Convert a RenderTargetBitmap to BitmapImage

Question

How can I convert a RenderTargetBitmap to BitmapImage in C# XAML, Windows 8.1?

I tried

// rendered is the RenderTargetBitmap 
BitmapImage img = new BitmapImage();
InMemoryRandomAccessStream randomAccessStream = new InMemoryRandomAccessStream();
await randomAccessStream.WriteAsync(await rendered.GetPixelsAsync());
randomAccessStream.Seek(0); 
await img.SetSourceAsync(randomAccessStream);

But it always gives error at

img.SetSourceAsync(randomAccessStream);

There are many ways in WPF but in WinRT? How can I do that ?

Thanks a lot!

Answer 1

this is the one that worked Sharing render to bitmap image in windows phone 8.1

turned out that i just can't fill the stream directly using

stream.WriteAsync(byteArray.AsBuffer());

you have to use bitmap encoder , final working code :

InMemoryRandomAccessStream stream = new InMemoryRandomAccessStream();
        var buffer = await rendered.GetPixelsAsync();
      //  await stream.ReadAsync(buffer, (uint)buffer.Length, InputStreamOptions.None);
        BitmapImage img = new BitmapImage();
        var encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, stream);
        encoder.SetPixelData(
            BitmapPixelFormat.Bgra8,
            BitmapAlphaMode.Straight,
            (uint)rendered.PixelWidth,
            (uint)rendered.PixelHeight,
            DisplayInformation.GetForCurrentView().LogicalDpi,
            DisplayInformation.GetForCurrentView().LogicalDpi,
            buffer.ToArray());
        await encoder.FlushAsync();
        await img.SetSourceAsync(stream);
        preview.Source = img;