pip install tifffile

new_gray = gray_img[np.newaxis, ::]

tiff_list = np.append(tiff_list, new_gray, axis=0)

tifffile.imsave( out_tiff_path, tiff_list )

import cv2
import tifffile
import time
import numpy as np
import time
import os

img_path = '../word_all'
out_txt_path = '../out_word_all.box'
out_tiff_path = '../out_word_all.tif'

tiff_list = None


with open(out_txt_path, 'wb') as f:
  dir_list = os.listdir(img_path)
  cnt_num = 0
  
  for dir_name in dir_list:
    dir_path = os.path.join(img_path, dir_name)
    img_list = os.listdir(dir_path)
    pwd = os.getcwd()
    os.chdir(dir_path)
    
    for img in img_list:
      
      print('dir_path:{}'.format(dir_path))
      gray_img = cv2.imread(img, cv2.IMREAD_GRAYSCALE)
      new_gray = gray_img[np.newaxis, ::]
      print('gray_img shape:{}, new_gray shape:{}'.format(gray_img.shape, new_gray.shape))
      #global cnt_num
      if cnt_num == 0:
        print('cnt_num == 0')
        tiff_list = new_gray
      else:
        print('np.append')
        tiff_list = np.append(tiff_list, new_gray, axis=0)
        print('tiff_list shape:{}'.format(tiff_list.shape))
      
      content = '{} 2 2 60 60 {}\n'.format(dir_name, cnt_num)
      print(content)
      f.write(content.encode('UTF-8'))
      cnt_num += 1
    os.chdir(pwd)

  tifffile.imsave( out_tiff_path, tiff_list )


print('tiff_list shape:{}'.format(tiff_list.shape))