From 04475076070bce27b971523effdb03438d55e1c6 Mon Sep 17 00:00:00 2001
From: Alexander Kobjolke <me@failco.de>
Date: Sun, 3 Apr 2022 00:02:03 +0200
Subject: [PATCH] merge-pdf: Convert to PostScript before combining

Some PDF files may contain empty BBox elements which confuses the pdf
parser so that those files get ignored. This commit circumvents this
problem by first converting all files to PostScript.
---
 home/local/bin/merge-pdf | 70 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 68 insertions(+), 2 deletions(-)

diff --git a/home/local/bin/merge-pdf b/home/local/bin/merge-pdf
index c5b4e62..a2d0de5 100755
--- a/home/local/bin/merge-pdf
+++ b/home/local/bin/merge-pdf
@@ -1,8 +1,74 @@
 #! /usr/bin/env nix-shell
-#! nix-shell -i bash -p ghostscript
+#! nix-shell -i bash -p ghostscript -p coreutils
 #
 # Local Variables:
 # mode: sh
 # End:
+#
 
-gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=- -dBATCH "$@"
+workdir=
+keep_workdir=false
+output=-
+
+function usage {
+    cat <<EOF
+usage: merge-pdf [options] files...
+
+options:
+  -o FILE    write result to FILE (default: -)
+EOF
+}
+
+function cleanup {
+    if [ x"${keep_workdir}" != x"true" ]; then
+        if [ -d "${workdir}" ]; then
+            rm -rf "${workdir}"
+        fi
+    fi
+}
+
+trap "cleanup" EXIT
+
+while getopts ":ho:k" o; do
+   case "$o" in
+       h)
+           usage
+           exit 0
+           ;;
+       o)
+           output="$OPTARG"
+           ;;
+       k)
+           keep_workdir=true
+           ;;
+       *)
+           usage
+           exit 1
+           ;;
+   esac
+done
+
+shift $((OPTIND - 1))
+
+workdir=$(mktemp -d)
+
+echo >&2 "[INFO] Putting temporary files into ${workdir}"
+
+files=()
+for f; do
+    fname=$(basename "$f" .pdf)
+    of="${workdir}/${fname}.ps"
+    echo >&2 "[PS  ] \"${f}\" -> \"${of}\""
+    pdf2ps "$f" "${of}" >&/dev/null
+    files+=("$of")
+done
+
+echo >&2 "[PDF ] combining ${#files[@]} file(s) into ${output}"
+
+gs -dNOPAUSE -sDEVICE=pdfwrite \
+    -dPDFSETTINGS=/prepress \
+    -sPAPERSIZE=a4 \
+    -sFIXEDMEDIA \
+    -sOUTPUTFILE="${output}" \
+    -dBATCH \
+    "${files[@]}" >&/dev/null