An image-hiding method with high hiding capacity based on best-block matching and k-means clustering

This paper presents a novel image-hiding method that exhibits a high hiding capacity that allows the embedded important image to be larger than the cover image, a facility that is seldom described in the literature. In the proposed method, the entire important image is divided into many nonoverlapping blocks. For each block of the important image, a block-matching procedure is used to search for the best similar block from a series of numbered candidate blocks. The obtained indices of the best-matching blocks are encoded using Huffman coding scheme, and then recorded in the least-significant-bit planes of the cover image through a monoalphabetic transposition cipher. The proposed method exhibits the following advantages over existing methods: (1) a high hiding capacity such that the embedded important image can be larger than the cover image; (2) a stego-image with a high quality, which improves the secrecy of the hidden image; and (3) a small error between the extracted important image and the original important image indicating that the extracted important image is of acceptable quality.