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/python/tutorial_code/TrackingMotion/harris_detector/cornerHarris_Demo.py

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+from __future__ import print_function
+import cv2 as cv
+import numpy as np
+import argparse
+
+source_window = 'Source image'
+corners_window = 'Corners detected'
+max_thresh = 255
+
+def cornerHarris_demo(val):
+    thresh = val
+
+    # Detector parameters
+    blockSize = 2
+    apertureSize = 3
+    k = 0.04
+
+    # Detecting corners
+    dst = cv.cornerHarris(src_gray, blockSize, apertureSize, k)
+
+    # Normalizing
+    dst_norm = np.empty(dst.shape, dtype=np.float32)
+    cv.normalize(dst, dst_norm, alpha=0, beta=255, norm_type=cv.NORM_MINMAX)
+    dst_norm_scaled = cv.convertScaleAbs(dst_norm)
+
+    # Drawing a circle around corners
+    for i in range(dst_norm.shape[0]):
+        for j in range(dst_norm.shape[1]):
+            if int(dst_norm[i,j]) > thresh:
+                cv.circle(dst_norm_scaled, (j,i), 5, (0), 2)
+
+    # Showing the result
+    cv.namedWindow(corners_window)
+    cv.imshow(corners_window, dst_norm_scaled)
+
+# Load source image and convert it to gray
+parser = argparse.ArgumentParser(description='Code for Harris corner detector tutorial.')
+parser.add_argument('--input', help='Path to input image.', default='../data/building.jpg')
+args = parser.parse_args()
+
+src = cv.imread(args.input)
+if src is None:
+    print('Could not open or find the image:', args.input)
+    exit(0)
+
+src_gray = cv.cvtColor(src, cv.COLOR_BGR2GRAY)
+
+# Create a window and a trackbar
+cv.namedWindow(source_window)
+thresh = 200 # initial threshold
+cv.createTrackbar('Threshold: ', source_window, thresh, max_thresh, cornerHarris_demo)
+cv.imshow(source_window, src)
+cornerHarris_demo(thresh)
+
+cv.waitKey()