gfv

#!/bin/bash

readonly program="$(basename "${0}")"
readonly cap_fps='30'

function depends_on {
  local dep="${1}"

  if ! command -v "${dep}" &>/dev/null; then
    echo -e >&2 "\n$(tput setaf 1)This script requires ${dep}. Please install it first.$(tput sgr0)\n"
    exit 1
  fi
}

function syntax_error {
  echo -e "${program}: ${1}\nTry \`${program} --help\` for more information." >&2
  exit 1
}

function get_output_path {
  readonly local ext='gif'
  readonly local input_path="${1}"
  local output_path="${2}"

  if [[ -n "${output_path}" ]]; then
    [[ "${output_path##*.}" == "${ext}" ]] && echo "${output_path}" || echo "${output_path}.${ext}"
  else
    output_path="${input_path%.*}.${ext}"

    while [[ -e "${output_path}" ]]; do
      output_path="${output_path%.*}_$(date -u +'%Y.%m.%d.%H%M%S').${ext}"
    done

    echo "${output_path}"
  fi
}

function usage {
  echo "
    Usage:
      ${program} [options] <file>

    Options:
      -f <integer>, --fps <integer>          Frames per second. Default is auto-detected from video, capped at ${cap_fps}.
      -w <interger>, --width <integer>       Resize the gif proportionally.
      -o, --output-file <file>               File to output to. Default is saving next to the input file with same name.
      -g, --gifski                           Use gifski for the conversion.
      -h, --help                             Show this help.
  " | sed -E 's/^ {4}//'
}

# available flags
args=()
while [[ "${1}" ]]; do
  case "${1}" in
    -h | --help)
      usage
      exit 0
      ;;
    -f | --fps)
      readonly chosen_fps="${2}"
      shift
      ;;
    -w | --width)
      readonly width="${2}"
      shift
      ;;
    -o | --output-file)
      readonly given_output_path="${2}"
      shift
      ;;
    -g | --gifski)
      depends_on 'gifski'
      readonly use_gifski='true'
      ;;
    --)
      shift
      args+=("${@}")
      break
      ;;
    -*)
      syntax_error "unrecognized option: ${1}"
      ;;
    *)
      args+=("${1}")
      ;;
  esac
  shift
done
set -- "${args[@]}"

if [[ "${#}" -eq 0 ]]; then
  usage
  exit 1
fi

readonly input_file="${1}"
readonly output_file="$(get_output_path "${input_file}" "${given_output_path}")"

depends_on 'ffmpeg'

# Set FPS
if [[ -z "${chosen_fps}" ]]; then
  depends_on 'ffprobe'

  readonly video_fps="$(ffprobe -loglevel error -select_streams v:0 -of default=noprint_wrappers=1:nokey=1 -show_entries stream=r_frame_rate "${input_file}" | bc)"
  readonly fps="$([[ "${video_fps}" -gt "${cap_fps}" ]] && echo "${cap_fps}" || echo "${video_fps}")"
else
  readonly fps="${chosen_fps}"
fi

# Make the animated gif
if [[ -z "${use_gifski}" ]]; then
  [[ -z "${width}" ]] && width='-1' # Make width same as original video, if none given

  readonly palette="$(mktemp).png"
  ffmpeg -i "${input_file}" -filter_complex "fps=${fps},scale=${width}:-1:flags=lanczos,palettegen" "${palette}"
  ffmpeg -i "${input_file}" -i "${palette}" -filter_complex "fps=${fps},scale=${width}:-1:flags=lanczos[x];[x][1:v]paletteuse" "${output_file}"
else
  readonly tmp_dir="$(mktemp -d)"

  echo 'Extracting images from video…'
  ffmpeg -loglevel quiet -i "${input_file}" -filter_complex "fps=${fps}" "${tmp_dir}/output_mage%9d.png"

  options=()
  [[ -n "${width}" ]] && options+=('--width' "${width}")
  options+=('--fps' "${fps}")

  gifski "${tmp_dir}/"* "${options[@]}" --output "${output_file}"
fi