如何将调整大小的图像保存到 ASP.NET 核心应用程序中的 Azure Blob 存储？

Question

I'm using the ImageSharp library to rescale my images before they are uploaded to Azure, the application hangs with no errors when it reaches the UploadBlob action and I think it's the stream causing it. When the image is uploaded the information is gathered from the image stream, I create an empty MemoryStream , resize the image using ImageSharp , stuff the MemoryStream with my newly scaled image and try to upload that MemoryStream to Azure and I don't think it likes it as that is where it hangs.

Is MemoryStream the correct thing to use in this instance or is it something else?

CarController.cs

[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(Car car)
{
    // Define the cancellation token.
    CancellationTokenSource source = new CancellationTokenSource();
    CancellationToken token = source.Token;

    if (ModelState.IsValid)
    {
        //Access the car record
        _carService.InsertCar(car);

        //Get the newly created ID
        int id = car.Id;

        //Give it a name with some virtual directories within the container         
        string fileName = "car/" + id + "/car-image.jpg";
        string strContainerName = "uploads";

        //I create a memory stream ready for the rescaled image, not sure this is right.
        Stream outStream = new MemoryStream();

        //Access my storage account
        BlobServiceClient blobServiceClient = new BlobServiceClient(accessKey);
        BlobContainerClient containerClient = blobServiceClient.GetBlobContainerClient(strContainerName);

        //Open the image read stream
        var carImage = car.ImageFile.OpenReadStream();

        //Rescale the image, save as jpeg.
        using (Image image = Image.Load(carImage))
        {
            int width = 250;
            int height = 0;
            image.Mutate(x => x.Resize(width, height));                    
            image.SaveAsJpeg(outStream);
        }

        var blobs = containerClient.UploadBlob(fileName, outStream);
        return RedirectToAction(nameof(Index));
    }            
    return View(car);
}

Answer 1

It's not got anything to do with the ImageSharp library.

You need to reset your outStream position after saving. BlobContainerClient is trying to read from the end of the stream.