arXiv Machine Learning
1d ago

Convergent Plug-and-Play Image Restoration with Annealed Noise Levels

The paper presents convergence guarantees for Plug-and-Play (PnP) image restoration algorithms that use annealed noise levels, covering both deterministic and stochastic methods. It identifies explicit nonconvex objectives linked to the final denoising level and proves that iterates become asymptotically stationary with respect to these objectives, without requiring a specific noise decay schedule. The authors validate their theory experimentally on tasks such as inpainting, super‑resolution, demosaicing, and tomography.

By Samuel Hurault
arXiv Computer Vision
Sep 24

Image Denoising Using Lower Semi-Frames

A blind image denoising framework based on an infinite directional lower semi-frame (DLSF) is introduced for additive white Gaussian noise. The method estimates noise variance directly in the DLSF domain using joint covariance of four directional difference channels, then applies channel‑wise Wiener‑type shrinkage and canonical‑dual synthesis with data‑consistent iterative reconstruction. Experiments on three standard grayscale images show a mean relative noise‑estimation error of 3.28 % and average PSNR gains of 7.45 dB, improving to 8.31 dB at 30/255 noise.

By Hemalatha M, P. Sam Johnson