docs: function bfs(img, startCoord, eventMap, blacklist) {
      var queue = _is('Array', startCoord) ? startCoord : [startCoord];
  
      if (_isImgLoaded(img)) {
          _bfs(_wrapByCanvas(img), queue, eventMap, blacklist);
      } else {
          img.addEventListener('load', function() {
              _bfs(_wrapByCanvas(img), queue, eventMap, blacklist);
          }, false);
      }
  }