C#图片高效无损压缩 绝对有效

这两天忙于将扫描仪扫描出来的文件缩放图片分辨率和大小，开始尝试修改扫描仪设置的参数，结果发现没有办法修改扫描仪参数，最后尝试将扫描后的图片进行代码处理，下面是写的是关于图片进行无损压缩的代码。
 
/// <summary>  
         /// 无损压缩图片  
         /// </summary>  
         /// <param name="sFile">原图片</param>  
         /// <param name="dFile">压缩后保存位置</param>  
         /// <param name="dHeight">高度</param>  
         /// <param name="dWidth">宽度</param>  
         /// <param name="flag">压缩质量 1-100</param>  
         /// <returns></returns>  
         public static bool CompressImage(string sFile, string dFile, int dHeight, int dWidth, int flag)  
         {  
   
             System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile);  
             ImageFormat tFormat = iSource.RawFormat;  
             int sW = 0, sH = 0;  
             //按比例缩放  
             Size tem_size = new Size(iSource.Width, iSource.Height);  
   
             if (tem_size.Width > dHeight ||tem_size.Width > dWidth)   
             {  
                 if ((tem_size.Width * dHeight) > (tem_size.Height * dWidth))  
                 {  
                     sW = dWidth;  
                     sH = (dWidth * tem_size.Height) / tem_size.Width;  
                 }  
                 else 
                 {