Dynamic WebM resolution

dynamic-webm.sh

#!/usr/bin/env bash

tmpfile=$(mktemp)

clean_up() {
    rm -f "$tmpfile"
}

trap "clean_up" EXIT
trap "clean_up; exit 1" INT TERM

input=apu.jpg

curl -LR -o $input https://0x0.st/H-fV.jpg

width=$(identify -format '%w' $input)
rm -f apu???.webm
j=0
for i in $(seq 10 1 $width); do
    j=$(($j + 1))
    h=$(printf '%03d' $j)
    convert $input -resize ${i}x${i} apu${h}.webm
done

>$tmpfile
for i in $(seq 1 $j); do
    echo "file $(pwd)/apu$(printf '%03d' $i).webm" >>$tmpfile
done
for i in $(seq $j -1 1); do
    echo "file $(pwd)/apu$(printf '%03d' $i).webm" >>$tmpfile
done
ffmpeg -hide_banner -f concat -safe 0 -i $tmpfile -c copy -y foo.webm