[3] Haralick R.Digital step edges from zero crossing of second directional derivatives.IEEE Trans.PAMI,1984,6;1:58～68

[4] Hubel D H,Wiesel T N.Brain mechanisms of vision.Scientific American,1979,198;9:150～162

[5] Livingstone M S.Art,illusion and the vision system.Scientific American,1988,258;1:78～75