ggirou · March 21, 2014 13:41 · Mar 21, 2014
diff --git a/center.dart b/center.dart
@@ -0,0 +1,40 @@
+import 'dart:convert';
+import 'dart:html';
+import 'dart:math';
+import 'dart:svg' as svg;
+
+main() {
+  HttpRequest.getString('svg-datas.json').then(JSON.decode).then(calculateGravity);
+}
+
+calculateGravity(Map<String, Map> paths) {
+  paths.forEach((country, data) {
+    var path = data['path'];
+    var el = new svg.PathElement()..setAttribute('d', path);
+    List<Point> points = el.pathSegList
+        .where((ps) => !(ps is svg.PathSegClosePath))
+        .map((p) => new Point(p.x, p.y)).toList();
+    var g = gravity(points);
+
+    print("""  "$country": {
+    "path": "$path",
+    "center": {
+      "x": ${g.x},
+      "y": ${g.y}
+    }
+  },""");
+  });
+}
+
+Point gravity(List<Point> points) {
+  num sumArea = 0, sumX = 0, sumY = 0;
+  for (int i = 0; i < points.length; i++) {
+    var i_p = (i + 1) % points.length;
+    var g = points[i].x * points[i_p].y - points[i_p].x * points[i].y;
+    sumArea += g;
+    sumX += (points[i].x + points[i_p].x) * g;
+    sumY += (points[i].y + points[i_p].y) * g;
+  }
+  sumArea = 3 * sumArea;
+  return new Point((sumX / sumArea).round(), (sumY / sumArea).round());
+}
diff --git a/center.html b/center.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+
+<html>
+  <head>
+  	<meta charset="utf-8">
+  	<meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>center</title>
+  </head>
+
+  <body>   
+    <p id="text"></p>
+    <script type="application/dart" src="center.dart"></script>
+    <!-- for this next line to work, your pubspec.yaml file must have a dependency on 'browser' -->
+    <script src="packages/browser/dart.js"></script>
+  </body>
+</html>