Images captured under bad weather conditions suffer from poor contrast and visibility. These effects are noticeable for haze, mist, fog, or dust storms. We have proposed a recovering method for images captured for several adverse weather conditions based on the RGB response ratio constancy under illuminant changes. This algorithm improves the visibility, contrast, and color in degraded images with low computational times. We obtain results similar to those from previously published deweathering methods but with no prior information about the image content or atmospheric parameters needed.

We have analyzed the changes in the color of objects in natural scenes due to atmospheric scattering according to changes in the distance of observation. Hook-shaped curves were found in the chromaticity diagram when the object moved from zero distance to long distances, where the object chromaticity coordinates approached the color coordinates of the horizon. This trend is the result of the combined effect of attenuation in the direct light arriving to the observer from the object and the airlight added during its trajectory. Atmospheric scattering leads to a fall in the object's visibility, which is measurable as a difference in color between the object and the background (taken here to be the horizon). Focusing on color difference instead of luminance difference could produce different visibility values depending on the color tolerance used. We assessed the cone-excitation ratio constancy for several objects at different distances. Affine relationships were obtained when an object's cone excitations were represented both at zero distance and increasing distances. These results could help to explain color constancy in natural scenes for objects at different distances, a phenomenon that has been pointed out by different authors.

Scattering and absorption in the atmosphere influence the colors of objects and can dramatically affect the way a landscape is perceived. We estimated, computationally, the chromatic losses in natural scenes as a function of the viewing distance for several atmospheric conditions. The study was based on models of real atmospheric scattering and absorption applied to hyperspectral data from natural images. It was found that exponential models could describe well the reduction in the number of perceived colors as a function of the viewing distance and the relationship between the coefficient reflecting the sum of the scattering and absorption effects and the viewing distance for a 50% reduction in colors. These results provide simple models to estimate the chromatic losses with viewing distance and can be used in applications of atmospheric optics concerned with visual simulations. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 341–346, 2014