[vtkusers] Unexpected result when changing the window & level if a lookup table is assigned

[Roger Bramon Feixas]

Dear all,

I'm sending this issue to both GDCM and VTK mailing list because even
though we are currently using the GDCM implementation of
vtkImageMapToWindowLevelColors, it has the same behavior than VTKimplementation.

My question is related to how the window and level are applied when a
lookuptable is assigned. I prepared a video to illustrate it:
http://www.youtube.com/watch?v=PbQnWCBhpmw

Currently, when a lookup table is given, the scalars are mapped through the
table and then each output component is multiplied by (inputValue +
shift)*scale. Thus, a scalar value always has the same hue and only
the brightness changes depending on window and level values.

Our expected behavior is obtained by changing the range of the lookup table
taking into account the window and level values, and then mapping the
scalars through the table to obtain the output colors.

I think that the video clearly shows the difference.

I would like to know your opinion and I am also wondering what are the
cases where the current behavior is the desired behavior.

Many thanks!

Roger
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