[vtkusers] Transparency of binary segmentation mask (ImageActor2D + LUT)

Sun Mar 29 13:34:26 EDT 2009

vtkImageBlend is intended for this scenario. You could pass your input image
and the overlay segmentation. Blend them and assign approriate colors
through the blender.

On Fri, Mar 27, 2009 at 1:49 PM, Charlotte Curtis <c.f.curtis at gmail.com>wrote:

> Just a follow-up in case anyone else has this problem: it seems that
> vtkActor2D cannot layer with transparency.  Switching to a
> vtkImageActor solved the problem, although introducing a few others
> (like requiring the data to be unsigned char, meaning some of the
> intensity data of the image must be discarded).
>
> Charlotte
>
> On Tue, Mar 24, 2009 at 1:14 PM, Charlotte Curtis <c.f.curtis at gmail.com>
> wrote:
> >
> > Hi Jeff, thanks for the reply.
> >
> > I'm not sure what you mean by exactly the same location - it's true
> > that they are at the same xy location, but they are on different
> > layers, or at least that's what I'd like them to be doing.  I tried
> > changing the Z location with Mapper->SetZSlice, but this just resulted
> > in the entire segmentation mask becoming opaque (including the values
> > that are mapped through the LUT to an alpha of zero).
> >
> > I tried setting the opacity of both images to 0.5 as you suggested
> > (using actor->GetProperty()->SetOpacity()), and this didn't seem to
> > change anything.  Even setting the opacity to zero results in opaque
> > images, although if I set the alpha of my LUT values to zero the image
> > does indeed disappear.
> >
> > If I print various values to std::cout, everything seems to be in
> > order - for example, overlayRenderer->Transparent() returns 1,
> > overlayActor->GetProperty()->GetOpacity() returns whatever I set it to
> > (0.5), etc.  I thought perhaps there was something wrong with my
> > system graphics/opengl setup, but if I build and run the "medical 3"
> > example I do get a transparent volume.  Reading through the code in
> > that file, the only difference I could see was that it uses a single
> > renderer with multiple actors so I tried that as well, but nothing
> > seemed to change.
> >
> > Thanks again for the help,
> >
> > Charlotte
> >
> > On Tue, Mar 24, 2009 at 8:09 AM, Jeff Baumes <jeff.baumes at kitware.com>
> wrote:
> > > It looks like the images are displayed at exactly the same location? I
> > > believe the image mapper maps a texture to a quad, so perhaps you have
> > > conflicting geometry. The other thing I would try is to set the
> > > opacity of both images to less than 1.0 (like 0.9 and 0.5), so that
> > > they are both rendered in the same render pass. VTK first renders any
> > > opaque geometry, then renders translucent geometry, so that may be why
> > > it gets obscured.
> > >
> > > Jeff
> > >
> > > On Mon, Mar 23, 2009 at 9:38 PM, Charlotte Curtis <
> c.f.curtis at gmail.com> wrote:
> > >> Hi all,
> > >>
> > >> I've got a couple of images displayed on top of each other, one a 2D
> > >> medical image, and the other a binary segmentation mask.  They each
> > >> have their own image actors and renderers, and I created a lookup
> > >> table for the segmentation mask in the hopes that it would let me
> > >> render the mask as semi-transparent colours.  Right now I've got two
> > >> values in the LUT (corresponding to the image values of 0 and 1), and
> > >> I can change the colours, but the transparency is binary - if I set
> > >> the alpha value to 0, it doesn't display, but if it's anything else
> > >> (even 0.001) then the mask is completely opaque.
> > >>
> > >> I've also tried changing the opacity of the actor
> > >> (actor->GetProperty->SetOpacity()), but this doesn't seem to do
> > >> anything, although when I print out the value of the actor's opacity
> > >> it thinks that it is set correctly.
> > >>
> > >> Perhaps my window/levels are wrong?  I'm kind of at a loss.  Apologies
> > >> if this has been asked (seems like a common problem, but I couldn't
> > >> find a solution so far).  Thanks,
> > >>
> > >> Charlotte
> > >>
> > >> // Create the common components for the image viewer
> > >> vtkRenderWindow* renWin = vtkRenderWindow::New();
> > >> vtkRenderWindowInteractor* interactor =
> renWin->MakeRenderWindowInteractor();
> > >> interactor->SetRenderWindow( renWin );
> > >>
> > >> // Create the components for the image display
> > >> vtkRenderer* imageRenderer = vtkRenderer::New();
> > >> vtkActor2D* imageActor = vtkActor2D::New();
> > >> vtkImageMapper* imageMapper = vtkImageMapper::New();
> > >>
> > >> // Set the values and connect them together
> > >> imageMapper->SetColorWindow( 1024 );
> > >> imageMapper->SetColorLevel( 512 );
> > >> imageMapper->SetInput( connector->GetOutput() );
> > >> imageActor->SetMapper( imageMapper );
> > >> imageRenderer->AddActor( imageActor );
> > >>
> > >> // Create the components for the mask layer
> > >> vtkRenderer* overlayRenderer = vtkRenderer::New();
> > >> vtkActor2D* overlayActor = vtkActor2D::New();
> > >> vtkImageMapper* overlayMapper = vtkImageMapper::New();
> > >> vtkLookupTable* overlayLUT = vtkLookupTable::New();
> > >> vtkImageMapToColors* colourMapper = vtkImageMapToColors::New();
> > >>
> > >> /************************* This is the part that's not behaving
> > >> ********************************/
> > >> // set properties of the various overlay components
> > >> //overlayActor->GetProperty()->SetOpacity( 0.5 ); this doesn't seem to
> > >> do anything
> > >> double outsideColour[4] = {1.0, 0, 0, 0.5};  // This one shows up as
> > >> completely opaque red.
> > >> double insideColour[4] = {1.0, 1.0, 1.0, 0}; // This one doesn't show,
> > >> which is correct.
> > >> overlayLUT->SetNumberOfTableValues(2);
> > >> overlayLUT->SetTableRange(0, 1);
> > >> overlayLUT->SetTableValue( 0, outsideColour );
> > >> overlayLUT->SetTableValue( 1, insideColour );
> > >> overlayLUT->Build();
> > >> overlayMapper->SetColorLevel( 0.5 );
> > >> overlayMapper->SetColorWindow( 0.5 );
> > >>
> > >> // Connect the overlay stuff together
> > >> colourMapper->SetLookupTable( overlayLUT );
> > >> colourMapper->SetInput( binConnector->GetOutput() );
> > >> overlayMapper->SetInput( colourMapper->GetOutput() );
> > >> overlayActor->SetMapper( overlayMapper );
> > >> overlayRenderer->AddActor( overlayActor );
> > >>
> > >> // Connect everything together
> > >> renWin->SetSize( size[0], size[1] );
> > >> renWin->SetNumberOfLayers( 2 );
> > >> renWin->AddRenderer( imageRenderer );
> > >> renWin->AddRenderer( overlayRenderer );
> > >> imageRenderer->SetLayer( 0 );
> > >> overlayRenderer->SetLayer( 1 );
> > >>
> > >> // Look at the pretty picture!
> > >> renWin->Render();
> > >> interactor->Start();
> > >> _______________________________________________
> > >> Powered by www.kitware.com
> > >>
> > >> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
> > >>
> > >> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
> > >>
> > >> Follow this link to subscribe/unsubscribe:
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> > >>
> > >
> > >
> > >
> > > --
> > > Jeff Baumes, Ph.D.
> > > R&D Engineer, Kitware Inc.
> > > (518) 371-3971 x132
> > > jeff.baumes at kitware.com
> > >
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
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>

-- 
Karthik Krishnan
R&D Engineer,
Kitware Inc.
Ph: 518 881 4919
Fax: 518 371 4573
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