import base64
import hashlib
import hmac
import textwrap


key = bytes.fromhex("943b421c9eb07c830af81030552c86009268de4e532ba2ee2eab8247c6da0881")
salt = bytes.fromhex("520f986b998545b4785e0defbc4f3c1203f22de2374a3d53cb7a7fe9fea309c5")


url = b"http://img.example.com/pretty/image.jpg"

encoded_url = base64.urlsafe_b64encode(url).rstrip(b"=").decode()
# You can trim padding spaces to get good-looking url
encoded_url = '/'.join(textwrap.wrap(encoded_url, 16))

path = "/{resize}/{width}/{height}/{gravity}/{enlarge}/{encoded_url}.{extension}".format(
    encoded_url=encoded_url,
    resize="fill",
    width=300,
    height=300,
    gravity="no",
    enlarge=1,
    extension="png",
).encode()
digest = hmac.new(key, msg=salt+path, digestmod=hashlib.sha256).digest()

protection = base64.urlsafe_b64encode(digest).rstrip(b"=")

url = b'/%s%s' % (
    protection,
    path,
)

print(url.decode())

# without / in url
# /_PQ4ytCQMMp-1w1m_vP6g8Qb-Q7yF9mwghf6PddqxLw/fill/300/300/no/1/aHR0cDovL2ltZy5leGFtcGxlLmNvbS9wcmV0dHkvaW1hZ2UuanBn.png

# with / in url
# /MlF9VpgaHqcmVK3FyT9CTJhfm0rfY6JKnAtxoiAX9t0/fill/300/300/no/1/aHR0cDovL2ltZy5l/eGFtcGxlLmNvbS9w/cmV0dHkvaW1hZ2Uu/anBn.png
