private void Form1_Load(object sender, EventArgs e)

        {

            string file =System.IO.Path.Combine(Environment.CurrentDirectory, @"11.jpg");

            try

            {

                Image i = new Bitmap(file);

                pbO.Image = i;

                pbD1.Image = WayOne(file);

                pbD2.Image = WayTwo(file);

                pbS1.Image = WaySOne(file);

                pbS2.Image = WaySTwo(file);

            }

            catch (Exception ex)

            {

                MessageBox.Show(ex.Message);

            }

        }

        private Bitmap WayOne(string file)

        {

            using (Image i = new Bitmap(file))

            {

                Bitmap b = new Bitmap(i.Width, i.Height);

                using (Graphics g = Graphics.FromImage(b))

                {

                    g.FillEllipse(new TextureBrush(i), , , i.Width, i.Height);

                }

                return b;

            }

        }

        private Bitmap WayTwo(string file)

        {

            using (Image i = new Bitmap(file))

            {

                Bitmap b = new Bitmap(i.Width, i.Height);

                using (Graphics g = Graphics.FromImage(b))

                {

                    g.DrawImage(i, , , b.Width, b.Height);

                    int r = Math.Min(b.Width, b.Height) / ;

                    PointF c = new PointF(b.Width / 2.0F, b.Height / 2.0F);

                    for (int h = ; h < b.Height; h++)

                        for (int w = ; w < b.Width; w++)

                            if ((int)Math.Pow(r, ) < ((int)Math.Pow(w * 1.0 - c.X, ) + (int)Math.Pow(h * 1.0 - c.Y, )))

                            {

                                b.SetPixel(w, h, Color.Transparent);

                            }

                }

                return b;

            }

        }

        private Bitmap WaySOne(string file)

        {

            using (Image i = new Bitmap(file))

            {

                Bitmap b = new Bitmap(i.Width, i.Height);

                using (Graphics g = Graphics.FromImage(b))

                {

                    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                    using (System.Drawing.Drawing2D.GraphicsPath p = new System.Drawing.Drawing2D.GraphicsPath(System.Drawing.Drawing2D.FillMode.Alternate))

                    {

                        p.AddEllipse(, , i.Width, i.Height);

                        g.FillPath(new TextureBrush(i), p);

                    }

                    //g.FillEllipse(new TextureBrush(i), 0, 0, i.Width, i.Height);

                }

                return b;

            }

        }

        private Bitmap WaySTwo(string file)

        {

            using (Image i = new Bitmap(file))

            {

                Bitmap b = new Bitmap(i.Width, i.Height);

                using (Graphics g = Graphics.FromImage(b))

                {

                    g.DrawImage(i, , , b.Width, b.Height);

                    int r = Math.Min(b.Width, b.Height) / ;

                    PointF c = new PointF(b.Width / 2.0F, b.Height / 2.0F);

                    for (int h = ; h < b.Height; h++)

                        for (int w = ; w < b.Width; w++)

                            if ((int)Math.Pow(r, ) < ((int)Math.Pow(w * 1.0 - c.X, ) + (int)Math.Pow(h * 1.0 - c.Y, )))

                            {

                                b.SetPixel(w, h, Color.Transparent);

                            }

                    //画背景色圆

                    using (Pen p = new Pen(System.Drawing.SystemColors.Control))

                        g.DrawEllipse(p, , , b.Width, b.Height);

                }

                return b;

            }

        }