CLIP-Flow: A Universal Discriminator for AI-Generated Images Inspired by Anomaly Detection

Fuente: arXiv
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Auteurs principaux: Yuan, Zhipeng, Wang, Kai, Quan, Weize, Yan, Dong-Ming, Wu, Tieru
Format: Preprint
Publié: 2025
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author Yuan, Zhipeng
Wang, Kai
Quan, Weize
Yan, Dong-Ming
Wu, Tieru
author_facet Yuan, Zhipeng
Wang, Kai
Quan, Weize
Yan, Dong-Ming
Wu, Tieru
contents With the rapid advancement of AI generative models, the visual quality of AI-generated images (AIIs) has become increasingly close to natural images, which inevitably raises security concerns. Most AII detectors often employ the conventional image classification pipeline with natural images and AIIs (generated by a generative model), which can result in limited detection performance for AIIs from unseen generative models. To solve this, we proposed a universal AI-generated image detector from the perspective of anomaly detection. Our discriminator does not need to access any AIIs and learn a generalizable representation with unsupervised learning. Specifically, we use the pre-trained CLIP encoder as the feature extractor and design a normalizing flow-like unsupervised model. Instead of AIIs, proxy images, e.g., obtained by applying a spectral modification operation on natural images, are used for training. Our models are trained by minimizing the likelihood of proxy images, optionally combined with maximizing the likelihood of natural images. Extensive experiments demonstrate the effectiveness of our method on AIIs produced by various image generators.
format Preprint
id arxiv_https___arxiv_org_abs_2508_09477
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle CLIP-Flow: A Universal Discriminator for AI-Generated Images Inspired by Anomaly Detection
Yuan, Zhipeng
Wang, Kai
Quan, Weize
Yan, Dong-Ming
Wu, Tieru
Computer Vision and Pattern Recognition
Cryptography and Security
With the rapid advancement of AI generative models, the visual quality of AI-generated images (AIIs) has become increasingly close to natural images, which inevitably raises security concerns. Most AII detectors often employ the conventional image classification pipeline with natural images and AIIs (generated by a generative model), which can result in limited detection performance for AIIs from unseen generative models. To solve this, we proposed a universal AI-generated image detector from the perspective of anomaly detection. Our discriminator does not need to access any AIIs and learn a generalizable representation with unsupervised learning. Specifically, we use the pre-trained CLIP encoder as the feature extractor and design a normalizing flow-like unsupervised model. Instead of AIIs, proxy images, e.g., obtained by applying a spectral modification operation on natural images, are used for training. Our models are trained by minimizing the likelihood of proxy images, optionally combined with maximizing the likelihood of natural images. Extensive experiments demonstrate the effectiveness of our method on AIIs produced by various image generators.
title CLIP-Flow: A Universal Discriminator for AI-Generated Images Inspired by Anomaly Detection
topic Computer Vision and Pattern Recognition
Cryptography and Security
url https://arxiv.org/abs/2508.09477