Sylvester spectral filter and tone mapping

We propose a flexible IGS tone mapping framework that works in three domains: image (I), gradient(G), and spectrum (S). Since illumination non-uniformity is known to be one of the main difficulties in tone reproduction (even for moderate dynamic range images), we use homomorphic Sylvester spectral filtering in the gradient domain to reduce lighting contrast, while avoid serious artifacts (such as halos and hollows). Furthermore, we show that by using the cumulative distribution function of the gamma distribution as the tone curve, the contrast and brightness of tone reproduction can be effectively controlled. The main motivation for this strategy is to deal with the issues caused by global illumination shading for high-dynamic-range images so that the user can adjust a few parameters to achieve the desired level of contrast in the final images, but does not require individual manual adjustment on a per-image basis. Our framework takes advantage of the efficiency and effectiveness of spectral domain filtering for dealing with these issues caused by global illumination shading.