  We provide a general framework for the derivation of the hydrodynamical
corrections to the QCD electromagnetic emissivities in a viscous fluid.
Assuming that the emission times are short in comparison to the fluid evolution
time, we show that the leading corrections in the fluid gradients are
controlled by the bulk and shear tensors times pertinent response functions
involving the energy-momentum tensor. In a hadronic fluid phase, we explicit
these contributions using spectral functions. Using the vector dominance
approximation, we show that the bulk viscosity correction to the photon rate is
sizable, while the shear viscosity is negligible for about all frequencies. In
the partonic phase near the transition temperature we provide an assessment of
the viscous corrections to the photon and dilepton emissions, using a
non-perturbative quark-gluon plasma with soft thermal gluonic corrections in
the form of operators of leading mass dimension. Again, the thermal bulk
viscosity corrections are found to be larger than the thermal shear viscosity
corrections at all energies for both the photon and dilepton in the partonic
phase.
