Local watermarks based on Krawtchouk moments

This paper proposes a new image watermarking scheme using the set of Krawtchouk moments. The watermark is constructed as an independent identically distributed (i.i.d.) Gaussian random vector that is imperceptibly inserted in a spread-spectrum-like fashion into the perceptually significant Krawtchouk moments of the image. Interestingly, watermarks based on Krawtchouk moments are local, that is, the watermark affects only a selected portion of the image, the position of which can be decided by user. This, in effect, permits the watermark to be embedded at the portion of the image which is most significant information-wise. And this also means that the watermark is especially robust to cropping. Experimental results are provided to support these claims.