Feature Points

import cv2
import numpy as np

image = cv2.imread("photo.jpg")
gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

# ORB: Oriented FAST and Rotated BRIEF
# Fast, free to use, good for matching and tracking
orb = cv2.ORB_create(nfeatures=500)

# Detect keypoints and compute descriptors
keypoints, descriptors = orb.detectAndCompute(gray, None)

print(f"Detected {len(keypoints)} feature points")
print(f"Descriptor shape: {descriptors.shape}")  # (n_keypoints, 32)

# Draw keypoints on the image
result = cv2.drawKeypoints(
    image, keypoints, None,
    color=(0, 255, 0),
    flags=cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS
)

cv2.imwrite("feature_points.jpg", result)

# Analyse keypoint properties
if keypoints:
    strongest = max(keypoints, key=lambda kp: kp.response)
    print(f"Strongest keypoint: position=({strongest.pt[0]:.1f}, {strongest.pt[1]:.1f})")
    print(f"  Size: {strongest.size:.1f}, Angle: {strongest.angle:.1f}°")