Watermark strength determination based on a new contrast masking model

摘要

This paper presents a new approach in the selection of auspicious sites to be watermarked. The selection takes into account human visual system properties including luminance adaptation, contrast sensitivity and spatio-frequential selectivity. The paper exploits also the local band limited contrast to determine the maximum watermark strength to be applied without inducing visible degradations. Compared to the well known approaches, a contrast masking model is used here to adjust, site by site, the watermark strength. To test the approach efficiency, obtained results are considered in the context of an adaptive watermarking algorithm. The performance of this latter is evalauted in terms of watermark invisibility. Robustness to most common attacks such as JPEG compression, cropping (with zero padding) and low pass filtering is also considered.