public async Task StartPreviewAsync(QR_Code_Scanner.Business.ComboboxItem comboboxItem)
{
FrameSourceInformation frameSourceInformation = new FrameSourceInformation();
try
{
mediaCapture = new MediaCapture();
var settings = new MediaCaptureInitializationSettings()
{
StreamingCaptureMode = StreamingCaptureMode.Video
};
if (comboboxItem != null)
{
settings.VideoDeviceId = comboboxItem.ID;
frameSourceInformation = comboboxItem.MediaFrameSourceInformation;
}
else
{
if (availableColorCameras == null)
{
var frameSourceInformations = await GetFrameSourceInformationAsync();
frameSourceInformation = frameSourceInformations.First();
availableColorCameras = await GetFrameSourceGroupsAsync(frameSourceInformation);
}
settings.VideoDeviceId = availableColorCameras.First().Id;
}
qrAnalyzerCancellationTokenSource = new CancellationTokenSource();
try
{
await mediaCapture.InitializeAsync(settings);
}
catch (Exception ex)
{
MessageManager.ShowMessageToUserAsync("Tried to initialize a color camera but failed to do so.");
}
List <VideoEncodingProperties> availableResolutions = null;
try
{
availableResolutions = mediaCapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview).Where(properties => properties is VideoEncodingProperties).Select(properties => (VideoEncodingProperties)properties).ToList();
}
catch (Exception ex)
{
MessageManager.ShowMessageToUserAsync("No resolutions could be detected, trying default mode.");
}
VideoEncodingProperties bestVideoResolution = this.findBestResolution(availableResolutions);
if (bestVideoResolution != null)
{
await mediaCapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.VideoPreview, bestVideoResolution);
}
displayRequest.RequestActive();
}
catch (UnauthorizedAccessException)
{
// This will be thrown if the user denied access to the camera in privacy settings
MessageManager.ShowMessageToUserAsync("The app was denied access to the camera");
return;
}
try
{
this.ScanForQRcodes = true;
previewWindowElement.Source = mediaCapture;
await mediaCapture.StartPreviewAsync();
isPreviewing = true;
var imgProp = new ImageEncodingProperties
{
Subtype = "BMP",
Width = (uint)imgCaptureWidth,
Height = (uint)imgCaptureHeight
};
var bcReader = new BarcodeReader();
var qrCaptureInterval = 200;
var torch = mediaCapture.VideoDeviceController.TorchControl;
var exposureCompensationControl = mediaCapture.VideoDeviceController.ExposureCompensationControl;
if (torch.Supported)
{
torch.Enabled = false;
}
//if (exposureCompensationControl.Supported) {
// var maxSupported = exposureCompensationControl.Max;
// var minSupported = exposureCompensationControl.Min;
// var middleExposure = (maxSupported + minSupported) / 2;
// var quarterExposure = (middleExposure + minSupported) / 2;
// await exposureCompensationControl.SetValueAsync(quarterExposure);
//}
// Get information about the preview
var previewProperties = mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview) as VideoEncodingProperties;
while (!qrAnalyzerCancellationTokenSource.IsCancellationRequested && qrAnalyzerCancellationTokenSource != null && qrAnalyzerCancellationTokenSource.Token != null)
{
//try capture qr code here
if (ScanForQRcodes)
{
VideoFrame videoFrameFormatPlaceholder = new VideoFrame(BitmapPixelFormat.Bgra8, (int)previewProperties.Width, (int)previewProperties.Height);
await mediaCapture.GetPreviewFrameAsync(videoFrameFormatPlaceholder);
await findQRinImageAsync(bcReader, videoFrameFormatPlaceholder);
videoFrameFormatPlaceholder.Dispose();
videoFrameFormatPlaceholder = null;
}
//await Task.Delay(qrCaptureInterval, qrAnalyzerCancellationTokenSource.Token);
var delayTask = Task.Delay(qrCaptureInterval, qrAnalyzerCancellationTokenSource.Token);
var continuationTask = delayTask.ContinueWith(task => { });
await continuationTask;
}
}
catch (System.IO.FileLoadException)
{
mediaCapture.CaptureDeviceExclusiveControlStatusChanged += mediaCapture_CaptureDeviceExclusiveControlStatusChanged;
}
catch (System.ObjectDisposedException)
{
Debug.WriteLine("object was disposed");
}
catch (Exception)
{
Debug.WriteLine("another exception occurred.");
}
}
public async Task <IEnumerable <DeviceInformation> > GetFrameSourceGroupsAsync(FrameSourceInformation frameSourceInformation)
{
try
{
var availableColorCamera = frameSourceInformation.MediaFrameSourceGroup.SourceInfos.Select(y => y.DeviceInformation).Distinct();
return(availableColorCamera);
}
catch (Exception ex)
{
MessageManager.ShowMessageToUserAsync("Tried to find all available color cameras but failed to do so.");
return(null);
}
}
public ComboboxItem(string name, string id, FrameSourceInformation mediaFrameSourceInformation)
{
Name = name; ID = id; MediaFrameSourceInformation = mediaFrameSourceInformation;
}
