Gifski: Optimized GIF Encoder(github.com)

    #!/bin/sh

    SCALE=500
    FPS=15
    SCALEPROVIDED=false
    
    for arg in "$@"
    do
        case $arg in
            -s=*|--size=*)
            SCALE="${arg#*=}"
            SCALEPROVIDED=true
            shift 
            ;;
            -f=*|--fps=*)
            FPS="${arg#*=}"
            shift 
            ;;
        esac
    done
    
    palette="/tmp/palette.png"

    # Look at the width/height of the video
    width=`ffprobe -v error -select_streams v:0 -show_entries stream=width -of csv=s=x:p=0 $1`
    height=`ffprobe -v error -select_streams v:0 -show_entries stream=height -of csv=s=x:p=0 $1`
    
    # Get the max
    max=$(( width > height ? width : height))
    
    # If we havent provided a scale, and the max size is lower than the default, set it to the lower value
    if [ "$SCALEPROVIDED" == true ]
    then
        minScale=$SCALE
    else
        minScale=$(( SCALE < max ? SCALE : max))
    fi
    
    # Set our flags
    filters="fps=$FPS,scale=$minScale:-1:flags=lanczos"
    
    # If there's no name provided, output the same name as the input with gif as the extension
    output=$2
    if [ -z "$output" ]
    then
        output=${1%.*}.gif
    fi
    
    # Output our gif
    ffmpeg -v error -i $1 -vf "$filters,palettegen=max_colors=256" -y $palette
    ffmpeg -v error -i $1 -i $palette -lavfi "$filters [x]; [x][1:v] paletteuse" -y $output
    
    echo created $output at ${minScale}px

    gif input.mov

    gif -s=800 -f=22 input.mov my-800px-22fps-gif.gif

  #!/usr/bin/env bash
  set -euo pipefail
  
  dbg() { if [ "${DEBUG:=false}" = 'true' ]; then echo "$@"; fi }
  die() { echo "Error: $*" 1>&2; zenity --error --text="$*"; exit 1; }
  
  if ! command -v pngquant > /dev/null; then die 'You must install pngquant'; fi
  if ! command -v cjpegli > /dev/null; then die 'You must install cjpegli'; fi
  if ! command -v gifsicle > /dev/null; then die 'You must install gifsicle'; fi
  
  for filename in "${@:1}"; do
    if [ -d "$filename" ]; then
      echo && echo "ℹ File '$filename' is a directory. Skipping."
      continue
    fi
    if [ ! -f "$filename" ]; then
      echo && echo "ℹ File '$filename' does not exist. Skipping."
      continue
    fi
  
    extension_raw="${filename##*.}"
    extension="${extension_raw,,}"  # Convert to lowercase
    if [[ "$extension" != 'jpg' && "$extension" != 'png' && "$extension" != 'gif' ]]; then
      echo && echo "ℹ Skipping file $filename due to unsupported extension: .$extension"
      continue
    fi
  
    filename_noext="${filename%.*}"
    filename_original="${filename_noext}_beforeOpt.${extension_raw}"
    filename_final="${filename_noext}.${extension}"
    dbg "filename($filename), filename_noext($filename_noext), extension($extension), filename_original($filename_original)"
  
    echo && echo " Compressing $filename ..."
    mv "$filename" "$filename_original"
    if [ "$extension" == 'jpg' ]; then
      cjpegli "$filename_original" "${filename_noext}_q50.${extension}" -q 50
      cjpegli "$filename_original" "${filename_noext}_q60.${extension}" -q 60
      cjpegli "$filename_original" "${filename_noext}_q70.${extension}" -q 70
      cjpegli "$filename_original" "${filename_noext}_q80.${extension}" -q 80
      cjpegli "$filename_original" "${filename_noext}_q90.${extension}" -q 90
    elif [ "$extension" == 'png' ]; then
      pngquant --strip --force --verbose --output "$filename_final" "$filename_original"
    elif [ "$extension" == 'gif' ]; then
      # https://kornel.ski/lossygif , set --lossy to 20 for light compression, 200 for heavy
      gifsicle -O3 --lossy=50 --verbose --output "$filename_final" "$filename_original"
    fi
    gio trash "$filename_original"
  done
  
  sync