[vtkusers] greyscale/color

[Chunyan Jiang]

Dear VTK friends,
I import the greyscale image data from memery to vtkImageImport, then
transform the vtkImageImport to vtkStructuredPoints by
vtkImageToStructuredPoints. After that I use vtkVolumeRayCastMapper to
render the volume. It works now, however, the greyscale image changes to
color image. How can I render grey image? I attach the code below. Is there
something wrong? Any help is appreciated.

Code:
	vtkImageImport *importer = vtkImageImport::New();
	importer->SetWholeExtent(1,dimensions[0],1,dimensions[1],1,dimensions[2]);
	importer->SetDataExtentToWholeExtent();

	importer->SetDataScalarTypeToUnsignedChar();

	importer->SetDataOrigin(0,0,0);
    importer->SetDataSpacing(1,1,1);
	importer->SetImportVoidPointer(data);//data is unsigned char* that storing
greyscale images data

	vtkStructuredPoints* structPts= vtkStructuredPoints::New();
	vtkImageToStructuredPoints* its=vtkImageToStructuredPoints::New();
	its->SetInput(importer->GetOutput());
	structPts=its->GetOutput();



// Create transfer mapping scalar value to opacity
	vtkPiecewiseFunction *opacityTransferFunction =
vtkPiecewiseFunction::New();
    opacityTransferFunction->AddPoint(20, 0.0);
    opacityTransferFunction->AddPoint(255, 0.2);

// Create transfer mapping scalar value to color
	vtkColorTransferFunction *colorTransferFunction =
vtkColorTransferFunction::New();
    colorTransferFunction->AddRGBPoint(0.0, 0.0, 0.0, 0.0);
    colorTransferFunction->AddRGBPoint(64.0, 1.0, 0.0, 0.0);
    colorTransferFunction->AddRGBPoint(128.0, 0.0, 0.0, 1.0);
    colorTransferFunction->AddRGBPoint(192.0, 0.0, 1.0, 0.0);
    colorTransferFunction->AddRGBPoint(255.0, 0.0, 0.2, 0.0);

// The property describes how the data will look
	vtkVolumeProperty *volumeProperty = vtkVolumeProperty::New();
    volumeProperty->SetColor(colorTransferFunction);
    volumeProperty->SetScalarOpacity(opacityTransferFunction);

// The mapper / ray cast function know how to render the data
	vtkVolumeRayCastCompositeFunction *compositeFunction=
vtkVolumeRayCastCompositeFunction::New();
	vtkVolumeRayCastMapper *volumeMapper=vtkVolumeRayCastMapper::New();
    volumeMapper->SetVolumeRayCastFunction(compositeFunction);

    volumeMapper->SetInput(structPts);//sp reader->GetOutput()

// The volume holds the mapper and the property and can be used to
position/orient the volume
	vtkVolume *volume = vtkVolume::New();
    volume->SetMapper(volumeMapper);
    volume->SetProperty(volumeProperty);


	renderer->AddActor(volume);

  // interact with data
  renWin->Render();

***********************************************************************
Chunyan Jiang, Dipl.-Inform.,
Institut for Telematic
Bahnhofstrasse 30-32, D-54292 Trier, Germany
Phone: (+49) (0)651-97551-34
Fax: (+49) (0)651-97551-12
***********************************************************************