kmlparser.py

#!/usr/bin/python

# Copyright (C) 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
This package provides implementation of a converter from a kml
file format into Google transit feed format.

The KmlParser class is the main class implementing the parser.

For point geometries, information about stops is extracted from a kml file.
The extractor expects the stops to be represented as placemarks with
a single point.

For line geometries, information about shapes is extracted from a kml file.

"""

import re
import string
import sys
import transitfeed
from transitfeed import util
import xml.dom.minidom as minidom
import zipfile


class Placemark(object):
  def __init__(self):
    self.name = ""
    self.coordinates = []

  def IsPoint(self):
    return len(self.coordinates) == 1

  def IsLine(self):
    return len(self.coordinates) > 1

class KmlParser(object):
  def __init__(self, stopNameRe = '(.*)'):
    """
    Args:
      stopNameRe - a regular expression to extract a stop name from a
                   placemaker name
    """
    self.stopNameRe = re.compile(stopNameRe)

  def Parse(self, filename, feed):
    """
    Reads the kml file, parses it and updated the Google transit feed
    object with the extracted information.

    Args:
      filename - kml file name
      feed - an instance of Schedule class to be updated
    """
    dom = minidom.parse(filename)
    self.ParseDom(dom, feed)

  def ParseDom(self, dom, feed):
    """
    Parses the given kml dom tree and updates the Google transit feed object.

    Args:
      dom - kml dom tree
      feed - an instance of Schedule class to be updated
    """
    shape_num = 0
    for node in dom.getElementsByTagName('Placemark'):
      p = self.ParsePlacemark(node)
      if p.IsPoint():
        (lon, lat) = p.coordinates[0]
        m = self.stopNameRe.search(p.name)
        feed.AddStop(lat, lon, m.group(1))
      elif p.IsLine():
        self.ConvertPlacemarkToShape(p, feed)

  def ParsePlacemark(self, node):
    ret = Placemark()
    for child in node.childNodes:
      if child.nodeName == 'name':
        ret.name = self.ExtractText(child)
      if child.nodeName == 'Point' or child.nodeName == 'LineString':
        ret.coordinates = self.ExtractCoordinates(child)
    return ret

  def ExtractText(self, node):
    for child in node.childNodes:
      if child.nodeType == child.TEXT_NODE:
        return child.wholeText  # is a unicode string
    return ""

  def ExtractCoordinates(self, node):
    coordinatesText = ""
    for child in node.childNodes:
      if child.nodeName == 'coordinates':
        coordinatesText = self.ExtractText(child)
        break
    ret = []
    for point in coordinatesText.split():
      coords = point.split(',')
      ret.append((float(coords[0]), float(coords[1])))
    return ret

  def ConvertPlacemarkToShape(self, p, feed):
    shape = transitfeed.Shape(p.name)
    for (lon, lat) in p.coordinates:
      shape.AddPoint(lat, lon)

    try:
      existing_shape = feed.GetShape(p.name)

      # If the existing shape has the same points, we don't need to add a new
      # shape.
      if existing_shape == shape:
        return

      # If the shape has different points, we need to modify our shape id so as
      # to avoid duplication.
      shape.shape_id += '_%d' % len(feed.GetShapeList())

    except KeyError:
      # No existing shape with that id, so no worries.
      pass

    feed.AddShapeObject(shape)

def main():
  usage = \
"""%prog <input.kml> <output GTFS.zip>

Reads KML file <input.kml> and creates GTFS file <output GTFS.zip> with
placemarks in the KML represented as stops.
"""

  parser = util.OptionParserLongError(
      usage=usage, version='%prog '+transitfeed.__version__)
  (options, args) = parser.parse_args()
  if len(args) != 2:
    parser.error('You did not provide all required command line arguments.')

  if args[0] == 'IWantMyCrash':
    raise Exception('For testCrashHandler')

  parser = KmlParser()
  feed = transitfeed.Schedule()
  feed.save_all_stops = True
  parser.Parse(args[0], feed)
  feed.WriteGoogleTransitFeed(args[1])

  print "Done."


if __name__ == '__main__':
  util.RunWithCrashHandler(main)