Add steps/offsets convenience constructor:

[timholy]

This adds a convenience constructor with the following syntax:

AxisArray(A::AbstractArray, (names...,), (steps...,), [(offsets...,)])

where steps is meant in the range-step sense, and offsets is like start for each coordinate. Requested in JuliaImages/Images.jl#542 (comment). I can add it to ImageAxes but I thought perhaps it would be worth gauging interest here first. CC @tknopp.

Is that one line in the docs enough, or does it need more explanation?

[tknopp]

Yes thanks, this looks good. I am just realizing that the range objects as we have them are not sufficient to define cell-centered grids. So what I actually would like to have is to define an image of e.g. 10x10mm^2 discretized into 2x2 voxels giving me positions located at (2.5,2.5), (2.5,7.5), (7.5,2.5), (7.5,7.5). But maybe this is something I should store in the MetaData of an ImageMeta object.

[timholy]

I'm not sure I see the problem. The ranges specify a grid; it's up to you to interpret what that grid means. If you want it to mean the cell centers, then just make sure that the offsets tuple expresses the position of the center of the first "corner" grid element.

[tknopp]

yes, this was more a self conversation that I need to reorganize my thinking. In the old Images.jl the actual grid points were never specified an in turn I could generate them cell centered when I needed them. Now I need to think about this when creating the AxisArray. So all fine.