A Robust Image Watermarking Based On Gradient VectorQuantization and Denoising Using Contourlet Transform

ABTRACT We propose a robust quantization-based image watermarking scheme, called the gradient direction watermarking (GDWM).This is based on the uniform quantization of the direction of gradient vectors. In GDWM, the watermark bits are embedded by quantizing the angles of significant gradient vectors at multiple wavelet scales. The proposed scheme has the following advantages: 1)Increased invisibility of the embedded watermark because the watermark is embedded in significant gradient vectors, 2) robustness to amplitude scaling attacks because the watermark is embedded in the angles of the gradient vectors, and 3) increased watermarking capacity as the scheme uses multiple-scale embedding.. This watermarking technique is more Robust tovarious sizes of watermark Images.we construct a discrete-domain multiresolution and multidirectional expansion using non-separable filter banks, in much the same way that wavelets were derived from filter banks. This construction results in a flexible mutiresolution, local, and directional image expansion using contour segments, and thus it is named the contourlettransform. The discrete contourlet transform has a fast iterated filter bank algorithm that requires order N operations for N-pixel images. Finally, we show simulation results using contourlet denoising method over wavelet. Keywords—ContourletTransform ,denoising, digital watermarking,gradientdirection quantization, wavelets.