An image watermarking scheme using HVS characteristics and spread transform

The paper presents a robust digital image watermarking scheme that uses both the characteristics of the human visual system (HVS) and statistical information measure. Spread transform approach is used where data is embedded through transform coefficients of both the cover and the watermark data. The spread transform watermarking technique yields better results in terms of imperceptibility, resiliency, capacity and cost compared to widely used spread spectrum watermarking schemes. Hadamard transformation is used not only for simpler implementation but also for its higher data hiding capacity (M. Ramkumar and AN Akansu, 2001). Experimental results show that the visual quality of the extracted watermark is good in spite of several external attacks. The fact is also supported by mutual information values used as objective measure.