Check whether a point is within a polygon #ruby

point-in-polygon.rb

  def point_in_polygon?(polygonPoints)
    return false if self.latitude.blank? or self.longitude.blank?
    polygonPoints.each do |point|
      point[0] = point[0].to_f
      point[1] = point[1].to_f
    end

    contains_point = false
    i = -1
    j = polygonPoints.size - 1
    while (i += 1) < polygonPoints.size
      a_point_on_polygon = polygonPoints[i]
      trailing_point_on_polygon = polygonPoints[j]
      if point_is_between_the_ys_of_the_line_segment?(a_point_on_polygon, trailing_point_on_polygon)
        if ray_crosses_through_line_segment?(a_point_on_polygon, trailing_point_on_polygon)
          contains_point = !contains_point
        end
      end
      j = i
    end
    contains_point
  end

  private

  def point_is_between_the_ys_of_the_line_segment?(a_point_on_polygon, trailing_point_on_polygon)
    (a_point_on_polygon[0] <= self.latitude && self.latitude < trailing_point_on_polygon[0]) || 
    (trailing_point_on_polygon[0] <= self.latitude && self.latitude < a_point_on_polygon[0])
  end

  def ray_crosses_through_line_segment?(a_point_on_polygon, trailing_point_on_polygon)
    (self.longitude < (trailing_point_on_polygon[1] - a_point_on_polygon[1]) * (self.latitude - a_point_on_polygon[0]) / 
    (trailing_point_on_polygon[0] - a_point_on_polygon[0]) + a_point_on_polygon[1])
  end

based on http://jakescruggs.blogspot.com/2009/07/point-inside-polygon-in-ruby.html but uses an object with lat/long and receives the polygon instead of having the polygon as the object receiving the point

Really helpful script 😄