Visible watermarking assessment metrics based on just noticeable distortion

During the last two decades, several visible watermarking algorithms with different characteristics have been proposed. In the context of visible digital watermarking, watermark visibility and its non-obtrusiveness are essential issues. However, assessment metrics were not established to evaluate these two issues until now. Due to the lack of established assessment metrics, visibility is evaluated in a subjective manner and the obtrusiveness caused by the visible watermark is evaluated by well-known image quality metrics, such as peak signal noise ratio, comparing the host image and the watermarked image. In this paper, we propose four assessment metrics for visible watermarking algorithms, in which the global visibility, global obtrusiveness, local obtrusiveness in host edge region, and a global quality of watermarked image are evaluated using a couple of criteria based on the human visual system and a pixel-based just-noticeable distortion function. The evaluation results show the reliability of the proposed metrics used for measuring the above-mentioned aspects when several visible watermarking algorithms are employed as well as in several scenarios where an attempt to remove the watermark pattern from the watermarked content was made.