Watermarking is a good defense against illicit copying, and other misuses of copyright information. Watermarks should be both invisible and robust. It is easy to place an invisible watermark, but it is not so easy to make it robust; often, one can remove a watermark by compression-decompression, and other attacks.

The new ideas in this paper show how a watermark in a black-and-white picture can be protected against JPEG and JPEG2000 compressions, and other attacks. One of the new ideas is visual masking, in which the watermark is added to the third or fourth level of the complex wavelet transform of the picture. For these new ideas to become commercially important, they should be tried on color pictures and music.