\name{area.owin}
\alias{area.owin}
\alias{volume.owin}
\title{Area of a Window}
\description{
  Computes the area of a window 
}
\usage{
 area.owin(w)
 \method{volume}{owin}(x)
}
\arguments{
  \item{w}{A window, whose area will be computed.
    This should be an object of class \code{\link{owin}},
    or can be given in any format acceptable to \code{\link{as.owin}()}.
  }
  \item{x}{Object of class \code{\link{owin}}}
}
\value{
  A numerical value giving the area of the window. 
}
\details{
  If the window \code{w} is of type \code{"rectangle"} or \code{"polygonal"},
  the area of this rectangular window is computed by analytic geometry.
  If \code{w} is of type \code{"mask"} 
  the area of the discrete raster approximation of the window is
  computed by summing the binary image values and adjusting for
  pixel size.

  The function \code{volume.owin} is identical to \code{area.owin}
  except for the argument name. It is a method for the generic function
  \code{volume}.
}
\seealso{
  \code{\link{perimeter}},
  \code{\link{diameter.owin}},
  \code{\link{owin.object}},
  \code{\link{as.owin}}
}
\examples{
  w <- unit.square()
  area.owin(w)
       # returns 1.00000

  k <- 6
  theta <- 2 * pi * (0:(k-1))/k
  co <- cos(theta)
  si <- sin(theta)
  mas <- owin(c(-1,1), c(-1,1), poly=list(x=co, y=si))
  area.owin(mas)
      # returns approx area of k-gon
  
  mas <- as.mask(square(2), eps=0.01)
  X <- raster.x(mas)
  Y <- raster.y(mas)
  mas$m <- ((X - 1)^2 + (Y - 1)^2 <= 1)
  area.owin(mas)
       # returns 3.14 approx     

}
\author{Adrian Baddeley
  \email{Adrian.Baddeley@csiro.au}
  \url{http://www.maths.uwa.edu.au/~adrian/}
  and Rolf Turner
  \email{r.turner@auckland.ac.nz}
}
\keyword{spatial}
\keyword{math}