Patent ID: 7333244

Claim:
A method of embedding an image into two images, comprising: performing a digital halftoning process on a Cartesian product of color spaces to embed the image into the two images, wherein the digital halftoning process comprises an iterative isotopic halftoning process, wherein the iterative isotropic halftoning process comprises: for each iteration for each i for each j for each output vector o = (o 1 , o 2 , o 3 ) ∈ P replace Outimage k (i, j) with o k fork = 1, 2, 3, set ⁢ ⁢ Error ⁡ ( o ) = ∑ k = 1 3 ⁢ v k ⁢  L ⁡ ( Outimage k - A k ′ )  endfor find ⁢ ⁢ output ⁢ ⁢ vector ⁢ ⁢ o min = arg ⁢ ⁢ min o ∈ P ⁢ ⁢ Error ⁡ ( o ) set Outimage(i, j) = o min . endfor (j) endfor (i) wherein if Outimage has not changed between two iterations or maximum number of iterations reached, then exit the iterations loop, where: A 1 ′, A 2 ′ and A 3 ′ are input images; P comprises a set of output vectors; Output comprises A 1 ′ and A 2 ′ where (A 1 ,A 2 ,A 3 )=Outimage which resembles (A 1 ′, A 2 , A 3 ′); v i determines how strongly the error in each image is minimized; and L comprises a linear space-invariant model of a human vision system.