This figure illustrates the duality between open and close using nonsymmetrical structuring element.
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from morph import *
from MLab import fliplr
B_img=mmreadgray('blob1.tif')
B=mmimg2se(B_img)
mmshow(mmseshow(B))
y,x=indices((140,100))
F= mmbinary((2*x) < (y))
F=mmunion(F,fliplr(F))
F=mmpad(F,B)
mmshow(F)
C=mmero(F,B)
mmshow(C)
D=mmopen(F,B)
mmshow(D)
Fc= mmneg(F)
mmshow(Fc)
Bc=mmsereflect(B)
mmshow(mmseshow(Bc))
Cc=mmdil(Fc,Bc)
mmshow(Cc)
Dc=mmclose(Fc,Bc)
mmshow(Dc)