Make TF points relative to houndsfield scale (for DICOM)?

[mlavik1]

The TF points have density values between 0.0 and 1.0. This is relative to the value range of the dataset, and the corresponding absolute density value will then depend on the minimum and maximum data value.

However, for DICOM we typically deal with Hounsfield values. To make sure the same transfer function looks the same on all DICOM datasets, we should make the density values relative to the Hounsfield Unit scale (-1024 to 3071).

NOTE: Do we have to read the Rescale type, as well as rescale slope/intercept, or does SimpleITK already do that? (and what about OpenDICOM?)