Overlapping blocks: here or a new package?

@kescobo was asking in the #image-processing slack about assembling a bunch of individual, overlapping images into a single larger image while maintaining the ability to access each individual underlying array. The translations needed to align the images in their regions of overlap is done by external tools, but once you know what those translations are, this seems quite a lot like "mortar + overlaps". We wondered whether it would be better to add this to BlockArrays.jl, or whether it would complicate things here to the point that it's better done as an external package. Just wondering what the maintainers of this package would prefer.

@kescobo, I forgot to ask: are all the transformations pure translations? If there are rotations/etc, presumably that might be important to know at the outset.

Start with the issue discussion and the existing BlockArrays.jl concepts mentioned there, especially mortar and overlaps. Clarify whether the requested transformations are pure translations or also include rotations, then determine whether the capability belongs in BlockArrays.jl or an external package. Done means the maintainers have a decided scope and package location.