当给定的开始,结束和1点位于C#中的贝塞尔曲线时,找到QuadraticBe

static class DrawingUtility
{
    static void bez3pts1(double x0,double y0,double x3,double y3,double x2,double y2,out double x1,out double y1)
    {
        // find chord lengths
        double c1 = Math.Sqrt((x3 - x0) * (x3 - x0) + (y3 - y0) * (y3 - y0));
        double c2 = Math.Sqrt((x3 - x2) * (x3 - x2) + (y3 - y2) * (y3 - y2));
        // guess "best" t
        double t = c1 / (c1 + c2);
        // quadratic Bezier is B(t) = (1-t)^2*P0 + 2*t*(1-t)*P1 + t^2*P2
        // solving gives P1 = [B(t) - (1-t)^2*P0 - t^2*P2] / [2*t*(1-t)] where P3 is B(t)
        x1 = (x3 - (1 - t) * (1 - t) * x0 - t * t * x2) / (2 * t * (1 - t));
        y1 = (y3 - (1 - t) * (1 - t) * y0 - t * t * y2) / (2 * t * (1 - t));
    }

    // pass in a PathFigure and it will append a QuadraticBezierSegment connecting the previous point to int1 and endPt
    static public void QuadraticBezierFromIntersection(PathFigure path,Point startPt,Point int1,Point endPt)
    {
        double x1,y1;
        bez3pts1(startPt.X,startPt.Y,int1.X,int1.Y,endPt.X,endPt.Y,out x1,out y1);
        path.Segments.Add(new QuadraticBezierSegment { Point1 = new Point(x1,y1),Point2 = endPt } );
    }
}