A semi-fragile lossless digital watermarking based on adaptive threshold for image authentication

In this paper, a novel semi-fragile lossless digital watermarking method based on adaptive threshold for image authentication is presented. Most of the existing semi-fragile lossless watermarking schemes are based on modulo-256 addition to achieve losslessness. In order to avoid the salt-and-pepper noise, some of the schemes ignore the blocks which lead to overflow/underflow, and using error correction codes (ECCs). But the ECC will reduce available embedding capacity, especially for the complex images. We then propose an adaptive threshold method to improve the existing schemes. By employing a robust statistical quantity based on the patchwork to embed data, identifying image complexity based on wavelet-domain generalised Gaussian distribution (GGD) and using it to adaptively quantise thresholds which differentiating the embedding process, and using simple ECC, this technique has achieved losslessness, robustness and more competitive available embedding capacity. Experimental results demonstrate that the capacity of watermarked image of this technique is highly improved, and the quality of the image is acceptable.