cat and shrink pdf files

pdf-cat-and-shrink/assemble.sh

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+#!/bin/sh
+
+for i in {1..24..1}; do
+  qpdf --empty --pages "vivre-ensemble.pdf" $((i+1)) "langage-oral.pdf" $((i+3)) "langage-écrit.pdf" $((i+5)) "structurer-sa-pensée.pdf" $((i+3)) "découvrir-le-monde.pdf" $((i+3)) "activités-artistiques.pdf" $((i+3)) "activités-physiques.pdf" $((i+2)) -- tmp.pdf
+  ./shrinkpdf.sh tmp.pdf livret-élève-$i.pdf 150
+done

pdf-cat-and-shrink/shrinkpdf.sh

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+#!/bin/sh
+
+# http://www.alfredklomp.com/programming/shrinkpdf
+# Licensed under the 3-clause BSD license:
+#
+# Copyright (c) 2014-2019, Alfred Klomp
+# 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.
+
+
+shrink ()
+{
+	gs					\
+	  -q -dNOPAUSE -dBATCH -dSAFER		\
+	  -sDEVICE=pdfwrite			\
+	  -dCompatibilityLevel=1.3		\
+	  -dPDFSETTINGS=/screen			\
+	  -dEmbedAllFonts=true			\
+	  -dSubsetFonts=true			\
+	  -dAutoRotatePages=/None		\
+	  -dColorImageDownsampleType=/Bicubic	\
+	  -dColorImageResolution=$3		\
+	  -dGrayImageDownsampleType=/Bicubic	\
+	  -dGrayImageResolution=$3		\
+	  -dMonoImageDownsampleType=/Subsample	\
+	  -dMonoImageResolution=$3		\
+	  -sOutputFile="$2"			\
+	  "$1"
+}
+
+check_smaller ()
+{
+	# If $1 and $2 are regular files, we can compare file sizes to
+	# see if we succeeded in shrinking. If not, we copy $1 over $2:
+	if [ ! -f "$1" -o ! -f "$2" ]; then
+		return 0;
+	fi
+	ISIZE="$(echo $(wc -c "$1") | cut -f1 -d\ )"
+	OSIZE="$(echo $(wc -c "$2") | cut -f1 -d\ )"
+	if [ "$ISIZE" -lt "$OSIZE" ]; then
+		echo "Input smaller than output, doing straight copy" >&2
+		cp "$1" "$2"
+	fi
+}
+
+usage ()
+{
+	echo "Reduces PDF filesize by lossy recompressing with Ghostscript."
+	echo "Not guaranteed to succeed, but usually works."
+	echo "  Usage: $1 infile [outfile] [resolution_in_dpi]"
+}
+
+IFILE="$1"
+
+# Need an input file:
+if [ -z "$IFILE" ]; then
+	usage "$0"
+	exit 1
+fi
+
+# Output filename defaults to "-" (stdout) unless given:
+if [ ! -z "$2" ]; then
+	OFILE="$2"
+else
+	OFILE="-"
+fi
+
+# Output resolution defaults to 72 unless given:
+if [ ! -z "$3" ]; then
+	res="$3"
+else
+	res="72"
+fi
+
+shrink "$IFILE" "$OFILE" "$res" || exit $?
+
+check_smaller "$IFILE" "$OFILE"