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 can2_imset_pre : cancel f g -> cancel g f -> f @: D = g @^-1: D.