bool ImageTransformation::findHomography( const Keypoints& source, const Keypoints& result, const Matches& input, Matches& inliers, cv::Mat& homography)
{
if (input.size() < 8)
return false;
std::vector<cv::Point2f> srcPoints, dstPoints;
const int pointsCount = input.size();
for (int i=0; i<pointsCount; i++)
{
srcPoints.push_back(source[input[i].trainIdx].pt);
dstPoints.push_back(result[input[i].queryIdx].pt);
}
std::vector<unsigned char> status;
cv::findHomography(srcPoints, dstPoints, CV_FM_RANSAC, 3, status);
inliers.clear();
for (int i=0; i<pointsCount; i++)
{
if (status[i])
{
inliers.push_back(input[i]);
}
}
return true;
}
/*
* Find the closest match in db, return as element of matches
*/
void SemanticDescriptor::findClosestMatch(Database & db, Matches & matches)
{
SemanticDescriptor bestMatch = (*(db.dDB.begin())).first;
//matches.insert((*(db.dDB.begin())).second);
SemanticDescriptor compareID;
int matchStrength;
map<SemanticDescriptor, string>::iterator iter;
for (iter = db.dDB.begin(); iter != db.dDB.end(); ++iter) {
compareID = iter->first;
matchStrength = closerMatch(compareID, bestMatch, db);
/* If compareID is a better match, reset matches */
if (matchStrength > 0)
if (compareID.coverage(*this, db) >= .5) {
matches.clear();
matches.insert(iter->second);
bestMatch = compareID;
}
/* If compareID is an equal match, then add it to the set of matches */
if (matchStrength == 0)
if (compareID.coverage(*this, db) >= .5)
matches.insert(iter->second);
}
}
bool HybridTracker::Localize(const Marker& target, const Frame& scene, Matches& out) {
vector<cv::DMatch> matches;
methods.Match(target.descriptor, scene.descriptor, matches);
out.clear();
for(auto& it : matches) {
out._targetPts.push_back(target.keys[it.queryIdx]);
out._scenePts.push_back(scene.keys[it.trainIdx]);
out._error.push_back(it.distance);
}
return matches.size() > 20;
}
void ratioTest(const std::vector<Matches>& knMatches, float maxRatio, Matches& goodMatches)
{
goodMatches.clear();
for (size_t i=0; i< knMatches.size(); i++)
{
const cv::DMatch& best = knMatches[i][0];
const cv::DMatch& good = knMatches[i][1];
assert(best.distance <= good.distance);
float ratio = (best.distance / good.distance);
if (ratio <= maxRatio)
{
goodMatches.push_back(best);
}
}
}
bool ImageTransformation::findHomography( const Keypoints& source, const Keypoints& result, const Matches& input, Matches& inliers, cv::Mat& homography)
{
if (input.size() < 4)
return false;
const int pointsCount = input.size();
const float reprojectionThreshold = 2;
//Prepare src and dst points
std::vector<cv::Point2f> srcPoints, dstPoints;
for (int i = 0; i < pointsCount; i++)
{
srcPoints.push_back(source[input[i].trainIdx].pt);
dstPoints.push_back(result[input[i].queryIdx].pt);
}
// Find homography using RANSAC algorithm
std::vector<unsigned char> status;
homography = cv::findHomography(srcPoints, dstPoints, cv::RANSAC, reprojectionThreshold, status);
// Warp dstPoints to srcPoints domain using inverted homography transformation
std::vector<cv::Point2f> srcReprojected;
cv::perspectiveTransform(dstPoints, srcReprojected, homography.inv());
// Pass only matches with low reprojection error (less than reprojectionThreshold value in pixels)
inliers.clear();
for (int i = 0; i < pointsCount; i++)
{
cv::Point2f actual = srcPoints[i];
cv::Point2f expect = srcReprojected[i];
cv::Point2f v = actual - expect;
float distanceSquared = v.dot(v);
if (/*status[i] && */distanceSquared <= reprojectionThreshold * reprojectionThreshold)
{
inliers.push_back(input[i]);
}
}
// Test for bad case
if (inliers.size() < 4)
return false;
// Now use only good points to find refined homography:
std::vector<cv::Point2f> refinedSrc, refinedDst;
for (int i = 0; i < inliers.size(); i++)
{
refinedSrc.push_back(source[inliers[i].trainIdx].pt);
refinedDst.push_back(result[inliers[i].queryIdx].pt);
}
// Use least squares method to find precise homography
cv::Mat homography2 = cv::findHomography(refinedSrc, refinedDst, 0, reprojectionThreshold);
// Reproject again:
cv::perspectiveTransform(dstPoints, srcReprojected, homography2.inv());
inliers.clear();
for (int i = 0; i < pointsCount; i++)
{
cv::Point2f actual = srcPoints[i];
cv::Point2f expect = srcReprojected[i];
cv::Point2f v = actual - expect;
float distanceSquared = v.dot(v);
if (distanceSquared <= reprojectionThreshold * reprojectionThreshold)
{
inliers.push_back(input[i]);
}
}
homography = homography2;
return inliers.size() >= 4;
}
