Research On Defogging Method Of The Natural Scene Image

In recent years,many parts of our country have been affected by the varying degrees of haze,which makes our daily life inconvenience,especially in the intelligent transportation,and aerospace field.Because of the existence of fog or haze,the quality of the images captured in the outdoor has some serious decline,such as lack of contrast,color blur and so on,which is not only disadvantageous for the visual experience of our eyes,but also makes the image features extraction great challenging.Therefore,the defogging of fog images have always been a hot topic in computer vision,and has wide application prospect.In this thesis,the defogging method of the natural scene image was studied,and the main research contents as follows:Firstly,the principle of atmospheric scattering was introduced,especially the derivation and establishment of the atmospheric scattering model.The basic characteristics of the fog image was analyzed,which establishes a theoretical foundation for defogging study.Secondly,two kinds of foggy image restoration methods with physical models were studied,which are based on atmospheric light curtain defogging method and based on optimized contrast enhancement defogging method respectively.The two shortcomings of the former method were analyzed: the parameters are not easy to adjust and the median filter can not keep the edges strong.For the latter method,the effectiveness and the stability were fully highlighted.The performance of image restoration of the two defogging methods were evaluated from two different perspectives,such as the subjective human vision and the objective quantitative analysis.Moreover,these two proposed methods were compared with the traditional classical methods.Experimental results show that the computation speed of two proposed methods can reach the real-time,and the image qualities after restoration,such as the edge of the details and the color fidelity,have been greatly improved.Finally,the famous image defogging method based on the dark channel prior theory was introduced.The advantages and the principles of this method were discussed in detail.Then,the shortcomings of this method was analyzed,and an improved defogging method was proposed based on the dark channel prior theory.The soft matting is replaced by the guided filtering in the proposed method,so that the computation speed has been greatly improved.Moreover,for the failure of the He's method defogging the sky area,the operation on the sky area defogging was proposed.Then qualitative analysis and quantitative assessment was made between the proposed method and the classical methods.Experiments show that the proposed method has a very good computation speed,and can solve many problems in defogging which cannot be overcome by the classical methods.