Hello,

I am trying to compute the difference between an image and its left-right flipped version.

In SPM, if I first use ‘reorient’ then ‘imcalc’ to compute the difference, everything works as expected.

Now, I would like to perform the same operations using the Python ecosystem (nibabel, nipy, nilearn…)

I tried to use `nilearn.image.math_img`

, but it refuses to perform a computation with images having different affines (which sort of makes sense). Yet, because in SPM, the left-right flipping is achieved by changing the sign of the XX component of the affine so I cannot use the Python script on flipped images generated by SPM.

I tried to flip the data, using `nilearn.image.swap_img_hemispheres`

, which presumably uses numpy flip to flip the data array. But the result is not satisfactory (the axis of symmetry is a bit shifted from the center when I visualize the image).

Any suggestions?

It would be cool if nilearn’s `math_img`

could perform arithmetic operations between images “in the world space” and take care ‘automagically’ of resampling.