Reversible Watermarking Based on Eight Improved Prediction Modes

A new reversible watermark scheme based on eight prediction modes is presented. In each of eight prediction modes, any modification to some pixels which account for one-fourth of all pixels is not allowed for a single embedding process. By employing smartly these unchanged pixels, each to-be-predicted pixel in any mode is guaranteed to be surrounded by several pixels which constitute a local neighborhood. Each neighborhood has two applications. The first one is that when it is exploited to interpolate its corresponding surrounded pixel, the noticeable improvement in prediction accuracy is obtained. The second one is that its variance is employed to determine which classification (i.e., smooth or complex set) its surrounded pixel belongs to. For any to-be-predicted pixel, the number of embedded bits is adaptively determined according to this pixel’s belonging. Experimental results reveal the proposed method is effective.