下载网页图片

//实例化WebRequest对象   

 WebRequest wreq = WebRequest.Create(url);// url图片地址

 //创建HttpWebResponse对象

HttpWebResponse wresp = (HttpWebResponse)wreq.GetResponse();

//创建流对象

Stream s = wresp.GetResponseStream();

System.Drawing.Image img;

 img = System.Drawing.Image.FromStream(s);               

  img.Save(Server.MapPath("保存路径") +"保存得图片名称", ImageFormat.Png);// ImageFormat.Png为图片格式