HP: http://free.pages.at/easyfilter/curves.html
DL: http://free.pages.at/easyfilter/smartcurve.zip
English and German version icluded in ZIP file
Installation in xnView:
Make sure that an image is displayed in XnView.
Then select Filter > Adobe-Photoshop-Plug-Ins > Adobe 8BF filters.
In the appearing dialog press the "Config" and then the "Add" button and choose
the folder where you installed SmartCurve. Press OK. SmartCurve will now appear
in the list on the left. To run SmartCurve double click on the SmartCurve
entry or select it and press the "Start" button.