[Insight-users] Resample an image to a higher resolution in the same space with a zero derivative edge condition

Seth Gilchrist seth at mech.ubc.ca
Fri Sep 24 13:07:45 EDT 2010


Hi Kishore,
This is indeed very helpful.  Thanks for your time.

Regards,
Seth

On Fri, Sep 24, 2010 at 10:00 AM, Kishore Mosaliganti <kishoreraom at gmail.com
> wrote:

> Is this class relevant to your problem?
>
>
> http://www.itk.org/Doxygen318/html/classitk_1_1ZeroFluxNeumannBoundaryCondition.html
>
> Kishore
>
> On Thu, Sep 23, 2010 at 5:42 PM, Seth Gilchrist <seth at mech.ubc.ca> wrote:
> > Hello,
> > I know what you are thinking...why are you up-sampling an image?  Here is
> > the situation and problem and I hope that you can help.
> >
> > I have an image of vectors (3D image, 3D vectors) that is of a course
> > resolution (35,20,20).  These vectors represent the displacement of a
> > grouping of pixels in a fixed image. Each voxel in the vector image
> > represents the average displacement of 21x21x21 voxels in the fixed
> image.
> > What I want to do is linearly interpolate the data from the course vector
> > image into the grid (they occupy the same space) of the fixed image.  The
> > new vector image will then be used to morph the fixed image into the
> moving
> > image space, giving a deformable-like transform, and then the fixed and
> > moving image can be operated on in the same space.
> >
> > The problem is that when interpolating the values at the edge of the
> vector
> > image the interpolator uses a single value for the out-of-bounds pixels.
> > This means that the vectors at the edge of my new vector image converge
> to
> > the displacement represented by the out-of-bounds value (a constant).
> What
> > I would like, is to have the edge given a zero derivative (Neumann)
> > condition (or even better, be able to try a few different boundary
> > conditions).  I have looked through the interpolate and resample filters
> and
> > can't seem to find this already implemented.  Has this been done, or
> should
> > I just get on writing it myself?
> >
> > Thanks for your time and help.
> >
> > Regards,
> > Seth
> >
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