Nope, you'll have to math a bit (it's always a rectangle)
.
Here's how the defaults look like, for example:
https://github.com/koreader/koreader...ment-736856442
In order of priority (hence the overlaps):
* Cyan: Corners
* Red: Footer
* Blue: Menus
* Green: Next page
* Yellow: Previous page
Note that, as far as page turns are concerned, these are specifically the *tap* zones. If you swipe to turn pages, that works across the whole screen, regardless of the tap zones.