Section CardFunImage.
Variables aT aT2 rT : finType.
Variables (f : aT -> rT) (g : rT -> aT) (f2 : aT -> aT2 -> rT).
Variables (D : {pred aT}) (D2 : {pred aT}).

Lemma can_imset_pre (T : finType) f g (A : {set T}) :
cancel f g -> f @: A = g @^-1: A :> {set T}.