A further study on steganalysis of LSB matching by calibration

In this paper, based on a careful investigation on the calibration (downsample) technique, we improve two detectors for detecting LSB matching: calibrated HCF COM and calibrated adjacency HCF COM. Instead of using the COM (center of mass) of the HCF (histogram characteristic function), we consider the ratio of the histogram´s DFT coefficients of the image to the corresponding coefficients of the down-sampled image. Moreover, we propose to down-sample only for non-oscillating pixels. With a same level of computational complexity, the new detectors thus obtained are better than the old ones, especially for uncompressed images.