code: func NewBatch(container Triangles, pic Picture) *Batch {
  	b := &Batch{cont: Drawer{Triangles: container, Picture: pic}}
  	b.SetMatrix(IM)
  	b.SetColorMask(Alpha(1))
  	return b
  }
docs: // NewBatch creates an empty Batch with the specified Picture and container.
  //
  // The container is where objects get accumulated. Batch will support precisely those Triangles
  // properties, that the supplied container supports. If you retain access to the container and
  // change it, call Dirty to notify Batch about the change.
  //
  // Note, that if the container does not support TrianglesColor, color masking will not work.