ShrinkPDF (two step)

zpf.sh

#!/bin/sh
# Modified from https://github.com/aklomp/shrinkpdf
# Licensed under the 3-clause BSD license:
#
# Copyright (c) 2014-2022, Alfred Klomp
# Copyright (c) 2020-2022, Carlos E.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
# 1. Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
# 3. Neither the name of the copyright holder nor the names of its contributors
#    may be used to endorse or promote products derived from this software
#    without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

set -e

cleanup() {
	if [ -e "$OVERLAY" ]; then rm "$OVERLAY"; fi
	if [ -e "$BACK" ]; then rm "$BACK"; fi
}

# Temporary files
OVERLAY="$(mktemp -t zpdf.XXXXXXXXXX)"
BACK="$(mktemp -t zpdf.XXXXXXXXXX)"

trap cleanup INT HUP TERM EXIT

# Output DPI
DPI=${3:-72}

INPUT=${1:?No input file.}
if [ -f "$INPUT" ]; then
	echo "Input file: $INPUT"
else
	>&2 printf 'No such file or directory: %s\n' "${INPUT}"
	exit 1
fi

OUT=${2:?No output file.}
printf 'Output file: %s\n' "$OUT"

# Wrapper with all relvant Ghostscript options.
gs_o() {
	gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite \
		-dAutoRotatePages=/None \
		-dColorImageDownsampleType=/Bicubic \
		-dColorImageResolution="$DPI" \
		-dGrayImageDownsampleType=/Bicubic \
		-dGrayImageResolution="$DPI" \
		-dMonoImageDownsampleType=/Subsample \
		-dMonoImageResolution="$DPI" "$@"
}

printf %s 'Extracting text and images... '
	# Text
	gs_o -o "$OVERLAY" -dFILTERIMAGE -dFILTERVECTOR "$INPUT" &
	# Images
	gs_o -o "$BACK" -dFILTERTEXT -dPDFSETTINGS=/screen "$INPUT"
	wait
echo '[OK]'

printf %s 'Overlaying... '
	pdftk "$OVERLAY" multibackground "$BACK" output "$OUT"
echo '[OK]'