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tickbox var: $interpolatelutflag -- for color LUT's
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default: 1 (TRUE)

If the "intp" tickbox (near upper right) is
ticked, r,g,b's for val's in between color lookup
table entries (in e.g., $iscandir/scripts/*.lut)
are interpolated.

If not ticked, colors are constant until val
reaches next highest entry.

For real-valued LUT's, see "bot" tick to control
whether the color LUT val entry sets bottom edge
or center of color, and "sym" tick to determine
whether (s)fthresh and (s)fmid cut into color
scale from symmetrically in both directions from
zero, or just from the bottom.

See help for "lut:" entry for more details.
