vid2gif.sh - uses ffmpeg and gifsicle to convert a video to a gif within a filesize constraint

vid2gif.sh

#!/bin/bash
echo "Usage: vid2gif.sh <input> <output>"
echo -n "Enter desired delay (1/100 of seconds): "
read delay
fps=$(expr 100 / $delay)
read -p "Enter width [default: -1]: " width
width=${width:--1}
read -p "Enter height [default: -1]: " height
height=${height:--1}
read -p "Enter start timestamp [default: 0]: " tstart
tstart=${tstart:-0}
read -p "Enter duration [default: 9999999]: " dur
dur=${dur:-9999999}
read -p "Enter extra ffmpeg filters (put a comma first): " ffextra
read -p "Enter maximum filesize (bytes) [default: 3145728]: " maxbytes
maxbytes=${maxbytes:-3145728}

tempdir=$(mktemp -d)

filters="fps=$fps,scale=$width:$height:flags=lanczos$ffextra"
ffmpeg -v warning -ss $tstart -t $dur -i "$1" -vf "$filters,palettegen" -y $tempdir/palette.png
ffmpeg -v warning -ss $tstart -t $dur -i "$1" -i $tempdir/palette.png -lavfi "$filters [x]; [x][1:v] paletteuse=dither=floyd_steinberg" -y $tempdir/gif.gif


rm "$2"
gifsicle -O3 -j7 -d $delay -o "$2" $tempdir/gif.gif
lossy=0
#increment loss until filesize target is reached. 
while [ $(stat -c%s "$2") -gt $maxbytes ] && [ $lossy -lt 200 ]; do
	echo "Lossy setting $lossy didn't work (filesize = $(bc <<< 'scale=6; '$(stat -c%s "$2")'/1048576') MiB), tring $(($lossy + 5))"
	lossy=$(($lossy + 5))
	rm "$2"
	gifsicle -O3 -j7 --lossy=$lossy -d $delay -o "$2" $tempdir/gif.gif
done

rm -r $tempdir

echo -----------
if [ $lossy -gt 0 ]; then
	echo "Done! Used lossy setting $lossy, filesize = $(bc <<< 'scale=6; '$(stat -c%s "$2")'/1048576') MiB"
else
	echo "Done! Didn't need lossy compression, filesize = $(bc <<< 'scale=6; '$(stat -c%s "$2")'/1048576') MiB"
fi