Watermark-Preserving Keypoint Enhancement for Screen-Shooting Resilient Watermarking

Screen-shooting resilient (SSR) watermark is a special kind of robust watermarking. One can extract the watermark message even the embedded image communicates via a physical screen to the camera channel. The keypoint-based SSR watermarking is one promising solution to realize such screen-to-camera communication. The enhanced keypoints were used to locate the embedding region and then perform watermark embedding. However, the keypoint-based SSR watermarking treats the critical two steps, keypoint enhancement and watermark embedding, independently, neglecting their inter-play. This work proposes a watermark-preserving keypoint enhancement algorithm for SSR watermarking. Specifically, we resort to a convex constrained optimization framework to unify keypoint enhancement and watermark embedding. Multiple constraints are imposed to simultaneously ensure the watermark validity and blind synchronization of embedding regions. Our method enables jointly optimizing the watermarking distortion and keypoint enhancement. The proposed method achieves superior watermark extraction accuracy while retaining better watermarked image quality when compared with previous works.