S-Adapter: Generalizing Vision Transformer for Face Anti-Spoofing with Statistical Tokens

TL;DR

This paper introduces S-Adapter, a novel statistical adapter for Vision Transformers that enhances cross-domain face anti-spoofing by capturing local statistical features and reducing domain style variance, leading to improved generalization.

Contribution

The paper proposes a new Statistical Adapter (S-Adapter) and Token Style Regularization (TSR) to improve cross-domain generalization of Vision Transformers in face anti-spoofing tasks.

Findings

S-Adapter outperforms state-of-the-art methods in zero-shot and few-shot cross-domain tests.

TSR effectively reduces domain style variance, enhancing model robustness.

The approach demonstrates significant improvements on benchmark datasets.

Abstract

Face Anti-Spoofing (FAS) aims to detect malicious attempts to invade a face recognition system by presenting spoofed faces. State-of-the-art FAS techniques predominantly rely on deep learning models but their cross-domain generalization capabilities are often hindered by the domain shift problem, which arises due to different distributions between training and testing data. In this study, we develop a generalized FAS method under the Efficient Parameter Transfer Learning (EPTL) paradigm, where we adapt the pre-trained Vision Transformer models for the FAS task. During training, the adapter modules are inserted into the pre-trained ViT model, and the adapters are updated while other pre-trained parameters remain fixed. We find the limitations of previous vanilla adapters in that they are based on linear layers, which lack a spoofing-aware inductive bias and thus restrict the cross-domain generalization. To address this limitation and achieve cross-domain generalized FAS, we propose a novel Statistical Adapter (S-Adapter) that gathers local discriminative and statistical information from localized token histograms. To further improve the generalization of the statistical tokens, we propose a novel Token Style Regularization (TSR), which aims to reduce domain style variance by regularizing Gram matrices extracted from tokens across different domains. Our experimental results demonstrate that our proposed S-Adapter and TSR provide significant benefits in both zero-shot and few-shot cross-domain testing, outperforming state-of-the-art methods on several benchmark tests. We will release the source code upon acceptance.