在ASP.NET中实现上传图片，并按比例生成缩略图

private   void  btnUploadPicture_Click( object  sender, System.EventArgs e) ... {   //检查上传文件的格式是否有效   if(this.UploadFile.PostedFile.ContentType.ToLower().IndexOf("image") < 0)   ...{    Response.Write("上传图片格式无效！");    return;   }   //生成原图   Byte[] oFileByte = new byte[this.UploadFile.PostedFile.ContentLength];   System.IO.Stream oStream = this.UploadFile.PostedFile.InputStream;   System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream);   int oWidth = oImage.Width; //原图宽度   int oHeight = oImage.Height; //原图高度   int tWidth = 100; //设置缩略图初始宽度   int tHeight = 100; //设置缩略图初始高度   //按比例计算出缩略图的宽度和高度   if(oWidth >= oHeight)   ...{    tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth)));   }   else   ...{    tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight)));   }   //生成缩略原图   Bitmap tImage = new Bitmap(tWidth,tHeight);   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(0,0,tWidth,tHeight),new Rectangle(0,0,oWidth,oHeight),GraphicsUnit.Pixel);   string oFullName = Server.MapPath(".") + "/" + "o" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存原图的物理路径   string tFullName = Server.MapPath(".") + "/" + "t" + DateTime.Now.ToShortDateString().Replace("-","") + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + DateTime.Now.Millisecond.ToString() + ".jpg"; //保存缩略图的物理路径   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);   }   catch(Exception ex)   ...{    throw ex;   }   finally   ...{    //释放资源    oImage.Dispose();    g.Dispose();    tImage.Dispose();   }}