I have OpenCV 3.0, and I have compiled & installed it with the opencv_contrib module so that's not a problem. Unfortunately the examples from previous versions do not work with the current one, and so although this question has already been asked more than once I would like a more current example that I can actually work with. Even the official examples don't work in this version (feature detection works but not other feature examples) and they use SURF anyway.
So, how do I use OpenCV SIFT on C++? I want to grab the keypoints in two images and match them, similar to this example, but even just getting the points and descriptors would be enough help. Help!
then:
#include "opencv2/xfeatures2d.hpp"
//
// now, you can no more create an instance on the 'stack', like in the tutorial
// (yea, noticed for a fix/pr).
// you will have to use cv::Ptr all the way down:
//
cv::Ptr<Feature2D> f2d = xfeatures2d::SIFT::create();
//cv::Ptr<Feature2D> f2d = xfeatures2d::SURF::create();
//cv::Ptr<Feature2D> f2d = ORB::create();
// you get the picture, i hope..
//-- Step 1: Detect the keypoints:
std::vector<KeyPoint> keypoints_1, keypoints_2;
f2d->detect( img_1, keypoints_1 );
f2d->detect( img_2, keypoints_2 );
//-- Step 2: Calculate descriptors (feature vectors)
Mat descriptors_1, descriptors_2;
f2d->compute( img_1, keypoints_1, descriptors_1 );
f2d->compute( img_2, keypoints_2, descriptors_2 );
//-- Step 3: Matching descriptor vectors using BFMatcher :
BFMatcher matcher;
std::vector< DMatch > matches;
matcher.match( descriptors_1, descriptors_2, matches );
also, don't forget to link opencv_xfeatures2d !