C#图片无损压缩

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/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


/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