Image generation with DOL-systems is discussed. It is shown that, if e
ither the vector or the turtle geometry interpretation is used, DOL-sy
stems can produce step-by-step all images that can be generated by reg
ular languages (or by equivalent Iterative Matrix Homomorphisms of Sha
llit and Stolfi). An extension of turtle geometry interpretation is in
troduced that enables L-systems to generate gray-tone images. It is sh
own that with our extension every Weighted Finite Automaton can be sim
ulated step-by-step by a DOL-system.