```
# rectangular
a <- owin(c(0,1),c(0,1))
b <- owin(c(-1,2),c(-1,2))
bmina <- complement.owin(a, frame=b)
# polygonal
data(demopat)
w <- demopat$window
outside <- complement.owin(w)
# mask
w <- as.mask(demopat$window)
outside <- complement.owin(w)
```

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