1. A method of compressing an image block comprising multiple image elements, said method comprising the steps of: determining a first and a second color codeword defining multiple discrete color representations along a line in a color space; and determining a color modifying codeword representing a set of multiple color modifiers for modifying said multiple discrete color representations along at least one selected extension vector in said color space to obtain, for each of said discrete multiple color representations, a set of multiple color points, wherein said multiple color points of said sets are located on a surface defined by said multiple color representations and said at least one selected extension vector and wherein colors of said image elements are approximated by said multiple color points of said sets.