Visibility restoration of lake crater hazy image based on dark channel prior

摘要

Volcanic degassing is often happened on top of Mt Kelud. One of the indicator of its activity is the changing of the lake color. An observation has been conducted for years to watch the condition of the lake using a CCTV camera, the volcanology officer. Since it is located on top of the mountain, weather condition always change from clear, cloudy, or hazy. Obviously, the vision of the camera is limited or even blocked by the haze or fog. In this paper, we use a haze removal technique based on dark channel prior. The problem comes up because the airlight hard to estimate on non-sky area. By comparing different size of the patches, we found that, in our case, for smaller patch the airlight closes to its maximum limit. This airlight almost equals to sky region. For image improvement, we use guided image filter to maintain image quality after transmission map estimation. According to FADE (Fog Aware Density Evaluator) the fog density estimated to be 0.6333 and SSIM (Structural Similarity) 0.9977.