如何在UWP中使用MediaElement拍摄快照

Question

我有一个UWP项目想在播放视频时从Mediaelement拍摄快照。

有没有人知道任何有用的链接或如何处理这项任务？

Answer 1

根据您的要求，您可以通过Custom video effects实现这一目标。因为您可以使用ProcessFrame方法获得每帧。您可以使用静态属性来存储当前帧并将其传递给图像控件。以下是RExampleVidoEffect类。

public sealed class RExampleVidoEffect : IBasicVideoEffect
{

    private static SoftwareBitmap Snap;
    public void SetEncodingProperties(VideoEncodingProperties encodingProperties, IDirect3DDevice device)
    {

    }

    public void ProcessFrame(ProcessVideoFrameContext context)
    {
        var inputFrameBitmap = context.InputFrame.SoftwareBitmap;
        Snap = inputFrameBitmap;
    }

    public static SoftwareBitmap GetSnapShot()
    {
        return Snap;
    }
    public void Close(MediaEffectClosedReason reason)
    {

    }

    public void DiscardQueuedFrames()
    {

    }

    public bool IsReadOnly
    {
        get
        {
            return true;
        }
    }

    public IReadOnlyList<VideoEncodingProperties> SupportedEncodingProperties
    {
        get { return new List<VideoEncodingProperties>(); }
    }
    public MediaMemoryTypes SupportedMemoryTypes
    {
        get { return MediaMemoryTypes.Cpu; }
    }

    public bool TimeIndependent
    {
        get { return true; }
    }



    public void SetProperties(IPropertySet configuration)
    {

    }
}

<强>用法

private async void VideoPlayer_Loaded(object sender, RoutedEventArgs e)
{
    var videoFile = await Package.Current.InstalledLocation.GetFileAsync("big_buck_bunny.mp4");  
    MediaClip clip = await MediaClip.CreateFromFileAsync(videoFile);

    var videoEffectDefinition = new VideoEffectDefinition(typeof(RExampleVidoEffect).FullName);
    clip.VideoEffectDefinitions.Add(videoEffectDefinition);

    MediaComposition compositor = new MediaComposition();
    compositor.Clips.Add(clip);

    this.VideoPlayer.SetMediaStreamSource(compositor.GenerateMediaStreamSource());

}


private async void Button_Click(object sender, RoutedEventArgs e)
{
    var bitmap = RExampleVidoEffect.GetSnapShot();

    if (bitmap.BitmapPixelFormat != BitmapPixelFormat.Bgra8 ||
         bitmap.BitmapAlphaMode == BitmapAlphaMode.Straight)
    {
        bitmap = SoftwareBitmap.Convert(bitmap, BitmapPixelFormat.Bgra8, BitmapAlphaMode.Premultiplied);
    }
    var source = new SoftwareBitmapSource();
    await source.SetBitmapAsync(bitmap);
    img.Source = source;
}

<强>效果