Local Proximity for Enhanced Visibility in Haze

Abstract

Atmospheric medium often constrains the visibility of outdoor scenes due to scattering of light rays. This causes attenuation in the irradiance reaching the imaging device along with an additive component to render a hazy effect in the image. The visibility is further reduced for poorly illuminated scenes. The attenuation becomes wavelength dependent in underwater scenario, causing undesired color cast along with hazy effect. In order to suppress the effect of different atmospheric/underwater conditions such as haze and to enhance the contrast of such images, we reformulate local haziness in a generalized manner. The parameters are estimated by harnessing the similarity of patches within a local neighborhood. Unlike existing methods, our approach is developed based on the assumption that for outdoor scenes the depth of patches changes gradually in a local neighborhood surrounding the patch. This change in depth can be approximated by patch similarity in that neighborhood. As the attenuation in irradiance of an image in presence of atmospheric medium relies on the depth of the scene, the coefficients related to the attenuation are estimated from the weights of patch similarity. The additive haze effect is deduced using non-local mean of the patch. Our experimental results demonstrate the effectiveness of our approach in reducing the haze component as well as in enhancing the image under different conditions of haze (daytime, nighttime, and underwater).