Get centroid for polygon in Google Maps

gistfile1.coffee

 
google.maps.Polygon::getArea = ->
  points = @getPaths()
 
  area = 0
  i = 0
  j = points.length - 1
 
  while i < points.length
    point1 = points[i]
    point2 = points[j]
    area += point1.lng() * point2.lat()
    area -= point1.lat() * point2.lng()
    j = i
    i++
    
  area /= 2
  area
 
google.maps.Polygon::getCentroid = ->
  points = @getPaths()
 
  x = 0
  y = 0
  i = 0
  j = points.length - 1
 
  while i < points.length
    point1 = points[i]
    point2 = points[j]
    f = point1.lng() * point2.lat() - point2.lng() * point1.lat()
    x += (point1.lng() + point2.lng()) * f
    y += (point1.lat() + point2.lat()) * f
    j = i
    i++
 
  f = @getArea() * 6
 
  new google.maps.LatLng(x / f, y / f)