protected void Page_Load(object sender, EventArgs e)
{
  WebRequest myrequest = WebRequest.Create("http://xxxxx/userface.jpg");
  WebResponse myresponse = myrequest.GetResponse();
  Stream imgstream = myresponse.GetResponseStream();
  System.Drawing.Image img = System.Drawing.Image.FromStream(imgstream);
  //img.Save(Server.MapPath("test.jpg"),System.Drawing.Imaging.ImageFormat.Jpeg);
  MemoryStream ms = new MemoryStream();
  img.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
  Response.ClearContent(); //需要输出图象信息 要修改HTTP头 
  Response.ContentType = "image/gif";
  Response.BinaryWrite(ms.ToArray());
}