Re: [pygame] Polygon Area Calculation?

[Ron Dippold <sizer@xxxxxxxxxx>]

Not built in, but here's something I wrote a while ago based on calculating the consecutive trapezoids along the axis - this is a common algorithm. Note the caveats in the method docs.

   - Ron


def poly_area( points ):
	"""
	Returns the area of any polygon IF the edges don't cross and
	the points are given in order around the edge.
	
	points are [ (x,y), (x,y) ... ]
	"""
	
	area = 0
	# start with the last point so we close it (won't hurt if it already is)
	pt1 = points[-1]
	for pt2 in points:
		# we save the /2.0 for the return
		area += ( pt2[0] - pt1[0] ) * ( pt2[1] + pt1[1] ) # /2.0
		pt1 = pt2

	# counterclockwise poly returns negative area
	if area<0:
		area *= -1

	return area/2.0


Mark S wrote:
> Hi all,
>
> I'm wondering if there is anything built in to pygame that will report 
> the area of a polygon?