Fixes issue #12812. Using `util::interpolationFactor` handles the case where inputLevels.min == inputLevels.max, so it returns an interpolation factor of "0" instead of dividing by 0.
Fixes issue #12812. Using `util::interpolationFactor` handles the case where inputLevels.min == inputLevels.max, so it returns an interpolation factor of "0" instead of dividing by 0.