copy Curve2D getCenterPoint getLength isClosed

copy() virtual Geometry2D * copy ( void  ) const pure virtual 实现了 Geometry2D. 在 ArcofCircle2D, ArcofEllipse2D, BezierCurve2D, BSplineCurve2D, Circle2D, Ellipse2D, Hyperbola2D, Line2D, LineSegment2D, NURBSCurve2D, Parabola2D , 以及 PolyLine2D 内被实现.