c#上传并改变图片大小

protected void UpLoadPhoto_Click(object sender, ImageClickEventArgs e)    {        if (FileUpload1.HasFile)        {            string fileContentType = FileUpload1.PostedFile.ContentType;            if (fileContentType == "image/bmp" || fileContentType == "image/gif" || fileContentType == "image/pjpeg")            {                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("file/" + fileName); // 服务器端文件路径                 string webFilePath_s = Server.MapPath("file/" + fileName_s);　　// 服务器端缩略图路径                 if (!File.Exists(webFilePath))                {                    try                    {                        FileUpload1.SaveAs(webFilePath); // 使用 SaveAs 方法保存文件                         MakeThumbnail(webFilePath, webFilePath_s, 100, 100, "Cut"); // 生成缩略图方法                         ScriptManager.RegisterStartupScript(UpdatePanel1, typeof(UpdatePanel), "scriptname", "alert('文件上传成功!')", true);                        //this.RegisterStartupScript("hello", "<script>alert('文件上传成功!')</script>");                        Tools.AddLog("0", "上传照片成功信息成功！");                        imgPhoto.Visible = true;                        imgPhoto.ImageUrl = webFilePath_s;                        PhotoUrl = webFilePath_s;                    }                    catch (Exception ex)                    {                        Tools.AddLog("1", "上传照片成功信息失败！");                        throw new Exception("提示：文件上传失败，失败原因" + ex.Message);                    }                }                else                {                    this.RegisterStartupScript("hello", "<script>alert('图片已经存在，请重命名后上传!')</script>");                }            }            else            {                this.RegisterStartupScript("hello", "<script>alert('文件类型不符!')</script>");            }        }        else        {            ScriptManager.RegisterStartupScript(UpdatePanel1, typeof(UpdatePanel), "scriptname", "alert('请选择照片!')", true);        }    }        /**/    /// <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（物理路径）</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</param>     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();        }    }