The origin matlab code implements [1]. We translated the code from matlab to python version. The input is a RGB image, and the output is 686 dimension features.
[1] T. Pevny, P. Bas, and J. Fridrich, Steganalysis by Subtractive Pixel Adjacency Matrix IEEE Trans. on Info. Forensics and Security, vol. 5(2), pp. 215–224, 2010.
Source: http://dde.binghamton.edu/download/feature_extractors/
Update: the matlab file, spam686.m, is no longer available.