def Compute(self, reverse=False, sign=True):
"""Compute the properties of the polygon
:param reverse: if true then clockwise (instead of
counter-clockwise) traversal counts as a positive area
:param sign: if true then return a signed result for the area if the
polygon is traversed in the "wrong" direction instead of returning
the area for the rest of the earth
:return: a tuple of number, perimeter (meters), area (meters^2)
If the object is a polygon (and not a polygon), the perimeter
includes the length of a final edge connecting the current point to
the initial point. If the object is a polyline, then area is nan.
More points can be added to the polygon after this call.
"""
if self.polyline:
area = Math.NAN
if self.num < 2:
perimeter = 0.0
if not self.polyline:
area = 0.0
return self.num, perimeter, area
if self.polyline:
perimeter = self._perimetersum.Sum()
return self.num, perimeter, area
_, s12, _, _, _, _, _, _, _, S12 = self.earth._GenInverse(
self.lat1, self.lon1, self._lat0, self._lon0, self._mask
)
perimeter = self._perimetersum.Sum(s12)
tempsum = Accumulator(self._areasum)
tempsum.Add(S12)
crossings = self._crossings + PolygonArea._transit(self.lon1, self._lon0)
if crossings & 1:
tempsum.Add((1 if tempsum.Sum() < 0 else -1) * self.area0 / 2)
# area is with the clockwise sense. If !reverse convert to
# counter-clockwise convention.
if not reverse:
tempsum.Negate()
# If sign put area in (-area0/2, area0/2], else put area in [0, area0)
if sign:
if tempsum.Sum() > self.area0 / 2:
tempsum.Add(-self.area0)
elif tempsum.Sum() <= -self.area0 / 2:
tempsum.Add(self.area0)
else:
if tempsum.Sum() >= self.area0:
tempsum.Add(-self.area0)
elif tempsum.Sum() < 0:
tempsum.Add(self.area0)
area = 0.0 + tempsum.Sum()
return self.num, perimeter, area
