这段代码可以抓取指定的url的网络图片，并保存到本地

public Bitmap Get_img()          {              Bitmap img = null;              HttpWebRequest req;              HttpWebResponse res = null;                  try                  {                      System.Uri httpUrl = new System.Uri("http://xxx.com/xxx.png ");                      req = (HttpWebRequest)(WebRequest.Create(httpUrl));                      req.Timeout = 180000; //设置超时值10秒                         req.UserAgent = "XXXXX";                      req.Accept = "XXXXXX";                      req.Method = "GET";                      res = (HttpWebResponse)(req.GetResponse());                              img = new Bitmap(res.GetResponseStream());//获取图片流                                      img.Save(@"E:/" + DateTime.Now.ToFileTime().ToString() + ".png");//随机名                  }                     catch (Exception ex)                  {                       string aa= ex.Message;                  }                  finally                  {                      res.Close();                  }                       return img;          }