Question

I’m trying to get the compressed JPEG data out of the Camera Capture UI, but I’m getting tripped up around IInputBuffer. Here’s what I’ve got:

private async void OnWebcamButton(object sender, RoutedEventArgs e)
{
    var captureUi = new CameraCaptureUI();
    var result = await captureUi.CaptureFileAsync(CameraCaptureUIMode.Photo);
    var file = await result.OpenForReadAsync();
    var reader = new DataReader(file);

    byte[] data = new byte[reader.UnconsumedBufferLength];
    await reader.LoadAsync(reader.UnconsumedBufferLength);
    reader.ReadBytes(data);

    // XXX: This is always zero
    Debug.Text = String.Format("Buffer is {0} bytes", data.Length);
}

Any ideas what I’m doing wrong?

Answer 1

I don’t think you need a DataReader here at all. Try this:

using System.Runtime.InteropServices.WindowsRuntime; // for AsBuffer()
...
var file = await captureUi.CaptureFileAsync(CameraCaptureUIMode.Photo);
var stream = await result.OpenForReadAsync();
byte[] data = new byte[file.Size];
await stream.ReadAsync(data.AsBuffer(), (uint)data.Length, InputStreamOptions.None);

Alternatively, you can use AsStream() extension method (from System.IO.WindowsRuntimeStreamExtensons) to wrap WinRT IInputStream as System.IO.Stream, and then use normal .NET techniques.