Sub saveBinaryPBM (handle As Long, filename As String)
    Dim imgwidth As Long
    Dim imgheight As Long
    Dim oldsource As Long
    Dim fid As String
    Dim imgdim As String
    Dim y As _Unsigned Long
    Dim x As _Unsigned Long
    Dim c As _Byte

    oldsource = _Source
    _Source handle
    imgwidth = _Width(handle)
    imgheight = _Height(handle)
    Open filename For Binary As #1
    fid = "P4" + Chr$(10)
    Put #1, , fid
    fid = "# Created with QB64" + Chr$(10)
    Put #1, , fid
    imgdim = LTrim$(Str$(imgwidth) + Str$(imgheight)) + Chr$(10)
    Put #1, , imgdim
    Dim o As _Unsigned _Byte
    For y = 0 To imgheight - 1
        For x = 0 To imgwidth - 1
            c = (Point(x, y) = _RGB(0, 0, 0))
            If c <> 0 Then
                o = _SetBit(o, 7 - (x Mod 8))
            Else
                o = _ResetBit(o, 7 - (x Mod 8))
            End If
            If x Mod 8 = 7 Then
                Put #1, , o
            End If
        Next
    Next
    Close #1
End Sub