[vtkusers] No LookupTable was set but input data is not VTK_UNSIGNED_CHAR

[Flaviu2]

David, I cannot thank you enough for your kindness.Yes, I post the code used for case without LUT:

    vtkDICOMReader* m_pDICOMReader = vtkDICOMReader::New();
    m_pDICOMReader->RemoveAllInputs();
    vtkDICOMApplyRescale* m_pRescale = vtkDICOMApplyRescale::New();
    m_pDICOMReader->SetFileNames(pFN); // all files from serie
    m_pDICOMReader->AutoRescaleOff();
    m_pDICOMReader->Update();
    m_pRescale->SetInputConnection(m_pDICOMReader->GetOutputPort());
    m_pRescale->Update();
    vtkImageReslice* m_pResliceAxial = vtkImageReslice::New();
    m_pResliceAxial->SetInputConnection(m_pRescale->GetOutputPort());
    vtkImageMapToColors* m_pColorAxial = vtkImageMapToColors::New();
    m_pColorAxial->SetInputConnection(m_pResliceAxial->GetOutputPort());
    vtkImageActor* m_pImageActor = vtkImageActor::New();
    // and then, forward, setup m_pColorAxial to an image actor:
    pImageActor->GetMapper()->SetInputConnection(m_pColorAxial->GetOutputPort());
    // and add image actor to a renderer
    m_pRenderer->AddActor(m_pImageActor);
In fact, I am using the same code, but I am not using vtkLookupTable at all ... I know, it is not quite ok, but it is the only way to have the original window level from the image ...
Flaviu.



 

    On Thursday, May 19, 2016 4:03 PM, David Gobbi <david.gobbi at gmail.com> wrote:
 

 I will try to answer your question, but I need to know more about your code first.  Can you post the code you used for the "Snapshot_without_LUT" image?  In particular, the screenshot has a Window/Level annotation (W: 80, L: 35), so show me how those values are used in the code.
On Thu, May 19, 2016 at 6:35 AM, Flaviu2 <flaviu2 at yahoo.com> wrote:

Hi David. Something strange is happen ... I had tried to set LUT as you said, but the image are still whiter than without LUT ... see attached images ...
And of course, I can not use vtkImageMapToColors without LUT, because the application is crashing ... is there a solution here ?
Flaviu.
 

    
 

 Hi Flaviu,
This is incorrect:
m_pLUTAxial->SetRange(dLevel, dWindow);

It should be something like this:
m_pLUTAxial->SetRange(dLevel - 0.5*dWindow, dLevel + 0.5*dWindow);
 - David

On Fri, May 13, 2016 at 1:22 AM, Flaviu2 <flaviu2 at yahoo.com> wrote:

This is a little pseudocode of the entire pipeline:
 vtkDICOMReader* m_pDICOMReader = vtkDICOMReader::New(); m_pDICOMReader->RemoveAllInputs(); vtkDICOMApplyRescale* m_pRescale = vtkDICOMApplyRescale::New(); m_pDICOMReader->SetFileNames(pFN); // all files from serie m_pDICOMReader->AutoRescaleOff(); m_pDICOMReader->Update(); m_pRescale->SetInputConnection(m_pDICOMReader->GetOutputPort()); m_pRescale->Update(); vtkImageReslice* m_pResliceAxial = vtkImageReslice::New(); m_pResliceAxial->SetInputConnection(m_pRescale->GetOutputPort()); vtkLookupTable* m_pLUTAxial = vtkLookupTable::New(); m_pLUTAxial->SetValueRange(0.0, 1.0); // from black to white m_pLUTAxial->SetSaturationRange(0.0, 0.0); // no color saturation vtkDICOMMetaData* pMeta = m_pDICOMReader->GetMetaData(); const vtkDICOMValue& window = pMeta->GetAttributeValue(DC::WindowWidth); const vtkDICOMValue& level = pMeta->GetAttributeValue(DC::WindowCenter); double dWindow = window.AsDouble(); double dLevel = level.AsDouble(); m_pLUTAxial->SetRange(dLevel, dWindow); // image intensity range m_pLUTAxial->SetRampToLinear(); m_pLUTAxial->Build(); vtkImageMapToColors* m_pColorAxial = vtkImageMapToColors::New(); m_pColorAxial->SetLookupTable(m_pLUTAxial); m_pColorAxial->SetInputConnection(m_pResliceAxial->GetOutputPort()); vtkImageActor* m_pImageActor = vtkImageActor::New(); // and then, forward, setup m_pColorAxial to an image actor: pImageActor->GetMapper()->SetInputConnection(m_pColorAxial->GetOutputPort()); // and add image actor to a renderer m_pRenderer->AddActor(m_pImageActor);

I had taken "Window center" and "Window width" and put them as range on lookuptable ... the image are little dark, and is not like the original (without setup lookup table looks good, but I get those warning like in post subject) ... might not understand well what you said about this range, but I am feel I am not far from solve this problem ... can you guide me a little bit ?
Flaviu.


 

 Since you're already using vtk-dicom, you can use vtkDICOMApplyRescaleto convert your CT image to Hounsfield units (if you use this filter, you shouldalso call AutoRescaleOff() on the reader).
After the image has been converted to Hounsfield units, you can use the"Window Center" and "Window Width" presets that are stored in the metadata to set the range for the lookup table.
However, I usually ignore these presets, and instead use the VTK classvtkImageHistogramStatistics to compute the range.  Its GetAutoRange()computes a range by doing some simple histogram analysis.
If you enjoy doing a lot of reading, the relevant parts the DICOM standardare here:http://dicom.nema.org/MEDICAL/Dicom/current/output/chtml/part03/sect_C.11.html
After the image goes through vtkImageMapToColors, how are yourendering it?
 - David

   



   

   



  
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