kinect for windows

首先看骨骼追踪例子代码的结构：

例子代码不是很多，在SkeletonBasics.cpp中，大部分的功能都在kinect SDK中实现，应用开发只需要了解接口，并调用它的接口即可。首先我们找到main函数：

int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow)
{
    CSkeletonBasics application;
    application.Run(hInstance, nCmdShow);
}

这个main函数是不是似曾相识，跟深度图的main函数差不多的，只是构造一个对象，然后调用这个对象的Run接口，构造函数只是初始化成员，所以我们直接看Run的实现：

int CSkeletonBasics::Run(HINSTANCE hInstance, int nCmdShow)
{
    MSG       msg = {0};
    WNDCLASS  wc  = {0};

    // Dialog custom window class
    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.cbWndExtra    = DLGWINDOWEXTRA;
    wc.hInstance     = hInstance;
    wc.hCursor       = LoadCursorW(NULL, IDC_ARROW);
    wc.hIcon         = LoadIconW(hInstance, MAKEINTRESOURCE(IDI_APP));
    wc.lpfnWndProc   = DefDlgProcW;
    wc.lpszClassName = L"SkeletonBasicsAppDlgWndClass";

    if (!RegisterClassW(&wc))
    {
        return 0;
    }

    // Create main application window
    HWND hWndApp = CreateDialogParamW(
        hInstance,
        MAKEINTRESOURCE(IDD_APP),
        NULL,
        (DLGPROC)CSkeletonBasics::MessageRouter, 
        reinterpret_cast<LPARAM>(this));

    // Show window
    ShowWindow(hWndApp, nCmdShow);

    const int eventCount = 1;
    HANDLE hEvents[eventCount];

    // Main message loop
    while (WM_QUIT != msg.message)
    {
        hEvents[0] = m_hNextSkeletonEvent;

        // Check to see if we have either a message (by passing in QS_ALLEVENTS)
        // Or a Kinect event (hEvents)
        // Update() will check for Kinect events individually, in case more than one are signalled
        DWORD dwEvent = MsgWaitForMultipleObjects(eventCount, hEvents, FALSE, INFINITE, QS_ALLINPUT);

        // Check if this is an event we're waiting on and not a timeout or message
        if (WAIT_OBJECT_0 == dwEvent)
        {
            Update();
        }

        if (PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE))
        {
            // If a dialog message will be taken care of by the dialog proc
            if ((hWndApp != NULL) && IsDialogMessageW(hWndApp, &msg))
            {
                continue;
            }

            TranslateMessage(&msg);
            DispatchMessageW(&msg);
        }
    }

    return static_cast<int>(msg.wParam);
}

这个Run函数是不是也是很熟悉，跟深度图的Run函数也是差不多，创建对话框，然后进入消息处理死循环，在死循环里处理窗口消息和kinect消息。

接下来和深度图一样，我们也进入到窗口初始化消息里，看整个程序的初始化是怎么样的：

LRESULT CALLBACK CSkeletonBasics::DlgProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_INITDIALOG:
        {
            // Bind application window handle
            m_hWnd = hWnd;

            // Init Direct2D
            D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &m_pD2DFactory);

            // Look for a connected Kinect, and create it if found
            CreateFirstConnected();
        }
        break;

初始化处理和深度图也差不多，D2D1CreateFactory函数创建DirectX对象，然后调用CreateFirstConnected去创建kinect对象，在CreateFirstConnected函数里的处理又有何不同呢？我们一起来看代码：

HRESULT CSkeletonBasics::CreateFirstConnected()
{
    INuiSensor * pNuiSensor;

	// 获取kinect数量
    int iSensorCount = 0;
    HRESULT hr = NuiGetSensorCount(&iSensorCount);
    if (FAILED(hr))
    {
        return hr;
    }

    // Look at each Kinect sensor  查找一个有效的kinect设备
    for (int i = 0; i < iSensorCount; ++i)
    {
        // Create the sensor so we can check status, if we can't create it, move on to the next
        hr = NuiCreateSensorByIndex(i, &pNuiSensor);
        if (FAILED(hr))
        {
            continue;
        }

        // Get the status of the sensor, and if connected, then we can initialize it
        hr = pNuiSensor->NuiStatus();
        if (S_OK == hr)
        {
            m_pNuiSensor = pNuiSensor;
            break;
        }

        // This sensor wasn't OK, so release it since we're not using it
        pNuiSensor->Release();
    }

    if (NULL != m_pNuiSensor)
    {
        // 这里的参数和深度图不一样，深度图用的参数是NUI_INITIALIZE_FLAG_USES_DEPTH
		// 这个意思就是将这个kinect初始化成骨骼跟踪
        hr = m_pNuiSensor->NuiInitialize(NUI_INITIALIZE_FLAG_USES_SKELETON); 
        if (SUCCEEDED(hr))
        {
            // 这个Event和深度图一样，是kinectSDK和上层应用程序通信的事件
            m_hNextSkeletonEvent = CreateEventW(NULL, TRUE, FALSE, NULL);

            // 打开一个骨骼跟踪数据，深度图需要的参数比较复杂，这个比较简答
            hr = m_pNuiSensor->NuiSkeletonTrackingEnable(m_hNextSkeletonEvent, 0); 
        }
    }

    if (NULL == m_pNuiSensor || FAILED(hr))
    {
        SetStatusMessage(L"No ready Kinect found!");
        return E_FAIL;
    }

    return hr;
}

看初始化kinect设备的代码，貌似区别也不是很大，只是初始化参数不同，打开数据流的函数不同，框架性的代码还是差不多的。

当这个m_hNextSkeletonEvent事件被注册到kinect SDK库之后，当有数据来时，Update函数会被调用，Update函数最后调用了ProcessSkeleton函数来处理骨骼数据：

void CSkeletonBasics::ProcessSkeleton()
{
    NUI_SKELETON_FRAME skeletonFrame = {0};

	// 获取一帧骨骼数据
    HRESULT hr = m_pNuiSensor->NuiSkeletonGetNextFrame(0, &skeletonFrame);
    if ( FAILED(hr) )
    {
        return;
    }

    // 让骨骼数据变得平滑，消除抖动现象
    m_pNuiSensor->NuiTransformSmooth(&skeletonFrame, NULL);

    // 创建m_pRenderTarget对象
    hr = EnsureDirect2DResources( );
    if ( FAILED(hr) )
    {
        return;
    }

    m_pRenderTarget->BeginDraw();
    m_pRenderTarget->Clear( );

    RECT rct;
    GetClientRect( GetDlgItem( m_hWnd, IDC_VIDEOVIEW ), &rct);
    int width = rct.right;
    int height = rct.bottom;

	// 最多支持6个人的骨骼跟踪数据
    for (int i = 0 ; i < NUI_SKELETON_COUNT; ++i)
    {
        NUI_SKELETON_TRACKING_STATE trackingState = skeletonFrame.SkeletonData[i].eTrackingState;

        if (NUI_SKELETON_TRACKED == trackingState)
        {
            // 画骨骼
            DrawSkeleton(skeletonFrame.SkeletonData[i], width, height);
        }
        else if (NUI_SKELETON_POSITION_ONLY == trackingState)
        {
            // 只是跟踪位置的话，那么就画个位置，在人很多时，kinect只跟踪两个人的骨骼，其他人之显示位置
            D2D1_ELLIPSE ellipse = D2D1::Ellipse(
                SkeletonToScreen(skeletonFrame.SkeletonData[i].Position, width, height),
                g_JointThickness,
                g_JointThickness
                );

            m_pRenderTarget->DrawEllipse(ellipse, m_pBrushJointTracked);
        }
    }

    hr = m_pRenderTarget->EndDraw();

    // Device lost, need to recreate the render target
    // We'll dispose it now and retry drawing
    if (D2DERR_RECREATE_TARGET == hr)
    {
        hr = S_OK;
        DiscardDirect2DResources();
    }
}

在处理骨骼数据函数中，对数据skeletonFrame中保存的六个骨骼跟踪数据循环处理，如果状态是NUI_SKELETON_TRACKED则通过DrawSkeleton画详细骨骼信息，如果是NUI_SKELETON_POSITION_ONLY则只画位置信息，如果不是这两个状态，则啥也不做。接下来我们来看看DrawSkeleton看看骨骼信息怎么画的：

void CSkeletonBasics::DrawSkeleton(const NUI_SKELETON_DATA & skel, int windowWidth, int windowHeight)
{      
    int i;

	// 将关节点转化成屏幕上的坐标点
    for (i = 0; i < NUI_SKELETON_POSITION_COUNT; ++i)
    {
        m_Points[i] = SkeletonToScreen(skel.SkeletonPositions[i], windowWidth, windowHeight);
    }

    // 画骨骼，参数1是骨骼数据，参数2和参数3是关节
    DrawBone(skel, NUI_SKELETON_POSITION_HEAD, NUI_SKELETON_POSITION_SHOULDER_CENTER); // 这个是脑袋，从脑袋关节到肩膀中间
    DrawBone(skel, NUI_SKELETON_POSITION_SHOULDER_CENTER, NUI_SKELETON_POSITION_SHOULDER_LEFT);  // 肩膀中间到左边
    DrawBone(skel, NUI_SKELETON_POSITION_SHOULDER_CENTER, NUI_SKELETON_POSITION_SHOULDER_RIGHT);  // 肩膀中间到右边，下面的类似
    DrawBone(skel, NUI_SKELETON_POSITION_SHOULDER_CENTER, NUI_SKELETON_POSITION_SPINE);
    DrawBone(skel, NUI_SKELETON_POSITION_SPINE, NUI_SKELETON_POSITION_HIP_CENTER);
    DrawBone(skel, NUI_SKELETON_POSITION_HIP_CENTER, NUI_SKELETON_POSITION_HIP_LEFT);
    DrawBone(skel, NUI_SKELETON_POSITION_HIP_CENTER, NUI_SKELETON_POSITION_HIP_RIGHT);

    // Left Arm
    DrawBone(skel, NUI_SKELETON_POSITION_SHOULDER_LEFT, NUI_SKELETON_POSITION_ELBOW_LEFT);
    DrawBone(skel, NUI_SKELETON_POSITION_ELBOW_LEFT, NUI_SKELETON_POSITION_WRIST_LEFT);
    DrawBone(skel, NUI_SKELETON_POSITION_WRIST_LEFT, NUI_SKELETON_POSITION_HAND_LEFT);

    // Right Arm
    DrawBone(skel, NUI_SKELETON_POSITION_SHOULDER_RIGHT, NUI_SKELETON_POSITION_ELBOW_RIGHT);
    DrawBone(skel, NUI_SKELETON_POSITION_ELBOW_RIGHT, NUI_SKELETON_POSITION_WRIST_RIGHT);
    DrawBone(skel, NUI_SKELETON_POSITION_WRIST_RIGHT, NUI_SKELETON_POSITION_HAND_RIGHT);

    // Left Leg
    DrawBone(skel, NUI_SKELETON_POSITION_HIP_LEFT, NUI_SKELETON_POSITION_KNEE_LEFT);
    DrawBone(skel, NUI_SKELETON_POSITION_KNEE_LEFT, NUI_SKELETON_POSITION_ANKLE_LEFT);
    DrawBone(skel, NUI_SKELETON_POSITION_ANKLE_LEFT, NUI_SKELETON_POSITION_FOOT_LEFT);

    // Right Leg
    DrawBone(skel, NUI_SKELETON_POSITION_HIP_RIGHT, NUI_SKELETON_POSITION_KNEE_RIGHT);
    DrawBone(skel, NUI_SKELETON_POSITION_KNEE_RIGHT, NUI_SKELETON_POSITION_ANKLE_RIGHT);
    DrawBone(skel, NUI_SKELETON_POSITION_ANKLE_RIGHT, NUI_SKELETON_POSITION_FOOT_RIGHT);

    // 画关节
    for (i = 0; i < NUI_SKELETON_POSITION_COUNT; ++i)
    {
        D2D1_ELLIPSE ellipse = D2D1::Ellipse( m_Points[i], g_JointThickness, g_JointThickness );

        if ( skel.eSkeletonPositionTrackingState[i] == NUI_SKELETON_POSITION_INFERRED )
        {
            m_pRenderTarget->DrawEllipse(ellipse, m_pBrushJointInferred);
        }
        else if ( skel.eSkeletonPositionTrackingState[i] == NUI_SKELETON_POSITION_TRACKED )
        {
            m_pRenderTarget->DrawEllipse(ellipse, m_pBrushJointTracked);
        }
    }
}

在这里绘制比较简单，所以这里绘制并没有像深度图一样使用一个类来做绘制，直接写到函数里了。另外一个这里DirectX的绘制也就只是画画线，如果你熟悉GDI，完全可以通过GDI来绘图，而不用DirectX。