tileget.py

# Downloads all the tiles at full resolution from a directory of Zoomify tiles.
# Requires `eventlet` for multithreaded HTTP requests

import eventlet
from eventlet.green import urllib2
from math import floor, ceil, pow

BASE_URL = "http://www.theatlantic.com/media/interactives/2015/11/colorado-satellite-photo/tiles/"
DOWNLOAD_DIR = "tiles/"

IMAGE_WIDTH = 10644.0
IMAGE_HEIGHT = 13305.0

ZOOM_LEVEL = 6

TILE_SIZE = 256.0

def getGridSize(width, height):
  return (ceil(width / TILE_SIZE), ceil(height / TILE_SIZE))

def calcTiles():
  width = IMAGE_WIDTH
  height = IMAGE_HEIGHT

  g_sizes = [getGridSize(width, height)]

  while width > TILE_SIZE or height > TILE_SIZE:
    width = width / 2
    height = height / 2
    g_sizes.append(getGridSize(width, height))

  return g_sizes

GRID_SIZES = list(reversed(calcTiles()))

def getTileGroup(x, y):
  # based on https://github.com/turban/Leaflet.Zoomify
  zoom = ZOOM_LEVEL
  num = 0

  for i in range(0, zoom):
    grid_size = GRID_SIZES[i]
    num += grid_size[0]*grid_size[1]

  num += y * GRID_SIZES[zoom][0] + x
  return floor(num / 256)

# Quick TileGroup tests
# ---------------------
# print "%s should be %s -> %s" % (getTileGroup(16,33), 8, getTileGroup(16,33) == 8)
# print "%s should be %s -> %s" % (getTileGroup(28,28), 7, getTileGroup(28,28) == 7)
# print "%s should be %s -> %s" % (getTileGroup(0,0), 2, getTileGroup(0,0) == 2)
# print "%s should be %s -> %s" % (getTileGroup(41,40), 9, getTileGroup(41,40) == 9)
# print "%s should be %s -> %s" % (getTileGroup(40,49), 11, getTileGroup(40,49) == 11)
# print "%s should be %s -> %s" % (getTileGroup(39,43), 10, getTileGroup(39,43) == 10)
# print "%s should be %s -> %s" % (getTileGroup(0,31), 8, getTileGroup(0,31) == 8)
# print "%s should be %s -> %s" % (getTileGroup(1,31), 8, getTileGroup(1,31) == 8)
# print "%s should be %s -> %s" % (getTileGroup(2,37), 9, getTileGroup(2,37) == 9)
# print "%s should be %s -> %s" % (getTileGroup(3,31), 8, getTileGroup(3,31) == 8)
# print "%s should be %s -> %s" % (getTileGroup(3,37), 9, getTileGroup(3,37) == 9)

def getTileURL(x,y):
  group = getTileGroup(x,y)
  return "%sTileGroup%d/%s-%d-%d.jpg" % (BASE_URL, group, 6, x, y)

def getListOfURLs():
  urls = []
  for x in range(int(GRID_SIZES[6][0])):
    for y in range(int(GRID_SIZES[6][1])):
      urls.append({
        'x': x,
        'y': y,
        'url': getTileURL(x,y)
      })
  return urls

def fetchImage(img):
  return {
    'body': urllib2.urlopen(img['url']).read(),
    'img': img
  }

urls = getListOfURLs()
pool = eventlet.GreenPool(size=16)

for response in pool.imap(fetchImage, urls):
  body = response['body']
  img = response['img']
  f = open('%s%s-%s.jpg' % (DOWNLOAD_DIR, img['x'], img['y']), 'wb')
  f.write(body)
  f.close()

tilestitch.py

# Stitches together tiles grabbed by `tileget.py` to make a big image
# Requires PIL (use Pillow)

from math import floor
from PIL import Image

IMAGE_WIDTH = 10644
IMAGE_HEIGHT = 13305

TILE_SIZE = 256

DOWNLOAD_DIR = "tiles/"

newimg = Image.new('RGB', (IMAGE_WIDTH, IMAGE_HEIGHT))

for x in xrange(0, IMAGE_WIDTH, TILE_SIZE):
  for y in xrange(0, IMAGE_HEIGHT, TILE_SIZE):
    im = Image.open("%s%d-%d.jpg" % (DOWNLOAD_DIR, floor(x/TILE_SIZE), floor(y/TILE_SIZE)))
    newimg.paste(im, (x, y))

newimg.save('stitched.jpg')