[Insight-users] Confidence Connected Seed Coordinates

[Luis Ibanez]

Hi Cameron,


If you want to find the pixel value of an ITK image at a given physical
coordinate you may want to consider the two following options:


A)  ImageType::PointType  point = GetPointSomehow();
     ImageType::IndexType  index;
     ImageType::PixelType  pixelValue;

     ImageType::ConstPointer image = seriesReader->GetOutput();

     image->TransformPhysicalPointToIndex( point, index );

     if( image->GetBufferedRegion().IsInside(index) )
       {
       pixelValue = image->GetPixel( index );
       }

or


B)  use the itk::NearestNeighborInterpolateImageFunction
     as Interpolator type,


     ImageType::ConstPointer image = seriesReader->GetOutput();

     interpolator->SetImage( image );

     pixelValue = interpolator->Evaluate( point );


 From your email, it seem that you are more interested on the
index location than the actual pixel value. In that case, you
probably only need the first half of option (A).


   Regards,


      Luis


------------------------
Cameron Burnett wrote:
> Oh ok. So there is no way to perhaps extract a pixel at a certain 
> physical coordinate, from the ImageSeriesReader object ?? I had a look 
> at the doxygen documentation for itk::ImageSeriesReader but there wasn't 
> any method like that.
> 
> The problem is that I'm doing this with 3D interaction. At the moment I 
> don't have any 2D viewports at all. In order to find a seed point, the 
> only logical thing I could think of was a vtkPointWidget. If that 
> doesn't end up working then I'm not sure if it would be possible to do 
> 3D region growing at all. Unless I can guess the seed point.
> 
> Any ideas??
> 
> Thanks.
> 
> 
> 
> ------------------------------------------------------------------------
>  > Date: Mon, 14 Apr 2008 10:16:44 -0400
>  > From: bill.lorensen at gmail.com
>  > To: w_e_b_m_a_s_t_e_r_6_9 at hotmail.com
>  > Subject: Re: [Insight-users] Confidence Connected Seed Coordinates
>  > CC: insight-users at itk.org
>  >
>  > Cameron,
>  >
>  > The Seed coordinates are in pixels, not physical coordinates. IN
>  > addition, VTK flips the image, so you will need to flip your Y pixel
>  > coordinate.
>  >
>  > We should probably add a method to the filters with Seeds to accept
>  > physical coordinates. Please add a feature request in the ITK bug
>  > tracker.
>  >
>  > This page explains how to submit a bug:
>  > http://www.itk.org/Wiki/ITK_Procedure_for_Contributing_Bug_Fixes
>  >
>  > Thanks,
>  >
>  > Bill
>  >
>  >
>  > On Mon, Apr 14, 2008 at 9:56 AM, Cameron Burnett
>  > <w_e_b_m_a_s_t_e_r_6_9 at hotmail.com> wrote:
>  > >
>  > > Hi,
>  > >
>  > > I'm just wondering about the coordinate system of the confidence 
> connected
>  > > algorithm. I'm using a vtkPointWidget to select a seed point, and 
> according
>  > > to the point widget, my XY coordinates range from about -45,413 
> (top-left)
>  > > to 413,-45 (bottom-right).... and also a z coordinate which I've 
> got as 7.5
>  > > (middle slice).
>  > >
>  > > Now, when I plug that into the confidence connected SetSeed() method, I
>  > > don't think the two coordinate systems are matching up because my 
> results
>  > > are a bit strange.
>  > >
>  > >
>  > > The following picture is an image of two legs, and you can see the
>  > > vtkPointWidget being positioned in the center of the femur.
>  > >
>  > > http://img382.imageshack.us/img382/2118/dicomimgaw7.jpg
>  > >
>  > > This is the result of a multiplier of 0.1, followed by a multiplier 
> of 2.
>  > >
>  > > http://img397.imageshack.us/img397/9743/outputvtk01multiplierwd7.jpg
>  > > http://img383.imageshack.us/img383/6727/outputvtk2multiplierfs6.jpg
>  > >
>  > > (Note: I think these may be a bit pixely due to the compression on
>  > > imageshack, but the actual ones are just 2 solid colours)
>  > >
>  > >
>  > > What I conclude from that is that the blue area is in fact the area 
> that has
>  > > been seeded, not the red area. Therefore that is why I believe that 
> I have
>  > > some sort of problem with the coordinates not matching. What do I 
> have to do
>  > > to make sure the point widget and the SetSeed() method both match up??
>  > >
>  > > And I also don't know why there are 2 colours in the vtk file, when one
>  > > should obviously be transparent. Is that one easy to answer?
>  > >
>  > >
>  > > Thanks for any help,
>  > > Cameron.
>  > >
>  > >
>  > >
>  > > ________________________________
>  > > Grab it. You dream job is up for grabs.
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>  > >
>  > >
> 
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