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) -> str: return f"Harris Corner detection with k : {self.k}" def detect(self, img_path: str) -> tuple[cv2.Mat, list[list[int]]]: """ 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: list[list[int]] = [] 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)