#!/usr/bin/env bash
set -e

INPUT="$1"
OUT="${2:-output.gif}"

TMP_PALETTE="$(mktemp /tmp/palette.XXXX.png)"

ffmpeg -y -i "$INPUT" \
  -vf "fps=15,scale=900:-2:flags=lanczos,palettegen=max_colors=256:stats_mode=diff" \
  "$TMP_PALETTE"

ffmpeg -y -i "$INPUT" -i "$TMP_PALETTE" \
  -lavfi "fps=15,scale=900:-2:flags=lanczos [x]; [x][1:v] paletteuse=dither=bayer:bayer_scale=5" \
  "$OUT"

rm "$TMP_PALETTE"