Create difference images that represent a visual diff of two pptx files

diff-pptx

#!/usr/bin/env bash
alias soffice=/Applications/LibreOffice.app/Contents/MacOS/soffice
shopt -s expand_aliases
soffice --headless --convert-to pdf arch1.pptx
soffice --headless --convert-to pdf arch2.pptx 
convert -density 150 arch1.pdf -quality 80 'output1.jpg'
convert -density 150 arch2.pdf -quality 80 'output2.jpg'

i=0
for files in output1-*; do
    compare -compose src output1-$i.jpg output2-$i.jpg diff-$i.jpg
    echo -n '.'
    : $((i++))
done
echo