PYTHON

python einops rearrange

# credit to the example in the source link
# suppose we have a set of 32 images in "h w c" format (height-width-channel)
>>> images = [np.random.randn(30, 40, 3) for _ in range(32)]

# stack along first (batch) axis, output is a single array
>>> rearrange(images, 'b h w c -> b h w c').shape
(32, 30, 40, 3)

# concatenate images along height (vertical axis), 960 = 32 * 30
>>> rearrange(images, 'b h w c -> (b h) w c').shape
(960, 40, 3)

# concatenated images along horizontal axis, 1280 = 32 * 40
>>> rearrange(images, 'b h w c -> h (b w) c').shape
(30, 1280, 3)

# reordered axes to "b c h w" format for deep learning
>>> rearrange(images, 'b h w c -> b c h w').shape
(32, 3, 30, 40)

# flattened each image into a vector, 3600 = 30 * 40 * 3
>>> rearrange(images, 'b h w c -> b (c h w)').shape
(32, 3600)

# split each image into 4 smaller (top-left, top-right, bottom-left, bottom-right), 128 = 32 * 2 * 2
>>> rearrange(images, 'b (h1 h) (w1 w) c -> (b h1 w1) h w c', h1=2, w1=2).shape
(128, 15, 20, 3)

# space-to-depth operation
>>> rearrange(images, 'b (h h1) (w w1) c -> b h w (c h1 w1)', h1=2, w1=2).shape
(32, 15, 20, 12)