  We suggest a scheme to manipulate paraxial diffraction by utilizing the
dependency of a four-wave mixing process on the relative angle between the
light fields. A microscopic model for four-wave mixing in a Lambda-type level
structure is introduced and compared to recent experimental data. We show that
images with feature size as low as 10 micrometers can propagate with very
little or even negative diffraction. The mechanism is completely different from
that conserving the shape of spatial solitons in nonlinear media, as here
diffraction is suppressed for arbitrary spatial profiles. At the same time, the
gain inherent to the nonlinear process prevents loss and allows for operating
at high optical depths. Our scheme does not rely on atomic motion and is thus
applicable to both gaseous and solid media.
