Multiple images in some vsi files?

[ruoyussh]

Hi Nico,

First of all, thank you for your great effort in developing this fork.

I was wondering when we read vsi files, there're sometimes multiple images within a vsi file (label, overview and tissue section in high power).

Does this library provide a interface which allows us to specify which sub-image we want to read? Maybe there is one but I missed it?

Many thanks, Ruoyu