Smoothing of Polygonal Chains for 2D Shape Representation Using a G2-Continuous Cubic A-Spline

We have developed a G-continuous cubic A-spline, suitable for smoothing polygonal chains used in 2D shape representation. The proposed A-spline scheme interpolates an ordered set of data points in the plane, as well as the direction and sense of tangent vectors associated to these points. We explicitly characterize curve families which are used to construct the A-spline sections, whose members have the required interpolating properties and possess a minimal number of inflection points. The A-spline considered here has many attractive features: it is very easy to construct, it provides us with convenient geometric control handles to locally modify the shape of the curve and the error of approximation is controllable. Furthermore, it can be rapidly displayed, even though its sections are implicitly defined algebraic curves.