[vtkusers] best way to clip vtkImageData using vtkPloyData

[Prathamesh Kulkarni]

Thanks for the directions.. Here is what I did:

blended_image->SetInput(blank_image);
blended_image->AddInput(red_image);
blended_image->SetSencil(image_stencil_data);
blended_image->Update();


Am I missing something here? Setting the stencil is not having any effect on
the output. I am only getting a bled of blank_image and red_image.

Thanks,
Prathamesh

On Fri, Jul 16, 2010 at 11:38 AM, David Gobbi <david.gobbi at gmail.com> wrote:

> In vtkImageBlend, you need to have two inputs or else the filter will
> do nothing.  The first input to vtkImageBlend is the background image,
> and the second inputs is pasted on top of the first image, using the
> stencil to specify a cut-out region.
>
> So if you want to make several colored regions, you need to have
> several solid-colored images to start with, and then paste each one on
> top of your background using the proper stencil for that color.  Use
> several vtkImageBlend filters in a chain, each one will add another
> colored region to the image.
>
> You can create a solid-colored image by creating a vtkLookupTable that
> has just one color, and pass an input image of the desired sized
> through vtkImageMapToColors to map the image to that color.  For the
> background, you can either use your original image (mapped to RBG so
> that other images can be blended on top of it), or you can use a black
> image created by mapping your original image through a black lookup
> table.
>
>   David
>
>
> On Thu, Jul 15, 2010 at 11:05 PM, Prathamesh Kulkarni
> <prathameshmkulkarni at gmail.com> wrote:
> > I managed to add more than one stencils by using the
> > combined_vtkImageStencilData->Add(new_vtkImageStencilData) and then
> setting
> > vtkImageStencil->AddStencil(combined_vtkImageStencilData);
> > However, I have not been able to figure out a way to set the foreground
> > color of any stencil to a given value. The aim is to show every stencil
> with
> > a different color in the vtkImageData (= vtkImageStencil->GetOutput()).
> > Any help will be highly appreciated.
> >
> > Thanks,
> > Prathamesh
> > On Thu, Jul 15, 2010 at 6:52 PM, Prathamesh Kulkarni
> > <prathameshmkulkarni at gmail.com> wrote:
> >>
> >> I managed use vtkImageStencil and vtkImageAccumulate, but could not get
> a
> >> proper blended image output with vtkImageBlend. Following is my code
> snippet
> >> for vtkImageBlend:
> >>
> >>         blended_image->SetInput(image_data);
> >>         blended_image->SetStencil(image_stencil_data);
> >>
> >>         blended_image->SetOpacity(1, opacity)
> >>         blended_image->Update();
> >>
> >> When I try to render blended_image->GetOutput(), I simply get the input
> >> image, as if setting the stencil had no effect. I expected to see a
> >> different opacity in the stencil region. Please tell me if I am missing
> >> anything here.
> >>
> >>
> >> Also, I was wondering how to add multiple stencils to vtkImageStencil so
> >> that at the output I can have a vtkImageData showing multiple stencils
> with
> >> different colors.
> >>
> >> In any case, I did not understand how to set the foreground color of a
> >> single stencil.
> >>
> >>
> >>
> >> Sorry for putting in 3 questions together.. Thanks for your answers in
> >> advance.
> >>
> >>
> >> Prathamesh
> >>
> >>
> >> On Wed, Jul 14, 2010 at 5:31 PM, David Gobbi <david.gobbi at gmail.com>
> >> wrote:
> >>>
> >>> Hi Prathamesh,
> >>>
> >>> You should use either vtkClipVolume or vtkImageStencil, based on what
> >>> you want as an output. The vtkClipVolume filter will output an
> >>> unstructured grid, i.e. it will produce a geometric data set
> >>> consisting of voxel cells (each voxel cell will be a little cube with
> >>> eight points at its corners).  If you want the output to be an actual
> >>> image, with the background set to black or to transparent, then you
> >>> should use vtkImageStencil.
> >>>
> >>> In either case, the best place to start is vtkImplicitLoop, which
> >>> takes a contour and produces an "implicit function", which in
> >>> VTK-speak, is a function used to define the inside vs. the outside of
> >>> a selection area.  Then the vtkImplicitLoop can be used as an input to
> >>> vtkImplicitFunctionToImageStencil.  The output of
> >>> vtkImplicitFunctionToImageStencil can then be used as an input to e.g.
> >>> vtkImageBlend (for pasting a cut-out image onto another image),
> >>> vtkImageStencil (for blacking out the non-selected region of the
> >>> image), or vtkImageAccumulate (for computing the average value,
> >>> standard deviation, or the histogram of the image area inside the
> >>> stencil).
> >>>
> >>>   David
> >>>
> >>>
> >>>
> >>>
> >>> On Wed, Jul 14, 2010 at 4:13 PM, Prathamesh Kulkarni
> >>> <prathameshmkulkarni at gmail.com> wrote:
> >>> >
> >>> > Hello all,
> >>> >
> >>> > I want to extract a sub-image from vtkImageData given a closed set of
> >>> > points
> >>> > forming any arbitrary shape (may be a vtkPolyData).
> >>> >
> >>> > I have been looking at vtk classes like vtkClipVolume, vtkExtractVOI,
> >>> > vtkImageStencil. I am no able to understand which way should be
> >>> > preferred
> >>> > over which to do my task. Also, I am not able to figure out the exact
> >>> > pipeline structure for these clipping methods.
> >>> >
> >>> > Could someone please throw some light on this?
> >>> >
> >>> > Thanks,
> >>> > Prathamesh
> >>> >
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> >>
> >
> >
>
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