即使使用Dispatcher WPF，也必须在同一线程上创建DependencySource和DependencyObject。

Question

我正在编写一个C# WPF应用程序，我正在使用AForge库的视频流。我想部署的应用程序，因为一切工作在第一台PC。

比我部署它，并在其他PC上，我得到以下错误。

"Must create DependencySource on the same Thread as the DependencyObject even by using Dispatcher" "必须在与DependencyObject相同的线程上创建依赖源，即使使用Dispatcher"

这是源码，我在从WebCam获得的每一个新的Frame上调用它。

private void video_NewFrame(object sender, NewFrameEventArgs eventArgs)

{ if (StreamRunning) { try { using (var bitmap = (Bitmap)eventArgs.Frame.Clone()) {

                    Image = ToBitmapImage(bitmap);
                }
                Image.Freeze();
            }
            catch (Exception e)
            {
                UIMessages = "Error: NewFrame " + e.Message;
            }
        }

}

ToBitmapImage方法。

        private BitmapImage ToBitmapImage(Bitmap bitmap)
    {

        var start = 420;
        var end = 1920 - 2* 420;
        BitmapImage bi = new BitmapImage();
        bi.BeginInit();
        MemoryStream ms = new MemoryStream();
        Bitmap source = bitmap;
        Bitmap CroppedImage = source.Clone(new System.Drawing.Rectangle(start, 0, end, 1080), source.PixelFormat);          
        CroppedImage.Save(ms, ImageFormat.Bmp);

        ms.Seek(0, SeekOrigin.Begin);
        bi.StreamSource = ms;
        bi.EndInit();
        return bi;
    }

进一步的代码：

 private BitmapImage _image;
 public BitmapImage Image {
        get => _image;
        set
        {
            _image = value;
            OnPropertyChanged();
        }
    }

摄像机的开始。

            if (SelectedDevice != null)
            {
                _videoSource = new VideoCaptureDevice(SelectedDevice.MonikerString);
                //var test = _videoSource.VideoCapabilities;
                _videoSource.NewFrame += video_NewFrame;
                _videoSource.Start();


            }

UI：

 <Image Height="400" Width="400" Source="{Binding Image, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,0"/>

我也试了一下

 Dispatcher.CurrentDispatcher.Invoke(() => Image = ToBitmapImage(bitmap));

Answer 1

当从流中加载一个BitmapImage时，你通常会尽快关闭流，并确保BitmapImage被立即加载，通过设置 "加载BitmapImage "来实现。BitmapCacheOption.OnLoad.

private static BitmapImage ToBitmapImage(Bitmap bitmap)
{
    var start = 420;
    var end = 1920 - 2 * 420;

    var croppedBitmap = bitmap.Clone(
        new System.Drawing.Rectangle(start, 0, end, 1080),
        bitmap.PixelFormat);          

    var bi = new BitmapImage();

    using (var ms = new MemoryStream())
    {
        croppedBitmap.Save(ms, ImageFormat.Bmp);
        ms.Seek(0, SeekOrigin.Begin);

        bi.BeginInit();
        bi.CacheOption = BitmapCacheOption.OnLoad;
        bi.StreamSource = ms;
        bi.EndInit();
    }

    bi.Freeze();

    return bi;
}