Source Code for Module madrona.common.jsonutils

 1  """ 
 2  GeoJSON helper functions 
 3  """ 
 4  from django.core import serializers 
 5  import json 
 6   
 7 -def get_properties_json(i): 
 8      json_orig = serializers.serialize('json', [i,]) 
 9      # use_natural_keys=True is not reliable; can fail w/ content_type error: 
10      #     'NoneType' object has no attribute 'natural_key' 
11      obj = json.loads(json_orig) 
12      props = obj[0]['fields'] 
13      unwanted_properties = [ 
14          'geometry_final',  
15          'geometry_orig',  
16          'content_type',  
17          'object_id',  
18      ] 
19      for uwp in unwanted_properties: 
20          try: 
21              props.pop(uwp) 
22          except: 
23              pass 
24      # Add uid 
25      props['uid'] = i.uid 
26      return props 
27   
28 -def get_feature_json(geom_json, prop_json): 
29      return """{ 
30          "type": "Feature", 
31          "geometry": %s,  
32          "properties": %s 
33      }""" % (geom_json, prop_json) 
34   
35 -def srid_to_urn(srid): 
36      """ 
37      Take a postgis srid and make it into a OGC CRS URN 
38      As suggested by http://www.geojson.org/geojson-spec.html#named-crs 
39      This is pretty dumb right now and just assumes EPSG as the authority 
40      except for 4326 which uses: 
41        4326 -> urn:ogc:def:crs:OGC:1.3:CRS84 
42      """ 
43      if int(srid) == 4326: 
44          return "urn:ogc:def:crs:OGC:1.3:CRS84" 
45       
46      return "urn:ogc:def:crs:EPSG::%d" % srid 
47   
48 -def srid_to_proj(srid): 
49      """ 
50      Take a postgis srid and return the proj4 string 
51      Useful for custom projections with no authority 
52      """ 
53      from django.contrib.gis.gdal import SpatialReference 
54      srs = SpatialReference(srid)  
55      return srs.proj.strip() 
56