lot's of changes; nonfree & photo modules added; SIFT & SURF -> nonfree module; Inpainting -> photo; refactored features2d (ORB is still failing tests), optimized brute-force matcher and made it non-template.

modules/features2d/src/keypoint.cpp

@@ -165,6 +165,52 @@ float KeyPoint::overlap( const KeyPoint& kp1, const KeyPoint& kp2 )
 
     return ovrl;
 }
+    
+    
+struct KeypointResponseGreaterThanThreshold
+{
+    KeypointResponseGreaterThanThreshold(float _value) :
+    value(_value)
+    {
+    }
+    inline bool operator()(const KeyPoint& kpt) const
+    {
+        return kpt.response >= value;
+    }
+    float value;
+};
+
+struct KeypointResponseGreater
+{
+    inline bool operator()(const KeyPoint& kp1, const KeyPoint& kp2) const
+    {
+        return kp1.response > kp2.response;
+    }
+};
+
+// takes keypoints and culls them by the response
+void KeyPointsFilter::retainBest(vector<KeyPoint>& keypoints, int n_points)
+{
+    //this is only necessary if the keypoints size is greater than the number of desired points.
+    if( n_points > 0 && keypoints.size() > (size_t)n_points )
+    {
+        if (n_points==0)
+        {
+            keypoints.clear();
+            return;
+        }
+        //first use nth element to partition the keypoints into the best and worst.
+        std::nth_element(keypoints.begin(), keypoints.begin() + n_points, keypoints.end(), KeypointResponseGreater());
+        //this is the boundary response, and in the case of FAST may be ambigous
+        float ambiguous_response = keypoints[n_points - 1].response;
+        //use std::partition to grab all of the keypoints with the boundary response.
+        vector<KeyPoint>::const_iterator new_end =
+        std::partition(keypoints.begin() + n_points, keypoints.end(),
+                       KeypointResponseGreaterThanThreshold(ambiguous_response));
+        //resize the keypoints, given this new end point. nth_element and partition reordered the points inplace
+        keypoints.resize(new_end - keypoints.begin());
+    }
+}
 
 struct RoiPredicate
 {