IFS representation can be extended to a grayscale image by considering the image's graph as a subset of R 3 {\displaystyle \mathbb {R} ^{3}} . For a grayscale image u(x,y), consider the set S = {(x,y,u(x,y))}. Then similar to the binary case, S is described by an IFS using a set of contraction mappings ƒ1,...,ƒN, but in R 3 {\displaystyle \mathbb {R} ^{3}} ,