Novel gray-scale watermarking algorithm based on QFT

This paper proposes a novel algorithm of embedding gray-scale watermark image into an RGB host image based on the Quaternion Fourier Transform (QFT). The R, G, B color components are represented respectively by the three imaginary parts of a pure imaginary quaternion and the gray-scale watermark image is inserted into the real part of the carrier image which is transformed by the QFFT. By using the symmetrical characteristic of the real part, we achieve the insertion of the gray-scale watermark image without lose. Experiment results show that the watermarked image with this method has the biggest imperceptibility with the best PSNR when compared with other gray-scale watermarking schemes.