Spatio-Temporal Retinex-like Envelope with Total Variation

Abstract

Many algorithms for spatial color correction of digital im- ages have been proposed in the past. Some of the most recently developed algorithms use stochastic sampling of the image in or- der to obtain maximum and minimum envelope functions. The envelopes are in turn used to guide the color adjustment of the en- tire image. In this paper, we propose to use a variational method instead of the stochastic sampling to compute the envelopes. A numerical scheme for solving the variational equations is out- lined, and we conclude that the variational approach is computa- tionally more efficient than using stochastic sampling. A percep-tual experiment with 20 observers and 13 images is carried out in order to evaluate the quality of the resulting images with the two approaches. There is no significant difference between the variational approach and the stochastic sampling when it comes to overall image quality as judged by the observers. However, the observed level of noise in the images is significantly reduced by the variational approach.