The function as.matrix.owin converts a window to a
logical matrux. It first converts the window x into a binary pixel mask
using as.mask. It then extracts the pixel entries
as a logical matrix.
The resulting matrix has entries that are
TRUE if the corresponding pixel is inside the window,
and FALSE if it is outside.
The function as.matrix is generic. The function
as.matrix.owin
is the method for windows (objects of class "owin").
Use as.im to convert a window to a pixel image.