Photivo is a free and open-source (GPL3) photo processor. It handles your RAW files and your bitmap files (TIFF, JPEG, BMP, PNG, and many more) in a non-destructive 16-bit processing pipe with gimp workflow integration batch mode.
Photivo tries to provide the best algorithms available, even if this implies some redundancy. So, to my knowledge, it offers the most flexible and powerful denoise, sharpens, and local contrast (fake HDR) algorithms in the open-source world.
16-bit internal processing, color managed with LCMS2.
Gimp workflow integration (import and export)
Works with RAWs and Bitmaps (8 bit bitmaps are transformed and processed with 16 bit, which usually gives better results).
CA correction, Green equilibration, line denoise, badpixel reduction, wavelet denoise, median filters on RAW data.
Perspective correction (tilt and turn), distorsion and geometry (also defish) correction