LiveQuartz is a simple and powerful photo editor for the Mac. It is based on non-destructive layers and filters. The layers are at the left and the filters are at the right of the window.
To edit a photo, just drag it into the window (or layers list) and it will be added as a new layer. LiveQuartz handles multi-touch trackpads.
The software is localized in 11 languages : English, Traditional Chinese, Simplifed Chinese, Danish, French, German, Italian, Japanese, Persian, Russian, and Spanish.