generateHeatmap static method

Map<Point<int>, double> generateHeatmap({ required List<HeatPoint> points, required double radius, required double resolution, })

Implementation

static Map<Point<int>, double> generateHeatmap({
  required List<HeatPoint> points,
  required double radius,
  required double resolution,
}) {
  final Distance dist = Distance();
  final Map<Point<int>, double> heatGrid = {};

  for (final p in points) {
    final influenceRadius = radius;

    for (double dx = -influenceRadius; dx <= influenceRadius; dx += resolution) {
      for (double dy = -influenceRadius; dy <= influenceRadius; dy += resolution) {
        final targetLat = p.lat + (dy / 111320.0);
        final targetLng = p.lng + (dx / (111320.0 * cos(p.lat * pi / 180)));

        final d = dist.as(LengthUnit.Meter, LatLng(p.lat, p.lng), LatLng(targetLat, targetLng));

        if (d <= influenceRadius) {
          final weight = p.intensity * exp(-pow(d, 2) / (2 * pow(influenceRadius / 2, 2)));

          final x = ((p.lng + dx) / resolution).floor();
          final y = ((p.lat + dy) / resolution).floor();
          final key = Point(x, y);

          heatGrid.update(key, (v) => v + weight, ifAbsent: () => weight);
        }
      }
    }
  }

  return heatGrid;
}