Large scale image super-resolution is a challenging computer vision task, since vast information is missing in a highly degraded image, say for example forscale x16 super-resolution. Diffusion models are used successfully in recent years in extreme super-resolution applications, in which Gaussian noise is used as a means to form a latent photo-realistic space, and acts as a link between the space of latent vectors and the latent photo-realistic space. There are quite a few sophisticated mathematical derivations on mapping the statistics of Gaussian noises making Diffusion Models successful. In this paper we propose a simple approach which gets away from using Gaussian noise but adopts some basic structures of diffusion models for efficient image super-resolution. Essentially, we propose a DNN to perform domain transfer between neighbor domains, which can learn the differences in statistical properties to facilitate gradual interpolation with results of reasonable quality. Further quality improvement is achieved by conditioning the domain transfer with reference to the input LR image. Experimental results show that our method outperforms not only state-of-the-art large scale super resolution models, but also the current diffusion models for image super-resolution. The approach can readily be extended to other image-to-image tasks, such as image enlightening, inpainting, denoising, etc.

翻译：大规模图像超分辨率是一项具有挑战性的计算机视觉任务，因为在高度退化的图像（例如16倍超分辨率）中，大量信息缺失。近年来，扩散模型被成功应用于极端超分辨率任务，其中高斯噪声被用作构建潜在逼真空间的手段，并充当潜向量空间与潜在逼真空间之间的桥梁。已有大量复杂数学推导来解释高斯噪声的统计特性，从而使得扩散模型取得成功。本文提出了一种简洁方法，该方法摒弃了高斯噪声的使用，但借鉴了扩散模型的基本结构以实现高效图像超分辨率。具体而言，我们设计了一个深度神经网络（DNN）来执行相邻域之间的域迁移，该网络能够学习不同域间统计特性的差异，从而逐步插值获得合理质量的结果。通过参考输入低分辨率（LR）图像对域迁移过程进行条件约束，进一步提升了生成质量。实验结果表明，我们的方法不仅优于当前最先进的大规模超分辨率模型，还超越了现有的图像超分辨率扩散模型。该方法可轻松扩展至其他图像到图像的任务，如图像增强、修复、去噪等。