gistfile1.py

#!/usr/bin/python


import os
import urllib2
from PIL import Image


BASE = 'http://imgs.xkcd.com/clickdrag'
N, E, S, W = [14,48,25,33]


def tiles():
    """Generator iterating over all available tile filenames.
    """
    for v in range(-N, S):
        for h in range(-W, E):
            vcoord = "%in" % (-v)
            hcoord = "%sw" % (-h)
            if v >= 0:
                vcoord = "%is" % (v + 1)
            if h >= 0:
                hcoord = "%ie" % (h + 1)

            filename = "%s%s.png" % (vcoord, hcoord)
            #print filename
            yield (h, v), filename


def fetch():
    for pos, filename in tiles():
        url = "%s/%s" % (BASE, filename)
        try:
            data = urllib2.urlopen(url)
            with open(filename, 'w') as f:
                f.write(data.read())
        except urllib2.HTTPError:
            print "Skipping %s" % url


def compose(s=256):
    comp = Image.new('RGB', ((E + W) * s, (N + S) * s))
    black = Image.new('RGB', (s, s), '#000000')
    white = Image.new('RGB', (s, s), '#ffffff')
    for pos, filename in tiles():
        h, v = pos
        if os.path.exists(filename):
            i = Image.open(filename).resize((s, s), Image.ANTIALIAS)
        elif v >= 0:
            i = black
        else:
            i = white
        x = (h + W) * s
        y = (v + N) * s
        comp.paste(i, (x, y))
    comp.save('xkcdworld_%i.png' % s)


if __name__ == '__main__':
    #fetch()
    compose()