C# 图片无损压缩

        /// <summary>
        /// 图像缩略图处理
        /// </summary>
        /// <param name="bytes">图像源数据</param>
        /// <param name="compression">压缩质量 1-100</param>
        /// <param name="thumbWidth">缩略图的宽</param>
        /// <param name="thumbHeight">缩略图的高</param>
        /// <returns></returns>
        public static byte[] ConvertToThumbnail(byte[] bytes, int compression = , int thumbWidth = , int thumbHeight = )
        {
            byte[] bs = null;

            try
            {
                if (bytes != null)
                {
                    using (MemoryStream ms = new MemoryStream(bytes))
                    {
                        using (Bitmap srcimg = new Bitmap(ms))
                        {
                            if (thumbWidth ==  && thumbHeight == )
                            {
                                thumbWidth = srcimg.Width;
                                thumbHeight = srcimg.Height;
                            }
                            using (Bitmap dstimg = new Bitmap(thumbWidth, thumbHeight))//图片压缩质量
                            {
                                //从Bitmap创建一个System.Drawing.Graphics对象，用来绘制高质量的缩小图。
                                using (Graphics gr = Graphics.FromImage(dstimg))
                                {
                                    //把原始图像绘制成上面所设置宽高的缩小图
                                    Rectangle rectDestination = new Rectangle(, , thumbWidth, thumbHeight);
                                    gr.Clear(Color.WhiteSmoke);
                                    gr.CompositingQuality = CompositingQuality.HighQuality;
                                    gr.SmoothingMode = SmoothingMode.HighQuality;
                                    gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
                                    gr.DrawImage(srcimg, rectDestination, , , srcimg.Width, srcimg.Height, GraphicsUnit.Pixel);

                                    EncoderParameters ep = new EncoderParameters();
                                    ep.Param[] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, compression);//设置压缩的比例1-100
                                    ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
                                    ImageCodecInfo jpegICIinfo = arrayICI.FirstOrDefault(t => t.FormatID == System.Drawing.Imaging.ImageFormat.Png.Guid);
                                    using (MemoryStream dstms = new MemoryStream())
                                    {
                                        if (jpegICIinfo != null)
                                        {
                                            dstimg.Save(dstms, jpegICIinfo, ep);
                                        }
                                        else
                                        {
                                            dstimg.Save(dstms, System.Drawing.Imaging.ImageFormat.Png);//保存到内存里
                                        }
                                        bs = new Byte[dstms.Length];
                                        dstms.Position = ;
                                        dstms.Read(bs, , bs.Length);
                                    }
                                }
                            }
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                LogManager.DefaultLogger.Error(LogConvert.ParseWebEx(ex), string.Concat("ConvertToThumbnail error.", thumbWidth, " ", thumbHeight));
            }
            return bs;
        }