/// <summary>Invoke
        /// </summary>
        public async Task Invoke(HttpContext context)
        {
            var path = context.Request.Path;

            // hand to next middleware if we are not dealing with an image
            if (context.Request.Query.Count == 0 || !IsImagePath(path))
            {
                await _next.Invoke(context);

                return;
            }
            //图片需要的参数
            var resizeParameter = GetResizeParameter(context.Request.Query);

            //无参数,不缩放
            if (!resizeParameter.HasParams())
            {
                await _next.Invoke(context);

                return;
            }

            //图片路径
            var imagePath = Path.Combine(
                _env.WebRootPath,
                path.Value.Replace('/', Path.DirectorySeparatorChar).TrimStart(Path.DirectorySeparatorChar));

            //图片不存在
            if (!File.Exists(imagePath))
            {
                await _next.Invoke(context);

                return;
            }
            //图片最后修改时间
            var lastWriteTimeUtc = File.GetLastWriteTimeUtc(imagePath);

            //图片二进制
            byte[] imageBytes = await _imageResizeService.GetImageData(imagePath, resizeParameter, lastWriteTimeUtc);

            //无法调整图片,那么就直接返回下一个
            if (imageBytes == null || imageBytes.Length <= 0)
            {
                await _next.Invoke(context);

                return;
            }

            //contentType
            context.Response.ContentType   = MimeTypeNameUtil.GetMimeName(resizeParameter.Format);
            context.Response.ContentLength = imageBytes.Length;
            await context.Response.Body.WriteAsync(imageBytes.ToArray(), 0, imageBytes.Length);
        }
        public void GetMimeName_Test()
        {
            var actual = MimeTypeNameUtil.GetMimeName("Xls");

            Assert.Equal("application/vnd.ms-excel", actual);
        }