small fixes for features2d tutorials

doc/tutorials/features2d/feature_description/feature_description.markdown

@@ -49,13 +49,13 @@ int main( int argc, char** argv )
   int minHessian = 400;
 
   Ptr<SURF> detector = SURF::create();
-  detector->setMinHessian(minHessian);
+  detector->setHessianThreshold(minHessian);
 
   std::vector<KeyPoint> keypoints_1, keypoints_2;
   Mat descriptors_1, descriptors_2;
 
-  detector->detectAndCompute( img_1, keypoints_1, descriptors_1 );
-  detector->detectAndCompute( img_2, keypoints_2, descriptors_2 );
+  detector->detectAndCompute( img_1, Mat(), keypoints_1, descriptors_1 );
+  detector->detectAndCompute( img_2, Mat(), keypoints_2, descriptors_2 );
 
   //-- Step 2: Matching descriptor vectors with a brute force matcher
   BFMatcher matcher(NORM_L2);

doc/tutorials/features2d/feature_flann_matcher/feature_flann_matcher.markdown

@@ -58,13 +58,13 @@ int main( int argc, char** argv )
   int minHessian = 400;
 
   Ptr<SURF> detector = SURF::create();
-  detector->setMinHessian(minHessian);
+  detector->setHessianThreshold(minHessian);
 
   std::vector<KeyPoint> keypoints_1, keypoints_2;
   Mat descriptors_1, descriptors_2;
 
-  detector->detectAndCompute( img_1, keypoints_1, descriptors_1 );
-  detector->detectAndCompute( img_2, keypoints_2, descriptors_2 );
+  detector->detectAndCompute( img_1, Mat(), keypoints_1, descriptors_1 );
+  detector->detectAndCompute( img_2, Mat(), keypoints_2, descriptors_2 );
 
   //-- Step 2: Matching descriptor vectors using FLANN matcher
   FlannBasedMatcher matcher;

doc/tutorials/features2d/feature_homography/feature_homography.markdown

@@ -20,6 +20,7 @@ This tutorial code's is shown lines below.
 #include <stdio.h>
 #include <iostream>
 #include "opencv2/core.hpp"
+#include "opencv2/imgproc.hpp"
 #include "opencv2/features2d.hpp"
 #include "opencv2/highgui.hpp"
 #include "opencv2/calib3d.hpp"
@@ -50,8 +51,8 @@ int main( int argc, char** argv )
   std::vector<KeyPoint> keypoints_object, keypoints_scene;
   Mat descriptors_object, descriptors_scene;
 
-  detector->detectAndCompute( img_object, keypoints_object, descriptors_object );
-  detector->detectAndCompute( img_scene, keypoints_scene, descriptors_scene );
+  detector->detectAndCompute( img_object, Mat(), keypoints_object, descriptors_object );
+  detector->detectAndCompute( img_scene, Mat(), keypoints_scene, descriptors_scene );
 
   //-- Step 2: Matching descriptor vectors using FLANN matcher
   FlannBasedMatcher matcher;
@@ -81,13 +82,13 @@ int main( int argc, char** argv )
   Mat img_matches;
   drawMatches( img_object, keypoints_object, img_scene, keypoints_scene,
                good_matches, img_matches, Scalar::all(-1), Scalar::all(-1),
-               vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
+               std::vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
 
   //-- Localize the object
   std::vector<Point2f> obj;
   std::vector<Point2f> scene;
 
-  for( int i = 0; i < good_matches.size(); i++ )
+  for( size_t i = 0; i < good_matches.size(); i++ )
   {
     //-- Get the keypoints from the good matches
     obj.push_back( keypoints_object[ good_matches[i].queryIdx ].pt );

doc/tutorials/features2d/trackingmotion/good_features_to_track/good_features_to_track.markdown

@@ -96,7 +96,7 @@ void goodFeaturesToTrack_Demo( int, void* )
   /// Draw corners detected
   cout<<"** Number of corners detected: "<<corners.size()<<endl;
   int r = 4;
-  for( int i = 0; i < corners.size(); i++ )
+  for( size_t i = 0; i < corners.size(); i++ )
      { circle( copy, corners[i], r, Scalar(rng.uniform(0,255), rng.uniform(0,255),
               rng.uniform(0,255)), -1, 8, 0 ); }