subroutine dilation(x,y,n,m)
  implicit none
  integer :: i,j,n,m
  integer x(n,m)
  integer y(n,m)
!f2py intent(out) y
!f2py intent(in) x

  y=x
  do j=2,m-1
    do i=2,n-1
      y(i,j)=maxval(x(i-1:i+1,j-1:j+1))
    end do
  end do
end subroutine dilation

subroutine erosion(x,y,n,m)
  implicit none
  integer :: i,j,n,m
  integer x(n,m)
  integer y(n,m)
!f2py intent(out) y
!f2py intent(in) x

  y=x
  do j=2,m-1
    do i=2,n-1
      y(i,j)=minval(x(i-1:i+1,j-1:j+1))
    end do
  end do
end subroutine erosion

subroutine sort(a,n) !GnomeSort
  implicit none
  integer :: n,i,temp
  integer :: a(n)

  i=1
  temp=1

  do while (i<n)
    if (a(i)>a(i+1)) then
      temp=a(i)
      a(i)=a(i+1)
      a(i+1)=temp
      if (i>1) then
        i=i-1
      else
        i=i+1
      end if
    else
      i=i+1
    end if
  end do

end subroutine sort

subroutine median(x,y,m,n) ! 3x3 Medianfilter
  implicit none
  integer :: i,j,n,m
  integer x(n,m)
  integer y(n,m)
  integer z(9)
  logical mask(3,3)
  mask=.true.

!f2py intent(out) y
!f2py intent(in) x

  y=x
  do j=2,m-1
    do i=2,n-1
      z=pack(x(i-1:i+1,j-1:j+1),mask)
      call sort(z,9)
      y(i,j)=z(5)
    end do
  end do

end subroutine median