Silverlight中摄像头的运用

Silverlight中摄像头的运用—part2

Silverlight 4 中摄像头的运用—part1

将跟踪颜色视作输入

好了，我们能够跟踪到这个颜色了，那这么做的意义是什么呢？实际上，我们可以根据它的位置来移动东西。接下来的例子中，创建的一个球会跟随这个颜色一起移动。你可以用来作出很诡异的对象跟随画面移动的效果。

关键代码：

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//part2

Ellipse ball = new Ellipse();

CompositeTransform ballctf;

ball.Width = 20;

ball.Height = 20;

ball.Fill = new SolidColorBrush(Colors.Orange);

ballctf = new CompositeTransform();

ball.RenderTransform = ballctf;

            labRes.Content = "捕获颜色=" + found.ToString();
            labPoint.Content = "坐标=" + _lastPoint.X.ToString() + "," + _lastPoint.Y.ToString();

            ballctf.TranslateX = _lastPoint.X;
            ballctf.TranslateY = _lastPoint.Y;

            Debug.WriteLine(found);
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分析移动区域

在这一节，我们虽然还不去涉及如何跟踪物体的具体轨迹，但会知道如何判断是否有移动。一个基本概念是：如果有移动，每帧的画面会明显不同。所以，如果发现两帧画面中位图的像素有不同的地方，就能知道发生了移动。

有两个潜在元素。第一，我们需要两张位图。第二，我们还需要一个比较函数。如果，你正在想着是否需要遍历所有像素来进行比较，那么我告诉你，这里有一个很实用的技巧：使用混合模式。绘制时如果不指定混合模式，新的像素值就会完全覆盖以取代存在的像素值。这也是我们至今为止一直在做的事情。如果使用混合模式，新的像素会影响已存在的像素，两张图片会以一种特别的方式混合在一起。而此刻，我们要用的混合模式叫做difference（差异），它对两张图片的红、绿、蓝三个通道的每个像素进行一次比较，然后给出它们之间的相减所得的差值。如果两个像素完全一致，那么结果就是0，也就是黑色，否则就是别的其它什么值（颜色）。这样，我们就把跟踪移动的问题简化了，只要寻找非黑色区域即可。

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public partial class MotionTracking : UserControl
    {
        CaptureSource _captureSource;
        VideoCaptureDevice _video;
        VideoBrush _videoBrush;
        Rectangle _rect;
        Image _wb_image;
        WriteableBitmap _wb = null;
        bool _isEnableCamera = false;

        WriteableBitmap _newFrameBitmap;
        WriteableBitmap _oldFrameBitmap;

        Image _newFrame;
        Image _oldFrame;

        public MotionTracking()
        {
            InitializeComponent();

            _captureSource = new CaptureSource();
            _video = CaptureDeviceConfiguration.GetDefaultVideoCaptureDevice();
            if (_video != null)
            {
                _video.DesiredFormat = _video.SupportedFormats[1];
                _captureSource.VideoCaptureDevice = _video;
                _videoBrush = new VideoBrush();
                _videoBrush.SetSource(_captureSource);
            }
            CompositionTarget.Rendering += new EventHandler(OnRender);

            btnStart.Click += new RoutedEventHandler(btnStart_Click);

            this.imageEffectsListBox.Items.Add(new NormalEffect());

            this.imageEffectsListBox.Items.Add(new DarkenEffect());
            this.imageEffectsListBox.Items.Add(new MultiplyEffect());
            this.imageEffectsListBox.Items.Add(new ColorBurnEffect());
            this.imageEffectsListBox.Items.Add(new LinearBurnEffect());

            this.imageEffectsListBox.Items.Add(new LightenEffect());
            this.imageEffectsListBox.Items.Add(new ScreenEffect());
            this.imageEffectsListBox.Items.Add(new ColorDodgeEffect());
            this.imageEffectsListBox.Items.Add(new LinearDodgeEffect());

            this.imageEffectsListBox.Items.Add(new OverlayEffect());
            this.imageEffectsListBox.Items.Add(new SoftLightEffect());
            this.imageEffectsListBox.Items.Add(new HardLightEffect());
            this.imageEffectsListBox.Items.Add(new VividLightEffect());
            this.imageEffectsListBox.Items.Add(new LinearLightEffect());
            this.imageEffectsListBox.Items.Add(new PinLightEffect());

            this.imageEffectsListBox.Items.Add(new DifferenceEffect());
            this.imageEffectsListBox.Items.Add(new ExclusionEffect());

            this.imageEffectsListBox.Items.Add(new GlowEffect());
            this.imageEffectsListBox.Items.Add(new ReflectEffect());

            this.imageEffectsListBox.Items.Add(new HardMixEffect());
            this.imageEffectsListBox.Items.Add(new NegationEffect());
            this.imageEffectsListBox.Items.Add(new PhoenixEffect());

            this.imageEffectsListBox.Items.Add(new AverageEffect());

            this.imageEffectsListBox.SelectedIndex = 0;
        }

        void btnStart_Click(object sender, RoutedEventArgs e)
        {
            if (CaptureDeviceConfiguration.AllowedDeviceAccess ||
                CaptureDeviceConfiguration.RequestDeviceAccess())
            {
                _rect = new Rectangle();
                _rect.Width = 320;
                _rect.Height = 240;

                _rect.Fill = _videoBrush;
                _rect.Visibility = Visibility.Collapsed;
                video_Canvas.Children.Add(_rect);

                _newFrameBitmap = new WriteableBitmap(_rect, null);
                _oldFrameBitmap = new WriteableBitmap(_rect, null);

                _newFrame = new Image();
                _newFrame.Width = 320;
                _newFrame.Height = 240;
                _newFrame.Source = _newFrameBitmap;
                _newFrame.Visibility = Visibility.Collapsed;

                _oldFrame = new Image();
                _oldFrame.Width = 320;
                _oldFrame.Height = 240;
                _oldFrame.Source = _oldFrameBitmap;

                video_Canvas.Children.Add(_oldFrame);
                video_Canvas.Children.Add(_newFrame);



                _captureSource.Start();
                _isEnableCamera = true;

                Thread thread = new Thread(new ThreadStart(ThreadProc));
                thread.Start();

            }
        }

        void OnRender(object sender, EventArgs e)
        {
            if (_isEnableCamera)
            {
                MatrixTransform transform = new MatrixTransform();
                transform.Matrix = new Matrix(-1, 0, 0, 1, 320, 0);

                _newFrameBitmap.Render(_rect, transform);
                _newFrameBitmap.Invalidate();
            }
        }

        void ThreadProc()
        {
            while (true)
            {
                Thread.Sleep(20);

                //Do the action in the UI thread
                Dispatcher.BeginInvoke(ThreadUpdate);
            }
        }

        void ThreadUpdate()
        {
            if (_isEnableCamera)
            {
                _oldFrameBitmap.Render(_newFrame, null);
                _oldFrameBitmap.Invalidate();
            }
        }

        private void imageEffectsListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            BlendModeEffect effect = e.AddedItems[0] as BlendModeEffect;
            if (effect != null)
            {
                if (_oldFrameBitmap != null)
                {
                    ImageBrush _newImageBrush = new ImageBrush();
                    _newImageBrush.ImageSource = _newFrameBitmap;
                    ImageBrush _oldImageBrush = new ImageBrush();
                    _oldImageBrush.ImageSource = _oldFrameBitmap;

                    //effect.AInput = _oldImageBrush;
                    effect.BInput = _newImageBrush;
                    this._oldFrame.Effect = effect;
                }
            }
        }
    }

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