On Edge-Aware Path-based Color Spatial Sampling for Retinex: from Termite Retinex to Light Energy-driven Termite Retinex

Retinex theory estimates the human color sensation at any observed point by correcting its color based on the spatial arrangement of the colors in proximate regions. In this work, we revise two recent path-based, edge-aware Retinex implementations: Termite Retinex (TR) and Energy-driven Termite Retinex (ETR). As the original Retinex implementation, TR and ETR scan the neighborhood of any image pixel by paths and rescale their chromatic intensities by intensity levels computed by re-working the colors of the pixels on the paths. Our interest to TR and ETR is due to their novel, content based scanning scheme, that uses the image edges to define the paths and exploits a swarm intelligence model for guiding the spatial exploration of the image. The exploration scheme of ETR has been showed to be particularly effective: its paths are local minima of an energy functional, designed to favor the sampling of image pixels highly relevant to color sensation. Nevertheless, since its computational complexity makes ETR poorly practicable, here we present a light version of it, named named Light Energy-driven Termite Retinex, and obtained from ETR by implementing a modified, optimized minimization procedure and by exploiting parallel computing.