A nonlocal variational formulation for the improvement of tone mapped images

Due to technical limitations, common display devices can only reproduce images having a low range of intensity values (dynamic range). As a consequence, the dynamic range of images encoding real world scenes, which is large, has to be compressed in order for them to be reproduced on a common display, and this technique is called tone mapping. Because there is no ground truth to compare with, evaluation of a tone mapped image has to be done by comparing with the original high dynamic range image. As standard metrics based on pixel-wise comparisons are not suitable for comparing images of different dynamic range, non local perceptual based metrics are commonly used. We propose a general method for optimizing tone mapped images with respect to a given non local metric. In particular, if the metric is perceptual, i.e. it involves perceptual concepts, we provide an adequate minimization strategy. Experiments on a particular perceptual metric tested with different tone mapped images provided by several tone mapping operators validate our approach.This work was supported by European Research Council, Starting Grant ref. 306337, and by Spanish grants ref. TIN2011-15954-E and ref. TIN2012-38112

A nonlocal variational formulation for the improvement of tone mapped images

Due to technical limitations, common display devices can only reproduce images having a low range of intensity values (dynamic range). As a consequence, the dynamic range of images encoding real world scenes, which is large, has to be compressed in order for them to be reproduced on a common display, and this technique is called tone mapping. Because there is no ground truth to compare with, evaluation of a tone mapped image has to be done by comparing with the original high dynamic range image. As standard metrics based on pixel-wise comparisons are not suitable for comparing images of different dynamic range, non local perceptual based metrics are commonly used. We propose a general method for optimizing tone mapped images with respect to a given non local metric. In particular, if the metric is perceptual, i.e. it involves perceptual concepts, we provide an adequate minimization strategy. Experiments on a particular perceptual metric tested with different tone mapped images provided by several tone mapping operators validate our approach.This work was supported by European Research Council, Starting Grant ref. 306337, and by Spanish grants ref. TIN2011-15954-E and ref. TIN2012-38112