save image

I believe I am jumping in at the deep end here but Ill give it a go.
I have some code I found on stack overflow (cudos to Kuba Ober) I have attached it.
It creates a photomosaic.
Id like to be able to save the mosaic it creates to a directory.
Im on a mac.
Ive been bumbling around for a while now. Im hoping someone could show me and from there I can figure out other things I want to do.
I am learning C++ but Im only at the early stages so please forgive my ignorance.

See QImage::save()

Cheers,
_