Constrained pseudo-Brownian motion and its application to image enhancement.

Brownian motion is a random process that finds application in many fields, and its relation to certain color perception phenomena has recently been observed. On this ground, Marini and Rizzi developed a retinex algorithm based on Brownian motion paths. However, while their approach has several advantages and delivers interesting results, it has a high computational complexity. We propose an efficient algorithm that generates pseudo-Brownian paths with a very important constraint: we can guarantee a lower bound to the number of visits to each pixel, as well as its average. Despite these constraints, we show that the paths generated have certain statistical similarities to random walk and Brownian motion. Finally, we present a retinex implementation that exploits the paths generated with our algorithm, and we compare some images it generates with those obtained with the McCann99 and Frankle and McCann's algorithms (two multiscale retinex implementations that have a low computational complexity). We find that our approach causes fewer artifacts and tends to require a smaller number of pixel comparisons to achieve similar results, thus compensating for the slightly higher computational complexity.