Color Image Watermarking Using the Spatio-Chromatic Fourier Transform

In this paper, a color watermarking algorithm is proposed. The method encodes the chromatic content of a color image as CIE a*b* chromaticity coordinates whereas the achromatic content is encoded as CIE L tristimulus value. Color watermarks (yellow and blue) are embedded in the frequency domain of the chromatic channels by using the spatio-chromatic discrete Fourier transform (SCDFT). It first encodes a* and b* as complex values, followed by a single discrete Fourier transform. Watermark casting is performed by estimating the just-noticeable distortion (JND) of the images, to ensure watermark invisibility. The most interesting characteristics of the new scheme is the possibility of performing watermarking in the frequency domain of chromatic components