Abstract. Retinex algorithms have been widely applied in many aspects of image processing. Based on the iterative Retinex algorithm, we propose an edge-preserving illumination estimation method. Inspired by the anisotropic diffusion, an edge-stopping function is introduced in the iterative computation. This modification enables the preservation of abrupt edges when computing the upper envelope of a given image. Based on the illumination-reflectance decomposition, a high-dynamic-range (HDR) radiance map can be easily tone-mapped to be a low-dynamic-range image by compressing the range of the estimated illumination. Artifacts are effectively suppressed using the proposed method. Meanwhile, we also propose a jumping-spiral iteration manner to improve the symmetry of the edge response. Experimental results show that the proposed tone mapping algorithm is very effective in reproducing HDR scenes, and has a better performance compared with some similar operators.
IntroductionThe dynamic range of natural scenes varies accordingly with different lighting conditions, from lower than 40 dB for ordinary uniformly lit scenes to higher than 120 dB for mixed indoor-outdoor scenes. However, human observers can cope well with such tremendous difference through local adaptation embedded in retina and cortex. Powered by sophisticated mechanisms, the human visual systems (HVS) can perceive a very large intensity range simultaneously, and even larger after long-time adaptation.1,2 On the other hand, the dynamic range of current image displays and other reproduction media is rather limited. Consequently, there is a great demand for high-fidelity dynamic range reduction in many media-related applications, such as remote imaging, medical imaging, virtual reality, and digital photography.