lat_long_zoom_to_tile_URL.py

import os, sys
import math

class Point:
    def __init__(self, x=0.0, y=0.0):
        self.x = x
        self.y = y

class Tile:
    def __init__(self, x=0, y=0):
        self.x = x
        self.y = y

def lat_long_zoom_to_pixel_coords(lat, lon, zoom):
    p = Point()
    sinLat = math.sin(lat * math.pi/180.0)
    x = ((lon + 180) / 360) * 256 * math.pow(2,zoom)
    y = (0.5 - math.log((1 + sinLat) / (1 - sinLat)) /
          (4 * math.pi)) * 256 * math.pow(2,zoom)
    p.x = int(math.floor(x))
    p.y = int(math.floor(y))
    print("\nThe pixel coordinates are x = {} and y = {}".format(p.x, p.y))
    return p

# NOTE - lat_long_zoom_to_pixel_coords and then to a tile will find the tile that
# contains that coordinate - going from tile back to lat long will not (typically)
# return that same coordinate
# I'm unclear if this returns the center of the tile or the top left corner.
def pixel_coords_to_lat_long(p, zoom):
  mapsize = 256 * math.pow(2, zoom)
  x = (min(max(p.x, 0), mapsize - 1) / mapsize) - 0.5
  lon = 360 * x
  y = 0.5 - (min(max(p.y, 0), mapsize - 1) / mapsize)
  lat = 90 - 360 * math.atan(math.exp(-y * 2 * math.pi)) / math.pi
  return lat, lon

def pixel_coords_to_tile_address(x,y):
    t = Tile()
    t.x = int(math.floor(x / 256))
    t.y = int(math.floor(y / 256))
    print("\nThe tile coordinates are x = {} and y = {}".format(t.x, t.y))
    return t

def tile_address_to_pixel_coords(t):
    p = Point()
    p.x = t.x * 256
    p.y = t.y * 256
    return p

def tile_coords_and_zoom_to_quadKey(x, y, zoom):
    quadKey = ''
    for i in range(zoom, 0, -1):
        digit = 0
        mask = 1 << (i - 1)
        if(x & mask) != 0:
            digit += 1
        if(y & mask) != 0:
            digit += 2
        quadKey += str(digit)
    print("\nThe quadkey is {}".format(quadKey))
    return quadKey

def quadKey_to_url(quadKey):
    try:
        f = open('cfg/api_key')
        api_key = f.read()
    except:
        print("Something is wrong with your API key.\n"
               "Do you even have an API key?")

    #TODO get this into a config file, and set up others (Google, OSM, etc)
    tile_url = ("http://t0.tiles.virtualearth.net/tiles/a{}.jpeg?"
                "g=854&mkt=en-US&token={}".format(quadKey, api_key))
    print("\nThe tile URL is: {}".format(tile_url))
    return tile_url


def lat_long_zoom_to_quadKey(lat, lon, zoom):
    pixel = lat_long_zoom_to_pixel_coords(lat, lon, zoom)
    tile = pixel_coords_to_tile_address(pixel.x, pixel.y)
    quadKey = tile_coords_and_zoom_to_quadKey(tile.x, tile.y, zoom)
    return quadKey

def lat_long_zoom_to_URL(lat, lon, zoom):
    pixel = lat_long_zoom_to_pixel_coords(lat, lon, zoom)
    tile = pixel_coords_to_tile_address(pixel.x, pixel.y)
    quadKey = tile_coords_and_zoom_to_quadKey(tile.x, tile.y, zoom)
    tile_url = quadKey_to_url(quadKey)
    return tile_url

if __name__ == "__main__":

    # This script is intended to provide functions to another script.

    # The __main__ function here is for testing and convenience;
    # it accepts a latitude, longitude, and zoom level as arguments and
    # calls the functions that translate those inputs into a tile URL, which
    # is printed to the console along with the pixel and tile coordinates.

    lat = float(sys.argv[1])
    lon = float(sys.argv[2])
    zoom = int(sys.argv[3])

    URL = lat_long_zoom_to_URL(lat, lon, zoom)