code: # ----------------------------------------------------------------------------
  # -                        Open3D: www.open3d.org                            -
  # ----------------------------------------------------------------------------
  # The MIT License (MIT)
  #
  # Copyright (c) 2018-2021 www.open3d.org
  #
  # Permission is hereby granted, free of charge, to any person obtaining a copy
  # of this software and associated documentation files (the "Software"), to deal
  # in the Software without restriction, including without limitation the rights
  # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  # copies of the Software, and to permit persons to whom the Software is
  # furnished to do so, subject to the following conditions:
  #
  # The above copyright notice and this permission notice shall be included in
  # all copies or substantial portions of the Software.
  #
  # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  # IN THE SOFTWARE.
  # ----------------------------------------------------------------------------
  
  import numpy as np
  import matplotlib.pyplot as plt
  import matplotlib.image as mpimg
  
  import open3d as o3d
  #conda install pillow matplotlib
  
  if __name__ == "__main__":
  
      print("Testing image in open3d ...")
      print("Convert an image to numpy")
      sample_image = o3d.data.JuneauImage()
      x = o3d.io.read_image(sample_image.path)
      print(np.asarray(x))
      print(
          "Convet a numpy image to o3d.geometry.Image and show it with DrawGeomtries()."
      )
      y = mpimg.imread(sample_image.path)
      print(y.shape)
      yy = o3d.geometry.Image(y)
      print(yy)
      o3d.visualization.draw_geometries([yy])
  
      print("Render a channel of the previous image.")
      z = np.array(y[:, :, 1])
      print(z.shape)
      print(z.strides)
      zz = o3d.geometry.Image(z)
      print(zz)
      o3d.visualization.draw_geometries([zz])
  
      print("Write the previous image to file.")
      o3d.io.write_image("test.jpg", zz, quality=100)
  
      print("Testing basic image processing module.")
      sample_image = o3d.data.JuneauImage()
      im_raw = mpimg.imread(sample_image.path)
      im = o3d.geometry.Image(im_raw)
      im_g3 = im.filter(o3d.geometry.ImageFilterType.Gaussian3)
      im_g5 = im.filter(o3d.geometry.ImageFilterType.Gaussian5)
      im_g7 = im.filter(o3d.geometry.ImageFilterType.Gaussian7)
      im_gaussian = [im, im_g3, im_g5, im_g7]
      pyramid_levels = 4
      pyramid_with_gaussian_filter = True
      im_pyramid = im.create_pyramid(pyramid_levels, pyramid_with_gaussian_filter)
      im_dx = im.filter(o3d.geometry.ImageFilterType.Sobel3dx)
      im_dx_pyramid = o3d.geometry.Image.filter_pyramid(
          im_pyramid, o3d.geometry.ImageFilterType.Sobel3dx)
      im_dy = im.filter(o3d.geometry.ImageFilterType.Sobel3dy)
      im_dy_pyramid = o3d.geometry.Image.filter_pyramid(
          im_pyramid, o3d.geometry.ImageFilterType.Sobel3dy)
      switcher = {
          0: im_gaussian,
          1: im_pyramid,
          2: im_dx_pyramid,
          3: im_dy_pyramid,
      }
      for i in range(4):
          for j in range(pyramid_levels):
              plt.subplot(4, pyramid_levels, i * 4 + j + 1)
              plt.imshow(switcher.get(i)[j])
      plt.show()
  
apis: numpy.asarray matplotlib.pyplot.subplot matplotlib.pyplot.show numpy.array matplotlib.image.imread