Delaboratory is a color correction utility for digital images.
It features:

 - Floating point precision (not 8-bit like Gimp, not 16-bit
   like most raw processors)
 - Native support for multiple colorspaces (sRGB, ProPhoto RGB,
   LAB, CMYK, LCH, HSL, HSV, BW)
 - Non-destructive editing (adjustment layers)
 - KISS design, realtime preview
 - Basic operations: CMYK curves, CMYK levels, RGB curves, RGB
   levels, white balance in LAB, saturation in LAB, LAB curves,
   BW curve, HSV equalizer, LCH equalizer, recover shadows/highlights,
   vignette, local contrast, LAB/BW/RGB/CMYK gradients
 - Expert operations: levels, curves, equalizer, exposure, saturation,
   white balance, fill, tone, local contrast, auto_dodge/auto_burn,
   sharpen, vignette, gradient, gaussian blur, recover highlights,
   recover shadows, channel mixer, high pass, c2g, copy
 - Many blend modes (multiply, screen, overlay, inverted overlay,
   dodge, burn, add, grain extract, grain merge, sub, difference,
   darken, lighten), color/luminosity blending for RGB and CMYK
 - RAW support (via dcraw), up to 5 color samplers, histograms and color
   matrices, etc.

WWW: https://bsdforge.com/projects/graphics/delaboratory/