Difference-expansion based reversible and visible image watermarking scheme

A reversible image watermarking scheme recovers the original cover image after extracting the embedded watermarks. A visible image watermarking scheme embeds watermarks to create a visible watermark effect on the cover image. A general reversible image watermarking scheme embeds invisible watermarks. This paper presents a reversible and visible image watermarking scheme that uses a conventional difference-expansion method. The cover image is first segmented to non-overlapped k×k blocks. Each block is then applied to two watermarking schemes; a difference-expansion based invisible watermarking scheme and a visible watermarking scheme to embed one watermark bit. Exceeding numbers, larger than 255 or smaller than 0, generated from the difference-expansion method require being recorded for a lossless recovery. Experimental results show that the proposed scheme embeds visible watermarks with few recorded exceeding numbers. However, not recording any exceeding numbers still results in a high similarity of extracted watermark image and good quality of recovered cover image.