#!/bin/sh

set -eu

infile="$1"
outfile="${2:-$(basename "$infile" .pdf)_gray13.pdf}"

# https://stackoverflow.com/questions/20128656
gs \
	-sDEVICE=pdfwrite \
	-dPDFSETTINGS=/prepress \
	-sProcessColorModel=DeviceGray \
	-sColorConversionStrategy=Gray \
	-dOverrideICC \
	-dCompatibilityLevel=1.3 \
	-o "$outfile" \
	-f "$infile"