LightZone is a professional-level digital darkroom and photo
editor for Mac, Windows, and Linux. It includes RAW processing
and editing. Rather than using layers in the way that other
photo editors do, LightZone lets the user build up a stack of
tools which can be rearranged, readjusted, turned off and on,
and removed from the stack. It's a completely non-destructive
editor, where any of the tools can be re-adjusted or modified
later — even in a different editing session. A tool stack can
even be copied to a batch of photos at one time. LightZone
always operates in a 16-bit linear color space with the wide
gamut of ProPhoto RGB.