Pythonを使って直線検出をする

環境

・Ubuntu18.04
・Python3
import numpy as np
import cv2
import itertools


def calc_haarlike(crop_img):
    crop_img = crop_img[:,::-1]

    threshold = 10
    rect_w = 8
    pattern_w = rect_w // 2 
    width = crop_img.shape[1]
    
    peak_index = 0
    max_value = 0
    
    for index in range(width-rect_w):
        a1 = np.mean(crop_img[:, index: index+pattern_w])
        a2 = np.mean(crop_img[:, index+pattern_w: index+rect_w])
        H = a1-a2 
        if max_value < H and H - max_value > threshold:
            max_value = H
            peak_index = index

    index = width - peak_index + rect_w
    return index if max_value > 0 else -1

def candidate_extraction(img):
    n = []
    h, w = img.shape[0], img.shape[1]
    wh = 8 #window height
    window_pos = np.array([
        [[400, 600], [500, 700]],
        [[380, 580], [520, 720]],
        [[360, 560], [540, 740]],
        
        [[700, 900], [800, 1000]],
        [[680, 880], [820, 1020]],
        [[660, 860], [840, 1040]],
    ])

    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
    for i, ((x1, y1), (x2, y2)) in enumerate(window_pos):
        crop_img = gray[y1: y2, x1: x2]
        peak_index = calc_haarlike(crop_img)
        cv2.imwrite("./img_gray_"+str(i)+".jpg", crop_img)
        cv2.line(img,pt1=(x1, y1), pt2=(x2,y2),color=(0,0,255),thickness=10)
        if peak_index != -1:
            cv2.circle(img, (x1+peak_index, y1), 5, (255, 0, 0), thickness=1)
            n.append([x1 + peak_index,y1])

    t = itertools.combinations(n,2)
    for i in t:
        print(i)
        a,b = linear(i[0],i[1])
        if a != 0:
            cv2.line(img,pt1=(0,b), pt2=(int((len(img) - b)/a),len(img)),color=(0,255,0),thickness=10)
            cv2.line(img,pt1=(0,b), pt2=(len(img[0]),int(len(img[0])*a + b)),color=(0,255,0),thickness=10)
        else:
            cv2.line(img,pt1=(0, int(b)), pt2=(len(img[0]),int(b)),color=(0,255,0),thickness=10)
    cv2.imwrite("./img.jpg", img)

def linear(n1, n2):
    a = (n2[1]-n1[1])/(n2[0]-n1[0])
    b = int((n2[0]*n1[1]-n1[0]*n2[1])/(n2[0]-n1[0]))
    return a, b

def main():
    img = cv2.imread("./data/path.jpg")
    candidate_extraction(img)

if __name__ == '__main__':
    main()
参考

こちらの方のプログラムを参考にしております。
https://nsr-9.hatenablog.jp/entry/2021/08/15/120000