While I was searching about Retina images for dmg, I found text about retina images in html page (Safari).
After a simple search in my hard disk, I found a
> tag, a special line, a line build in an unknown (to me) way. It have two entries to load an image:
the first loads the
1x image while the second loads a
I searched for 2x.jpg, and located some html files. I loaded one of them in TextEdit, search for 2x.jpg, and watch carefully the html text to locate what I wrote above.
The relevant entry in the Apple documentation is here .