PIMoG: An Effective Screen-shooting Noise-Layer Simulation for Deep-Learning-Based Watermarking Network

With the omnipresence of camera phone and digital display, capturing digitally displayed image with camera phone are getting widely practiced. In the context of watermarking, this brings forth the issue of screen-shooting robustness. The key to acquiring screenshooting robustness is designing a good noise layer that could represent screen-shooting distortions in a deep-learning-based watermarking framework. However, it is very difficult to quantitatively formulate the screen-shooting distortion since the screen-shooting process is too complex. In order to design an effective noise layer for screen-shooting robustness, we propose new insight in this paper, that is, it is not necessary to quantitatively simulate the overall procedure in the screen-shooting noise layer, only including the most influenced distortions is enough to generate an effective noise layer with strong robustness. To verify this insight, we propose a screen-shooting noise layer dubbed PIMoG. Specifically, we summarize the most influenced distortions of screen-shooting process into three parts (perspective distortion, illumination distortion and moiré distortion) and further simulate them in a differentiable way.For the rest distortion, we utilize the Gaussian noise to approximate the main part of them. As a result, the whole network can be trained end-to-end with such noise layer. Extensive experiments illustrate the superior performance of the proposed PIMoG noise layer. In addition to the noise layer design, we also propose a gradient maskguided image loss and an edge mask-guided image loss to further improve the robustness and invisibility of the whole network respectively. Based on the proposed loss and PIMoG noise layer, the whole framework outperforms the SOTA watermarking method with at least 5% in extraction accuracy and achieves more than 97% accuracy in different screen-shooting conditions.