tiledata.py

#!/usr/bin/python
# ----------------------------------------------------------------------------
# Download OSM data covering the area of a slippy-map tile
#
# Features:
#  * Cached (all downloads stored in cache/z/x/y/data.osm)
# ----------------------------------------------------------------------------
# Copyright 2008, Oliver White
#
# 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 3 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.  If not, see <http://www.gnu.org/licenses/>.
# ---------------------------------------------------------------------------

import os
import pickle
from urllib.request import urlretrieve

from tilenames import tileEdges


def DownloadLevel():
    """All primary downloads are done at a particular zoom level"""
    return(15)


def GetOsmTileData(z, x, y):
    """Download OSM data for the region covering a slippy-map tile"""
    if(x < 0 or y < 0 or z < 0 or z > 25):
        print("Disallowed (%d,%d) at zoom level %d" % (x, y, z))
        return

    directory = 'cache/%d/%d/%d' % (z, x, y)
    filename = '%s/data.osm.pkl' % (directory)
    if(not os.path.exists(directory)):
        os.makedirs(directory)

    if(z == DownloadLevel()):
        # Download the data
        s, w, n, e = tileEdges(x, y, z)
        # /api/0.6/map?bbox=left,bottom,right,top
        URL = 'http://api.openstreetmap.org/api/0.6/map?bbox={},{},{},{}'.format(
            w, s, e, n)

        if(not os.path.exists(filename)):  # TODO: allow expiry of old data
            urlretrieve(URL, filename)
        return(filename)

    elif(z > DownloadLevel()):
        # use larger tile
        while(z > DownloadLevel()):
            z = z - 1
            x = int(x / 2)
            y = int(y / 2)
        return(GetOsmTileData(z, x, y))
    return(None)


if(__name__ == "__main__"):
    """test mode"""
    print(GetOsmTileData(15, 7700, 13546))