Research On Optimal Transmission Estimation Via Fog Density Perception For Efficient Single Image Defogging

Images captured in fog,mist and haze weather condition often suffer from poor visibility and low contrast and color fidelity.Hence,image defogging have captured much attention.In this paper,we aim to develop a novel image defogging algorithm by directly predicting fog density of recovered images rather than adopting prior assumption or constraints.The main contributions of this paper are summarized as follow:This paper proposes a novel fog density evaluator via statistical features of foggy images to evaluate fog level.After analyzing thirteen fog-relevant via mutual information coefficient and pearson correlation coefficient,this paper adopts three fog-relevant statistical features derived from foggy images,and further develops a simple fog density evaluator(SFDE)by creating a linear combination of these fog-relevant features.This proposed evaluator can efficiently perceive the fog density of a single image without reference to a corresponding fog-free image and has a low computational load compared with an existing method.A physics-based mathematical relationship between the transmission and the fog density score of the recovered image is developed via SFDE,thus image defogging can be posed as a minimization problem on the fog density score of the recovered image.Two optimal transmission models,called an Optimal Transmission model via SFDE(OTSFDE)and a Simpler Optimal Transmission models via SFDE(SOTSFDE),are present to determine the key transmission map for efficient fog removal.Compared to OTSFDE,SOTSFDE has low computational complexity with slight performance degradation.Experimental results demonstrate that the proposed algorithms can effectively remove fog and are not confin ed by any assumptions or constraints,both quantitatively and qualitatively,compared with some existing algorithms.This paper introduced a kind of scatter model of nighttime scene and realizes nighttime image dehazing via OTSFDE and SOTSFDE.The scatter model of nighttime scene is a linear combination of three terms: the direct transmission,airlight and glow.Based on the model,First,the effect of the glow in the image is reduced to achieve a nighttime image which consist of direct transmission and airlight only.Then,the OTSFDE and SOTSFDE are used to dehaze the nighttime haze image.Experimental results demonstrate the effectiveness of our correction method on a number of examples and compare our results with existing daytime and nighttime dehazing methods' results.