看看Help TCanvas.PolyBezier 和TCanvas.PolyBezierTo
Draws a set of B閦ier curves.
procedure PolyBezier(const Points: array ofTPoint);
Description
Use PolyBezier to draw cubic B閦ier curves using the endpoints and control points specified by the Points parameter. The first curve is drawn from the first point to the fourth point, using the second and third points as control points. Each subsequent curve in the sequence needs exactly three more points: the ending point of the previous curve is used as the starting point, the next two points in the sequence are control points, and the third is the ending point.
The Points parameter gives the endpoints to use when generating the B閦ier curves.
This procedure draws lines by using the current pen.
Tip: Use the Slice function to pass a portion of an array of points to the PolyBezier method. For example, to form a B閦ier curve using the first ten points from an array of 100 points, use the Slice function as follows:
Canvas.PolyBezier(Slice(PointArray, 10));
Control points after a[Index+3] are ignored. Nothing happens if there aren't enough control points
