void SURFmatching(cv::Mat matScene, cv::Mat matObject)
{
//-- Step 1: Detect the keypoints and extract descriptors using SURF
int minHessian = 400;
cv::Ptr<SURF> detector = SURF::create(minHessian);
std::vector<cv::KeyPoint> keypoints_object, keypoints_scene;
cv::Mat descriptors_object, descriptors_scene;
detector->detectAndCompute(matObject, cv::Mat(), keypoints_object, descriptors_object);
detector->detectAndCompute(matScene, cv::Mat(), keypoints_scene, descriptors_scene);
//-- Step 2: cv::Matching descriptor vectors using FLANN cv::Matcher
cv::FlannBasedMatcher Matcher;
std::vector< cv::DMatch > Matches;
Matcher.match(descriptors_object, descriptors_scene, Matches);
double max_dist = 0; double min_dist = 100;
//-- Quick calculation of max and min distances between keypoints
for (int i = 0; i < descriptors_object.rows; i++)
{
double dist = Matches[i].distance;
if (dist < min_dist) min_dist = dist;
if (dist > max_dist) max_dist = dist;
}
printf("-- Max dist : %f \n", max_dist);
printf("-- Min dist : %f \n", min_dist);
//-- Draw only "good" cv::Matches (i.e. whose distance is less than 3*min_dist )
std::vector< cv::DMatch > good_Matches;
for (int i = 0; i < descriptors_object.rows; i++)
{
if (Matches[i].distance < 3 * min_dist)
{
good_Matches.push_back(Matches[i]);
}
}
cv::Mat img_Matches;
cv::drawMatches(matObject, keypoints_object, matScene, keypoints_scene,
good_Matches, img_Matches, cv::Scalar::all(-1), cv::Scalar::all(-1),
std::vector<char>(), cv::DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS);
//-- Localize the object
std::vector<cv::Point2f> obj;
std::vector<cv::Point2f> scene;
for (size_t i = 0; i < good_Matches.size(); i++)
{
//-- Get the keypoints from the good cv::Matches
obj.push_back(keypoints_object[good_Matches[i].queryIdx].pt);
scene.push_back(keypoints_scene[good_Matches[i].trainIdx].pt);
}
cv::Mat H = cv::findHomography(obj, scene, cv::RANSAC);
//-- Get the corners from the image_1 ( the object to be "detected" )
std::vector<cv::Point2f> obj_corners(4);
obj_corners[0] = cvPoint(0, 0); obj_corners[1] = cvPoint(matObject.cols, 0);
obj_corners[2] = cvPoint(matObject.cols, matObject.rows); obj_corners[3] = cvPoint(0, matObject.rows);
std::vector<cv::Point2f> scene_corners(4);
cv::perspectiveTransform(obj_corners, scene_corners, H);
//-- Draw lines between the corners (the mapped object in the scene - image_2 )
cv::line(img_Matches, scene_corners[0] + cv::Point2f(matObject.cols, 0), scene_corners[1] + cv::Point2f(matObject.cols, 0), cv::Scalar(0, 255, 0), 4);
cv::line(img_Matches, scene_corners[1] + cv::Point2f(matObject.cols, 0), scene_corners[2] + cv::Point2f(matObject.cols, 0), cv::Scalar(0, 255, 0), 4);
cv::line(img_Matches, scene_corners[2] + cv::Point2f(matObject.cols, 0), scene_corners[3] + cv::Point2f(matObject.cols, 0), cv::Scalar(0, 255, 0), 4);
cv::line(img_Matches, scene_corners[3] + cv::Point2f(matObject.cols, 0), scene_corners[0] + cv::Point2f(matObject.cols, 0), cv::Scalar(0, 255, 0), 4);
//-- Show detected cv::Matches
img_Matches = ResizeByHeight(img_Matches, 600);
cv::imshow("Good cv::Matches & Object detection", img_Matches);
}
