[Insight-users] RE: increasing bspline control point density

[Luis Ibanez]

Hi Karl,

For your convenience we just added an example to ITK
illustrating how you can increase the resolution of
the BSpline transform grid in order to refine a
deformable registration.


You will find this new example under:

   Insight/Examples/Registration/
             DeformableRegistration6.cxx

http://www.itk.org/cgi-bin/viewcvs.cgi/Examples/Registration/DeformableRegistration6.cxx?root=Insight

You will have to update your CVS checkout in order
to get this new file.


The example is mostly based on DeformableRegistration4.cxx,
and a second stage was added in which another BSpline
transform with higher resolution grid is configured.

Please let us know if you find any problems or
have further questions.


    Thanks


      Luis


----------------
Karl Baum wrote:
> Jim,
> You are correct in stating that I would like to "upsample" the B-Spline and
> not the image.
> Thanks,
> Karl
> 
> 
> Date: Fri, 23 Jul 2004 10:25:43 -0400
> From: "Miller, James V (Research)" <millerjv at crd.ge.com>
> Subject: RE: [Insight-users] increasing bspline control point density
> To: "'Stefan Klein'" <stefan at isi.uu.nl>, insight-users at itk.org
> 
> I think the BSplineUpsampleImageFilter upsamples an image via B-spline
> interpolation. I think Karl wants to "upsample" his B-spline not an image.
>  
> Jim
> 
> -----Original Message-----
> From: Stefan Klein [mailto:stefan at isi.uu.nl]
> Sent: Friday, July 23, 2004 9:21 AM
> To: insight-users at itk.org
> Subject: RE: [Insight-users] increasing bspline control point density
> 
> 
> Hi Karl,
> 
> You may use the itk::BSplineUpsampleImageFilter.
> Look at the help of itk::BSplineUpsampleImageFilterBase. There it's
> explained how it works.
> 
> Regards,
> Stefan.
> 
> 
> 
> 
> At 08:46 23/07/04, Miller, James V (Research) wrote:
> 
> 
> I do not think ITK provides a mechanism for increasing the number of 
> control points in a B-spline grid.  However, the mathematics of B-splines
> do support this operation.  There are formulas for adding a control point
> to a B-spline that maintain the trace of the B-spline (shape of the
> B-spline).
> 
> Any good book on B-splines will provide the formulas. 
> 
> Jim
> 
> 
> 
> -----Original Message-----
> From: Karl Baum [ mailto:kgbaum at syr.edu <mailto:kgbaum at syr.edu> ]
> Sent: Thursday, July 22, 2004 5:22 PM
> To: insight-users at itk.org
> Subject: [Insight-users] increasing bspline control point density
> 
> 
> Hi,
> I am using BSplines to provide the transformations necessary for my
> registration.  I would like to take an iterative approach where I first do
> registration with a low control point density, and then use the results as
> input to a registration with a higher control point density.  The issue I am
> facing at this point in time is how to initialize the parameters of the
> second iteration with the results of the first iteration.  In other words I
> need to take the grid defined by the deformation coefficients of the first
> iteration, and use it as input into the second.  To do this I need to
> calculate the starting deformation coefficients on the higher density grid. 
> 
> Does itk provide anything to do this?  I was unable to find any
> documentation addressing this.
> 
> Thanks,
> Karl
> 
> 
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