[Insight-developers] reading Image<Matrix> as Image<SymmetricSecondRankTensor>

[Matthew McCormick (thewtex)]

Hi Luis,

On Mon, Jun 14, 2010 at 6:47 AM, Luis Ibanez <luis.ibanez at kitware.com>wrote:

>
> Hi Matt,
>
> Thanks for looking into this problem.
>
> I'm a bit confused about what you suggest in your email.
>
> Are you suggesting to change the test
> in order to also exercise a 2D case ?
>

Yes.


>
> or is it the core of the change, to use an image of
> SymmetricSecondRankTensor instead of Matrix2x2
> as the source for the image ?
>
>
Yes.  In any case, I need to write an image of SymmetricSecondRankTensor to
test the bug.  For consistency, I should then change the 3D case too?  But I
do not know if reading an image of Matrix as SymmetricSecondRankTensor is
behavior that is expected.  If so, I do not want to remove the test for it.
 Also if so, readers will need to be fixed to behave this way.  Personally,
I would not necessarily expect this behavior.


> Also, have you identified the changes that we will
> have to introduce in the Writer/Reader in order to
> get this test to pass ?
>

Changing the file name on the test shows that MetaImage, NRRD, and NIfTI all
pass for the 3D case.

As far as I can tell, NRRD and NIfTI do not support 3 component symmetric
second rank tensor.  MetaImage does support it, but its behavior would have
to change.  I am working on adding support to the VTKImageIO, but it can not
support generic 2x2 or 3x3 matrices.


>
>
> Could you please clarify ?
>
>
Hopefully this clarifies, but let me know if it is still unclear.

Thanks,
Matt


>
>     Thanks
>
>
>           Luis
>
>
> ----------------------------------------------------------
> On Sun, Jun 13, 2010 at 12:38 AM, Matthew McCormick (thewtex) <
> matt at mmmccormick.com> wrote:
>
>> Hi,
>>
>> I am working on adding 2D SymmetricSecondRankTensor image write support.
>> The bug is here.
>> http://vtk.org/Bug/view.php?id=10732
>>
>> In order to add a test for the bug, I was thinking of modifying
>> Testing/Code/IO/itkSymmetricSecondRankTensorImageReadTest.cxx
>>
>> Currently, this test creates an Image of 3x3 itk::Matrix, writes it to
>> file, reads it in as an Image of SymmetricSecondRankTensor's, and checks to
>> ensure the content is the same.
>>
>> If I try to do the same with 2x2 itk::Matrix, the
>> SymmetricSecondRankTensor reader does not read the correct components:
>> 941: Test command: /mnt/datab/itkcvsb/bin/itkIOTests
>> itkSymmetricSecondRankTensorImageReadTest
>> /mnt/datab/itkcvsb/Testing/Temporary/testSymmetricTensor1.nrrd
>> /mnt/datab/itkcvsb/Testing/Temporary/testSymmetricTensor2.nrrd
>> 941: Test timeout computed to be: 1500
>> 941: Tensor read does not match expected values
>> 941: Index [0, 0]
>> 941: Tensor value
>> 941: 1  2  2
>> 941: Matrix value
>> 941: 1 2
>> 941: 2 3
>> 941:
>>
>> If the commented code, where an image of 2D SymmetricSecondRankTensor (
>> instead of itk::Matrix ) is written, is used with the MetaImage format the
>> test can pass.
>>
>> Is it OK to change the test as in the commented code, or are other changes
>> required?
>>
>> Thanks,
>> Matt
>>
>>
>>
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