Max pooling is the de facto standard for converting anomaly score maps into image-level decisions in memory-bank-based unsupervised anomaly detection (UAD). However, because it relies on a single extreme response, it discards most information about how anomaly evidence is distributed and structured across the image, often causing normal and anomalous scores to overlap. We propose StructCore, a training-free, structure-aware image-level scoring method that goes beyond max pooling. Given an anomaly score map, StructCore computes a low-dimensional structural descriptor phi(S) that captures distributional and spatial characteristics, and refines image-level scoring via a diagonal Mahalanobis calibration estimated from train-good samples, without modifying pixel-level localization. StructCore achieves image-level AUROC scores of 99.6% on MVTec AD and 98.4% on VisA, demonstrating robust image-level anomaly detection by exploiting structural signatures missed by max pooling.
@article{arxiv.2602.17048,
title = {StructCore: Structure-Aware Image-Level Scoring for Training-Free Unsupervised Anomaly Detection},
author = {Joongwon Chae and Lihui Luo and Yang Liu and Runming Wang and Dongmei Yu and Zeming Liang and Xi Yuan and Dayan Zhang and Zhenglin Chen and Peiwu Qin and Ilmoon Chae},
journal= {arXiv preprint arXiv:2602.17048},
year = {2026}
}