The present invention concerns a method for assigning a pixel to one of a foreground pixel set and a background pixel set. In this method, if a first condition is met the pixel is assigned to the background pixel set , and if the first condition is not met and a second condition is met, the pixel is assigned to the foreground pixel set. The method comprises a step ( S100 ) of calculating a probability that the pixel belongs to a foreground-relevant object according to a semantic segmentation algorithm, the first condition is that this probability that the pixel belongs to a foreground relevant object does not exceed a first predetermined threshold, and the second condition is that a difference between this probability that the pixel belongs to a foreground relevant object and a baseline probability for the pixel equals or exceeds a second predetermined threshold.