Python PIL（Pillow）有时会在透明图像上生成垃圾

Question

当我创建一个没有颜色的图像时，我会得到垃圾（随机颜色，点或线）

image = Image.new("RGBA", (256, 256), None)

# draw a rectangle with rounded corners
image = draw_corner_box(image, radius=10)

# draw a rectangle with rounded corners and apply blur,
# paste image in the result and return
image = draw_shadow_box(image, radius=10)

image.save("image.png", "PNG")

完整图像

缩放图像