text: import warnings
  import numpy as np
  from skimage import img_as_ubyte
  
  
  def make_colorbar(cmap, size=(12, 28), horizontal=True):
      """Make a colorbar from a colormap.
  
      Parameters
      ----------
      cmap : vispy.color.Colormap
          Colormap to create colorbar with.
      size : 2-tuple
          Shape of colorbar.
      horizontal : bool
          If True colobar is oriented horizontal, otherwise it is oriented
          vertical.
  
      Returns
      ----------
      cbar : array
          Array of colorbar.
      """
  
      if horizontal:
          input = np.linspace(0, 1, size[1])
          bar = np.tile(np.expand_dims(input, 1), size[0]).transpose((1, 0))
      else:
          input = np.linspace(0, 1, size[0])
          bar = np.tile(np.expand_dims(input, 1), size[1])
  
      # cmap.__getitem__ returns a vispy.color.ColorArray
      color_array = cmap[bar.ravel()]
      # the ColorArray.RGBA method returns a normalized uint8 array
      cbar = color_array.RGBA.reshape(bar.shape + (4,))
  
      return cbar
  