Compute affine matrix using direction, spacing and origin

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I want to compute the affine matrix manually for the image to convert between world and voxel coordinates. How can I do that using direction, spacing and origin that is returned using SimpleITK?

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itkindextophysicalpoint
itkindextophysicalpoint883×750 69.1 KB

This may answer your question.
Refer to [SOLVED]TransformIndexToPhysicalPoint manually - #9 by rolof - Beginner Questions - ITK