Export folder picture from flac

export-picture.sh

#!/bin/bash

if [ $# -eq 0 ]; then
  printf "Usage: %s INDIR [...INDIRS]\n" "${0}" >&2
  exit 1
fi

# track
function get_mimetype () {
  local line
  while read -e line; do
    if [[ "${line}" =~ ^[[:space:]]*MIME[[:space:]]type:[[:space:]](.*)$ ]]; then
      echo "${BASH_REMATCH[1]}"
      return 0
    fi
  done < <(metaflac --list --block-type=PICTURE "${1}" | head)
  printf "The track '%s' haven't picture\n" "${1}" >&2
  return 1
}

# track
function get_ext () {
  local mimetype="$(get_mimetype "${1}")"
  case "${mimetype}" in
    "image/jpeg")
      echo "jpg"
      ;;
    "image/png")
      echo "png"
      ;;
    *)
      printf "Unkown mimetype '%s' of '%s'\n" \
        "${mimetype}" \
        "${1}" >&2
      return 1
      ;;
  esac
}

# track
function folder_picture () {
  local picture="$(dirname "${1}")/folder.$(get_ext "${1}")"
  printf "Extract picture from '%s' to '%s'\n" \
    "${1}" \
    "${picture}"
  metaflac --export-picture-to="${picture}" "${1}"
}

declare track
while read -e track; do
  folder_picture "${track}" &
done < <(find "${@}" -type f -name '01*.flac')
wait