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Implemented new algorithm for asymmetric circles pattern detection. Use flag CALIB_CB_CLUSTERING.

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This commit is contained in:
Ilya Lysenkov
2011-04-15 15:33:11 +00:00
parent 2c8af20bd0
commit 37cd2b6f25
4 changed files with 290 additions and 2 deletions
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3
modules/calib3d/include/opencv2/calib3d/calib3d.hpp
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@@ -560,7 +560,8 @@ CV_EXPORTS void drawChessboardCorners( Mat& image, Size patternSize,
const vector<Point2f>& corners,
bool patternWasFound );
enum { CALIB_CB_SYMMETRIC_GRID = 1, CALIB_CB_ASYMMETRIC_GRID = 2 };
enum { CALIB_CB_SYMMETRIC_GRID = 1, CALIB_CB_ASYMMETRIC_GRID = 2,
CALIB_CB_CLUSTERING = 4, CALIB_CB_WHITE_CIRCLES = 8 };
//! finds circles' grid pattern of the specified size in the image
CV_EXPORTS_W bool findCirclesGrid( const Mat& image, Size patternSize,

15
modules/calib3d/src/calibinit.cpp
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@@ -1937,7 +1937,13 @@ void drawChessboardCorners( Mat& image, Size patternSize,
bool findCirclesGrid( const Mat& image, Size patternSize,
vector<Point2f>& centers, int flags )
{
Ptr<SimpleBlobDetector> detector = new SimpleBlobDetector();
SimpleBlobDetector::Params params;
if(flags & CALIB_CB_WHITE_CIRCLES)
{
params.filterByColor = true;
params.blobColor = 255;
}
Ptr<SimpleBlobDetector> detector = new SimpleBlobDetector(params);
//Ptr<FeatureDetector> detector = new MserFeatureDetector();
vector<KeyPoint> keypoints;
detector->detect(image, keypoints);
@@ -1947,6 +1953,13 @@ bool findCirclesGrid( const Mat& image, Size patternSize,
points.push_back (keypoints[i].pt);
}
if((flags & CALIB_CB_CLUSTERING) && (flags & CALIB_CB_ASYMMETRIC_GRID))
{
CirclesGridClusterFinder circlesGridClusterFinder;
circlesGridClusterFinder.findGrid(points, patternSize, centers);
return !centers.empty();
}
CirclesGridFinderParameters parameters;
parameters.vertexPenalty = -0.6f;
parameters.vertexGain = 1;

250
modules/calib3d/src/circlesgrid.cpp
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@@ -43,9 +43,259 @@
#include "circlesgrid.hpp"
//#define DEBUG_CIRCLES
#ifdef DEBUG_CIRCLES
#include <opencv2/highgui/highgui.hpp>
#endif
using namespace cv;
using namespace std;
void CirclesGridClusterFinder::hierarchicalClustering(const vector<Point2f> points, const Size &patternSize, vector<Point2f> &patternPoints)
{
Mat dists(points.size(), points.size(), CV_32FC1, Scalar(0));
Mat distsMask(dists.size(), CV_8UC1, Scalar(0));
for(size_t i=0; i<points.size(); i++)
{
for(size_t j=i+1; j<points.size(); j++)
{
dists.at<float>(i, j) = norm(points[i] - points[j]);
distsMask.at<uchar>(i, j) = 255;
//TODO: use symmetry
distsMask.at<uchar>(j, i) = distsMask.at<uchar>(i, j);
dists.at<float>(j, i) = dists.at<float>(i, j);
}
}
vector<std::list<size_t> > clusters(points.size());
for(size_t i=0; i<points.size(); i++)
{
clusters[i].push_back(i);
}
int patternClusterIdx = 0;
while(clusters[patternClusterIdx].size() < patternSize.area() && countNonZero(distsMask == 255) > 0)
{
Point minLoc;
minMaxLoc(dists, 0, 0, &minLoc, 0, distsMask);
int minIdx = std::min(minLoc.x, minLoc.y);
int maxIdx = std::max(minLoc.x, minLoc.y);
distsMask.row(maxIdx).setTo(0);
distsMask.col(maxIdx).setTo(0);
Mat newDists = cv::min(dists.row(minLoc.x), dists.row(minLoc.y));
Mat tmpLine = dists.row(minIdx);
newDists.copyTo(tmpLine);
tmpLine = dists.col(minIdx);
newDists.copyTo(tmpLine);
clusters[minIdx].splice(clusters[minIdx].end(), clusters[maxIdx]);
patternClusterIdx = minIdx;
}
patternPoints.clear();
if(clusters[patternClusterIdx].size() != patternSize.area())
{
return;
}
patternPoints.reserve(clusters[patternClusterIdx].size());
for(std::list<size_t>::iterator it = clusters[patternClusterIdx].begin(); it != clusters[patternClusterIdx].end(); it++)
{
patternPoints.push_back(points[*it]);
}
}
void CirclesGridClusterFinder::findGrid(const std::vector<cv::Point2f> points, cv::Size patternSize, vector<Point2f>& centers)
{
centers.clear();
vector<Point2f> patternPoints;
hierarchicalClustering(points, patternSize, patternPoints);
if(patternPoints.empty())
{
return;
}
vector<Point2f> hull2f;
convexHull(Mat(patternPoints), hull2f, false);
vector<Point2f> corners;
findCorners(hull2f, corners);
vector<Point2f> outsideCorners;
findOutsideCorners(corners, outsideCorners);
vector<Point2f> sortedCorners;
getSortedCorners(hull2f, corners, outsideCorners, sortedCorners);
vector<Point2f> rectifiedPatternPoints;
rectifyPatternPoints(patternSize, patternPoints, sortedCorners, rectifiedPatternPoints);
parsePatternPoints(patternSize, patternPoints, rectifiedPatternPoints, centers);
}
void CirclesGridClusterFinder::findCorners(const std::vector<cv::Point2f> &hull2f, std::vector<cv::Point2f> &corners)
{
//find angles (cosines) of vertices in convex hull
vector<float> angles;
for(size_t i=0; i<hull2f.size(); i++)
{
Point2f vec1 = hull2f[(i+1) % hull2f.size()] - hull2f[i % hull2f.size()];
Point2f vec2 = hull2f[(i-1 + static_cast<int>(hull2f.size())) % hull2f.size()] - hull2f[i % hull2f.size()];
float angle = vec1.ddot(vec2) / (norm(vec1) * norm(vec2));
angles.push_back(angle);
}
//sort angles by cosine
//corners are the most sharp angles (6)
Mat anglesMat = Mat(angles);
Mat sortedIndices;
sortIdx(anglesMat, sortedIndices, CV_SORT_EVERY_COLUMN + CV_SORT_DESCENDING);
CV_Assert(sortedIndices.type() == CV_32SC1);
const int cornersCount = 6;
corners.clear();
for(int i=0; i<cornersCount; i++)
{
corners.push_back(hull2f[sortedIndices.at<int>(i, 0)]);
}
}
void CirclesGridClusterFinder::findOutsideCorners(const std::vector<cv::Point2f> &corners, std::vector<cv::Point2f> &outsideCorners)
{
//find two pairs of the most nearest corners
double min1 = std::numeric_limits<double>::max();
double min2 = std::numeric_limits<double>::max();
Point minLoc1, minLoc2;
for(size_t i=0; i<corners.size(); i++)
{
for(size_t j=i+1; j<corners.size(); j++)
{
double dist = norm(corners[i] - corners[j]);
Point loc(j, i);
if(dist < min1)
{
min2 = min1;
minLoc2 = minLoc1;
min1 = dist;
minLoc1 = loc;
}
else
{
if(dist < min2)
{
min2 = dist;
minLoc2 = loc;
}
}
}
}
std::set<int> outsideCornersIndices;
for(size_t i=0; i<corners.size(); i++)
{
outsideCornersIndices.insert(i);
}
outsideCornersIndices.erase(minLoc1.x);
outsideCornersIndices.erase(minLoc1.y);
outsideCornersIndices.erase(minLoc2.x);
outsideCornersIndices.erase(minLoc2.y);
outsideCorners.clear();
for(std::set<int>::iterator it = outsideCornersIndices.begin(); it != outsideCornersIndices.end(); it++)
{
outsideCorners.push_back(corners[*it]);
}
}
void CirclesGridClusterFinder::getSortedCorners(const std::vector<cv::Point2f> &hull2f, const std::vector<cv::Point2f> &corners, const std::vector<cv::Point2f> &outsideCorners, std::vector<cv::Point2f> &sortedCorners)
{
Point2f center = std::accumulate(corners.begin(), corners.end(), Point2f(0.0f, 0.0f));
center *= 1.0 / corners.size();
vector<Point2f> centerToCorners;
for(size_t i=0; i<outsideCorners.size(); i++)
{
centerToCorners.push_back(outsideCorners[i] - center);
}
//TODO: use CirclesGridFinder::getDirection
float crossProduct = centerToCorners[0].x * centerToCorners[1].y - centerToCorners[0].y * centerToCorners[1].x;
//y axis is inverted in computer vision so we check > 0
bool isClockwise = crossProduct > 0;
Point2f firstCorner = isClockwise ? outsideCorners[1] : outsideCorners[0];
std::vector<Point2f>::const_iterator firstCornerIterator = std::find(hull2f.begin(), hull2f.end(), firstCorner);
sortedCorners.clear();
for(vector<Point2f>::const_iterator it = firstCornerIterator; it != hull2f.end(); it++)
{
vector<Point2f>::const_iterator itCorners = std::find(corners.begin(), corners.end(), *it);
if(itCorners != corners.end())
{
sortedCorners.push_back(*it);
}
}
for(vector<Point2f>::const_iterator it = hull2f.begin(); it != firstCornerIterator; it++)
{
vector<Point2f>::const_iterator itCorners = std::find(corners.begin(), corners.end(), *it);
if(itCorners != corners.end())
{
sortedCorners.push_back(*it);
}
}
}
void CirclesGridClusterFinder::rectifyPatternPoints(const cv::Size &patternSize, const std::vector<cv::Point2f> &patternPoints, const std::vector<cv::Point2f> &sortedCorners, std::vector<cv::Point2f> &rectifiedPatternPoints)
{
//indices of corner points in pattern
vector<Point> trueIndices;
trueIndices.push_back(Point(0, 0));
trueIndices.push_back(Point(patternSize.width - 1, 0));
trueIndices.push_back(Point(patternSize.width - 1, 1));
trueIndices.push_back(Point(patternSize.width - 1, patternSize.height - 2));
trueIndices.push_back(Point(patternSize.width - 1, patternSize.height - 1));
trueIndices.push_back(Point(0, patternSize.height - 1));
vector<Point2f> idealPoints;
for(size_t idx=0; idx<trueIndices.size(); idx++)
{
int i = trueIndices[idx].y;
int j = trueIndices[idx].x;
idealPoints.push_back(Point2f((2*j + i % 2)*squareSize, i*squareSize));
}
Mat homography = findHomography(Mat(sortedCorners), Mat(idealPoints), 0);
Mat rectifiedPointsMat;
transform(Mat(patternPoints), rectifiedPointsMat, homography);
rectifiedPatternPoints.clear();
convertPointsHomogeneous(rectifiedPointsMat, rectifiedPatternPoints);
}
void CirclesGridClusterFinder::parsePatternPoints(const cv::Size &patternSize, const std::vector<cv::Point2f> &patternPoints, const std::vector<cv::Point2f> &rectifiedPatternPoints, std::vector<cv::Point2f> &centers)
{
flann::LinearIndexParams flannIndexParams;
flann::Index flannIndex(Mat(rectifiedPatternPoints).reshape(1), flannIndexParams);
centers.clear();
for( int i = 0; i < patternSize.height; i++ )
{
for( int j = 0; j < patternSize.width; j++ )
{
Point2f idealPt((2*j + i % 2)*squareSize, i*squareSize);
vector<float> query = Mat(idealPt);
int knn = 1;
vector<int> indices(knn);
vector<float> dists(knn);
flannIndex.knnSearch(query, indices, dists, knn, flann::SearchParams());
centers.push_back(patternPoints.at(indices[0]));
if(dists[0] > maxRectifiedDistance)
{
centers.clear();
return;
}
}
}
}
Graph::Graph(size_t n)
{
for (size_t i = 0; i < n; i++)

24
modules/calib3d/src/circlesgrid.hpp
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@@ -45,9 +45,33 @@
#include <fstream>
#include <set>
#include <list>
#include <numeric>
#include "precomp.hpp"
class CirclesGridClusterFinder
{
public:
CirclesGridClusterFinder()
{
squareSize = 1.0f;
maxRectifiedDistance = squareSize / 2.0;
}
void findGrid(const std::vector<cv::Point2f> points, cv::Size patternSize, std::vector<cv::Point2f>& centers);
//cluster 2d points by geometric coordinates
void hierarchicalClustering(const std::vector<cv::Point2f> points, const cv::Size &patternSize, std::vector<cv::Point2f> &patternPoints);
private:
void findCorners(const std::vector<cv::Point2f> &hull2f, std::vector<cv::Point2f> &corners);
void findOutsideCorners(const std::vector<cv::Point2f> &corners, std::vector<cv::Point2f> &outsideCorners);
void getSortedCorners(const std::vector<cv::Point2f> &hull2f, const std::vector<cv::Point2f> &corners, const std::vector<cv::Point2f> &outsideCorners, std::vector<cv::Point2f> &sortedCorners);
void rectifyPatternPoints(const cv::Size &patternSize, const std::vector<cv::Point2f> &patternPoints, const std::vector<cv::Point2f> &sortedCorners, std::vector<cv::Point2f> &rectifiedPatternPoints);
void parsePatternPoints(const cv::Size &patternSize, const std::vector<cv::Point2f> &patternPoints, const std::vector<cv::Point2f> &rectifiedPatternPoints, std::vector<cv::Point2f> &centers);
float squareSize, maxRectifiedDistance;
};
class Graph
{
public: