Distance Map of Window
Computes the distance from each pixel to the nearest point in the given window.
- A window (object of class
- Arguments passed to
as.maskto control pixel resolution.
The ``distance map'' of a window $W$ is the function
$f$ whose value
f(u) is defined for any two-dimensional
location $u$ as the shortest distance from $u$ to $W$.
This function computes the distance map of the window
and returns the distance map as a pixel image. The greyscale value
at a pixel $u$ equals the distance from $u$ to the nearest
Additionally, the return value
has an attribute
"bdry" which is
also a pixel image. The grey values in
"bdry" give the
distance from each pixel to the bounding rectangle of the image.
If the window
X is not already a pixellated window
(a binary image mask), it is converted into one. The arguments
... control the pixel resolution in this case, but will
otherwise be ignored.
This function is a method for the generic
- A pixel image (object of class
"im") whose greyscale values are the values of the distance map. The return value has an attribute
"bdry"which is a pixel image.
data(letterR) U <- distmap(letterR) plot(U) plot(attr(U, "bdry"))