#region 上传图片生成缩略图

     /// <summary>

     /// 上传图片

     /// </summary>

     /// <param name="sender"></param>

     /// <param name="e"></param>

     public void btnUpload_Click(object sender, EventArgs e)

     {

         //检查上传文件的格式是否有效

         if (this.fudPhoto.PostedFile.ContentType.ToLower().IndexOf("image") < )

         {

             Response.Write("<script>alert('上传图片格式无效!');window.location.href='LES_ApplyTopActivityAdd.aspx';</script>");

             return;

         }

         string FileNmae;

         string FileNameS;

         string name = fudPhoto.PostedFile.FileName;//客户端文件路径

         FileInfo file = new FileInfo(name);

         string fileName = file.Name;

         string ExtName = getFileExt(fileName).ToUpper();

         //生成原图

         Byte[] oFileByte = new byte[this.fudPhoto.PostedFile.ContentLength];

         System.IO.Stream oStream = this.fudPhoto.PostedFile.InputStream;

         System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);

         int towidth = ;//设置缩略图初始高度

         int toheight = ;//设置缩略图初始宽度

         int x = ;

         int y = ;

         int ow = oImage.Width;

         int oh = oImage.Height;

         if (ow ==  && ow == )

         {

             //按比例计算出缩略图的宽度和高度 

             if (((double)oImage.Width / (double)oImage.Height) > ((double)towidth / (double)toheight))

             {

                 oh = oImage.Height;

                 ow = oImage.Height * towidth / toheight;

                 y = ;

                 x = (oImage.Width - ow) / ;

             }

             else

             {

                 ow = oImage.Width;

                 oh = oImage.Width * toheight / towidth;

                 x = ;

                 y = (oImage.Height - oh) / ;

             }

             //生成缩略原图

             Bitmap tImage = new Bitmap(towidth, toheight);

             Graphics g = Graphics.FromImage(tImage);

             g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //设置高质量插值法

             g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置高质量,低速度呈现平滑程度

             g.Clear(Color.Transparent); //清空画布并以透明背景色填充

             g.DrawImage(oImage, new Rectangle(, , towidth, toheight), new Rectangle(, , ow, oh), GraphicsUnit.Pixel);

             FileNmae = DateTime.Now.ToShortDateString().Replace("-", "") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + "." + ExtName; //保存原图的物理路径

             string oFullName = Server.MapPath("/uploadfiles//" + FileNmae);

             FileNameS = FileNmae + "-S" + ".JPG"; //保存缩略图的物理路径

             string tFullName = Server.MapPath("/uploadfiles//" + FileNameS);

             try

             {

                 //以JPG格式保存图片

                 oImage.Save(oFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

                 tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg);

                 //lbMessage.Text = "提示：文件”" + FileNmae + "“成功上传，并生成”" + FileNameS + "“缩略图，文件类型为：" +

                 //     fudPhoto.PostedFile.ContentType + "，文件大小为：" + fudPhoto.PostedFile.ContentLength + "B";

                 lbMessage.Text = "提示：文件成功上传，并生成”" + FileNameS + "“缩略图！";

                 string PIC = FileNmae;

                 ViewState["pic"] = PIC;

             }

             catch (Exception ex)

             {

                 throw ex;

             }

             finally

             {

                 //释放资源

                 oImage.Dispose();

                 g.Dispose();

                 tImage.Dispose();

             }

         }

         else

         {

             lbMessage.Text = "提示：图片的尺寸应该是640x640";

         }

     }

     private string getFileExt(string fileName)

     {

         if (fileName.IndexOf(".") == -)

             return "";

         string[] temp = fileName.Split('.');

         return temp[temp.Length - ].ToLower();

     }

     #endregion

 }
如图效果图：