#!/usr/bin/python3
# lädt und zeigt eine Landkarte, auf man die EAH sieht,
# von Webseite der OpenStreetMap Foundation (AHG, 2022)
import requests
from math import pi, pow, log, radians, tan
from io import BytesIO
from PIL import Image
from subprocess import run

# Variables defining the map of the EAH Jena
lat, lon = 50.918890, 11.569350 # geogr. coordinates
zoom = 18     # zoom factor (integer between 0 and 18)
nx = 3        # number of tiles to add east and west
ny = 2        # number of tiles to add north and south

# Web Mercator projection and scale -> tile coordinates
z = pow(2, zoom) ; b = radians(lat)
x = int( z * (lon/360.0 + 0.5) )
y = int( (z/(2.0*pi)) * (pi-log(tan(pi/4.0+b/2.0))) )

# Download and concatenation of tiles to form an image
kx = ky = 0   # indices for tile column and tile row
o = "https://tile.openstreetmap.org/" # OpenStreetMap
img = Image.new('RGB',((2*nx+1)*256,(2*ny+1)*256))
kx = 0       # reset the index for tile column
for i in range(x-nx,x+nx+1):
    ky = 0   # reset the index for tile row
    for j in range(y-ny,y+ny+1):
        u = o+str(zoom)+"/"+str(i)+"/"+str(j)+".png"
        with requests.get(u) as r:
            tile = Image.open(BytesIO(r.content))
        img.paste(tile,(kx*256,ky*256))
        ky = ky + 1
    kx = kx + 1

# Save and show image (end with key "q")
img.save("geo.png")           # save image
run(["fbi","-a","geo.png"])   # show image with autozoom