function to check if cordinates inside polygone for dart and flutter framework

polygone.dart

import 'dart:math';
// function to check if cordinates inside polygone 
bool polygoneContains(List<LatLng> points, num lat, num lng) {
  List<Point<num>> _points =
      points.map((e) => Point<num>(e.latitude, e.longitude)).toList();
  num ax = 0;
  num ay = 0;
  num bx = _points[points.length - 1].x - lat;
  num by = _points[points.length - 1].y - lng;
  int depth = 0;

  for (int i = 0; i < _points.length; i++) {
    ax = bx;
    ay = by;
    bx = _points[i].x - lat;
    by = _points[i].y - lng;

    if (ay < 0 && by < 0) continue; // both "up" or both "down"
    if (ay > 0 && by > 0) continue; // both "up" or both "down"
    if (ax < 0 && bx < 0) continue; // both points on left

    num lx = ax - ay * (bx - ax) / (by - ay);

    if (lx == 0) return true; // point on edge
    if (lx > 0) depth++;
  }

  return (depth & 1) == 1;
}