EMBEDDING DATA IN MATERIAL

A spatial domain using image produced by a source is combined with watermark data Ri to produce a spatial domain watermarked image. The watermarked image is produced by an embedder according to equation: Ci′=Ci+α. Ri, where Ci and Ci′ are wavelet transform coefficients of the image, and α is a scaling factor. α is chosen so that the watermark is imperceptible in the image and to resist removal of the watermark by unauthorized processing. It is desirable that a has the smallest value which achieves that. If α is too big the watermark is perceptible in the image. If α is too small the mark may not survive processing of the image.