CODEWITHSUNDEEP
numpy
Ricardo Cruz
Ricardo Cruz

Reputation: 3593

numpy: unpack array along an axis

Say that I have a RGB image:

from skimage import data
img = data.astronaut()
print(img.shape)  # (512, 512, 3)

Is there a succinct numpy command to unpack it along the color channels:

R, G, B = np.unpack(img, 2)  # ?

What I am doing is using comprehension:

R, G, B = (img[:, :, i] for i in range(3))

But is there no simpler command?

Upvotes: 4

Views: 2318

Answers (3)

Conchylicultor
Conchylicultor

Reputation: 5729

Alternatively, you can use np.split:

R, G, B = np.split(img, img.shape[-1], axis=-1)

If your array is of shape (height, width, channel), you can use np.dsplit to split along the depth dimension:

R, G, B = np.dsplit(img, img.shape[-1])

Upvotes: 1

Divakar
Divakar

Reputation: 221584

Alternatively you can use np.rollaxis -

R,G,B = np.rollaxis(img,2)

Upvotes: 4

David Z
David Z

Reputation: 131600

You can transpose the length-3 dimension to the front and then unpack it:

R, G, B = img.transpose((2, 0, 1))

Upvotes: 1

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