Watermarking and Coefficient Scanning for Light Field Images in 4D-DCT Domain

Light field images have emerged as an important advance in the representation of visual data; at the same time, dealing with such images has brought new challenges related to multimedia transmission and security. In this article, we introduce a robust and blind scheme to watermark lenslet light field images. The method, which is based on quantization index modulation, allows to recover the watermark even after the image is submitted to compression in the 4D-DCT (four-dimensional discrete cosine transform) domain or other attacks. To achieve this, an empirical strategy for scanning the coefficients in the referred domain is also proposed; we demonstrate that, in general, such a strategy outperforms state-of-the-art methods whose purpose is to exploit the energy compacting property of the 4D-DCT. The introduced watermarking scheme has been evaluated using 30 light field images and several embedding / extracting parameters. The obtained results indicate that the watermark is satisfactorily imperceptible and confirm its robustness against various attacks.