from django.contrib.gis.db.models.fields import GeometryField
#from django.contrib.gis.gdal import Envelope
from django.contrib.gis.geos import Polygon
from django.utils import simplejson
from django.http import HttpResponse
#from django.db.models.fields.related import ManyRelatedManager
# also need to check out:
# http://code.google.com/p/dojango/source/browse/trunk/dojango/util/__init__.py#82
# example usages:
"""
def a_shapes(request):
ids = request.GET.get('ids').split(',')
mimetype = 'text/plain' #'application/javascript; charset=utf8'
pretty_print = True
if ids:
qs = WorldBorders.objects.filter(affiliates__in=ids).annotate(num_a=Count('affiliates')).filter(num_a__gt=0)
else:
qs = WorldBorders.objects.none()
return render_to_geojson(qs,
extra_attributes=['num_a','affiliates_set'],
geom_attribute='point',
included_fields=['id','name'],
mimetype=mimetype,
proj_transform=900913,
pretty_print=pretty_print
)
def responses(qs,type_='countries',pretty_print=True,mimetype='text/plain'):
if type_ == 'locations':
qs = qs.geolocations()
return render_to_geojson(qs,
excluded_fields=['json'],
geom_field='point',
proj_transform=900913,
mimetype=mimetype,
pretty_print=pretty_print
)
elif type_ == 'affiliates':
qs = qs.exclude(geokeywords='').attach_locations()
return render_to_geojson(qs,
included_fields=['id','_geokeywords_cache'],
geom_attribute='point',
extra_attributes=['name'],
proj_transform=900913,
mimetype=mimetype,
pretty_print=pretty_print
)
elif type_ == 'countries':
qs2 = W.objects.filter(affiliates__in=qs).annotate(num_a=Count('affiliates')).filter(num_a__gt=0)
return render_to_geojson(qs2,
extra_attributes=['num_a'],
#geom_attribute='point',
mimetype=mimetype,
pretty_print=pretty_print
)
else:# type_ == 'countries' or type is None:
if len(qs) > 10:
# this is a limit, weird huh?
# requires another all() otherwise it
# returns a list!
qs = qs.all()[:10]
return render_to_geojson(qs,
included_fields=['id','_geokeywords_cache'],
geom_attribute='countries.unionagg',
extra_attributes=['name'],
mimetype=mimetype,
pretty_print=pretty_print
)
"""
def render_to_geojson(query_set, geom_field=None, geom_attribute=None, extra_attributes=[],mimetype='text/plain', pretty_print=False, excluded_fields=[],included_fields=[],proj_transform=None):
'''
Shortcut to render a GeoJson FeatureCollection from a Django QuerySet.
Currently computes a bbox and adds a crs member as a sr.org link
'''
excluded_fields.append('_state')
collection = {}
if hasattr(query_set,'_meta'): # its a model instance
fields = query_set._meta.fields
query_set = [query_set]
else:
fields = query_set.model._meta.fields
if geom_attribute:
geometry_name = geom_attribute
geo_field = None
if '.' in geom_attribute:
prop, meth = geom_attribute.split('.')
if len(query_set):
p = getattr(query_set[0],prop)
geo_field = getattr(p,meth)
if callable(geo_field):
geo_field = geo_field()
else:
if len(query_set):
geo_field = getattr(query_set[0],geom_attribute)
if callable(geo_field):
geo_field = geo_field()
if not geo_field:
srid = 4326
else:
srid = geo_field.srid
else:
geo_fields = [f for f in fields if isinstance(f, GeometryField)]
#attempt to assign geom_field that was passed in
if geom_field:
#import pdb;pdb.set_trace()
geo_fieldnames = [x.name for x in geo_fields]
try:
geo_field = geo_fields[geo_fieldnames.index(geom_field)]
except:
raise Exception('%s is not a valid geometry on this model' % geom_field)
else:
if not len(geo_fields):
raise Exception('There appears to be no valid geometry on this model')
geo_field = geo_fields[0] # no support yet for multiple geometry fields
#remove other geom fields from showing up in attributes
if len(geo_fields) > 1:
for field in geo_fields:
if field.name not in excluded_fields:
excluded_fields.append(field.name)
geometry_name = geo_field.name
srid = geo_field.srid
if proj_transform:
to_srid = proj_transform
else:
to_srid = srid
# Gather the projection information
crs = {}
crs['type'] = "link"
crs_properties = {}
crs_properties['href'] = 'http://spatialreference.org/ref/epsg/%s/' % to_srid
crs_properties['type'] = 'proj4'
crs['properties'] = crs_properties
collection['crs'] = crs
collection['srid'] = to_srid
# Build list of features
features = []
if query_set.distinct():
for item in query_set:
feat = {}
feat['type'] = 'Feature'
if included_fields:
d = {}
for f in included_fields:
if hasattr(item,f):
d[f] = getattr(item,f)
else:
d = item.__dict__.copy()
for field in excluded_fields:
if field in d.keys():
d.pop(field)
if geometry_name in d:
d.pop(geometry_name)
for attr in extra_attributes:
a = getattr(item,attr)
# crappy way of trying to figure out it this is a
# m2m, aka 'ManyRelatedManager'
if hasattr(a,'values_list'):
a = list(a.values_list('id',flat=True))
if callable(a):
d[attr] = a()
else:
d[attr] = a
if '.' in geometry_name:
prop, meth = geometry_name.split('.')
a = getattr(item,prop)
g = getattr(a,meth)
if callable(g):
g = g()
else:
g = getattr(item,geometry_name)
if g:
if proj_transform:
g.transform(proj_transform)
feat['geometry'] = simplejson.loads(g.geojson)
feat['properties'] = d
features.append(feat)
else:
pass #features.append({'type':'Feature','geometry': {},'properties':{}})
# Label as FeatureCollection and add Features
collection['type'] = "FeatureCollection"
collection['features'] = features
# Attach extent of all features
if query_set:
ex = None
query_set.query.distinct = False
if hasattr(query_set,'agg_extent'):
ex = [x for x in query_set.agg_extent.tuple]
elif '.' in geometry_name:
prop, meth = geometry_name.split('.')
a = getattr(item,prop)
if a:
ex = [x for x in a.extent()]
else:
# make sure qs does not have .distinct() in it...
ex = [x for x in query_set.extent()]
if ex:
if proj_transform:
poly = Polygon.from_bbox(ex)
poly.srid = srid
poly.transform(proj_transform)
ex = poly.extent
collection['bbox'] = ex
# Return response
response = HttpResponse()
if pretty_print:
response.write('%s' % simplejson.dumps(collection, indent=1))
else:
response.write('%s' % simplejson.dumps(collection))
response['Content-length'] = str(len(response.content))
response['Content-Type'] = mimetype
return response