Method trackFrame

src/CVTracker.cpp:172–327

Update the object tracker according to frame returns true if KLT succeeded, false otherwise

// Update the object tracker according to frame
// returns true if KLT succeeded, false otherwise
bool CVTracker::trackFrame(cv::Mat &frame, size_t frameId)
{
    const int W = frame.cols, H = frame.rows;
    const auto& prev = trackedDataById[frameId - 1];

    // Reconstruct last-known box in pixel coords
    cv::Rect2d lastBox(
        prev.x1 * W, prev.y1 * H,
        (prev.x2 - prev.x1) * W,
        (prev.y2 - prev.y1) * H
    );

    // Convert to grayscale
    cv::Mat gray;
    cv::cvtColor(frame, gray, cv::COLOR_BGR2GRAY);

    const bool prevGrayMatches =
        !prevGray.empty() &&
        prevGray.size() == gray.size() &&
        prevGray.type() == gray.type();
    const bool fullPrevGrayMatches =
        !fullPrevGray.empty() &&
        fullPrevGray.size() == gray.size() &&
        fullPrevGray.type() == gray.type();

    if (!prevGray.empty() && !prevGrayMatches) {
        prevPts.clear();
        lostCount = 0;
    }

    cv::Rect2d cand;
    bool didKLT = false;

    // Try KLT-based drift
    if (prevGrayMatches && !prevPts.empty()) {
        std::vector<cv::Point2f> currPts;
        std::vector<uchar> status;
        std::vector<float> err;
        cv::calcOpticalFlowPyrLK(
            prevGray, gray,
            prevPts, currPts,
            status, err,
            cv::Size(21,21), 3,
            cv::TermCriteria{cv::TermCriteria::COUNT|cv::TermCriteria::EPS,30,0.01},
            cv::OPTFLOW_LK_GET_MIN_EIGENVALS, 1e-4
        );

        // collect per-point displacements
        std::vector<double> dx, dy;
        for (size_t i = 0; i < status.size(); ++i) {
            if (status[i] && err[i] < 12.0) {
                dx.push_back(currPts[i].x - prevPts[i].x);
                dy.push_back(currPts[i].y - prevPts[i].y);
            }
        }

        if ((int)dx.size() >= minKltPts) {
            auto median = [&](auto &v){