open-cv轮廓检测

Question

open-cv的轮廓检测矩形拟合 下图中如何实现最大矩形的检测呢

1. 

Answer 1

import cv2 as cv
import numpy as np

img_path = "/home/LTL/Desktop/20220719171125.png"

img_np = cv.imread(img_path)
ret, thresh1 = cv.threshold(img_np, 80, 255, cv.THRESH_BINARY)
np_zeros = np.ones(thresh1.shape[0:2]) * 255

index_1 = np.where(thresh1[:, :, 0] == 0)
index_2 = np.where(thresh1[:, :, 1] == 0)
index_3 = np.where(thresh1[:, :, 1] == 0)
np_zeros[index_1[0], index_1[1]] = 0
np_zeros[index_2[0], index_2[1]] = 0
np_zeros[index_3[0], index_3[1]] = 0

contour_list, _ = cv.findContours(np_zeros.astype(np.uint8), cv.RETR_TREE, cv.CHAIN_APPROX_SIMPLE)

contour_area_list = list(map(lambda x: cv.contourArea(x), contour_list))
contour_list = list(filter(lambda x: 100 < cv.contourArea(x) < img_np.shape[0] * img_np.shape[1] // 2, contour_list))
result_xywh = []
result_poly_point = []
contour_list.sort(key=lambda x: cv.contourArea(x), reverse=True)

for contour_i, contour in enumerate(contour_list[0:1]):
    contour_area = cv.contourArea(contour)
    x, y, w, h = cv.boundingRect(contour)

    poly_point_list = contour[:, 0, :].ravel().tolist()
    poly_point = np.int0(poly_point_list).reshape((-1, 1, 2))
    result_poly_point.append(poly_point)
    cv.rectangle(img_np, (x, y), (x + w, y + h), (255, 255, 0), 2)
cv.imshow('', img_np)
cv.waitKey()
cv.destroyAllWindows()