Properly handle boolean filter

arkindex/documents/api/elements.py

@@ -479,7 +479,7 @@ class ElementsListBase(CorpusACLMixin, DestroyModelMixin, ListAPIView):
                 filters['rotation_angle'] = rotation_angle
 
         if 'mirrored' in self.clean_params:
-            filters['mirrored'] = self.clean_params['mirrored']
+            filters['mirrored'] = self.clean_params['mirrored'].lower() not in ('false', '0')
 
         if self.type_filter:
             filters['type'] = self.type_filter