.Net上传图片按比例自动缩小或放大

以下为引用的内容：
//// <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;
}
}