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(3.4) aruco: shift corner positions to the correct rotation (backport #2372) #2374

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Dec 5, 2019
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(3.4) aruco: shift corner positions to the correct rotation (backport #2372) #2374

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62 changes: 41 additions & 21 deletions modules/aruco/src/aruco.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -210,6 +210,22 @@ static void _reorderCandidatesCorners(vector< vector< Point2f > > &candidates) {
}
}

/**
* @brief to make sure that the corner's order of both candidates (default/white) is the same
*/
static vector< Point2f > alignContourOrder( Point2f corner, vector< Point2f > candidate){
uint8_t r=0;
double min = cv::norm( Vec2f( corner - candidate[0] ), NORM_L2SQR);
for(uint8_t pos=1; pos < 4; pos++) {
double nDiff = cv::norm( Vec2f( corner - candidate[pos] ), NORM_L2SQR);
if(nDiff < min){
r = pos;
min =nDiff;
}
}
std::rotate(candidate.begin(), candidate.begin() + r, candidate.end());
return candidate;
}

/**
* @brief Check candidates that are too close to each other, save the potential candidates
Expand Down Expand Up @@ -315,7 +331,7 @@ static void _filterTooCloseCandidates(const vector< vector< Point2f > > &candida
biggerContours.push_back(contoursIn[biggerIdx]);

if( detectInvertedMarker ){
smallerCandidates.push_back(candidatesIn[smallerIdx]);
smallerCandidates.push_back(alignContourOrder(candidatesIn[biggerIdx][0], candidatesIn[smallerIdx]));
smallerContours.push_back(contoursIn[smallerIdx]);
}
}
Expand Down Expand Up @@ -550,7 +566,7 @@ static int _getBorderErrors(const Mat &bits, int markerSize, int borderSize) {
*/
static uint8_t _identifyOneCandidate(const Ptr<Dictionary>& dictionary, InputArray _image,
vector<Point2f>& _corners, int& idx,
const Ptr<DetectorParameters>& params)
const Ptr<DetectorParameters>& params, int& rotation)
{
CV_Assert(_corners.size() == 4);
CV_Assert(_image.getMat().total() != 0);
Expand Down Expand Up @@ -590,14 +606,9 @@ static uint8_t _identifyOneCandidate(const Ptr<Dictionary>& dictionary, InputArr
.colRange(params->markerBorderBits, candidateBits.rows - params->markerBorderBits);

// try to indentify the marker
int rotation;
if(!dictionary->identify(onlyBits, idx, rotation, params->errorCorrectionRate))
return 0;

// shift corner positions to the correct rotation
if(rotation != 0) {
std::rotate(_corners.begin(), _corners.begin() + 4 - rotation, _corners.end());
}
return typ;
}

Expand All @@ -611,9 +622,10 @@ class IdentifyCandidatesParallel : public ParallelLoopBody {
IdentifyCandidatesParallel(const Mat& _grey, vector< vector< Point2f > >& _candidates,
const Ptr<Dictionary> &_dictionary,
vector< int >& _idsTmp, vector< uint8_t >& _validCandidates,
const Ptr<DetectorParameters> &_params)
const Ptr<DetectorParameters> &_params,
vector< int > &_rotated)
: grey(_grey), candidates(_candidates), dictionary(_dictionary),
idsTmp(_idsTmp), validCandidates(_validCandidates), params(_params) {}
idsTmp(_idsTmp), validCandidates(_validCandidates), params(_params), rotated(_rotated) {}

void operator()(const Range &range) const CV_OVERRIDE
{
Expand All @@ -622,7 +634,7 @@ class IdentifyCandidatesParallel : public ParallelLoopBody {

for(int i = begin; i < end; i++) {
int currId;
validCandidates[i] = _identifyOneCandidate(dictionary, grey, candidates[i], currId, params);
validCandidates[i] = _identifyOneCandidate(dictionary, grey, candidates[i], currId, params, rotated[i]);

if(validCandidates[i] > 0)
idsTmp[i] = currId;
Expand All @@ -639,6 +651,7 @@ class IdentifyCandidatesParallel : public ParallelLoopBody {
vector< int > &idsTmp;
vector< uint8_t > &validCandidates;
const Ptr<DetectorParameters> &params;
vector< int > &rotated;
};


Expand Down Expand Up @@ -676,7 +689,12 @@ static void _copyVector2Output(vector< vector< Point2f > > &vec, OutputArrayOfAr
}
}


/**
* @brief rotate the initial corner to get to the right position
*/
static void correctCornerPosition( vector< Point2f >& _candidate, int rotate){
std::rotate(_candidate.begin(), _candidate.begin() + 4 - rotate, _candidate.end());
}

/**
* @brief Identify square candidates according to a marker dictionary
Expand All @@ -699,30 +717,32 @@ static void _identifyCandidates(InputArray _image, vector< vector< vector< Point
_convertToGrey(_image.getMat(), grey);

vector< int > idsTmp(ncandidates, -1);
vector< int > rotated(ncandidates, 0);
vector< uint8_t > validCandidates(ncandidates, 0);

//// Analyze each of the candidates
parallel_for_(Range(0, ncandidates),
IdentifyCandidatesParallel(grey,
params->detectInvertedMarker ? _candidatesSet[1] : _candidatesSet[0],
_dictionary, idsTmp,
validCandidates, params));
validCandidates, params, rotated));

for(int i = 0; i < ncandidates; i++) {
if(validCandidates[i] > 0) {
// add the white valid candidate
if( params->detectInvertedMarker && validCandidates[i] == 2 ){
accepted.push_back(_candidatesSet[1][i]);
ids.push_back(idsTmp[i]);
// to choose the right set of candidates :: 0 for default, 1 for white markers
uint8_t set = validCandidates[i]-1;

contours.push_back(_contoursSet[1][i]);
// shift corner positions to the correct rotation
correctCornerPosition(_candidatesSet[set][i], rotated[i]);

if( !params->detectInvertedMarker && validCandidates[i] == 2 )
continue;
}
// add the default (black) valid candidate
accepted.push_back(_candidatesSet[0][i]);

// add valid candidate
accepted.push_back(_candidatesSet[set][i]);
ids.push_back(idsTmp[i]);

contours.push_back(_contoursSet[0][i]);
contours.push_back(_contoursSet[set][i]);

} else {
rejected.push_back(_candidatesSet[0][i]);
Expand Down