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encodedpolyline.js
~~~~~~~~~~~~~~~~~~

Encoding and decoding of encoded polylines.  This script implements
the Encoded Polyline Algorithm as used by Google Maps and other map
applications.

* Usage

  <script src=encodedpolyline.js></script>
  <script>
    console.log (EncodedPolyline.encode ([[lat, lon], ...], 1e5));
    console.log (EncodedPolyline.decode (input, 2, 1e5));
  </script>

* Methods

Following methods are available:

  encoded = EncodedPolyline.encode (decoded, f)

    Encodes the list of items and returns the result string.

    The first argument must be an Array of Arrays, where the inner
    Arrays must contain same numbers of items.  Each item of the inner
    Arrays must be numbers.

    To encode a list of pairs of latitude and longitude, as used by
    Google Maps, specify the list of latitude and longitude (both in
    decimal), as an Array of Arrays, and the factor value |1e5|, as
    the arguments.

  decoded = EncodedPolyline.decode (encoded, n, f)

    Decodes the encoded polyline string and returns the result list.

    The second argument represents the number of the items in each
    pair.

    To decode a polyline encoded list of pairs of latitude and
    longitude, as used by Google Maps, specify the encoded string, the
    number of items in each pair |2| (i.e. latitude and longitude),
    and the factor value |1e5|.

    The method returns an Array of Arrays, where inner Arrays
    represent the pairs in the list.  When the input is broken, the
    returned list might be incomplete.

Please note that the factor value I<$f> affects the precision of
encoded numbers, i.e. whether the original value can be obtained by
encoding a number and then decoding its result.  When /n/ * /f/ is an
integer, the exact number /n/ can be obtained.

* Specification

Encoded Polyline Algorithm Format
<https://developers.google.com/maps/documentation/utilities/polylinealgorithm>.

* See also

SuikaWiki: Encoded Polyline
<https://wiki.suikawiki.org/n/Encoded%20Polyline>.

* Author

Wakaba <[email protected]>.

* License

Copyright 2016 Wakaba <[email protected]>.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.