Enhancing Diffusion Posterior Sampling for Inverse Problems by Integrating Crafted Measurements
This work addresses a specific bottleneck in diffusion-based methods for image restoration tasks, representing an incremental improvement over existing posterior sampling techniques.
The paper tackles the problem of premature introduction of high-frequency information during early stages of diffusion posterior sampling for inverse problems, which causes larger posterior estimate errors. The proposed DPS-CM method integrates crafted measurements to mitigate this misalignment, significantly improving performance on tasks like Gaussian deblurring, super-resolution, and inpainting compared to existing approaches.
Diffusion models have emerged as a powerful foundation model for visual generations. With an appropriate sampling process, it can effectively serve as a generative prior for solving general inverse problems. Current posterior sampling-based methods take the measurement (i.e., degraded image sample) into the posterior sampling to infer the distribution of the target data (i.e., clean image sample). However, in this manner, we show that high-frequency information can be prematurely introduced during the early stages, which could induce larger posterior estimate errors during restoration sampling. To address this observation, we first reveal that forming the log-posterior gradient with the noisy measurement ( i.e., noisy measurement from a diffusion forward process) instead of the clean one can benefit the early posterior sampling. Consequently, we propose a novel diffusion posterior sampling method DPS-CM, which incorporates a Crafted Measurement (i.e., noisy measurement crafted by a reverse denoising process, rather than constructed from the diffusion forward process) to form the posterior estimate. This integration aims to mitigate the misalignment with the diffusion prior caused by cumulative posterior estimate errors. Experimental results demonstrate that our approach significantly improves the overall capacity to solve general and noisy inverse problems, such as Gaussian deblurring, super-resolution, inpainting, nonlinear deblurring, and tasks with Poisson noise, relative to existing approaches. Code is available at: https://github.com/sjz5202/DPS-CM.