Patent ID: 6678390
Filing Date: 2004-01-13
Classification: G06T,H04N

Abstract:
A method for extracting an embedded binary message from a digital image, the embedded message being formed by convolution with a carrier, comprising the steps of:a) providing a message template indicating the relative locations of data in the embedded message, the relative locations of the data being such that the autocorrelation of the message template is strongly peaked at zero offset with substantially smaller sidelobes occurring at nonzero offset locations and further such that no bit location is closer to another bit location by less then three pixels and further arranged substantially along concentric circles or along a spiral pattern; b) correlating an arbitrary region of the digital image with the carrier to extract a cyclically shifted binary message from the digital image; c) taking the absolute value of the cyclically shifted message to form a positive valued cyclically shifted binary message; d) correlating the positive valued cyclically shifted binary message with the message template to form a shifted offset image having a peak amplitude representing the location of the message boundary; and e) employing the location of the message boundary to extract the hidden message.