Github action to compare compiled examples with known good versions

[matsavage]

There should be a way to automatically check that there has been no visual change in the PDFs produced by the actions pipeline

[matsavage]

Example script using imagemagick

#!/bin/bash

reference_files=`find /home/mathew-savage/Downloads/example_2_*`

# run imagemagick compare for all files
results=()
for file in $reference_files
do
  filename=`basename $file`
  result=`compare -metric mae /home/mathew-savage/Downloads/${filename} /home/mathew-savage/Downloads/result/${filename} difference_${filename}.png 2>&1`

  similarity=`echo $result | grep -oP '(?<=\().+?(?=\))'`
  similarity_percent="$(echo "$similarity * 100" | bc)"
  results+=($similarity_percent)

  printf "%s: difference from reference: %0.4f%% \n" $file $similarity_percent
done

# return 1 if any file is over threshold
for result in ${results[@]}
do
  if (( $(echo "$result > 0.01" | bc -l) )); then
    exit 1
  fi
done

exit 0