spatstat.geom (version 3.2-8)

owin2mask: Convert Window to Binary Mask under Constraints

Description

Converts a window (object of class "owin") to a binary pixel mask, with options to require that the inside, outside, and/or boundary of the window should be completely covered.

Usage

owin2mask(W,
         op = c("sample", "notsample",
                "cover", "inside",
                "uncover", "outside",
                "boundary",
                "majority", "minority"),
         ...)

Value

A mask (object of class "owin" of type "mask"

representing a binary pixel mask).

Arguments

W

A window (object of class "owin").

op

Character string (partially matched) specifying how W should be converted to a binary pixel mask.

...

Optional arguments passed to as.mask to determine the pixel resolution.

Author

Adrian Baddeley .

Details

This function is similar to, but more flexible than, as.mask. It converts the interior, exterior, or boundary of the window W to a binary pixel mask.

• If op="sample" (the default), the mask consists of all pixels whose centres lie inside the window W. This is the same as using as.mask.

• If op="notsample", the mask consists of all pixels whose centres lie outside the window W. This is the same as using as.mask followed by complement.owin.

• If op="cover", the mask consists of all pixels which overlap the window W, wholly or partially.

• If op="inside", the mask consists of all pixels which lie entirely inside the window W.

• If op="uncover", the mask consists of all pixels which overlap the outside of the window W, wholly or partially.

• If op="outside", the mask consists of all pixels which lie entirely outside the window W.

• If op="boundary", the mask consists of all pixels which overlap the boundary of the window W.

• If op="majority", the mask consists of all pixels in which at least half of the pixel area is covered by the window W.

• If op="minority", the mask consists of all pixels in which less than half of the pixel area is covered by the window W.

These operations are complementary pairs as follows:

"notsample"	is the complement of	"sample"
"uncover"	is the complement of	"inside"
"outside"	is the complement of	"cover"
"minority"	is the complement of	"majority"

They also satisfy the following set relations:

"inside"	is a subset of	"cover"
"outside"	is a subset of	"uncover"
"boundary"	is a subset of	"cover"
"boundary"	is a subset of	"uncover"

The results of "inside", "boundary" and "outside" are disjoint and their union is the entire frame.

Theoretically "sample" should be a subset of "cover", "notsample" should be a subset of "uncover", "inside" should be a subset of "majority" and "outside" should be a subset of "minority", but these could be false due to numerical error in computational geometry.

See Also

as.mask

Examples

  W <- Window(chorley)
  opa <- par(mfrow=c(2,5))
  plot(as.mask(W, dimyx=10), col="grey", main="sample")
  plot(W, add=TRUE, lwd=3, border="red")  
  plot(owin2mask(W, "ma", dimyx=10), col="grey", main="majority")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "i", dimyx=10), col="grey", main="inside")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "c", dimyx=10), col="grey", main="cover")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "b", dimyx=10), col="grey", main="boundary")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(as.mask(complement.owin(W), dimyx=10), col="grey",
       main="notsample")
  plot(W, add=TRUE, lwd=3, border="red")  
  plot(owin2mask(W, "mi", dimyx=10), col="grey", main="minority")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "o", dimyx=10), col="grey", main="outside")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "u", dimyx=10), col="grey", main="uncover")
  plot(W, add=TRUE, lwd=3, border="red")
  plot(owin2mask(W, "b", dimyx=10), col="grey", main="boundary")
  plot(W, add=TRUE, lwd=3, border="red")
  par(opa)