生成縮略圖

public class UploadController : Controller
    {
        public ActionResult UploadImage()
        {
            return View();
        }

        [HttpPost]
        public JsonResult UploadImage(HttpPostedFileBase file)
        {
            TResult<string> result = new TResult<string>();

            if (file == null)
            {
                result.Message = "請選擇須要上傳的文件.";
                return Json(result);
            }

            string returnFileString = "";
            string oldFileName = file.FileName;
            string suffix = Path.GetExtension(oldFileName);
            string folder = Server.MapPath("~/UpFiles/");
            string fileName = folder + Guid.NewGuid().ToString("N") + suffix;

            //若是不存在目錄 就建立
            if (!Directory.Exists(folder))
            {
                Directory.CreateDirectory(folder);
            }

            //保存文件
            file.SaveAs(fileName);
            returnFileString = fileName;

            #region 處理縮略圖

            string imageArraySize = Request["ImageArraySize"];
            if (string.IsNullOrWhiteSpace(imageArraySize))
            {
                result.IsSuccess = true;
                result.TData = returnFileString;
                result.Message = "上傳成功";
                return Json(result);
            }

            string[] thumbArray = imageArraySize.Split(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
            if (thumbArray == null || thumbArray.Length <= 0)
            {
                result.IsSuccess = true;
                result.TData = returnFileString;
                result.Message = "上傳成功";
                return Json(result);
            }

            foreach (var item in thumbArray)
            {
                string[] thumbItem = item.Split(new char[] { '*' }, StringSplitOptions.RemoveEmptyEntries);
                if (thumbItem == null || thumbItem.Length != 2)
                {
                    continue;
                }

                string tryWidth = thumbItem[0];
                double width = tryWidth.ToDoubleReMin();
                if (width <= 0)
                {
                    continue;
                }

                string tryHeight = thumbItem[1];
                double height = tryHeight.ToDoubleReMin();
                if (height <= 0)
                {
                    continue;
                }

                string thumbImageSrc = string.Format(fileName.Replace(suffix, "") + "_{0}_{1}{2}", width, height, suffix);
                MakeThumbnail(fileName, thumbImageSrc, (int)width, (int)height, MakeThumbnailModel.WHCut);
                returnFileString += "," + thumbImageSrc;
            }

            #endregion

            result.IsSuccess = true;
            result.TData = returnFileString;
            result.Message = "上傳成功";
            return Json(result);
        }

        /// <summary> 
        /// 生成縮略圖 
        /// </summary> 
        /// <param name="originalImagePath">源圖路徑（物理路徑）</param> 
        /// <param name="thumbnailPath">縮略圖路徑（物理路徑）</param> 
        /// <param name="width">縮略圖寬度</param> 
        /// <param name="height">縮略圖高度</param> 
        /// <param name="mode">生成縮略圖的方式</param>     
        public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, MakeThumbnailModel mode)
        {
            Image originalImage = 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 MakeThumbnailModel.WH://指定高寬縮放（可能變形）                 
                    break;
                case MakeThumbnailModel.OnlyW://指定寬，高按比例                     
                    toheight = originalImage.Height * width / originalImage.Width;
                    break;
                case MakeThumbnailModel.OnlyH://指定高，寬按比例 
                    towidth = originalImage.Width * height / originalImage.Height;
                    break;
                case MakeThumbnailModel.WHCut://指定高寬裁減（不變形）                 
                    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;
            }

            //新建一個bmp圖片 
            Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

            //新建一個畫板 
            Graphics g = System.Drawing.Graphics.FromImage(bitmap);

            //設置高質量插值法 
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //設置高質量,低速度呈現平滑程度 
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空畫布並以透明背景色填充 
            g.Clear(Color.Transparent);

            //在指定位置而且按指定大小繪製原圖片的指定部分 
            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
                new Rectangle(x, y, ow, oh),
                GraphicsUnit.Pixel);

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

    public enum MakeThumbnailModel
    {
        /// <summary>
        /// 指定高寬縮放（可能變形）
        /// </summary>
        WH = 1,

        /// <summary>
        /// 指定寬，高按比例   
        /// </summary>
        OnlyW = 2,

        /// <summary>
        /// 指定高，寬按比例 
        /// </summary>
        OnlyH = 3,

        /// <summary>
        /// 指定高寬裁減（不變形）
        /// </summary>
        WHCut = 4
    }