[vtkusers] vtkWindowToImageFilter

[Mark Wyszomierski]

Hi Dominik,

That's the problem - if any part of the render window is overlapped,
or just off screen rendering is on, I'll get an incorrect image.

As far as I can tell, there is no way to do this at the moment. How
are other people doing this? I could try using vtkGL2PSExporter as you
suggested but it might be too slow to do quick screen captures.

Thanks,
Mark

On 4/3/07, Dominik Szczerba <domi at vision.ee.ethz.ch> wrote:
> With a png file the covered of off-desktop part will be empty.My code:
>
>                vtkSmartPointer<vtkPNGWriter> writer = vtkSmartPointer<vtkPNGWriter>::New();
>                w2i->Update();
>                writer->SetInputConnection(w2i->GetOutputPort());
>                writer->SetFileName((curr_fname+".png").c_str());
>                renWin->Render();
>                writer->Write();
>                w2i->Modified(); //w2i is a global
>
> BTW. The effect of vtkGL2PSExporter will always be OK.
> Dominik
>
> On Tuesday 03 April 2007 21:21, Mark Wyszomierski wrote:
> > Hi Dominik,
> >
> > That didn't seem to have any effect for me, because the bitmap is
> > already written out at the time writer->Write() is called.
> >
> > Can I ask you though, what happens if you drag your render window
> > partially off your desktop screen so it gets clipped by the edges - do
> > you still get the entire render window contents captured? Nothing I do
> > seems to get around this problem. I've traced into the render window
> > class and it does seem to be reading the pixels from the back buffer:
> >
> >     glReadBuffer(static_cast<GLenum>(this->GetBackLeftBuffer()));
> >
> > still I get artifacts of overlapping windows in my screenshot!
> >
> > Thanks,
> > Mark
> >
> > On 4/3/07, Dominik Szczerba <domi at vision.ee.ethz.ch> wrote:
> > > I have w2i->Modified() after write, else doesnt work.
> > > --ds
> > >
> > > On Tuesday 03 April 2007 19:40, you wrote:
> > > > Hi,
> > > >
> > > > I'm using the source from the example page. Looks like:
> > > >
> > > > void CSomeClass::Screenshot(vtkRenderWindow* pRenWin)
> > > > {
> > > >     vtkWindowToImageFilter* w2i = vtkWindowToImageFilter::New();
> > > >     vtkBMPWriter* writer = vtkBMPWriter::New();
> > > >     w2i->SetInput(pRenWin);
> > > >     w2i->Update();
> > > >     writer->SetInputConnection(w2i->GetOutputPort());
> > > >     writer->SetFileName("C:\\test.bmp");
> > > >     pRenWin->Render();
> > > >     writer->Write();
> > > > }
> > > >
> > > > if the render window was doing offscreen rendering, the resulting
> > > > image will be just black. If doing on screen rendering, the filter
> > > > will just capture any other windows 'on top of' the render window. I
> > > > thought this filter used to capture exactly what was in the renderer,
> > > > regardless of what other windows were on top of it, or if it was doing
> > > > offscreen rendering. I know if I revert back to the VTK release
> > > > version the same code above works fine with offscreen rendering,
> > > > probably with onscreen rendering and overlapping windows?
> > > >
> > > > Thanks,
> > > > Mark
> > > >
> > > > On 4/3/07, Dominik Szczerba <domi at vision.ee.ethz.ch> wrote:
> > > > > I once had a similar problem (empty screen) and if I recall properly
> > > > > the solution was to call Modified() somewhere.
> > > > > Dominik
> > > > >
> > > > > On Tuesday 03 April 2007 15:19, Mark Wyszomierski wrote:
> > > > > > Hi,
> > > > > >
> > > > > > Has anyone tried using the CVS version of vtkWindowToImageFilter?
> > > > > > It seems to produce an empty image when used. Reverting back to the
> > > > > > 'release' version 5x of VTK, the same code that uses it produces
> > > > > > correct results. Just wondering if anyone experienced the same
> > > > > > thing or any ways around it,
> > > > > >
> > > > > > Thanks,
> > > > > > Mark
> > > > > > _______________________________________________
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> > > > >
> > > > > --
> > > > > Dominik Szczerba, PhD
> > > > > Computer Vision Lab CH-8092 Zurich
> > > > > http://www.vision.ee.ethz.ch/~domi
> > > > > _______________________________________________
> > > > > This is the private VTK discussion list.
> > > > > Please keep messages on-topic. Check the FAQ at:
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> > >
> > > --
> > > Dominik Szczerba, PhD
> > > Computer Vision Lab CH-8092 Zurich
> > > http://www.vision.ee.ethz.ch/~domi
> > > _______________________________________________
> > > This is the private VTK discussion list.
> > > Please keep messages on-topic. Check the FAQ at:
> > > http://www.vtk.org/Wiki/VTK_FAQ Follow this link to
> > > subscribe/unsubscribe:
> > > http://www.vtk.org/mailman/listinfo/vtkusers
>
> --
> Dominik Szczerba, PhD
> Computer Vision Lab CH-8092 Zurich
> http://www.vision.ee.ethz.ch/~domi
> _______________________________________________
> This is the private VTK discussion list.
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