make_grid.py

#!/usr/bin/env python3

"""Assembles images into a grid."""

import argparse
import math
import sys

from PIL import Image


def main():
    p = argparse.ArgumentParser(description=__doc__)
    p.add_argument("images", type=str, nargs="+", metavar="image", help="the input images")
    p.add_argument("--output", "-o", type=str, default="out.png", help="the output image")
    p.add_argument("--nrow", type=int, help="the number of images per row")
    args = p.parse_args()

    images = [Image.open(image) for image in args.images]
    mode = images[0].mode
    size = images[0].size
    for image, name in zip(images, args.images):
        if image.mode != mode:
            print(f"Error: Image {name} had mode {image.mode}, expected {mode}", file=sys.stderr)
            sys.exit(1)
        if image.size != size:
            print(f"Error: Image {name} had size {image.size}, expected {size}", file=sys.stderr)
            sys.exit(1)

    n = len(images)
    x = args.nrow if args.nrow else math.ceil(n**0.5)
    y = math.ceil(n / x)

    output = Image.new(mode, (size[0] * x, size[1] * y))
    for i, image in enumerate(images):
        cur_x, cur_y = i % x, i // x
        output.paste(image, (size[0] * cur_x, size[1] * cur_y))

    output.save(args.output)


if __name__ == "__main__":
    main()