A color value differentiation scheme for blind digital image watermarking

摘要

In order to contribute to the security of medical image, we present in this paper a blind and robust watermarking technique that allows the integration of the electronic patient's record into retinal images. In our work, we present an approach developed to find a compromise between capacity and imperceptibility. The proposed blind watermarking approach is based on the color values difference calculation between pixels to determine the substitution to be made. We proposed in this work ten possible variants of this approach to determine which offers the best compromise between the capacity and the imperceptibility. Following the evaluation of the approach by metrics designed for reliability tests, some variants confirm remarkably good results either by objective or subjective evaluation. The capacity and imperceptibility evaluations reveal very encouraging results. We obtained good results concerning the imperceptibility with a PSNR greater than 69 dB for some variants due to the insignificance of the least significant bits modification. An evaluation of the watermark's robustness demonstrates the proposed schemas generate reasonably robust watermarked samples against various attacks. A high-quality watermark with a normalized cross-correlation greater than 0.9 for some variants is obtained. However, some variants remain weak in terms of robustness because any simple treatment can modify the LSBs, which makes the extraction impossible.