[vtkusers] volume reslice problem
Andi2008
mail-andi at web.de
Fri Aug 8 08:52:05 EDT 2008
Hi,
thank you for the quick answer. I tried to implement that but i have
problems with the right settings and also the use of a look up table needs a
lot more memory. Is it normal? I change the code as follows. Can you please
take a look over?
vtkRenderer *vtk_Renderer = vtkRenderer::New();
vtkWin32OpenGLRenderWindow *vtk_Win32OpenGLWindow =
vtkWin32OpenGLRenderWindow::New();
vtk_Win32OpenGLWindow->AddRenderer(vtk_Renderer);
// m_vtkvolumedata is an vtkImageData object and contains the volume
double *spacing = pThis->m_vtkvolumedata->GetSpacing();
int extent[6];
pThis->m_vtkvolumedata->GetExtent(extent);
double range[2];
pThis->m_vtkvolumedata->GetScalarRange(range);
vtkLookupTable *vtk_lookuptable = vtkLookupTable::New();
vtk_lookuptable->SetRange(range[0], range[1]); // image intensity range
vtk_lookuptable->SetHueRange(0.0, 0.0);
vtk_lookuptable->SetValueRange(0.0, 1.0); // from black to white
vtk_lookuptable->SetSaturationRange(0.0, 0.0); // no color saturation
vtk_lookuptable->SetAlphaRange(1.0, 1.0);
vtk_lookuptable->SetNumberOfColors(pow((float)2, pThis->m_iGrayscale));
vtk_lookuptable->SetRampToLinear();
vtk_lookuptable->Build();
vtkImageMapToWindowLevelColors *vtk_color_mapper =
vtkImageMapToWindowLevelColors::New();
vtk_color_mapper->SetLookupTable(vtk_lookuptable);
vtk_color_mapper->SetInput(pThis->m_vtkvolumedata);
vtk_color_mapper->SetLevel(pThis->m_dLevel);
vtk_color_mapper->SetWindow(pThis->m_dWindow);
vtk_color_mapper->ReleaseDataFlagOn();
vtkImageReslice *vtkImageReslicer = vtkImageReslice::New();
vtkImageReslicer->SetInput(vtk_color_mapper->GetOutput());
vtkImageReslicer->SetOutputDimensionality(2);
vtkImageReslicer->SetInterpolationModeToLinear();
vtkImageReslicer->SetOutputSpacing(spacing);
vtkImageReslicer->ReleaseDataFlagOn();
vtkImageMapper *mapper = vtkImageMapper::New();
mapper->SetInput(vtkImageReslicer->GetOutput());
mapper->SetColorWindow(255.0);
mapper->SetColorLevel(127.5);
vtkActor2D *vtkactor = vtkActor2D::New();
vtkactor->SetMapper(mapper);
vtkTransform *vtk_slicetransform = vtkTransform::New();
vtk_Renderer->AddActor(vtkactor);
vtk_Renderer->ResetCamera();
vtk_Renderer->GetActiveCamera()->ParallelProjectionOn();
Thanks a lot
Andi
David Gobbi-3 wrote:
>
> Hi Andreas,
>
> By default, vtkImageReslice sets the "Background" value to zero.
> Depending on how the Window/Level are set, this might appear as grey
> in the rendered image.
>
> There is an easy fix for this. Add vtkImageMapToColors (or
> vtkImageMapToWindowLevelColors) in front of vtkImageReslice, instead
> of doing the Window/Level in the ImageMapper. For the ImageMapper,
> you will have to set ColorWindow(255.0) and ColorLevel(127.5) to
> properly render data that has already been window/leveled.
>
> When you create the vtkLookupTable for vtkImageMapToColors, make sure
> that you call this function:
>
> table->SetRampToLinear();
>
> By default, VTK uses an sigmoid ramp (i.e. S-curve) for its lookup
> tables, which you definitely do not want for medical images. So you
> have to make sure to set the lookup table's ramp to linear before you
> use it.
>
> David
>
>
> On Fri, Aug 8, 2008 at 5:33 AM, Andreas Brüning <mail-andi at web.de> wrote:
>> Hello,
>>
>> i am writing a program to reslice a volume(stacked CT images) in any
>> direction and angle. Therefore i choose a point in the volume where to
>> slice through and also angles in x-,y- and z direction to define gradient
>> of the reslicearea. I create a reslice matrix using vtkTransform and
>> reslice the volume with a vtkImagereslice object like described in the
>> medical examples in vtk. I would like to get the data of the resliced
>> image but i dont know where i can get this data.
>>
>> The following code shows my vtk pipeline:
>>
>>
>> vtkRenderer *vtk_Renderer = vtkRenderer::New();
>>
>> vtkWin32OpenGLRenderWindow *vtk_Win32OpenGLWindow =
>> vtkWin32OpenGLRenderWindow::New();
>> vtk_Win32OpenGLWindow->AddRenderer(vtk_Renderer);
>>
>> double *spacing = pThis->m_vtkvolumedata->GetSpacing();
>> int extent[6];
>> pThis->m_vtkvolumedata->GetExtent(extent);
>>
>> vtkImageReslice *vtkImageReslicer = vtkImageReslice::New();
>> vtkImageReslicer->SetInput(pThis->m_vtkvolumedata); //vtkImageData
>> comming from vtkImport
>> vtkImageReslicer->SetOutputDimensionality(2);
>> vtkImageReslicer->SetInterpolationModeToLinear();
>>
>>
>> vtkImageReslicer->SetOutputSpacing(spacing);
>> vtkImageReslicer->ReleaseDataFlagOn();
>>
>> vtkImageMapper *mapper = vtkImageMapper::New();
>> mapper->SetInput(vtkImageReslicer->GetOutput());
>> mapper->SetColorLevel(pThis->m_dLevel);
>> mapper->SetColorWindow(pThis->m_dWindow);
>>
>> vtkActor2D *vtkactor = vtkActor2D::New();
>> vtkactor->SetMapper(mapper);
>>
>> vtkTransform *vtk_slicetransform = vtkTransform::New();
>>
>> vtk_Renderer->AddActor(vtkactor);
>> vtk_Renderer->ResetCamera();
>> vtk_Renderer->GetActiveCamera()->ParallelProjectionOn();
>>
>>
>> The reslicing part looks like this:
>>
>> vtk_slicetransform->Identity();
>> vtk_slicetransform->Translate(pThis->m_pSliceCenter[0],
>> pThis->m_pSliceCenter[1], pThis->m_pSliceCenter[2]); //centerpoint for
>> reslicing
>>
>> vtk_slicetransform->RotateZ(pThis->m_dSliceAngle_z);
>> vtk_slicetransform->RotateX(pThis->m_dSliceAngle_x);
>> vtk_slicetransform->RotateY(pThis->m_dSliceAngle_y);
>>
>> vtkImageReslicer->SetResliceAxes(vtk_slicetransform->GetMatrix());
>>
>> vtkImageReslicer->UpdateInformation();
>>
>> vtk_Win32OpenGLWindow->Render();
>>
>>
>>
>> When i run the program and change one angle i see gray areas around the
>> resultimage. I dont know where it comes from, but i guess they are
>> somehow representing the rest of the volume. Does anybody know how i can
>> only show the resultimage? When i rotate around x-axis and y-axis the
>> gray area get really big. I checked the OutputExtend of the resliceobject
>> after reslicing and at this time i get negative results the outcomming
>> extent is (0,-1,0,-1,0,-1).
>>
>>
>> By the way. I dont use any vtkInteractors in here because i want to run
>> this offscreen and only use everything to reslice the volume.
>>
>>
>> Thanks in advance
>> Andi
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