python: how to polygon to binary mask with ones in intersection area

Question

Can not make binary mask from self-intersected polygon.

import numpy as np
from PIL import Image, ImageDraw


def show(img,full=False):
    if full:
        display(Image.fromarray(np.uint8(img)))
    else:
        img = resize(img,300)
        display(img)

def polygons_to_mask(poly,shape):

    def points_to_float(point_str):
        a= point_str.split(",")
        # print(a)
        return (int(float(a[0])),int(float(a[1])))

    points = [ points_to_float(x) for x in poly.split(";")]
    points1d = []
    for p in points:
        points1d +=p 
    img = Image.new("L", [shape[0], shape[1]], 0)
    ImageDraw.Draw(img).polygon(points1d, outline=1, fill=1)
    mask = np.array(img)
    return mask


def points_to_float(point_str):
        a= point_str.split(",")
        # print(a)
        return (int(float(a[0])),int(float(a[1])))


poly = "30,20;30,60;60,60;60,30;20,30;20,40;50,40;50,50;40,50;40,20"

mask = polygons_to_mask(poly,(80,80))



# print(mask)
show(mask*255)

current result mask is: https://i.stack.imgur.com/LalaF.png

but I need like that: https://i.stack.imgur.com/XeHQP.png

tried PIL draw polygon and this polygon2mask . the result is the same.