Robust Image Protection Countering Cropping Manipulation

Image cropping is a cheap yet effective operation of maliciously altering image contents. Existing cropping detection mechanisms analyze the fundamental traces of image cropping, for example, chromatic aberration and vignetting to uncover cropping attack. However, they are fragile to common post-processing attacks which deceive forensics by removing such cues. Besides, they ignore the fact that recovering the cropped-out contents can unveil the purpose of the behaved cropping attack. This paper presents a novel robust watermarking scheme for image Cropping Localization and Recovery (CLR-Net). We first protect the original image by introducing imperceptible perturbations. Then, typical image post-processing attacks are simulated to erode the protected image. On the recipient's side, we predict the cropping mask and recover the original image. We propose two plug-and-play networks to improve the real-world robustness of CLR-Net, namely, the Fine-Grained generative JPEG simulator (FG-JPEG) and the Siamese image pre-processing network. To the best of our knowledge, we are the first to address the combined challenge of image cropping localization and entire image recovery from a fragment. Experiments demonstrate that CLR-Net can accurately localize the cropping as well as recover the details of the cropped-out regions with both high quality and fidelity, despite the presence of image processing attacks of varied types.