add part of opencv

Lib/opencv/sources/doc/tutorials/features2d/feature_detection/feature_detection.markdown

@@ -0,0 +1,53 @@
+Feature Detection {#tutorial_feature_detection}
+=================
+
+Goal
+----
+
+In this tutorial you will learn how to:
+
+-   Use the @ref cv::FeatureDetector interface in order to find interest points. Specifically:
+    -   Use the cv::xfeatures2d::SURF and its function cv::xfeatures2d::SURF::detect to perform the
+        detection process
+    -   Use the function @ref cv::drawKeypoints to draw the detected keypoints
+
+\warning You need the <a href="https://github.com/opencv/opencv_contrib">OpenCV contrib modules</a> to be able to use the SURF features
+(alternatives are ORB, KAZE, ... features).
+
+Theory
+------
+
+Code
+----
+
+@add_toggle_cpp
+This tutorial code's is shown lines below. You can also download it from
+[here](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/features2D/feature_detection/SURF_detection_Demo.cpp)
+@include samples/cpp/tutorial_code/features2D/feature_detection/SURF_detection_Demo.cpp
+@end_toggle
+
+@add_toggle_java
+This tutorial code's is shown lines below. You can also download it from
+[here](https://github.com/opencv/opencv/tree/master/samples/java/tutorial_code/features2D/feature_detection/SURFDetectionDemo.java)
+@include samples/java/tutorial_code/features2D/feature_detection/SURFDetectionDemo.java
+@end_toggle
+
+@add_toggle_python
+This tutorial code's is shown lines below. You can also download it from
+[here](https://github.com/opencv/opencv/tree/master/samples/python/tutorial_code/features2D/feature_detection/SURF_detection_Demo.py)
+@include samples/python/tutorial_code/features2D/feature_detection/SURF_detection_Demo.py
+@end_toggle
+
+Explanation
+-----------
+
+Result
+------
+
+-#  Here is the result of the feature detection applied to the `box.png` image:
+
+    ![](images/Feature_Detection_Result_a.jpg)
+
+-#  And here is the result for the `box_in_scene.png` image:
+
+    ![](images/Feature_Detection_Result_b.jpg)