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Blind Image Super-Resolution with Degradation-Aware Adaptation
Most existing super-resolution (SR) methods are designed to restore high resolution (HR) images from certain low resolution (LR) images with a simple degradation, e.g. bicubic downsampling. Their generalization capability to real-world degradation is limited because it often couples several degradation factors such as noise and blur. To solve this problem, existing blind SR methods rely on either explicit degradation estimation or translation to bicubicly downsampled LR images, where inaccurate estimation or translation would severely deteriorate the SR performance. In this paper, we propose a plug-and-play module, which could be applied to any existing image super-resolution model for feature-level adaptation to improve the generalization ability to real-world degraded images. Specifically, the degradation encoder computes an implicit degradation representation which is supervised by a ranking loss based on the degradation level. The degradation representation then works as a kind of condition and is applied to the existing image super-resolution model pretrained on bicubicly downsampled LR images through the proposed region-aware modulation. With the proposed method, the base super-resolution model could be fine-tuned to adapt to the condition of degradation representation for further improvement. Experimental results on both synthetic and real-world datasets show that the proposed image SR method with compact model size performs favorably against state-of-the-art methods.