在 Asp Core 中将 IFormFile 转换为图像

Question

如果文件是图像，我需要调整文件上传的大小。

我写了调整大小的扩展：

 public static Image ResizeImage(this Image image, int width, int height)
    {
        var res = new Bitmap(width, height);
        using (var graphic = Graphics.FromImage(res))
        {
            graphic.InterpolationMode = InterpolationMode.HighQualityBicubic;
            graphic.SmoothingMode = SmoothingMode.HighQuality;
            graphic.PixelOffsetMode = PixelOffsetMode.HighQuality;
            graphic.CompositingQuality = CompositingQuality.HighQuality;
            graphic.DrawImage(image, 0, 0, width, height);
        }
        return res;
    }

这是 Upload Action :

 [HttpPost("UploadNewsPic"), DisableRequestSizeLimit]
    public IActionResult UploadNewsPic(IFormFile file)
    {
        if (file.IsImage())
        {

        }
        try
        {
            if (file.Length > 0)
            {
                string fileName = ContentDispositionHeaderValue.Parse(file.ContentDisposition).FileName.Trim('"');
                string fullPath = Path.Combine(_applicationRoot.UploadNewPath(), file.Name);
                using (var stream = new FileStream(fullPath, FileMode.Create))
                {
                    file.CopyTo(stream);
                }
            }
            return Ok();
        }
        catch (Exception e)
        {
            return BadRequest();
        }
    }

现在我的问题在这里 =>我的扩展只适用于Image文件类型，但此文件的类型是IFormFile. 我该如何转换IFormFile为Image类型？

Answer 1

您应该使用该Image.FromStream()方法将流作为图像读取：

public async Task<IActionResult> FileUpload(IFormFile file)
        {
            if (file == null || file.Length == 0)
            {
                return BadRequest();
            }

            using (var memoryStream = new MemoryStream())
            {
                await file.CopyToAsync(memoryStream);
                using (var img = Image.FromStream(memoryStream))
                {
                  // TODO: ResizeImage(img, 100, 100);
                }
            }
        }