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FOCAL

An official implementation code for paper "Rethinking Image Forgery Detection via Contrastive Learning and Unsupervised Clustering"

Table of Contents

• Background
• Dependency
• Usage
• Citation

Background

Image forgery detection aims to detect and locate forged regions in an image. Most existing forgery detection algorithms formulate classification problems to classify pixels into forged or pristine. However, the definition of forged and pristine pixels is only relative within one single image, e.g., a forged region in image A is actually a pristine one in its source image B (splicing forgery). Such a relative definition has been severely overlooked by existing methods, which unnecessarily mix forged (pristine) regions across different images into the same category.

To resolve this dilemma, we propose the FOrensic ContrAstive cLustering (FOCAL) method, a novel, simple yet very effective paradigm based on contrastive learning and unsupervised clustering for the image forgery detection. Specifically, FOCAL 1) utilizes pixel-level contrastive learning to supervise the high-level forensic feature extraction in an image-by-image manner, explicitly reflecting the above relative definition; 2) employs an on-the-fly unsupervised clustering algorithm (instead of a trained one) to cluster the learned features into forged/pristine categories, further suppressing the cross-image influence from training data; and 3) allows to further boost the detection performance via simple feature-level concatenation without the need of retraining.

Extensive experimental results over six public testing datasets demonstrate that our proposed FOCAL significantly outperforms the state-of-the-art competing algorithms by big margins: +24.3% on Coverage, +18.6% on Columbia, +17.5% on FF++, +14.2 on MISD, +13.5% on CASIA and +10.3% on NIST in terms of IoU. The paradigm of FOCAL could bring fresh insights and serve as a novel benchmark for the image forgery detection task.

Dependency

• torch 1.9.0
• scikit-learn 1.2.1
• torch_kmeans 0.2.0

Usage

• For training:

python main.py --type='train'

• For testing:

python main.py --type='test_single'

FOCAL will detect the images in the demo/input/ and save the results in the demo/output/ directory.

• For prepare the training/test datasets:

python main.py --type='flist' --path_input 'demo/input/' --path_gt 'demo/gt/' --nickname 'demo'

Note: The pretrained FOCAL can be downloaded from Google Drive.

Note: To facilitate reproduction, we provide the download link of test datasets used in the FOCAL experiments: Columbia, Coverage, CASIA, NIST, MISD, FFpp. Please follow relevant licenses and use them for research purposes only.

Citation

If you use this code for your research, please citing the reference:

@article{focal,
  title={Rethinking Image Forgery Detection via Contrastive Learning and Unsupervised Clustering},
  author={H. Wu and Y. Chen and J. Zhou},
  year={2023}
}