Manipulate TopoJSON, such as to merge shapes, and convert it back to GeoJSON.

The topo_client package provides tools for manipulating TopoJSON, such as to merge shapes or quantize coordinates, and for converting back to GeoJSON (using feature) for rendering with standard tools such as GeoPath. For example, bl.ocks.org/3783604:

import 'dart:convert';

import 'package:d4_geo/d4_geo.dart';
import 'package:http/http.dart' as http;

void main() async {
  var path = GeoPath();

  String url = "https://d3js.org/us-10m.v1.json";
  final response = await http.get(Uri.parse(url));

  path(jsonDecode(response.body));
}