渐进式Jpg图片

网速比较慢的时候，会出现图片的空白，为了提升用户体验，可以先加载一个缩略图，然后加载一个渐进式图片(从模糊到清晰)；实现中暂时只放出来图片byte[]的转换，其实可以实现stream,bitmap等的转换，不再列举；

ps:需要借助Magick.NET

        /// <summary>
        /// 转换Jpg渐进式
        /// </summary>
        /// <param name="data">图片数据</param>
        /// <returns></returns>
        public byte[] ConvertProgressive(byte[] data)
        {
            byte[] resData = null;
            using (MemoryStream mStream = new MemoryStream())
            {
                using (MagickImage image = new MagickImage(data))
                {
                    image.Format = MagickFormat.Pjpeg;
                    image.Write(mStream);
                }
                resData = mStream.ToArray();
            }
            return resData;
        }

        /// <summary>
        /// 固定宽度等比缩放图片
        /// </summary>
        /// <param name="data"></param>
        /// <param name="width"></param>
        /// <returns></returns>
        public byte[] ScaleImageByWith(byte[] data, int width)
        {
            byte[] resData = null;
            using (MagickImage image = new MagickImage(data))
            {
                var imageSmall = image.Clone();
                imageSmall.Scale(width, image.Height * width / image.Width);
                using (MemoryStream mStream = new MemoryStream())
                {
                    imageSmall.Write(mStream);
                    resData = ConvertProgressive(mStream.ToArray()) ;
                }
            }
            return resData;
        }