  The recent advancements in black hole imaging have opened a new era of
probing horizon-scale physics with electromagnetic radiation. However, a
feature of the observed images, a bright ring encircling a relatively dark
region, has not sufficiently proved the existence of event horizons. It thus
requires extreme care when studying the possibility of using such image
features to examine quantum effects that may change the classical picture of
black holes slightly or drastically. In this work, we investigate the image of
a horizonless compact object, whose interior metric satisfies the 4D
semi-classical Einstein equation non-perturbatively for the Planck constant,
and whose entropy agrees with the Bekenstein-Hawking formula. Although the
absence of an event horizon allows light rays to pass through the dense
interior, the extremely strong redshift significantly darkens the image, making
it almost identical to the classical black-hole image. In particular, if there
is light emission a bit inside the surface of the object, the intensity around
the inner shadow is slightly enhanced, which could be a future observable
prediction to characterize the object. We also find through a phenomenological
parameter that the image is further darkened due to interactions inside. Thus,
the image is consistent with current observations, and the object could be a
candidate for black holes in quantum theory.
