C#图片无损压缩

//引用命名空间
using System.Drawing.Imaging;
using System.Drawing;
using System.Drawing.Drawing2D;

#region GetPicThumbnail

    /// <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"></param>

    /// <param name="flag">压缩质量 1-100</param>

    /// <returns></returns>



    public 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) //将**改成c#中的或者操作符号

        {



            if ((tem_size.Width * dHeight) > (tem_size.Height * 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();



        }







    }

    #endregion