aspnetcore两种上传图片(文件)的方式

aspnetcore上传图片也就是上传文件有两种方式，一种是通过form-data，一种是binary。

先介绍第一种form-data:

该方式需要显示指定一个IFormFile类型，该组件会动态通过打开一个windows窗口选择文件及图片。

postman演示如上，代码如下：

  [HttpPost]
        [AllowAnonymous]
        public IActionResult UploadFileByForm(IFormFile formFile)
        {
            var file = formFile;
            if (file == null)
                return JsonContent(new { status = "error" }.ToJson());

            string path = $"/Upload/{Guid.NewGuid().ToString("N")}/{file.FileName}";
            string physicPath = GetAbsolutePath($"~{path}");
            string dir = Path.GetDirectoryName(physicPath);
            if (!Directory.Exists(dir))
                Directory.CreateDirectory(dir);
            using (FileStream fs = new FileStream(physicPath, FileMode.Create))
            {
                file.CopyTo(fs);
            }

            string url = $"{_configuration["WebRootUrl"]}{path}";
            var res = new
            {
                name = file.FileName,
                status = "done",
                thumbUrl = url,
                url = url
            };

            return JsonContent(res.ToJson());
        }

第二种通过binary

同样是打开windows窗口选择文件，不过这里不需要参数显式指定IFormFile

看代码就明白了,这里通过请求上下文的body来读取字节流，如果有提示不能同步读取流的话，需要指定 services.Configure<KestrelServerOptions>(x => x.AllowSynchronousIO = true)；现在都不用iis，所以不介绍了。

 /// <summary>
        /// 上传图片 binary模式
        /// </summary>
        /// <returns></returns>
        [HttpPost]
        [AllowAnonymous]
        public IActionResult UploadImage()
        {
            var request = HttpContext.Request;
            var stream = new BinaryReader(request.Body);
            var body = stream.ReadBytes(1024*1024*5);
            return File(body, @"image/jpeg");

        }

aspnetcore7提供了如下的方式，通过指定本地文件绝对地址来读取字节流，应该算是第二种方式吧。

代码如下：参考：ASP.NET Core 7.0 的新增功能 | Microsoft Learn 需要引入包SixLabors.ImageSharp、SixLabors.ImageSharp.Formats.Jpeg

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Formats.Jpeg;
using SixLabors.ImageSharp.Processing;

var builder = WebApplication.CreateBuilder(args);

var app = builder.Build();

app.MapGet("/process-image/{strImage}", (string strImage, HttpContext http, CancellationToken token) =>
{
    http.Response.Headers.CacheControl = $"public,max-age={TimeSpan.FromHours(24).TotalSeconds}";
    return Results.Stream(stream => ResizeImageAsync(strImage, stream, token), "image/jpeg");
});

async Task ResizeImageAsync(string strImage, Stream stream, CancellationToken token)
{
    var strPath = $"wwwroot/img/{strImage}";
    using var image = await Image.LoadAsync(strPath, token);
    int width = image.Width / 2;
    int height = image.Height / 2;
    image.Mutate(x =>x.Resize(width, height));
    await image.SaveAsync(stream, JpegFormat.Instance, cancellationToken: token);
}