Determine if a point is inside a given polygon or not
    Polygon is a list of (x,y) pairs.

    [code taken from: http://www.ariel.com.au/a/python-point-int-poly.html]

    let's make an easy square:

    >>> poly = [ (0,0),\
                 (1,0),\
                 (1,1),\
                 (0,1) ]
    >>> pointInsidePolygon(0.5,0.5, poly)
    True
    >>> pointInsidePolygon(1.5,1.5, poly)
    False

def pointInsidePolygon(x, y, poly):
    """
    Determine if a point is inside a given polygon or not
    Polygon is a list of (x,y) pairs.

    [code taken from: http://www.ariel.com.au/a/python-point-int-poly.html]

    let's make an easy square:

    >>> poly = [ (0,0),\
                 (1,0),\
                 (1,1),\
                 (0,1) ]
    >>> pointInsidePolygon(0.5,0.5, poly)
    True
    >>> pointInsidePolygon(1.5,1.5, poly)
    False
    """
    n = len(poly)
    inside = False
    p1x, p1y = poly[0]
    for i in range(n + 1):
        p2x, p2y = poly[i % n]
        if y > min(p1y, p2y):
            if y <= max(p1y, p2y):
                if x <= max(p1x, p2x):
                    if p1y != p2y:
                        xinters = (y - p1y) * (p2x - p1x) / (p2y - p1y) + p1x
                    if p1x == p2x or x <= xinters:
                        inside = not inside
        p1x, p1y = p2x, p2y
    return inside