A reversible data hiding scheme for JPEG images by doubling small quantized AC coefficients

Abstract

Reversible data hiding for Joint Photographic Experts Group (JPEG) images has become popular in recent years, since JPEG images are widely used in practical applications. An improved reversible data hiding (RDH) method for JPEG images based on Huang et al.’s method is proposed. Huang et al. embedded data into discrete cosine transform (DCT) coefficients with values 1 and − 1 (i.e., the selected coefficients) using histogram shifting. After analyzing the statistical properties of quantized DCT coefficient blocks of the JPEG images, it was concluded that the vast majority of blocks have no alternating current (AC) coefficients with values in (3, −3, 4, −4), especially when the quality factor (QF) is low. For these blocks, we propose a method which extends the selected coefficients with values in (1, −1) to values in (1, −1, 2, −2), then embeds secret data into the selected coefficients by doubling them, while keeping the unselected coefficients unchanged. The extended method can improve the embedding capacity as well as the image quality. For the other blocks, Huang’s method is still applied. Experimental results verify that the proposed scheme can achieve higher embedding capacity, while maintaining a similar image quality and file size as other schemes did.