mkv-extract-fonts

#!/bin/bash
set -eo pipefail
shopt -s nullglob

throw() {
  printf '%s: %s\n' "${0##*/}" "$1" >&2
  return 1
}

if [[ $1 =~ ^(--help|-h)$ ]]; then
  cat >&2 <<'EOF'
Usage: mkv-extract-fonts [-n] [<path...>]

Extracts all unique fonts (by filename) from the given mkvs. Fonts are
extracted to the current directory.

Directories are expanded to contained *.mkv files (non-recursive). If no paths
are given, the current directory is used.

Options:

  -n        Dry run.
EOF
  exit 1
fi

paths=()
paths_given=
dry_run=
while (( $# > 0 )); do
  case $1 in
    --)
      shift
      paths+=("$@")
      break
      ;;
    -n)
      dry_run=1
      ;;
    -*)
      throw "unknown option: $1"
      ;;
    *)
      if [[ -f "$1" ]]; then
        paths+=("$1")
        paths_given=1
      elif [[ -d "$1" ]]; then
        paths+=("$1"/*.mkv)
        paths_given=1
      else
        throw "'$1' does not exist"
      fi
      ;;
  esac
  shift
done
if [[ ! $paths_given ]]; then
  paths=(*.mkv)
fi

list_fonts() { # <path>
  mkvmerge -J "$1" | jq -r '
    if .tracks | type != "array" then
      "\"\(.file_name)\" is not an mkv\n" | halt_error
    else
      .attachments[] | select(
        (.content_type | startswith("font/")) or
        .content_type == "application/x-truetype-font" or
        .content_type == "application/x-font-ttf" or
        .content_type == "application/vnd.ms-opentype" or
        .content_type == "application/font-sfnt" or
        .content_type == "application/font-woff" or
        (.file_name | test("\\.(ttf|otf|ttc|woff2?)$"; "i"))
      ) | (
        (.id | tostring) + ":" + .file_name
      )
    end
  '
}

for path in "${paths[@]}"; do
  echo "$path"

  fonts=()
  has_fonts=

  list=$(list_fonts "$path")

  while read -r line; do
    has_fonts=1
    filename=$(cut -f2 -d: <<<"$line")
    if [[ -f $filename ]]; then
      printf '  \e[36mAlready extracted\e[m %s\n' "$filename"
    else
      printf '  \e[32mExtracting\e[m %s\n' "$filename"
      fonts+=("$line")
    fi
  done <<<"$list"

  if [[ ! $has_fonts ]]; then
    printf '  No fonts\n'
    continue
  elif (( ${#fonts[@]} == 0 )) || [[ $dry_run ]]; then
    continue
  fi

  mkvextract "$path" attachments "${fonts[@]}" >/dev/null
done