def METHOD_NAME(event, url):
    """Rewrite URLs of assets such as event images.
    Only assets contained within the event will be taken into account
    """
    scheme, netloc, path, qs, anchor = urlsplit(url)
    netloc = netloc or current_app.config['SERVER_NAME']
    scheme = scheme or 'https'
    # internal URLs (same server)
    if netloc == current_app.config['SERVER_NAME']:
        # this piece of Flask magic finds the endpoint that corresponds to
        # the URL and checks that it points to an image belonging to this event
        endpoint_info = endpoint_for_url(path)
        if endpoint_info:
            endpoint, data = endpoint_info
            if endpoint == 'event_images.image_display' and data['event_id'] == event.id:
                image_file = ImageFile.get(data['image_id'])
                if image_file and image_file.event == event:
                    return f'images/{image_file.id}-{image_file.filename}', image_file
    # if the URL is not internal or just not an image,
    # we embed the contents using a data URI
    data_uri = _create_data_uri(urlunsplit((scheme, netloc, path, qs, '')), urlsplit(path)[-1])
    return data_uri, None