一个坐标点围绕任意中心点旋转--C#实现

假设对图片上任意点(x,y)，绕一个坐标点(rx0,ry0)逆时针旋转RotaryAngle角度后的新的坐标设为(x‘, y‘)，有公式：

x‘= (x - rx0)*cos(RotaryAngle) + (y - ry0)*sin(RotaryAngle) + rx0 ;
    y‘=-(x - rx0)*sin(RotaryAngle) + (y - ry0)*cos(RotaryAngle) + ry0 ;

/// <summary>
        /// 对一个坐标点按照一个中心进行旋转
        /// </summary>
        /// <param name="center">中心点</param>
        /// <param name="p1">要旋转的点</param>
        /// <param name="angle">旋转角度，笛卡尔直角坐标</param>
        /// <returns></returns>
        private  Point PointRotate(Point center, Point p1, double angle)
        {
            Point tmp = new Point();
            double angleHude = angle * Math.PI / 180;/*角度变成弧度*/
            double x1 = (p1.X - center.X) * Math.Cos(angleHude) + (p1.Y - center.Y ) * Math.Sin(angleHude) + center .X;
            double y1 = -(p1.X - center.X) * Math.Sin(angleHude) + (p1.Y - center.Y) * Math.Cos(angleHude) + center.Y;
            tmp.X = (int)x1;
            tmp.Y = (int)y1;
            return tmp;
        }