Patent ID: 6404899
Filing Date: 2002-06-11
Classification: G06T

Abstract:
A computer-implemented method for embedding data in a digital image that is used to authenticate the image, comprising the steps of:a) dividing said image into groups of M rectilinear blocks; b) calculating a property value of each said block; c) defining a mapping function that maps said property value of each said block onto a 0 or a 1 bit; d) embedding said 0 or 1 bit associated to each said block in accordance with the following steps, with a variable L=(a1âˆ’b1) when |a1âˆ’b1|&lE;d, where a1 is a number of microblocks with a first property value equal to a pre-specified lower bound value and having an inherently embedded bit opposite of a bit to be embedded, b1 is a number of microblocks with a second property value equal to a pre-specified upper bound value and having an inherently embedded bit opposite of a bit to be embedded, d is a number of microblocks with a property value between said pre-specified lower bound value and said pre-specified upper bound value and having an inherently embedded bit opposite of a bit to be embedded, I is a macroaverage value, I1 is a quantized macroaverage value, &ggr; is a macroblock property value interval, &Dgr; is an amount by which a change in the microblock property value will not exceed, and D is a set of microblocks with a property value between said pre-specified lower value and said pre-specified upper value and having an inherently embedded bit opposite of a bit to be embedded: i) increasing a1's by &Dgr;; ii) decreasing b1's by &Dgr;; iii) increasing a property value associated with each of |L| microblocks of D by &Dgr; when L<0; iv) decreasing said property value associated with each of |L| microblocks of D by &Dgr; when L&gE;0; and v) adjusting the remaining D microblocks.