convert a video into a GIF with optimal palette

mkgif.sh

#!/usr/bin/bash

input=/dev/stdin
output=/dev/stdout
slice=
palette="/tmp/mkgif-$$-palette.png"
fps=15
width=
crop=

while getopts "s:d:t:w:f:c:h" opt; do
	case $opt in
		h)
			echo "Usage: mkgif.sh [-s start_time] [-d duration] [-t tempfile] [-w width] [-f fps] [-c width:height:x:y] [input.mp4] [output.gif]"
			exit
			;;
		s)
			slice="$slice -ss $OPTARG"
			;;
		d)
			slice="$slice -t $OPTARG"
			;;
		t)
			palette=$OPTARG
			;;
		f)
			fps=$OPTARG
			;;
		w)
			width=$OPTARG
			;;
		c)
			crop=$OPTARG
			;;
		\?)
			echo "Invalid option: -$OPTARG" >&2
			exit 1
			;;
		:)
			echo "Option -$OPTARG requires an argument." >&2
			exit 1
			;;
	esac
done

if [[ $OPTIND -le $# ]]; then
	input=${@:$OPTIND:1}
	OPTIND=$((OPTIND+1))
fi

if [[ $OPTIND -le $# ]]; then
	output=${@:$OPTIND:1}
fi

filters="fps=$fps"

if [[ ! -z $width ]]; then
	filters="$filters,scale=${width}:-1:flags=lanczos"
fi

if [[ ! -z $crop ]]; then
	filters="crop=$crop,$filters"
fi

set -xe

ffmpeg -v warning $slice -i "$input" -vf "$filters,palettegen" -y "$palette"
ffmpeg -v warning $slice -i "$input" -i "$palette" -lavfi "$filters [x]; [x][1:v] paletteuse" -f gif -y "$output"
rm "$palette"