如何在C#中实现图片缩放

 /// <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;     }    }      /// <summary>    /// 按比例缩小图片，自动计算高度    /// </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="intWidth">缩小至宽度</param>    public void SmallPic(string strOldPic, string strNewPic, int intWidth)    {       System.Drawing.Bitmap objPic,objNewPic;     try     {      objPic = new System.Drawing.Bitmap(strOldPic);      int intHeight=(intWidth / objPic.Width) * objPic.Height;      objNewPic=new System.Drawing.Bitmap(objPic,intWidth,intHeight);      objNewPic.Save(strNewPic);       }     catch(Exception exp){throw exp;}     finally     {      objPic=null;      objNewPic=null;     }    }        /// <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 SmallPic(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;     }    }