This function generates a rectangular grid of locations in the plane,
tests whether each of these locations lies inside the
window `w`

, and stores the results as a binary pixel image
or `mask' (an object of class `"owin"`

, see `owin.object`

).

The most common use of this function is to approximate the shape
of another window `w`

by a binary pixel image. In this case,
we will usually want to have a very fine grid of pixels.

This function can also be used to generate a coarsely-spaced grid of
locations inside a window, for purposes such as subsampling
and prediction.

The grid spacing and location are controlled by the
arguments `eps`

, `dimyx`

and `xy`

,
which are mutually incompatible.

If `eps`

is given, then it determines the grid spacing.
If `eps`

is a single number,
then the grid spacing will be approximately `eps`

in both the \(x\) and \(y\) directions. If `eps`

is a
vector of length 2, then the grid spacing will be approximately
`eps[1]`

in the \(x\) direction and
`eps[2]`

in the \(y\) direction.

If `dimyx`

is given, then the pixel grid will be an
\(m \times n\) rectangular grid
where \(m, n\) are given by `dimyx[2]`

, `dimyx[1]`

respectively. **Warning:** `dimyx[1]`

is the number of
pixels in the \(y\) direction, and `dimyx[2]`

is the number
in the \(x\) direction.

If `xy`

is given, then this should be some kind of
data specifing the coordinates of a pixel grid. It may be

a list or structure containing elements `x`

and `y`

which are numeric vectors of equal length. These will be taken as
\(x\) and `y`

coordinates of the margins
of the grid. The pixel coordinates will be generated
from these two vectors.

a pixel image (object of class `"im"`

).

a window (object of class `"owin"`

) which is
of type `"mask"`

so that it contains pixel coordinates.

If `xy`

is given, `w`

may be omitted.

If neither `eps`

nor `dimyx`

nor `xy`

is given,
the pixel raster dimensions are obtained from
`spatstat.options("npixel")`

.

There is no inverse of this function. However, the function
`as.polygonal`

will compute a polygonal approximation
of a binary mask.