保存指定品质的图片

        /// <summary>
        /// 保存图片
        /// </summary>
        /// <param name="srcImage">要保存的图片</param>
        /// <param name="quality">品质（1L~100L之间，数值越大品质越好）</param>
        /// <param name="filename">保存路径</param>
        public static void SaveImage(Image srcImage, long quality, string filename)
        {
            using (EncoderParameters encoderParams = new EncoderParameters(1))
            {
                encoderParams.Param[0] = new EncoderParameter(Encoder.Quality, quality);
                ImageCodecInfo encoder = null;
                string ext = Path.GetExtension(filename);
                if (string.IsNullOrEmpty(ext))
                {
                    ext = ".jpg";
                }
                //根据扩展名得到解码、编码器
                foreach (ImageCodecInfo codecInfo in ImageCodecInfo.GetImageEncoders())
                {
                    if (Regex.IsMatch(codecInfo.FilenameExtension, string.Format(@"(;|^)\*\{0}(;|$)", ext), RegexOptions.IgnoreCase))
                    {
                        encoder = codecInfo;
                        break;
                    }
                }
                Directory.CreateDirectory(Path.GetDirectoryName(filename));
                srcImage.Save(filename, encoder, encoderParams);
            }
        }