Method TrackFrameFeatures

src/CVStabilization.cpp:106–185

Track current frame features and find the relative transformation

// Track current frame features and find the relative transformation
bool CVStabilization::TrackFrameFeatures(cv::Mat frame, size_t frameNum){
    // Check if there are black frames
    if(cv::countNonZero(frame) < 1){
        return false;
    }

    // Initialize prev_grey if not
    if(prev_grey.empty()){
        prev_grey = frame;
        return true;
    }

    // OpticalFlow features vector
    std::vector <cv::Point2f> prev_corner, cur_corner;
    std::vector <cv::Point2f> prev_corner2, cur_corner2;
    std::vector <uchar> status;
    std::vector <float> err;
    // Extract new image features
    cv::goodFeaturesToTrack(prev_grey, prev_corner, 200, 0.01, 30);
    // Track features
    cv::calcOpticalFlowPyrLK(prev_grey, frame, prev_corner, cur_corner, status, err);
    // Remove untracked features
    for(size_t i=0; i < status.size(); i++) {
        if(status[i]) {
            prev_corner2.push_back(prev_corner[i]);
            cur_corner2.push_back(cur_corner[i]);
        }
    }
    // In case no feature was detected
    if(prev_corner2.empty() || cur_corner2.empty()){
        last_T = cv::Mat();
        // prev_grey = cv::Mat();
        return false;
    }

    // Translation + rotation only
    cv::Mat T = cv::estimateAffinePartial2D(prev_corner2, cur_corner2); // false = rigid transform, no scaling/shearing

    double da, dx, dy;
    // If T has nothing inside return (probably a segment where there is nothing to stabilize)
    if(T.size().width == 0 || T.size().height == 0){
        return false;
    }
    else{
        // If no transformation is found, just use the last known good transform
        if(T.data == NULL){
            if(!last_T.empty())
                last_T.copyTo(T);
            else
                return false;
        }
        // Decompose T
        dx = T.at<double>(0,2);
        dy = T.at<double>(1,2);
        da = atan2(T.at<double>(1,0), T.at<double>(0,0));
    }

    // Filter transformations parameters, if they are higher than these: return