Image Watermarking in DCT:an Embedding Strategy and Algorithm

Where should invisible image watermarks be embedded in DCT domain in order for the image watermarks to be invisible and robust?Though many papers in the literature agree that watermarks should be embedded in perceptually significant components,DC components are explicitly excluded from watermark embedding.In this paper,a new embedding strategy and an algorithm applying the strategy for watermarking in DCT domain is proposed.Based on a quantitative analysis on magnitude of DCT components,we argue that more robustness can be achieved if watermarks are embedded in DC components since DC components have much larger perceptual capacity than any AC components.Applying this embedding strategy,an adaptive watermarking algorithm incorporating the feature of visual masking of human vision system is presented.Experimental results demonstrate that the embedding strategy is effective and the invisible watermarks thus generated are very robust.