1. An image generation device that generates, based on information regarding a shape of a surface of an object, a two-dimensional image of the object which (i) is a high-quality image of the object having a resolution higher than a resolution of a low-quality image from which the information regarding the shape of the surface of the object is obtained and (ii) more clearly shows the shape of the surface of the object than the low-quality image, the object of the two-dimensional image being illuminated by a light source and viewed from a viewpoint, said image generation device comprising: an information obtainment unit configured to obtain position information of the light source, position information of the viewpoint, and geometric normal information regarding the shape, the geometric normal information specifying a vertical vector of a point on the surface of the object; a geometric parameter calculation unit configured to calculate, for each point of the surface of the object corresponding to a pixel in the two-dimensional image, a first geometric parameter regarding the shape by performing a predetermined arithmetic operation using the position information of the light source, the position information of the viewpoint, and the geometric normal information; a high-resolution database unit in which an exemplum is previously stored, the exemplum being a geometric parameter that indicates a mesostructure of a portion of the surface and has a spatial resolution higher than a spatial resolution of the geometric normal information; an exemplum expansion unit configured to read out the exemplum from said high-resolution database unit, and spatially increase the readout exemplum so that a spatial region indicated by the readout exemplum is expanded to cover the surface of the object in the two-dimensional image; a geometric parameter modification unit configured to calculate a modified geometric parameter by modifying the first geometric parameter using the spatial region expanded by said exemplum expansion unit; an image generation unit configured to calculate a pixel value of each of the points of the surface of the object corresponding to a pixel in the two-dimensional image by applying the modified geometric parameter to a reflection model for deciding the pixel value, and to generate the two dimensional image; a first image capture unit configured to generate the low-quality image by capturing an image of the object; and a separation unit configured to separate the low-quality image generated by said first image capture unit into specular reflection components of the low-quality image and diffuse reflection components of the low-quality image, wherein said geometric parameter calculation unit, said exemplum expansion unit, said geometric parameter modification unit, and said image generation unit perform the calculating of the first geometric parameter, the reading out and the increasing, the calculating of the modified geometric parameter, and the calculating of the pixel value and the generating of the two-dimensional image, respectively, to generate specular reflection components which are different from the specular reflection components of the low-quality image separated by said separation unit, wherein said image generation unit is configured to generate the two-dimensional image by synthesizing (i) an image using the specular reflection components which are different from the specular reflection components of the low-quality image separated by said separation unit with (ii) an image using the diffuse reflection components of the low-quality image separated by said separation unit, wherein said exemplum expansion unit includes an exemplum conformity expansion unit configured to spatially increase the readout exemplum with specular reflection while keeping a correlation between the specular reflection components of the low-quality image and the diffuse reflection components of the low-quality image separated by said separation unit, wherein said exemplum conformity expansion unit is configured to, when expanding a first region image having the specular reflection components of the low-quality image into a second region image having the specular reflection components of the low-quality image, (i) estimate transformation from a third region image having the diffuse reflection components of the low-quality image and corresponding to the first region image into a fourth region image having the diffuse reflection components of the low-quality image and corresponding to the second region image, and (ii) apply transformation equivalent to the estimated transformation to the first region image, in order to spatially increase the readout exemplum, wherein the first geometric parameter is a value of an angle between (i) a half vector generated by adding a unit vector indicating a direction of the light source with a unit vector indicating a direction of the viewpoint and (ii) a geometric normal vector of a point corresponding to the first geometric parameter, the geometric normal vector being the vertical vector of the point on the surface of the object, and wherein the image generation device further comprises: a second image capture unit configured to generate an image by capturing an image of a portion of the object with a resolution higher than a resolution of the low-quality image, the portion corresponding to a highlight region of the low-quality image to have a higher resolution in the two-dimensional image; a second geometric parameter estimation unit configured to estimate a second geometric parameter using, as an objective function, a pixel value of the image generated by said second image capture unit, the second geometric parameter indicating the shape of the surface of the object; and an exemplum generation unit configured to generate the exemplum using the second geometric parameter estimated by said second geometric parameter estimation unit, and to store the exemplum into said high-resolution database unit.