Make a montage from a list of PDF files

montage.py

#!/usr/bin/env python
"""
montage.py
2020-12-23
Kamil Slowikowski

Usage
-----

Write montage.png from a list of PDF files, each panel 500px wide:

    python montage.py -p 500 file-*.pdf montage.png


Requirements
------------

This script depends on the following command line tools:

    - GhostScript
    - pngquant
    - ImageMagick (or GraphicsMagick)

On macOS, install the dependencies like this:

    brew install gs pngquant graphicsmagick

"""

from glob import glob
from natsort import natsorted
from pathlib import Path
from shlex import quote
import click
import re
import subprocess


def optimize_png(file):
    file_fs8 = file.replace(".png", "-fs8.png")
    cmd = f'pngquant "{file}" && mv -f "{file_fs8}" "{file}"'
    print(f'Optimizing {file}')
    return subprocess.call(cmd, shell = True)


def pdf_to_png(file, res=200):
    assert Path(file).is_file()
    png = file.rstrip('.pdf') + '.png'
    if not Path(png).is_file():
        print(f'Writing {quote(png)}')
        cmd = f'gs -sDEVICE=pngalpha -o {quote(png)} -r{res} {quote(file)}'
        p = subprocess.Popen(
            cmd.split(),
            stdout = subprocess.PIPE,
            stderr = subprocess.PIPE,
        )
        output, err = p.communicate()
        assert p.returncode == 0
    return png


def get_ext(file):
   m = re.search(r"\.(.+)$", file)
   if m:
       return m.group(1)
   return None


@click.command()
@click.argument('in_files', nargs = -1)
@click.argument('out_file', nargs = 1)
@click.option('-p', '--pixels', 'pixels', default = 384,
    help = 'Width, in pixels, of each panel')
@click.option('--optimize/--no-optimize', 'optimize', default = True,
    help = 'Run pngquant to optimize the output, if it is a PNG')
def montage(in_files, out_file, pixels = 384, optimize = True):
    assert len(in_files) >= 2
    in_files = list(in_files)
    for i in range(len(in_files)):
        if get_ext(in_files[i]) == 'pdf':
            in_files[i] = pdf_to_png(in_files[i])
    cmd = f"montage {' '.join(in_files)}"
    cmd += f" -geometry {pixels}x+2+2 {out_file}"
    print(f'Writing {out_file}')
    retval = subprocess.call(cmd, shell = True)
    if optimize and get_ext(out_file) == 'png':
        retval = optimize_png(out_file)
    return retval


if __name__ == '__main__':
    montage()