commit 4ae795dd555a923753aceceb15de4e882f701110
Author: Nils Freydank <nils.freydank@posteo.de>
Date:   Wed Nov 11 11:30:35 2020 +0100

    Initial commit

diff --git a/LICENSE b/LICENSE
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+++ b/LICENSE
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+Copyright 2020 Nils Freydank <holgersson@posteo.de>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/README.txt b/README.txt
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+# pdf2book
+This repo contains a small script to reorganize PDF from a normal increasing
+page numbering into a printable set of sheets which can be foled into a book.
+
+## usage
+pdf2book <input.pdf> <output.pdf>
+
+## Author and license
+The author of this script is Nils Freydank. The script is licensed as MIT.
+Details can be found inside the file LICENSE.
+
+<!--
+vim:fileencoding=utf-8:ts=4:syntax=markdown:colorcolumn=81:noexpandtab
+-->
diff --git a/pdf2book.sh b/pdf2book.sh
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+#!/bin/sh
+# Reorganize PDF for book-alike printing
+# -- w/o cover i.e. page 1 is the cover page --
+#
+# Author:    Nils Freydank <holgersson@posteo.de>
+# Copyright: 2020 by Nils Freydank
+# License:   MIT
+# Version:   2020-11-11
+# 
+# dependencies:
+# - bash
+# - coreutils (date, mkdir)
+# - groff (for empty page generation)
+# - poppler (pdfseperate, pdfunite)
+
+PATH="/bin:/usr/bin"
+
+INPUT_FILE="${1:-input.pdf}"
+OUTPUT_FILE="${2:-printable_output.pdf}"
+
+TMPDIR="tmp_$(date --utc +%s)"
+mkdir -p "${TMPDIR}"
+
+# Separate the document into single pages.
+pdfseparate "${INPUT_FILE}" "${TMPDIR}/%d.pdf"
+
+# Rearrange the pages:
+# 1. Find out the highest page number.
+# 2. If page number can't be devided by 4 (i.e. modulus operation is not zero),
+#    then align/fill with empty pages until it can.
+# 3. Create an array with old -> new mappings.
+# 4. Move the pages.
+
+# -- step 1 of 4 --
+PAGE_COUNTER="$(ls "${TMPDIR}" | wc -l)"
+
+# -- step 2 of 4 --
+while [[ $((${PAGE_COUNTER} % 4)) != 0 ]]
+do
+	# Create an new empty page.
+	echo "" | groff -T pdf > ${TMPDIR}/$((${PAGE_COUNTER} + 1)).pdf
+	# Re-scan the files.
+	PAGE_COUNTER="$(ls "${TMPDIR}" | wc -l)"
+done
+
+# -- step 3 of 4 --
+NEW_PAGE_LIST=()
+ctr_down="${PAGE_COUNTER}"
+
+# Note: Start at 1 as this is our first page.
+ctr_up=1
+while [[ ${ctr_up} -le $((${PAGE_COUNTER} / 2 )) ]]
+do
+	NEW_PAGE_LIST+=( ${ctr_down} )
+	NEW_PAGE_LIST+=( ${ctr_up} )
+	ctr_down=$((${ctr_down} - 1))
+	ctr_up=$((${ctr_up} + 1))
+	NEW_PAGE_LIST+=( ${ctr_up} )
+	NEW_PAGE_LIST+=( ${ctr_down} )
+	ctr_down=$((${ctr_down} - 1))
+	ctr_up=$((${ctr_up} + 1))
+done
+
+# -- step 4 of 4 --
+# Warning: Remember to start at zero as an array is accessed!
+for ((i=0; i < ${#NEW_PAGE_LIST[*]}; i++))
+do
+	if [[ $((i + 1)) -le 9 ]]
+	then
+		mv "${TMPDIR}/${NEW_PAGE_LIST[$i]}.pdf" "${TMPDIR}/newpage-0$((i + 1)).pdf"
+	else
+		mv "${TMPDIR}/${NEW_PAGE_LIST[$i]}.pdf" "${TMPDIR}/newpage-$((i + 1)).pdf"
+	fi
+done
+
+# Re-unite the sorted pages for printing.
+pdfunite "${TMPDIR}"/newpage-* "${OUTPUT_FILE}"
+
+# Cleanup intermediate data.
+rm -rf "${TMPDIR}"
+
+# vim:fileencoding=utf-8:ts=4:syntax=bash:colorcolumn=81:noexpandtab