I have scanned some old pictures. The uneven surface resulted in white wave-shaped stripes in the scan. Is there any way I can remove them in Gimp (pretty inexperienced user) or other free tool? Any help would be much appreciated! Petr
With some scanners, you scan the image twice, and rotate the image by 180° for the second scan. Then in Gimp you load both images, rotate one of them, align them and set the top one to "darken only".
However this requires a very accurate scanner, and many scanners have a lateral distortion that makes such images too different to overlap.