Image.shift integer shifts

[garrettwrong]

Currently we use im_translate to perform image shifting via FFT. For integer (pixel) shifts we can use np.roll on the data directly.

I think the im_translate can be used in the case of subpixel shifts and in future optimized cases where we are already in F space.

I suspect this would just involve creating a function for the integer shifting and some test logic in shift.

[janden]

Outside of testing, are there significant uses of integer shifting that we need to cater to?

[garrettwrong]

We don't need to, but if we're not already in basis coef it is faster when we want to... (avoids basis round-trip/ffts).

The two uses of shifting in our pipeline are BF for class averaging (currently pixel shifts) and _generate_shift_phase_and_filter in common lines. The later probably should be using our image/basis based translating tool, but would not be pixel shifts.

FWIW, I removed this from the next release board because it isn't really a priority.

[janden]

Sounds good.

[garrettwrong]

I'm now thinking having different shifting methods is going to be dangerous/fragile. It would be better to have one we use all that time and works well.

Closing.