Perceptual constancy is the most salient aspect of the way the world looks to us.It may enlighten some new ideas for many open issues of computer vision

such as automatic image understanding and image object recognition.Size constancy is one of the most important perceptual constancy.The key to correct size constancy perception of image object is to correctly estimate the depth of objects in the image.This paper introduces most of image depth cues used by human vision

and presents a method to resolve the fusion and confliction of these cues.Then we propose a model to implement size constancy computation of image objects.Experimental results suggest that our model can work reasonably well.In addition

this paper sets a good example for applying visual psychology to resolving computer vision problems.