[Neuroimaging] why 2 affine transforms in the nifti

[VRomain]

Hello


As suggest by oscar I open a new thread, since there may be nothing to 
do with Nibabel CZI grant


So to resume, I sometimes get  troubles when playing with different 
software, because of the 2 affines stored in the nifti file.

(some software thing one should only read / write the sform, other the 
qform, so it is easy to get to inconsistency, that will just scratch 
your results)

Thanks @ oscar to point out the nitransforms repo - 
https://github.com/poldracklab/nitransforms 
<https://github.com/poldracklab/nitransforms>)

I'll have a closer look, this is indeed an important objectiv


I am curious, to know why it was a clever idea to store 2 affine ? ( I 
probably miss the point ... )

 From what I understand, it was meant to get an history of the 
registration made on the data. The only software I know that use it, is 
spm coregister function. they update the sform and keep the qform. Ok we 
can come back, but if for any reason one have to coregister a second 
time, then the information is lost (because they chose to update the 
sform, and the qform take the old sform value ...)