PANDA: Perceptually Aware Neural Detection of Anomalies

Semi-supervised methods of anomaly detection have seen substantial advancement in recent years. Of particular interest are applications of such methods to diverse, real-world anomaly detection problems where anomalous variations can vary from the visually obvious to the very subtle. In this work, we propose a novel fine-grained VAE-GAN architecture trained in a semi-supervised manner in order to detect both visually distinct and subtle anomalies. With the use of a residually connected dual-feature extractor, a fine-grained discriminator and a perceptual loss function, we are able to detect subtle, low inter-class (anomaly vs. normal) variant anomalies with greater detection capability and smaller margins of deviation in AUC value during inference compared to prior work whilst also remaining time-efficient during inference. We achieve state-of-the-art anomaly detection results when compared extensively with prior semi-supervised approaches across a multitude of anomaly detection benchmark tasks including trivial leave-one-out tasks (CIFAR-10 - $\mathbf{AUPRC}_{avg}$: 0.91; MNIST - $\mathbf{AUPRC}_{avg}$: 0.90) in addition to challenging real-world anomaly detection tasks (plant leaf disease - AVC: 0.776; threat item X-ray - AVC: 0.51), video frame-level anomaly detection (VCSDPedl - AVC: 0.95) and high frequency texture with object anomalous defect detection (MVTEC - $\mathbf{AUC}_{avg}$: 0.83).