The invention discloses a calculating method for the size constancy of object image,belonging to the computer technology fields of vision, image recognition and mode discrimination. The sentience constancy is the most important and specific aspect in human perception world and the size constancy is one of the most important sentience constancy. The invention can make computer perceive the size constancy for each object of single 2D image as human, because it completely simulate the mechanism of size constancy for human visual system. The steps include: calculating the median line of image by the technique of sky detection, calculating the linear parameters in the direction of depth with most rapid change form the image bottom line to the midline in the part of image floor, calculating the apperceive depth in the middle of each image object, and calculating the constancy finally. |