import mahotas
import mahotas.demos
from pylab import gray, imshow, show
import numpy as np

luispedro = mahotas.demos.load('luispedro')
luispedro = luispedro.max(2)
T = mahotas.otsu(luispedro)
lpbin = (luispedro > T)
gray()
eye = ~lpbin[112:180,100:190]
imshow(eye)
show()