Abstract :
It is well known that a Steiner triple system (STS) on image points, an image, can be seen as a collection of 3-subsets of its point set, called triples, such that each pair of points occurs in exactly one triple as well as a decomposition of a complete graph on image vertices into cycles of length 3. By combining those two views on STSs we develop a method for its weak coloring. This method enables us to show that each image is 4-colorable, which in turn implies that the chromatic spectrum of image is image
