  Code mapping (CM) is an efficient technique for reversible data hiding (RDH)
in JPEG images, which embeds data by constructing a mapping relationship
between the used and unused codes in the JPEG bitstream. This study presents a
new framework for designing a CM-based RDH method. First, a new code mapping
strategy is proposed to suppress file size expansion and improve applicability.
Based on our proposed strategy, the mapped codes are redefined by creating a
new Huffman table rather than selecting them from the unused codes in the
original Huffman table. The critical issue of designing the CM-based RDH
method, that is, constructing code mapping, is converted into a combinatorial
optimization problem. This study proposes a novel CM-based RDH method that
utilizes a genetic algorithm (GA). The experimental results demonstrate that
the proposed method achieves a high embedding capacity with no signal
distortion while suppressing file size expansion.
