TW 497

Adhemar Bultheel
Digital watermarking of images in the fractional Fourier domain

Abstract

We describe the implementation of a watermark embedding technique for images using the discrete fractional Fourier transform. The idea is that a 2D discrete fractional Fourier transform of the image is computed. In this transform domain, a normal distributed random sequence with certain characteristics is used to modify the transform coefficients in the middle range of magnitude. Then the inverse transform is applied to give the watermarked image. The detection is based on performing the same transform operation. The watermark is recognized if there is a strong correlation with the embedded watermark. That is when the correlation is above some threshold.