maps.google.polygon.containsLatLng.js

// Polygon getBounds extension - google-maps-extensions
// https://github.com/tparkin/Google-Maps-Point-in-Polygon
// http://code.google.com/p/google-maps-extensions/source/browse/google.maps.Polygon.getBounds.js
if (!google.maps.Polygon.prototype.getBounds) {
  google.maps.Polygon.prototype.getBounds = function(latLng) {
    var bounds = new google.maps.LatLngBounds(),
      paths = this.getPaths(),
      path,
      p, i;

    for (p = 0; p < paths.getLength(); p++) {
      path = paths.getAt(p);
      for (i = 0; i < path.getLength(); i++) {
        bounds.extend(path.getAt(i));
      }
    }

    return bounds;
  };
}

// Polygon containsLatLng - method to determine if a latLng is within a polygon
google.maps.Polygon.prototype.containsLatLng = function(latLng) {
  // Exclude points outside of bounds as there is no way they are in the poly

  var inPoly = false,
    bounds, lat, lng,
    numPaths, p, path, numPoints,
    i, j, vertex1, vertex2;

  // Arguments are a pair of lat, lng variables
  if (arguments.length == 2) {
    if (
      typeof arguments[0] == "number" &&
      typeof arguments[1] == "number"
    ) {
      lat = arguments[0];
      lng = arguments[1];
    }
  } else if (arguments.length == 1) {
    bounds = this.getBounds();

    if (!bounds && !bounds.contains(latLng)) {
      return false;
    }
    lat = latLng.lat();
    lng = latLng.lng();
  } else {
    console.log("Wrong number of inputs in google.maps.Polygon.prototype.contains.LatLng");
  }

  // Raycast point in polygon method

  numPaths = this.getPaths().getLength();
  for (p = 0; p < numPaths; p++) {
    path = this.getPaths().getAt(p);
    numPoints = path.getLength();
    j = numPoints - 1;

    for (i = 0; i < numPoints; i++) {
      vertex1 = path.getAt(i);
      vertex2 = path.getAt(j);

      if (
        vertex1.lng() <  lng &&
        vertex2.lng() >= lng ||
        vertex2.lng() <  lng &&
        vertex1.lng() >= lng
      ) {
        if (
          vertex1.lat() +
          (lng - vertex1.lng()) /
          (vertex2.lng() - vertex1.lng()) *
          (vertex2.lat() - vertex1.lat()) <
          lat
        ) {
          inPoly = !inPoly;
        }
      }

      j = i;
    }
  }

  return inPoly;
};