Easy OpenStreetMap tile displaying for Python

Question

I want to include the open street map (OSM) in my python code.

I have read through lots of webpages regarding to OSM. But unfortunately I\'m a bit lost, regarding wh

Answer 1

Building up on BerndGit's nice answer, I add a slightly modified version which allows to display other contents together with the tiles (using Basemap). Btw I've come across a dedicated library, geotiler (http://wrobell.it-zone.org/geotiler/intro.html), but it requires Python 3.

from mpl_toolkits.basemap import Basemap
import matplotlib.pyplot as plt
import numpy as np

import math
import urllib2
import StringIO
from PIL import Image

def deg2num(lat_deg, lon_deg, zoom):
  lat_rad = math.radians(lat_deg)
  n = 2.0 ** zoom
  xtile = int((lon_deg + 180.0) / 360.0 * n)
  ytile = int((1.0 - math.log(math.tan(lat_rad) + (1 / math.cos(lat_rad))) / math.pi) / 2.0 * n)
  return (xtile, ytile)

def num2deg(xtile, ytile, zoom):
  """
  http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
  This returns the NW-corner of the square. 
  Use the function with xtile+1 and/or ytile+1 to get the other corners. 
  With xtile+0.5 & ytile+0.5 it will return the center of the tile.
  """
  n = 2.0 ** zoom
  lon_deg = xtile / n * 360.0 - 180.0
  lat_rad = math.atan(math.sinh(math.pi * (1 - 2 * ytile / n)))
  lat_deg = math.degrees(lat_rad)
  return (lat_deg, lon_deg)

def getImageCluster(lat_deg, lon_deg, delta_lat,  delta_long, zoom):
    smurl = r"http://a.tile.openstreetmap.org/{0}/{1}/{2}.png"
    xmin, ymax = deg2num(lat_deg, lon_deg, zoom)
    xmax, ymin = deg2num(lat_deg + delta_lat, lon_deg + delta_long, zoom)

    bbox_ul = num2deg(xmin, ymin, zoom)
    bbox_ll = num2deg(xmin, ymax + 1, zoom)
    #print bbox_ul, bbox_ll

    bbox_ur = num2deg(xmax + 1, ymin, zoom)
    bbox_lr = num2deg(xmax + 1, ymax +1, zoom)
    #print bbox_ur, bbox_lr

    Cluster = Image.new('RGB',((xmax-xmin+1)*256-1,(ymax-ymin+1)*256-1) )
    for xtile in range(xmin, xmax+1):
        for ytile in range(ymin,  ymax+1):
            try:
                imgurl=smurl.format(zoom, xtile, ytile)
                print("Opening: " + imgurl)
                imgstr = urllib2.urlopen(imgurl).read()
                tile = Image.open(StringIO.StringIO(imgstr))
                Cluster.paste(tile, box=((xtile-xmin)*255 ,  (ytile-ymin)*255))
            except: 
                print("Couldn't download image")
                tile = None

    return Cluster, [bbox_ll[1], bbox_ll[0], bbox_ur[1], bbox_ur[0]]

if __name__ == '__main__':
    lat_deg, lon_deg, delta_lat,  delta_long, zoom = 45.720-0.04/2, 4.210-0.08/2, 0.04,  0.08, 14
    a, bbox = getImageCluster(lat_deg, lon_deg, delta_lat,  delta_long, zoom)

    fig = plt.figure(figsize=(10, 10))
    ax = plt.subplot(111)
    m = Basemap(
        llcrnrlon=bbox[0], llcrnrlat=bbox[1],
        urcrnrlon=bbox[2], urcrnrlat=bbox[3],
        projection='merc', ax=ax
    )
    # list of points to display (long, lat)
    ls_points = [m(x,y) for x,y in [(4.228, 45.722), (4.219, 45.742), (4.221, 45.737)]]
    m.imshow(a, interpolation='lanczos', origin='upper')
    ax.scatter([point[0] for point in ls_points],
               [point[1] for point in ls_points],
               alpha = 0.9)
    plt.show()