Cutting and pasting subimages

[guynir42]

Need to get a generic tool to cut an image into subsections (with overlap) and then paste them back together with linear interpolation between the overlapping regions (feather).

This could be useful for coaddition/subtraction where we can use a smaller sub image where the PSF and background levels are more-or-less the same across the region, instead of assume that on the whole image.

[guynir42]

This might be easier to do using overlapping Hann windows, as in signal processing.

https://en.wikipedia.org/wiki/Hann_function

https://en.wikipedia.org/wiki/Short-time_Fourier_transform

https://en.wikipedia.org/wiki/Overlap%E2%80%93add_method

[guynir42]

This will be useful for ZOGY subtraction, as it will save a lot of memory. I am not sure if this will make the runs faster or slower. There could be other advantages such as doing alignment and background/flux matching better on small windows.