All living within the same physical space. Elements can vary in length, depending on the number of bytes needed to represent each of them.Īn element, then, is an aggregation of bytes, which in turn are an aggregation of bits, 8 bits in particular. So, what are the elements in an array? Just bytes laid out in order.

There are ways of representing different data types in a single array, of course, but that is outside the scope of this article. Something else to note is that arrays have to contain elements of the same data-type, so as to guarantee equal byte-length intervals. A 1-dimensional array of 16-bit integers (2 bytes length) will have a stride of 2 bytes. This depends on the byte-length of the data types contained in the array.Į.g. On the memory level of arrays, the stride represents the number of bytes you need to jump forward in order to get to the next element contained in the array. That contiguous piece of memory can then be viewed in different shapes using strides. Numpy arrays, and arrays in general, are laid out in memory as contiguous chunks of bytes. What if we could just use a different view to the same chunk of memory and present it as tiles? Let’s talk a bit about arrays. import numpy as np image = np.random.randn(4, 4, 3) tiles = np.zeros((4, 2, 2, 3)) c = 0 for i in range(0, image.shape, 2): for j in range(0, image.shape, 2): tiles = image c += 1Īs the iterations grow (image size over tile size ratio), not to mention iterating over large number of images (3rd for-loop), this can occupy resources and quickly create a bottleneck in your pipeline.įig. # Creating a stack of 2 x 2 tiles out of a 4 x 4 # RGB image with channels on the last axis. However, this method is particularly inefficient (especially) in Python and does not scale well, at all, with large datasets (nor smaller tiles, for that matter).Ī nested for-loops approach would look something like the snippet below: # Nested for-loops method. One of the most common ways of creating a stack of image tiles I have seen around is with nested for-loops, as in instantiating a new array with the desired dimensions and populating it within those loops.

Split picture into grid