Add Java and Python code for the following features2d tutorials: Harris corner detector, Shi-Tomasi corner detector, Creating your own corner detector, Detecting corners location in subpixels, Feature Detection, Feature Description, Feature Matching with FLANN, Features2D + Homography to find a known object. Use Lowe's ratio test to filter the matches.

samples/cpp/tutorial_code/features2D/feature_description/SURF_matching_Demo.cpp

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+#include <iostream>
+#include "opencv2/core.hpp"
+#ifdef HAVE_OPENCV_XFEATURES2D
+#include "opencv2/highgui.hpp"
+#include "opencv2/features2d.hpp"
+#include "opencv2/xfeatures2d.hpp"
+
+using namespace cv;
+using namespace cv::xfeatures2d;
+using std::cout;
+using std::endl;
+
+const char* keys =
+    "{ help h |                          | Print help message. }"
+    "{ input1 | ../data/box.png          | Path to input image 1. }"
+    "{ input2 | ../data/box_in_scene.png | Path to input image 2. }";
+
+int main( int argc, char* argv[] )
+{
+    CommandLineParser parser( argc, argv, keys );
+    Mat img1 = imread( parser.get<String>("input1"), IMREAD_GRAYSCALE );
+    Mat img2 = imread( parser.get<String>("input2"), IMREAD_GRAYSCALE );
+    if ( img1.empty() || img2.empty() )
+    {
+        cout << "Could not open or find the image!\n" << endl;
+        parser.printMessage();
+        return -1;
+    }
+
+    //-- Step 1: Detect the keypoints using SURF Detector, compute the descriptors
+    int minHessian = 400;
+    Ptr<SURF> detector = SURF::create( minHessian );
+    std::vector<KeyPoint> keypoints1, keypoints2;
+    Mat descriptors1, descriptors2;
+    detector->detectAndCompute( img1, noArray(), keypoints1, descriptors1 );
+    detector->detectAndCompute( img2, noArray(), keypoints2, descriptors2 );
+
+    //-- Step 2: Matching descriptor vectors with a brute force matcher
+    // Since SURF is a floating-point descriptor NORM_L2 is used
+    Ptr<DescriptorMatcher> matcher = DescriptorMatcher::create(DescriptorMatcher::BRUTEFORCE);
+    std::vector< DMatch > matches;
+    matcher->match( descriptors1, descriptors2, matches );
+
+    //-- Draw matches
+    Mat img_matches;
+    drawMatches( img1, keypoints1, img2, keypoints2, matches, img_matches );
+
+    //-- Show detected matches
+    imshow("Matches", img_matches );
+
+    waitKey();
+    return 0;
+}
+#else
+int main()
+{
+    std::cout << "This tutorial code needs the xfeatures2d contrib module to be run." << std::endl;
+    return 0;
+}
+#endif