ENH: Add opacity support for DiscretizableColorTransferFunction
requested to merge LucasGandelKitware/vtk:DiscretizableColorTransferFunction-Opacity-Support into master
Overridding the ScalarsToColors internal method "MapScalarsThroughTable2" to handle mapping of alpha values when using the MapScalarsThroughTable entry point. Previous work from 01b2767b was only supporting opacity mapping for the MapScalars entry point. Mapping of RGB values is still delegated to the superclass or the lookup table.