SP^3: 用于即插即用复原的球形先验

摘要

本文提出了一种新颖的即插即用算法SP^3，该算法通过用球形编码器（Spherical Encoders, SE）作为生成先验来替代去噪器，从而加速最大后验图像恢复。SP^3利用SE紧密结构的潜在空间作为自然图像流形的鲁棒投影，来近似处理难以求解的邻近先验步骤。借助半二次分裂（Half-Quadratic Splitting）将此投影与闭式数据一致性步骤交替进行，可在推理过程中无需梯度计算即实现稳定收敛。这种独特的公式赋予了“随时”恢复的能力，从首次迭代起即可生成清晰合理的图像。在多种图像恢复任务上的评估表明，SP^3在感知质量上与最先进的零样本扩散和流方法相当，而速度提升了3至630倍。

English

In this paper, we introduce SP^3, a novel Plug-and-Play algorithm that accelerates maximum a posteriori image restoration by replacing denoisers with Spherical Encoders (SE) as generative priors. SP^3 approximates the intractable proximal prior step by utilizing the SE tightly structured latent space as a robust projection onto the natural image manifold. Alternating this projection with a closed-form data-consistency step, via Half-Quadratic Splitting, achieves stable convergence without requiring gradient computation during inference. This unique formulation unlocks "anytime" restoration capabilities, producing sharp, plausible images from the first iteration. Evaluations across a variety of image restoration tasks demonstrate that SP^3 achieves perceptual quality comparable to state-of-the-art zero-shot diffusion and flow methods while being 3-630times faster.