Yunyang Xu, Lexin Fang, Xuemei Li, Caiming Zhang
Image super-resolution aims to enhance the detail representation and visual clarity of low-resolution images. Although latent diffusion model (LDM)-based super-resolution approaches have achieved remarkable progress, their use of aggressive downsampling to compress degraded images into the latent space often results in loss of high-frequency details, thereby limiting the structural fidelity of the reconstructed images. To address this, we propose a plug-and-play Edge Reconstruction Network (ERN) that recovers high-resolution edge prior from low-resolution inputs. By explicitly including this high-resolution edge prior as structural priors in the diffusion process, the model’s ability to reconstruct high-frequency details can be greatly improved. In ERN, new edges of images are calculated using edge pixels. Since edge pixels are treated as discrete sampling points on the edge curve, the neural network interpolates edge pixels only, effectively eliminating non-edge information interference, thereby reducing jagged edges and block artifacts. In addition, the network’s reconstruction accuracy and robustness in complex structure scenes improve significantly as it learns the mapping between low-resolution images and their corresponding high-resolution edge images. Another key contribution is an automatic label generation method based on surface fitting, which extracts edge labels with quadratic polynomial accuracy from GT images, providing reliable supervision for edge reconstruction and alleviating the scarcity of high-quality edge labels. Extensive experiments demonstrate ERN’s effectiveness on SR task. It can be seamlessly integrated into existing LDM-based methods, with only ∼ 15M additional parameters yielding a 0.1 dB ∼ 1.2 dB PSNR gain, achieving a favorable balance between performance and computational cost. The code will be released at https://github.com/YunyangXu/ERN .