def ff_neighbour(col, row, direction)
      case direction
        when :north then return col, row-1
        when :south then return col, row+1
        when :east  then return col+1, row
        when :west  then return col-1, row
      end
    end
def ff_neighbour(col, row, direction)
      case direction
        when :north then return col, row-1
        when :south then return col, row+1
        when :east  then return col+1, row
        when :west  then return col-1, row
      end
    end
Gives the neighbour column and row indices based on a specified origin
 point and a direction of travel. This private method is used by
 flood_fill() and its dependency; ff_find_border()
 :east => to the right when looking at an array image printout on the screen

 @param [Integer] col the column index of the origin
 @param [Integer] row the row index of the origin
 @param [Symbol] direction the direction of travel (:east, :west, :north, :south)
 @return [Array<Integer>] column and row pixel indices