Sharpening tool, uses blurred mask. Sharpness is modified with few sliders that work like a kind of equalizer. User can control blurring parameters (radius and treshold for selective blur mask). It provides 4 types of output: Sharpenned image, mask, split/comparision mode and mask-to-img differences.
Brightness of image can be affected by levels-like tool that works indirectly - via the mask.
See attached screenshot for more info.
Plugin is multithreaded.
Downloads (source code with instructions for linux) and few sample images http://code.google.com/p/aumask/wiki/Introduction.
Any comments and feature requests welcomed.