Image watermarking based on the two dimensional fully fledged fractional discrete fourier transform of type IV

An image watermarking technique is presented based on the two-dimensional fractional discrete Fourier transform of type IV (2D-FDFT-IV). The binary watermark image is first randomized by calling two functions in the NAG toolbox for Matlab with the objective of the pseudorandom permutation of the indices of the vector formed by the concatenation of the columns of the matrix representation of the watermark. Next a scaled and balanced version of the randomized watermark is added to the transformed input image. Finally the inverse transform is applied for producing the watermarked image. In order to assess the imperceptibility of the watermark, the peak signal to noise ratio (PSNR) is computed versus the relative scale factor employed in inserting the watermark. The experimental results show that adopting the fully-fledged definition of the fractional transform leads to higher PSNR than adopting the simple definition.