NO-ob

// ==UserScript==
// @icon         https://gelbooru.com/favicon.ico
// @name         Gelbooru Resize
// @namespace    kannalo
// @version      0.1
// @description  try to take over the world!
// @author       You
// @match        *://gelbooru.com/index.php?page=post&s=view*
// @grant        none

NO-ob

import os
import re
dir = os.getcwd()

for filename in os.listdir(dir):
        match = re.search("\s\d{3}\s", filename)
        if match:
                num = int(match.group().strip(" ")) + 2
                if num < 100:
                        num = "0" + str(num)