code: function (filepath, options, callback) {
          if (typeof options === 'function') {
              callback = options;
              options = undefined;
          }
  
          options = options || '';
          var args = _.compact([filepath].concat(options.replace(/\ \ /g, ' ').split(' ')));
  
          logger.debug('cmd:', constant.PROG_OPTIPNG, args.join(' '));
  
          var proc = spawn(constant.PROG_OPTIPNG, args);
  
          proc.stdout.on('data', function (data) {
              logger.debug(data.toString());
          });
  
          proc.stderr.on('data', function (data) {
              logger.debug(data.toString());
          });
  
          proc.addListener('exit', function (e) {
              if (e) {
                  return callback(e);
              }
              callback();
          });
      }
docs: optipng
  
  @name optipng
  @memberof image
  @method
  @param {String} filepath PING file path.
  @param {String} options optipng options.
  @param {function} callback
  @example
  var filepath = './test/image/logo.png';