[Insight-users] suppress shearing

[Erik Türke]

On 04/09/2010 11:48 PM, Luis Ibanez wrote:
>
> Hi Erik,
>
> A transform that allows for rotation and for anisotropic scaling
> is indirectly allowing for Skewing (or Shearing).
>
> In short,
> it is a transform that does not preserve the angles
> between two straight lines.
>
>
> In that case, the Affine Transform is what you need.
>
>
> However,
> you may want to look at the
>
>                   itkScaleSkewVersor3DTransform
>
> http://public.kitware.com/Insight/Doxygen/html/classitk_1_1ScaleSkewVersor3DTransform.html
>
>
> Just in case
> your definition of "shearing" is a bit more specific....
>
>
>
>      Regards,
>
>
>            Luis
>
>
>
> --------------------------------------------------------------------------------
> On Fri, Apr 9, 2010 at 10:32 AM, Erik Tuerke <tuerke at cbs.mpg.de 
> <mailto:tuerke at cbs.mpg.de>> wrote:
>
>     Hi!
>
>     Thanks for the reply!
>
>     Unfortunately i can not rely on an isotropic scaling. Sometimes it
>     will be enough, but the best would be to apply an anisotropic scaling.
>
>     cheers
>
>     ----- Original Message -----
>     From: "Bill Lorensen" <bill.lorensen at gmail.com
>     <mailto:bill.lorensen at gmail.com>>
>     To: "Erik Tuerke" <tuerke at cbs.mpg.de <mailto:tuerke at cbs.mpg.de>>
>     Cc: "insight-users" <insight-users at itk.org
>     <mailto:insight-users at itk.org>>
>     Sent: Friday, April 9, 2010 2:52:51 PM GMT +01:00 Amsterdam /
>     Berlin / Bern / Rome / Stockholm / Vienna
>     Subject: Re: [Insight-users] suppress shearing
>
>     itkSimiliarity2DTransform and itkSimilarity3DTransform ally rotation,
>     translation and isotropic scaling.
>
>     Is your scaling isotropic?
>
>     On Fri, Apr 9, 2010 at 4:39 AM, Erik Tuerke <tuerke at cbs.mpg.de
>     <mailto:tuerke at cbs.mpg.de>> wrote:
>     > Ahh...sorry for the double post but i am used to push strg-s to
>     save a text but unfortunately this is assigned to sent.
>     >
>     > anyway...
>     >
>     > I am seeking a transform which is capable of applying a
>     transformation in a way of translation, rotation and scaling.
>     > Since i did not found such a transform, i thought taking the
>     affine transform and suppress the shearing.
>     > Is there any way to do so? Maybe setting the optimizer scale to
>     0 for the respective parameters...but what are the shearing
>     parameters?
>     >
>     > Thanks!
>     >
>     > --
>     > Erik Türke
>     > Department of Neurophysics
>     > Max-Planck-Institute for Human Cognitive and Brain Sciences
>     > Stephanstrasse 1A
>     > 04103 Leipzig
>     > Germany
>     > Tel: +49 341 99 40-2440
>     > Email: tuerke at cbs.mpg.de <mailto:tuerke at cbs.mpg.de>
>     > www.cbs.mpg.de <http://www.cbs.mpg.de>
>     >
>     >
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>
>     --
>     Erik Türke
>     Department of Neurophysics
>     Max-Planck-Institute for Human Cognitive and Brain Sciences
>     Stephanstrasse 1A
>     04103 Leipzig
>     Germany
>     Tel: +49 341 99 40-2440
>     Email: tuerke at cbs.mpg.de <mailto:tuerke at cbs.mpg.de>
>     www.cbs.mpg.de <http://www.cbs.mpg.de>
>
>
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>
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>
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>
Hi!

Thanks for your reply!

Actually, what i want to do is ONLY a anisotropic scaling. The reason 
why i mentioned the translation and rotation is because i want to set 
these parameters gained from a rigid transform as a "initial 
parameters". But when applying the Scaling transform, rotation and 
translation should be fixed.

Rigid Transform(rotation and translation) - > Scaling 
Transform(anisotropic scaling)

So i want to perform the two transforms consecutively without having to 
resample the image after the rigid transform.
So my idea was to use a simple affine transform and making the rotation, 
translation and shearing parameters fixed by setting the respective 
optimizer-scalings to 0. But my guess is now there are no seperate 
scaling parameters. :-(

So i have to consider a different approach...

cheers








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