More compressible location map for reversible watermarking using expansion embedding

A location map is frequently employed in reversible watermarking to distinguish the watermarked pixels. It is usually compressed by arithmetic coding before being concealed. The size of the compressed location map influences the payload greatly. Proposed is a novel principle of creating the location map, which increases the compression ratio of the location map and achieves higher payload at high peak signal-to-noise ratio. Experimental results show the proposal is effective.