Split zmx files from a zmf catalog

zmf2zmx.py

import numpy as np
import sys
from struct import Struct

if len(sys.argv) != 3:
    print("usage: zmf2zmx in.zmf zmx_dir")

with open(sys.argv[1], 'rb') as f:
    zmf_bytes = f.read()

zmx_dir = sys.argv[2] + '/'

header = Struct('<100s24xIdd')

# from https://github.com/quartiq/rayopt/blob/master/rayopt/zemax.py#L79
def zmf_obfuscate(data, a, b):
    iv = np.cos(6*a + 3*b)
    iv = np.cos(655*(np.pi/180)*iv) + iv
    p = np.arange(len(data))
    k = 13.2*(iv + np.sin(17*(p + 3)))*(p + 1)
    k = (int((f"{_:.8e}")[4:7]) for _ in k)
    data = np.frombuffer(data, np.uint8)
    data = data ^ np.fromiter(k, np.uint8, len(data))
    return data.tobytes().decode()

# drop the first four bytes
cur = 4
while cur < len(zmf_bytes):
    data = header.unpack(zmf_bytes[cur: cur+header.size])
    name = data[0].rstrip(b'\0').decode()
    size = data[1]
    a, b = data[2], data[3]
    try:
        with open(zmx_dir + name, 'w') as f:
            f.write(zmf_obfuscate(zmf_bytes[cur+header.size:cur+header.size+size], a, b))
    except:
        print("failed on", name)

    cur += header.size + size

Just signed in to say thank You!
Saved me a lot of time and trouble. Thanks for sharing.