highlyreliablemarkers.cpp

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/*****************************
Copyright 2011 Rafael Muñoz Salinas. All rights reserved.

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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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********************************/

#include "highlyreliablemarkers.h"
#include <iostream>
using namespace std;

namespace aruco {

// static variables from HighlyReliableMarkers. Need to be here to avoid linking errors
Dictionary HighlyReliableMarkers::_D;
HighlyReliableMarkers::BalancedBinaryTree HighlyReliableMarkers::_binaryTree;
unsigned int HighlyReliableMarkers::_n, HighlyReliableMarkers::_ncellsBorder, HighlyReliableMarkers::_correctionDistance;
int HighlyReliableMarkers::_swidth;


MarkerCode::MarkerCode(unsigned int n) {
    // resize bits vectors and initialize to 0
    for (unsigned int i = 0; i < 4; i++) {
        _bits[i].resize(n * n);
        for (unsigned int j = 0; j < _bits[i].size(); j++)
            _bits[i][j] = 0;
        _ids[i] = 0; // ids are also 0
    }
    _n = n;
};


MarkerCode::MarkerCode(const MarkerCode &MC) {
    for (unsigned int i = 0; i < 4; i++) {
        _bits[i] = MC._bits[i];
        _ids[i] = MC._ids[i];
    }
    _n = MC._n;
}



void MarkerCode::set(unsigned int pos, bool val, bool updateIds) {
    // if not the same value
    if (get(pos) != val) {
        for (unsigned int i = 0; i < 4; i++) {         // calculate bit coordinates for each rotation
            unsigned int y = pos / n(), x = pos % n(); // if rotation 0, dont do anything
                                                       // else calculate bit position in that rotation
            if (i == 1) {
                unsigned int aux = y;
                y = x;
                x = n() - aux - 1;
            } else if (i == 2) {
                y = n() - y - 1;
                x = n() - x - 1;
            } else if (i == 3) {
                unsigned int aux = y;
                y = n() - x - 1;
                x = aux;
            }
            unsigned int rotPos = y * n() + x; // calculate position in the unidimensional string
            _bits[i][rotPos] = val;            // modify value
                                               // update identifier in that rotation
            if(updateIds) {
                if (val == true)
                    _ids[i] += (unsigned int)pow(float(2), float(rotPos)); // if 1, add 2^pos
                else
                    _ids[i] -= (unsigned int)pow(float(2), float(rotPos)); // if 0, substract 2^pos
            }
        }
    }
}


unsigned int MarkerCode::selfDistance(unsigned int &minRot) const {
    unsigned int res = _bits[0].size();    // init to n*n (max value)
    for (unsigned int i = 1; i < 4; i++) { // self distance is not calculated for rotation 0
        unsigned int hammdist = hammingDistance(_bits[0], _bits[i]);
        if (hammdist < res) {
            minRot = i;
            res = hammdist;
        }
    }
    return res;
}


unsigned int MarkerCode::distance(const MarkerCode &m, unsigned int &minRot) const {
    unsigned int res = _bits[0].size(); // init to n*n (max value)
    for (unsigned int i = 0; i < 4; i++) {
        unsigned int hammdist = hammingDistance(_bits[0], m.getRotation(i));
        if (hammdist < res) {
            minRot = i;
            res = hammdist;
        }
    }
    return res;
};


void MarkerCode::fromString(std::string s) {
    for (unsigned int i = 0; i < s.length(); i++) {
        if (s[i] == '0')
            set(i, false);
        else
            set(i, true);
    }
}

std::string MarkerCode::toString() const {
    std::string s;
    s.resize(size());
    for (unsigned int i = 0; i < size(); i++) {
        if (get(i))
            s[i] = '1';
        else
            s[i] = '0';
    }
    return s;
}


cv::Mat MarkerCode::getImg(unsigned int pixSize) const {
    const unsigned int borderSize = 1;
    unsigned int nrows = n() + 2 * borderSize;
    if (pixSize % nrows != 0)
        pixSize = pixSize + nrows - pixSize % nrows;
    unsigned int cellSize = pixSize / nrows;
    cv::Mat img(pixSize, pixSize, CV_8U, cv::Scalar::all(0)); // create black image (init image to 0s)
    // double for to go over all the cells
    for (unsigned int i = 0; i < n(); i++) {
        for (unsigned int j = 0; j < n(); j++) {
            if (_bits[0][i * n() + j] != 0) { // just draw if it is 1, since the image has been init to 0
                                              // double for to go over all the pixels in the cell
                for (unsigned int k = 0; k < cellSize; k++) {
                    for (unsigned int l = 0; l < cellSize; l++) {
                        img.at< uchar >((i + borderSize) * cellSize + k, (j + borderSize) * cellSize + l) = 255;
                    }
                }
            }
        }
    }
    return img;
}


unsigned int MarkerCode::hammingDistance(const std::vector< bool > &m1, const std::vector< bool > &m2) const {
    unsigned int res = 0;
    for (unsigned int i = 0; i < m1.size(); i++)
        if (m1[i] != m2[i])
            res++;
    return res;
}




bool Dictionary::fromFile(std::string filename) {
    cv::FileStorage fs(filename, cv::FileStorage::READ);
    int nmarkers, markersize;

    // read number of markers
    fs["nmarkers"] >> nmarkers;                     // cardinal of D
    fs["markersize"] >> markersize;                 // n
    fs["tau0"] >> tau0;

    // read each marker info
    for (int i = 0; i < nmarkers; i++) {
        std::string s;
        fs["marker_" + toStr(i)] >> s;
        MarkerCode m(markersize);
        m.fromString(s);
        push_back(m);
    }
    fs.release();
    return true;
};

bool Dictionary::toFile(std::string filename) {
    cv::FileStorage fs(filename, cv::FileStorage::WRITE);
    // save number of markers
    fs << "nmarkers" << (int)size();                               // cardinal of D
    fs << "markersize" << (int)((*this)[0].n());                   // n
    fs << "tau0" << (int)(this->tau0); // n
    // save each marker code
    for (unsigned int i = 0; i < size(); i++) {
        std::string s = ((*this)[i]).toString();
        fs << "marker_" + toStr(i) << s;
    }
    fs.release();
    return true;
};

unsigned int Dictionary::distance(const MarkerCode &m, unsigned int &minMarker, unsigned int &minRot) {
    unsigned int res = m.size();
    for (unsigned int i = 0; i < size(); i++) {
        unsigned int minRotAux;
        unsigned int distance = (*this)[i].distance(m, minRotAux);
        if (distance < res) {
            minMarker = i;
            minRot = minRotAux;
            res = distance;
        }
    }
    return res;
}


unsigned int Dictionary::minimunDistance() {
    if (size() == 0)
        return 0;
    unsigned int minDist = (*this)[0].size();
    // for each marker in D
    for (unsigned int i = 0; i < size(); i++) {
        // calculate self distance of the marker
        minDist = std::min(minDist, (*this)[i].selfDistance());

        // calculate distance to all the following markers
        for (unsigned int j = i + 1; j < size(); j++) {
            minDist = std::min(minDist, (*this)[i].distance((*this)[j]));
        }
    }
    return minDist;
}




bool HighlyReliableMarkers::loadDictionary(Dictionary D, float correctionDistanceRate) {
    if (D.size() == 0)
        return false;
    _D = D;
    _n = _D[0].n();
    _ncellsBorder = (_D[0].n() + 2);
    _correctionDistance = correctionDistanceRate * ((D.tau0-1)/2);
    cerr << "aruco :: _correctionDistance = " << _correctionDistance << endl;
    _binaryTree.loadDictionary(&D);
    return true;
}

bool HighlyReliableMarkers::loadDictionary(std::string filename, float correctionDistance) {
    Dictionary D;
    D.fromFile(filename);
    return loadDictionary(D, correctionDistance);
}


int HighlyReliableMarkers::detect(const cv::Mat &in, int &nRotations) {

    assert(in.rows == in.cols);
    cv::Mat grey;
    if (in.type() == CV_8UC1)
        grey = in;
    else
        cv::cvtColor(in, grey, CV_BGR2GRAY);
    // threshold image
    cv::threshold(grey, grey, 125, 255, cv::THRESH_BINARY | cv::THRESH_OTSU);
    _swidth = grey.rows / _ncellsBorder;

    // check borders, even not necesary for the highly reliable markers
    // if(!checkBorders(grey)) return -1;

    // obtain inner code
    MarkerCode candidate = getMarkerCode(grey);

    // search each marker id in the balanced binary tree
    unsigned int orgPos;
    for (unsigned int i = 0; i < 4; i++) {
        if (_binaryTree.findId(candidate.getId(i), orgPos)) {
            nRotations = i;
            // return candidate.getId(i);
            return orgPos;
        }
    }

    // alternative version without using the balanced binary tree (less eficient)
    //         for(uint i=0; i<_D.size(); i++) {
    //           for(uint j=0; j<4; j++) {
    //        if(_D[i].getId() == candidate.getId(j)) {
    //          nRotations = j;
    //          //return candidate.getId(j);
    //          return i;
    //        }
    //           }
    //         }

    // correct errors
    unsigned int minMarker, minRot;
    if (_D.distance(candidate, minMarker, minRot) <= _correctionDistance) {
        nRotations = minRot;
        return minMarker;
        // return _D[minMarker].getId();
    }

    return -1;
}


bool HighlyReliableMarkers::checkBorders(cv::Mat grey) {
    for (int y = 0; y < _ncellsBorder; y++) {
        int inc = _ncellsBorder - 1;
        if (y == 0 || y == _ncellsBorder - 1)
            inc = 1; // for first and last row, check the whole border
        for (int x = 0; x < _ncellsBorder; x += inc) {
            int Xstart = (x) * (_swidth);
            int Ystart = (y) * (_swidth);
            cv::Mat square = grey(cv::Rect(Xstart, Ystart, _swidth, _swidth));
            int nZ = cv::countNonZero(square);
            if (nZ > (_swidth * _swidth) / 2) {
                return false; // can not be a marker because the border element is not black!
            }
        }
    }
    return true;
}

MarkerCode HighlyReliableMarkers::getMarkerCode(const cv::Mat &grey) {
    MarkerCode candidate(_n);
    for (int y = 0; y < _n; y++) {
        for (int x = 0; x < _n; x++) {
            int Xstart = (x + 1) * (_swidth);
            int Ystart = (y + 1) * (_swidth);
            cv::Mat square = grey(cv::Rect(Xstart, Ystart, _swidth, _swidth));
            int nZ = countNonZero(square);
            if (nZ > (_swidth * _swidth) / 2)
                candidate.set(y * _n + x, 1);
        }
    }
    return candidate;
}



void HighlyReliableMarkers::BalancedBinaryTree::loadDictionary(Dictionary *D) {
    // create _orderD wich is a sorted version of D
    _orderD.clear();
    for (unsigned int i = 0; i < D->size(); i++) {
        _orderD.push_back(std::pair< unsigned int, unsigned int >((*D)[i].getId(), i));
    }
    std::sort(_orderD.begin(), _orderD.end());

    // calculate the number of levels of the tree
    unsigned int levels = 0;
    while (pow(float(2), float(levels)) <= _orderD.size())
        levels++;
    //       levels-=1; // only count full levels

    // auxiliar vector to know which elements are already in the tree
    std::vector< bool > visited;
    visited.resize(_orderD.size(), false);

    // calculate position of the root element
    unsigned int rootIdx = _orderD.size() / 2;
    visited[rootIdx] = true; // mark it as visited
    _root = rootIdx;

    //    for(int i=0; i<visited.size(); i++) std::cout << visited[i] << std::endl;

    // auxiliar vector to store the ids intervals (max and min) during the creation of the tree
    std::vector< std::pair< unsigned int, unsigned int > > intervals;
    // first, add the two intervals at each side of root element
    intervals.push_back(std::pair< unsigned int, unsigned int >(0, rootIdx));
    intervals.push_back(std::pair< unsigned int, unsigned int >(rootIdx, _orderD.size()));

    // init the tree
    _binaryTree.clear();
    _binaryTree.resize(_orderD.size());

    // add root information to the tree (make sure child do not coincide with self root for small sizes of D)
    if (!visited[(0 + rootIdx) / 2])
        _binaryTree[rootIdx].first = (0 + rootIdx) / 2;
    else
        _binaryTree[rootIdx].first = -1;
    if (!visited[(rootIdx + _orderD.size()) / 2])
        _binaryTree[rootIdx].second = (rootIdx + _orderD.size()) / 2;
    else
        _binaryTree[rootIdx].second = -1;

    // for each tree level
    for (unsigned int i = 1; i < levels; i++) {
        unsigned int nintervals = intervals.size(); // count number of intervals and process them
        for (unsigned int j = 0; j < nintervals; j++) {
            // store interval information and delete it
            unsigned int lowerBound, higherBound;
            lowerBound = intervals.back().first;
            higherBound = intervals.back().second;
            intervals.pop_back();

            // center of the interval
            unsigned int center = (higherBound + lowerBound) / 2;

            // if center not visited, continue
            if (!visited[center])
                visited[center] = true;
            else
                continue;

            // calculate centers of the child intervals
            unsigned int lowerChild = (lowerBound + center) / 2;
            unsigned int higherChild = (center + higherBound) / 2;

            // if not visited (lower child)
            if (!visited[lowerChild]) {
                intervals.insert(intervals.begin(), std::pair< unsigned int, unsigned int >(lowerBound, center)); // add the interval to analyze later
                _binaryTree[center].first = lowerChild;                                                           // add as a child in the tree
            } else
                _binaryTree[center].first = -1; // if not, mark as no child

            // (higher child, same as lower child)
            if (!visited[higherChild]) {
                intervals.insert(intervals.begin(), std::pair< unsigned int, unsigned int >(center, higherBound));
                _binaryTree[center].second = higherChild;
            } else
                _binaryTree[center].second = -1;
        }
    }

    // print tree
    //     for(uint i=0; i<_binaryTree.size(); i++) std::cout << _binaryTree[i].first << " " << _binaryTree[i].second << std::endl;
    //     std::cout << std::endl;
}


int count = 0;
int idc = 11;

bool HighlyReliableMarkers::BalancedBinaryTree::findId(unsigned int id, unsigned int &orgPos) {
    int pos = _root;                             // first position is root
    while (pos != -1) {                          // while having a valid position
        unsigned int posId = _orderD[pos].first; // calculate id of the node
        if (posId == id) {
            orgPos = _orderD[pos].second;
            return true; // if is the desire id, return true
        } else if (posId < id)
            pos = _binaryTree[pos].second; // if desired id is higher, look in higher child
        else
            pos = _binaryTree[pos].first; // if it is lower, look in lower child
    }
    count++;
    return false; // if nothing found, return false
}
}