Patent Publication Number: US-9906676-B2

Title: Image processing apparatus and image processing method

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a technique of reproducing a translucent body. 
     Description of the Related Art 
     In the field of printing product packages, outdoor advertisements, and building materials, it is required to reproduce a translucent body. The appearance of the translucent body is determined by both transmissive light which is transmitted through the translucent body and reflective light which is reflected from the surface and inside of the translucent body. Accordingly, the reproduction of the translucent body requires color management considering both the transmissive light and the reflective light. 
     For example, there is a technique disclosed in Japanese Patent Laid-Open No. 2011-61723 as a technique of performing appropriate color management for a printed object observed under the influence of both a transmissive light source and a reflective light source. Japanese Patent Laid-Open No. 2011-61723 discloses the technique of obtaining spectral emission luminosity from a printed object in an observational environment in which the transmissive light source and the reflective light source coexist and calculating a colorimetric value in a desired observational environment based on the spectral emission luminosity. 
     In the case of performing color management by using the method disclosed in Japanese Patent Laid-Open No. 2011-61723, an observational environment for which color management is to be performed is designated, and based on the measurement values of a printed object in the observational environment, a printed object reproducing a desired color is formed. However, this printed object reproduces the desired color in the designated observational environment, and an appearance in another observational environment is not considered. Accordingly, there is a problem that whenever the observational environment changes, it is necessary to recalculate the measurement values to form the printed object again. 
     SUMMARY OF THE INVENTION 
     In an aspect of the present invention, there is provided an image processing apparatus comprising: a first obtaining unit configured to obtain first information including reflective characteristics of an object to be reproduced; a second obtaining unit configured to obtain second information including transmissive characteristics of the object to be reproduced; and a determining unit configured to determine an amount of coloring material for each pixel of an image representing the object to be reproduced based on the first information and the second information. 
     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 showing the physical configuration of an image processing apparatus according to Embodiment 1; 
         FIG. 2  is a block diagram showing the logical configuration of the image processing apparatus according to Embodiment 1; 
         FIG. 3  is a flowchart of processing performed by the image processing apparatus according to Embodiment 1; 
         FIG. 4  is a view showing a user interface displayed in a UI displaying unit according to Embodiment 1; 
         FIGS. 5A to 5D  are views showing examples of a method for obtaining image data including reflection and transmission as explained in embodiments; 
         FIG. 6  is a view showing a relationship between a reflective image and a transmissive image as explained in the embodiments; 
         FIG. 7  is a flowchart showing the operation of a feature amount determining unit according to Embodiment 1; 
         FIG. 8  is a flowchart showing the operation of a coloring material amount determining unit according to Embodiment 1; 
         FIGS. 9A and 9B  are views showing the inner structure of a data holding unit and a color conversion table according to Embodiment 1; 
         FIG. 10  is a view showing the structure of an image forming unit according to Embodiment 1; 
         FIG. 11  is a flowchart showing the operation of the image forming unit according to Embodiment 1; 
         FIG. 12  is a flowchart of processing performed by the image processing apparatus according to Embodiment 2; 
         FIG. 13  is a flowchart showing the operation of the feature amount determining unit according to Embodiment 2; 
         FIG. 14  is a flowchart of processing by a determining unit according to Embodiment 3; 
         FIG. 15  is a view showing an example of a color conversion LUT for calculating an ink amount from the CIELAB values of a reflective image and a transmissive image as explained in Embodiment 3; 
         FIG. 16  is a block diagram showing the logical configuration of an image processing apparatus according to Embodiment 4; 
         FIG. 17  is a view showing a user interface screen according to Embodiment 4; 
         FIG. 18  is a flowchart of processing performed by the image processing apparatus according to Embodiment 4; 
         FIGS. 19A and 19B  are schematic diagrams showing color gamut which can be reproduced by the image processing apparatus as explained in Embodiment 4; 
         FIG. 20  is a flowchart of processing for determining the amount of a coloring material according to Embodiment 4; 
         FIG. 21A  is a schematic diagram for explaining data in the data holding unit; and 
         FIG. 21B  is a schematic diagram for explaining a color conversion table. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described below in detail based on preferred embodiments with reference to the attached drawings. Incidentally, the features of the following embodiments are mere examples, and the present invention is not limited to the illustrated features. 
     Embodiment 1 
     In the present embodiment, explanation will be made on an example in which a reflective image is obtained by capturing an image of a translucent body to be reproduced with a reflective light source, and a transmissive image is obtained by capturing an image of the translucent body with a transmissive light source, and the translucent body is reproduced as a printed object based on the reflective image and the transmissive image. 
       FIG. 1  is a block diagram of an image processing apparatus according to the present embodiment. An image processing apparatus includes a CPU  101 , a main memory  102 , an HDD  103 , a general-purpose interface  104 , a monitor  105 , a main bus  106 , an instruction inputting unit  107  such as a keyboard or a mouse, and an image forming unit  108 . The general-purpose interface  104  connects the instruction inputting unit  107 , the image forming unit  108 , and the like to the main bus  106 . 
     A description will be given below of various processing operations which are realized by the CPU  101  executing various types of software (computer programs) stored in the HDD  103 . First, the CPU  101  starts an image processing application stored in the HDD  103  according to a user&#39;s instruction to the instruction inputting unit  107 . Then, the image processing application is expanded in the main memory  102 , and a user interface is displayed on the monitor  105 . Then, various types of data stored in the HDD  103  are transferred to the main memory  102  via the main bus  106  according to a command from the CPU  101 . The various types of data transferred to the main memory  102  are subjected to predetermined arithmetic processing according to the command from the CPU  101 , and the result of the arithmetic processing is displayed on the monitor  105  or stored in the HDD  103  via the main bus  106 . 
     Regarding the above configuration, explanation will be made on processing performed by the image processing application according to the command from the CPU  101 . 
       FIG. 2  is a diagram showing the logical configuration of the image processing apparatus  201  according to the present embodiment. The image processing apparatus  201  includes a UI displaying unit  202 , a first image data obtaining unit  203 , a second image data obtaining unit  204 , a determining unit  205 , a data holding unit  208 , and an image forming unit  209 . Further, the determining unit  205  includes a feature amount determining unit  206  and a coloring material amount determining unit  207 . Incidentally,  FIG. 2  shows a configuration example in which the image processing apparatus includes the image forming unit  209 , but the image processing apparatus may include the image forming unit outside of the image processing apparatus  201 . More specifically, the image processing apparatus  201  may be an apparatus which generates coloring material amount data for determining the amount of a coloring material used for the image forming unit. 
     The UI displaying unit  202  displays a user interface or the like on the monitor  105 . The first image data obtaining unit  203  obtains reflective image data designated by the user via the user interface displayed by the UI displaying unit  202 . The second image data obtaining unit  204  obtains transmissive image data designated by the user via the user interface displayed by the UI displaying unit  202 . The reflective image data and the transmissive image data are image data obtained by performing image-capturing on the same object (the same object to be reproduced) under different image-capturing conditions. Hereinafter, an image represented by the reflective image data is simply referred to as a reflective image, and an image represented by the transmissive image data is referred to as a transmissive image. The determining unit  205  determines the amount of the coloring material for reproducing the object to be reproduced based on the obtained reflective image data and transmissive image data. The determining unit  205  includes the feature amount determining unit  206  and the coloring material amount determining unit  207 , which perform the following processing to determine the amount of the coloring material. More specifically, the feature amount determining unit  206  determines a feature amount for reproducing characteristics appearing in the reflective image and the transmissive image based on the reflective image data and the transmissive image data. The coloring material amount determining unit  207  determines the amount of the coloring material based on the determined feature amount. 
     The data holding unit  208  holds a table and the like associating the characteristics of the coloring material, the feature amount, and the like. The image forming unit  209  forms an image based on the determined amount of the coloring material. 
     &lt;Operation of the Image Processing Apparatus  201 &gt; 
       FIG. 3  is a flowchart of processing performed by the image processing apparatus  201 . Processing shown in  FIG. 3  is realized by the image processing application functioning as each unit shown in  FIG. 2  according to the command from the CPU  101 . 
     In step S 301 , the UI displaying unit  202  displays, on the monitor  105 , the user interface for enabling the user to input information necessary for performing image processing.  FIG. 4  shows an example of the user interface. 
     In a designation input item  401 , the user designates the reflective image data representing the reflective image obtained by capturing an image of the translucent body to be reproduced with the reflective light source to input the reflective image data to the image processing apparatus  201 . In a designation input item  402 , the user designates the transmissive image data representing the transmissive image obtained by capturing an image of the translucent body to be reproduced with the transmissive light source to input the transmissive image data to the image processing apparatus  201 . An input image displaying unit  403  displays the reflective image data and the transmissive image data designated by the user in the designation input item  401  and the designation input item  402 . An output image displaying unit  404  displays a preview of a printed object reproducing the translucent body based on the input image data. A process button  405  is a button for giving an instruction to perform processing for calculating the amount of the coloring material in the printed object. An output button  406  is a button for performing processing for forming the printed object based on the calculated amount of the coloring material. In a case where the user performs input to each designation input unit, and gives an instruction to press the process button  405 , the process proceeds to step S 302 . 
     In step S 302 , the first image data obtaining unit  203  obtains reflective image data on the object to be reproduced as designated by the user via the user interface displayed in step S 301 . The reflective image data can be obtained by emitting light from an angle of 45 degrees with respect to a front side of the object to be reproduced, and capturing, with an image input device such as a digital camera, reflective light Rs travelling in a zero-degree direction with respect to a normal to the front side of the object to be reproduced as shown in  FIG. 5A , for example. The reflective light Rs includes surface reflective light reflected from the surface of the object to be reproduced and inner reflective light reflected from the inside of the object to be reproduced. At the time of image-capturing, it is necessary to be careful not to capture, together with the reflective light Rs, light transmitted through the object to be reproduced and reflected from another object. Incidentally, the geometrical condition explained in the present embodiment is an example, and it is needless to say that the reflective image data may be obtained under another geometrical condition. 
     In step S 303 , the second image data obtaining unit  204  obtains the transmissive image data on the object to be reproduced designated by the user via the user interface displayed in step S 301 . The transmissive image data can be obtained by emitting light from an angle of zero degrees with respect to a normal of a back side of the object to be reproduced and capturing, with the image input device such as the digital camera, transmissive light T travelling in a zero-degree direction with respect to a normal of the front side as shown in  FIG. 5B , for example. It is preferable that a positional relationship between the object to be reproduced and the digital camera be the same as the one at the time capturing the reflective image. Incidentally, the geometrical condition explained in the present embodiment is an example, and it is needless to say that the transmissive image data may be obtained under another geometrical condition. 
     In step S 304 , the feature amount determining unit  206  calculates a feature amount corresponding to both the reflective light and the transmissive light from the object to be reproduced based on the reflective image data obtained in step S 302  and the transmissive image data obtained in step S 303 .  FIG. 6  shows a relationship between the reflective image obtained in step S 302  and the transmissive image obtained in step S 303 . In  FIG. 6 , a star-shaped region is the object to be reproduced. In a case where the object to be reproduced has high transmissivity, most of light from the light source is transmitted through the object to be reproduced, and the reflective image obtained by above-described image-capturing method is a dark-color image. Further, the transmissive image is a light-color image. On the other hand, in a case where the object to be reproduced has low transmissivity, light from the light source is reflected or absorbed, and the transmissive image obtained by above-described image-capturing method is a dark-color image. Further, the reflective image can be a light-color image or a dark-color image depending on the reflective and absorption characteristics of the object. In view of the above, the feature amount determining unit  206  calculates the feature amount of the object to be reproduced by using the characteristics that the lightness of the reflective image and the transmissive image varies depending on the transmissivity of the object to be reproduced. Specific processing by the feature amount determining unit  206  will be described later. 
     In step S 305 , the coloring material amount determining unit  207  determines the amount of the coloring material in the printed object based on the feature amount determined in step S 304 . Specific processing by the coloring material amount determining unit  207  will be described later. 
     In step S 306 , the image forming unit  209  forms an image on a transparent print medium (for example, a film) based on the amount of the coloring material determined in step  305 , and ends the process. Specific processing by the image forming unit  209  will be described later. Incidentally, as described above, step S 306  may be performed by an apparatus other than the image processing apparatus  201 . 
     &lt;Operation of the Feature Amount Determining Unit  206  in Step S 304 &gt; 
       FIG. 7  is a flowchart of the processing performed by the feature amount determining unit  206  in step  304 . 
     In step S 701 , the feature amount determining unit  206  converts each pixel in the reflective image into CIELAB values. Subsequent processing will be described below by assuming that the reflective image and the transmissive image in the present embodiment are recorded in sRGB color space prescribed by the CIE (the International Commission on Illumination). Further, the reflective image and the transmissive image have the same resolution, and the pixel positions of the object to be reproduced in the reflective image correspond to those in the transmissive image. Naturally, in a case where the pixel positions of the object to be reproduced in the reflective image are not aligned to those in the transmissive image to some extent, the positions of the pixels may be adjusted by performing publicly-known rotational processing or the like. First, each pixel in the reflective image is converted into CIE tristimulus values X, Y, and Z by using the following formulas (1) and (2). 
     
       
         
           
             
               
                 
                   
                     R 
                     Linear 
                   
                   = 
                   
                     { 
                     
                       
                         
                           
                             
                               
                                 R 
                                 ⁢ 
                                 
                                   / 
                                 
                                 ⁢ 
                                 12.92 
                               
                             
                             
                               
                                 R 
                                 ≤ 
                                 0.04045 
                               
                             
                           
                           
                             
                               
                                 
                                   [ 
                                   
                                     
                                       ( 
                                       
                                         R 
                                         + 
                                         0.055 
                                       
                                       ) 
                                     
                                     ⁢ 
                                     
                                       / 
                                     
                                     ⁢ 
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                                   ] 
                                 
                                 2.4 
                               
                             
                             
                               
                                 R 
                                 &gt; 
                                 0.04045 
                               
                             
                           
                         
                         ⁢ 
                         
                           
 
                         
                         ⁢ 
                         
                           G 
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                         { 
                         
                           
                             
                               
                                 
                                   
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                                     ⁢ 
                                     
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                                     G 
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                                       [ 
                                       
                                         
                                           ( 
                                           
                                             G 
                                             + 
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                                           ) 
                                         
                                         ⁢ 
                                         
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                                       ] 
                                     
                                     2.4 
                                   
                                 
                                 
                                   
                                     G 
                                     &gt; 
                                     0.04045 
                                   
                                 
                               
                             
                             ⁢ 
                             
                               
 
                             
                             ⁢ 
                             
                               B 
                               Linear 
                             
                           
                           = 
                           
                             { 
                             
                               
                                 
                                   
                                     B 
                                     ⁢ 
                                     
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                                     B 
                                     ≤ 
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                                       ] 
                                     
                                     2.4 
                                   
                                 
                                 
                                   
                                     B 
                                     &gt; 
                                     0.04045 
                                   
                                 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
             
               
                 
                   
                     ( 
                     
                       
                         
                           X 
                         
                       
                       
                         
                           Y 
                         
                       
                       
                         
                           Z 
                         
                       
                     
                     ) 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             0.4124 
                           
                           
                             0.3576 
                           
                           
                             0.1805 
                           
                         
                         
                           
                             0.2126 
                           
                           
                             0.7152 
                           
                           
                             0.0722 
                           
                         
                         
                           
                             0.0193 
                           
                           
                             0.1192 
                           
                           
                             0.9505 
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           
                             
                               R 
                               Linear 
                             
                           
                         
                         
                           
                             
                               G 
                               Linear 
                             
                           
                         
                         
                           
                             
                               B 
                               Linear 
                             
                           
                         
                       
                       ) 
                     
                   
                 
               
               
                 
                   Formula 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
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     Then, the CIE tristimulus values X, Y, and Z are converted into CIELAB values by using the following formula (3). 
     
       
         
           
             
               
                 
                   
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                                   ( 
                                   
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                                       w 
                                     
                                   
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                                   1 
                                   ⁢ 
                                   
                                     / 
                                   
                                   ⁢ 
                                   3 
                                 
                               
                             
                             
                               
                                 X 
                                 &gt; 
                                 0.008856 
                               
                             
                           
                           
                             
                               
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                                 × 
                                 
                                   ( 
                                   
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                                     ⁢ 
                                     
                                       / 
                                     
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                                       w 
                                     
                                   
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                                 116 
                               
                             
                             
                               
                                 X 
                                 ≤ 
                                 0.008856 
                               
                             
                           
                         
                         ⁢ 
                         
                           
 
                         
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                                     Y 
                                     &gt; 
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                                     × 
                                     
                                       
                                         ( 
                                         
                                           Y 
                                           ⁢ 
                                           
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                                     Y 
                                     ≤ 
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                             ⁢ 
                             
                               
 
                             
                             ⁢ 
                             
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                           = 
                           
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                                           ⁢ 
                                           
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                                           3 
                                         
                                       
                                     
                                     
                                       
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                                         &gt; 
                                         0.008856 
                                       
                                     
                                   
                                   
                                     
                                       
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                                         × 
                                         
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                                             ⁢ 
                                             
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                                         116 
                                       
                                     
                                     
                                       
                                         Z 
                                         ≤ 
                                         0.008856 
                                       
                                     
                                   
                                 
                                 ⁢ 
                                 
                                   
 
                                 
                                 ⁢ 
                                 L 
                               
                               = 
                               
                                 
                                   
                                     116 
                                     × 
                                     
                                       f 
                                       y 
                                     
                                   
                                   - 
                                   
                                     16 
                                     ⁢ 
                                     
                                       
 
                                     
                                     ⁢ 
                                     a 
                                   
                                 
                                 = 
                                 
                                   
                                     500 
                                     × 
                                     
                                       ( 
                                       
                                         
                                           f 
                                           x 
                                         
                                         - 
                                         
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                                           y 
                                         
                                       
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                                     ⁢ 
                                     
                                       
 
                                     
                                     ⁢ 
                                     b 
                                   
                                   = 
                                   
                                     500 
                                     × 
                                     
                                       ( 
                                       
                                         
                                           f 
                                           y 
                                         
                                         - 
                                         
                                           f 
                                           z 
                                         
                                       
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                   Formula 
                   ⁢ 
                   
                       
                   
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                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
     where X, Y, and Z are tristimulus values in a XYZ color space, 
     Xw, Yw, and Zw are the tristimulus values of a white point, and 
     in D65, Xw=95.05, Yw=100.0, and Zw=108.91. 
     This processing is performed on all the pixels of the reflective image. As a result, each pixel in the reflective image is converted into the CIELAB values. 
     In step S 702 , the feature amount determining unit  206  converts each pixel in the transmissive image into the CIELAB values. A converting method is the same as the one in step S 701 , and explanation thereof will be omitted. 
     In step S 703 , the feature amount determining unit  206  calculates the feature amount of each pixel in the object to be reproduced. The feature amount in the present embodiment does not represent only either one of the transmissive characteristics and the reflective characteristics, but represents a ratio between the reflective light and the transmissive light. Here, the feature amount S in the present embodiment is defined as a ratio between the lightness of the transmissive image and the lightness of the reflective image, and more specifically, the feature amount S is calculated by using the following formula (4).
 
 S=L   R /( L   R   +L   T )  Formula (4)
 
     where L R  is an L value in CIELAB color space for the reflective image, and L T  is an L value in CIELAB color space for the transmissive image. 
     In step S 704 , the feature amount determining unit  206  stores, in the main memory  102 , the feature amount of each pixel in the object to be reproduced calculated in step S 703  together with the CIELAB values of the pixel, and ends the process. 
     &lt;Operation of the Coloring Material Amount Determining Unit  207  in Step  305 &gt; 
       FIG. 8  is a flowchart of the processing performed by the coloring material amount determining unit  207  in step S 305 . 
     In step S 801 , the coloring material amount determining unit  207  obtains the CIELAB values of each pixel in an image and the feature amount of each pixel in the image as calculated in step S 304 . The obtained CIELAB values may be those of the reflective image or those of the transmissive image, but in the present embodiment, the CIELAB values of the reflective image are obtained. 
     In step S 802 , the coloring material amount determining unit  207  obtains the characteristics of the coloring material from the data holding unit  208 .  FIGS. 9A and 9B  show an example of the characteristics of the coloring material stored in the data holding unit  208 . As shown in  FIG. 9A , the data holding unit  208  holds a correspondence table in which the amount of a white ink is associated with the feature amount and a color conversion table for each amount of the white ink. The white ink is an ink used for the image forming unit  209  to form the printed object, and functions as a scatterer, thereby controlling the ratio between the reflective light and the transmissive light from the printed object. As stated above, in the present embodiment, the image of the object to be reproduced is formed on the transparent print medium (for example, the film). On this occasion, as the amount of the white ink is increased, the reflective light increases, and the reflectivity of the printed object increases. Further, as more light is reflected from or absorbed by the white ink, the transmissive light decreases, and the transmissivity of the printed object decreases. Conversely, as the amount of the white ink is decreased, the reflectivity of the printed object decreases, and the transmissivity increases. The data holding unit  208  holds a correspondence table showing the amount of the white ink corresponding to the characteristics (that is, the feature amount) of such a translucent body. Incidentally, the correspondence table held by the data holding unit  208  is created by previously changing the amount of the white ink, forming the printed object by the image forming unit  209 , and making measurements. 
     Further, the image forming unit  209  equips color inks for controlling color as well as the white ink for controlling the ratio between the reflective light and the transmissive light emitted from the object to be reproduced. In the present embodiment, the color inks are four color inks, that is, C (cyan), M (magenta), Y (yellow), and K (black) inks. Further, for simple explanation, the scattering characteristics of these inks are sufficiently smaller than those of the white ink, and the ratio between the reflective light and the transmissive light is not affected. There is created in advance, for each amount of the white ink, a color conversion table specifying a relationship between a combination of the amounts of the color inks corresponding to the characteristics of the image forming unit  209  and the CIELAB values, and the data storing unit  208  stores the color conversion table therein. The reason why the color conversion table is prepared for each amount of the white ink is that the combination of the color inks representing the predetermined CIELAB values varies according to the amount of the white ink. The color conversion table held by the data holding unit  208  is a table showing a relationship between each lattice point and the amounts of the C, M, Y, and K inks reproducing the lattice point. This lattice point is a lattice point produced by dividing the ranges of the CIELAB values (for example, 0≦L*100, −128≦a*, b*≦127) into 17 slices for each axis. This table is created in advance for each amount of the white ink. On this occasion, in a case where the CIELAB values of the lattice point are outside the color gamut which can be reproduced by the image forming unit  209 , processing to set the CIELAB values of the lattice point within the color gamut is appropriately performed by performing color gamut compression (gamut mapping). Either of the reflective image and the transmissive image may presumed to set the CIELAB values, but these CIELAB values need to correspond to the CIELAB values obtained in step S 801 . In the present embodiment, explanation will be made on an example of holding a color conversion table specifying a relationship between the CIELAB values of the reflective image and the amounts of the color inks as shown in  FIG. 9B . Incidentally, any method may be used as a method for creating the color conversion table. Since there are many known methods, their explanation will be omitted in the present embodiment. In step S 802 , as the characteristics of the coloring material, there are obtained two types of tables, that is, the correspondence table in which the amount of the white ink is associated with the feature amount and the color conversion table. 
     In step S 803 , the coloring material amount determining unit  207  determines the amount of the white ink realizing the feature amount of each pixel by referring to the correspondence table obtained in step S 802 . 
     In step S 804 , the coloring material amount determining unit  207  calculates the amounts of the color inks for reproducing the reflective CIELAB values of each pixel by referring to the color conversion table corresponding to the amount of the white ink for each pixel as determined in step S 803 . The amounts of the color inks may be calculated by performing interpolation calculation based on the color conversion table. It is possible to use, as an interpolation method, an already-known method such as tetrahedral interpolation or cubic interpolation. 
     In step S 805 , the calculated amount of the white ink and the calculated amounts of the color inks for each pixel are stored in a memory, and the process ends. 
     Incidentally, in the present embodiment, the correspondence table is used to calculate the amount of the white ink from the feature amount. However, the amount of the white ink can be calculated by using an approximation formula to obtain a relationship between the amount of the white ink and the feature amount. For example, the following formula (5) can be used as a formula for calculating the amount of the white ink W from the feature amount S.
 
 W=kS   n   Formula (5)
 
     where k and n are constants, and appropriate values may be stored as k and n beforehand. 
     &lt;Operation of the Image Forming Unit  209  in Step S 306 &gt; 
       FIG. 10  is a view showing the structure of the image forming unit  209 . A head cartridge  1001  includes a print head having a plurality of ejection openings and an ink tank for supplying an ink to the print head, and is provided with a connector for receiving a signal or the like for driving each ejection opening of the print head. The ink tank is independently provided with a total of five types of color inks, that is, the white ink and the C (cyan), M (magenta), Y (yellow), and K (black) inks for controlling the feature amount. The head cartridge  1001  is positioned and exchangeably mounted in a carriage  1002 , and the carriage  1002  is provided with a connector holder for transmitting a drive signal or the like to the head cartridge  1001  via the connector. The carriage  1002  can reciprocate along a guide shaft  1003 . More specifically, the carriage  1002  is driven by a main scan motor  1004  as a driving source via a driving mechanism such as a motor pulley  1005 , a driven pulley  1006 , and a timing belt  1007 , and the position and movement of the carriage  1002  are controlled. Incidentally, the movement of the carriage  1002  along the guide shaft  1003  is referred to as a “main scan,” and the moving direction is referred to as a “main scan direction.” A print medium  1008  such as a transmissive film for printing is placed on an automatic sheet feeder (hereinafter referred to as the “ASF”)  1010 . At the time of forming an image, a paper feed motor  1011  is driven to rotate a pickup roller  1012  via a gear, and the print medium  1008  is separated and fed from the ASF  1010  one by one. Further, the print medium  1008  is conveyed to a print start position facing an ejection-opening surface of the head cartridge  1001  on the carriage  1002  by rotation of a conveying roller  1009 . The conveying roller  1009  is driven by a line field (LF) motor  1013  as a driving source via a gear. Whether the print medium  1008  is fed or not and a position at the time of feeding are determined at the time of the passage of the print medium  1008  through a paper end sensor  1014 . The head cartridge  1001  mounted on the carriage  1002  is held so that the ejection-opening surface protrudes downward from the carriage  1002  and is parallel to the print medium  1008 . A controlling unit  1020  controls the operation of each part of the image forming unit  209  based on the amount of the white ink and the amounts of the color inks for each pixel as calculated in step S 305 . For ease of explanation, a description will be given by assuming that in the present embodiment, the image forming unit  209  is a binary printer which controls whether or not to eject an ink at a predetermined resolution. Naturally, it is possible to use a system capable of adjusting the size of an ink droplet to be ejected. 
     Explanation will be made on the operation of forming an image. First, in a case where the print medium  1008  is conveyed to the predetermined print start position, the carriage  1002  moves along the guide shaft  1003  above the print medium  1008 , and during the movement of the carriage  1002 , the ink is ejected from the ejection openings of the print head. In a case where the carriage  1002  is moved to one end of the guide shaft  1003 , the conveying roller  1009  conveys the print medium  1008  by a predetermined distance in a direction perpendicular to the scan direction of the carriage  1002 . This conveying of the print medium  1008  is referred to as the “paper feed” or the “sub-scan,” and this conveying direction is referred to as the “paper feed direction” or the “sub-scan direction.” In a case where the print medium  1008  has been conveyed by the predetermined distance, the carriage  1002  moves again along the guide shaft  1003 . In this manner, an image is formed on the entire print medium  1008  by repeating the scan and the feed by the carriage  1002  for the print head. 
     Incidentally, the print medium used in the present embodiment may be a transparent body or a translucent body, preferably has high transmissivity, and may be used to form an image by the print head. It is possible to use various materials such as polyvinyl chloride, acryl, and PET. Further, it is conceivable to use a mode in which a plurality of color conversion tables to be used for step S 305  are held, and a suitable color conversion table is used according to the print medium, or the like. Further, in the present embodiment, an example of an inkjet system as the image forming unit is presented, but another printing system may be used. 
       FIG. 11  is a flowchart of the processing performed by the image forming unit  209  in step S 306 . 
     In step S 1101 , the image forming unit  209  quantizes the multivalued amount of the white ink for each pixel as calculated in step S 305  into binary data based on which the image forming unit  209  can form an image. A quantizing method may be a general method such as a dither matrix method or an error diffusion method. The cycle (distribution) of the white ink can be adjusted by performing such an area gradation method to perform quantization. Incidentally, explanation has been made based on the premise that the resolution of the input image is equal to that of the image forming unit, but in a case where the resolution of the input image is different from that of the image forming unit, resolution conversion processing may be performed. 
     In step S 1102 , the image forming unit  209  uses and ejects the white ink to form the image based on the binary data obtained by the quantization in step S 1101 . In step S 1103 , the image forming unit  209  quantizes the multivalued amounts of the color inks for each pixel as calculated in step S 305  into binary data for each ink color. In step S 1104 , the image forming unit  209  uses and ejects the color inks to form the image based on the binary data obtained by the quantization in step S 1103 . The above processing in steps S 1101  to S 1104  is repeatedly performed for each paper feed operation until the entire image has been formed. 
     As explained above, in the present embodiment, the feature amounts represented in the reflective image and the transmissive image of the translucent body are determined based on the reflective image and the transmissive image of the translucent body. Further, explanation has been made on the example in which the image is formed by using the amount of the white ink and the amounts of the color inks which are calculated based on the feature amounts. More specifically, explanation has been made on the example in which the ratio between the reflective light and the transmissive light emitted from the object to be reproduced is controlled. This makes it possible to form the printed object having the feature amount equivalent to that of the translucent body, and accordingly, it is possible to obtain the printed object which reproduces the appearance of the translucent body in any observational environment. 
     Embodiment 2 
     In Embodiment 1, explanation has been made on the example in which the reflective image is input as information indicative of the reflective characteristics of the object to be reproduced, and the transmissive image is input as information indicative of the transmissive characteristics. In the present embodiment, explanation will be made on an example in which a black backing image and a white backing image are input as information indicative of the reflective characteristics and information indicative of the transmissive characteristics, respectively. Incidentally, the configuration of Embodiment 2 may be identical to that of Embodiment 1. Differences from Embodiment 1 lie in the details of the processing by the first image data obtaining unit  203 , the second image data obtaining unit  204 , and the feature amount determining unit  206 . Accordingly, this processing will be described below, and explanation on the other processing operations will be omitted. 
       FIG. 12  is a flowchart of processing performed by the image processing apparatus  201  according to Embodiment 2. The flowchart of  FIG. 12  is obtained by changing steps S 302 , S 303 , and S 304  in the flowchart of  FIG. 3  to steps S 1202 , S 1203 , and S 1204 , respectively. Explanation will be made on steps S 1202 , S 1203 , and S 1204 , which constitute the differences from Example 1. 
     In step S 1202 , the first image data obtaining unit  203  obtains black backing image data produced by capturing an image of the object to be reproduced on a black backing. As shown in  FIG. 5C , for example, a black member having negligibly small reflectivity is placed under the object to be reproduced, and as in Embodiment 1, light is emitted from a 45-degree direction with respect to the normal to the front side. Then, the image-capturing device such as the digital camera is provided in a zero-degree direction with respect to the normal to the front side to capture an image. In this case, since light transmitted through the object to be reproduced is absorbed by the black backing, the black backing image can be handled as the reflective image in which only the reflective light Rs is captured as in Embodiment 1. In step S 1202 , this black backing image is obtained. 
     In step S 1203 , the second image data obtaining unit  204  obtains white backing image data produced by capturing an image of the object to be reproduced on a white backing. As shown in  FIG. 5D , for example, a white member having reflectivity of about 100% is placed under the object to be reproduced, and light is emitted from a 45-degree direction with respect to the normal to the front side. Then, the image-capturing device such as the digital camera is provided in a zero-degree direction with respect to the normal to the front side to capture an image. In this case, the captured light includes not only the reflective light Rs, but also light T 2  transmitted through the object to be reproduced twice. This is because the transmissive light T transmitted through the object to be reproduced is reflected from the white backing, is transmitted through the object to be reproduced again, and is emitted from the object to be reproduced. In step S 1203 , the second image data obtaining unit  204  obtains the white backing image produced by capturing the light Rs+T 2 . 
     In step S 1204 , the feature amount determining unit  206  calculates the feature amount based on the black backing image and the white backing image obtained in steps S 1202  and S 1203 . Explanation will be made below on the specific processing by the feature amount determining unit  206 . 
       FIG. 13  shows a flowchart of the processing by the feature amount determining unit  206  according to the present embodiment. 
     In step S 1301 , the feature amount determining unit  206  converts each pixel in the black backing image obtained in step S 1202  into CIE tristimulus values X, Y, and Z. In the conversion, the above-described formulas (1) and (2) are used. 
     In step S 1302 , the feature amount determining unit  206  converts each pixel in the white backing image obtained in step S 1203  into CIE tristimulus values X, Y, and Z. In the conversion, the above-described formulas (1) and (2) are used. 
     In step S 1303 , the feature amount determining unit  206  calculates CIE tristimulus values X, Y, and Z for each pixel in an image corresponding to the transmissive image. As described above, the black backing image is an image obtained by capturing the reflective light Rs, and the white backing image is an image obtained by capturing the light Rs+T 2 , which is a mixture of the reflective light Rs and the transmissive light T. Accordingly, in a case where Ik is the CIE tristimulus values X, Y, and Z for the black backing image, Iw is the CIE tristimulus values X, Y, and Z for the white backing image, and It is the CIE tristimulus values X, Y, and Z for the image corresponding to the transmissive image, It can be calculated according to the following formula (6).
 
 It=√{square root over (Iw−Ik)}   Formula (6)
 
     In this manner, in step S 1303 , the value of each pixel in the black backing image and the value of each pixel in the white backing image are used to calculate the CIE tristimulus values X, Y, and Z for each pixel in the image corresponding to the transmissive image. 
     In step S 1304 , the feature amount determining unit  206  converts the CIE tristimulus values X, Y, and Z for each pixel in the black backing image (that is, the reflective image) into CIELAB values. In the conversion, the above-described formula (3) is used. 
     In step S 1305 , the feature amount determining unit  206  converts the CIE tristimulus values X, Y, and Z for each pixel in the image corresponding to the transmissive image as calculated in step S 1303  into CIELAB values. In the conversion, the above-described formula (3) is used. 
     In step S 1306 , the feature amount determining unit  206  calculates the feature amount of each pixel. In the calculation, the above-described formula (4) is used. Incidentally, the calculation is performed by regarding the CIELAB values for the black backing image as the CIELAB values of the reflective image. In step S 1307 , the feature amount determining unit  206  stores, in a memory, the feature amount of each pixel calculated in step S 1306  together with the CIELAB values of the pixel, and ends the process. 
     In the above description, explanation has been made on the example in which in the present embodiment, the feature amount indicative of the ratio between the reflective light and the transmissive light emitted from the object to be reproduced is determined based on the image obtained by performing image-capturing on the translucent body with the black backing and the image obtained by performing image-capturing on the translucent body with the white backing. Accordingly, it is possible to form the printed object having the feature amount equivalent to that of the translucent body based on the plurality of reflective images obtained by changing the backing without requiring the transmissive image as in Embodiment 1. 
     Embodiment 3 
     In Embodiment 1, explanation has been made on the feature that the feature amount indicative of the ratio between the reflective light and the transmissive light emitted from the object to be reproduced is determined based on the reflective image and the transmissive image, and the amount of the coloring material is determined based on the feature amount. In the present embodiment, explanation will be made on the feature of directly determining the amount of the coloring material based on the reflective image and the transmissive image. 
     An image processing apparatus of Embodiment 3 is identical to that of Embodiment 1 except that the feature of the determining unit  205  in  FIG. 2  is different between Embodiment 1 and Embodiment 3. More specifically, the determining unit  205  does not include the feature amount determining unit  206  and the coloring material amount determining unit  207 . A flowchart of processing performed by the image processing apparatus  201  according to Embodiment 3 is identical to the flowchart according to Embodiment 1 except the following point. More specifically, the flowchart according to Embodiment 3 is identical to the flowchart according to Embodiment 1 except that in  FIG. 3 , processing in steps S 304  and S 305  is deleted, and processing for calculating the amount of the coloring material based on the reflective image data and the transmissive image data is inserted instead. 
     With reference to  FIG. 14 , explanation will be made below on processing performed by the determining unit  205  to calculate the amount of the coloring material based on the reflective image data and the transmissive image data according to Embodiment 3. 
     In step S 1401 , the determining unit  205  converts each pixel of the reflective image into CIELAB values. In the conversion, the formulas (1), (2), and (3) are used. In step S 1402 , the determining unit  205  converts each pixel of the transmissive image into CIELAB values. In the conversion, the formulas (1), (2), and (3) are used. 
     In step S 1403 , the determining unit  205  calculates the amount of the white ink and the amounts of the color inks based on the CIELAB values for the reflective image and the CIELAB values for the transmissive image. In Embodiment 1, the feature amount is firstly calculated from the CIELAB values for the reflective image and the CIELAB values for the transmissive image, and then, the amounts of the inks are successively calculated. In the present embodiment, the amount of each ink is directly determined. In the present embodiment, the data holding unit  208  holds a color conversion LUT shown in  FIG. 15 . This color conversion LUT is a LUT indicative of a correspondence relationship between the CIELAB values for the reflective image and the transmissive image and the amounts of the inks (W, C, M, Y, and K) for reproducing these CIELAB values, and is a six-dimensional input/five-dimensional output LUT. The color conversion LUT may be prepared beforehand based on the result of changing the amounts of the inks stepwise, outputting the printed object by the image forming unit  209 , and making measurements and may be stored in the data holding unit  208 . In step S 1403 , the determining unit  205  performs interpolation calculation with the color conversion LUT, thereby calculating the amount of the white ink and the amounts of the color inks which realize the CIELAB values for the reflective image and the transmissive image. Incidentally, since an existing method may be used for the interpolation calculation, explanation thereof will be omitted. 
     In step S 1404 , the determining unit  205  stores, in the memory, the amount of the white ink and the amounts of the color inks for each pixel as calculated in step S 1403  together with the CIELAB values for the pixel, and ends the process. 
     As described above, in Embodiment 3, the data holding unit  208  is configured to hold, as the color conversion LUT, a correspondence relationship between the CIELAB values for the reflective image and the transmissive image of the translucent body and the amount of the white ink and the amounts of the color inks for reproducing the CIELAB values. This makes it possible to directly calculate the amount of the inks necessary for reproducing the translucent body based on the CIELAB values for the reflective image and the transmissive image of the translucent body. 
     &lt;Variations&gt; 
     In the above embodiments, descriptions have been given of the examples in which the calculated amount of the white ink is binarized, and printing is performed by using area gradation. In addition to these examples, it is also possible to perform a method for controlling the amount of the white ink for each pixel to control a thickness or form a printed object having a distribution of the ratio between the reflective light and the transmissive light in an image by using a plurality of white inks having different scattering characteristics. 
     Further, in the embodiments, the feature amount is defined by using the lightness of each image as in the formula (4). However, the feature amount is not limited to this. For example, the feature amount may be defined as follows:
 
 S=L   R   /L   T   Formula (7)
 
     As in the following formulas (8) and (9), the numerator may be the lightness of the transmissive image.
 
 S=L   T /( L   R   +L   T )  Formula (8)
 
 S=L   T   /L   R   Formula (9)
 
     Further, it is also possible to use not the ratio of lightness, but a ratio of the luminance, spectral energy, or the like of the reflective light and the transmissive light. Furthermore, it is possible to define, not the lightness, but a difference between the reflective light and the transmissive light as a feature amount. In this case, a table of correspondence between the feature amount and the white ink may be created according to the definition of the feature amount, and held in the data holding unit  208 . 
     Further, in Embodiment 1, there is shown the example in which the reflective image and the transmissive image are input and in Embodiment 2, there is shown the example in which the black backing image and the white backing image are input. However, the input information is not limited to these. For example, in a case where two or more items such as an image obtained by performing image-capturing under any condition and a ratio of the illumination of the reflective light source and the transmissive light source at the time of capturing the image are input for one object to be reproduced, it is possible to calculate the feature amount. Further, color information equivalent to a hue, chroma, and the like is included in two types of images to be input such as both the reflective image and the transmissive image in Embodiment 1, but it is also possible to use a method in which only information on lightness is included in either one of the reflective image and the transmissive image. 
     Further, in the embodiments, an RGB image is input as information including reflection and transmission, but the input information is not limited to the RGB image. For example, it is also possible to use a CMYK image, and further, it is also possible to use information such as a distribution of a feature amount created by using computer graphics (CG). As the feature amount, it is possible to use the feature amount indicative of the ratio between the reflective light and the transmissive light as described in the examples, and it is also possible to use reflectivity and transmissivity which can be converted into the ratio between the reflective light and the transmissive light, and hiding power and haze which conform to the JIS. Further, it is also possible to use a combination of the above items. 
     Further, in the embodiments, explanation has been made by taking CIELAB color space as an example of color space used for color conversion, but the color space is not limited to the CIELAB color space. For example, it is possible to use other color space such as CIE tristimulus values X, Y, and Z or CIELUV. Further, it is needless to say that it is possible to use color perception space for a color appearance model such as CIECAM97, CIECAM97s, or CIECAM02. 
     Further, in the embodiments, explanation has been made that at least two types of coloring materials are used, and that at least one of the coloring materials includes an achromatic ink having relatively stronger scattering than the other coloring material(s). More specifically, explanation has been made on the example in which the C, M, Y, and K inks and the white ink are used. Further, explanation has been made on the example in which the white ink is used as an ink for controlling the ratio between the reflective light and the transmissive light, but it is also possible to use another ink such as a silver ink. 
     Further, in the embodiments, for simple explanation, description has been given based on the premise that the scattering characteristics of the color inks are sufficiently small as compared with those of the white ink and do not affect the ratio between the reflective light and the transmissive light. However, it is possible to use color inks which affect the ratio between the reflective light and the transmissive light. In this case, in order to determine the amounts of the inks for obtaining the desired feature amount and color reproduction, it is possible to use a method for previously measuring the feature amount in a case where the white ink and the color inks are mixed, and converting the feature amount into the color conversion LUT. 
     Further, in the embodiments, explanation has been made that the color inks included in the image forming unit  209  are C, M, Y, and K. For example, it is possible to use the color inks such as R (red), G (green), and B (blue) color inks. Further, it is needless to say that it is possible to use any color inks as light-color inks such as lc (light cyan) and lm (light magenta) color inks. Further, it is naturally possible to use a method for forming an image by previously preparing a plurality of inks according to the calculated feature amount without individually controlling ejection of the above-described multiple color inks. 
     Further, in the embodiments, description has been mainly made of a method for forming the printed object. However, for example, it is also possible to use a method using, as a display for controlling the appearances of both the transmissive light source and the reflective light source, a filter in which elements capable of controlling the ratio between the reflective light and the transmissive light are arranged in place of the white ink. 
     Embodiment 4 
     In Embodiment 4, explanation will be made on processing in a case where the color gamut of the reflective image or the color gamut of the transmissive image goes beyond the scope of color reproduction of the image processing apparatus. 
     In the present embodiment, the white ink is a coloring material used for controlling the scattering characteristics (light scattering intensity) of the printed object as in Embodiments 1 to 3. As the amount of the white ink becomes larger, the scattering intensity of the printed object becomes higher, and the reflectivity of the printed object becomes higher. On the other hand, as the amount of the white ink becomes smaller, the scattering intensity of the printed object becomes lower, and the transmissivity of the printed object becomes higher. Further, in the present embodiment, the effects of the color inks of four colors C, M, Y, and K on the scattering characteristics of the printed object are extremely small as compared with those of the white ink as in Embodiments 1 to 3, and can be ignored. 
       FIG. 16  is a block diagram showing the logical configuration of an image processing apparatus  1600  according to the present embodiment. As shown in  FIG. 16 , the image processing apparatus  1600  includes a reflective image obtaining unit  1601 , a transmissive image obtaining unit  1602 , a priority level obtaining unit  1603 , a scattering characteristics deriving unit  1604 , a coloring material amount determining unit  1605 , a preview screen creating unit  1606 , and a data holding unit  1607 . 
     The reflective image obtaining unit  1601  obtains reflective image data selected by the user, and sends the obtained reflective image data to the coloring material amount determining unit  1605 . The reflective image data is the reflective image data obtained by the method explained in Embodiments 1 to 3. 
     The transmissive image obtaining unit  1602  obtains transmissive image data selected by the user, and sends the obtained transmissive image data to the coloring material amount determining unit  1605 . The transmissive image data is the transmissive image data obtained by the method explained in Embodiments 1 to 3. 
     The priority level obtaining unit  1603  obtains a priority level designated by the user, and sends the obtained priority level to the scattering characteristics deriving unit  1604 . The priority level is a parameter for adjusting a degree to which the reflective characteristics of the translucent body and the transmissive characteristics of the translucent body contribute to reproduction of an appearance. 
     The scattering characteristics deriving unit  1604  derives scattering characteristics necessary for reproducing the appearance of the translucent body based on the priority level sent by the priority level obtaining unit  1603  (the details will be described later), and sends the derived scattering characteristics to the coloring material amount determining unit  1605 . 
     The coloring material amount determining unit  1605  determines the amount of the coloring material based on either of the reflective image data and the transmissive image data and the scattering characteristics (the details will be described later). Print data sent to an image forming unit  1610  by the image processing apparatus  1600  includes data on the amount of the coloring material (hereinafter referred to as the coloring material amount data), and the image forming unit  1610  forms an image on a print medium based on the coloring material amount data. Further, in a case where the user desires a preview display, the coloring material amount determining unit  1605  sends the coloring material amount data to the preview screen creating unit  1606 . 
     The preview screen creating unit  1606  creates a preview screen based on the coloring material amount data sent by the coloring material amount determining unit  1605 . This preview screen is an image for showing how the resultant printed object will appear with the reflective light source or the transmissive light source in a case where printing is performed at a present setting. The created preview screen is displayed on the monitor and presented to the user (see  FIG. 17 ). 
     The data holding unit  1607  holds data such as a lookup table (LUT) used in a case where the coloring material amount determining unit  1605  determines the amount of the coloring material or in a case where the preview screen creating unit  1606  creates the preview screen (the details will be described later). 
     &lt;User Interface Screen&gt; 
       FIG. 17  is a view showing an example of a UI screen displayed on the monitor after the image processing application is started. Via this UI screen, the user inputs information necessary for printing. 
     The UI screen shown in  FIG. 17  includes a reflective image input area  1701 , a transmissive image input area  1702 , a priority level input area  1703 , an input image display area  1704 , and an output image (preview) display area  1705 . Except for the priority level input area  1703 , the above areas are basically the same as the ones shown in  FIG. 4 . 
     In the present embodiment, the user designates the priority level by moving a slide bar in the priority level input area  1703 . As shown in  FIG. 17 , in the present embodiment, the priority level takes any integral value in the range of 1 to 10, and as the appearance in the case of using the reflective light source is more prioritized over the appearance in the case of using the transmissive light source, the priority level becomes lower. Incidentally, the priority level explained in the present embodiment is just an example, and the priority level may be values expressed in smaller units, larger units, or percentage, 
     In the output image (preview) display area  1705 , there are displayed an image for showing how the printed object will look with the reflective light source in a case where printing is performed at a present setting and an image for showing how the printed object will look with the transmissive light source in a case where printing is performed at the present setting. On this occasion, compression is performed as necessary so that the color gamut of an image to be displayed in the output image (preview) display area  1705  is within the color gamut which can be reproduced by the image processing apparatus. Accordingly, before printing, the user can check whether or not the desired result (printed object) can be obtained by viewing the display in the area. 
     A convert button  1706  is a button used in a case where the user desires the preview display. After inputting data to the reflective image input area  1701 , the transmissive image input area  1702 , and the priority level input area  1703 , pressing the convert button  1706  triggers execution of processing in the present embodiment. The details of this processing will be described later with reference to  FIG. 18 . 
     An output button  1707  is a button used in a case where the user gives an instruction to perform printing and output. In a case where the output button  1707  is pressed, the image forming apparatus starts printing processing. 
     &lt;Processing Performed by the Image Processing Apparatus&gt; 
       FIG. 18  is a flowchart of processing performed by the image processing apparatus  1600  according to the present embodiment. As stated above, after the reflective image and the transmissive image are selected via the UI screen, and the priority level is designated, pressing the convert button  1706  by the user triggers execution of the processing according to the present embodiment. 
     In step S 1801 , the CPU determines whether or not the convert button  1706  is pressed after the user&#39;s input. As a result of the determination, in a case where the convert button  1706  is pressed, the process proceeds to step S 1802 . On the other hand, in a case where the convert button  1706  is not pressed, a standby state is maintained until the convert button  1706  is pressed. 
     In step S 1802 , the reflective image obtaining unit  1601  obtains the reflective image data selected by the user, and sends the obtained reflective image data to the coloring material amount determining unit  1605 . 
     In step S 1803 , the transmissive image obtaining unit  1602  obtains the transmissive image data selected by the user, and sends the obtained transmissive image data to the coloring material amount determining unit  1605 . 
     In step S 1804 , the priority level obtaining unit  1603  obtains the priority level (hereinafter denoted as P) designated by the user, and sends the obtained priority level to the scattering characteristics deriving unit  1604 . 
     In step S 1805 , the scattering characteristics deriving unit  1604  derives scattering characteristics (hereinafter denoted as S) based on the priority level P, and sends the derived scattering characteristics to the coloring material amount determining unit  1605 . 
     In order to explain a method for deriving the scattering characteristics S,  FIGS. 19A and 19B  show color gamut which can be reproduced by the image processing apparatus  1600 .  FIG. 19A  is a diagram showing color gamut which can be reproduced by the image processing apparatus  1600  for the printed object observed with the reflective light source. Color gamut  1901  shown by a solid line in  FIG. 19A  is color gamut which can be reproduced in a case where printing is performed under a condition in which the content of the scatterer (the white ink) is large, and color gamut  1902  shown by a broken line is color gamut which can be reproduced in a case where printing is performed under a condition in which the content of the scatterer is small. In a case where printing is performed under a condition in which the content of the scatterer is large as indicated by the color gamut  1901 , the color gamut is wide, and in a case where printing is performed under a condition in which the content of the scatterer is small as indicated by the color gamut  1902 , the color gamut is narrow. 
       FIG. 19B  is a diagram showing color gamut which can be reproduced by the image processing apparatus  1600  for the printed object observed with the transmissive light source. Color gamut  1903  shown by a solid line in  FIG. 19B  is color gamut which can be reproduced in a case where printing is performed under a condition in which the content of the scatterer is large, and color gamut  1904  shown by a broken line is color gamut which can be reproduced in a case where printing is performed under a condition in which the content of the scatterer is small. In a case where printing is performed under a condition in which the content of the scatterer is large as indicated by the color gamut  1903 , the color gamut is narrow, and in a case where printing is performed under a condition in which the content of the scatterer is small as indicated by the color gamut  1904 , the color gamut is wide. 
     As disclosed in  FIGS. 19A and 19B , there exists a tradeoff relationship between the color gamut which can be reproduced by the image processing apparatus  1600  with the reflective light source and the color gamut which can be reproduced by the image processing apparatus  1600  with the transmissive light source. More specifically, in a case where printing is performed under a condition in which the content of the scatterer is large, the color gamut which can be reproduced with the reflective light source is wide, but the color gamut which can be reproduced with the transmissive light source is narrow. On the other hand, in a case where printing is performed under a condition in which the content of the scatterer is small, the color gamut which can be reproduced with the reflective light source is narrow, and the color gamut which can be reproduced with the transmissive light source is wide. 
     Accordingly, in the present embodiment, in a case where the reproducibility of the appearance in the case of using the reflective light source is prioritized, printing is performed under a condition in which the content of the white ink, which is the scatterer, is large, and in a case where the reproducibility of the appearance in the case of using the transmissive light source is prioritized, printing is performed under a condition in which the content of the white ink, which is the scatterer, is small. More specifically, in the present embodiment, in a case where the reproducibility of the appearance with the transmissive light source is more prioritized, the priority level becomes higher (see  FIG. 17 ), and accordingly, a monotonous-decrease relationship may be used in the case of obtaining the scattering characteristics S based on the priority level P. For example, the scattering characteristics S are calculated from the priority level P by using the following formula (10).
 
 S= 1/ P   Formula (10)
 
     Incidentally, the formula (10) used in the present embodiment to derive the scattering characteristics S is just an example, and as long as there is established a simple-decrease relationship between the priority level P and the scattering characteristics S, another function may be used to calculate the scattering characteristics S. 
     In step S 1806 , the coloring material amount determining unit  1605  determines the amount of the coloring material necessary for printing based on the scattering characteristics, and sends the coloring material amount data to the preview screen creating unit  1606 . The details of the processing in step S 1806  will be described later. 
     In step S 1807 , the preview screen creating unit  1606  creates the preview screen based on the coloring material amount data. More specifically, the preview screen creating unit  1606  converts the CMYK values obtained in step S 1806  into CIELab values for creating the preview screen in the case of using the reflective light source by using the LUT held in the data holding unit  1607 , and converts the CIELab values into sRGB values. Likewise, the preview screen creating unit  1606  converts the CMYK values obtained in step S 1806  into CIELab values for creating the preview screen in the case of using the transmissive light source, and converts the CIELab values into sRGB values. The preview screen is created based on these conversions, and the created preview screen is displayed in the output image (preview) display area  1705 . 
     In step S 1808 , the CPU determines whether or not the user presses the output button  1707 . As a result of the determination, in a case where the output button  1707  is pressed, the process proceeds to step S 1809 . On the other hand, in a case where the output button  1707  is not pressed, the process returns to step S 1801 . 
     In step S 1809 , the image processing apparatus  1600  sends, to the image forming unit  1610 , print data including the coloring material amount data created by the coloring material amount determining unit  1605 . 
     &lt;Processing for Determining the Amount of the Coloring Material&gt; 
       FIG. 20  is a flowchart of the processing (step S 1806  in  FIG. 18 ) for determining the amount of the coloring material according to the present embodiment. The processing for determining the amount of the coloring material will be described below in detail with reference to  FIG. 20 . 
     In step S 2001 , the coloring material amount determining unit  1605  obtains the reflective image data, the transmissive image data, and the scattering characteristics S. As described above, the reflective image data and the transmissive image data are image data obtained by capturing an image of the translucent body, and have CIELab values as the pixel values of each pixel. 
     In step S 2002 , the coloring material amount determining unit  1605  uses the information held in the data holding unit  1607  to determine the amount of the white ink based on the scattering characteristics obtained in step S 2001 . In the present embodiment, as shown in  FIG. 21A , the data holding unit  1607  holds a graph prescribing a correspondence relationship between the scattering characteristics S and the amount of the white ink W, and the coloring material amount determining unit  1605  uses this graph to obtain the amount of the white ink corresponding to the scattering characteristics. Incidentally, the graph prescribing the correspondence relationship between the scattering characteristics S and the amount of the white ink W is prepared beforehand by performing printing by the image forming unit  1610  under a plurality of conditions in which the amount of the white ink varies, and measuring the resultant printed object, and the prepared graph is held in the data holding unit  1607 . 
     In step S 2003 , the coloring material amount determining unit  1605  uses the information held in the data holding unit  1607  to determine the amounts of the color inks based on either of the reflective image data and the transmissive image data obtained in step S 2001  and the amount of the white ink determined in step S 2002 . More specifically, in order to determine the amounts of the color inks, the reflective image data is used in a case where the scattering characteristics obtained in step S 2001  are ⅕ or more (the priority level is 5 or less) and the transmissive image data is used in a case where the scattering characteristics are ⅙ or less (the priority level is 6 or more). In the present embodiment, as shown in  FIGS. 21A and 21B , the data holding unit  1607  holds the color conversion LUT for each allowable amount of the white ink for converting the CIELab values into the CMYK values. Accordingly, the coloring material amount determining unit  1605  uses one of the color conversion LUTs to convert the CIELab values of the reflective image data or the CIELab values of the transmissive image data into the CMYK values, thereby obtaining the amounts of the color inks (the CMYK values for each pixel). In a case where the Lab values before the conversion are not held in the color conversion LUT to be used, it is possible to calculate the CMYK values by using interpolation calculation, and it is possible to use, as an interpolation method, an already-known method such as tetrahedral interpolation or cubic interpolation. Incidentally, the color conversion LUT is prepared beforehand for each amount of the white ink by obtaining each of the amounts of the inks of four colors CMYK (a combination of the color inks) corresponding to the color values (CIELab values) to be reproduced, and the prepared color conversion LUT is held in the data holding unit  1607 . It is possible to use any already-known method as a method for preparing the color conversion LUT. 
     The above is the details of the processing for determining the amount of the coloring material. The data holding unit  1607  may hold, as temporary data, data indicative of the amount of the white ink and the amounts of the color inks for each pixel as determined by the above processing. 
     As described above, the image processing apparatus of the present embodiment displays the UI screen through which the user can designate the priority level indicating parameters for adjusting a degree of contribution between the reflective characteristics of the translucent body and the transmissive characteristics of the translucent body to the reproduction of the appearance. The image processing apparatus derives the scattering characteristics based on the priority level designated by the user, and derives the amounts of the CMYK color inks and the amount of the white color based on the derived scattering characteristics. Then, the image forming apparatus actually performs printing based on the derived amounts of the color inks and the derived amount of the white ink. Accordingly, in the present embodiment, the user can obtain the printed object which reproduces the appearance of translucent body in the desired priority level. 
     Further, in the above-described embodiments, explanation has been made on the case of using the CIELab color space as color space which does not depend on a device. However, it is also possible to use color space which does not depend on another device. For example, it is possible to use color space such as CIE tristimulus values X, Y, and Z or CIELUV. Further, it is also possible to use color perception space for a color appearance model such as CIECAM97, CIECAM97s, or CIECAM02. 
     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. 
     According to the present invention, it is possible to suitably reproduce the appearance of the printed object for the translucent body. 
     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 Applications No. 2015-064527, filed Mar. 26, 2015, and No. 2015-133864, filed Jul. 2, 2015, which are hereby incorporated by reference wherein in their entirety.