CODEWITHSUNDEEP
pythonsimpleitk
mehrtash
mehrtash

Reputation: 930

Get Matrix and Translation from a SimpleITK transform

I am reading an ITK transform from a file. I cannot figure out the API for getting the Translation or the Matrix directly from the transform. 

t = sitk.ReadTransform('sample_transform.h5')
print(t)

Here is the result of printing:

itk::simple::Transform
VersorRigid3DTransform (0x55c3e22f5de0)
RTTI typeinfo:   itk::VersorRigid3DTransform<double>
Reference Count: 1
Modified Time: 802
Debug: Off
Object Name: 
Observers: 
 none
Matrix: 
 0.999862 0.016289 0.00333268 
 -0.0161218 0.998848 -0.0451944 
 -0.00406501 0.0451344 0.998973 
Offset: [-1.3857, 0.238944, 0.984074]
Center: [36.1356, 6.81771, -27.0756]
Translation: [-1.36988, 0.872183, 1.17271]
Inverse: 
 0.999862 -0.0161218 -0.00406501 
 0.016289 0.998848 0.0451344 
 0.00333268 -0.0451944 0.998973 
Singular: 0
Versor: [ 0.0225887, 0.00184996, -0.00810505, 0.99971 ]

Are there functions to get the Matrix and Translation directly?

It looks likes that translation can be retrieved from the last three items of the t.GetParameters():

print(t.GetParameters())

would give:

(0.02258874140769294,
 0.0018499585651891462,
 -0.00810504740162434,
 -1.3698806341361933,
 0.8721829896773953,
 1.1727120470384382)

Upvotes: 2

Views: 2216

Answers (1)

blowekamp
blowekamp

Reputation: 1431

The ReadTransform methods always returns a std::Transform base class. That common interface can be useful. Sometime you the derived interface is wanted which provides the useful methods like GetTranslation and GetMatrix[1]. This can simply be done by converting/casting the base transform:

myVersorTransform = VersorRigid3DTransform(t)

[1] https://itk.org/SimpleITKDoxygen/html/classitk_1_1simple_1_1VersorRigid3DTransform.html

Upvotes: 2

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