  A small fraction of hot OBA stars host global magnetic fields with field
strengths of the order of 0.1-10 kG. This leads to the creation of persistent
surface structures (spots) in stars with sufficiently weak winds as a result of
the radiative diffusion. These spots become evident in spectroscopic and
photometric variability. This type of variability is not expected in stars with
strong winds, where the wind inhibits the radiative diffusion. Therefore, a
weak photometric variability of the magnetic Of?p star HD 191612 is attributed
to the light absorption in the circumstellar clouds. We study the nature of the
photometric variability of HD 191612. We assume that the variability results
from variable wind blanketing induced by surface variations of the magnetic
field tilt and modulated by stellar rotation. We used our global kinetic
equilibrium (NLTE) wind models with radiative force determined from the
radiative transfer equation in the comoving frame (CMF) to predict the stellar
emergent flux. Our models describe the stellar atmosphere in a unified manner
and account for the influence of the wind on the atmosphere. The models are
calculated for different wind mass-loss rates to mimic the effect of magnetic
field tilt on the emergent fluxes. We integrate the emergent fluxes over the
visible stellar surface for individual rotational phases, and calculate the
rotationally modulated light curve of HD 191612. The wind blanketing that
varies across surface is able to explain a part of the observed light
variability in this star. The mechanism is able to operate even at relatively
low mass-loss rates. The remaining variability is most likely caused by the
flux absorption in circumstellar clouds. The variable wind blanketing is an
additional source of the light variability in massive stars. The presence of
the rotational light variability may serve as a proxy for the magnetic field.
