The Kubelka-Munk function is simple but it ignores the film?s thickness, so
its applications are greatly limited. Though the exact relationship between
the Kubelka-Munk function and the thickness can be derived from a
differential model, it is too complex to be practically used. Here a
modification is suggested by taking the thickness effect and the
temperature effect into account, and the validity is widely enlarged. The
modified Kubelka-Munk theory can be used as a color-matching model for
colorful fabrics. If the porosity of the film is considered, a fractal
modification with two-scale fractal derivative has to be adopted.