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 the grid spacing will be
approximately eps in both the $x$ and $y$ directions.
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 a structure
containing two elements x and y which are the
vectors of $x$ and y coordinates of the margins
of the grid. The pixel coordinates will be generated
from these two vectors. In this case 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.