Numpy change shape from (3, 512, 660, 4) to (3,2048,660,1)

问题

I am working on tensorflow and I am having some images of cars in an numpy array with shape (3, 512, 660, 4).

In this, 3 corresponds to a car index, 512*660 is an image size and 4 corresponds to the different sides of a car.

That is, (1, 512, 660, 1) corresponds to Car1 - front side image, (1, 512, 660, 2) corresponds to Car1 - Left side image and so on.

Now, I want to concat all the images of a car into one image (2048*660). That is, I want to reshape (3, 512, 660, 4) to (3, 2048, 660, 1).

Can someone help me?

I tried reshape function but it actually overlaps images rather than concatenating it.

回答1:

We could permute axes to push the last axis up front as the new third axis and reshape. Permuting axes could be handled with np.swapaxes or np.transpose or np.rollaxis, giving us three solutions, like so -

a.swapaxes(2,3).reshape(3,2048,660,1)
a.transpose(0,1,3,2).reshape(3,2048,660,1)
np.rollaxis(a,3,2).reshape(3,2048,660,1)

If you wanted to have sides-index at the front, transpose it accordingly -

a.transpose(0,3,1,2).reshape(3,2048,660,1)

来源：https://stackoverflow.com/questions/46388237/numpy-change-shape-from-3-512-660-4-to-3-2048-660-1