[vtkusers] vtkImageReslice and vtkImageViewer

[David Gobbi]

Hi Talita,

When reslice->SetOutputDimensionality(2) is used, the output of
vtkImageReslice contains only one slice.  That is why GetWholeZMax()
is returning zero.

To just change the axes without doing anything else to the image, use
SetOutputDimensionality(3) and do not set the "center" in the
resliceAxes.

    David



On Tue, Sep 23, 2008 at 10:16 PM, Talita Perciano
<talitaperciano at gmail.com> wrote:
> Hello,
>
> I'm trying to read DICOM image slices and to view them with a
> vtkImageViewer. The thing is that I want to change the axis before I view
> the slices, that is, if the slices are in axial direction I want to change
> it to coronal direction. I'm doing that using the a vtkImageReslice. The
> thing is that when I pass the DICOM reader directly to the vtkImageViewer
> things work fine. However, when I use first the vtkImageReslice and than
> pass it to the vtkImageViewer I can't view the slices anymore. It's strange
> because when I call GetWholeZMax it returns 0. Does anybody could help me?
> The code is attached.
>
> Thank you,
>
> Talita
>
> -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>         std::string strFolderPath = "/home/talita/Desktop/COMUNIX/Neck
> 1HEAD_NECK_PETCT/CT HEAD-NK 5.0 B30s";
>
>         vtkDICOMImageReader *reader = vtkDICOMImageReader::New();
>         reader->SetDirectoryName (strFolderPath.c_str());
>         reader->Update();
>
>     reader->SetDataScalarTypeToUnsignedShort();
>       reader->UpdateWholeExtent();
>
>       // Calculate the center of the volume
>       reader->GetOutput()->UpdateInformation();
>       int extent[6];
>       double spacing[3];
>       double origin[3];
>       reader->GetOutput()->GetWholeExtent(extent);
>       reader->GetOutput()->GetSpacing(spacing);
>       reader->GetOutput()->GetOrigin(origin);
>
>       double center[3];
>       center[0] = origin[0] + spacing[0] * 0.5 * (extent[0] + extent[1]);
>       center[1] = origin[1] + spacing[1] * 0.5 * (extent[2] + extent[3]);
>       center[2] = origin[2] + spacing[2] * 0.5 * (extent[4] + extent[5]);
>
>       // Matrices for axial, coronal, sagittal, oblique view orientations
>       static double axialElements[16] = {
>                1, 0, 0, 0,
>                0, 1, 0, 0,
>                0, 0, 1, 0,
>                0, 0, 0, 1 };
>
>       static double coronalElements[16] = {
>            1, 0, 0, 0,
>            0, 0, 1, 0,
>            0,-1, 0, 0,
>            0, 0, 0, 1 };
>
>       static double sagittalElements[16] = {
>            0, 0,-1, 0,
>            1, 0, 0, 0,
>            0,-1, 0, 0,
>            0, 0, 0, 1 };
>
>       //static double obliqueElements[16] = {
>       //         1, 0, 0, 0,
>       //         0, 0.866025, -0.5, 0,
>       //         0, 0.5, 0.866025, 0,
>       //         0, 0, 0, 1 };
>
>       // Set the slice orientation
>       vtkMatrix4x4 *resliceAxes = vtkMatrix4x4::New();
>       resliceAxes->DeepCopy(coronalElements);
>       // Set the point through which to slice
>       resliceAxes->SetElement(0, 3, center[0]);
>       resliceAxes->SetElement(1, 3, center[1]);
>       resliceAxes->SetElement(2, 3, center[2]);
>
>       // Extract a slice in the desired orientation
>       vtkImageReslice *reslice = vtkImageReslice::New();
>       reslice->SetInputConnection(reader->GetOutputPort());
>       reslice->SetOutputDimensionality(2);
>       reslice->SetResliceAxes(resliceAxes);
>       //reslice->SetInterpolationModeToNearestNeighbor();
>
>       // Create a greyscale lookup table
>       vtkLookupTable *table = vtkLookupTable::New();
>       table->SetRange(0, 2000); // image intensity range
>       table->SetValueRange(0.0, 1.0); // from black to white
>       table->SetSaturationRange(0.0, 0.0); // no color saturation
>       table->SetRampToLinear();
>       table->Build();
>
>       // Map the image through the lookup table
>       vtkImageMapToColors *color = vtkImageMapToColors::New();
>       color->SetLookupTable(table);
>       color->SetInputConnection(reslice->GetOutputPort());
>
>     vtkImageViewer *viewer = vtkImageViewer::New();
>
>     viewer->SetInput(color->GetOutput());
>     printf("\n%d\n",viewer->GetWholeZMax());
>     viewer->SetZSlice(35);
>     viewer->SetColorWindow(2000);
>     viewer->SetColorLevel(1000);
>     viewer->Render();
>
>
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