Color and pseudo-color images

A color image is usually represented by three functions of space. In most color formats, the three functions are for three primary colors such as red, green and blue $f_r(x,y)$, $f_g(x,y)$, and $f_b(x,y)$, or some other three parameters such as intensity, hue and saturation, $f_i(x,y)$, $f_h(x,y)$, and $f_s(x,y)$.

Sometimes artificial colors can be assigned to a gray level image to better distinguish visually the different gray levels.

The display of gray level, pseudo-color and true-color images on a monitor screen through color-map (color lookup table) is illustrated below.