Unlocking the Forgery Detection Potential of Vanilla MLLMs: A Novel Training-Free Pipeline

TL;DR

This paper introduces Foresee, a training-free pipeline leveraging vanilla multimodal large language models for image forgery detection, achieving superior localization and explanation capabilities without additional training.

Contribution

It presents a novel training-free approach that enhances vanilla MLLMs for image forgery detection, surpassing existing methods in accuracy, interpretability, and generalization.

Findings

Outperforms existing methods in tamper localization accuracy

Provides richer textual explanations for forgeries

Demonstrates strong generalization across diverse tampering types

Abstract

With the rapid advancement of artificial intelligence-generated content (AIGC) technologies, including multimodal large language models (MLLMs) and diffusion models, image generation and manipulation have become remarkably effortless. Existing image forgery detection and localization (IFDL) methods often struggle to generalize across diverse datasets and offer limited interpretability. Nowadays, MLLMs demonstrate strong generalization potential across diverse vision-language tasks, and some studies introduce this capability to IFDL via large-scale training. However, such approaches cost considerable computational resources, while failing to reveal the inherent generalization potential of vanilla MLLMs to address this problem. Inspired by this observation, we propose Foresee, a training-free MLLM-based pipeline tailored for image forgery analysis. It eliminates the need for additional training and enables a lightweight inference process, while surpassing existing MLLM-based methods in both tamper localization accuracy and the richness of textual explanations. Foresee employs a type-prior-driven strategy and utilizes a Flexible Feature Detector (FFD) module to specifically handle copy-move manipulations, thereby effectively unleashing the potential of vanilla MLLMs in the forensic domain. Extensive experiments demonstrate that our approach simultaneously achieves superior localization accuracy and provides more comprehensive textual explanations. Moreover, Foresee exhibits stronger generalization capability, outperforming existing IFDL methods across various tampering types, including copy-move, splicing, removal, local enhancement, deepfake, and AIGC-based editing. The code will be released in the final version.