def _check_extent(self, layer, geom_query, projection=None, **kwargs): model_projection = geom_query.model._meta.get_field(find_geom_field(geom_query)).srid if projection is not None and projection != model_projection: poly = Polygon.from_bbox(geom_query.extent()) poly.srid = model_projection poly.transform(projection) query_extent = poly.extent else: query_extent = geom_query.extent() # layer.extent is useless, cause it computes extents from geometry, so it bypass geojson's value numpy.testing.assert_almost_equal(json.loads(self.geojson)["bbox"], query_extent, decimal=3)
def _test_render_to_json(self, geom_query, properties=(), **kwargs): "Generic testing function of rendering json from queryset geom_query""" geom_field = find_geom_field(geom_query) self.assertGreater(len(geom_query), 0) ds = self._generate_data_source_from_json(geom_query, properties=properties, **kwargs) self.assertEqual(ds.layer_count, 1) layer = ds[0] self.assertEqual(layer.num_feat, geom_query.count()) self._check_extent(layer, geom_query, **kwargs) self._check_geometry(layer, geom_query, **kwargs) self._check_attributes(layer, geom_query, properties=properties)
def _check_geometry(self, layer, geom_query, projection=None, simplify=None, **kwargs):
model_projection = geom_query.model._meta.get_field(find_geom_field(geom_query)).srid
if projection is not None and projection != model_projection:
# prepare geometry for comparing in requested projection
geom_query = geom_query.transform(projection)
features_data = {}
for feature in geom_query:
if simplify:
features_data[feature.pk] = feature.the_geom.simplify(simplify)
else:
features_data[feature.pk] = feature.the_geom
for feature in layer:
gid = feature["gid"].as_int()
self.assertTrue(feature.geom.geos.equals_exact(features_data[gid], tolerance=0.001))
def render_to_geojson(queryset, projection=None, simplify=None, extent=None, maxfeatures=None, priorityfield=None, properties=None, prettyprint=False):
'''
Shortcut to render a GeoJson FeatureCollection from a Django QuerySet.
Currently computes a bbox and adds a crs member as a sr.org link.
Parameters:
* queryset (django.db.models.query.QuerySet) - queryset of models containing geometry data
* projection (int) - projection code used when geometry data should be transformed to other projection
* simplify (float) - value specifies tolerance in Douglas-Peucker algorithm for simplifying geometry
* extent (django.contrib.gis.geos.Polygon instance) - limits features to features inside extent's bounds
* maxfeatures (int) - gives maximum number of rendered features based on priority field
* priorityfield (string) - name of the priority field used for reducing features
* properties ([(string, string or callable), ...]) - list of feature's non geometry attributes defined as couples \
(title, value), where value can be field name or callable (that accepts a feature instance as argument and returns attribute's value)
* prettyprint (boolean) - flag influencing indentation used in geojson (for better readability)
'''
geom_field = find_geom_field(queryset)
if extent is not None:
#queryset.filter(<geom_field>__intersects=extent)
queryset = queryset.filter(**{'%s__intersects' % geom_field: extent})
if maxfeatures is not None:
if priorityfield is None:
raise RuntimeError("priorityfield must be defined")
queryset.order_by(priority_field)
queryset = queryset[:maxfeatures]
src_projection = None
if queryset.exists():
src_projection = queryset.model._meta.get_field(geom_field).srid
if projection is None:
projection = src_projection
if projection is not None and src_projection != projection:
queryset = queryset.transform(projection)
if properties is None:
properties = [(field.name, field.name) for field in queryset.model._meta.fields]
features = list()
collection = dict()
if src_projection is not None:
crs = dict()
crs[GEOJSON_FIELD_TYPE] = GEOJSON_VALUE_LINK
crs_properties = dict()
crs_properties[GEOJSON_FIELD_HREF] = '%s%s/' % (SPATIAL_REF_SITE, projection)
crs_properties[GEOJSON_FIELD_TYPE] = 'proj4'
crs[GEOJSON_FIELD_PROPERTIES] = crs_properties
collection[GEOJSON_FIELD_CRS] = crs
collection[GEOJSON_FIELD_SRID] = projection
for item in queryset:
feat = dict()
feat[GEOJSON_FIELD_ID] = item.pk
#filling feature properties with dict: {<field_name>:<field_value>}
feat[GEOJSON_FIELD_PROPERTIES] = dict()
for title, attrib in properties:
if attrib == geom_field:
continue
if isroutine(attrib):
value = attrib(item)
else:
value = getattr(item, attrib)
feat[GEOJSON_FIELD_PROPERTIES][title] = __simple_render_to_json(value)
feat[GEOJSON_FIELD_TYPE] = GEOJSON_VALUE_FEATURE
geom = getattr(item, geom_field)
if simplify:
geom = geom.simplify(simplify)
# We have to use gdal.OGRGeometry geometry class directly and without srid parameter
# to prevent creating a SpatialReference instance, which causes memory leaks
feat[GEOJSON_FIELD_GEOMETRY] = simplejson.loads(gdal.OGRGeometry(geom.wkb).json)
features.append(feat)
collection[GEOJSON_FIELD_TYPE] = GEOJSON_VALUE_FEATURE_COLLECTION
collection[GEOJSON_FIELD_FEATURES] = features
if queryset.exists():
if projection is not None and src_projection != projection:
poly = Polygon.from_bbox(queryset.extent())
# We have to use gdal.OGRGeometry geometry class directly and without srid parameter
# to prevent creating a SpatialReference instance, which causes memory leaks
ogr_geom = gdal.OGRGeometry(poly.wkb)
ogr_geom.srs = __get_spatial_reference(src_projection)
ogr_geom.transform(__get_spatial_reference(projection))
collection[GEOJSON_FIELD_BBOX] = ogr_geom.extent
else:
collection[GEOJSON_FIELD_BBOX] = queryset.extent()
if prettyprint == True:
return simplejson.dumps(collection, indent=4)
else:
return simplejson.dumps(collection)