asp.net输出 png 图像，

1 MemoryStream MemStream = new MemoryStream();2 Bitmap bmp = new Bitmap(200, 60);3 Graphics g = Graphics.FromImage(bmp);4 g.Clear(Color.White);5 g.DrawEllipse(new Pen(new SolidBrush(Color.Blue)), 10, 10, 180, 40);6 Response.ClearContent();7 Response.ContentType = "image/png";8 bmp.Save(MemStream, ImageFormat.Png);         9 MemStream.WriteTo(Response.OutputStream);