Refocus
Introduction
During image processing operations such as scanning and scaling, images tend to get blurry. The blurred impression of these images is due to the fact that image pixels are averaged with their neighbors. Blurred images don't have sharp boundaries and look as though they have been taken with an unfocussed camera.Refocus is a plug-in for the Gimp (the GNU Image Manipulation Program). This plug-in attempts to "refocus" the image, using a technique called FIR Wiener filtering. The traditional technique for sharpening images is to use unsharp masking. Refocus generally produces better results than unsharp masking.
The plug-in comes with a preview that helps you select the best parameters.
Documentation
Instructions for installing and using the plug-in are included in the distribution in both html and pdf format. An online html version can be found here.Examples
The following images give you an impression of the effect of this plug-in.
The Wilber images at the top of this page show what the plug-in can do under optimal conditions. The image on the right is really the refocussed version of the image on the left.