# Coordinates of keypoints using FLANN matcher

I have two images (faces) and I want to check if it is the same person or not. So far I implemented as it is in this tutorial and I obtained this results:

So far I could work with that. I would just need to check that each point from left and right are in the same horizontal lines I could same it is the same face in both images. But the thing is, how do I get the coordinates of each of the points shown in the images above?

This is the code:

    // Step 1: Detect the keypoints using SURF detect.
int minHessian = 400;
SurfFeatureDetector detector(minHessian);
std::vector<KeyPoint> keypoints_1, keypoints_2;
detector.detect(roiFrameMaster, keypoints_1);
detector.detect(roiFrameSlave, keypoints_2);

// Step 2: Calculate descriptors (feature vectors).
SurfDescriptorExtractor extractor;
Mat descriptors_1, descriptors_2;
extractor.compute(roiFrameMaster, keypoints_1, descriptors_1);
extractor.compute(roiFrameSlave, keypoints_2, descriptors_2);

// Step 3 : Matching descriptor vectors using FLANN matcher.
FlannBasedMatcher matcher;
std::vector< DMatch > matches;
matcher.match(descriptors_1, descriptors_2, matches);

double max_dist = 0; double min_dist = 100;
//-- Quick calculation of max and min distances between keypoints
for( int i = 0; i < descriptors_1.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" matches (i.e. whose distance is less than 2*min_dist,
//-- or a small arbitary value ( 0.02 ) in the event that min_dist is very
//-- small)
std::vector< DMatch > good_matches;

for( int i = 0; i < descriptors_1.rows; i++ )
{
if( matches[i].distance <= max(2*min_dist, 0.02))
good_matches.push_back( matches[i]);
}

//-- Draw only "good" matches
Mat img_matches;
drawMatches(roiFrameMaster, keypoints_1, roiFrameSlave, keypoints_2,
good_matches, img_matches, Scalar::all(-1), Scalar::all(-1),
vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );

//-- Show detected matches
imshow( "Good Matches", img_matches);


Thanks for the help.

edit retag close merge delete