import cv2
import glob
import os
import tqdm
from itertools import islice
from multiprocessing import Pool
from pathlib import Path

path = r'./**/*.png'
resize_factor = (0.5, 0.5) # Width, Height

def resize_image(_file):
    img = cv2.imread(_file, cv2.IMREAD_UNCHANGED)
    resized_img = cv2.resize(img, None, fx=resize_factor[0], fy=resize_factor[1])
    save_path = os.path.join('../resized_image', _file)
    Path(os.path.dirname(save_path)).mkdir(parents=True, exist_ok=True)
    cv2.imwrite(save_path, resized_img)

if __name__ == '__main__':
    num_process = 16
    files = glob.glob(path, recursive=True)
    len_total = len(files)
    # iter_files = iter(files)
    # files = [list(islice(iter_files, e)) for e in [len(files) // num_process] * (num_process + 1)]
    with Pool(processes=num_process) as p:
        r = list(tqdm.tqdm(p.imap(resize_image, files), total=len_total))