void getMatches(cv::BFMatcher &m_matcher, const cv::Mat &trainDescriptors, const cv::Mat& queryDescriptors, std::vector<cv::DMatch>& good_matches)
{
std::vector<std::vector<cv::DMatch> > m_knnMatches;
good_matches.clear();
// To avoid NaNs when best match has
// zero distance we will use inverse ratio.
const float minRatio =1.f / 1.5f;
// KNN match will return 2 nearest
// matches for each query descriptor
m_matcher.knnMatch(trainDescriptors, queryDescriptors, m_knnMatches,10);
for (size_t i=0; i < m_knnMatches.size(); i++)
{
const cv::DMatch& bestMatch = m_knnMatches[i][0];
const cv::DMatch& betterMatch = m_knnMatches[i][1];
float distanceRatio = bestMatch.distance /
betterMatch.distance;
// Pass only matches where distance ratio between
// nearest matches is greater than 1.5
// (distinct criteria)
if (distanceRatio < minRatio)
{
good_matches.push_back(bestMatch);
}
}
}
cv::Point2f calcLocation(cv::Mat query_img) {
std::vector<cv::KeyPoint> kp_query; // Keypoints of the query image
cv::Mat des_query;
cv::Mat query_img_gray;
cv::cvtColor(query_img,
query_img_gray,
cv::COLOR_BGR2GRAY);
detector->detectAndCompute(query_img_gray,
cv::noArray(),
kp_query,
des_query);
std::vector< std::vector<cv::DMatch> > matches;
matcher.knnMatch(des_ref,
des_query,
matches,
2);
std::vector<cv::KeyPoint> matched_query, matched_ref, inliers_query, inliers_ref;
std::vector<cv::DMatch> good_matches;
//-- Localize the object
std::vector<cv::Point2f> pts_query;
std::vector<cv::Point2f> pts_ref;
for(size_t i = 0; i < matches.size(); i++) {
cv::DMatch first = matches[i][0];
float dist_query = matches[i][0].distance;
float dist_ref = matches[i][1].distance;
if (dist_query < match_ratio * dist_ref) {
matched_query.push_back(kp_query[first.queryIdx]);
matched_ref.push_back(kp_ref[first.trainIdx]);
pts_query.push_back(kp_query[first.queryIdx].pt);
pts_ref.push_back(kp_ref[first.trainIdx].pt);
}
}
cv::Mat mask;
// Homograpy
cv::Mat homography;
homography = cv::findHomography(pts_query,
pts_ref,
cv::RANSAC,
5,
mask);
// Input Quadilateral or Image plane coordinates
std::vector<cv::Point2f> centers(1), centers_transformed(1);
cv::Point2f center(query_img_gray.rows / 2,
query_img_gray.cols / 2);
cv::Point2f center_transformed(query_img.rows / 2,
query_img.cols / 2);
centers[0] = center; // Workaround for using perspective transform
cv::perspectiveTransform(centers,
centers_transformed,
homography);
center_transformed = centers_transformed[0];
return center_transformed;
}