Shell script to convert 4x6 label from PDF to monochrome PNG on Mac OS

convert-label-to-mono.sh

#!/bin/sh
#
# Bash script to convert 4x6 label from PDF to a monochrome PNG on Mac OS
#
# I wrote this because I was unhappy with the print quality, printing 
# directly to a Zebra GX420d using the system print drivers (CUPS).
# In particular dithering could stop barcodes from being scanned.
#
# By scaling and converting to monochrome first, I found that the print quality
# was much better.
#
# By Nicholas Humfrey <njh.me>
# 

# Abort if anything fails
set -e

INFILE="$1"
OUTFILE="${INFILE%.pdf}-mono.png"
TMPFILE="$(mktemp -t monolabel).tiff"

if [ ! -f "$INFILE" ]; then
  echo "Input file does not exist: $INFILE"
  exit 1
fi

echo "Input File: $INFILE"
echo "Output File: $OUTFILE"


## FIXME: support landscape labels

# Use Mac OS tool to convert from PDF to a temporary TIFF file
# (Scriptable Image Processing System)
sips \
  --setProperty format tiff \
  --setProperty dpiHeight 203 \
  --setProperty dpiWidth 203 \
  --resampleWidth 812 \
  --resampleHeight 1218 \
  --padColor FFFFFF \
  --out "$TMPFILE" \
  "$INFILE"


# FIXME: detect if 'convert' or 'magick' commands are available

# Convert the TIFF to monochrome PNG
# (can't see how to do this using sips)
magick "$TMPFILE -threshold 50% -monochrome $OUTFILE"

# Delete the temporary file
rm -f "$TMPFILE"

echo "Done."