无损压缩图片

//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