographing without strobe light-emitting is made equal to a block division number “m” (to be described later) for the image data  205  at photographing with strobe light-emitting. After Step S 501 , the first WEB correction value determining unit  206  advances the processing to Step S 502 . In Step S 502 , the first WEB correction value determining unit  206  averages pixel values of each color for each block, and calculates respective color average values (R[i], G[i], B[i]) of RGB. Note that [i] represents an i th  block of the (1 to n) blocks. Further, the first WEB correction value determining unit  206  calculates color evaluation values (Cx[i], Cy[i]) according to the following Expression (1).
 
 Cx[i ]=( R[i]−B[i ])/ Y[i]× 1024
 
 Cy[i ]=( R[i]+B[i]− 2 G[i ])/ Y[i]× 1024   Expression (1)
 
where Y[i]=(R[i]+2G[i]+B[i])/4
 
     After Step S 502 , the first WEB correction value determining unit  206  advances the processing to Step S 503 . In Step S 503 , the first WEB correction value determining unit  206  performs white detection using graphs having coordinate axes as illustrated in  FIGS. 6A and 6B . In  FIGS. 6A and 6B , the negative direction of the x-coordinate (Cx) represents a color evaluation value when the color of a high color temperature object is photographed, and the positive direction thereof represents a color evaluation value when the color of a low color temperature object is photographed. Moreover, the y-coordinate (Cy) represents the degree of a green component of a light source, and the G component becomes larger toward the negative direction of the y-coordinate (Cy), that is, a higher degree of the G component indicates that the light source is a fluorescent light. 
     Moreover, in Step S 503 , the first WEB correction value determining unit  206  determines whether or not the color evaluation values (Cx[i], Cy[i]) of the i th  block calculated in Step S 502  are included in a preset white detection range  601  illustrated in  FIG. 6A . Because the environmental light is an unknown light source, the white detection range  601  is defined with reference to color evaluation values that are calculated in advance from images obtained by photographing a white object under different light sources. Then, if it is determined in Step S 503  that the color evaluation values (Cx[i], Cy[i]) of the i th  block are included in the preset white detection range  601 , the first WEB correction value determining unit  206  advances the processing to Step S 504 . On the other hand, if it is determined in Step S 503  that the color evaluation values (Cx[i], Cy[i]) of the i th  block are not included in the preset white detection range  601 , the first WEB correction value determining unit  206  advances the processing to Step S 505 . 
     In Step S 504 , the first WEB correction value determining unit  206  determines that the i th  block is white, integrates the color average values (R[i], G[i], B[i]) of this block, and obtains respective integral values (SumR, SumG, SumB) of the color average values. Note that the processing of Steps S 503  and S 504  can be represented by the following Expression (2). 
     
       
         
           
             
               
                 
                   
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     Here, in Expression (2), if the color evaluation values (Cx[i], Cy[i]) are included in the white detection range  601 , the first WEB correction value determining unit  206  sets “1” to Sw[i] in Expression (2). On the other hand, if the color evaluation values (Cx[i], Cy[i]) are not included in the white detection range  601 , the first WEB correction value determining unit  206  sets “0” to Sw[i] in Expression (2). That is, if “1” is set to Sw[i], the first WEB correction value determining unit  206  integrates the color average values (R[i], G[i], B[i]). On the other hand, if “0” is set to Sw[i], the first WEB correction value determining unit  206  does not integrate the color average values (R[i], G[i], B[i]). After Step S 504 , the first WEB correction value determining unit  206  advances the processing to Step S 505 . 
     In Step S 505 , the first WEB correction value determining unit  206  determines whether or not the processing of Steps S 502  to S 504  has been performed on the total blocks. If it is determined in Step S 505  that an unprocessed block exists, the first WEB correction value determining unit  206  returns the processing to Step S 502 , and repeats processing similar to the above. On the other hand, if it is determined in Step S 505  that the processing of Steps S 502  to S 504  has been performed on the total blocks, the first WEB correction value determining unit  206  advances the processing to Step S 506 . 
     In Step S 506 , the first WEB correction value determining unit  206  calculates first WEB correction values (WEBCol_R 1 , WEBCol_G 1 , WEBCol_B 1 ) according to Expression (3), from respective integral values (SumR 1 , SumG 1 , SumB 1 ) of the color average values obtained for the total blocks. Note that the integral values (SumR 1 , SumG 1 , SumB 1 ) are values obtained by integrating, for the total blocks, the respective integral values (SumR, SumG, SumB) of the color average values of each block.
 
WEB Col _ R 1=Sum Y 1×1,024/Sum R 1
 
WEB Col _ G 1=Sum Y 1×1,024/Sum G 1
 
WEB Col _ B 1=Sum Y 1×1,024/Sum B 1  Expression (3)
 
where SumY 1 =(SumR 1 +2×SumG 1 +SumB 1 )/4
 
     Note that, although the example in which the first WEB correction values are calculated from the image data  202  at photographing without strobe light-emitting is described here, in the case where the environmental light is known (for example, photographing in a studio), the first WEB correction values may be set in advance. 
     Returning to the description of  FIG. 4 , after Step S 401 , the processing advances to Step S 402 , and the processing of Step S 402  is performed by the second WEB correction value determining unit  208 . In Step S 402 , the second WEB correction value determining unit  208  determines second WEB correction values corresponding to strobe light, based on the image data  205  at photographing with strobe light-emitting. The processing of determining the second WEB correction values is performed according to a method similar to the above-mentioned processing of determining the first WEB correction values. Note that, unlike the processing of determining the first WEB correction values, the processing of determining the second WEB correction values is performed using a white detection range  602  for the strobe light as illustrated in  FIG. 6B . This is because the environmental light is basically an unknown light source whereas the strobe light is a known light source and because the range of the strobe light can be limited as indicated by the white detection range  602  in  FIG. 6B . Note that WEB correction values corresponding to the strobe light as the second WEB correction values may be preset as known values. 
     After Step S 402 , the processing advances to Step S 403 , and the processing of Step S 403  is performed by the strobe light component calculating unit  210 . In Step S 403 , the strobe light component calculating unit  210  calculates a strobe light component of each block of the image data  205  at photographing with strobe light-emitting, from the data on the distribution characteristics  203  of the strobe light and the data on the distance map  204  acquired with strobe light-emitting. 
     Here, the strobe light component calculation processing of Step S 403  is described in detail with reference to  FIG. 7  and  FIGS. 8A to 8C .  FIG. 7  is a flowchart of the strobe light component calculation processing.  FIG. 8A  is a diagram illustrating an image  801  (image data  205 ) at photographing with strobe light-emitting and an example block (block P) whose strobe light component is to be calculated.  FIG. 8B  is a diagram illustrating an example division into blocks that are processing units in the strobe light component calculation processing.  FIG. 8C  is a diagram illustrating an example of the distribution characteristics of the strobe light. 
     First, in the flowchart of  FIG. 7 , as the processing of Step S 701 , the strobe light component calculating unit  210  acquires lens focal distance information at photographing with strobe light-emitting from the system controlling unit  106 . That is, because the system controlling unit  106  performs autofocus control for driving the focus lens in the imaging optical system  101  and thus holds the focal distance information, the strobe light component calculating unit  210  acquires the focal distance information therefrom. After Step S 701 , the strobe light component calculating unit  210  advances the processing to Step S 702 . 
     In Step S 702 , the strobe light component calculating unit  210  divides the image data  205  at photographing with strobe light-emitting into a number m of blocks, the number m being equal to the block division number adopted at creating the distance map  204 . This makes the resolution of the distance map  204  equal to the resolution of each block obtained by dividing the image data  205  at photographing with strobe light-emitting.  FIG. 8B  is a diagram schematically illustrating a state where the image data  205  at photographing with strobe light-emitting including plural pixels  803  is divided for each block of a range  804  indicated by thick lines in  FIG. 8B , the range  804  corresponding to each block of the distance map  204 . Note that, in the image data  205  at photographing with strobe light-emitting like the image  801  in  FIG. 8A , for example, the block P that is part of an image of an object  802  indicates one of the blocks divided as described above. After Step S 702 , the strobe light component calculating unit  210  advances the processing to Step S 703 . 
     In Step S 703 , the strobe light component calculating unit  210  reads distance information (distance information in the depth direction from the strobe light source) on the distance map  204  corresponding to each block divided in Step S 702  out of the memory unit  110 . After Step S 703 , the strobe light component calculating unit  210  advances the processing to Step S 704 . 
     In Step S 704 , the strobe light component calculating unit  210  calculates a strobe light component. Specifically, the strobe light component calculating unit  210  calculates a strobe light component from the coordinates of a block corresponding to (x, y) coordinates of the distance map  204 , the focal distance information acquired in Step S 701 , the depth distance information on the distance map  204  acquired in Step S 703  and the distribution characteristics  203  of the strobe light. 
     Here, the distribution characteristics  203  of the strobe light are characteristics (as illustrated in  FIG. 8C ) indicating how a light quantity Ys that reaches the object changes depending on the distance and the direction from the strobe light source. Note that  FIG. 8C  is described assuming the case of photographing in the state where the strobe light is emitted toward the object without changing the radiation direction of the strobe light and the case of photographing in the state where the emitted light quantity of the strobe light source and the spreading angle of the strobe light are not changed and kept constant. As is apparent from  FIG. 8C , the light quantity Ys of the strobe light that reaches the object becomes larger as the distance from the strobe light source to the object becomes shorter, and, conversely, becomes smaller as the distance therefrom to the object becomes longer. Moreover, the direction from the strobe light source can be expressed by an angle formed by: the optical axis of one of a lens optical system and a reflective optical system included in the strobe light source (referred to as the optical axis of the strobe light source); and a line segment connecting from a light emitting point of the strobe light source to the object (referred to as the line segment from the light source to the object). As the angle formed by the optical axis of the strobe light source and the line segment from the light source to the object becomes smaller (the position of the object becomes closer to the optical axis of the strobe light source), the light quantity Ys that reaches the object becomes larger. Conversely, as the angle formed by the optical axis of the strobe light source and the line segment from the light source to the object becomes larger (the position of the object becomes farther from the optical axis of the strobe light source), the light quantity Ys that reaches the object becomes smaller. Moreover, the focal distance at photographing corresponds to the angle of view at photographing. As the focal distance becomes longer (larger), the angle of view becomes narrower. Conversely, as the focal distance becomes shorter (smaller), the angle of view becomes wider. That is, as the focal distance becomes longer (the angle of view becomes narrower), the proportion of an image of the object to a photographed image becomes larger. Conversely, as the focal distance becomes shorter (the angle of view becomes wider), the proportion of the image of the object to the photographed image becomes smaller. Moreover, if the focal distance is long (the angle of view is narrow), a photographed image is obtained in a narrow range with respect to the spreading angle of the strobe light. Conversely, if the focal distance is short (the angle of view is wide), the photographed image is obtained in a wide range with respect to the spreading angle of the strobe light. Further, in the present embodiment, the size of the distance map corresponds to the size of a sensor surface of the imaging device  102 , and the resolution of the distance map is equal to the resolution based on the above-mentioned block division number. Accordingly, if the focal distance changes, (x, y) coordinates of the object image with respect to (x, y) coordinates of the distance map also change, and the direction of the object with respect to the optical axis of the strobe light source also changes. As an example, even if the strobe light component of the block P illustrated in  FIG. 8A  is Ysp in  FIG. 8C  at a given focal distance, if the focal distance changes, the direction of the block P with respect to the optical axis of the strobe light source also changes, and the strobe light component becomes different. Note that, although  FIG. 8C  illustrates the case where distribution characteristics in the x-axis direction are the same as distribution characteristics in the y-axis direction, the distribution characteristics in the x-axis direction may be different from the distribution characteristics in the y-axis direction depending on the shape of the strobe. 
     Then, the strobe light component calculating unit  210  calculates a strobe light component Ys[i] of each of the (1 to m) divided blocks according to a function g in Expression (4) using the following four arguments. In Expression (4), the four arguments are coordinates (x[i], y[i]) of the distance map corresponding to each block, depth distance information z(x[i], y[i]) on the distance map and a focal distance f. That is, the strobe light component calculating unit  210  calculates the object position in the real space based on these four arguments, and obtains the strobe light component Ys[i] by applying information on the distribution characteristics.
 
 Ys[i]=g ( x[i],y[i],z ( x[i],y[i ]), f )   Expression (4)
 
     Note that, although the example in which the above four arguments are used to calculate the strobe light component is described here, other arguments concerning the strobe light component may be used. Meanwhile, although the calculation accuracy of the strobe light component is lower, only the depth distance information may be used as an argument on the assumption that every object is located in front of the light source. Moreover, although the example in which the strobe light component is calculated according to the function using the plural arguments is described here, the strobe light component may be held as a table, and may be determined by referring to the table according to conditions. After Step S 704 , the strobe light component calculating unit  210  advances the processing to Step S 705 . 
     In Step S 705 , the strobe light component calculating unit  210  determines whether or not the processing of Steps S 703  and S 704  has been performed on the total blocks. If it is determined in Step S 705  that an unprocessed block exists, the strobe light component calculating unit  210  returns the processing to Step S 703 , and repeats processing similar to the above. On the other hand, if it is determined in Step S 705  that the processing of Steps S 703  and S 704  has been performed on the total blocks, the strobe light component calculating unit  210  ends the strobe light component calculation processing illustrated in the flowchart of  FIG. 7 . 
     If the strobe light component calculation processing in the flowchart of  FIG. 7  is ended, the processing by the image processing unit  104  advances to image combining ratio calculation processing of Step S 404  in  FIG. 4 , and the processing of Step S 404  is performed by the combining ratio calculating unit  211 . In the processing of Step S 404 , the combining ratio calculating unit  211  calculates a combining ratio α used for image combining. Here, the combining ratio calculating unit  211  calculates the combining ratio α using the strobe light component Ys[i] of each block calculated in Step S 403  and the image data  205  at photographing with strobe light-emitting. First, the combining ratio calculating unit  211  divides the image data  205  at photographing with strobe light-emitting into the number m of blocks similarly to the strobe light component calculation processing, averages pixel values of each color of RGB for each block, and calculates color average values (Rt[i], Gt[i], Bt[i]). Then, the combining ratio calculating unit  211  calculates a luminance value Yt[i] of each block according to the following Expression (5).
 
 Yt[i]= 0.3× Rt[i]+ 0.6× Gt[i]+ 0.1× Bt[i]    Expression (5)
 
     Here, the luminance value Yt[i] of each block thus calculated is defined as the sum of the strobe light component and the environmental light component of each block. The combining ratio calculating unit  211  further calculates the ratio of the strobe light component Ys[i] in Expression (4) to the sum Yt[i] of the strobe light component and the environmental light component according to the following Expression (6), to thereby obtain a combining ratio α[i] of each block.
 
α[ i]=Ys[i]/Yt[i]   Expression (6)
 
     Subsequently, if the combining ratio calculation processing of Step S 404  is ended, the processing by the image processing unit  104  advances to corrected image data generating processing of Step S 405 , and the processing of Step S 405  is performed by the first correcting unit  207  and the second correcting unit  209 . In the processing of Step S 405 , the first correcting unit  207  generates first corrected image data Yuv 1  from the image data  205  at photographing with strobe light-emitting, using the first WEB correction values corresponding to the environmental light determined in Step S 401 . Moreover, in Step S 405 , the second correcting unit  209  generates second corrected image data Yuv 2  from the image data  205  at photographing with strobe light-emitting, using the second WEB correction values corresponding to the strobe light determined in Step S 402 . Note that the first correcting unit  207  and the second correcting unit  209  also perform development processing from RGB to YUV. 
     Subsequently, if the corrected image data generating processing of Step S 405  is ended, the processing by the image processing unit  104  advances to image combining processing of Step S 406 , and the processing of Step S 406  is performed by the combining unit  212 . In Step S 406 , the combining unit  212  combines the corrected image data Yuv 1  and the corrected image data Yuv 2  using the combining ratio α[i] of each block calculated in Step S 404 , and generates combined image data Yuv 3 . Specifically, the combining unit  212  calculates color evaluation values (Y 3 [ i ], u 3 [ i ], v 3 [ i ]) of the combined image data Yuv 3  according to the following Expression (7). (Y 1 [ i ], u 1 [ i ], v 1 [ i ]) in Expression (7) are color evaluation values of the corrected image data Yuv 1 , and (Y 2 [ i ], u 2 [ i ], v 2 [ i ]) in Expression (7) are color evaluation values of the corrected image data Yuv 2 .
 
 Y 3[ i]=Y 1[ i ]×(1−α[ i ])+ Y 2[ i]×α[i] 
 
 u 3[ i]=u 1[ i ]×(1−α[ i ])+ u 2[ i]×α[i] 
 
 v 3[ i]=v 1[ i ]×(1−α[ i ])+ v 2[ i]×α[i]    Expression (7)
 
     Here, in order to reduce a coloring discrepancy that occurs in a boundary portion between blocks, the combining ratio calculating unit  211  may further perform pixel interpolation processing in Step S 404 , to thereby calculate a combining ratio β[j] of each pixel from the combining ratio α[i] of each block. Note that [j] represents a j th  pixel of the pixels in each block. Specifically, the combining ratio calculating unit  211  calculates the combining ratio β[j] of each pixel from the combining ratio α[i] of each block, using bilinear interpolation as the pixel interpolation processing. Moreover in this case, in Step S 406 , the combining unit  212  combines the corrected image data Yuv 1  and the corrected image data Yuv 2  using the combining ratio β[j] of each pixel, and generates the combined image data Yuv 3 . Color evaluation values (Y 3 [ j ], u 3 [ j ], v 3 [ j ]) of the combined image data Yuv 3  are calculated from color evaluation values (Y 1 [ j ], u 1 [ j ], v 1 [ j ]) of the corrected image data Yuv 1  and color evaluation values (Y 2 [ j ], u 2 [ j ], v 2 [ j ]) of the corrected image data Yuv 2 . That is, the combining unit  212  calculates the color evaluation values (Y 3 [ j ], u 3 [ j ], v 3 [ j ]) of the combined image data Yuv 3  according to the following Expression (8).
 
 Y 3[ j]=Y 1[ j ]×(1−β[ j ])+ Y 2[ j]×β[j] 
 
 u 3[ j]=u 1[ j ]×(1−β[ j ])+ u 2[ j]×β[j] 
 
 v 3[ j]=v 1[ j ]×(1−β[ j ])+ v 2[ j]×β[j]    Expression (8)
 
     As has been described above, the image processing unit  104  of the present embodiment calculates the strobe light component from the distance map and the distribution characteristics of the strobe light. Consequently, according to the present embodiment, for example, even if one of the object and the imaging apparatus moves at photographing, a coloring discrepancy in a boundary portion of the object can be reduced, and appropriate coloring can be given to both the main object and the background. Note that, although  FIG. 2  illustrates the configuration example in which the image processing unit  104  includes the first and second WEB correction value determining units  206  and  208  and the first and second correcting units  207  and  209 , the present invention is not limited thereto, and the image processing unit  104  may include one WEB correction value determining unit and one correcting unit. In the case of using one WEB correction value determining unit and one correcting unit, the following time-division sequential processing is performed. That is, processing similar to the processing by the first WEB correction value determining unit  206  and the first correcting unit  207  is first performed, and processing similar to the processing by the second WEB correction value determining unit  208  and the second correcting unit  209  is then performed. Moreover, although the example in which image data is divided into plural blocks and processing is performed on a block basis is described in the present embodiment, the present invention is not limited thereto, and processing may be performed on a pixel basis considering the processing time and the image quality. 
     Second Embodiment 
     Next, an image processing apparatus of the second embodiment is described. In the image processing apparatus of the second embodiment, a reflectance of the object is further applied to the processing by the strobe light component calculating unit  210  described in the first embodiment. Hereinafter, in the image processing apparatus of the second embodiment, only processing different from the processing in the first embodiment is described, and description of the same processing as the processing in the first embodiment is omitted. 
     In the image processing apparatus of the second embodiment, as the processing of Step S 704  in the flowchart of  FIG. 7 , the strobe light component calculating unit  210  calculates the strobe light component Ys[i] of each block according to the following Expression (9) obtained by applying a reflectance r of the object to Expression (4). Note that the reflectance r of the object is defined as a standard reflectance that is an average value of a general substance stored in advance in the memory unit  110 .
 
 Ys[i]=g ( x[i],y[i],z ( x[i],y[i ]), f )× r    Expression (9)
 
     Moreover, in the second embodiment, the strobe light component calculating unit  210  can calculate the strobe light component considering, for example, a reflectance of a human face instead of the standard reflectance.  FIG. 9A  is a schematic diagram illustrating an example case where a face is detected from a photographed image. The face detecting unit  112  included in the image processing unit  104  detects a human image region  901  that is the object, from image data at photographing with strobe light-emitting, and further detects a face image to identify a face image region  902 . With regard to blocks corresponding to the face image region  902  detected by the face detecting unit  112 , the strobe light component calculating unit  210  of the WEB correcting unit  105  calculates the strobe light component Ys[i] using the reflectance of the human face stored in advance in the memory unit  110 . 
     As has been described above, according to the second embodiment, the reflectance of the object is considered at calculating the strobe light component. Hence, the calculation accuracy of the strobe light component can be enhanced, and more appropriate white balance correction is possible. Moreover, the image processing apparatus of the second embodiment detects the human face image region from the photographed image, and calculates the strobe light component considering the reflectance of the human face with regard to the face image region. Hence, more appropriate WEB correction is possible for, particularly, the human face. 
     Third Embodiment 
     Next, an image processing apparatus of the third embodiment is described. In the image processing apparatus of the third embodiment, a reflection direction of the strobe light on the object surface is further applied to the processing by the strobe light component calculating unit  210  described in the second embodiment. Hereinafter, in the image processing apparatus of the third embodiment, only processing different from the processing in the second embodiment is described, and description of the same processing as the processing in the second embodiment is omitted. 
       FIG. 10  is a diagram illustrating a relation between a direction normal to the object surface and reflected light of the strobe light. First, a method of calculating a reflection angle θ of the strobe light to the object surface is described. As illustrated in  FIG. 10 , in the case where strobe light  1003  enters a point  1002  on an object surface  1001 , the strobe light is reflected on the point  1002  on the object surface  1001  to become reflected light  1004 . The reflection angle θ of the reflected light  1004  to the object surface  1001  can be calculated by estimating a normal vector  1005  at the point  1002  from the surface shape of the object and obtaining an angle formed by the strobe light and the normal. Accordingly, a reflected light component of the strobe light that can be actually observed from the imaging apparatus, of a reflected light component of the reflected light  1004  is such a reflected light component  1006  as illustrated in  FIG. 10 . For simplification of description,  FIG. 10  illustrates the entrance and the reflection of the strobe light  1003  on the object surface  1001  in the form of a two-dimensional plane including the strobe light  1003 , the reflected light  1004  and the normal, but, originally, the entrance and the reflection of the strobe light  1003  are phenomena in a three-dimensional space. Accordingly, the normal vector  1005  and the reflected light component  1006  are actually obtained so as to suit the three-dimensional space. 
     Here, the surface shape of the object can be calculated by performing interpolation processing on the distance map. That is, in Step S 704  in the flowchart of  FIG. 7 , the strobe light component calculating unit  210  calculates the strobe light component Ys[i] of each block according to the following Expression (10) obtained by applying the reflection angle θ of the strobe light to Expression (9).
 
 Ys[i]=g ( x[i],y[i],z ( x[i],y[i ]), f )×cos 2θ× r    Expression (10)
 
     Moreover, in the third embodiment, if the face detecting unit  112  included in the image processing unit  104  detects a face image from image data at photographing with strobe light-emitting, the face detecting unit  112  further detects the positions of organs such as eyes and a mouth from the face image region. In this case, the strobe light component calculating unit  210  applies such a three-dimensional face model as illustrated in  FIG. 9B , based on information on the positions of the organs such as eyes and a mouth detected by the face detecting unit  112 , to thereby calculate a normal vector. Note that data on the three-dimensional face model is stored in advance in the memory unit  110 . Then, the strobe light component calculating unit  210  defines the normal vector as a reflected light component. 
     As has been described above, according to the third embodiment, the reflection direction of the strobe light on the object surface is considered at calculating the strobe light component. Hence, the calculation accuracy of the strobe light component can be enhanced, and more appropriate white balance correction is possible. Moreover, the image processing apparatus of the third embodiment calculates the strobe light component considering the reflection direction of the strobe light on the human face, based on the human face image region detected from the photographed image. Hence, more appropriate WEB correction is possible for, particularly, the human face. 
     Fourth Embodiment 
     Next, an image processing apparatus of the fourth embodiment is described. The image processing apparatus of the fourth embodiment detects movements of the object and the imaging apparatus and switches strobe light component calculating methods according to the movement detection result, at the time of the processing by the strobe light component calculating unit  210  described in the first embodiment. 
     Hereinafter, the image processing apparatus of the fourth embodiment is described with reference to  FIG. 11 ,  FIGS. 12A and 12B .  FIG. 11  is a flowchart of processing by the strobe light component calculating unit  210  in the fourth embodiment. Note that, in the flowchart of  FIG. 11 , the same processing as the processing in the flowchart of  FIG. 7  used to describe the first embodiment is denoted by the same reference sign as the reference sign in  FIG. 7 , and description thereof is omitted as appropriate. Moreover,  FIGS. 12A and 12B  are schematic diagrams for describing moving region detection processing of detecting movements of the object and the imaging apparatus from a photographed image. 
     In the flowchart of  FIG. 11 , upon completion of the acquisition of the focal distance information in Step S 701 , the strobe light component calculating unit  210  advances the processing to Step S 1101 . In Step S 1101 , as illustrated in  FIG. 12A , the strobe light component calculating unit  210  identifies an object region  1201  at photographing without strobe light-emitting and an object region  1202  at photographing with strobe light-emitting. Then, the strobe light component calculating unit  210  detects such a moving region  1203  as illustrated in  FIG. 12B  from the object region  1201  at photographing without strobe light-emitting and the object region  1202  at photographing with strobe light-emitting. At this time, the moving region  1203  is detected by, for example, comparing the image data  202  at photographing without strobe light-emitting and the image data  205  at photographing with strobe light-emitting and determining whether or not a difference between the image data  202  and the image data  205  is equal to or more than a predetermined amount. Note that, at this time, the strobe light component calculating unit  210  compares these pieces of image data after subtracting the strobe light component from the image data  205  at photographing with strobe light-emitting, considering influences by the strobe light. Then, the strobe light component calculating unit  210  detects, as the moving region  1203 , a region in which the difference between the image data  202  and the image data  205  is equal to or more than the predetermined amount. Upon completion of the detection of the moving region in Step S 1101 , the strobe light component calculating unit  210  advances the processing to Step S 702 . 
     In Step S 702 , the strobe light component calculating unit  210  divides both the image data  205  at photographing with strobe light-emitting and the image data  202  at photographing without strobe light-emitting into plural blocks, in a manner similar to the manner in the first embodiment. Upon completion of the division of the pieces of image data in Step S 702 , the strobe light component calculating unit  210  advances the processing to Step S 1102 . 
     In Step S 1102 , the strobe light component calculating unit  210  determines whether or not the moving region detected in Step S 1101  is included in the processing target block. If the moving region is included in the processing target block, the strobe light component calculating unit  210  advances the processing to Step S 703 . Then, the strobe light component calculating unit  210  performs the processing from Step S 703  to Step S 705  described in the first embodiment. On the other hand, if it is determined in Step S 1102  that the moving region is not included in the processing target block, the strobe light component calculating unit  210  advances the processing to Step S 1103 . 
     In Step S 1103 , the strobe light component calculating unit  210  calculates the strobe light component from the difference between the image data  202  at photographing without strobe light-emitting and the image data  205  at photographing with strobe light-emitting. Specifically, the strobe light component calculating unit  210  first calculates the strobe light component Ys[i] from a luminance value Ye[i] of each block of the image data  202  at photographing without strobe light-emitting and the luminance value Yt[i] of each block of the image data  205  at photographing with strobe light-emitting. A method of calculating the luminance value Ye[i] and the luminance value Yt[i] is as described in Step S 404  of  FIG. 4  in the first embodiment. Subsequently, the strobe light component calculating unit  210  calculates the strobe light component Ys[i] by subtracting the environmental light component (Ye[i]) from the sum (Yt[i]) of the strobe light component and the environmental light component according to the following Expression (11).
 
 Ys[i]=Yt[i]−Ye[i]   Expression (11)
 
     Upon completion of the calculation of the strobe light component Ys[i] in Step S 1103 , the strobe light component calculating unit  210  advances the processing to Step S 705 . Then, in Step S 705 , the strobe light component calculating unit  210  determines whether or not the processing on the total blocks has been completed. If it is determined in Step S 705  that the processing on the total blocks has been completed, the strobe light component calculating unit  210  ends the strobe light component calculation processing. On the other hand, if it is determined in Step S 705  that the processing on the total blocks has not been completed (an unprocessed block remains), the strobe light component calculating unit  210  returns the processing to Step S 1102 , and performs the above-mentioned processing. 
     As has been described above, in the fourth embodiment, strobe light component calculating methods are switched according to the detection result of the moving region. Hence, the calculation accuracy of the strobe light component of the background region for which the accuracy of the distance map is lower can be enhanced. Consequently, according to the fourth embodiment, even in the case of photographing with strobe light-emitting in the state where the object and the imaging apparatus are moving, a coloring discrepancy in a boundary portion of the object can be reduced, and appropriate coloring can be given to both the main object and the background. In this way, according to the fourth embodiment, the calculation accuracy of the strobe light component of a long-distance region, that is, the background region for which the accuracy of the distance map is lower can be enhanced, and more appropriate white balance correction is possible. 
     Note that, although the example in which the moving region is detected from the difference between the image data at photographing without strobe light-emitting and the image data at photographing with strobe light-emitting is described in the fourth embodiment, the present invention is not limited thereto. For example, the moving region may be detected from a difference between a distance map at photographing without strobe light-emitting and a distance map at photographing with strobe light-emitting. That is, if the difference between the distance map at photographing without strobe light-emitting and the distance map at photographing with strobe light-emitting is, for example, more than a predetermined value, it can be detected that the object has moved. 
     Hereinabove, exemplary embodiments of the present invention have been described. The present invention is not limited to these embodiments, and can be variously modified and changed within the range of the gist thereof. 
     Other Embodiments 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-018688, filed Feb. 2, 2015, which is hereby incorporated by reference herein in its entirety.