Steganography: an algorithm for threshold based embedding

I am doing a little bit of research lately because steganography has become an interesting hobby of mine.

The first "real" algorithm that will make it into pepperpickle's feature set is "Threshold-based" as discussed in the following paper by Khan, Shah, Naeem et al.:
https://www.researchgate.net/publication/271207740_Threshold-based_Steganography_A_Novel_Technique_for_Improved_Payload_and_SNR

It is strikingly simple to implement and, according to the authors, improves the payload and Signal-to-Noise-Ratio - let's see :)

here is how it works:

Threshold-based embedding. I found no traces of steganography in this image.

I propose the following addition, though:
If a pixel is completely white (255, 255, 255) or black (0, 0, 0), leave it as it is to make steganalysis a little bit harder.