Introduce jump probability for grey scale images

[TomTranter]

It is possible to assign a probability that a movement will take place based on the grey scale value of an image. This is useful for tomography data for materials with variable microporosity that is below the resolution of the image. Whether the grey scale value can always be linked to microporosity is another matter as different materials attenuate differently so composite materials may require some additional segmentation. This concept is proven in the literature and would be useful to implement. Fiedler et. al. have published a few papers on this
https://www.sciencedirect.com/science/article/pii/S0167577X08008446