arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2408.09151cs.CVeess.IV

面向极端图像缩放的时间步感知扩散模型

Timestep-Aware Diffusion Model for Extreme Image Rescaling

School of Remote Sensing and Information Engineering, Wuhan University(武汉大学遥感信息工程学院)

Ce Wang, Zhenyu Hu, Wanjie Sun, Zhenzhong Chen

AI总结:

本文提出时间步感知扩散模型TADM,通过在预训练自编码器潜在空间中结合伪可逆模块与时间步对齐策略,利用文本到图像扩散模型的先验解决极端图像缩放中的不适定问题,在定量与定性评估中均优于现有方法。

摘要:

图像缩放旨在学习能够被精确重建为原始高分辨率(HR)对应图像的最优低分辨率(LR)图像,从而为超高清媒体提供一种高效的图像处理与存储方法。然而,极端下采样因子由于其高度不适定的特性,给上采样过程带来了重大挑战,导致现有图像缩放方法难以生成语义正确的结构和感知友好的纹理。在本工作中,我们提出了一种名为时间步感知扩散模型(TADM)的新框架,用于极端图像缩放。该框架在预训练自编码器的潜在空间中执行缩放操作,并有效利用预训练文本到图像扩散模型学习到的强大自然图像先验。具体而言,TADM采用一个伪可逆模块来建立HR图像潜在特征与目标尺寸LR图像之间的双向映射。随后,缩放后的潜在特征通过预训练扩散模型进行增强,以生成更逼真的细节。考虑到缩放操作引起的空间非均匀退化,我们提出了一种新颖的时间步对齐策略,该策略能够根据重建潜在特征的质量自适应地分配扩散模型的生成能力。大量实验表明,TADM在定量和定性评估中均优于先前的方法。

英文摘要:

Image rescaling aims to learn the optimal low-resolution (LR) image that can be accurately reconstructed to its original high-resolution (HR) counterpart, providing an efficient image processing and storage method for ultra-high definition media. However, extreme downscaling factors pose significant challenges to the upscaling process due to its highly ill-posed nature, causing existing image rescaling methods to struggle in generating semantically correct structures and perceptual friendly textures. In this work, we propose a novel framework called Timestep-Aware Diffusion Model (TADM) for extreme image rescaling, which performs rescaling operations in the latent space of a pre-trained autoencoder and effectively leverages powerful natural image priors learned by a pre-trained text-to-image diffusion model. Specifically, TADM adopts a pseudo-invertible module to establish the bidirectional mapping between the latent features of the HR image and the target-sized LR image. Then, the rescaled latent features are enhanced by a pre-trained diffusion model to generate more faithful details. Considering the spatially non-uniform degradation caused by the rescaling operation, we propose a novel time-step alignment strategy, which can adaptively allocate the generative capacity of the diffusion model based on the quality of the reconstructed latent features. Extensive experiments demonstrate the superiority of TADM over previous methods in both quantitative and qualitative evaluations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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