c#ピクチャ圧縮アルゴリズム

  #region     
        private static byte[] CompressionImage(Stream fileStream, long quality)
        {
            using (System.Drawing.Image img = System.Drawing.Image.FromStream(fileStream))
            {
                using (Bitmap bitmap = new Bitmap(img))
                {
                    ImageCodecInfo CodecInfo = GetEncoder(img.RawFormat);
                    System.Drawing.Imaging.Encoder myEncoder = System.Drawing.Imaging.Encoder.Quality;
                    EncoderParameters myEncoderParameters = new EncoderParameters(1);
                    EncoderParameter myEncoderParameter = new EncoderParameter(myEncoder, quality);
                    myEncoderParameters.Param[0] = myEncoderParameter;
                    using (MemoryStream ms = new MemoryStream())
                    {
                        bitmap.Save(ms, CodecInfo, myEncoderParameters);
                        myEncoderParameters.Dispose();
                        myEncoderParameter.Dispose();
                        return ms.ToArray();
                    }
                }
            }
        }

        private static ImageCodecInfo GetEncoder(ImageFormat format)
        {
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.FormatID == format.Guid)
                { return codec; }
            }
            return null;
        }
        #endregion