dilation
Morphological Dilation
Perform morphological dilation of a window, a line segment pattern or a point pattern
Usage
dilation(w, r, ...)
## S3 method for class 'owin':
dilation(w, r, \dots, polygonal=NULL, tight=TRUE)
## S3 method for class 'ppp':
dilation(w, r, \dots, polygonal=TRUE, tight=TRUE)
## S3 method for class 'psp':
dilation(w, r, \dots, polygonal=TRUE, tight=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 dilation.
- ...
- extra arguments passed to
as.mask
controlling the pixel resolution, if the pixel approximation is used. - polygonal
- Logical flag indicating whether to compute a polygonal
approximation to the dilation (
polygonal=TRUE
) or a pixel grid approximation (polygonal=FALSE
). Ignored ifgpclib
is disabled. - tight
- Logical flag indicating whether the bounding frame of the window
should be taken as the smallest rectangle enclosing the dilated region
(
tight=TRUE
), or should be the dilation of the bounding frame ofw
(tight=F
Details
The morphological dilation of a set $W$ by a distance $r > 0$ is the set consisting of all points lying at most $r$ units away from $W$. Effectively, dilation adds a margin of width $r$ onto the set $W$.
If polygonal=TRUE
then a polygonal approximation
to the dilation is computed.
If polygonal=FALSE
then a pixel approximation
to the dilation is computed from the distance map of w
.
The arguments "..."
are passed to as.mask
to control the pixel resolution.
When w
is a window, the default (when polygonal=NULL
)
is to compute a polygonal approximation if
w
is a rectangle or polygonal window, and to compute a
pixel approximation if w
is a window of type "mask"
.
Polygonal calculations require the gpclib
package which is subject to licence restrictions.
It is enabled by spatstat.options(gpclib=TRUE)
.
See licence.polygons
.
Value
- If
r > 0
, an object of class"owin"
representing the dilated region. Ifr=0
, the result is identical tow
.
See Also
Examples
w <- owin(c(0,1),c(0,1))
v <- dilation(w, 0.1)