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_detection/SURF_detection_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;
+
+int main( int argc, char* argv[] )
+{
+    CommandLineParser parser( argc, argv, "{@input | ../data/box.png | input image}" );
+    Mat src = imread( parser.get<String>( "@input" ), IMREAD_GRAYSCALE );
+    if ( src.empty() )
+    {
+        cout << "Could not open or find the image!\n" << endl;
+        cout << "Usage: " << argv[0] << " <Input image>" << endl;
+        return -1;
+    }
+
+    //-- Step 1: Detect the keypoints using SURF Detector
+    int minHessian = 400;
+    Ptr<SURF> detector = SURF::create( minHessian );
+    std::vector<KeyPoint> keypoints;
+    detector->detect( src, keypoints );
+
+    //-- Draw keypoints
+    Mat img_keypoints;
+    drawKeypoints( src, keypoints, img_keypoints );
+
+    //-- Show detected (drawn) keypoints
+    imshow("SURF Keypoints", img_keypoints );
+
+    waitKey();
+    return 0;
+}
+#else
+int main()
+{
+    std::cout << "This tutorial code needs the xfeatures2d contrib module to be run." << std::endl;
+    return 0;
+}
+#endif