class DecoratedPolygon:
def __init__(self, vlist):
corrected_vlist = self.__correct(vlist)
self.polygon = Polygon(corrected_vlist)
@property
def vlist(self):
return self.polygon.vlist
def area(self):
return self.polygon.area()
def set_areaAlg(self, alg):
self.polygon.set_areaAlg(alg)
def __correct(self, vlist):
new_vlist = vlist
if new_vlist[-1] != new_vlist[0]:
new_vlist.append(new_vlist[0])
return new_vlist
vertices = self._polygon.vlist
area = 0.0
for i in range(0, len(vertices) - 3):
area += self.__calc_triang_area(vertices[i], vertices[i + 1],
vertices[i + 2])
return fabs(area)
def __calc_triang_area(self, v1, v2, v3):
l1 = (v2[0] - v1[0], v2[1] - v1[1])
l2 = (v3[0] - v1[0], v3[1] - v1[1])
cross = (0, 0, l1[0] * l2[1] - l1[1] * l2[0])
area = sqrt(cross[0]**2 + cross[1]**2 + cross[2]**2) / 2
return area
if __name__ == "__main__":
# Making us some pretty triangle
poly = Polygon([(0, 0), (0.866, 0.5), (1, 0)])
# Wanna know its area. Bridge will call specific area function
poly.set_areaAlg(OnlyTriangleAreaAlg(poly))
print(poly.area())
# Now it's some messed up non-convex polygon. Ouch
poly = Polygon([(0, 0), (1, 0), (2, 1), (3, 4), (3, 5), (2, 2), (1, 2),
(0, 0)])
# Need new algorithm for that
poly.set_areaAlg(GeneralAreaAlg(poly))
print(poly.area())
