  The photon transverse momentum spectrum and its anisotropy from Pb+Pb
collisions at the CERN Large Hadron Collider energy $\sqrt {s_{NN}}=2.76$ TeV
are investigated within the integrated hydrokinetic model (iHKM). Photon
production is accumulated from the different processes at the various stages of
relativistic heavy ion collisions: from the primary hard photons of very early
stage of parton collisions to the thermal photons from equilibrated quark-gluon
and hadron gas stages. Along the way a hadronic medium evolution is treated in
two distinct, in a sense opposite, approaches: chemically equilibrated and
chemically frozen system expansion. Studying the centrality dependence of the
results obtained allows us to conclude that a relatively strong transverse
momentum anisotropy of thermal radiation is suppressed by prompt photon
emission which is an isotropic. We find out that this effect is getting
stronger as centrality increases because of the simultaneous increase in the
relative contribution of prompt photons in the soft part of the spectra. The
substantial results obtained in iHKM with nonzero viscosity ($\eta/s=0.08$) for
photon spectra and $v_2$ coefficients are mostly within the error bars of
experimental data, but there is some systematic underestimation of both
observables for the near central events. We claim that a situation could be
significantly improved if an additional photon radiation that accompanies the
presence of a deconfined environment is included. Since a matter of a
space-time layer where hadronization takes place is actively involved in
anisotropic transverse flow, both positive contributions to the spectra and
$v_2$ are considerable, albeit such an argument needs further research and
elaboration.
