我目前在一个项目中,我正在从IP摄像机接收实时视频流作为MediaPlayer对象。最终目标是能够使用Windows.Media.OCR每秒钟左右从框架中提取文本,为此,我需要一个SoftwareBitmap。

从Microsoft UWP文档看来,可以使用CopyFrameToVideoSurface(CanvasBitmap)方法从MediaPlayer对象获取帧。我可以从SoftwareBitmap创建CanvasBitmap,但是我没有找到一种无需保存文件就可以从CanvasBitmap创建SoftwareBitmap的方法(我试图避免这种情况,不需要保留图像)。我希望我缺少一些简单的东西,有没有办法从MediaPlayer对象获取SoftwareBitmap?

我一直在引用this example在帧服务器模式下使用MediaPlayer。我不需要显示图像,因此,如果可能的话,最好避免使用CanvasBitmap。

媒体播放器

private async Task GetStream()
{
    mediaPlayer = new MediaPlayer()
    {
        Source = MediaSource.CreateFromStream(placeholder, "video")
    };

    mediaPlayer.VideoFrameAvailable += VideoFrameAvailable;
    mediaPlayer.IsVideoFrameServerEnabled = true;
    mediaPlayer.Play();
}

private async void VideoFrameAvailable(MediaPlayer sender, object args)
{
    // Get frame from media player, create SoftwareBitmap
    await ExtractText(softwareBitmapImg);
}


我提供的OCR部分的代码相对简单,当我提供SoftwareBitmap时,它就像一个魅力。

光学字符识别

private async Task ExtractText()
{
    Language ocrLanguage = new Language("en-us");
    OcrEngine ocrEngine = OcrEngine.TryCreateFromLanguage(ocrLanguage);

    var ocrResult = await ocrEngine.RecognizeAsync(bitmap);
    String text = ocrResult.Text;
}

最佳答案

CanvasBitmap实现IDirect3DSurface接口,只要调用VideoFrameAvailable处理程序,就使用CopyFrameToVideoSurface方法将帧的内容复制到IDirect3DSurface。当调用CopyFrameToVideoSurface时,我们需要CanvasBitmap对象将当前帧从MediaPlayer复制到CanvasBitmap中,但是您无需显示图像。

private async void mediaPlayer_VideoFrameAvailable(MediaPlayer sender, object args)
{
    CanvasDevice canvasDevice = CanvasDevice.GetSharedDevice();
    await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, async () =>
    {
        SoftwareBitmap softwareBitmapImg;
        SoftwareBitmap frameServerDest = new SoftwareBitmap(BitmapPixelFormat.Rgba8, 100, 100, BitmapAlphaMode.Premultiplied);

        using (CanvasBitmap canvasBitmap = CanvasBitmap.CreateFromSoftwareBitmap(canvasDevice, frameServerDest))
        {
            sender.CopyFrameToVideoSurface(canvasBitmap);

            softwareBitmapImg = await SoftwareBitmap.CreateCopyFromSurfaceAsync(canvasBitmap);

        }
        await ExtractText(softwareBitmapImg);
    });
}

10-08 04:54