import cv2
import numpy as np     

image,contours,hierarchy=cv2.findContours(image,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

for obj in np.array(contours):
    t1 = obj.flatten()#降维
    t2 = [str(x) for x in t1]#转为字符串格式
    t3 = ' '.join(t2)
    f = open('test.txt', "a", encoding='utf-8')
    f.writelines([t3,' ','building','\n'])
    f.close()