Asynchronous image processing in C#

Question

I need to operate on bitmap pixels asynchronously. There is Bitmap and WriteableBitmap. I need something like:

public async Task<Bitmap> ProcessBitmap(Bitmap bitmap)
{
   // operate on bitmap asynchronously
   return newBitmap;
}

I wanted to use WriteableBitmap and convert it to stream and use stream async methods but PixelBuffer property seems unavailable in both WPF and WinForms. How should I do this? I could also use Parallel.For in some scenarios but how would I get result then?

So you can do something like var files = new [] { "c:\file1.bmp", "c:\file2.bmp" }; var tasks = files.Select(x => ProcessBitmap(x)); await Task.WhenAll(tasks). The WhenAll will wait for all tasks started to execute (here is you parallelism. — Callum Linington
– Callum Linington, Commented Jul 18, 2016 at 14:47
Look into using the Parallel library in .NET. It will allow you to utilize all the cores of the CPU to do image processing. msdn.microsoft.com/en-us/library/dd460720(v=vs.110).aspx — Jon
– Jon, Commented Jul 18, 2016 at 14:49

Luaan · Accepted Answer · 2016-07-18 14:45:52Z

5

Image processing is almost entirely CPU-bound. There's no asynchronous I/O you could exploit.

Do not confuse I/O-bound code (where async works great) with CPU-bound code (where async doesn't give you any benefits, really).

answered Jul 18, 2016 at 14:45

Luaan

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dymanoid Over a year ago

Probably, the question point is that the processing should run on a different thread not to block the UI thread. So asynchronously should be read as on a parallel thread, I suppose.

Alex Zhmerik · Accepted Answer · 2016-07-18 16:02:44Z

1

With Task.Run you can send the CPU-intensive work to ThreadPool, so your thread is free to do other work while awaiting:

public async void Button_Click(object sender, RoutedEventArgs e) {
    ...
    var processedBitmap = await ProcessBitmap(bitmap);
    ...
}

public async Task<Bitmap> ProcessBitmap(Bitmap bitmap) {
    //on bitmap asynchronously
    await Task.Run(() => {
        return DoActualBitmapProcessing(bitmap);
    }
}

answered Jul 18, 2016 at 16:02

Alex Zhmerik

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KansaiRobot Over a year ago

Where is the return statement for the ProcessBitmap function?

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