  We calculate the thermal photon transverse momentum spectra and elliptic flow
in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at RHIC and in $\sqrt{s_{NN}} =
2.76$ TeV Pb+Pb collisions at the LHC, using an ideal-hydrodynamical framework
which is constrained by the measured hadron spectra at RHIC and LHC. The
sensitivity of the results to the QCD-matter equation of state and to the
photon emission rates is studied, and the photon $v_2$ is discussed in the
light of the photonic $p_T$ spectrum measured by the PHENIX Collaboration. In
particular, we make a prediction for the thermal photon $p_T$ spectra and
elliptic flow for the current LHC Pb+Pb collisions.
