type src
type dst
val blit : (src, dst) Base.Blit_intf.blit
val blito : (src, dst) Base.Blit_intf.blito
val unsafe_blit : (src, dst) Base.Blit_intf.blit
val sub : (src, dst) Base.Blit_intf.sub
val subo : (src, dst) Base.Blit_intf.subo