A digital watermarking algorithm for image based on fractional Fourier transform

A novel digital watermarking embedding and detecting algorithm for image is presented, which uses the chirp signal as a watermark and embeds in the fractional Fourier transform (FRFT) domain of the image, and the watermark position and the transform order are used as the encryption keys. With the help of the property of the impulse characteristic in the FRFT domain for chirp signal, the watermark can be detected conveniently. The experiments results have show that the proposed algorithm not only is of good imperceptibility and security and is very robust to JPEG compression and to noise attacks, but also can provide protection under the cropping and the filtering.