Reversible data hiding method and recovering method

The invention relates to a reversible data hiding method and a recovering method. The reversible data hiding method comprises a preprocessing step in which an original pixel-domain image is divided into blocks and the blocks are sorted according to the gray values, a marking step in which the sequence after sorting is detected and identified and feature-class blocks are marked, a watermark information embedding step in which watermark information is embedded into the feature-class blocks through a second embedding method, and an auxiliary information embedding step in which corresponding auxiliary information is embedded. According to the invention, on-demand watermark information embedding is realized, equal-maximum pixel redundancy in the image is fully exploited, 'one-position multi-bit embedding' is realized, and the information capacity is improved effectively. Meanwhile, seamless integration of a first embedding method and the second embedding method is achieved effectively.