Version: (using KDE 4.4.0) Installed from: SuSE RPMs For now when comparing images the best option is to run two instances of Gwenview and manually go from one image to another. And next image, and next. It would be more useful if gwenview could provide split screen view (note: synchronized!) or could communicate with another instance of gwenview -- in the latter case it would send "signal": go to file "xyz.jpg" (please note, there should be no directory included). And that's it -- one gwenview would be master, the other slave. No extra functions are needed.
Maybe just for being sure: the problem is -- you have two directories A and B with files with identical names (some file may be missing though). Let's say A contains "original" files, and B with color reduced, or sepia added, etc. So you want to see the original file and the effect of it. And such function -- gwenview talking to each other, to keep current image in sync, would work for such problem just great.
*** Bug 131832 has been marked as a duplicate of this bug. ***
In fact, Gwenview now has this feature! In browse mode, select two pictures and hit return. Now they're compared side-by-side. You can click "Synchronize" to sync them up.