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

Roger Bramon Feixas rogerbramon at gmail.com
Tue Oct 1 06:51:13 EDT 2013

Dear folks,

We are strongly interested in knowing your opinion on the issue. If you
agree, we can discuss about the implementation, we would like to
collaborate to the project. We believe it is a nice improvement not only
for our own project.



On Fri, Sep 13, 2013 at 2:35 PM, Roger Bramon Feixas
<rogerbramon at gmail.com>wrote:

> 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
> lookup table 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 lookuptable 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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