[Insight-users] How to implement to only rotate images in the

[Elena Pavlovskaia]

Hello Luis, ÒÂÎÄÎÄ,

> setting the optimizer scaling values in such a  way that
> translations will be insignificant

This is what I did with Rigid3DTransform and where I got to a problem
reported in

http://public.kitware.com/pipermail/insight-users/2007-February/020926.html
(RegularStepGradientDescentBaseOptimizer::AdvanceOneStep problem)

In my case the images where pretty well aligned along the translation
component. The chances of getting a gradient with almost zero translation
components were very high. When that happened, my image jumped A LOT along
the rotation component. Later the RegularStepGradientDescentBaseOptimizer
converged to a wrong local minimum.

Since then I use the fix suggested in the same posting, and it works fine.

Elena


-------------
Luis wrote:

Hi ÒÂÎÄÎÄ

There is not an equivalent of a rotation-only
Transform for 2D in ITK.

You could get a similar effect by using the
itkRigid2DTransform.txx and setting the
optimizer scaling values in such a  way that
translations will be insignificant.

You can also write your own 2D rotation-only
Transform by deriving from the itkRigid2DTransform
and overloading the GetParameters() and SetParameters()
methods.


    Regards,


       Luis



-----------------
ÒÂÎÄÎÄ wrote:
> Hi Luis,
>
> Thank you for your reply.
> The VersorTransform is very useful for me.
> I want to know if there is such a transform for 2D images.
>
> Regards,
> Yi Wenwen
>
> ÔÚ2007-03-26£¬Luis Ibanez <luis.ibanez at kitware.com> дµÀ£º Hi Yi,
>
> You may want to use the VersorTransform:
>
> http://www.itk.org/Insight/Doxygen/html/classitk_1_1VersorTransform.html
>
> You will find details about this Transform class
> in the ITK Software Guide
>
>
> http://www.itk.org/ItkSoftwareGuide.pdf
>
> in the "Image Registration" Chapter.
>
>
> Note that it is *VERY IMPORTANT* for you to set the
> Center of rotation before you use this transform.
>
>
> Regards,
>
>
> Luis
>
>
> -------------
> ÒÂÎÄÎÄ wrote:
>  > Hi, everyone,
>  > I want to only rotate images but not translate images in the process of
>  > registration.
>  > Who can tell me how to implement it by setting the parameters of
>  > Transform classes?
>  >
>  > Thanks for any tips.
>  > Regards,
>  > Yi Wenwen
>  >
>  >
>
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