  GAN-generated image detection now becomes the first line of defense against
the malicious uses of machine-synthesized image manipulations such as
deepfakes. Although some existing detectors work well in detecting clean, known
GAN samples, their success is largely attributable to overfitting unstable
features such as frequency artifacts, which will cause failures when facing
unknown GANs or perturbation attacks. To overcome the issue, we propose a
robust detection framework based on a novel multi-view image completion
representation. The framework first learns various view-to-image tasks to model
the diverse distributions of genuine images. Frequency-irrelevant features can
be represented from the distributional discrepancies characterized by the
completion models, which are stable, generalized, and robust for detecting
unknown fake patterns. Then, a multi-view classification is devised with
elaborated intra- and inter-view learning strategies to enhance view-specific
feature representation and cross-view feature aggregation, respectively. We
evaluated the generalization ability of our framework across six popular GANs
at different resolutions and its robustness against a broad range of
perturbation attacks. The results confirm our method's improved effectiveness,
generalization, and robustness over various baselines.
