如何使用Asp.net mvc实时生成缩率图到硬盘？

/// <summary>
 /// 生成图片缩率图Action
 /// </summary>
 /// <param name="p">原图url</param>
 /// <param name="id">图片尺寸以及生成缩率图的类型</param>
 /// <returns></returns>
 [ValidateInput(false)]
 public ActionResult Index(string p, string id)
 {
 if (string.IsNullOrEmpty(p))
 {
 return new HttpStatusCodeResult(404);
 }

 string oPath = Regex.Replace(p, @"http[s]?://(.*?)/", "/", RegexOptions.IgnoreCase);
 int? oWidth = 200, oHeight = 200;
 int cutMode = 3;
 string pPath;
 string oDir;

 if (!string.IsNullOrEmpty(id))
 {
 string[] ss = id.Split(new char[] { '_' }, StringSplitOptions.RemoveEmptyEntries);
 if (ss.Length < 2)
 {
  return new HttpStatusCodeResult(404);
 }
 if (ss.Length > 2)
 {
  cutMode = int.Parse(ss[2]);
 }
 oPath = oPath.Insert(oPath.LastIndexOf('/') + 1, string.Format("{0}_{1}_{2}_", ss[0], ss[1], cutMode));
 oWidth = int.Parse(ss[0]);
 oHeight = int.Parse(ss[1]);
 }

 pPath = Server.MapPath(oPath);
 oDir = Path.GetDirectoryName(pPath);

 if (!System.IO.File.Exists(pPath))
 {
 byte[] imagebytes = FileHelper.DownLoadFile(p);
 if (!Directory.Exists(oDir))
 {
  Directory.CreateDirectory(oDir);
 }
 FileHelper.MakeThumbnail(FileHelper.BytToImg(imagebytes), oWidth.Value, oHeight.Value, (ThumbnailMode)cutMode, pPath, true);
 }

 return File(pPath, FileHelper.GetContentTypeByExtension(Path.GetExtension(pPath).ToLower()));
 }

 public class FileHelper
 {
 /// <summary>
 /// 图片后缀和ContentType对应字典
 /// </summary>
 static Dictionary<string, string> extensionContentTypeDic;

 static FileHelper()
 {
 if (extensionContentTypeDic == null)
 {
 //.jpg", ".png", ".gif", ".jpeg
 extensionContentTypeDic = new Dictionary<string, string>();
 extensionContentTypeDic.Add(".jpg", "image/jpeg");
 extensionContentTypeDic.Add(".png", "image/png");
 extensionContentTypeDic.Add(".gif", "image/gif");
 extensionContentTypeDic.Add(".jpeg", "image/jpeg");
 }
 }
 /// <summary>
 /// 根据后缀名获取extension
 /// </summary>
 /// <param name="extension"></param>
 /// <returns></returns>
 public static string GetContentTypeByExtension(string extension)
 {
 if (extensionContentTypeDic.ContainsKey(extension))
 {
 return extensionContentTypeDic[extension];
 }
 return null;
 }

 /// <summary > 
 /// 将Image对象转化成二进制流 
 /// </summary > 
 /// <param name="image" > </param > 
 /// <returns > </returns > 
 public static byte[] ImageToByteArray(Image image)
 {
 MemoryStream imageStream = new MemoryStream();
 Bitmap bmp = new Bitmap(image.Width, image.Height);
 Graphics g = Graphics.FromImage(bmp);
 g.DrawImage(image, new System.Drawing.Rectangle(0, 0, image.Width, image.Height));
 try
 {
 bmp.Save(imageStream, image.RawFormat);
 }
 catch (Exception e)
 {

 bmp.Save(imageStream, System.Drawing.Imaging.ImageFormat.Jpeg);
 }
 byte[] byteImg = imageStream.GetBuffer();
 bmp.Dispose();
 g.Dispose();
 imageStream.Close();
 return byteImg;
 }

 /// <summary> 
 /// 字节流转换成图片 
 /// </summary> 
 /// <param name="byt">要转换的字节流</param> 
 /// <returns>转换得到的Image对象</returns> 
 public static Image BytToImg(byte[] byt)
 {
 MemoryStream ms = new MemoryStream(byt);
 Image img = Image.FromStream(ms);
 ms.Close();
 return img;
 }

 /// <summary>
 /// 生成缩率图
 /// </summary>
 /// <param name="originalImage">原始图片Image</param>
 /// <param name="width">缩率图宽</param>
 /// <param name="height">缩率图高</param>
 /// <param name="mode">生成缩率图的方式</param>
 /// <param name="thumbnailPath">缩率图存放的地址</param>
 public static Image MakeThumbnail(Image originalImage, int width, int height, ThumbnailMode mode, string thumbnailPath, bool isSave = true)
 {
 int towidth = width;
 int toheight = height;

 int x = 0;
 int y = 0;
 int ow = originalImage.Width;
 int oh = originalImage.Height;
 switch (mode)
 {
 case ThumbnailMode.HW://指定高宽缩放（可能变形）  
  break;
 case ThumbnailMode.W://指定宽，高按比例  
  toheight = originalImage.Height * width / originalImage.Width;
  break;
 case ThumbnailMode.H://指定高，宽按比例 
  towidth = originalImage.Width * height / originalImage.Height;
  break;
 case ThumbnailMode.Cut://指定高宽裁减（不变形）  
  if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
  {
  oh = originalImage.Height;
  ow = originalImage.Height * towidth / toheight;
  y = 0;
  x = (originalImage.Width - ow) / 2;
  }
  else
  {
  ow = originalImage.Width;
  oh = originalImage.Width * height / towidth;
  x = 0;
  y = (originalImage.Height - oh) / 2;
  }
  break;

 default:
  break;
 }

 //新建一个bmp图片 
 System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
 //新建一个画板 
 Graphics g = System.Drawing.Graphics.FromImage(bitmap);
 //设置高质量插值法 
 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
 //设置高质量,低速度呈现平滑程度 
 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
 //清空画布并以透明背景色填充 
 g.Clear(Color.Transparent);
 //在指定位置并且按指定大小绘制原图片的指定部分 
 g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
 new Rectangle(x, y, ow, oh),
 GraphicsUnit.Pixel);
 if (!isSave)
 {
 return bitmap;
 }
 try
 {
 //以jpg格式保存缩略图 
 //bitmap.Save(thumbnailPath, bitmap.RawFormat);
 bitmap.Save(thumbnailPath, ImageFormat.Jpeg);
 return bitmap;

 }
 catch (System.Exception e)
 {
 throw e;
 }
 finally
 {
 originalImage.Dispose();
 bitmap.Dispose();
 g.Dispose();
 }
 return null;
 }


 /// <summary>
 /// 下载指定文件
 /// </summary>
 /// <param name="remoteUrl"></param>
 /// <param name="ss"></param>
 public static byte[] DownLoadFile(string remoteUrl)
 {
 WebClient wc = new WebClient();
 try
 {
 return wc.DownloadData(remoteUrl);
 }
 catch (Exception e)
 {
 throw new Exception("下载文件失败");
 }
 }

 }

 public enum ThumbnailMode
 {
 /// <summary>
 /// 指定高宽缩放（可能变形）
 /// </summary>
 HW,
 /// <summary>
 /// 指定高，宽按比例
 /// </summary>
 H,
 /// <summary>
 /// 指定宽，高按比例
 /// </summary>
 W,
 /// <summary>
 /// 指定高宽裁减（不变形） 
 /// </summary>
 Cut,

 }