State Space Models (SSM), such as Mamba, have shown strong representation ability in modeling long-range dependency with linear complexity, achieving successful applications from high-level to low-level vision tasks. However, SSM's sequential nature necessitates multiple scans in different directions to compensate for the loss of spatial dependency when unfolding the image into a 1D sequence. This multi-direction scanning strategy significantly increases the computation overhead and is unbearable for high-resolution image processing. To address this problem, we propose a novel Hierarchical Mamba network, namely, Hi-Mamba, for image super-resolution (SR). Hi-Mamba consists of two key designs: (1) The Hierarchical Mamba Block (HMB) assembled by a Local SSM (L-SSM) and a Region SSM (R-SSM) both with the single-direction scanning, aggregates multi-scale representations to enhance the context modeling ability. (2) The Direction Alternation Hierarchical Mamba Group (DA-HMG) allocates the isomeric single-direction scanning into cascading HMBs to enrich the spatial relationship modeling. Extensive experiments demonstrate the superiority of Hi-Mamba across five benchmark datasets for efficient SR. For example, Hi-Mamba achieves a significant PSNR improvement of 0.29 dB on Manga109 for ×3 SR, compared to the strong lightweight MambaIR.
@article{arxiv.2410.10140,
title = {Hi-Mamba: Hierarchical Mamba for Efficient Image Super-Resolution},
author = {Junbo Qiao and Jincheng Liao and Wei Li and Yulun Zhang and Yong Guo and Yi Wen and Zhangxizi Qiu and Jiao Xie and Jie Hu and Shaohui Lin},
journal= {arXiv preprint arXiv:2410.10140},
year = {2024}
}