This is a bug that makes Dolphin unusable for me so i always need to have another file manger installed that displays those file correctly: have a look at the screenshot(comparison between other fms and dolphin): Since other file managers(pcmanfm-qt here) do not scale(modify) the images to a fixed size its easy to see how they look(its actually a real preview) Reproducible: Always Expected Results: a preview mode similar to that of other file managers(pcmanfm, thunar, nautilus just to name a few) that shows the actual file and does not modify(eg: scale) it.
Your screenshots didn't make it, so I can't see what the exact issue is. But it seems that this is a duplicate of https://bugs.kde.org/show_bug.cgi?id=295526 *** This bug has been marked as a duplicate of bug 295526 ***