Decolumnize PDFs for ebook readers

pdfdecol.sh

#!/bin/bash
# -*- mode: shell-script; indent-tabs-mode: t; tab-width: 4; -*-
set -euo pipefail
IFS=$'\n'


function help {
	cat <<-EOF
		Usage: $0 <input.pdf> <output-file-or-directory>

		Cut file horizontally, then vertically, then crop margins.
		Make it readable on a 6" ebook reader.
	EOF
}


# decol <input.pdf> <output.pdf>
function decol {
	input="$1"
	output="$2"

	if [[ -e "$output" ]]; then
		read -rp "File '$output' exists. Overwrite? (y/n) "
		if [[ "${REPLY::1}" != "y" ]]; then
			exit
		fi
	fi

	tempx=$(tempfile --suffix=.pdf)
	tempy=$(tempfile --suffix=.pdf)
	trap "rm $tempx $tempy" EXIT

	mutool poster -x2 "$input" "$tempx"
	mutool poster -y2 "$tempx" "$tempy"
	pdfcrop "$tempy" "$output"
}


if [[ "$1" = "--help" || "$#" -ne 2 ]]; then
	help
	exit
fi

if [[ -d "$2" ]]; then
	decol "$1" "$2/$(basename $1)"
else
	decol "$1" "$2"
fi