/// <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);
}