1. An apparatus to classify pixels in an input image, the apparatus comprising: at least one processing unit coupled to a memory; a first confidence determination unit configured to determine a first confidence of each pixel in the pixels of the input image that represents a probability that a given pixel belongs to a particular class, wherein each pixel belongs to each of a plurality of predetermined classes; a detection unit configured to acquire, by using a detector to detect a particular class for a pixel among the plurality of predetermined classes, detection results used as an indication of the particular class to which each pixel in the input image belongs among the plurality of predetermined classes; an updating unit configured to update the first confidences according to the acquired detection results of the detector; and a class determination unit configured to determine, according to the updated first confidences, the class to which each pixel in the input image belongs among the plurality of predetermined classes, wherein at least one of the first confidence determination unit, the detection unit, the updating unit, and the class determination unit are implemented by the at least one processing unit.