Django WMS Framework¶
The Django WMS Framework is a toolkit that makes it easy to integrate a Web Map Service (WMS) or a x-y-z Tile Map Service into a Django project. Rendering of both vector and raster data formats are supported.
The processing of spatial data in django-wms relies on MapServer and its python bindings MapScript. Raster data integration depends on the django-raster package. The use of PostGIS as the database backend is required as well, for raster integration PostGIS >= 2.0 is required (see also django-raster package).
Install package with pip install django-wms
Add “wms” to your INSTALLED_APPS setting like this
INSTALLED_APPS = ( ... 'wms', )
The structure of django-wms is closely tied to how MapServer works.
The spatial data rendering in django-wms relies on MapScript, the python-bindings for MapServer. The basic funcitonality of django-wms is to use mapscript to dynamically produce directives for MapServer. To render spatial data, MapServer is configured through MapFiles in which global WMS parameters, layers and cartograpy styles are defined.
The concept of MAP directives is translated into a WmsMap class. LAYER definitions and classes for symbology and cartography are represented in the WmsLayer class within django-wms. A set of SYMBOL directives for drawing point data are preconfigured as well.
MapScript has its own class definitions for those directives, django-wms simply makes them easy to use in a django project.
Web requests in django-wms are handled through a class based view module WmsView. The view can be hooked into a url and will take care of handling WMS and TMS requests automatically.
To create a mapping service, subclass the django-wms layer, map and view classes and connect them to an existing model in django that has a spatial field (such as Point, Polygon, MultiPolygon or Raster). An example wms_config.py module could be specified as follows
### wms_config.py # Load django-wms classes from wms import maps, layers, views # Load model with spatial field (Point, Polygon, MultiPolygon) from myapp.models import MySpatialModel # Subclass the WmsLayer class and point it to a spatial model # use WmsVectorLayer for vector data and WmsRasterLayer for rasters class MyWmsLayer(layers.WmsVectorLayer): model = MySpatialModel # Subclass the WmsMap class and add the layer to it class MyWmsMap(maps.WmsMap): layer_classes = [ MyWmsLayer ] # Subclass the WmsView to create a view for the map class MyWmsView(views.WmsView): map_class = MyWmsMap
With the WmsView subclass in place, the only thing left to do to create a functional map service is to hook the view into a url. An example url configuration urls.py could be
### urls.py # Import the wms view from myproject.wms_config import MyWmsView # Add url patterns to setup map services from the view urlpatterns = patterns('', # This creates a WMS endpoint url(r'^wms/$', MyWmsView.as_view(), name='wms'), # This creates a TMS endpoint url(r'^tile/(?P<layers>[^/]+)/(?P<z>[0-9]+)/(?P<x>[0-9]+)/(?P<y>[0-9]+)(?P<format>\.jpg|\.png)$', MyWmsView.as_view(), name='tms'), )
The django-wms package will automatically detect the first spatial field it can find in MySpatialModel and create a WMS endpoint from the class based view. If the three arguments x, y and z are found in the urlpattern, the view functions as TMS endpoint.