[vtkusers] Changing level/window in LUT for ImageSlice: Unwanted clipping effects

[David Gobbi]

I've discovered more about this issue.  The Above/Below colors will work if
you call SetNumberOfColors after turning them on:

table->SetBelowRangeColor(1,0,0,1);
table->SetAboveRangeColor(0,1,0,1);
table->UseAboveRangeColorOn();
table->UseBelowRangeColorOn();
table->SetNumberOfColors(256);

I'm still investigating to see why this happens.

 - David


On Thu, Feb 2, 2017 at 7:20 AM, David Gobbi <david.gobbi at gmail.com> wrote:

>
>
> Hi Sophonet,
>
> I have confirmed that what you report is true: the vtkImageResliceMapper
> (and vtkImageSliceMapper) seem to ignore the AboveRangeColor and the
> BelowRangeColor.  This is also true for the current VTK master branch.  My
> current theory is that the mapper clamps the scalars to the range before
> they go through the lookup table.  Hopefully I'll have a fix for this soon.
>
> As a workaround (a inefficient workaround), you can use
> vtkImageMapToColors to apply the lookup table to the image before it goes
> to the mapper.
>
>  - David
>
>
> On Thu, Feb 2, 2017 at 5:10 AM, Sophonet <vtk12af6bc42 at kant.sophonet.de>
> wrote:
>
>> Dear list,
>>
>> for displaying images, I am using vtkImageResliceMapper. For changing the
>> colormap, I set a dedicated color map to the imageSlice's property (which
>> is a vtkLookupTable) and tell to use its scalar range:
>>
>> colorMap_->SetNumberOfTableValues(256);
>> colorMap_->SetRange(0, 1);
>>
>> imageProperty_->SetLookupTable(colorMap_);
>> imageProperty_->UseLookupTableScalarRangeOn();
>>
>>
>> Now, when changing level/window interactively with the mouse, I am
>> setting the range in the colorMap via
>>
>> double minmax[2];
>> // set values of minmax correctly
>> colorMap_->SetRange(minmax);
>>
>> The changes are displayed correctly - however, areas in which original
>> scalars of the image are clipped, the resulting color is displayed as
>> transparent. However, I would like to display the maximum / minimum value
>> in the color table.
>>
>> I have tried using colorMap_->SetAboveRangeColor() and
>> colorMap_->SetAboveRangeColorOn() (likewise for ...BelowRange...), with
>> no apparent effect.
>>
>> Any advice?
>>
>> I am using VTK 7.1.0.
>>
>> Thanks,
>>
>>      Sophonet
>>
>
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