Among them, both DE and HS attract much attention due to their easy operation and high quality of stego-image. Initial DE based scheme [8] calculates the difference between two adjacent pixels and then doubles (expands) the value to vacate its LSB to hide 1-bit secret data. To further exploit image correlation, DE is extended on prediction errors, and called as prediction-error expansion (PEE) [9]–[15]. Later, several improved techniques, such as selection techniques [12], [16], location map reduction [14], are proposed on PEE. Recently, in [23] and [42], the ideal that DE/PEE scheme could be regarded as a special case of HS is proposed. Therefore, we concentrates on the HS based scheme in this paper.