put_mask.py

# /// script
# dependencies = ["Pillow"]
# ///
import argparse
from pathlib import Path

from PIL import Image

parser = argparse.ArgumentParser()
parser.add_argument("base_image", type=Path)
parser.add_argument("mask_image", type=Path)
parser.add_argument("output_image", type=Path)
args = parser.parse_args()

mask_image = Image.open(args.mask_image)
base_image = Image.open(args.base_image)

base_image.thumbnail(mask_image.size, Image.BICUBIC)

canvas_image = Image.new("RGB", mask_image.size, "white")
canvas_image.paste(
    base_image,
    (
        (mask_image.size[0] - base_image.size[0]) // 2,
        (mask_image.size[1] - base_image.size[1]) // 2,
    ),
)
canvas_image.paste(mask_image, mask=mask_image)

canvas_image.save(args.output_image)