Effective image enhancement techniques for fog-affected indoor and outdoor images

Over the past decade, much research has been done to improve single-fog images. However, most of these have concentrated on outdoor environments and little has been done for indoor environments. In this study, an effective method of removing fog from images both indoors and outdoors is presented. A new single image enhancement approach is based on mixture of dark channel prior (DCP) and contrast limited adaptive histogram equalisation with discrete wavelet transform (CLAHE-DWT) algorithms. With the DCP algorithm using modified transmission map, the authors obtained fast processing speed and clean dehazed image without refining process. The CLAHE and DWT methods improved the contrast and sharpness of images. Finally, an enhanced image was produced by fusing the CLAHE and DWT images. To demonstrate the effectiveness of the proposed method, the authors performed objective image quality assessments, and so on. Through a variety of experiments for various indoor and outdoor images with fog, the proposed method was proven to be highly effective.