Strides and Nifti image orientation

Dear experts,

I have a NIfTI image which orientation is RPI. When displaying the image details with mrinfo -norealign, the strides given are [1 2 3], however I thought they would be [1,-2,-3] for RPI orientation.

Thanks for your help with this.


Welcome to the MRtrix forum!

To answer your question: this is exactly as expected. NIfTI assumes fixed strides of 1,2,3,… and using the -norealign option instructs mrinfo to leave that information exactly as it was on file. It’s what happens when you don’t use the -norealign option that can get confusing… There’s quite a detailed explanation of these issues in this post, hopefully this will answer your question.

Dear Donald,

Thanks a lot for your reply and link towards a similar post. I’ve understood now.