Self-Supervised Learning for Real-World Super-Resolution From Dual and Multiple Zoomed Observations

In this paper, we consider two challenging issues in reference-based super-resolution (RefSR) for smartphone, (i) how to choose a proper reference image, and (ii) how to learn RefSR in a self-supervised manner. Particularly, we propose a novel self-supervised learning approach for real-world RefSR from observations at dual and multiple camera zooms. Firstly, considering the popularity of multiple cameras in modern smartphones, the more zoomed (telephoto) image can be naturally leveraged as the reference to guide the super-resolution (SR) of the lesser zoomed (ultra-wide) image, which gives us a chance to learn a deep network that performs SR from the dual zoomed observations (DZSR). Secondly, for self-supervised learning of DZSR, we take the telephoto image instead of an additional high-resolution image as the supervision information, and select a center patch from it as the reference to super-resolve the corresponding ultra-wide image patch. To mitigate the effect of the misalignment between ultra-wide low-resolution (LR) patch and telephoto ground-truth (GT) image during training, we propose a two-stage alignment method, including patch-based optical flow alignment and auxiliary-LR guiding alignment. To generate visually pleasing results, we present local overlapped sliced Wasserstein loss. Furthermore, we take multiple zoomed observations to explore self-supervised RefSR, and present a progressive fusion scheme for the effective utilization of reference images. Experiments show that our methods achieve better quantitative and qualitative performance against state-of-the-arts.

I. Introduction

Image super-resolution (SR) [1], [2], [3], [4], [5] aiming to recover a high-resolution (HR) image from its low-resolution (LR) counterpart is a severely ill-posed inverse problem with many practical applications. Recently, reference-based image SR (RefSR) [6], [7], [8], [9], [10], [11], [12], [13], [14], [15] has made progress in relaxing the ill-posedness, which suggests to super-resolve the LR image for more accurate details by leveraging a reference (Ref) image, as shown in Fig. 1(a).