Mapnik Maps on the Command-Line

Nik2img is a third-party program that allows you to easily generate mapnik graphics from Mapnik xml or Cascadenik mml.

• No python coding is required, only a working Mapnik installation and an XML mapfile.
• Nik2img has a variety of options that make it a useful mapfile debugger.
• Using Nik2img is an easy way to test and develop your xml mapfiles before launching on a server.
• Nik2img should automatically open the rendered map once completed.
• Like Mapnik, it should run on both Mac, Linux, and Windows

To Install:

• Download from http://code.google.com/p/mapnik-utils/
• Or use easy_install:

  $ sudo easy_install -U nik2img
  

Note: These instructions are for the nik2img 0.3.0 release or above.

If you want to render your XML mapfile just do:

$ nik2img.py your_mapfile.xml your_map_rendered.png

• _{Note: The nik2img.py default output is a 600,300 pixel png, rendered at the maximum extent of all your layers}

And say you want to see your map reprojected ('--srs') to Google Spherical Mercator, use the url (or an epsg:code):

$ nik2img.py map.xml map.png --srs http://spatialreference.org/ref/user/6/

• Note: the above projection can also be called with '--srs 900913'

Or you want to test all the output formats ('-f all') of Mapnik's AGG and Cairo renderers and see Verbose debugging output ('-v'):

$ nik2img.py map.xml maps/ -f all -v

Or you want to run in 'Dry Run' mode('-n') and output no maps, but step through each part of the rendering process using 2 second pauses ('--pause') at each step to watch the progress, and finally set a python debugger trace ('--trace-steps') at step 5 to enter interactive mode:

Well, admit you are crazy, but do it like:

$ nik2img.py map.xml maps -n --pause 2 --trace-step 5 # in this case the pdb_trace() is set immediately following load_map()

• _{Note: The python debugger tool emulates your map being loaded and rendered by a custom python script within the python interpreter, allowing you to play around and learn the Mapnik python bindings like:}

  STEP: 5 // --> BBOX (max extent of all layers) is: Envelope(-180.0,-93.188202,180.0,86.811798)
  Total time: 6.58748102188 seconds | Last step: 5.00679016113e-06 seconds
  
  >>> Entering PDB interpreter
  --Return--
  > /usr/local/bin/nik2img.py(131)set_trace()->None
  -> pdb.set_trace()
  
  (Pdb) self.map
  <mapnik_utils.metaclass_injectors.Map object at 0x40ef30>
  (Pdb) self.map.scale()
  0.096269288333333425
  (Pdb) self.map.envelope()
  Envelope(-124.731422,17.9099933333,-66.969849,56.4177086667)
  (Pdb) self.map.envelope().center()
  Coord(-95.8506355,37.163851)
  (Pdb) self.map.background
  <mapnik._mapnik.Color object at 0x454bc8>
  (Pdb) print(self.map.background)
  rgb(140,182,211)
  (Pdb) self.map.srs
  '+proj=latlong +datum=WGS84'
  

• _{Then do:}

  (Pdb) continue # will leave the pdb intepreter
  

And for all the options available do:

$ nik2img.py -h