Chapter 9

1. Keypoints and compute descriptors in the loaded image, image, with ORB are as follows:

orb = cv2.ORB()
keypoints = orb.detect(image, None)
keypoints, descriptors = orb.compute(image, keypoints)

2. Previously detected keypoints, keypoints, are as follows:

image_keypoints = cv2.drawKeypoints(image, keypoints, None, color=(255, 0, 255), flags=0)

To draw detected keypoints, the cv2.drawKeypoints() function is used.

 

3. The BFMatcher object and matching of the descriptors, descriptors_1 and descriptors_2, which have been previously calculated, is created as follows:

bf_matcher = cv2.BFMatcher(cv2.NORM_HAMMING, crossCheck=True)
bf_matches = bf_matcher.match(descriptors_1, descriptors_2)

4. The first 20 matches of the matches that were sorted before is as follows:

bf_matches = sorted(bf_matches, key=lambda x: x.distance)
result = cv2.drawMatches(image_query, keypoints_1, image_scene, keypoints_2, bf_matches[:20], None, matchColor=(255, 255, 0), singlePointColor=(255, 0, 255), flags=0)

To draw the computed matches,  cv2.drawMatches() is used.

5. Markers using ArUco in the image gray_frame are detected as follows:

corners, ids, rejected_corners = cv2.aruco.detectMarkers(gray_frame, aruco_dictionary, parameters=parameters)

To detect markers, the cv2.aruco.detectMarkers() function is used.

6. The detected markers when using ArUco are as follows: 

frame = cv2.aruco.drawDetectedMarkers(image=frame, corners=corners, ids=ids, borderColor=(0, 255, 0))

To draw markers, the cv2.aruco.drawDetectedMarkers() function is used. 

7. The rejected markers when using Aruco are as follows:

frame = cv2.aruco.drawDetectedMarkers(image=frame, corners=rejected_corners, borderColor=(0, 0, 255))

To draw markers, the cv2.aruco.drawDetectedMarkers() function is also used. 

8. Detect and decode a QR code contained in the image with the following code:

 data, bbox, rectified_qr_code = qr_code_detector.detectAndDecode(image)