My scanner supports customisation of colour curve table. "scanimage" utility reports this option as
--red-gamma-table 0..255,...
Gamma-correction table for the red band.
--green-gamma-table 0..255,...
Gamma-correction table for the green band.
--blue-gamma-table 0..255,...
Gamma-correction table for the blue band.
It is an array of integers, SANE reports option size 1024. Alas, Python demands a single-value int/long option.

How can we support value tables?