A method of embedding digital data in a source image includes the steps of: a) generating a multi-level data image representing the digital data; b) convolving the multi-level data image with an encoding carrier image to produce a frequency dispersed data image; and c) adding the frequency dispersed...http://www.google.com/patents/US5859920?utm_source=gb-gplus-sharePatent US5859920 - Method for embedding digital information in an image
