PNG Image optimizer to run as a cronjob using oxipng

cron_optim_png.py

# -*- coding: utf-8 -*-
# Cron PNG Image optimizer
# chocolatkey (Henry) 2019-03-12
version = "1.1.0"

BASE = "/your/path"
LOCK_FILE = BASE + "/optim.lock"

import os
import sys
import csv
import datetime
from queue import Queue
import threading

import multiprocessing
THREADS = multiprocessing.cpu_count()

def worker():
    global already_optimized, q
    while True:
        obj = q.get()
        if obj is None:
            break

        fpath = os.path.join(obj[0], obj[1])
        print("Optimizing " + fpath)
        # Run oxipng
        os.system("nice -5 oxipng -o 4 -i 0 --strip safe " + fpath)
        # Add to optimized list
        already_optimized.append(obj[1])

        q.task_done()

def main():
    global already_optimized, q
    print("CronOptimPNG " + version)
    if os.path.exists(LOCK_FILE):
        print("Lock file exists, exiting")
        sys.exit(0)
    else:
        with open(LOCK_FILE, 'w', encoding='utf-8') as lockfile:
            lockfile.write(str(datetime.datetime.now()))
    for root, dirs, files in os.walk(BASE):
        if root is BASE:
            continue

        # Each part cache directory
        already_optimized = []
        print("---------" + root + "---------")
        stat_path = root + "_optim.csv"
        if os.path.exists(stat_path):
            print("Stat file exists for " + root)
            with open(stat_path, newline='', encoding='utf-8') as csvfile:
                stat_reader = csv.reader(csvfile)
                for row in stat_reader:
                    already_optimized.append(row[0]) # add filename to skip list
            print("Directory " + root + " has " + str(len(already_optimized)) + ", " + str((len(files) - len(already_optimized))) + " left")
        else:
            print("Directory " + root + " has not yet been optimized at all")

        q = Queue(maxsize=0)
        threads = []
        for i in range(THREADS):
            t = threading.Thread(target=worker)
            t.start()
            threads.append(t)
        # Optimize files
        for name in files:
            if not name.endswith(".png"):
                continue
            if name in already_optimized:
                print(name + " already optimized")
            else:
                q.put((root, name))

        for i in range(THREADS):
            q.put(None)
        for t in threads:
            t.join()

        csv_data = []
        for item in already_optimized:
            csv_data.append((item,))
        with open(stat_path, 'w', newline='', encoding='utf-8') as csvfile:
            writer = csv.writer(csvfile)
            writer.writerows(csv_data)
    print("Finished, removing lock")
    os.remove(LOCK_FILE)

if __name__ == '__main__':
    sys.exit(main())