Image and video compression and copyright protection.

摘要

An upsoaring number of digital images and videos demand efficient compression to facilitate storage and transmission of images and videos over Internet, and effective security and copyright protection techniques against malicious fabrication and illegal copy of digital contents.;First, we focus on transform and quantizer design for compression. We design integer reversible transforms with the stabilized and optimized PLUS factorization for unified lossy/lossless compression. The proposed integer DCTs and integer Lapped Biorthogonal Transform have better lossy/lossless image coding performance than some existing integer DCT and the integer Lapped Transform in JPEG-XR. Moreover, we propose an adaptive quantizer using piecewise companding and scaling for gaussian mixture with three modes. The proposed quantizers approximate MSE performance of Lloyd-Max quantizers but only with similar complexity of uniform quantizers, and achieve higher perceptual quality in High Dynamic Range(HDR) images compression. Furthermore, we propose an optimal vector quantizer approximator by using transforms plus scalar quantizers with small complexity. The system is built on the tri-axis coordinate frame, works for both circular and elliptical distributions, and almost always outperforms restricted/unrestricted polar quantizers, and rectangular quantizers.;Second, we study copyright protection of digital contents. The proposed image hashes by using companding and gray code have a small collision rate, strong discriminability and are difficult to analyze by attackers. We also propose an image authentication technique by feature point clustering and matching. Query images are authenticated with anchor images. The query images are registered, and the possible tampered areas are detected. Moreover, a robust track-and-trace video watermarking system is developed with watermarking embedder and detector. In the embedder, we insert a watermark pattern into video frames according to a watermark payload weighted by the human perceptual model, and transform videos with geometric anti-collusion codes. In the detector, Kanade-Lucas-Tomasi feature tracker is used to register the candidate videos, and the cross-correlation sequence is binarized, ECC decoded and decrypted. This system is very robust to both geometric attacks and collusion attacks, and watermarks are perceptually invisible to human vision system.