点旋转坐标变换

/// <summary>
/// 以中心点逆时针旋转Angle角度
/// </summary>
/// <param name="center">中心点</param>
/// <param name="p1">待旋转的点</param>
/// <param name="angle">旋转角度（弧度）</param>
public PointF PointRotate(PointF center, float xaxiStart, float yaxiStart, double angle)
{
　　PointF result = new PointF();
　　result.X = (xaxiStart - center.X) * (float)Math.Cos(angle) + (yaxiStart - center.Y) * (float)Math.Sin(angle) + center.X;
　　result.Y = -(xaxiStart - center.X) * (float)Math.Sin(angle) + (yaxiStart - center.Y) * (float)Math.Cos(angle) + center.Y;
　　return result;
}