Added Features2D descriptor tutorial + drawMatches in rst

doc/tutorials/features2d/feature_detection/feature_detection.rst

@@ -0,0 +1,97 @@
+.. _feature_detection:
+
+Feature Detection
+******************
+
+Goal
+=====
+
+In this tutorial you will learn how to:
+
+.. container:: enumeratevisibleitemswithsquare
+
+   * Use the :feature_detector:`FeatureDetector<>` interface in order to find interest points. Specifically:
+
+     * Use the :surf_feature_detector:`SurfFeatureDetector<>` and its function :feature_detector_detect:`detect<>` to perform the detection process
+     * Use the function :draw_keypoints:`drawKeypoints<>` to draw the detected keypoints
+     
+
+Theory
+======
+
+Code
+====
+
+This tutorial code's is shown lines below. You can also download it from `here <https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/features2D/SURF_detector.cpp>`_
+
+.. code-block:: cpp 
+
+   #include <stdio.h>
+   #include <iostream>
+   #include "opencv2/core/core.hpp"
+   #include "opencv2/features2d/features2d.hpp"	
+   #include "opencv2/highgui/highgui.hpp"
+
+   using namespace cv;
+
+   void readme();
+
+   /** @function main */
+   int main( int argc, char** argv )
+   {
+     if( argc != 3 )
+     { readme(); return -1; }
+
+     Mat img_1 = imread( argv[1], CV_LOAD_IMAGE_GRAYSCALE );
+     Mat img_2 = imread( argv[2], CV_LOAD_IMAGE_GRAYSCALE );
+  
+     if( !img_1.data || !img_2.data )
+     { std::cout<< " --(!) Error reading images " << std::endl; return -1; }
+
+     //-- Step 1: Detect the keypoints using SURF Detector
+     int minHessian = 400;
+
+     SurfFeatureDetector detector( minHessian );
+
+     std::vector<KeyPoint> keypoints_1, keypoints_2;
+
+     detector.detect( img_1, keypoints_1 );
+     detector.detect( img_2, keypoints_2 );
+
+     //-- Draw keypoints
+     Mat img_keypoints_1; Mat img_keypoints_2;
+
+     drawKeypoints( img_1, keypoints_1, img_keypoints_1, Scalar::all(-1), DrawMatchesFlags::DEFAULT ); 
+     drawKeypoints( img_2, keypoints_2, img_keypoints_2, Scalar::all(-1), DrawMatchesFlags::DEFAULT ); 
+
+     //-- Show detected (drawn) keypoints
+     imshow("Keypoints 1", img_keypoints_1 );
+     imshow("Keypoints 2", img_keypoints_2 );
+
+     waitKey(0);
+
+     return 0;
+     }
+
+     /** @function readme */
+     void readme()
+     { std::cout << " Usage: ./SURF_detector <img1> <img2>" << std::endl; }
+
+Explanation
+============
+
+Result
+======
+ 
+#. Here is the result of the feature detection applied to the first image:
+ 
+   .. image:: images/Feature_Detection_Result_a.jpg
+      :align: center
+      :height: 125pt
+
+#. And here is the result for the second image:
+
+   .. image:: images/Feature_Detection_Result_b.jpg
+      :align: center  
+      :height: 200pt 
+