code: def _draw(self, color):
          
          width = self.winfo_width()
          height = self.winfo_height()
          self.delete("bg")
          self.delete("cross_h")
          self.delete("cross_v")
          del self.bg
          self.bg = tk.PhotoImage(width=width, height=height, master=self)
          self._fill()
          self.create_image(0, 0, image=self.bg, anchor="nw", tags="bg")
          self.tag_lower("bg")
          h, s, v = color
          x = v / 100.
          y = (1 - s / 100.)
          self.create_line(0, y * height, width, y * height, tags="cross_h",
                           fill="#C2C2C2")
          self.create_line(x * width, 0, x * width, height, tags="cross_v",
                           fill="#C2C2C2")
docs: Draw the gradient and the selection cross on the canvas.