Integrating spatial and frequency information for Under-Display Camera image restoration

Abstract Under-Display Camera (UDC) houses a digital camera lens under a display panel. However, UDC introduces complex degradations such as noise, blur, decrease in transmittance, and flare. Despite the remarkable progress, previous research on UDC mainly focuses on eliminating diffraction in the spatial domain and rarely explores its potential in the frequency domain. In this paper, we revisit the UDC degradations in the Fourier space and figure out intrinsic frequency priors that imply the presence of the flares. Based on these observations, we propose SFIM, a novel multi-level deep neural network that efficiently restores UDC-distorted images by integrating local and global (the collective contribution of all points in the image) information. SFIM uses CNNs to capture fine-grained local details and FFT-based models to extract global patterns. The network comprises a spatial domain block (SDB), a frequency domain block (FDB), and an attention-based multi-level integration block (AMIB). Specifically, SDB focuses more on detailed textures such as noise and blur, FDB emphasizes irregular texture loss in extensive areas such as flare, and AMIB employs cross-domain attention to selectively integrate complementary spatial and frequency features across multiple levels, enhancing detail recovery and mitigating irregular degradations like flare. SFIM’s superior performance over state-of-the-art approaches is demonstrated through rigorous quantitative and qualitative assessments. Our source code is publicly available at: https://github.com/mcrl/SFIM .