Pierre-e Gougelet, the author of XnView, created an addon to use RIOT in it’s well known viewer.
Now XnView users have RIOT integrated into their favorite viewer to be able to easily optimize pictures using RIOT.
XnView is the third well known application using RIOT, after IrfanView and GIMP.
The XnView addon is freely available in the download page.
It performed well during my tests.
The addon package ships with RIOT 0.4.1, but RIOT can be upgraded separately.
Pierre even sent me the source-code for this addon.
If anybody wants to modify it feel free to contact me and I will provide the addon’s source-code.