  Deep neural networks have achieved remarkable progress in enhancing low-light
images by improving their brightness and eliminating noise. However, most
existing methods construct end-to-end mapping networks heuristically,
neglecting the intrinsic prior of image enhancement task and lacking
transparency and interpretability. Although some unfolding solutions have been
proposed to relieve these issues, they rely on proximal operator networks that
deliver ambiguous and implicit priors. In this work, we propose a paradigm for
low-light image enhancement that explores the potential of customized learnable
priors to improve the transparency of the deep unfolding paradigm. Motivated by
the powerful feature representation capability of Masked Autoencoder (MAE), we
customize MAE-based illumination and noise priors and redevelop them from two
perspectives: 1) \textbf{structure flow}: we train the MAE from a normal-light
image to its illumination properties and then embed it into the proximal
operator design of the unfolding architecture; and m2) \textbf{optimization
flow}: we train MAE from a normal-light image to its gradient representation
and then employ it as a regularization term to constrain noise in the model
output. These designs improve the interpretability and representation
capability of the model.Extensive experiments on multiple low-light image
enhancement datasets demonstrate the superiority of our proposed paradigm over
state-of-the-art methods. Code is available at
https://github.com/zheng980629/CUE.
