**Yutaro Iwamoto, Naoaki Hashimoto and Yen-Wei Chen \***

College of Information Science and Engineering, Ritsumeikan University, Shiga 525-8577, Japan; yiwamoto@fc.ritsumei.ac.jp (Y.I.); naoaki111.de@gmail.com (N.H.)

**\*** Correspondence: chen@is.ritsumei.ac.jp

Received: 16 December 2019; Accepted: 4 February 2020; Published: 9 February 2020

**Abstract:** This study proposes real-time haze removal from a single image using normalised pixel-wise dark-channel prior (DCP). DCP assumes that at least one RGB colour channel within most local patches in a haze-free image has a low-intensity value. Since the spatial resolution of the transmission map depends on the patch size and it loses the detailed structure with large patch sizes, original work refines the transmission map using an image-matting technique. However, it requires high computational cost and is not adequate for real-time application. To solve these problems, we use normalised pixel-wise haze estimation without losing the detailed structure of the transmission map. This study also proposes robust atmospheric-light estimation using a coarse-to-fine search strategy and down-sampled haze estimation for acceleration. Experiments with actual and simulated haze images showed that the proposed method achieves real-time results of visually and quantitatively acceptable quality compared with other conventional methods of haze removal.

**Keywords:** haze removal; dark channel; atmospheric-light estimation; coarse-to-fine search strategy
