spatstat (version 1.16-1)

closing: Morphological Closing

Description

Perform morphological closing of a window, a line segment pattern or a point pattern.

Usage

```closing(w, r, ...)
## S3 method for class 'owin':
closing(w, r, \dots, polygonal=NULL)
## S3 method for class 'ppp':
closing(w, r, \dots, polygonal=TRUE)
## S3 method for class 'psp':
closing(w, r, \dots, polygonal=TRUE)```

Arguments

w
A window (object of class `"owin"` or a line segment pattern (object of class `"psp"`) or a point pattern (object of class `"ppp"`).
r
positive number: the radius of the closing.
...
extra arguments passed to `as.mask` controlling the pixel resolution, if a pixel approximation is used
polygonal
Logical flag indicating whether to compute a polygonal approximation to the erosion (`polygonal=TRUE`) or a pixel grid approximation (`polygonal=FALSE`).

Value

• If `r > 0`, an object of class `"owin"` representing the closed region. If `r=0`, the result is identical to `w`.

Details

The morphological closing (Serra, 1982) of a set \$W\$ by a distance \$r > 0\$ is the set of all points that cannot be separated from \$W\$ by any circle of radius \$r\$. That is, a point \$x\$ belongs to the closing \$W*\$ if it is impossible to draw any circle of radius \$r\$ that has \$x\$ on the inside and \$W\$ on the outside. The closing \$W*\$ contains the original set \$W\$.

For a small radius \$r\$, the closing operation has the effect of smoothing out irregularities in the boundary of \$W\$. For larger radii, the closing operation smooths out concave features in the boundary. For very large radii, the closed set \$W*\$ becomes more and more convex.

The algorithm applies `dilation` followed by `erosion`.

References

Serra, J. (1982) Image analysis and mathematical morphology. Academic Press.

`opening` for the opposite operation.

`dilation`, `erosion` for the basic operations. `owin`, `as.owin` for information about windows.

Examples

Run this code
``````data(letterR)
v <- closing(letterR, 0.25, dimyx=256)
plot(v, main="closing")