[FIXED] Reverse a 3d array in python

Issue

I was wondering if there is a way to reverse a 3d numpy array? Like in 1d case we can go from [1 2 3] to [3 2 1]. Is there something similar for 3d?

Thanks

Solution

Do you mean reverse it along an particular axis?

For example, if we have a color image of the size height x width x 3 where the last axis is red, green, blue (RGB) pixels, and we want to convert it to blue, green, red (BGR):

image_bgr = image[:, :, ::-1]

If you'd prefer, you can even write that as:

image_bgr = image[..., ::-1]

As a more complete example, consider this:

import numpy as np

# Some data...
x = np.arange(3 * 4 * 5).reshape(5, 4, 3)

print x[0,0,:]

# Reverse the last axis
y = x[:, :, ::-1]

print y[0,0,:]

In general, though, you can use this to reverse any particular axis. For example, you could just as easily have done:

y = x[:, ::-1, :]

To reverse the second axis.

Answered By - Joe Kington