assfontmatch.rb

# Converts full name font specification on .ass subtitle to
# PostScript name to be used with ffmpeg+coretext on macOS

# coretext can't locate "맑은 고딕" (display name / full name) specified on ass file,
# however it can locate when "MalgunGothicRegular" (postscript name) is specified.

ASS_PATH = ARGV[0]
NEWASS_PATH = ARGV[1]
FONTS_DIR = ARGV[2]

unless ASS_PATH && NEWASS_PATH && FONTS_DIR
  puts "Usage: assfontmatch.rb subtitle.ass newsubtitle.ass ./fonts"
  exit 0
end

FC_SCAN_PATH = "/opt/homebrew/Cellar/fontconfig/2.14.0/bin/fc-scan"
FC_SCAN_CMD = "#{FC_SCAN_PATH} --format=\"%{fullname}\n%{postscriptname}\""

ass = File.read(ASS_PATH)

Dir["#{FONTS_DIR}/*"].each do |font|
  full_names, postscript_name = `#{FC_SCAN_CMD} #{font}`.split("\n")

  full_names.split(",").each do |full_name|
    # Match "양재난초체M" even when "양재난초체m" is specified on ass file
    regexp = Regexp.new(Regexp.escape(full_name), Regexp::IGNORECASE)
    ass.gsub!(regexp, postscript_name)
  end
end

File.write(NEWASS_PATH, ass)