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numpymultidimensional-array3dreshape
Uylenburgh
Uylenburgh

Reputation: 1307

Reshaping numpy 3D array

I have a dataset with dimensions: (32, 32, 73257) where 32x32 are pixels of a single image.

How do I reshape it to (73257, 1024) so that every image is unrolled in a row?

So far, I did:

self.train_data = self.train_data.reshape(n_training_examples, number_of_pixels*number_of_pixels)

and it looks like I got garbage instead of normal pictures. I am assuming that reshaping was performed across wrong dimension...??

Upvotes: 1

Views: 430

Answers (1)

Jaime
Jaime

Reputation: 67427

As suggested in the comments, first get every image in a column, then transpose:

self.train_data = self.train_data.reshape(-1, n_training_examples).T

The memory layout of your array will not be changed by any of these operations, so two contiguous pixels of any image will lay 73257 bytes apart (assuming a uint8 image), which may not be the best of options if you want to process your data one image at a time. You will need to time and validate this, but creating a copy of the array may prove advantageous performance-wise:

self.train_data = self.train_data.reshape(-1, n_training_examples).T.copy()

Upvotes: 1

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