Kernel Agnostic Real-world Image Super-resolution

Recently, deep neural network models have achieved impressive results in various research fields. Come with it, an increasing number of attentions have been attracted by deep super-resolution (SR) approaches. Many existing methods attempt to restore high-resolution images from directly down-sampled low-resolution images or with the assumption of Gaussian degradation kernels with additive noises for their simplicities. However, in real-world scenarios, highly complex kernels and non-additive noises may be involved, even though the distorted images are visually similar to the clear ones. Existing SR models are facing difficulties to deal with real-world images under such circumstances. In this paper, we introduce a new kernel agnostic SR framework to deal with real-world image SR problem. The framework can be hanged seamlessly to multiple mainstream models. In the proposed framework, the degradation kernels and noises are adaptively modeled rather than explicitly specified. Moreover, we also propose an iterative supervision process and frequency-attended objective from orthogonal perspectives to further boost the performance. The experiments validate the effectiveness of the proposed framework on multiple real-world datasets.