  Photon Bose-Einstein condensates are characterised by a quite weak
interaction, so they behave nearly as an ideal Bose gas. Moreover, since the
current experiments are conducted in a microcavity, the longitudinal motion is
frozen out and the photon gas represents effectively a two-dimensional trapped
gas of massive bosons. In this paper we focus on a harmonically confined ideal
Bose gas in two dimensions, where the anisotropy of the confinement allows for
a dimensional crossover. If the confinement in one direction is strong enough
so that this squeezed direction is frozen out, then only one degree of freedom
survives and the system can be considered to be quasi-one dimensional. In view
of an experimental set-up we work out analytically the thermodynamic properties
for such a system with a finite number of photons. In particular, we focus on
examining the dimensional information which is contained in the respective
thermodynamic quantities.
