/// <summary>
        ///  仿qq非直线箭头：采用填充多边形的方法
        /// </summary>
        /// <param name="g"></param>
        /// <param name="p"></param>
        /// <param name="start"></param>
        /// <param name="end"></param>
        private void DrawUArrowF(Graphics g, Pen p, Point start, Point end)
        {
            int par = 5;
            par = ((int)p.Width - 1) * 5 + par;//默认为10
            double Length = Math.Sqrt(Math.Abs(start.X - end.X) * Math.Abs(start.X - end.X) + Math.Abs(start.Y - end.Y) * Math.Abs(start.Y - end.Y));
            if (Length > 5)
            {
                g.CompositingQuality = CompositingQuality.HighQuality;
                double k = Math.Atan2((double)(end.Y - start.Y), (double)(end.X - start.X));//返回的是原点至点(x,y)的方位角，即与 x 轴的夹角
                double siny = Math.Sin(k);
                double cosy = Math.Cos(k);
                //箭头是一个底边=高=par的等腰三角形
                //运用正弦、余弦与边之间的关系；sin30°=cos60°求出坐标
                PointF point1 = new PointF(end.X + (float)(-par * cosy - (par / 2.0 * siny)), end.Y + (float)(-par * siny + (par / 2.0 * cosy)));
                PointF point2 = new PointF(end.X + (float)(-par * cosy + (par / 2.0 * siny)), end.Y - (float)(par / 2.0 * cosy + par * siny));
                PointF[] ps = { end, point1, point2 };
                //g.DrawPolygon(p, ps);//画三角形会出现偏移量的问题
 
                float offsetX = (float)(par * siny / 3.5);
                float offsetY = (float)(par * cosy / 3.5);
                PointF point3 = new PointF(end.X + (float)(-par * cosy - (par / 2.0 * siny)) + offsetX, end.Y + (float)(-par * siny + (par / 2.0 * cosy)) - offsetY);
                PointF point4 = new PointF(end.X + (float)(-par * cosy + (par / 2.0 * siny) - offsetX), end.Y - (float)(par / 2.0 * cosy + par * siny) + offsetY);
                PointF[] pj = { start, point3, point4 };
                //g.DrawPolygon(p, pj);//画三角形会出现偏移量的问题            
                FillMode flMode = FillMode.Alternate;
                SolidBrush brush = new SolidBrush(p.Color);
                //g.FillPolygon(brush, ps, flMode);//填充三角形箭头部
                //g.FillPolygon(brush, pj, flMode);//填充三角形箭身
                //两个三角形组合出现缝隙
                PointF[] pp = { start, point3, point1, end, point2, point4 };//填充箭头多边形
                g.FillPolygon(brush, pp, flMode);
                Pen px = new Pen(p.Color, 1);//新定义一个pen画一条直线，防止箭尾太细
                g.DrawLine(px, start, end);
                px.Dispose();
            }
        }