Slicing-à-la-Photoshop in Javascript

Question

Hello,

I am trying to do something very hard (well, hard to me at least): I would like to create a slicer (like Photoshop's one) in Javascript.

For now, I just concluded the Photoshop function creates "immuable" points each time you do a slice, and create 4 automatics slices (more if the slice overlap more than one other) around, which could be automatically merged further, for example.

I have no problem with creating a slice inside another one, but I don't really understand how does Photoshop proceed when the new slice overlap many.

Thanks.