Carol suggested that removing the interactive flag from png-save might help. If I do that, I get an error that directly says that a parameter is missing from png-save, which is at least perfectly understandable. The script, with Carol's suggestion commented out, is below. Anyone else with an answer, or with a good way to see where bugs in fu-scripts are in general? thanks, Dov (define (dl-png2transindexed2 file) (let* ( (img (car (file-png-load 1 file file) ) ) (d (car (gimp-image-active-drawable img))) ) (gimp-layer-add-alpha (car (gimp-image-get-active-layer img))) (gimp-by-color-select d '(255 255 255) 0 2 0 0 0 0) (gimp-edit-clear) (gimp-convert-indexed img 0 0 255 0 0 "") (file-png-save 1 img d file file 0 6 0 0 0 1 1) ; (file-png-save img d file file 0 6 0 0 0 1 1) ) ) (script-fu-register "dl-png2transindexed2" "<Toolbox>/Xtns/Script-Fu/png2transindexed2" "png2indexed2" "Dov Kruger& Elena Zagrai" "(c) 2004 Stevens Institute of Technology" "2004-02-25" "" SF-FILENAME "File" "file.png" )