DFT Based Coefficient Exchange Digital Image Watermarking

In this paper, a Discrete Fourier transform (DFT) based image watermarking scheme is proposed. The original cover image is divided into non-overlapping blocks of 8X8 and DFT is applied in each block and coefficient exchange is performed in the magnitude of the DFT block. Two coefficient is selected from each magnitude block to encode the binary watermark. The scheme encodes one bit of information in each 8X8 image block by confirming the difference between the two coefficients is positive then 1 is encoded and to encode zero the coefficients are exchanged. In the extraction of the watermark, the original image is not required. Using the StirMark benchmark tools, the proposed scheme is found to be robust against some of the common watermarking attacks like JPEG compression, affine transform and some of the common image processing attacks.