Python/computer_vision/harris_corner.py
Christian Clauss 71b458cefe
Rename harriscorner.py to harris_corner.py (#4470)
* Rename harriscorner.py to harris_corner.py

* updating DIRECTORY.md

* Rename meanthreshold.py to mean_threshold.py

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
2021-05-31 21:19:09 +05:30

76 lines
2.1 KiB
Python

import cv2
import numpy as np
"""
Harris Corner Detector
https://en.wikipedia.org/wiki/Harris_Corner_Detector
"""
class Harris_Corner:
def __init__(self, k: float, window_size: int):
"""
k : is an empirically determined constant in [0.04,0.06]
window_size : neighbourhoods considered
"""
if k in (0.04, 0.06):
self.k = k
self.window_size = window_size
else:
raise ValueError("invalid k value")
def __str__(self):
return f"Harris Corner detection with k : {self.k}"
def detect(self, img_path: str):
"""
Returns the image with corners identified
img_path : path of the image
output : list of the corner positions, image
"""
img = cv2.imread(img_path, 0)
h, w = img.shape
corner_list = []
color_img = img.copy()
color_img = cv2.cvtColor(color_img, cv2.COLOR_GRAY2RGB)
dy, dx = np.gradient(img)
ixx = dx ** 2
iyy = dy ** 2
ixy = dx * dy
k = 0.04
offset = self.window_size // 2
for y in range(offset, h - offset):
for x in range(offset, w - offset):
wxx = ixx[
y - offset : y + offset + 1, x - offset : x + offset + 1
].sum()
wyy = iyy[
y - offset : y + offset + 1, x - offset : x + offset + 1
].sum()
wxy = ixy[
y - offset : y + offset + 1, x - offset : x + offset + 1
].sum()
det = (wxx * wyy) - (wxy ** 2)
trace = wxx + wyy
r = det - k * (trace ** 2)
# Can change the value
if r > 0.5:
corner_list.append([x, y, r])
color_img.itemset((y, x, 0), 0)
color_img.itemset((y, x, 1), 0)
color_img.itemset((y, x, 2), 255)
return color_img, corner_list
if __name__ == "__main__":
edge_detect = Harris_Corner(0.04, 3)
color_img, _ = edge_detect.detect("path_to_image")
cv2.imwrite("detect.png", color_img)