[ITK-users] Multiply VariableSizeMatrix by VariableLengthVector

[Francois Budin]

Hello Cyril,

For the matrix conversion, you can use itk::Matrix::GetVnlMatrix() to
extract the matrix from the itk::Matrix object, and use assign that vnl
matrix to your itk::VariableLengthVector using operator=(const vnl_matrix<
T > &matrix).

itk::Matrix<float,3,3> mat;
itk::VariableSizeMatrix<float> v_mat;
v_mat = mat.GetVnlMatrix();

For the vectors, you could get access to the data from itk::Vector and pass
the pointer to the data to your itk::VariableLengthVector.
itk::Vector<float> vec;
itk::VariableLengthVector<float> v_vec;
v_vec.SetSize(3);
v_vec.SetData(vec.GetDataPointer(),false);

Be careful with the memory management for the vector as the data is still
managed by the itk::Vector in this example, so the data will be destroyed
if the vector is destroyed (if you go out of scope).

On Mon, Sep 19, 2016 at 11:05 AM, Cyril Mory <
cyril.mory at creatis.insa-lyon.fr> wrote:

> Hi ITK users,
>
> I have some working ITK code with itk::Matrix by itk::Vector
> multiplications, and I need to change to itk::VariableSizeMatrix and
> itk::VariableLengthVector.
>
> Simply writing
>
> "myResultVector = myMatrix * myInputVector"
>
> works with itk::Matrix and itk::Vector objects, but not with their
> VariableSize/Length counterparts. Is there a way to do it, other than
> writing the matrix by vector multiplication for-loops myself ?
>
> Regards,
>
> Cyril
>
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