使用http协议下载网络图片 - 陈力

     出于公司的一个需求，我要写一个下载网易微博的一个头像，但是网易微博的的图片是不允许外链的，所以我们只下载它，好了动手了，呵呵

    一开始我用这样来读流

 

 using (var stream = response.GetResponseStream())
            {


                //byte[] bytes = new byte[stream.Length];
                //stream.Read(bytes, 0, bytes.Length);
                //// 设置当前流的位置为流的开始   
                //stream.Seek(0, SeekOrigin.Begin);

            }

但是提示说，Strem不支持seek ，一到strem.length就开始报错，原因就在于 一个值得探索的未知

 

  所以只能用折中的方式来替代了

  byte[] photocontent = new Byte[response.ContentLength];
                 stream.Read(photocontent, 0, (int)response.ContentLength );

 

需要特别注意的是//stream.Read(content, 0, (int)webreponse.ContentLength );

//只能读取到3799字节的数据，在网上查了好久，没有找到怎么回事，后来，想到了解决大文件上传显示进度问题时，用到的//HttpWorkerRequest.ReadEntityBod（），需要检测是否读取完毕，进行多次读取才可以。

int readecount = 0;
                while (readecount < (int)webreponse.ContentLength)
                {
                    readecount += stream.Read(photocontent, readecount, (int)webreponse.ContentLength - readecount);


                }

 

 剩下就是我下载163 的图片的全部过程了

 Uri uri = new Uri("http://oimagec4.ydstatic.com/image?w=48&h=48&url=http%3A%2F%2Fos.blog.163.com%2Fcommon%2Ftinyava.s%3Fhost%3Dthetimeweekly%26type%3D1%26rnd%3D0.28753444320203836");
            var request = WebRequest.Create(uri) as HttpWebRequest;
            request.AllowAutoRedirect = true;
            request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
            request.Timeout = 6000;
            request.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip;
            request.Headers["Accept-Encoding"] = "gzip, deflate";
            request.Accept = "*/*";
            //request.Headers["host"] = "www.aqlife.com";
            //request.Connection = "Keep-Alive";
            var response = request.GetResponse() as HttpWebResponse;
            using (var stream = response.GetResponseStream())
            {
                //var bmp = new Bitmap(stream);
                //this.pictureBox1.Image = bmp;
                // stream.to              
                 byte[] photocontent = new Byte[response.ContentLength];
                 stream.Read(photocontent, 0, (int)response.ContentLength );
               
              
            }

欢迎大家拍砖。