4. ImageChops blend

See: https://pillow.readthedocs.io/en/stable/reference/ImageChops.html#PIL.ImageChops.blend
See: Image.blend()

4.1. Blend

Use the ImageChops.blend(image1, image2, alpha) method to blend images using constant transparency weight. Alias for .Image.blend()
The second image, must have the same mode and size as the first image.
If alpha is 0.0, a copy of the first image is returned. If alpha is 1.0, a copy of the second image is returned. There are no restrictions on the alpha value. If necessary, the result is clipped to fit into the allowed output range.
from PIL import Image, ImageChops

with Image.open("test_images/crosses.png") as im1:
    with Image.open("test_images/circles.png") as im2:
        im_out = ImageChops.blend(im1, im2, 0.5)
        im_out.save("chops/blend.png")
../_images/compare_blend.png