The&Dgr;++magnetic dipole moment is determined within a full dynamical and gauge invariant model. Using the same model the coupling constants that determine the M1 and E2 contributions to the pion photoproduction transition are also analyzed. First we study the elastic&pgr;+pand radiative&pgr;+p&ggr;scattering within a complex mass scheme which incorporates the finite width of the&Dgr;++resonance. The amplitudes for both processes are invariant under contact transformations that left invariant Lagrangians with the spin 3/2 fields and gauge-invariance is fulfilled for the radiative case. The pole parameters of the&Dgr;++obtained by fitting the experimental elastic cross section arem&Dgr;=(1211.9±0.5)&hthinsp;MeVand&Ggr;&Dgr;=(84.9±0.4)&hthinsp;MeV.The anomalous magnetic dipole moment of the&Dgr;++is left as the only adjustable parameter in radiative&pgr;+p&ggr;scattering. It was fixed by comparison with the experimental bremsstrahlung differential cross section in the case of most sensible photon geometries. In addition the coupling constants G1 and G2 of the&ggr;N→&Dgr;vertex are fitted to reproduced pion photoproduction cross section. ©2001 American Institute of Physics.