Reversible watermarking based on multiple prediction modes and adaptive watermark embedding

A new reversible watermark scheme based on multiple prediction modes and adaptive watermark embedding is presented. Six prediction modes fully exploiting strong correlation between any pixel and its surrounding pixels, are designed in this paper. Under any prediction mode, each to-be-predicted pixel must be surrounded by several pixels (they constitute a local neighborhood, and any modification to this neighborhood is not allowed in the embedding process). This neighborhood has three main applications. The first one is that when it is exploited to interpolate some to-be-predicted 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. The last one is that we can accurately evaluate the classification of watermarked pixels by analyzing the local complexity of their corresponding neighborhoods on the decoding side. Therefore, the payload can be largely increased as each to-be-predicted pixel in the smooth set can possibly carry more than 1 bit. Meanwhile, the embedding distortion is greatly controlled by embedding more bits into pixels belonging to smooth set and fewer bits into the others in complex set. Experimental results reveal the proposed method is effective.