Robust image watermarking based on quantization index modulation

A robust image watermarking based on the quantization index modulation (QIM) method is proposed. Conventional QIM methods employ a xed quantization step-size that results in poor robustness of the algorithm. In this paper, the quantization step-size in the QIM method is adaptively selected using a power-law function. To keep the watermark imperceptible and increase its robustness, the low frequency components of high entropy image blocks are used for data hiding. The analytical error probability and embedding distortion are derived and assessed by simulations on artificial signals. The optimum parameter in the power-law function is obtained based on minimizing the error probability. Experimental results con rm the superiority of the proposed technique against common attacks in comparison with the recently proposed methods.