C#无损高质量压缩图片代码

本文实例为大家分享了C#无损高质量压缩图片的具体代码，供大家参考，具体内容如下

/// 无损压缩图片  
/// <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"></param>  
/// <param name="flag">压缩质量(数字越小压缩率越高) 1-100</param>  
/// <returns></returns>  

public static bool GetPicThumbnail(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.Width * dWidth))
   {
     sW = dWidth;
     sH = (dWidth * tem_size.Height) / tem_size.Width;
   }
   else
   {
     sH = dHeight;
     sW = (tem_size.Width * dHeight) / tem_size.Height;
   }
 }
 else
 {
   sW = tem_size.Width;
   sH = tem_size.Height;
 }

Bitmap ob = new Bitmap(dWidth, dHeight);
 Graphics g = Graphics.FromImage(ob);

g.Clear(Color.WhiteSmoke);
 g.CompositingQuality = CompositingQuality.HighQuality;
 g.SmoothingMode = SmoothingMode.HighQuality;
 g.InterpolationMode = InterpolationMode.HighQualityBicubic;

g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);

g.Dispose();
 //以下代码为保存图片时，设置压缩质量  
 EncoderParameters ep = new EncoderParameters();
 long[] qy = new long[1];
 qy[0] = flag;//设置压缩的比例1-100  
 EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
 ep.Param[0] = eParam;
 try
 {
   ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
   ImageCodecInfo jpegICIinfo = null;
   for (int x = 0; x < arrayICI.Length; x++)
   {
     if (arrayICI[x].FormatDescription.Equals("JPEG"))
     {
       jpegICIinfo = arrayICI[x];
       break;
     }
   }
   if (jpegICIinfo != null)
   {
     ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径  
   }
   else
   {
     ob.Save(dFile, tFormat);
   }
   return true;
 }
 catch
 {
   return false;
 }
 finally
 {
   iSource.Dispose();
   ob.Dispose();
 }
}