Combinational image watermarking in the spatial and frequency domains

In order to provide more watermarks and to minimize the distortion of the watermarked image, a novel technique using the combinational spatial and frequency domains is presented in this paper. The splitting of the watermark image into two parts, respectively, for spatial and frequency insertion relies on the user's preference and data importance. Experimental results provide the comparisons when different sized watermarks are embedded into a grayscale image. The proposed combinational image watermarking possesses the following advantages. More watermark data can be inserted into the host image, so that the capacity is increased. The splitting of the watermark into two parts makes the degree of protection double. The splitting strategy can be designed even more complicated to be unable to compose. Furthermore, to enhance robustness, a random permutation of the watermark is used to defeat the attacks of signal processing, such as image crops.