用噪声匹配机制改进图像修复,让去噪器更可靠、结果更真实。
Beyond MMSE: Enhancing PnP Restoration with ProxiMAP

- 通过匹配迭代噪声与去噪器训练噪声,保持去噪器在分布内。
- 在去模糊、补全、超分等任务上显著提升重建清晰度。
- 无需改架构,可直接替换现有方法,适合图像恢复研究者使用。
插件式(PnP)方法通过将难以处理的后验最大(MAP)去噪器替换为均方误差最小(MMSE)去噪器,已成为解决成像逆问题的标准工具。尽管这种不匹配常被视为不可避免,近期工作尝试通过扩散模型得分来逼近MAP。我们发现这在实践中存在问题:学习到的得分与真实得分不符,导致以MAP为目标的迭代收敛至卡通化图像而非真实图像,且最佳效果出现在未完全收敛时。我们基于此观察提出新设计原则,引入ProxiMAP,其噪声调度使迭代残差噪声始终与去噪器训练噪声匹配。这确保去噪器始终处于分布内,从而获得可靠的得分,并实现隐式早停,避免上述失效模式。ProxiMAP是标准PnP算法中MMSE去噪器的模块化替代品,在去模糊、图像补全、超分辨率和相位恢复任务中持续提升重建质量。基于相同原理,我们还提出一种混合变体,仅在后期迭代应用ProxiMAP,此时去噪器最可靠——以极低计算成本达到或超过全替换版本的效果。
原文摘要 · Abstract (English)
Plug-and-Play (PnP) methods have become standard tools for solving imaging inverse problems by replacing the intractable maximum a posteriori (MAP) denoiser with the MMSE one. While this mismatch has been widely treated as unavoidable, recent works have sought to close this gap by targeting the MAP with diffusion-model scores. We show this is problematic in practice: learned scores do not match the true ones, so MAP-targeting iterations converge to cartoon-like images rather than realistic ones, and better results are obtained by stopping short of convergence. We turn this observation into a design principle and introduce ProxiMAP, an iterative MAP approximation whose noise schedule keeps the iterate's residual noise matched to the denoiser's training noise. This keeps the denoiser in-distribution where its score is reliable, and yields implicit early stopping that avoids the failure mode above. ProxiMAP is a modular drop-in replacement for MMSE denoisers in standard PnP algorithms and consistently sharpens reconstructions across deblurring, inpainting, super-resolution, and phase retrieval. Building on the same principle, we propose a hybrid variant that applies ProxiMAP only in the late iterations of PnP, where the denoiser is most reliable -- matching or exceeding the full-replacement variant at a fraction of the cost.
Thank you to arXiv for use of its open access interoperability. PaperDance 不是 arXiv 官方产品;中文卡片由大模型生成,请以原文为准。