On Perceptual Quality of Watermarked Images – An Experimental Approach

One challenge in designing content authentication watermarks is how to achieve a good balance between robustness against incidental distortions, fragility to tampering attacks, and maintaining an acceptable visual quality. In this paper, we present a performance analysis of a wavelet-based semi-fragile watermarking algorithm in terms of its impact on the perceptual quality of watermarked images. We use three different quality metrics to measure the degradation of the test images’ visual quality. Based on our experimental results, we propose limits on the algorithm parameters in order to achieve an acceptable balance between good robustness and minimal perceptual quality impact. We also present a sliding-window technique that helps in choosing appropriate wavelet decomposition levels for embedding the watermark bits.