Image-adaptive Watermarking Using The Improved Signal to Noise Ratio

This paper presents a new perceptual quality metric (PQM), the improved signal to noise ratio (iSNR). The improvement is done in the following two aspects: 1) the SNR manifests much better performance in an image block of small size than in a whole image; 2) the average luminance and gradient information are added into the SNR. Next, a locally adaptive watermarking framework is described, which is based on the localized quality evaluation, and the implementation using iSNR, iSNR-SS is discussed. In comparison with ones based on the global quality evaluation, iSNR-SS exploits the localized signal characteristics sufficiently while guaranteeing the localized watermark invisibility. Experimental results demonstrate that the proposed watermarking performs very well both in robustness and invisibility