.Net实现上传图片按比例自动缩小或放大的方法

//// <summary>
/// 按比例缩小图片，自动计算宽度
/// </summary>
/// <param name="stroldpic">源图文件名(包括路径)</param>
/// <param name="strnewpic">缩小后保存为文件名(包括路径)</param>
/// <param name="intheight">缩小至高度</param>
public void smallpicwidth(string stroldpic, string strnewpic, int intheight)
{
  system.drawing.bitmap objpic, objnewpic;
  try
  {
 objpic = new system.drawing.bitmap(stroldpic);
 int intwidth = (intheight / objpic.height) * objpic.width;
 objnewpic = new system.drawing.bitmap(objpic, intwidth, intheight);
 objnewpic.save(strnewpic);
  }
  catch (exception exp) { throw exp; }
  finally
  {
 objpic = null;
 objnewpic = null;
  }
}
/**//// <summary>
/// 缩小图片
/// </summary>
/// <param name="stroldpic">源图文件名(包括路径)</param>
/// <param name="strnewpic">缩小后保存为文件名(包括路径)</param>
/// <param name="intwidth">缩小至宽度</param>
/// <param name="intheight">缩小至高度</param>
public void smallpic(string stroldpic, string strnewpic, int intwidth, int intheight)
{
  system.drawing.bitmap objpic, objnewpic;
  try
  {
 objpic = new system.drawing.bitmap(stroldpic);
 objnewpic = new system.drawing.bitmap(objpic, intwidth, intheight);
 objnewpic.save(strnewpic);
  }
  catch (exception exp)
 { throw exp; }
  finally
  {
 objpic = null;
 objnewpic = null;
  }
}