Indexing with a list of locations

Let's use the ix_() function to shuffle the Lena image. This function creates a mesh from multiple sequences. As arguments, we give one-dimensional sequences, and the function returns a tuple of NumPy arrays. For example, check the following code snippet:

In : ix_([0,1], [2,3])
Out:
(array([[0], [1]]), array([[2, 3]]))

To index the array with a list of locations, perform the following steps:

1. Shuffle the array indices. Create a random indices array with the shuffle() function of the numpy.random module, as shown in the following lines of code. The function changes the array inplace by the way.

   def shuffle_indices(size):
      arr = np.arange(size)
      np.random.shuffle(arr)
   
      return arr

2. Now plot the shuffled indices as follows:

   plt.imshow(lena[np.ix_(xindices, yindices)])

What we get is a completely scrambled Lena, as shown in the following image:

The following code for this section is without comments. The complete code for this can be found in the ix.py file in the...