ASP.NET生成缩略图及水印图片

代码如下：

using System.IO;
using System.Drawing.Imaging;

private void Button1_ServerClick(object sender, System.EventArgse)
{
 Graphics g=null;
 System.Drawing.Image upimage=null;
 System.Drawing.Image thumimg=null;
 System.Drawing.Image simage=null;
 Bitmap outputfile=null;
 try
 {
  string extension = Path.GetExtension(File1.PostedFile.FileName).ToUpper();
  string filename = DateTime.Now.ToString("yyyyMMddhhmmss");
  string smallpath = Server.MapPath(".")+"/smallimg/";
  string bigpath = Server.MapPath(".")+"/bigimg/";
  int width,height,newwidth,newheight;

  System.Drawing.Image.GetThumbnailImageAbort callb =new  System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback); 

  if(!Directory.Exists(smallpath))
   Directory.CreateDirectory(smallpath);
  if(!Directory.Exists(bigpath))
   Directory.CreateDirectory(bigpath);

  Stream upimgfile = File1.PostedFile.InputStream;
  string simagefile = Server.MapPath("a8logo.jpg"); //要加水印的文件
  simage=System.Drawing.Image.FromFile(simagefile);
  upimage= System.Drawing.Image.FromStream(upimgfile); //上传的图片

  width = upimage.Width;
  height = upimage.Height;

  if(width>height)
  {
   newwidth=200;
   newheight =(int)((double)height/(double)width * (double)newwidth);
  }
  else
  {
   newheight=200;
   newwidth=(int)((double)width/(double)height * (double)newheight); 
  } 

  thumimg = upimage.GetThumbnailImage(newwidth,newheight,callb,IntPtr.Zero);
  outputfile=new Bitmap(upimage);
  g=Graphics.FromImage(outputfile);
  g.DrawImage(simage,new Rectangle(upimage.Width-simage.Width,upimage.Heightsimage.Height,upimage.Width,upimage.Height),0,0,upimage.Width,upimage.Height,GraphicsUnit.Pixel);

  string newpath = bigpath + filename + extension; //原始图路径
  string thumpath = smallpath + filename + extension; //缩略图路径
  outputfile.Save(newpath);
  thumimg.Save(thumpath);
  outputfile.Dispose();

 }
 catch(Exception ex)
 {
  throw ex;
 }
 finally
 {
  if(g!=null)
  g.Dispose();
  if(thumimg!=null)
  thumimg.Dispose();
  if(upimage!=null)
  upimage.Dispose();
  if(simage!=null)
  simage.Dispose();
 }
}

public bool ThumbnailCallback()
{
 return false;
}