Gif gen

giffer.sh

#!/usr/bin/env nix-shell
#!nix-shell -i bash -p ffmpeg pngquant gifski gifsicle
# shellcheck shell=bash
set -euo pipefail

if [[ "$#" -ne 3 ]]; then
  echo "Usage: gif.sh <name> <scale> <fps>"
  exit 1
fi

name=$1
scale=$2
fps=$3
name_root="${name%.*}"

# https://engineering.giphy.com/how-to-make-gifs-with-ffmpeg/
#ffmpeg -i $name -filter_complex "[0:v] fps=$fps,scale=$scale:-2,split [a][b];[a] palettegen [p];[b][p] paletteuse" -y frames/frame%04d.png

mkdir frames

# https://cassidy.codes/blog/2017/04/25/ffmpeg-frames-to-gif-optimization/
ffmpeg -i $name -vf palettegen -y palette.png
ffmpeg -i $name -v warning -vf "fps=$fps,scale=$scale:-1:flags=lanczos,palettegen=stats_mode=diff" -y palette.png
ffmpeg -i $name -i palette.png -lavfi "fps=$fps,scale=$scale:-1:flags=lanczos,paletteuse=dither=bayer:bayer_scale=5:diff_mode=rectangle" -y frames/frame%04d.png

pngquant --strip --ext=.png --force frames/*.png
gifski -W $scale frames/*.png -o tmp.gif
gifsicle --colors 256 -O3 tmp.gif -o $name_root-$scale-$fps.gif

rm -rf frames palette.png tmp.gif

# https://github.com/phw/peek