TransFusion -- A Transparency-Based Diffusion Model for Anomaly Detection

Surface anomaly detection is a vital component in manufacturing inspection. Reconstructive anomaly detection methods restore the normal appearance of an object, ideally modifying only the anomalous regions. Due to the limitations of commonly used reconstruction architectures, the produced reconstructions are often poor and either still contain anomalies or lack details in anomaly-free regions. Recent reconstructive methods adopt diffusion models, however with the standard diffusion process the problems are not adequately addressed. We propose a novel transparency-based diffusion process, where the transparency of anomalous regions is progressively increased, restoring their normal appearance accurately and maintaining the appearance of anomaly-free regions without loss of detail. We propose TRANSparency DifFUSION (TransFusion), a discriminative anomaly detection method that implements the proposed diffusion process, enabling accurate downstream anomaly detection. TransFusion achieves state-of-the-art performance on both the VisA and the MVTec AD datasets, with an image-level AUROC of 98.5% and 99.2%, respectively.