Abstract: Considering the file size increase and visual distortion of the JPEG image with secret data, a reversible data hiding algorithm of JPEG images based on distortion-extension cost is proposed. Histogram shifting is used to realize reversible embedding of secret data, focusing on how to adaptively select embedding frequency and image block according to embedding capacity, so as to minimize the visual distortion and file size increase of JPEG image with secret data. This paper discusses and analyzes the rationality of determining the frequency embedding sequence by simulating the unit increase of file size of different frequencies, and determining the image block embedding sequence by the number of zero alternating current coefficients and smoothness of the image block. When embedding the data, the frequency of the smaller unit increase of file size and the smoother image block are preferred; and the unit increase of file size and the unit distortion-increase ratio are defined as quantitative evaluation indicators of algorithm file expansion, the relationship of visual quality and file expansion, respectively. Experimental results demonstrate that compared with the latest similar algorithms, the proposed algorithm can achieve a better balance between the increase of file size of the JPEG image with secret data and the visual quality, and reduce the increase of file size of the JPEG image with secret data, and the average of unit increase of file size under the same embed capacity has been reduced by 0.15~0.25.

Key words: reversible data hiding, JPEG images, histogram shifting, file size increase, visual distortion