src/tim/prune/function/srtm/viewfinder/build-db.py

   1 #!/usr/bin/python3
   2
   3 import os
   4 import urllib.request
   5
   6 from html.parser import HTMLParser
   7
   8 COMMON_PREFIX = "http://viewfinderpanoramas.org/"
   9 COMMON_SUFFIX = ".zip"
  10
  11 def fetch_new_map():
  12     fetch_to_file(COMMON_PREFIX + "Coverage%20map%20viewfinderpanoramas_org3.htm",
  13                   "coverage-dem3.html")
  14     fetch_to_file(COMMON_PREFIX + "Coverage%20map%20viewfinderpanoramas_org1.htm",
  15                   "coverage-dem1.html")
  16
  17 def fetch_to_file(url, fname):
  18     if os.path.exists(fname):
  19         return
  20     req = urllib.request.urlopen(url)
  21     assert req.getcode() == 200, req.read()
  22     with open(fname, "w") as f:
  23         f.write(req.read().decode("utf-8"))
  24
  25 fetch_new_map()
  26
  27 class CoverageDEM3MapParser(HTMLParser):
  28     def __init__(self, *args, **kwargs):
  29         super().__init__(*args, **kwargs)
  30         self.coords_to_link = {}
  31         self.image_scale = 0
  32
  33     @staticmethod
  34     def _get_attr(attrs, attrname):
  35         return next(val for key, val in attrs if key == attrname)
  36
  37     def handle_starttag(self, tag, attrs):
  38         if tag == "area":
  39             coordattr = self._get_attr(attrs, "coords")
  40             coords = tuple(int(c) for c in coordattr.split(", "))
  41             assert len(coords) == 4, "Unexpected tag: %s, %s" % (tag, attrs)
  42
  43             link = self._get_attr(attrs, "href")
  44             assert link.startswith(COMMON_PREFIX)
  45             link = link[len(COMMON_PREFIX):]
  46             assert link.endswith(COMMON_SUFFIX)
  47             link = link[:-len(COMMON_SUFFIX)]
  48
  49             self.coords_to_link[coords] = link
  50         if tag == "img":
  51             width = int(self._get_attr(attrs, "width"))
  52             height = int(self._get_attr(attrs, "height"))
  53             assert width == 2 * height
  54             self.image_scale = width / 360
  55
  56 def populate_links(fname, lats_to_link):
  57     parser = CoverageDEM3MapParser()
  58     with open(fname) as f:
  59         parser.feed(f.read())
  60
  61     scale = parser.image_scale
  62     for coords in parser.coords_to_link:
  63         xmin, ymin, xmax, ymax = coords
  64         for x in range(int(xmin / scale), int(xmax / scale)):
  65             for y in range(int(ymin / scale) + 1, int(ymax / scale) + 1):
  66                 lats_to_link[90 - y, x - 180] = parser.coords_to_link[coords]
  67
  68 def self_test_dem3(lats_to_link):
  69     lat = 44
  70     while lat <= 47:
  71         lng = 0
  72         while lng <= 5:
  73             assert "L31" in lats_to_link[lat, lng]
  74             lng += 1
  75         lat += 1
  76
  77 def self_test_dem1(lats_to_link):
  78     assert "TATRA" in lats_to_link[49, 19]
  79     for lat, lng in lats_to_link:
  80         assert -90 <= lat <= 89
  81         assert -180 <= lng <= 179, lng
  82
  83 def write_db(dest, lats_to_link):
  84     with open(dest, "w") as f:
  85         for lat in range(-90, 90):
  86             for lng in range(-180, 180):
  87                 if (lat, lng) in lats_to_link:
  88                     print("%d %d %s" % (lat, lng,
  89                                         lats_to_link.get((lat, lng))),
  90                           file=f)
  91
  92 lats_to_link = {}
  93 populate_links("coverage-dem3.html", lats_to_link)
  94 self_test_dem3(lats_to_link)
  95 populate_links("coverage-dem1.html", lats_to_link)
  96 self_test_dem1(lats_to_link)
  97
  98 write_db("tiles.dat", lats_to_link)