pdfunbindbook.sh - unbind a book that all pages are double-page except covers.

pdfunbind.sh

#!/usr/bin/env bash
#
# pdfunbind.sh - unbind double-page PDF.
# Copyright (c) 2018 Koichi OKADA. All rights reserved.
# This script is distributed under the MIT license.
#
# Reference:
# * [1] superuser / [Linux-based tool to chop PDFs into multiple pages [closed]](https://superuser.com/questions/191373/linux-based-tool-to-chop-pdfs-into-multiple-pages)

(( 5 <= DEBUG )) && set -x

function cleanup ()
{
  rm "$WORK"*.pdf 2>/dev/null
  trap 0 1 2 3 15
}

function pagesize ()
{
  pdfinfo "$1" | awk '/^Page size:/ {print $3,$5}'
}

function usage ()
{
  cat <<-EOD
	Usage: ${0##*/} [options] PDFFILE
	  Unbind double-page PDF.
	  Output file is \${PDFFILE%.*}_unbound.pdf
	Options:
	  -m,--mode={book|2up}
	    Select mode (default: $OPT_MODE_DEFAULT).
	      book : All pages are double-page except covers.
	      2up  : All pages are double-page.
	EOD
}

OPT_MODE_DEFAULT=book

while (( 0 < $# )); do
  case "$1" in
    -h|--help)
        OPT_HELP="$1"
        shift
        ;;
    -m*|--mode|--mode=*)
        if [[ "$1" =~ ^(-m|--mode=)(book|2up)$ ]]; then
        OPT_MODE="${BASH_REMATCH[1]}"
        shift
        elif [[ "$1 $2" =~ ^(-m |--mode )(book|2up)$ ]]; then
        OPT_MODE="$2"
        shift 2
        else
        echo "Error: invalid option: $1 $2"
        exit 1
        fi
        ;;
    -*)
        echo "Error: unknown option: $1"
        exit 1
        ;;
    *)
        ARGS+=( "$1" )
        shift
        ;;
  esac
done

set -- "${ARGS[@]}"

if (( $# <= 0 )) || [ -n "$OPT_HELP" ]; then
  usage
  exit
fi

EL="\e[K"
PAGES=$(pdfinfo "$1" | awk '/^Pages:/{print $2}')
WORK="$(type pdftk | grep -q snap && mktemp -up. || mktemp -u)"
: ${OPT_MODE:=$OPT_MODE_DEFAULT}
case "$OPT_MODE" in
  2up)  COVER=0;;
  book) COVER=1;;
esac

trap cleanup 0 1 2 3 15

for i in `seq 1 $PAGES`; do
  echo -en "\rSplitting: page $i"
  pdftk "$1" cat $i output "$WORK"$(printf %03d $i).pdf
done
echo -e "\r${EL}Splitting: done"

for i in `seq $(( 1 + COVER )) $(( PAGES - COVER ))`; do
  echo -en "\rUnbinding book: page $i"

  PAGESIZE=( $( pagesize "$WORK"$(printf %03d $i).pdf ) )
  W="${PAGESIZE[0]}"
  H="${PAGESIZE[1]}"
  
  #BEGIN from reference [1]
  Wh="$( echo "$W * 0.5" | bc -l | cut -d . -f1 )"
  Whtt="$( echo "$W * 5" | bc -l | cut -d . -f1 )"
  Htt="$( echo "$H * 10" | bc -l | cut -d . -f1 )"
  
  gs -q -o "$WORK"$(printf %03d $i)L.pdf -sDEVICE=pdfwrite -g"$Whtt"x"$Htt" -c "<</PageOffset [0 0]>> setpagedevice" -f "$WORK"$(printf %03d $i).pdf
  gs -q -o "$WORK"$(printf %03d $i)R.pdf -sDEVICE=pdfwrite -g"$Whtt"x"$Htt" -c "<</PageOffset [-$Wh 0]>> setpagedevice" -f "$WORK"$(printf %03d $i).pdf
  #END from reference [1]
  
  rm "$WORK"$(printf %03d $i).pdf
done
echo -e "\r${EL}Unbinding book: done"

echo -en "\rMerging: "
pdftk "$WORK"*.pdf cat output "${1%.*}_unbound.pdf"
echo "done"