If you use Live Stack on the ASIAIR and you save the resulting image, it generates two images.
(1) it saves a .FIT image to either the ASIAIR system microSD card or an attached USB flash drive depending on how you have configured which device you wish to use.
(2) It will also generate a .JPG version of the image on your iPad/iPhone or whatever phone/tablet device you are using to control the ASIAIR.
So if you want to do further processing on the image, you would normally load the .FIT file into software that can handle that format and you can process it to your hearts content. It is basically an unstretched image which will appear very dark when first opened whereas the .JPG file appears as it did in the Live Stack view.
To transfer an image to a MAC you can just take the USB flash drive from the ASIAIR and plug it into the MAC or I believe there are ways of wirelessly transferring the files.
JohnD