[Insight-users] Re: Landmark Based transform initializer

[Karthik Krishnan]

Kevin,

To the best of my knowledge the class is doing the right thing and so is 
your code, (you've swapped the moving and fixed landmark roles).
Lines 86-87 of your code should read as, which is what you had earlier.
    initializer->SetFixedLandmarks( fixedLandmarks );
    initializer->SetMovingLandmarks( movingLandmarks );

With the following command line args: I get the second cow to overlap 
pretty well with the

http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/cow_0.jpeg 

> 11:06AM $ ./itk_landmark_transform cow_0.mhd cow_1.mhd 
> transformed_cow.mhd 97 245 331 61 88 240 334 
> 74                                         

  Fixed Landmark: [97, 245] Moving landmark [88, 240] Transformed fixed 
Landmark : [87.6235, 240.254]
  Fixed Landmark: [331, 61] Moving landmark [334, 74] Transformed fixed 
Landmark : [334.377, 73.7459]

Possible sources of confusion are:

1. The fixed landmarks after transformation through the transform 
produced should have the same values as the moving landmarks. Not the 
other way around.
2. Use InsightApplications/ImageViewer to view your .mhd output. The 
y-axis you are looking at might be flipped with respect to the image 
co-ordinates. It helps to use a viewer built using ITK, so you never 
have any co-ordinate confusion.

karthik


Kevin H. Hobbs wrote:

>On Mon, 2005-05-23 at 06:49 -0400, Karthik Krishnan wrote:
>  
>
>>Kevin:
>>
>>The class supports the Rigid2DTransform as well as the
>>VersorRigid3DTransform now. Please update your cvs repository. For usage,
>>please see the test
>>Testing/Code/Common/itkLandmarkBasedTransformInitializerTest.cxx
>>
>>Thanks
>>Regards
>>Karthik
>>    
>>
>
>
>I've put up a bit of code using the new
>itkLandmarkBasedTransformInitializer.
>
>http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/itk_landmark_transform.cxx
>
>It's mostly cobbled together from 
>Insight/Examples/Filtering/ResampleImageFilter6.cxx and
>Testing/Code/Common/itkLandmarkBasedTransformInitializerTest.cxx
>
>The transform seems to have rotated the moving image in the wrong
>direction.
>Fixed image:
>  http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/cow_0.jpeg 
>Moving image:
>  http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/cow_1.jpeg
>Difference of fixed and moving image:
>  http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/cow_diff_0_1.jpeg
>Difference of fixed and translated moving image:
>  http://crab-lab.zool.ohiou.edu/kevin/Slice_Landmark_Registration/cow_diff_0_trans_1.jpeg
>
>Did I mess something up with the transform, centers of rotation and the
>like?
>  
>
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