module DrawCommon
  def get_item_coords( item )
    coord = item.coords
    coord_array = []
    x = coord.shift
    y = coord.shift
    while x != nil
      coord_array.push( [x.to_f, y.to_f] )
      x = coord.shift
      y = coord.shift
    end
    coord_array
  end
  def set_coords( item, coord_array )
    eval "item.coords( #{ coord_array.flatten.join(',')} )"
  end
  def min_max( coord_array, index )
    temp = coord_array.collect{|c| c[index]}
    [ temp.min, temp.max ]
  end
  def center( coord_array )
    x_min, x_max = min_max( coord_array, 0 )
    y_min, y_max = min_max( coord_array, 1 )
    x = ( x_min + x_max ) / 2.0
    y = ( y_min + y_max ) / 2.0
    [x, y]
  end
  def axis_shift( coord_array, cntr )
    x0, y0 = cntr
    coord_array.collect{|c| [ c[0]-x0, c[1]-y0 ] }
  end
  def axis_shift_reverse( coord_array, cntr )
    x0, y0 = cntr
    coord_array.collect{|c| [ c[0]+x0, c[1]+y0 ] }
  end
  def linear_map( coord_array, matrix )
    cntr = center( coord_array )
    temp = axis_shift( coord_array, cntr )
    temp = temp.collect{|c|
      x = c[0]*matrix[0] + c[1]*matrix[1]
      y = c[0]*matrix[2] + c[1]*matrix[3]
      [x, y]
    }
    axis_shift_reverse( temp, cntr )
  end
  def linear_map_with_center( coord_array, matrix, cntr )
    temp = axis_shift( coord_array, cntr )
    temp = temp.collect{|c|
      x = c[0]*matrix[0] + c[1]*matrix[1]
      y = c[0]*matrix[2] + c[1]*matrix[3]
      [x, y]
    }
    axis_shift_reverse( temp, cntr )
  end
end