Robust Color Image Watermarking Schemes in the Wavelet Domain

In this paper, two approaches for color image watermarking in the wavelet domain are proposed. The first approach utilizes only the chrominance content of the color image for watermarking after performing a single level DWT (Discrete Wavelet Transform) decomposition and hence named as DWTC whereas the second approach utilizes both the luminance and chrominance content for watermarking and hence termed as DWTLC. Watermark which is a logo is scrambled before embedding to increase its robustness. Watermarking is done on the approximation band coefficients chosen randomly by a function in Lab space. Both the proposed approaches result in watermarked images of high quality. The robustness of both the approaches is verified by the conduct of various attacks on the watermarked images and is compared with an existing SCDFT based approach and a DWT based approach. Experimental results show that DWTC is robust to non geometric attacks like filtering, blurring, sharpening, histogram equalization, JPEG compression and to geometric attacks like additive noise and scaling. DWTLC watermarking also shows robustness to all the above attacks. Further, both the approaches resist collusion attack even with a minimum number of colluders and with increasing number of colluders there is much distortion in the visual quality of the colluded images.