[Insight-users] point based registration using least square

[Suyang Mei]

  Thanks a lot, for the help!
  I did successfully use itk::LandmarkBasedTransformInitializer to generate results.
  My question is - does this class support affine transform? looks to me it is working fine with rigid body transform, but the results not correct if it is affine, for example, I input the following points -

The points are 
 
X=[36,257; 
77,257; 30,370; 62,370;77,323];
 
X'=[118,257;77,257;126,370;93,370;77,323];

 R =

   -0.9999    0.0110
    0.0110    0.9999

is the rotation matrix I am expecting to get (I got from MATLAB svd), but I got 

R =

   0.980838    -0.194827
   0.194827    0.980838



--- On Wed, 5/5/10, Andinet Enquobahrie <andinet.enqu at kitware.com> wrote:

From: Andinet Enquobahrie <andinet.enqu at kitware.com>
Subject: Re: [Insight-users] point based registration using least square
To: "Suyang Mei" <suyang_mei at yahoo.com>
Cc: insight-users at itk.org
Date: Wednesday, May 5, 2010, 4:54 AM

Hi Suyang-
There is ITK landmark-based registration class that probably does what you are looking for. 
itk::LandmarkBasedTransformInitializer
This registration class implements an absolute orientation solution using unit quaternions. It is a closed-form solution to the least-squares problem of computing transformation parameters between two coordinate systems.

Hope that helps-Andinet
On Tue, May 4, 2010 at 8:56 PM, Suyang Mei <suyang_mei at yahoo.com> wrote:


Hi, all -

  I have a simple question here -

I'd like to perform point based image registration by using least square approach (basically finding the rotation matrix by using singular value decomposition SVD). Inputs are two sets of corresponding points, and I just need to get the transformation matrix back. 



More like the functions in Examples\Patened\ICP*.cxx, but use closed form instead of iterative approach. What is the ITK filter to perform this?

  Thanks a lot in advance.

Suyang





      
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