smart-sharpen2 v0.3b is my modified version of John Hall’s sharpening script from the GIMP FAQ site.

Changes:

• Dialogue to modify sharpening and edge-detection parameters.
• Optional despeckling applied to the layer mask prior to edge-detection; this removes a lot of the grain on scanned negatives and thus avoids sharpening it along with everything else. (The grain is still visible on the image, it just looks better without sharpening.) You may still wish to adjust the black, white and mid points for the mask in Levels.
• Handle both RGB and grayscale images, with optimisations for grayscale (copies rather than decomposes the image, since the Value component is the same in this case).

Otherwise, the script is substantially the same as the original. I’ve offered the changes to John, but he prefers his version to remain non-interactive for batch processing and there’s no way to run the same script in different ways. Hence the modified one is here for those who want more control over the process.