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+.alpha.. Ri, where Ci and Ci' are wavelet transform coefficients of the image, and .alpha. is a scaling factor. .alpha. 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 .alpha. is too big the watermark is perceptible in the image. If .alpha. is too small the mark may not survive processing of the image.