Generalization and PostScript

With the constantly increasing volume of graphical information in digital form, the automatic processing of this information for drawing vectors becomes more and more important. This usually means selecting vectors from the database, generalizing (data compression) and/or smoothing as needed. There are a number of application programs, which are helpful to perform this. However, occasionally one wants to have more specific control over the procedure. In this presentation our target is a simple vector drawing procedure. We propose to find a continuous smooth graphic representation of a polygon (open, or closed) given by m discrete points. We want to make it device independent. In order to do this, we shall make maximum use of the PostScript programming language. After a very brief introduction to the subject of generalization, the advantages of the parametric form, particularly the Bezier curve – which is the key to the procedure – is discussed in some detail. A few relevant operators of PostScript, the procedures to obtain our desired approximations, both interactively and automatically, will be presented. Some examples will be used to highlight the salient points.