Why setting image as its own icon with sips result a blurred icon? Are there any alternatives?

I've successfully changed icons using the procedure described in an another question: Changing or setting a file or folder icon programmatically. Either my sips (or Finder) got broken afterwards or I just zoomed in for the first time (it seems the icon is sharp from ≈100x100 downwards), but, anyway, the icon that sips -i image.png creates is blurry/pixelated: What I did before the blurrification: $ cp FIN-2.png FIN-3.png $ sips -i FIN-3.png So FIN-2 and FIN-3 are the same. FIN-2 is a 512x512 PNG-file **Furthermore:** using sips breaks *all* further attempts when trying to set a custom icon even with *any GUI method* and with *any file* in *any folder*. Only cure is to delete ~/Library/Caches/com.apple.finder/ and restart Finder. Then changing icon via GUI (drag&drop, copy&paste) works normally with any file. --- Two main questions—and answering to either one probably solves the problem close enough for me: 2. **How can I set an image as an icon programmatically without using sips -i (= sips --addIcon) in the process?** (again, refer to the other question for more comprehensive info) - Shell (bash) or AppleScript is preferred - I could convert the PNG to e.g. ICNS if needed. 1. Is sips broken? Why/How? Can it be fixed; how? (Or is it the Finder? Or something else?)