terrible.py

import os
import random
import struct

while True:
    src = open("source.vtf", "rb")
    f = open("test.vtf", "wb")
    word = src.read(4)
    while len(word) == 4:
        word = struct.unpack("I", word)[0]
        if random.randint(0, 20) < 3:
            bit = random.randint(0, 31)
            word = word ^ (1 << bit)
        word = struct.pack("I", word)
        f.write(word)
        word = src.read(4)
    os.system("\"C:/Program Files (x86)/Steam/steamapps/common/Team Fortress 2/bin/vtf2tga.exe\" -i test.vtf")