C# GDI winfrom 图像转换椭圆形

现在好多移动端上的人物头像都是椭圆形的，就行winfrom 上能不能设置椭圆形的图像

后台代码

 

        /// <summary>
        /// 选择图像
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnxuztx_Click(object sender, EventArgs e)
        {
            OpenFileDialog open = new OpenFileDialog();
            open.Filter = "图片|*.bmp;*.jpg;*.jpeg;*.png;*.gif;*.bmp;*.tif";
            var dialog = open.ShowDialog();
            if (dialog == DialogResult.OK)
            {
               imageName = System.IO.Path.GetFileName(open.FileName);
               fname = open.FileName;
            }
           //获取原始图像
            pictureBox1.Image = outimage(fname);
          
        }
        /// <summary>
        /// 根据文件路径转出image图像
        /// </summary>
        /// <param name="fname"></param>
        /// <returns></returns>
        public Image outimage(string fname)
        {
            using (var fileStream = new System.IO.FileStream(fname, System.IO.FileMode.Open))
            {
                byte[] bytes = new byte[fileStream.Length];
                fileStream.Read(bytes, 0, bytes.Length);

                var memoryStream = new System.IO.MemoryStream(bytes);
                if (memoryStream != null)
                {
                    return Image.FromStream(memoryStream);
                }
                return null;
            }
        }

 /// <summary>
        /// 重绘原始图像，变椭圆
        /// </summary>
        /// <param name="img"></param>
        /// <returns></returns>
        public Bitmap yximage(Bitmap img)
        {
            int t = 0;
            //图片可能会很大，宽高取小
            if (img.Width > img.Height)
                t = img.Height;
            else
                t = img.Width;

            int w = t, h = t;
            Size size = new Size(w, h);
            //先初始化一个位图对象，来存储截取后的图像
            Bitmap bitmap = new Bitmap(size.Width, size.Height);
            Rectangle rec = new Rectangle(0, 0, w, h);
            
            using (Graphics g = Graphics.FromImage(bitmap))
            {  // 
                using (TextureBrush br = new TextureBrush(img, System.Drawing.Drawing2D.WrapMode.Clamp, rec))
                {
                    br.ScaleTransform(bitmap.Width / (float)rec.Width, bitmap.Height / (float)rec.Height);
                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                    //把图像数据放进椭圆内部
                    g.FillEllipse(br, new Rectangle(Point.Empty, size));
                }
            }
            return bitmap;
 
        }

      /// <summary>
        /// 转换图像圆形
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void buttonZH_Click(object sender, EventArgs e)
        {
            if (pictureBox1.Image != null)
            {
                Bitmap bitiamge = (pictureBox1.Image as Bitmap);
                Image ima = yximage(bitiamge);           
                pictureBox2.Image = ima;
            }         
        }

     /// <summary>
        /// 保存图像
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnbc_Click(object sender, EventArgs e)
        {
            SaveFileDialog sf = new SaveFileDialog();
            sf.Filter="图片|*.bmp;*.jpg;*.jpeg;*.png;*.gif;*.bmp;*.tif";
            if (sf.ShowDialog() == DialogResult.OK)
            {
                pictureBox2.Image.Save(sf.FileName);
            }
        }