googlemaps/lib/utils/encodePolylines.js

A simple way to query the Google Maps API from Node.js

var _encodeNumber = require('./encodeNumber');

function _encodeSignedNumber(num) {

  var sgn_num = num << 1;

  if (num < 0) {
    sgn_num = ~(sgn_num);
  }

  return _encodeNumber(sgn_num);

}


/**
 * Algorithm pull from Google's definition of an encoded polyline
 *
 * Google documentation reference: https://developers.google.com/maps/documentation/utilities/polylinealgorithm
 */
module.exports = function(points) {

  // Dear maintainer:
  //
  // Once you are done trying to 'optimize' this routine,
  // and have realized what a terrible mistake that was,
  // please increment the following counter as a warning
  // to the next guy:
  //
  // total_hours_wasted_here = 11
  //
  var i, dlat, dlng;
  var plat = 0;
  var plng = 0;
  var encoded_points = [];

  if (typeof points == 'string') {
    points = points.split('|');
  }

  for (i = 0; i < points.length; i++) {
    var point = points[i].split(',');
    var lat = point[0];
    var lng = point[1];
    var late5 = Math.round(lat * 1e5);
    var lnge5 = Math.round(lng * 1e5);
    dlat = late5 - plat;
    dlng = lnge5 - plng;
    plat = late5;
    plng = lnge5;
    encoded_points.push( _encodeSignedNumber(dlat) + _encodeSignedNumber(dlng) );
  }

  return encoded_points.join('');

};