def save(output_path)
      output_path = File.expand_path(output_path)

      create_epub do
        mimetype = Zip::ZipOutputStream::open(output_path) do |os|
          os.put_next_entry("mimetype", nil, nil, Zip::ZipEntry::STORED, Zlib::NO_COMPRESSION)
          os << "application/epub+zip"
        end
        zipfile = Zip::ZipFile.open(output_path)
        Dir.glob('**/*').each do |path|
          zipfile.add(path, path)
        end
        zipfile.commit
      end
      FileUtils.remove_entry_secure dir
    end
def save(output_path)
      output_path = File.expand_path(output_path)

      create_epub do
        mimetype = Zip::ZipOutputStream::open(output_path) do |os|
          os.put_next_entry("mimetype", nil, nil, Zip::ZipEntry::STORED, Zlib::NO_COMPRESSION)
          os << "application/epub+zip"
        end
        zipfile = Zip::ZipFile.open(output_path)
        Dir.glob('**/*').each do |path|
          zipfile.add(path, path)
        end
        zipfile.commit
      end
      FileUtils.remove_entry_secure dir
    end
Save as OCF

 @param [String] output_path the output file path of ePub