1. An image correction method, comprising: an identifying step of identifying each pixel in an image as one of a foreground pixel and a background pixel; a background filling step of estimating a brightness of a background corresponding to a foreground pixel based on the brightness and a gradient of the brightness of background pixels adjacent to the foreground pixel to fill the background located in a position of the foreground pixel to obtain a background illumination map of the image according to filled backgrounds along with background pixels; and a correcting step of correcting the image based on the brightness of each pixel in the image and the background illumination map.