[MacOS] Reduce the size of PowerPoint (*.pptx) files by converting internal images from TIFF to PNG, saving 30x in file size

convert_image_in_ppt.sh

#!/bin/bash

input_file=$1;

if unzip -l "${input_file}" | grep ".tiff"
	then 
		echo "tiffs found, converting..."
		unzip -q "${input_file}" -d test
		for i in test/ppt/media/*.tiff; do sips -s format png "${i}" --out "${i%tiff}png"; rm $i; done
		for i in test/ppt/slides/_rels/*.rels; do echo $i; sed -i -e 's/.tiff/.png/g' $i; done
		rm test/ppt/slides/_rels/*.rels-e;
		cd test/;
		zip -q -r -X ../tmp.pptx *
		cd ..;
		rm -r test;
		mv tmp.pptx "${input_file}";
		echo "converted tiffs in ${input_file}."
	else 
		echo "no tiffs found in file"
fi