Area of a cinder::PolyLine2f

polyline_area.cpp

// Assumes line does not self intersecting
// Treats the line as closed (you wanted area right?)
// http://www.mathsisfun.com/geometry/area-irregular-polygons.html
float area( PolyLine2f line ) {
	float sum = 0.0;
	if ( line.size() > 1 ) {
		PolyLine2f::iterator it;
		Vec2f prev, curr;
		for ( it = line.begin(), prev = *it++; it != line.end() ; it++ ) {
			curr = *it;
			sum += ( prev.y + curr.y ) / 2.0 * ( curr.x - prev.x );
			prev = curr;
		}
	}
	return sum;
}