Refactored internal helpers. Simplified structure. Updated comments. Updates #41

Signed-off-by: Maxim Kostin <v-maxkos@microsoft.com>

modules/videoio/include/opencv2/videoio/cap_winrt.hpp

@@ -54,8 +54,11 @@ CV_EXPORTS void winrt_startMessageLoop(void callback(Args...), Args... args);
 
 /** @brief
 @note
-    Sets the reporter method for the HighguiAssist singleton. Starts the main OpenCV as
-    an async thread in WinRT. See VideoCapture for the example of callback implementation.
+    Starts (1) frame-grabbing loop and (2) message loop
+    1. Function passed as an argument must implement common OCV reading frames
+       pattern (see cv::VideoCapture documentation) AND call cv::winrt_imgshow().
+    2. Message processing loop required to overcome WinRT container and type
+       conversion restrictions. OCV provides default implementation
        Here is how the class can be used:
 @code
     void cvMain()

modules/videoio/src/cap.cpp

@@ -697,7 +697,7 @@ VideoCapture& VideoCapture::operator >> (Mat& image)
             bridge.bIsFrameNew = false;
 
             // needed here because setting Mat 'image' is not allowed by OutputArray in read()
-            Mat m(bridge.height, bridge.width, CV_8UC3, p);
+            Mat m(bridge.getHeight(), bridge.getWidth(), CV_8UC3, p);
             image = m;
         }
     }

modules/videoio/src/cap_winrt/MediaStreamSink.cpp

@@ -227,7 +227,6 @@ HRESULT MediaStreamSink::IsMediaTypeSupported(__in IMFMediaType *mediaType, __de
     HRESULT hr = ExceptionBoundary([this, mediaType, closestMediaType, &supported]()
     {
         auto lock = _lock.LockExclusive();
-        HRESULT hr = S_OK;
 
         if (closestMediaType != nullptr)
         {
@@ -281,7 +280,6 @@ HRESULT MediaStreamSink::SetCurrentMediaType(__in IMFMediaType *mediaType)
     return ExceptionBoundary([this, mediaType]()
     {
         auto lock = _lock.LockExclusive();
-        HRESULT hr = S_OK;
 
         CHKNULL(mediaType);
 

modules/videoio/src/cap_winrt_bridge.cpp

@@ -45,7 +45,7 @@ using namespace ::std;
 /***************************** VideoioBridge class ******************************/
 
 // non-blocking
-void VideoioBridge::requestForUIthreadAsync(int action, int widthp, int heightp)
+void VideoioBridge::requestForUIthreadAsync(int action)
 {
     reporter.report(action);
 }
@@ -80,10 +80,79 @@ void VideoioBridge::allocateOutputBuffers()
     backOutputBuffer = ref new WriteableBitmap(width, height);
 }
 
+// performed on UI thread
+void VideoioBridge::allocateBuffers(int width, int height)
+{
+    // allocate input Mats (bgra8 = CV_8UC4, RGB24 = CV_8UC3)
+    frontInputMat.create(height, width, CV_8UC3);
+    backInputMat.create(height, width, CV_8UC3);
+
+    frontInputPtr = frontInputMat.ptr(0);
+    backInputPtr = backInputMat.ptr(0);
+
+    allocateOutputBuffers();
+}
+
+// performed on UI thread
+bool VideoioBridge::openCamera()
+{
+    // buffers must alloc'd on UI thread
+    allocateBuffers(width, height);
+
+    // nb. video capture device init must be done on UI thread;
+    if (!Video::getInstance().isStarted())
+    {
+        Video::getInstance().initGrabber(deviceIndex, width, height);
+        return true;
+    }
+
+    return false;
+}
+
+// nb on UI thread
+void VideoioBridge::updateFrameContainer()
+{
+    // copy output Mat to WBM
+    Video::getInstance().CopyOutput();
+
+    // set XAML image element with image WBM
+    cvImage->Source = backOutputBuffer;
+}
+
 void VideoioBridge::imshow()
 {
-    VideoioBridge::getInstance().swapOutputBuffers();
-    VideoioBridge::getInstance().requestForUIthreadAsync(cv::UPDATE_IMAGE_ELEMENT);
+    swapOutputBuffers();
+    requestForUIthreadAsync(cv::UPDATE_IMAGE_ELEMENT);
+}
+
+int VideoioBridge::getDeviceIndex()
+{
+    return deviceIndex;
+}
+
+void VideoioBridge::setDeviceIndex(int index)
+{
+    deviceIndex = index;
+}
+
+int VideoioBridge::getWidth()
+{
+    return width;
+}
+
+int VideoioBridge::getHeight()
+{
+    return height;
+}
+
+void VideoioBridge::setWidth(int _width)
+{
+    width = _width;
+}
+
+void VideoioBridge::setHeight(int _height)
+{
+    height = _height;
 }
 
 // end
\ No newline at end of file

modules/videoio/src/cap_winrt_bridge.hpp

@@ -53,16 +53,24 @@ public:
     void    setReporter(Concurrency::progress_reporter<int> pr) { reporter = pr; }
 
     // to be called from cvMain via cap_winrt on bg thread - non-blocking (async)
-    void requestForUIthreadAsync( int action, int width=0, int height=0 );
+    void    requestForUIthreadAsync(int action);
 
     // TODO: modify in window.cpp: void cv::imshow( const String& winname, InputArray _img )
     void    imshow(/*cv::InputArray matToShow*/);   // shows Mat in the cvImage element
     void    swapInputBuffers();
     void    allocateOutputBuffers();
     void    swapOutputBuffers();
+    void    updateFrameContainer();
+    bool    openCamera();
+    void    allocateBuffers(int width, int height);
 
+    int     getDeviceIndex();
+    void    setDeviceIndex(int index);
+    int     getWidth();
+    void    setWidth(int width);
+    int     getHeight();
+    void    setHeight(int height);
 
-    int                         deviceIndex, width, height;
     std::atomic<bool>           bIsFrameNew;
     std::mutex                  inputBufferMutex;   // input is double buffered
     unsigned char *             frontInputPtr;      // OpenCV reads this
@@ -93,4 +101,17 @@ private:
 
     std::atomic<bool>   deviceReady;
     Concurrency::progress_reporter<int> reporter;
+
+    // Mats are wrapped with singleton class, we do not support more than one
+    // capture device simultaneously with the design at this time
+    //
+    // nb. inputBufferMutex was not able to guarantee that OpenCV Mats were
+    // ready to accept data in the UI thread (memory access exceptions were thrown
+    // even though buffer address was good).
+    // Therefore allocation of Mats is also done on the UI thread before the video
+    // device is initialized.
+    cv::Mat frontInputMat;
+    cv::Mat backInputMat;
+
+    int deviceIndex, width, height;
 };
\ No newline at end of file

modules/videoio/src/cap_winrt_capture.cpp

@@ -43,23 +43,9 @@ using namespace Microsoft::WRL;
 
 using namespace ::std;
 
-
-// nb. VideoCapture_WinRT is not a singleton, so the Mats are made file statics
-// we do not support more than one capture device simultaneously with the
-// design at this time
-
-// nb. inputBufferMutex was not able to guarantee that OpenCV Mats were
-// ready to accept data in the UI thread (memory access exceptions were thrown
-// even though buffer address was good).
-// Therefore allocation of Mats is also done on the UI thread before the video
-// device is initialized.
-
-static cv::Mat frontInputMat;
-static cv::Mat backInputMat;
-
 namespace cv {
 
-    /***************************** exported control functions ******************************/
+    /******************************* exported API functions **************************************/
 
     template <typename ...Args>
     void winrt_startMessageLoop(std::function<void(Args...)>&& callback, Args... args)
@@ -80,13 +66,13 @@ namespace cv {
             switch (action)
             {
             case OPEN_CAMERA:
-                winrt_openCamera();
+                VideoioBridge::getInstance().openCamera();
                 break;
             case CLOSE_CAMERA:
-                winrt_closeGrabber();
+                Video::getInstance().closeGrabber();
                 break;
             case UPDATE_IMAGE_ELEMENT:
-                winrt_updateFrameContainer();
+                VideoioBridge::getInstance().updateFrameContainer();
                 break;
             }
         });
@@ -98,7 +84,8 @@ namespace cv {
         winrt_startMessageLoop(std::function<void(Args...)>(callback), args...);
     }
 
-    void winrt_onVisibilityChanged(bool visible) {
+    void winrt_onVisibilityChanged(bool visible)
+    {
         if (visible)
         {
             VideoioBridge& bridge = VideoioBridge::getInstance();
@@ -108,99 +95,34 @@ namespace cv {
             {
                 if (Video::getInstance().isStarted()) return;
 
-                int device = bridge.deviceIndex;
-                int width = bridge.width;
-                int height = bridge.height;
+                int device = bridge.getDeviceIndex();
+                int width = bridge.getWidth();
+                int height = bridge.getHeight();
 
-                winrt_initGrabber(device, width, height);
+                Video::getInstance().initGrabber(device, width, height);
             }
         } else
         {
             //grabberStarted = false;
-            winrt_closeGrabber();
-        }
-    }
-
-    void winrt_imshow() {
-        VideoioBridge::getInstance().imshow();
-    }
-
-    void winrt_setFrameContainer(::Windows::UI::Xaml::Controls::Image^ image) {
-        VideoioBridge::getInstance().cvImage = image;
+            Video::getInstance().closeGrabber();
         }
-
-
-    /********************************* Internal helpers ************************************/
-
-    void winrt_updateFrameContainer()
-    {
-        // copy output Mat to WBM
-        winrt_copyOutput();
-
-        // set XAML image element with image WBM
-        VideoioBridge::getInstance().cvImage->Source = VideoioBridge::getInstance().backOutputBuffer;
     }
 
-    // performed on UI thread
-    bool winrt_openCamera()
-    {
-        VideoioBridge& bridge = VideoioBridge::getInstance();
-
-        int device = bridge.deviceIndex;
-        int width = bridge.width;
-        int height = bridge.height;
-
-        // buffers must alloc'd on UI thread
-        winrt_allocateBuffers(width, height);
-
-        // nb. video capture device init must be done on UI thread;
-        if (!Video::getInstance().isStarted())
+    void winrt_imshow()
     {
-            winrt_initGrabber(device, width, height);
-            return true;
-        }
-
-        return false;
+        VideoioBridge::getInstance().imshow();
     }
 
-    // performed on UI thread
-    void winrt_allocateBuffers(int width, int height)
+    void winrt_setFrameContainer(::Windows::UI::Xaml::Controls::Image^ image)
     {
-        VideoioBridge& bridge = VideoioBridge::getInstance();
-
-        // allocate input Mats (bgra8 = CV_8UC4, RGB24 = CV_8UC3)
-        frontInputMat.create(height, width, CV_8UC3);
-        backInputMat.create(height, width, CV_8UC3);
-
-        bridge.frontInputPtr = frontInputMat.ptr(0);
-        bridge.backInputPtr = backInputMat.ptr(0);
-
-        bridge.allocateOutputBuffers();
-    }
-
-    // non-blocking
-    bool winrt_initGrabber(int device, int w, int h) {
-        // nb. Video class is not exported outside of this DLL
-        // due to complexities in the CaptureFrameGrabber ref class
-        // as written in the header not mixing well with pure C++ classes
-        return Video::getInstance().initGrabber(device, w, h);
-    }
-
-    void winrt_closeGrabber() {
-        Video::getInstance().closeGrabber();
-    }
-
-    // nb on UI thread
-    void winrt_copyOutput() {
-        Video::getInstance().CopyOutput();
+        VideoioBridge::getInstance().cvImage = image;
     }
 
-
     /********************************* VideoCapture_WinRT class ****************************/
 
     VideoCapture_WinRT::VideoCapture_WinRT(int device) : started(false)
     {
-        VideoioBridge::getInstance().deviceIndex = device;
+        VideoioBridge::getInstance().setDeviceIndex(device);
     }
 
     bool VideoCapture_WinRT::isOpened() const
@@ -240,14 +162,13 @@ namespace cv {
             if (width == 0) width = 640;
             if (height == 0) height = 480;
 
-            VideoioBridge::getInstance().width = width;
-            VideoioBridge::getInstance().height = height;
+            VideoioBridge::getInstance().setWidth(width);
+            VideoioBridge::getInstance().setHeight(height);
 
             // nb. Mats will be alloc'd on UI thread
 
             // request device init on UI thread - this does not block, and is async
-            VideoioBridge::getInstance().requestForUIthreadAsync(OPEN_CAMERA,
-                outArray.size().width, outArray.size().height);
+            VideoioBridge::getInstance().requestForUIthreadAsync(OPEN_CAMERA);
 
             started = true;
             return false;

modules/videoio/src/cap_winrt_capture.hpp

@@ -42,17 +42,6 @@
 
 namespace cv {
 
-    /******************* Internal helpers **************************************/
-
-    void winrt_updateFrameContainer();
-    bool winrt_openCamera();
-    bool winrt_initGrabber(int device, int w, int h);
-    void winrt_closeGrabber();
-    void winrt_copyOutput();
-    void winrt_allocateBuffers(int width, int height);
-
-    /******************* VideoCapture_WinRT class ******************************/
-
     class VideoCapture_WinRT : public IVideoCapture
     {
     public:

modules/videoio/src/cap_winrt_video.cpp

@@ -78,7 +78,7 @@ void Video::closeGrabber() {
     bGrabberInitInProgress = false;
 }
 
-
+// non-blocking
 bool Video::initGrabber(int device, int w, int h) {
     // already started?
     if (bGrabberInited || bGrabberInitInProgress) return false;
@@ -124,7 +124,7 @@ bool Video::initGrabber(int device, int w, int h) {
             // for 24 bpp
             props->Subtype = MediaEncodingSubtypes::Rgb24;      bytesPerPixel = 3;
 
-            // format used by XAML & WBM (for testing)
+            // XAML & WBM use BGRA8, so it would look like
             // props->Subtype = MediaEncodingSubtypes::Bgra8;   bytesPerPixel = 4;
 
             props->Width = width;
@@ -282,22 +282,20 @@ bool Video::listDevicesTask() {
 
     auto settings = ref new MediaCaptureInitializationSettings();
 
-    //vector <int> devices;
-
     create_task(DeviceInformation::FindAllAsync(DeviceClass::VideoCapture))
         .then([this, &ready](task<DeviceInformationCollection^> findTask)
     {
         m_devices = findTask.get();
 
-        for (size_t i = 0; i < m_devices->Size; i++)
-        {
-            // ofVideoDevice deviceInfo;
-            auto d = m_devices->GetAt(i);
-            //deviceInfo.bAvailable = true;
-            //deviceInfo.deviceName = PlatformStringToString(d->Name);
-            //deviceInfo.hardwareName = deviceInfo.deviceName;
-            // devices.push_back(deviceInfo);
-        }
+        // TODO: collect device data
+        // for (size_t i = 0; i < m_devices->Size; i++)
+        // {
+        //   .. deviceInfo;
+        //   auto d = m_devices->GetAt(i);
+        //   deviceInfo.bAvailable = true;
+        //   deviceInfo.deviceName = PlatformStringToString(d->Name);
+        //   deviceInfo.hardwareName = deviceInfo.deviceName;
+        // }
 
         ready = true;
     });

modules/videoio/src/cap_winrt_video.hpp

@@ -34,6 +34,7 @@
 class Video {
 public:
 
+    // non-blocking
     bool initGrabber(int device, int w, int h);
     void closeGrabber();
     bool isStarted();