How to get the thumbnail of a recorded video - win

问题:

I've used CaptureSource() to record a video like in this Topic How to record video in a camera app for Windows Phone, but I can't get the thumbnail of the recorded video.

回答1:

Here is the solution:

[...]

// Add eventhandlers for captureSource.
captureSource.CaptureFailed += new EventHandler<ExceptionRoutedEventArgs>(OnCaptureFailed);
captureSource.CaptureImageCompleted += captureSource_CaptureImageCompleted;

[...]

captureSource.Start();
captureSource.CaptureImageAsync();

[...]

void captureSource_CaptureImageCompleted(object sender, CaptureImageCompletedEventArgs e)
{
 using (IsolatedStorageFile isoStore = IsolatedStorageFile.GetUserStoreForApplication())
  {
    System.Windows.Media.Imaging.WriteableBitmap wb = e.Result;

     string fileName = "CameraMovie.jpg";
     if (isoStore.FileExists(fileName))
         isoStore.DeleteFile(fileName); 

     IsolatedStorageFileStream file = isoStore.CreateFile(fileName);

     System.Windows.Media.Imaging.Extensions.SaveJpeg(wb, file, wb.PixelWidth, wb.PixelHeight, 0, 85);

     file.Close();
 }
}

UPDATE : Give the user the possibility to take the thumbnail when he want

Add an Tap event to viewfinderRectangle

<Rectangle 
    x:Name="viewfinderRectangle"
    [...]
    Tap="viewfinderRectangle_Tap" />

Call captureSource.CaptureImageAsync(); in that Tap event

private void viewfinderRectangle_Tap(object sender, System.Windows.Input.GestureEventArgs e)
{
 captureSource.CaptureImageAsync();
}

回答2:

You can try this. If you are using AudioVideoCaptureDevice api. following events call after every frame capture. You can choose any frame that you need. As take first one.

private AudioVideoCaptureDevice VideoRecordingDevice;
VideoRecordingDevice.PreviewFrameAvailable += previewThumbnail;
bool DisablePreviewFrame = false;

private void previewThumbnail(ICameraCaptureDevice a, object b)
{
    if (!DisablePreviewFrame)
    {
        DisablePreviewFrame = true;
        int frameWidth = (int)VideoRecordingDevice.PreviewResolution.Width;
        int frameHeight = (int)VideoRecordingDevice.PreviewResolution.Height;
    }
    int[] buf = new int[frameWidth * frameHeight];
    VideoRecordingDevice.GetPreviewBufferArgb(buf);
    using (IsolatedStorageFile isoStoreFile = IsolatedStorageFile.GetUserStoreForApplication())
    {
        var fileName = "temp.jpg";

        if (isoStoreFile.FileExists(fileName))
            isoStoreFile.DeleteFile(fileName);
        using (IsolatedStorageFileStream isostream = isoStoreFile.CreateFile(fileName))
        {
            WriteableBitmap wb = new WriteableBitmap(frameWidth, frameWidth);
            Array.Copy(buf, wb.Pixels, buf.Length);
            wb.SaveJpeg(isostream, 120, 120, 0, 60);
            isostream.Close();
        }
    }
}