生成缩略图

protected void uploadBtn_Click(object sender, EventArgs e)
    {
        uid = Session["UserId"].ToString();
        FilmVobInfo fvi = (FilmVobInfo)Session[Session.SessionID + FilmVobInfo.UserIdString];
        UploadDB upload = new UploadDB();

        bool fileOK = false;

      
        if (FileUpload1.PostedFile.ContentLength > 1)
        {
            string name = FileUpload1.PostedFile.FileName;                  // 客户端文件路径

            FileInfo file = new FileInfo(name);
            string fileName = file.Name;                                    // 文件名称
            string fileName_s = "s_" + file.Name;                           // 缩略图文件名称
                       string webFilePath = Server.MapPath("~/upload/" + fileName);        // 服务器端文件路径
            string webFilePath_s = Server.MapPath("~/upload/" + fileName_s);

            fviImgPath = "upload/" + fileName_s;
          

            //string size = FileUpload1.PostedFile.ContentLength.ToString();
            if (FileUpload1.HasFile)
            {
               

                FileUpload1.SaveAs(webFilePath);                                // 使用 SaveAs 方法保存文件

                MakeThumbnail(webFilePath, webFilePath_s, 120, 90, "Cut");     // 生成缩略图方法
                String fileExtension = System.IO.Path.GetExtension(FileUpload1.FileName).ToLower();
                String[] alloweExtensions ={ ".gif", ".jpg", ".bmp", "img", "imge", "png" };
                for (int i = 0; i < alloweExtensions.Length; i++)
                {

                    if (fileExtension == alloweExtensions[i])
                    {
                        fileOK = true;
                    }
                }

            }
        }

        else
        {

            fvi.ImgPath = "Images/" + "暂无图片.jpg";
        }

        if (Session[Session.SessionID + FilmVobInfo.UserIdString] == null)
        {
            return;
        }

            if (upload.AddBC( fvi.ImgPath) > -1)
            {

                Panel1.Visible = true;   //Panel上放一些上传成功的文字信息等等。

            }
     
    }

   ///生成缩略图
    public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
    {
        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
        System.Drawing.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(System.Drawing.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 System.Drawing.Rectangle(0, 0, towidth, toheight),
            new System.Drawing.Rectangle(x, y, ow, oh),
            System.Drawing.GraphicsUnit.Pixel);

        try
        {
            //以jpg格式保存缩略图
            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }