fps=60000/1001

ffmpeg \
    -r $fps -i "$1.%01d.png" \
    -vf palettegen \
    -y "$1.palette.png" \
&& \
ffmpeg \
    -r $fps -i "$1.%01d.png" \
    -i "$1.palette.png" \
    -lavfi "paletteuse[1],[1]scale=w=640:h=384:sws_flags=neighbor" \
    -y "$1.gif"