基于迭代交替优化的图像盲超分辨率重建

基于深度卷积神经网络的图像超分辨率重建算法通常假设低分辨率图像的降质是固定且已知的，如双3次下采样等，因此难以处理降质(如模糊核及噪声水平)未知的图像。针对此问题，该文提出联合估计模糊核、噪声水平和高分辨率图像，设计了一种基于迭代交替优化的图像盲超分辨率重建网络。在所提网络中，图像重建器以估计的模糊核和噪声水平作为先验信息，由低分辨率图像重建出高分辨率图像；同时，综合低分辨率图像和估计的高分辨率图像，模糊核及噪声水平估计器分别实现模糊核和噪声水平的估计。进一步地，该文提出对模糊核/噪声水平估计器及图像重建器进行迭代交替的端对端优化，以提高它们的兼容性并使其相互促进。实验结果表明，与IKC, DASR, MANet, DAN等现有算法相比，提出方法在常用公开测试集(Set5, Set14, B100, Urban100)及真实场景图像上都取得了更优的性能，能够更好地对降质未知的图像进行重建；同时，提出方法在参数量或处理效率上也有一定的优势。

Blind Image Super-resolution Reconstruction via Iterative and Alternative Optimization

Deep convolutional neural network-based image Super-Resolution (SR) methods assume generally that the degradations of Low-Resolution (LR) images are fixed and known (e.g., bicubic downsampling). Thus, they are almost unable to super-resolve images with unknown degradations (e.g., blur kernel and noise level). To address this problem, an iterative and alternative optimization-based blind image SR network is proposed, in which the blur kernel, noise level, and High-Resolution (HR) image are jointly estimated. Specifically, in the proposed method, the image reconstruction network reconstructs an HR image from the given LR image using the estimated blur kernel and noise level as prior knowledge. Correspondingly, the blur kernel and noise level estimators estimate the blur kernel and noise level respectively from the given LR image and the reconstructed HR image. To improve compatibility and promote each other mutually, the blur kernel estimator, noise level estimator, and image reconstruction network are iteratively and alternatively optimized in an end-to-end manner. The proposed network is compared with state-of-the-art methods (i.e., IKC, DASR, MANet, DAN) on commonly used benchmarks (i.e., Set5, Set14, B100, and Urban100) and real-world images. Results show that the proposed method achieves better performance on LR images with unknown degradations. Moreover, the proposed method has advantages in model size or processing efficiency.