[Insight-users] coordinate conversion

[Petr Jilkine]

yes it is

# vtk DataFile Version 3.0
vtk output
ASCII
DATASET POLYDATA
POINTS 2402 float
-0.808409 1.14813 17.7883 -0.817523 1.32669 17.7764 -2.34968 1.10108
17.9052



On Tue, Sep 10, 2013 at 11:45 AM, Siavash Khallaghi <siavashk at ece.ubc.ca>wrote:

> What is the format of your point set? Is it vtkPolyData?
>
> Siavash
>
> Petr Jilkine <petr.jilkine at cimtec-canada.ca> wrote:
>>
>> Hello,
>>
>> I have 2 images fixed and moving. I apply some linear transform to moving
>> image
>> to bring it to physical space of fixed image using ResampleImageFilter
>> (see metacode)
>>
>>   typedef typename itk::ResampleImageFilter< InputImageType,
>> OutputImageType > ResampleFilterType;
>>   ResampleFilterType::Pointer resample = ResampleFilterType::New();
>>
>>   resample->SetInput( moving );
>>   resample->SetTransform( transform );
>>   resample->SetSize( fixed->GetLargestPossibleRegion().GetSize() );
>>   resample->SetOutputOrigin(  fixed->GetOrigin() );
>>   resample->SetOutputSpacing( fixed->GetSpacing() );
>>   resample->SetOutputDirection( fixed->GetDirection() );
>>   resample->SetDefaultPixelValue( zeroValue );
>>
>> I also have 2 point sets, one in fixed, another in moving image.
>> I would like to resample moving point set in a similar way.
>> For this I use (metacode)
>>
>>   typedef itk::TransformMeshFilter< MeshType, MeshType, TransformType >
>> TransformMeshType;
>>
>>   TransformMeshType::Pointer movingTransformMesh =
>> TransformMeshType::New();
>>   movingTransformMesh->SetInput(movingMesh);
>>   movingTransformMesh->SetTransform(transform);
>>   movingTransformMesh->Update();
>> Probably I need to use an inverse transform instead.
>> I guess if the points in point sets had world coordinates if would work.
>> But coordinates of the points are wrt the center of corresponding image.
>> Now I need to convert these local coordinates to world coordinates taking
>> into account origin, spacing and direction matrix of the corresponding
>> image.
>> TransformMeshFilter seems a good candidate to do the job, but it is not
>> clear
>> how to pass origin, spacing and direction matrix to the filter.
>>
>> Coordinates conversion like this seems a standard problem and
>> I guess there is a standard way to do it in ITK. However, so far
>> I couldn’t find an appropriate ITK class/function.
>>
>> Any advice on this matter is really appreciated.
>>
>> Thanks,
>> Peter Jilkine
>>
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> --
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
>
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