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

[Karl Baum]

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