Investigate colour/intensity normalisation

[chengsoonong]

No description provided.

[MatthewJA]

This could be arbitrarily hard; could we mark it wontfix?

[chengsoonong]

My thought for this issue is to do some non-linear squashing (something like a sigmoid) and that should do the most of the required job.

I recall @jbanfield suggesting something like asinh.

[MatthewJA]

Alright, let's use asinh; I recall seeing a source saying that asinh has been shown to work well on inputs to these things.

[MatthewJA]

I can't seem to get fitting logistic regression to actually terminate with an asinh stretch (working on it...) but for random forests the performance is improved a fair bit with such a stretch.