resize-n-save.py

import os
import argparse
import PIL.Image as PILI


# Comply with os.makedirs - should not use parent dir. (..) in out_dir
ap = argparse.ArgumentParser()
ap.add_argument("in_dir")  # e.g. "inat18/"
ap.add_argument("out_dir")  # e.g. "out/"
ap.add_argument("--new_size", default=128)

args = ap.parse_args()

in_dir = args.in_dir
out_dir = args.out_dir
new_size = int(args.new_size)

for dirpath, dirnames, filenames in os.walk(in_dir):
    for img_name in filenames:
        # Skips empty directories
        img_path = dirpath + "/" + img_name
        resized_img = PILI.open(img_path).resize((new_size, new_size), PILI.ANTIALIAS).convert("RGB")
        
        # Ensure jpg output
        # TODO: Does not consider formats other than png. Needs better filename detection
        if img_name.endswith(".png"):
            resized_img_name = img_name[:-3] + "jpg"
        elif img_name.endswith(".jpeg"):
            resized_img_name = img_name[:-4] + "jpg"
        else:
            resized_img_name = img_name
        
        save_dir = out_dir + dirpath[len(in_dir):]
        os.makedirs(save_dir, exist_ok=True)
        
        save_path = save_dir + "/" + resized_img_name
        resized_img.save(save_path, subsampling=0, quality=100)  # Lose as little quality as possible
        print("Saved image:", save_path)