[Insight-users] Re: [Insight-developers] How to combine centered transforms

[Luis Ibanez]

Hi Richard,


Centered transforms are redundant in the sense that you could
modify the center and compensate with the values of the
translation in order to recover the same final transformation.

This means that you have some freedom for selecting the center
of rotation of the composed transform. Natural options could be
to keep the same center of rotation of the second transform.

Please take a look at the equation corresponding to the centered
transforms in the ITK Software Guide:

        http://www.itk.org/ItkSoftwareGuide.pdf

 From it you can deduce how the center of the first transform
will be rotated by the second transform and will end up being
part of the translation of the combined transforms.


Please let us know if you find any difficulty on defining
the computation of the combined transform.


    Thanks



       Luis



------------------------
Richard Beare wrote:
> Hi Everyone,
> 
> I'm registering a stack of slices in a pairwise fashion, using a
> Rigid2DTransform. In order to reconstruct the stack I need to combine
> the transforms from all previous slices. It is obvious how to deal
> with angle and translation, but what is the correct way of dealing
> with the center?
> 
> Thanks
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>