A DUAL TECHNIQUE FOR WATERMARKING COLOR DIGITAL IMAGES

The main requirements of a viable watermarking algorithm are: maintaining the host image quality and achieving a very high robustness to any kind of attacks for the introduced markup. In this paper, the authors propose a dual watermarking method. It combines a spatial watermarking technique with a frequency based technique. The two used methods have complementary results for image resistance to attacks. Since both watermarks are embedded in a different portion of the image coefficients, they do not interfere and the image quality is preserved. The resulting double watermarked image is extremely robust with respect to a wide range of attacks, including geometrical and non-geometrical transformations.