A Formal Description for Two-Dimensional Patterns

A "s t ruc tura l descript ion" for two-dimensional black and white patterns is defined as the set of contour l ines for an appropriate function which f i ts the binary pat tern. These contour lines are mutually nonintersecting closed polygonal curves with edges in only eight different directions and they represent the bound­ ar ies between connected black and white areas of the pattern. Rigorous procedures are described to t rans­ fo rm a "mat r i x pat tern" into a "st ructura l descr ipt ion" and vice versa. Advantages of this method for descr ib­ ing patterns previous to pattern recognition are d is ­ cussed at some length.