Test

class Window_Base
  alias draw_actor_hp_original draw_actor_hp
  def draw_actor_hp(actor, x, y, width = 144, height = 15)
    bg = Color.new(  0,   0,   0, 160)
    c1 = Color.new(255,   0,   0, 0)
    c2 = Color.new(255, 255,   0, 160)
    self.contents.fill_rect(x, y, width, height, bg)
    width2 = width * actor.hp / actor.maxhp
    gradient(x + 1, y + 1, width2 - 2, height - 2, c1, c2)
    draw_actor_hp_original(actor, x, y, width)
  end

  alias draw_actor_sp_original draw_actor_sp
  def draw_actor_sp(actor, x, y, width = 144, height = 15)
    bg = Color.new(  0,   0,   0, 160)
    c1 = Color.new(  0,   0, 255, 0)
    c2 = Color.new(  0, 255, 255, 160)
    self.contents.fill_rect(x, y, width, height, bg)
    width2 = width * actor.sp / actor.maxsp
    gradient(x + 1, y + 1, width2 - 2, height - 2, c1, c2)
    draw_actor_sp_original(actor, x, y, width)
  end

  def gradient(x, y, width, height, c1, c2)
    for i in 1..width
      x2 = x + i - 1
      r = c1.red * (width - i) / width + c2.red * i / width
      g = c1.green * (width - i) / width + c2.green * i / width
      b = c1.blue * (width - i) / width + c2.blue * i / width
      a = c1.alpha * (width - i) / width + c2.alpha * i / width
      self.contents.fill_rect(x2, y, 1, height, Color.new(r, g, b, a))
    end
  end
end