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

@@ -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