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// Determine mask based on positive monotony of phase in each row

inline void phaseMonotonyMask(cv::Mat& up, cv::Mat& mask){

    int nRows = up.rows;

    int nCols = up.cols;

    mask.create(nRows, nCols, CV_8UC1);

    mask.setTo(0);

    for(int r=0; r<nRows; r++){

        cv::Mat upRow = up.row(r);

        std::vector<int> b;

        //std::vector<float> lit;

        cv::Mat litMask(1, upRow.cols, CV_8UC1);

        litMask.setTo(0);

        // step 1: find longest increasing subsequence, (c) http://www.algorithmist.com

        std::vector<int> p(upRow.cols);

        int u, v;

        b.push_back(0);

        for(int i = 1; i < upRow.cols; i++){

            // If next element a[i] is greater than last element of

            // current longest subsequence, just push it at back of "b" and continue

            if (upRow.at<float>(0, b.back()) < upRow.at<float>(0, i)){

                p[i] = b.back();

                b.push_back(i);

                continue;

            }

            // Binary search to find the smallest element referenced by b which is just bigger than upRow[i]

            for(u = 0, v = b.size()-1; u < v;){

                int c = (u + v) / 2;

                if(upRow.at<float>(0, b[c]) < upRow.at<float>(0, i))

                    u = c+1;

                else

                    v = c;

            }

            // Update b if new value is smaller then previously referenced value

            if (upRow.at<float>(0, i) < upRow.at<float>(0, b[u])){

                if (u > 0) p[i] = b[u-1];

                b[u] = i;

            }

        }

        //lit.resize(b.size());

        for (u = b.size(), v = b.back(); u--; v = p[v]){

            litMask.at<uchar>(0, v) = 255;

            //lit[u] = v;

        }

        litMask.copyTo(mask.row(r));

    }

    return;

}