Apple iOS compatible image crop for contact/vcard images

apple_contact_picture_crop.py

#!/usr/bin/env python3

from PIL import Image
import io
import logging
import vobject
import base64
import hashlib

"""
Copyright 2021, Andreas Thienemann

This program is free software: you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program. If not, see <http://www.gnu.org/licenses/>.
"""

def apple_crop_photo(self, photo, vcard):
    """Crop an Apple contact picture accordingly.
    Apple on iOS and MacOS seems to store vcards with an URL to the original
    picture on the iCloud servers.

    Any cropping needed happens on the end device at display time.

    An example for this can look like the following taken from a vcard object:

    PHOTO;X-ABCROP-RECTANGLE=ABClipRect_1&385&218&635&635&Zqy85whZ4ZukGCMpiKdrM
        g;VALUE=uri:https://gateway.icloud.com/contacts/[redacted]/ck/card/[photo_...
        ..._id]

    X-ABCROP-RECTANGLE has the following parameters, separated by ampersands (&):
        * ABClipRect_1 = crop using a rectangle. Not seen any other cropping methods.
        * 385 = x: Distance from the left edge of the source image
        * 218 = y: Distance from the bottom edge of the source image
        * 635 = x': Width of the cropped image
        * 635 = y': Height of the cropped image
        * Zqy85whZ4ZukGCMpiKdrMg = base64 encoded md5hash (.digest(), not .hexdigest())
        of the image on the server.

    The y-axis is a bit weird as the y axis is normally taken from the top edge of the
    picture but Apple seems to measure the distance from the bottom edge of the input
    image to the bottom of the crop box..."""

    params = vcard.photo.params["X-ABCROP-RECTANGLE"][0].split("&")
    # No cropping needed
    if params[0] != "ABClipRect_1":
        logging.debug("Photo has no cropping parameters, returning as is.")
        return photo

    img = Image.open(io.BytesIO(photo))
    imgwidth, imgheight = img.size
    x, y, width, height = [int(x) for x in params[1:5]]
    # Recalculate y: Apple calculates y from the bottom edge while pillow calculates y
    # from the top edge
    y_orig = y
    y = imgheight - y - height
    box = (x, y, x + width, y + height)
    img = Image.open(io.BytesIO(photo))
    img = img.crop(box)
    with io.BytesIO() as output:
        img.save(output, format="PNG")
        contents = output.getvalue()
    logging.debug(
        "Photo cropped to %s.", {"apple": (x, y_orig, width, height), "pillow": box}
    )
    return contents