Adaptive post-filtering of JPEG compressed images considering compressed domain lossless data hiding

In this paper, we propose a new postprocessing algorithm for JPEG compressed images considering a compressed domain lossless data hiding scheme. The conventional compressed domain lossless data hiding scheme can embed information bits into the bitstream, while maintaining the file size and JPEG compatibility. As a new application of the conventional scheme, we design an algorithm of embedding filter coefficients in the bitstream, such that the embedded filter can be used to enhance the quality of the decoded image. To this end, a Wiener filter is estimated between the original and decoded images, and the coefficients are embedded into the JPEG bitstream. Moreover, the size, symmetry, and precision of the filter and the number of filters are determined under the constraint of embeddable bits. The proposed JPEG decoder extracts the filter coefficients from the bitstream and enhances the quality of the decoded image by applying the Wiener filter. The proposed algorithm can also work with conventional JPEG postprocessing algorithms, so that the performance of such conventional algorithms can be further improved.