Enhancement of Color Images in Poor Visibility Conditions

Degradation of images by the atmosphere often restricts imaging applications to good visibility conditions. For example, when imaging the terrain from a forward-looking airborne camera, the atmospheric degradation causes both a loss in contrast and color information. Enhancement of such images is a difficult task due to the complexity in restoring both the luminance and chrominance while maintaining good color fidelity. One particular problem is the fact that the level of contrast loss depends strongly on wavelength; shorter wavelengths ie. blue are more effected. In this paper, a novel method is presented for the enhancement of color images. This method is based on the underlying physics of the degradation and the parameters required for enhancement are estimated from the image itself. The proposed method is tested using synthetic images to explore the limitations and reliability of the method under different visibility conditions. Enhancement is performed on real images taken using an airborne camera at a height of approximately 1000 meters in hazy conditions for which the visibility is approximately 10 kilometers. Significant improvements in terms of contrast, visible range and color fidelity are evident when compared to existing methods.