polyline.py

# From https://github.com/hicsail/polyline
#
# ! osrm uses lon, lat order, code adapted for that !
#
# Copyright (c) 2014 Bruno M. Custódio
# Copyright (c) 2019 Frederick Jansen
# 
# 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.


def decodePolyline(expression, precision=5):
    def _trans(value, index):
        byte, result, shift = None, 0, 0

        while byte is None or byte >= 0x20:
            byte = ord(value[index]) - 63
            index += 1
            result |= (byte & 0x1f) << shift
            shift += 5
            comp = result & 1

        return ~(result >> 1) if comp else (result >> 1), index

    coordinates, index, lat, lng, length, factor = [], 0, 0, 0, len(expression), float(10 ** precision)

    while index < length:
        lat_change, index = _trans(expression, index)
        lng_change, index = _trans(expression, index)
        lat += lat_change
        lng += lng_change
        coordinates.append((lng / factor, lat / factor))

    return coordinates