C++ VideoCapture::grab方法代码示例

void* grabFunc(void* in_data)
{
    while(running)
    {
        pthread_mutex_lock(&mutexLock);
        if(camera.isOpened())
        {
            camera.grab();
        }
        pthread_mutex_unlock(&mutexLock);
    }

    std::cout << "Grab thread exit." << std::endl;
}

/**
 * @function main
 */
int main( int argc, char* argv[] ) {
  
  // Filter
  gFilterLimits.resize(6);
  //gFilterLimits << -0.35, 0.35, -0.70, 0.70, 1.5, 2.4; // Kinect
  gFilterLimits << -1.0, 1.0, -1.5, 1.5, 0.35, 2.0; // Asus on top of Crichton


  ObjectsDatabase mOd;
  mOd.init_classifier();
  mOd.load_dataset();

  gCapture.open( cv::CAP_OPENNI2 );
  
  if( !gCapture.isOpened() ) {
    printf("\t [ERROR] Could not open the capture object \n");
    return -1;
  }

  gCapture.set( cv::CAP_PROP_OPENNI2_MIRROR, 0.0 );
  gCapture.set( cv::CAP_PROP_OPENNI_REGISTRATION, -1.0 );
  gF = (float)gCapture.get( cv::CAP_OPENNI_DEPTH_GENERATOR_FOCAL_LENGTH );

  cv::namedWindow( gWindowName, cv::WINDOW_AUTOSIZE );
 
  ::google::InitGoogleLogging( argv[0] );
  
  for(;;) {

    if( !gCapture.grab() ) {
      printf("\t * ERROR Could not grab a frame \n");
      return -1;
    }

    gCapture.retrieve( gRgbImg, cv::CAP_OPENNI_BGR_IMAGE );
    if( gIsSegmentedFlag ) { drawSegmented(); }
    cv::imshow( gWindowName, gRgbImg );
    
    gCapture.retrieve( gPclMap, cv::CAP_OPENNI_POINT_CLOUD_MAP );


    cv::imshow( gWindowName, gRgbImg );

    char k = cv::waitKey(30);
    if( k == 'q' ) {
      printf("\t Finishing program \n");
      break;
    } 

    /** Recognize */
    else if( k == 'i' ) {

      // Process image
      process();
      gLabels.resize(gClusters.size() );
      gIndex.resize(gClusters.size() );      
      // Store images
      for( int i = 0; i < gClusters.size(); ++i ) {

	int xl = gBoundingBoxes[i](0);
	int yl = gBoundingBoxes[i](1);
	int xw = gBoundingBoxes[i](2)-gBoundingBoxes[i](0);
	int yw = gBoundingBoxes[i](3)-gBoundingBoxes[i](1);
	
	cv::Mat img( gRgbImg, cv::Rect( xl, yl,
					xw, yw ) );
	
	// Predict 
	mOd.classify( img, gIndex[i], gLabels[i] );
	
	cv::putText( gRgbImg,
		     gLabels[i], cv::Point(gBoundingBoxes[i](0), gBoundingBoxes[i](1) ),
		     cv::FONT_HERSHEY_SIMPLEX, 1, 
		     gColors[i],
		     2 );

	mOd.sayIt(gIndex[i]);
      }
      
      
      
    } // else
    
    
  } // for
  
} // main

int main() {
	
	

	// 打开摄像头
	video_capture.open(0);
	if (!video_capture.isOpened()){
		std::cerr << "Could not open video" << endl;
		return -1;
	}

	// 获取第一张图像，用于这设置参数
	video_capture >> input_image;

	// 读取摄像机参数
	camera_params.readFromXMLFile("camera.yml");
	camera_params.resize(input_image.size());

	// 注册窗口
	cv::namedWindow("thres",1);
	cv::namedWindow("in",1);

	marker_dector.getThresholdParams(threshold_param1, threshold_param2);
	i_threshold_param1 = threshold_param1;
	i_threshold_param2 = threshold_param2;

	cv::createTrackbar("ThresParam1", "in",&i_threshold_param1, 13, cvTackBarEvents);
	cv::createTrackbar("ThresParam2", "in",&i_threshold_param2, 13, cvTackBarEvents);

	char key=0;
	int index=0;

	//capture until press ESC or until the end of the video
	while( key!=27 && video_capture.grab())
	{
		//copy image
		video_capture.retrieve(input_image);
		
		//number of images captured
		index++; 

		//for checking the speed
		double tick = (double)cv::getTickCount();
		//Detection of markers in the image passed
		marker_dector.detect(input_image, markers, camera_params, marker_size);
		//chekc the speed by calculating the mean speed of all iterations
		average_time.first += ((double)cv::getTickCount() - tick) / cv::getTickFrequency();
		average_time.second++;
		std::cout << "Time detection=" << 1000 * average_time.first / average_time.second << " milliseconds" << endl;

		//print marker info and draw the markers in image
		input_image.copyTo(input_image_copy);
		for(unsigned int i = 0; i < markers.size(); i++){
			std::cout << markers[i] << std::endl;
			markers[i].draw(input_image, Scalar(0, 0, 255), 2);
		}

		//draw a 3d cube in each marker if there is 3d info
		if ( camera_params.isValid())
			for(unsigned int i = 0; i < markers.size(); i++){
				aruco::CvDrawingUtils::draw3dCube(input_image, markers[i], camera_params);
				aruco::CvDrawingUtils::draw3dAxis(input_image, markers[i], camera_params);
			}

			//DONE! Easy, right?
			cout << endl << endl << endl;
			//show input with augmented information and  the thresholded image
			cv::imshow("in", input_image);
			cv::imshow("thres", marker_dector.getThresholdedImage());

			key=cv::waitKey(0);//wait for key to be pressed
	}
	return 0;
}

 bool hasFrame(cv::VideoCapture& capture) {
     bool hasNotQuit = ((char) cv::waitKey(1)) != 'q';
     bool hasAnotherFrame = capture.grab();
     return hasNotQuit && hasAnotherFrame;
 }

int main(int argc, char** argv)
{
    
    /// READ PARAMETERS
    if(!readParameters(argc, argv))
    return false;
    
    /// CREATE UNDISTORTED CAMERA PARAMS
    CameraParamsUnd=CameraParams;
    CameraParamsUnd.Distorsion=cv::Mat::zeros(4,1,CV_32F);
    cout<<" REATE UNDISTORTED CAMERA PARAMS "<<endl;
    
    /// SET BOARD DETECTOR PARAMETERS
    TheBoardDetector.setParams(TheBoardConfig,CameraParamsUnd,TheMarkerSize);
    
    /// CAPTURE FIRST FRAME
    TheVideoCapturer.grab();
    TheVideoCapturer.retrieve ( TheInputImage );
    cv::undistort(TheInputImage,TheInputImageUnd,CameraParams.CameraMatrix,CameraParams.Distorsion);
    cout<<" CAPTURE FIRST FRAME "<<endl;
    /// INIT OGRE
    initOgreAR(CameraParamsUnd, TheInputImageUnd.ptr<uchar>(0));
    cout<<" OGRE initiated "<<endl;
    while (TheVideoCapturer.grab())
    {
        
        /// READ AND UNDISTORT IMAGE
        TheVideoCapturer.retrieve ( TheInputImage );
        cv::undistort(TheInputImage,TheInputImageUnd,CameraParams.CameraMatrix,CameraParams.Distorsion);
        
        /// DETECT BOARD
        float probDetect = TheBoardDetector.detect(TheInputImageUnd);
        cout<<" detection: "<<probDetect<<endl;
        /// UPDATE BACKGROUND IMAGE
        mTexture->getBuffer()->blitFromMemory(mPixelBox);
        
        /// UPDATE SCENE
        if ( probDetect>0.2) ogreNode->setVisible(true);
        else ogreNode->setVisible(false);
        
        // set node pose
        double position[3], orientation[4];
        TheBoardDetector.getDetectedBoard().OgreGetPoseParameters(position, orientation);
        ogreNode->setPosition( position[0], position[1], position[2]  );
        ogreNode->setOrientation( orientation[0], orientation[1], orientation[2], orientation[3]  );
        
        // Update animation
        double deltaTime = 1.2*root->getTimer()->getMilliseconds()/1000.;
        baseAnim->addTime(deltaTime);
        topAnim->addTime(deltaTime);
        root->getTimer()->reset();
        
        /// RENDER FRAME
        if(root->renderOneFrame() == false) break;
        Ogre::WindowEventUtilities::messagePump();
        
        /// KEYBOARD INPUT
        keyboard->capture();
        if (keyboard->isKeyDown(OIS::KC_ESCAPE)) break;
        
        
    }
    
    im->destroyInputObject(keyboard);
    im->destroyInputSystem(im);
    im = 0;
    
    delete root;
    return 0;
}