js-utl/dist/es6/modules/google.js

A collection of JS utility functions to be used across several applications or libraries.

/*
 * Copyright (c) 2022 Anton Bagdatyev (Tonix)
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

/**
 * Utility functions related to Google.
 */

/**
 * Determines the best zoom level for a Google map.
 *
 * @param {google.maps.LatLngBounds} bounds The bounds.
 * @param {Object} mapDim JS POJO with the properties height and width.
 * @param {number} mapDim.height The height of the map's div.
 * @param {number} mapDim.width The width of the map's div.
 * @return {number} The best zoom level.
 */
export function googleMapBestZoomLevelFromBounds(bounds, mapDim) {
  const WORLD_DIM = {
    height: 256,
    width: 256
  };
  const ZOOM_MAX = 21;

  function latRad(lat) {
    const sin = Math.sin(lat * Math.PI / 180);
    const radX2 = Math.log((1 + sin) / (1 - sin)) / 2;
    return Math.max(Math.min(radX2, Math.PI), -Math.PI) / 2;
  }

  function zoom(mapPx, worldPx, fraction) {
    return Math.floor(Math.log(mapPx / worldPx / fraction) / Math.LN2);
  }

  const ne = bounds.getNorthEast();
  const sw = bounds.getSouthWest();
  const latFraction = (latRad(ne.lat()) - latRad(sw.lat())) / Math.PI;
  const lngDiff = ne.lng() - sw.lng();
  const lngFraction = (lngDiff < 0 ? lngDiff + 360 : lngDiff) / 360;
  const latZoom = zoom(mapDim.height, WORLD_DIM.height, latFraction);
  const lngZoom = zoom(mapDim.width, WORLD_DIM.width, lngFraction);
  return Math.min(latZoom, lngZoom, ZOOM_MAX);
}
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