生成缩略图 - 到了,明天

    /// <summary>
    ///根据传入的相对路径，以“/”号分裂，判断各级文件夹是否存在，不存在则创建文件夹。
    /// </summary>
    /// <param name="FileUrl">相对路径</param>
    /// <returns>返回值</returns>
    ///

 public static void CreateDirectory(string FileUrl)
    {
        string[] DirectoryS=FileUrl.Split(new char[]{\'/\'});
        string dns=string.Empty;
        foreach (string dn in DirectoryS)
        {
            if (dn!="" && dn!=null)
            {
                dns+=dn+"/";
                if(!Directory.Exists(HttpContext.Current.Server.MapPath(dns)))
                {
                    Directory.CreateDirectory(HttpContext.Current.Server.MapPath(dns));
                }
            }
        }
    } 

   /// <summary>
    /// 生成缩略图
    /// </summary>
    /// <param name="originalImagePath">源图路径（物理路径）</param>
    /// <param name="thumbnailPath">缩略图路径（相对站点根目录的路径,不存在则创建）</param>
    /// <param name="width">缩略图宽度</param>
    /// <param name="height">缩略图高度</param>
    /// <param name="mode">生成缩略图的方式:"HW","W","H","Cut"</param> 

 public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
    {
        fso.CreateDirectory(thumbnailPath.Substring(0,thumbnailPath.LastIndexOf(\'/\')));
        thumbnailPath = HttpContext.Current.Server.MapPath(thumbnailPath);
        //HttpContext.Current.Response.Write(originalImagePath); HttpContext.Current.Response.End();

        System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

        int towidth = width;
        int toheight = height;

        int x = 0;
        int y = 0;
        int ow = originalImage.Width;
        int oh = originalImage.Height;

        switch (mode)
        {
            case "HW"://指定高宽缩放（可能变形）               
                break;
            case "W"://指定宽，高按比例                   
                toheight = originalImage.Height * width / originalImage.Width;
                break;
            case "H"://指定高，宽按比例
                towidth = originalImage.Width * height / originalImage.Height;
                break;
            case "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);
        //以jpg格式保存缩略图
        //HttpContext.Current.Response.BinaryWrite(byte[]);
         bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
         originalImage.Dispose();
         bitmap.Dispose();
         g.Dispose();

    }