1. An image defogging method, comprising: acquiring minimum intensity values of every pixel in a fogging image, and constructing a pixel-based dark channel map of the fogging image by using the acquired minimum intensity values of all pixels; acquiring minimum intensity values of local areas centered on every pixel in the fogging image, and constructing a local area-based dark channel map of the fogging image by using the acquired minimum intensity values of all local areas; acquiring a final dark channel map of the fogging image by using the pixel-based dark channel map and the local area-based dark channel map; acquiring intensity values of R, G, B channels of a pixel having a maximum grey value of all pixels in an area, which is covered by a brightest area of a predetermined size in the local area-based dark channel map, in a fogging map, as R, G, B components of an air light value of the fogging image; acquiring a transmission map of the fogging image by using the final dark channel map, a maximum value of the R, G, B components of the air light value, and a defogging parameter; and acquiring intensity values of R, G, B channels of every pixel in a defogged image by using the transmission map, the air light value, and the intensity values of the R, G, B channels of every pixel in the fogging image.