Robust sinusoidal watermark for images

A robust two-dimensional watermark for images which is quite secure and reliably detected under the influences of signal processing and/or geometrical alterations is proposed. The watermark is a matrix in which the rows are information-bearing pseudorandom sequences and columns are sinusoidal waves of a fixed frequency. The sinusoidal wave is used to confirm the existence of the watermark and to compensate for possible geometric distortion. To spread the energy across an image, the watermark is added to a set of selected samples in the sub-band domain. Experiments demonstrate the robustness and reliable detectability of the proposed watermark whether or not reference is made to the original image.