How Do You Save / Convert an Image to Be in the Frequency Domain? Quick Note: I don't believe this is a subjective question... however if it is I will gladly modify to be more objective

In ImageJ, if I take the FFT of an image, how can I save this new frequency domain image? The goal being that I would like to be able to open it up and take the IFFT.

When I try this, imageJ says you need to have a frequency domain image. This leaves me thinking that whatever information it has about the frequency domain is lost once I save.

My end goal is to take images that I have taken the FFT of from a python script that I am debugging and load them up in imageJ and take the IFFT.
A trick would be to use the TIFF format which supports many channels.
For each channel in your original image create 2 channels, one for the magnitude and the other for the phase.

TIFF supports 32 bit hence data will be well preserved.