zoom.py 文件源码

def get_zoom(self, geom):
        "Returns the optimal Zoom level for the given geometry."
        # Checking the input type.
        if not isinstance(geom, GEOSGeometry) or geom.srid != 4326:
            raise TypeError('get_zoom() expects a GEOS Geometry with an SRID of 4326.')

        # Getting the envelope for the geometry, and its associated width, height
        # and centroid.
        env = geom.envelope
        env_w, env_h = self.get_width_height(env.extent)
        center = env.centroid

        for z in range(self._nzoom):
            # Getting the tile at the zoom level.
            tile_w, tile_h = self.get_width_height(self.tile(center, z).extent)

            # When we span more than one tile, this is an approximately good
            # zoom level.
            if (env_w > tile_w) or (env_h > tile_h):
                if z == 0:
                    raise GoogleMapException('Geometry width and height should not exceed that of the Earth.')
                return z - 1

        # Otherwise, we've zoomed in to the max.
        return self._nzoom - 1