alt Hacker NewsWhat is it with commenters in this thread and wanting to "reliably scan one line at a time?" When users use image galleries, they generally do jump around because they're looking at all the options on screen all at once. The eyes absorb everything and then they pinpoint what looks good. I've never seen or heard anyone go line by line in an image gallery or a newspaper layout and doing so I'd find to be highly abnormal to average users.
I suspect if data from eye-tracking tests were available, there would be an extremely clear revealed preference from users. I read image galleries the exact same way I skim text, in an ordered fashion that allows me to "read" every image without reading an image twice, stopping if my attention is caught by something in particular. Splotting garbage over the screen haphazardly makes it blend together annoyingly and results in my eyes traversing the same areas multiple times both to try to pick out details and to try to keep my place in what I have/haven't skimmed yet. It is a layout that itself demands my attention, rather than letting my attention be absorbed naturally by the actual images.