1. A method of realism assessment of an image composite, comprising: providing the image composite having a foreground and a background; transforming the foreground and the background into a color space, wherein the transformed color space has a first axis representing luminance information, and a second axis and a third axis representing chromatic information; projecting the foreground and the background to a subspace represented by the second axis and the third axis; and assessing the image composite, in the projected subspace, according to a linearity of color distribution of the foreground and a linearity of color distribution of the background, and further according to a relationship between the color distribution of the foreground and the color distribution of the background.