Simplification by zoom level

djgeojson/tests.py

@@ -507,6 +507,24 @@ def test_some_tiles_have_empty_queryset(self):
         self.view.args = [4, 6, 8]
         self.assertEqual(0, len(self.view.get_queryset()))
 
+    def test_simplification_depends_on_zoom_level(self):
+        self.view.simplifications = {6: 100}
+        self.view.args = [6, 8, 4]
+        self.view.get_queryset()
+        self.assertEqual(self.view.simplify, 100)
+
+    def test_simplification_is_default_if_not_specified(self):
+        self.view.simplifications = {}
+        self.view.args = [0, 8, 4]
+        self.view.get_queryset()
+        self.assertEqual(self.view.simplify, None)
+
+    def test_simplification_takes_the_closest_upper_level(self):
+        self.view.simplifications = {3: 100, 6: 200}
+        self.view.args = [4, 8, 4]
+        self.view.get_queryset()
+        self.assertEqual(self.view.simplify, 200)
+
 
 class Address(models.Model):
     geom = GeoJSONField()

djgeojson/views.py

@@ -67,6 +67,8 @@ class TiledGeoJSONLayerView(GeoJSONLayerView):
     height = 256
     tile_srid = 3857
     trim_to_boundary = True
+    """Simplify geometries by zoom level (dict <int:float>)"""
+    simplifications = None
 
     def tile_coord(self, xtile, ytile, zoom):
         """
@@ -95,11 +97,21 @@ def get_queryset(self):
         qs = qs.filter(**{
             '%s__intersects' % self.geometry_field: bbox
         })
+
+        # Simplification dict by zoom level
+        simplifications = self.simplifications or {}
+        z = self.z
+        self.simplify = simplifications.get(z)
+        while self.simplify is None and z < 32:
+            z += 1
+            self.simplify = simplifications.get(z)
+
         # Won't trim point geometries to a boundary
         model_field = qs.model._meta.get_field(self.geometry_field)
         self.trim_to_boundary = (self.trim_to_boundary and
                                  not isinstance(model_field, PointField))
         if self.trim_to_boundary:
             qs = qs.intersection(bbox)
             self.geometry_field = 'intersection'
+
         return qs