zc.py

import numpy as np

# https://stackoverflow.com/questions/63787612/plotly-automatic-zooming-for-mapbox-maps
def zoom_center(lons: tuple = None, lats: tuple = None, lonlats: tuple = None,
                format: str = 'lonlat', projection: str = 'mercator',
                width_to_height: float = 2.0) -> (float, dict):
    """Finds optimal zoom and centering for a plotly mapbox.
    Must be passed (lons & lats) or lonlats.
    Temporary solution awaiting official implementation, see:
    https://github.com/plotly/plotly.js/issues/3434

    Parameters
    --------
    lons: tuple, optional, longitude component of each location
    lats: tuple, optional, latitude component of each location
    lonlats: tuple, optional, gps locations
    format: str, specifying the order of longitud and latitude dimensions,
        expected values: 'lonlat' or 'latlon', only used if passed lonlats
    projection: str, only accepting 'mercator' at the moment,
        raises `NotImplementedError` if other is passed
    width_to_height: float, expected ratio of final graph's with to height,
        used to select the constrained axis.

    Returns
    --------
    zoom: float, from 1 to 20 (I'm using .85 of the original value)
    center: dict, gps position with 'lon' and 'lat' keys

    >>> print(zoom_center((-109.031387, -103.385460),
    ...     (25.587101, 31.784620)))
    (5.75, {'lon': -106.208423, 'lat': 28.685861})
    """
    if lons is None and lats is None:
        if isinstance(lonlats, tuple):
            lons, lats = zip(*lonlats)
        else:
            raise ValueError(
                'Must pass lons & lats or lonlats'
            )

    maxlon, minlon = max(lons), min(lons)
    maxlat, minlat = max(lats), min(lats)
    center = {
        'lon': round((maxlon + minlon) / 2, 6),
        'lat': round((maxlat + minlat) / 2, 6)
    }

    # longitudinal range by zoom level (20 to 1)
    # in degrees, if centered at equator
    lon_zoom_range = np.array([
        0.0007, 0.0014, 0.003, 0.006, 0.012, 0.024, 0.048, 0.096,
        0.192, 0.3712, 0.768, 1.536, 3.072, 6.144, 11.8784, 23.7568,
        47.5136, 98.304, 190.0544, 360.0
    ])

    if projection == 'mercator':
        margin = 1.2
        height = (maxlat - minlat) * margin * width_to_height
        width = (maxlon - minlon) * margin
        lon_zoom = np.interp(width, lon_zoom_range, range(20, 0, -1))
        lat_zoom = np.interp(height, lon_zoom_range, range(20, 0, -1))
        zoom = round(min(lon_zoom, lat_zoom) * .85, 2)
    else:
        raise NotImplementedError(
            f'{projection} projection is not implemented'
        )

    return zoom, center