interpolatorRandomWalk maxDistance

[Fil]

Allows to select a region that contains high value samples:

before	after

The difficulty lies in choosing the value for points that are too far: should it be 0, or something else? (NaN and -Infinity don't work in conjunction with blur2 , but maybe it's blur2 that should be upgraded).

[Fil]

linked to (or identical to?) #1431.