.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;
            }
        }