使用ASP.NET抓取远程图片保存到本地，是个不错的主意，这样图片的访问速度就快，以下是本站原创的保存远程图片到本地的函数，支持.bmp,.jpg,.jpeg,.gif,.png等格式的远程图片。

源代码如下：

导入命名空间

using System.Net;
using System.IO;
using System.Drawing.Imaging;

   /// <summary>
    /// 下载远程图片保存到本地
    /// </summary>
    /// <param name="savedir">本地保存路径</param>
    /// <param name="imgpath">远程图片文件</param>
    /// <returns></returns>
    public string downRemoteImg(string savedir,string imgpath)
    {
        if (string.IsNullOrEmpty(imgpath))
            return string.Empty;
        else
        {
            string imgName = string.Empty;
            string imgExt = string.Empty;
            string saveFilePath = string.Empty;
            imgName = imgpath.Substring(imgpath.LastIndexOf("/"), imgpath.Length - imgpath.LastIndexOf("/"));
            imgExt = imgpath.Substring(imgpath.LastIndexOf("."), imgpath.Length - imgpath.LastIndexOf("."));
           
            saveFilePath = Server.MapPath(savedir);
            if (!Directory.Exists(saveFilePath))
                Directory.CreateDirectory(saveFilePath);

            try
            {
                WebRequest wreq = WebRequest.Create(imgpath);
                wreq.Timeout = 10000;
                HttpWebResponse wresp = (HttpWebResponse)wreq.GetResponse();
                Stream s = wresp.GetResponseStream();
                System.Drawing.Image img;
                img = System.Drawing.Image.FromStream(s);
                switch (imgExt.ToLower())
                {
                    case ".gif":
                        img.Save(saveFilePath + imgName, ImageFormat.Gif);
                        break;
                    case ".jpg":
                    case ".jpeg":
                        img.Save(saveFilePath + imgName, ImageFormat.Jpeg);
                        break;
                    case ".png":
                        img.Save(saveFilePath + imgName, ImageFormat.Png);
                        break;
                    case ".icon":
                        img.Save(saveFilePath + imgName, ImageFormat.Icon);
                        break;
                    case ".bmp":
                        img.Save(saveFilePath + imgName, ImageFormat.Bmp);
                        break;
                }

                img.Dispose();
                s.Dispose();

                return savedir + imgName;
            }
            catch
            {
                return imgpath;
            }
        }
    }

使用方法：

如保存到本地的test目录：

Response.Write(this.downRemoteImg("test", "http://www.xueit.com/ads/top760.gif"));