1. An image processing apparatus comprising: at least one processor configured to execute: an image decomposing unit configured to decompose a pixel value of each pixel forming an original image into an illumination component and a reflectance component to generate an illumination component image; and an image composing unit configured to reflect the illumination component on a sample image serving as a sample of image, and to combine the sample image having the illumination component reflected thereon with the original image, wherein the pixel value is decomposed according to the formula: 
 I=SR wherein I represents the pixel value, S represents the illumination component, and R represents the reflectance component.