Add center to map API

core/serializers.py

@@ -6,6 +6,10 @@ from django.utils.translation import gettext as _
 from rest_framework import serializers
 from drf_extra_fields.geo_fields import PointField
 from core.models import Profile, Map
+import json
+from django.contrib.gis.geos import Polygon
+from rest_framework.serializers import SerializerMethodField
+from pymbtiles import MBtiles
 
 class UserSerializer(serializers.ModelSerializer):
     class Meta:
@@ -72,9 +76,19 @@ class OwnerSerializer(serializers.ModelSerializer):
         exclude = ('id', 'username', 'password', 'email', 'first_name', 'last_name', 'is_active', 'is_staff', 'is_superuser', 'date_joined', 'groups', 'user_permissions', 'last_login')
 
 class MapSerializer(serializers.ModelSerializer):
+
+    center = SerializerMethodField('get_center_mbtiles')
+
+    def get_center_mbtiles(self, object):
+        with MBtiles(object.file.path) as src:
+            bounds = src.meta['bounds'].split(',')
+            pol = Polygon.from_bbox(bounds)
+            return json.loads(pol.centroid.json)
+        return ''
+
     class Meta:
         model = Map
-        fields = ('id', 'name', 'file')
+        fields = ('id', 'name', 'file', 'center')
 
 class PasswordResetSerializer(serializers.Serializer):
     email = serializers.EmailField()