Takže jsi postupoval podle tohoto návodu?

How to install (Script-Fu version):

1. Right-click on the link below that says "layerfx.scm". A pop-up menu should appear. Click "Save Target As..." or "Save Link As..." or whatever the equivalent option in your browser is.
2. Save the file "layerfx.scm" in your scripts folder. If you're not sure where your scripts folder is, you can check by opening GIMP and going to <Toolbox>/File/Preferences -> Folders -> Scripts. If more than one folder is shown, then any one of them will work.
3. Once you have saved the file in your scripts folder, if you are already running GIMP, either click <Toolbox>/Xtns/Script-Fu/Refresh Scripts, or just close and reopen GIMP.
4. If you have done this correctly, the scripts will appear in the menu under <Image>/Script-Fu/Layer Effects. If this menu is not there, try clicking <Toolbox>/Xtns/Script-Fu/Refresh Scripts. If it's still not there, make sure the file is in your scripts folder and that the filename ends with ".scm", not ".txt" or ".scm.txt" or something.