generate_image.py

   1 #!/usr/bin/python
   2 #
   3 # Generates a single large PNG image for a UK bounding box
   4 # Tweak the lat/lon bounding box (ll) and image dimensions
   5 # to get an image of arbitrary size.
   6 #
   7 # To use this script you must first have installed mapnik
   8 # and imported a planet file into a Postgres DB using
   9 # osm2pgsql.
  10 #
  11 # Note that mapnik renders data differently depending on
  12 # the size of image. More detail appears as the image size
  13 # increases but note that the text is rendered at a constant
  14 # pixel size so will appear smaller on a large image.
  15
  16 from mapnik import *
  17 import sys, os
  18
  19 if __name__ == "__main__":
  20     try:
  21         mapfile = os.environ['MAPNIK_MAP_FILE']
  22     except KeyError:
  23         mapfile = "osm.xml"
  24     map_uri = "image.png"
  25
  26     #---------------------------------------------------
  27     #  Change this to the bounding box you want
  28     #
  29     #ll = (-6.5, 49.5, 2.1, 59)
  30     ll = (24.32615, 44.10178, 24.37145, 44.1322) # Caracal
  31     ll = (24.30, 44.08, 24.38, 44.14) # Caracal
  32     #---------------------------------------------------
  33
  34     z = 15
  35     imgx = 500 * z
  36     imgy = 1000 * z
  37
  38     m = Map(imgx,imgy)
  39     load_map(m,mapfile)
  40     prj = Projection("+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +no_defs +over")
  41     c0 = prj.forward(Coord(ll[0],ll[1]))
  42     c1 = prj.forward(Coord(ll[2],ll[3]))
  43     bbox = Envelope(c0.x,c0.y,c1.x,c1.y)
  44     m.zoom_to_box(bbox)
  45     im = Image(imgx,imgy)
  46     render(m, im)
  47     view = im.view(0,0,imgx,imgy) # x,y,width,height
  48     view.save(map_uri,'png')