  The quantum phase-space approach allows one to define relativistic spatial
distributions inside a target with arbitrary spin and arbitrary average
momentum. We apply this quasiprobabilistic formalism to the whole
electromagnetic four-current operator in the case of spin-$0$ and
spin-$\frac{1}{2}$ targets, study in detail the frame dependence of the
corresponding spatial distributions, and compare our results with those from
the light-front formalism. While former works focused on the charge
distributions, we extend here the investigations to the current distributions.
We clarify the role played by the Wigner rotation and argue that
electromagnetic properties are most naturally understood in terms of Sachs form
factors, contrary to what the light-front formalism previously suggested.
Finally, we illustrate our results using the pion and nucleon electromagnetic
form factors extracted from experimental data.
