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

[David Gobbi]

Hi Sophonet,

Can you send the exact code that you use to set up the lookup table,
including the call to Build(), so that I can check locally?

 - David

On Thu, Feb 2, 2017 at 10:42 AM, Sophonet <vtk12af6bc42 at kant.sophonet.de>
wrote:

> Well, on my system your proposed change did not work, I still see
> transparent color when LUT clipping occurs, exactly as before. I have even
> copied your lines of your previous posting plus the Build() call below the
> SetRange() callback, in which I am doing level/windowing. Not sure why
> though - I might check again using the HEAD (I am on 7.1.0 release)
>
> - Sophonet
>
>
> Am 2017-02-02 18:08, schrieb David Gobbi:
>
>> Okay, here is a very simple work-around for this issue: Just call
>> Build() on the table after you have set all the other table
>> parameters.  Please let me know if this fixes the issue.
>>
>> I've submitted a fix for mapper so that it will call Build()
>> automatically.  I'm not sure why it didn't do this before.
>>
>>  - David
>>
>> On Thu, Feb 2, 2017 at 8:41 AM, David Gobbi <david.gobbi at gmail.com>
>> wrote:
>>
>> 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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