使用cv2.fillConvexPoly时cv2.LINE_AA无法实现抗锯齿边缘求助

我想用cv2.fillConvexPoly绘制带抗锯齿边缘的多边形，设置了lineType=cv2.LINE_AA参数，但完全没达到预期效果。

以下是我的测试代码：

import numpy as np
import cv2
import matplotlib.pyplot as plt

plt.subplot(2, 3, 1)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 1, lineType=cv2.LINE_4)
plt.imshow(mask, cmap='gray')
plt.title('1, LINE_4')

plt.subplot(2, 3, 2)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 1, lineType=cv2.LINE_8)
plt.imshow(mask, cmap='gray')
plt.title('1, LINE_8')

plt.subplot(2, 3, 3)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 1, lineType=cv2.LINE_AA)
plt.imshow(mask, cmap='gray')
plt.title('1, LINE_AA')

plt.subplot(2, 3, 4)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 255, lineType=cv2.LINE_4)
plt.imshow(mask, cmap='gray')
plt.title('255, LINE_4')

plt.subplot(2, 3, 5)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 255, lineType=cv2.LINE_8)
plt.imshow(mask, cmap='gray')
plt.title('255, LINE_8')

plt.subplot(2, 3, 6)
mask = np.zeros((80, 50), dtype=np.float32)
polygon_arr = (np.array([[10, 16],[26, 20],[31, 50],[14, 50]])).astype(np.int32)
cv2.fillConvexPoly(mask, polygon_arr, 255, lineType=cv2.LINE_AA)
plt.imshow(mask, cmap='gray')
plt.title('255, LINE_AA')

plt.show()

测试中不管用LINE_4、LINE_8还是LINE_AA，输出结果完全一致。我还尝试把数组的dtype改成int32，问题依然存在。测试效果截图：

内容的提问来源于stack exchange，提问作者Citrus Aqua